Introduction: To ascertain the optimal functional abductor moment arm of the hip for THA, we focused on the Trendelenburg sign. We investigate the various conditions associated with abductor moment arm to achieve a negative Trendelenburg sign postoperatively.

Methods: We reviewed 30 patients (34 uncemented primary THAs; mean age, 56 years) at a minimum of two years postoperatively. The tilting angle of the pelvis while performing the Trendelenburg test (Trendelenburg angle) was measured using a magnetic sensor system. On the hip radiographs, the %FO was calculated by dividing the femoral offset, by the distance between the centers of the bilateral femoral heads, and by multiplying by 100.

Results: The Trendelenburg angle averaged −4.3 degrees (−9 to −2.0) in all cases with a positive Trendelenburg sign, whereas it averaged +1.4 degrees (−2.0 to +12.0) when the Trendelenburg sign was negative. The %FO having a positive Trendelenburg sign (16.9 %; 10.0 to 22.5) were significantly shorter than those having a negative Trendelenburg sign (19.4 %; 13.5 to 24.7). The Trendelenburg angle correlated positively with %FO. Of the cases with a %FO value of more than 20%, about eighty percent of the cases had a negative Trendelenburg sign.

Discussion: The optimum abductor moment-arm, when the Trendelenburg sign is negative, has not been described. This study indicates that a %FO of 20 % may be one of the factors taken into account when determining the suitable size and position for acetabular and femoral neck components.

The study was designed to compare the clinical performance of an Alumina ceramic acetabular bearing to that of a polyethylene bearing in a cementless hip couple.

The study group consisted of 15 surgeons who performed 308 total hip replacements (297 patients) between January 29, 1998 and February 1, 2000. All patients received a porous coated cementless titanium stem with an Alumina ceramic 28 mm or 32 mm head. Patients were randomized to receive a porous titanium acetabular shell with either a polyethylene or Alumina cup liner. There were 164 Alumina cups and 144 polyethylene cups. The mean age was 57.3 years and consisted of 50% males and 50% females. The preoperative diagnoses were: osteoarthritis 69.8%, avascular necrosis 19.5 %, post traumatic arthritis 2.9 %, inflammatory arthritis 3.9% and other 3.9%. The mean follow up was 12 months. The longest follow up was 38 months.

The Harris Hip Score was good and excellent in 86% of the control patients and 87% of the study patients. There has been 100% follow up and survivorship.

There were two reoperations for recurrent dislocations in each group. There were no Alumina component fractures, no progressive radiolucencies and no evidence of rapid wear.

In the short term follow-up between 12 and 38 months, there do not appear to be any differences between the patients with a bearing couple consisting of Alumina on plastic with those consisting of Alumina on Alumina. There have been no catastrophic failures of the ceramic components. The Alumina/Alumina bearing couple for total hip arthroplasty appears to be an excellent alternative bearing, providing the advantage of improved long term wear and a reduced incidence of polyethylene induced osteolysis.

A method was developed to take radiographs showing the inner articulation of bipolar hip prostheses. By this method, wear was measured in 68 hips whose inner head diameter was 22 mm. Average annual wear rate was 0.17 mm. Osteolysis was observed in 25 hips (37%) and there was no difference between the annual wear rate of hips with and without osteolysis. Studying 19 retrieved prostheses, abrasion of the rim was deeper in hips with osteolysis than those without it. Wear rate of the inner articulation in bipolar hip prosthesis is much larger than that in Charnley’s prosthesis, as linear penetration into the articulation surface reduces the motion range of the inner articulation and this increases impingement and advances rim abrasion.

Friction was studied in 67 retrieved cemented cups with 32 mm internal diameter. Friction was measured under 1.0 KN of static load. High molecular hyaluronic acid was adapted as a lubricant. Thirty cups were combined with alumina heads and 37 were combined with metal heads. The years cups were in situ was 7.5 (3.2–13.2) for alumina-polyethylene implants and 8.9 (1.5–15.7) for metal-polyethylene implants (p> 0.05).

The revision rate at 15 years follow-up was higher in metal-polyethylene (PE) implants (57%) than that of alumina-PE implants (40%) (p< 0.05). The prevalence of cup loosening was less in alumina-PE implants (12/30) than in metal-PE implants (29/37) (p< 0.01). Less wear was observed in alumina-PE implants (1.15+−0,80mm) than in metal-PE implants (1.62+−0.61mm) (p< 0.01). Less wear was observed in cups without loosening (alumina-PE implants: 1.84+−0.57mm, metal-PE implants: 1.75+−0.51mm) than in those with loosening (alumina-PE implants: 0.69+−0.56mm, metal-PE implants: 1.31+−0.73mm) in both types (alumina-PE implants: p< 0.01, metal-PE implants: p< 0.05). Less wear rate was observed in cups without loosening (alumina-PE implants: 0.11+−0.05 mm/year, metal-PE implants: 0.14+−0.05mm/year) than in those with loosening (alumina-PE implants: 0.17+−0.03 mm/year, metal-PE implants: 0.22+−0.09mm/year) in both types (alumina-PE implants: p< 0.01, metal-PE implants: p< 0.05). The coefficient of friction increased in proportion to the progress of cup wear in both types (alumina-PE implants: r2 =0.217, p< 0.01, metal-PE implants: r2 =0.183, p< 0.01). Relation between the coefficient of friction and stability of implants was not detected in both types, while alumina-PE implants had lower coefficient of friction (0.137+-0.056) than metal-PE implants (0.209+−0.098) (p< 0.01). The torque of metal-PE implants without stem loosening (0.137+−0.053) was larger than that of alumina-PE implants with stem loosening (0.274+−0.088) (p< 0.01).

The results suggest that wear has greater influence on stability of implants than the friction, whereas coefficient of friction increases in worn implants.

In revision THA, the solid acetabular reconstruction in the true acetabulum is often challenging. We are using the Kerboull acetabular reinforcement devices after packing hydroxyapatite granules for acetabular bone defects. We report our 3–7 year clinical and roentgenographical results.

Twenty-one acetabuli in 20 patients were reconstructed in the true acetabuli with Kerboull-type acetabular reinforcement devices and porous hydroxyapatite granules (Sumitomo Pharmaceutical Co. Ltd.). The mean age of the patients at operation was 68 years. The mean follow-up period was 5 years and 3 months (38–88 months). Acetabular bone deficiencies were evaluated according to AAOS classification (type II: 5 hips, type III: 16 hips). Porous hydroxyapatite granules (20–60 grams) were grafted to all the acetabuli. Autologous cortico-cancellous bone grafts or hydroxyapatite blocks were used to reconstruct the segmental defects in 6 hips. All the acetabuli were reinforced with Ker-boull-type reinforcement devices and Charnley-type cemented prostheses were implanted. Clinical and roent-genographical results were evaluated using Japanese Orthopaedic Association hip score and Hodgkinson classification. Average hip score was improved from 42 points to 75 points. No re-revision was done. No infection was noted. The roentgenograms showed neither migration nor loosening of the acetabular components.

Porous hydroxyapatite granules are one of the best bone substitutes because of their mechanical and biochemical properties. Oonishi reported very good results of his acetabular reconstruction using this material. The Kerboull-type acetabular devices are very effective to the reconstruction in the true acetabulum. Excellent results of these devices were reported by Kerboull. Ace-tabular reconstrution using both of them showed very good clinical and roentgenographical results during 3 to 7 post-operative years in our series.

Aim of the study: Documentation of changes in retropa-tellar pressure, contact area and force after total knee arthroplasty in comparison with and without patella resurfacing devices.

Material and method: six cadaver specimen were examined after implantation of a total knee endoprosthesis (Genesis I type) with and without patella resurfacing implants of the sizes “small” und “medium”. Contact pressure and area measurements were done with Fuji Prescale Film (type super low) in a knee flexion angle of 60°.

Results: In comparison to the results without patella implants the implantation of the patella implant size “small” caused a significant decrease of retropatellar contact area (p=0.03) and force (p=0.03). Average and maximum pressure did not change significantly (p=0.6 and p=0.35) even though pressure increased slightly. For the „medium“ size maximum pressure (p=0.03) increased significantly and force decreased significantly (p=0,0277) whereas contact area and average pressure increased slightly.

Discussion: The significant reduction of contact area seen after implantation of both patellar implants may lead to non physiologic loading of the patella as well as to an unfavorable sliding behaviour of the femur.

Clinical relevance: Implantation of a patella resurfacing device can not significant change retropatellar pressure and the decrease of contact area is unfavorable because a small contact area can lead to accelerate wear debris and loosening. Implant size does not have a significant influence.

Aim: Evaluation of clinical, electromyographic and gait analysis results after constrained revision total knee arthroplasty. Material and Methods: 14 patients (mean age 67 years, 54-78) were evaluated 28.5 months (range, 6.5 to 61.4 months) after revision arthroplasty using constrained total knee endoprostheses (Genesis, Blauth).

Clinical evaluation was carried out using HSS, Knee Society, Tegner Activity, and Patellar scores. A three-dimensional, quantitative gait analysis and simultaneous epicutaneous electromyographic recordings of 7 muscles surrounding the knee were carried out on all patients. 11 healthy volunteers (mean age 69 years, 60-75) served as control group.

Results: Patients achieved 68 points in HSS, 125 in Knee Society, 1.3 in Tegner, and 19.1 in Patellar scores. Compared to the controls, all patients showed minor functional results. Electromyographic amplitudes of 5 muscles of the operated leg were significantly decreased compared to the contralateral side as well as the control group. Besides maximum knee extension all gait analysis parameters differed significantly between patients and controls. On the other hand, operated and uninvolved patients’ legs differed only in maximum knee extension in gait analysis. Significant correlations between clinical scores and ground reaction forces as well as electromyo-graphic levels of the gastroc muscle were noticed.

Conclusion: Functional deficits may not be explained by revision arthroplasty alone, but already exist preoperatively. The gastroc muscle seems to play and especially important role, as its functional deviations are highly correlated with clinical scores. The shown results stress the demand for extensive pre- and postoperative rehabilitation to avoid or at least reduce functional deficits after revision total knee arthroplasty.

The science of tribology concerning hip arthroplasty has mainly dealt with total endoprostheses, whereas measurement values of hemiendoprosthetic implants are rare. The small amount of experimental tribologic data concerning hemiendoprosthetic implants in the form of pendulum trials, animal experiments, in-vivo measurements on human hip joints and pin on disc studies will be reviewed in the following work. The reported frictional coefficients in these studies were between 0,014-0,07. In order to test the friction coefficients of different femur head hemiendoprostheses (ceramic-cobalt chrome – and titanium heads and bipolar endoprostheses) against fresh cadaveric acetabula, the HEPFlEx-hip simulator (Hemi-EndoProsthesis Flexion Extension) was developed. In the simulator, the various hemiendoprosthetic heads are placed on a special cone and tested against a human cadaver acetabulum cast in MCP 47 woodmetal. The plane of movement of the apparatus is uniaxial with a rotating movement of +/− 35 degrees. The force is produced pneumatically dynamic with amounts of up to 5 kN. Newborn calf serum served as a lubricant. Preliminary results showed that the mean friction coefficient at 3 kN loading was μ=0.032–0.07 for ceramic against cartilage and μ=0.024–0.153 for metal against cartilage.

Introduction: By compromising bone structure, peri-prosthetic osteolysis may increase the risk of fracture and/or aseptic loosening of components leading to revision surgery. Our purpose was to develop a reproducible rabbit model of periprosthetic osteolysis and observe the effects of implant type and fixation on the latency to onset and size of the osteolytic lesions.

Methods: Thirty-seven New Zealand White rabbits (71 knees) underwent knee arthrotomy and placement of cylindrical intramedullary stainless steel or polymethylmethacrylate (PMMA) implants. Each knee contained both a metallic and PMMA implant in either the femur or tibia that communicated with a common synovial space. A suspension of polyethylene particles (size < 4.5 um and concentration of 1-5 x 106 particles/ul) was injected into each knee at two-week intervals for ten weeks to induce osteolysis. Serial radiographs were taken at 4, 8, 14, 18, and 22 weeks postoperatively to document the progression of osteolysis. Statistical analysis was performed utilizing a two-tailed, unpaired t-test and a Mantel-Cox test with the level of significance set a p < 0.05.

Results: Radiographic analysis revealed that 96.9% of the stainless steel implants had evidence of osteolysis by 22 weeks compared to 22.9% of the PMMA implants (p< 0.001). The earliest onset of lesions in the metal implant group occurred at four weeks compared to 14 weeks in the PMMA group. We also found the area and volume of the osteolytic lesions to be significantly larger in the metal implants when compared to the implants composed of PMMA (p < 0.01).

Conclusions: Onset of osteolysis around metal implants occurred in a significantly shorter period of time and more frequently when compared to implants composed of PMMA. Also, the area and volume of the osteolytic lesions around the metal implants was found to be significantly larger than those of the PMMA. We concluded that relative material effects on osteoclast induced bone resorption and differences in ease of transport of particulate debris along metallic compared to PMMA surfaces may account for observed differences in frequency and severity of osteolytic lesions.

Patients with dislocation, severe subluxation of the hip joints were treated with cementless THA combined with subtrochanteric shortening femoral osteotomy. Total hip arthroplasty (THA) requiring subtrochanteric osteot-omy has been considered to lead to several complications. The aim of this paper is to assess the clinical results and complications of this procedure.

An acetabular component was placed into position at the site of the true acetabulum. After femoral corrective shortening osteotomy for dislocation or severe sub-luxation of the hip joints, an AML cementless stem was tightly inserted into the femoral canal to achieve bony union and osteointegration with the implant.

Twenty-one patients (23 hips; 2 men, 19 women) treated with cementless THA combined with subtro-chanteric femoral shortening osteotomy were enrolled in this study. The mean age was 55 years and the mean follow-up period was 4.5 years.

The average elongation of the limb was 48 mm after subtrochanteric shortening femoral osteotomy. Solid union of the osteotomy was obtained within an average of 5.5 months after surgery. None of these patients developed sciatic nerve palsy. There were 4 cases of non-union of the osteotomy site and 3 of aseptic loosening of the femoral component related to intraoperative femoral fracture. Upward migration of the proximal part of the femur was related to poor preoperative bone quality.

In order to diminish these complications, careful patient selection, accurate femoral reaming and suitable methods of bone cutting and augmentation of the oste-otomy site are necessary.

Introduction: We performed cementless total hip arthroplasty (THA) with autogenous bone block grafting on 18 hips in 15 patients with marked acetabular dysplasia and investigated the correlations of clinical results with the placement of the acetabular and femoral components.

Methods: There were 13 women and 2 men who had a mean duration of follow-up of 3.3 years (range, 2 to 4.3 years). According to the classification of Crowe et al, four hips in group I, three hips in group II, one hip in group III and 10 hips in group IV. The resected femoral head was used as a graft for the superior-lateral region of the true acetabulum.

Clinical results were determined according to the hip joint function criteria of the Japanese Orthopaedic Association (JOA).

Results: The mean preoperative JOA hip score was 44 points and that at follow up was 77 points. The distance from the Kohler line to the medial margin of the acetabu-lar component averaged 6.1 mm on the radiograph. Two patients required revision. In both patients, lateral insertion of the acetabular component of 8 and 15 mm respectively from the Kohler line had resulted in loosening of the cup. Of the 18 patients, femoral component had been placed in neutral position in 9, who had better clinical results than those of the others. The grafted bones united in all patients.

Discussion: The present study indicates that lateral insertion of the the acetabular component in THA should be avoided in patients with marked acetabular dysplasia.

Objective: Clinical and radiological comparison of unconstrained and constrained knee endoprostheses in revision total knee arthroplasty after septic or aseptic loosening in consideration of quality of life, activity and patella related problems.

Material and methods: 26 patients with 10 hinge pros-theses and 16 condylar prostheses were examined using the following scores: HSS, Knee Society Score, Visual Analogueue Scale, Tegner Activity Score, Patella Score, SF-36-helth questionaire. Before implantation all hinge endoprostheses were septic and all condylar endopros-theses aseptic. For radiological examination the Knee Society and Engh Score were used.

Results: There were no significant deviations in clinical parameters between the types of prostheses resp. septic or aseptic history. Radiological parameters deviated significantly in only one parameter: the femoral defects in hinge prostheses were significantly larger (p=0.0036). Regarding at patients with hinge prostheses compared with healthy subjects of the same age deviated significantly only in limitations in physical activities because of health problems, limitations in usual role activities because of physical health problems and bodily pain. In the group of condy-lar endoprostheses there were significant deviations for all items except vitality and general mental health.

Conclusion: The choice of condylar or hinged endopros-theses does not have any significant influence on clinical results, neither has aseptic or septic history. The quality of life results of condylar prostheses were inferior.

Fifty consecutive patients (60 hips) were included in the study who underwent primary total hip arthroplasty. There were 37 men and 13 women; the average age was 46.6 years (range, 26 to 70 years). The authors used cementless Duraloc series 100 acetabular component without a screw hole, a 22 mm (inner diameter) polyethylene liner, and a cementless IPS (Immediate Postoperative Stability) femoral component in all hips. The average follow-up was 6.3 years (range, 5 to 7 years). Thigh pain was evaluated using a visual analog scale (ten points). Clinical (Harris hip score) and radiographic follow-up was performed at six weeks; at three, six and 12 months; and yearly thereafter. Linear and volumetric wear were measured by software program. Bone remodeling and osteolysis were examined.

Preoperative hip score was 42.3 points (range, 16 to 69 points). The hip score at the final follow-up was 96 points (range, 95 to 100 points). All hips had satisfactory fit of the femoral stem in both coronal and sagittal planes. There was no aseptic loosening or revision of the components. One patient (2 %) had moderate thigh pain at three months and slight pain at six months and resolved. The average linear wear was 1.60 mm (SD, 0.068) and the wear rate per year was 0.23 mm (SD, 0.013). The average volumetric wear was 607.9 mm3 (SD, 25.8). The average volumetric wear per year was 87.4 mm3 (SD, 4.9). Four hips (8 %) had osteolysis in the calcar femorale (zone 7-A) less than 1 cm in diameter.

Aim of the study: The question wether there is a clinical relevance between the clinical outcome and life quality and radiological parameters.

Material and methods: 17 patients (average age 68.2 years) with total knee arthroplasty (Genesis I) were examined after a follow-up period of in average 24,6 months. The examination included the HSS-score for clinical parameters and the SF-36 for life quality. The evaluation of the radiological examinations were performed according to Ewald and Lotke and a special designed score of our unit.

Results: The HSS-Score resulted in average in 81 points and the SF-36 Fragebogens demonstrated significant worse results than in the age matched healthy population. The evaluation of the radiologic examinations according to Lotke showed an average value of 76,3. Correlations between the radilogical results and the HSS-score were not found. The correlation analysis between the SF-36 and HSS-score showed only positive values for the social functions. Correlations between the radiological evaluations according to Ewald and Lotke with the SF-36 score were found only for body pain and vitality.

Clinical relevance: This is the first study to find out the correlation between clinical and radiological parameters and also the outcome of life quality. The results of the positioning of the implants showed satisfying values in most of the cases, but some differences could be found. Because of deficits in the clinical and life quality outcome it can be supposed that the radiological parameters have significant influence. In our study we could not demonstrate correlations between the clinical and radiological examinations. Surprisingly also between the HSS and SF- 36 score no correlations were found. This findings showed us that the importance of the positioning of our implants has lower influence to the clinical results and life quality than we supposed.

Aim of the Study: Evaluation of differences in pro-prioception, gait analysis, electromyography in consideration of clinical results in patients with unicondylar and bicondylar knee arthroplasty.

Material and Methods: 17 patients with mean age of 62.5 years were examined after a mean time of 21.5 months after unicondylar knee arthroplasty and compared with 15 patients with a mean age of 67 years and a mean time of 31.9 months after bicondylar knee arthroplasty. For clinical examination the Knee Society, Hospital for Special Surgery and Patella Score were used. Proprioception was examined using the Balance test. In addition each patient was examined by gait analysis with three-dimensional-kinematics and force plate. M. rectus femoris, M. vastus medialis/lateralis, M. semiten-dinosus, M. biceps femoris, M. tibialis anterior and M. gastrocnemius were examined by electromyography.

Results: There were neither significant deviations in demographic data, clinical scores, electromyography results (except M. vastus lateralis), gait analysis nor in proprioception.

Conclusion: There were no deviations in any clinical or functional results in patients with unicondylar and bicon-dylar knee arthroplasty. Because of the uncertain long term results of unicondylar knee arthroplasty in respect of loosening and development of contralateral osteoarthritis, bicondylar knee arthroplasty can be approved.

Aim of the study: Results of total hip replacement in consideration of quality of life and their correlation to clinical radiologic findings were examined.

Material and methods: 46 of 61 patients with aseptic loosing and total hip replacement were examined in average 4,3 years after surgery with the Harris Hip Score, Merle d’Aubigne Score, Postel Score, WOMAC-Score and SF-36 Health Survey Score. The study of radiographs was completed by the Scores of Brooker, Lee and Gruen. Allograft were used in 38 (83,6%) cases.

Results: The result of the Merle d’Aubigne Score and Postel Score in average account for 11,5 points. Harris Hip Score obtains 62,7 points. The comparison form patient and control group with the SF-36-Score shows unpropitious results particularly for physical functioning, roll limitation because of physical health problems and roll limitation because of physical emotional problems. The outcome for general mental health and vitality show better results for the patients as for the control. Evaluation of the physical and psychical scale applies to impairments of daily life depending on the disease. Patients with hip arthroplasty shows in comparison to patients with cancer or cardiac infarction worst results for the physical category, whereas the best results for the psychical category. Radiographs of 33 patients were completely evaluated. In eight cases (24,2%) there were loosening lines in femur shaft area. In 18 cases (54,55%) there were loosening lines in the area of the acetabular cup, in three cases (9%) a migration

Conclusion: After a total hip replacement the physical functions are limited. Primary hip arthroplasty for young patients should be indicated reserved in consideration of above mentioned results, even if psychological results surprised.

Accepted landmarks for determining rotation include the posterior condyles, Whiteside’s line, arbitrary 3-4° of external rotation, and transepicondylar axis (TEA). All methods require anatomical identification, which may be variable.

The purpose of this study was to radiologically evaluate femoral component rotation (CT analysis) based on a method that references to the tibial axis and balanced flexion-tension.

Methods: CT scans of 38 randomly selected TKA were evaluated to determine femoral component positioning. Spiral CT scans of the femoral epicondylar region with eight 4mm cuts were performed to accurately identify medial and lateral epicondyles. Rotational alignment was measured in relation to the transepicondylar axis using CT-implemented software by two independent radiologists.

Results: Femoral component rotation ranged from 4° internal rotation to 5° external rotation with a mean of 0.0° = parallel to the TEA. All 38 cases had satisfactory clinical results, range of motion of over 90°, and showed perfect patello-femoral tracking and patellar congruency.

Conclusions: Femoral rotation position based on tibial axis and balanced flexion tension is patient specific, reproducible and results in predictable patella tracking. CT analysis in this study confirms that the tibial axis method produces a consistent femoral component positioning that relates accurately to the TEA. Tibial axis method avoids the need for arbitrary landmark identification, placing the femoral component predictably in an optimum position in relation to the tibia and patella.

The purpose this prospective, randomized clinical trial was to determine if unilateral or bilateral simultaneous total hip arthroplasty procedures resulted in a differing incidence of fat embolization, degree of hemodynamic compromise, levels of hypoxemia or mental status changes. Also, the incidence of fat embolization was compared between the cemented and cementless total hip arthroplasty in the patients with a unilateral- and bilateral simultaneous total hip arthroplasty.

One hundred and fifty-six consecutive patients undergoing primary total hip arthroplasty were enrolled prospectively in the study after giving informed consent. The group consisted of fifty patients undergoing bilateral simultaneous total hip arthroplasty and 106 patients undergoing unilateral total hip arthroplasty. One hundred and three hips were cemented and 103 hips were cementless. To determine the hemodynamic changes and to detect the fat and bone marrow embolization, arterial and right atrial blood samples were obtained before implantation (baseline) and at one, three, five and ten minutes after implantation of the acetabular component. Also, arterial and right atrial blood samples were obtained at one, three, five and ten minutes after implantation of the femoral component. And then blood samples were obtained at twenty-four and forty-eight hours after the operation. Arterial blood pressure, right atrial pressure, arterial oxygen tension and carbon-dioxide tension were monitored at corresponding times. The presence of lipid was determined with oil red O fat stain and the presence of cellular contents of bone marrow was determined with Wright-Giemsa stain.

The incidence of fat embolism was not statistically different (P=1.000) between the patients with a bilateral total hip arthroplasty (twenty seven patients or 54 per cent) and the patients with a unilateral total hip arthroplasty (fifty-two patients or 49 per cent). In the semiquantitative analysis of fat globules in both groups, there was no tendency to have a higher number of fat globules in the bilateral group than in the unilateral group. Also, the incidence of bone marrow embolization was not statistically different (P=0.800) between the patients with a bilateral total hip arthroplasty (eight patients or 16 per cent) and the patients with a unilateral total hip arthroplasty (fourteen patients or 13 per cent). There was no statistical difference (P=0.800) in the incidence of the presence of fat globule between the cemented total hip (thirty-four patients or 34 per cent) and the cementless total hip arthroplasty (forty-seven patients or 44 per cent). Also, there was no statistical difference (P=0.627) in the incidence of the presence of bone marrow cells between the cemented total hip arthroplasty (thirteen patients or 13 per cent) and the cement-less total hip arthroplasty (twelve patients or 11 per cent). Four patients with positive bone marrow cells had neurological manifestation. All of these four patients developed diffuse encephalopathy with confusion and agitation for about twenty-four hours.

The present study confirmed that the incidence of fat and bone marrow embolization is similar in the patients with a bilateral simultaneous-and unilateral total hip arthroplasty as well as in the patients with cemented and cementless total hip arthroplasty. The patients with bone marrow cell emboli had a significantly lower arterial oxygen tension (p=0.022) and oxygen saturation (p=0.017) than the patients without bone marrow cell emboli. On the contrary, the number of fat globules did not affect the perioperative hemodynamic changes. Encephalopathy is related to the biochemical and/or mechanical changes by bone marrow cells.

The purpose of this study was to analyse and to recommend solutions for early complications with a new total knee mobile bearing device, that promises a logical synthesis of combined A/P translation and rotation ability, but has shown early surgical technique related complications.

Materials and Methods: There were 244 Low Contact Stress (LCS) A/P glide total knee replacements (TKA) performed in the time between 1995 and 1999. Mean age was 67.2 years (range: 53-83). Mean follow-up was 16.5 months (range: 1-51). There was an unusual high incidence of anterior knee pain in this group compared with excellent results utilising rotating platform LCS TKA in this centre. Diagnostic evaluation included radiographs, arthroscopical evaluation, and positron emission tomography in five selected cases.

Results: There were 11 (4.5%) cases with Hoffa fatpad impingement, progressive ligament instability in 5 (2.0%) cases, arthrofibrosis in 4 (1.6%) cases, one malposition of tibial component, and one proximal tibial AVN. Five PET 18F-FDG scans prior to revision surgery revealed increased up-take correlated with intraoperative findings of fatpad fibrosis and/or necrosis.

Conclusion: The LCS A/P glide mobile bearing TKA has theoretical advantages over both meniscal and rotating mobile bearing knee designs. Early occurrence of Hoffa fatpad impingement was caused by surgical mal-technique in this centre that usually retains the vast majority of the fat pad. Revision surgery revealed evidence of impingement and all cases revealed clinical improved after partial excision of the fatpad. We, therefore, recommend partial to total excision of the Hoffa fat pad for utilisation of the A/P glide prosthesis.

The purpose of this study was to analyse a potential correlation of arthrofibrosis (AF) and femoral rotational mal-alignment in total knee arthroplasty (TKA). We hypothesized an increased internal mal-rotation of the femoral component leading to unphysiological kinematic motion of the arthroplastic knee joint. These repetitive microtrauma may then induce increased synovial hyperplasia leading to arthrofibrosis. Arthrofibrosis is an ill-defined entity that results in unsatisfactory outcome following TKA. Biological and mechanical factors have been suggested as etiology, but specific causes have not been identified.

Methods: From a cohort of 3058 mobile bearing TKA 44 (1.4%) cases were diagnosed with arthrofibrosis, of which 38 (86%) cases underwent clinical examination and CT investigation to determine femoral component rotation taking the transepicondylar (TEA) axis as reference point. A control group with 38 well functioning TKA was compared.

Results: Increased internal mal-rotation of the femoral component of 5.0° in the AF group (reference to the TEA) was highly significant (p < 0.001) ranging from 10°IR to 1°ER compared with the control group (0.0° parallel to TEA, 4°IR to 5°ER). Men younger than average for index TKA in this center with a decreased BMI, previous knee surgery (particularly correcting osteoto-mies), poliomyelitis, and OA had an increased risk of developing arthrofibrosis. PCL retaining or sacrificing, patella resurfacing or retaining had no increased prevalence for AF. Rheumatoid patients had a decreased risk of developing arthrofibrosis .

Conclusion: The correlation of AF to femoral component internal mal-rotation was statistically significant (p < 0.001). These results confirm that unphysiological kinematics in TKA appear to be a major etiopathological factor for arthrofibrosis (AF). In this study femoral component internal mal-rotation has shown to be a significant risk factor in the development of arthrofibrosis. We, therefore, recommend consideration of early CT evaluation in cases with AF and, when internally mal-rotated, revision of the femoral component.

This study has been cleared by the Ethical Committee, University of Zurich, Switzerland.

Introduction: Pelvic and acetabular reconstruction following tumor resections are often difficult and fraught with complications. This is the first report of a reconstruction utilizing sacral implantation of an acetabular component, a relatively simple procedure.

Materials and Methods: A 74 year-old man developed recurrent low-grade chondrosarcoma in his ilium. Prior resections had included total hip reconstruction with massive cemented acetabular components. A combined Type I and II internal hemipelvectomy with endoprosthetic reconstruction were performed. Following resection, his sacrum and a small fragment of remaining ilium at the sacroiliac joint was reamed to accept a 48 mm porous coated acetabular component. It was press- fit into place and further secured with two central and three rim screws. A constrained cup liner was used. A proximal femoral endoprosthesis was constructed from a commercially available modular oncology system. Additional resection of the superior and inferior pubic ramie was required to minimize the likelihood of endoprosthetic impingement and leverage-induced dislocation. A soft tissue reconstruction of the abductors was accomplished.

Results: He remains free of recurrence 15 months post-operative. He ambulates full weight bearing with crutches. His leg is neurovascularly intact and he is pleased with his results. A videotape, demonstrating his gait, will be shown

Discussion: The author knows of one similar reconstruction that was performed at another center (unpublished data). That other patient suffered acetabular component dislodgement. The intraoperative leverage-induced dislocation of the hip was the important determination. Pubic rami resection may be required to prevent femoral impingement and instability. The use of multiple fixation screws also improved component fixation.

Conclusion: Placement of a well fixed, constrained, acetab-ular component into a retained sacrum at the level of the SI joint provides an alternative limb salvage technique.

Cementless fixation in TKA remains controversial because of less predictable osseointegration and difficulty interpreting fixation interfaces. Radiolucent zone analysis (RLZ) of plain radiographs is the only practical method of evaluating the fixation interface.

Methods: This study evaluated 567 consecutive primary LCS mobile-bearing TKA with in-depth RLZ analysis of all cases by one author (T.K.). Mean follow-up was 5.7 years (2.0-14.9), mean age 69 years (70% females). Diagnosis included 8.3% rheumatoids. The same porocoated femoral and patella components were utilized. Tibial components included a 3-fin (ACL/PCL-retaining) or tapered-cone design (PCL-retaining/substituting). Bone treatment included generous use of autograft: cortico-cancellous struts for slope-off deformities and soft bone, morselized impaction for central zones, slurry to achieve interference fit.

Results: Good/excellent results were 94.7% with 4 fixation failures. Sequential RLZ of six patellar, four femoral, six tibial zones revealed: 1). Minimal femoral/patella lucencies---no failures; 2) Tibial tapered cone (n = 523) had one (0.2%) failure. Lucencies of 1–2 mm (usually isolated) were noted in 2% medial, lateral, posterior and 4% anterior/central zones, all of which remained stable; 3).Tibial 3-fin tibial design (n = 44) had 3 failures (6.8%) with RLZ > 2mm in multiple zones.

Conclusion: Cementless fixation with LCS porocoat pros-thesis was successful in all femoral/patellar and 99% of the tibial-cone design. The 3-fin design had multiple RLZ and a higher failure rate (not recommended). RLZ analysis with plain X-rays (over time) is a practical method of evaluating cementless fixation and correlates with clinical outcomes in our study.

Correction of fixed valgus is a challenge in primary TKA. Achieving patello-femoral and femoral-tibial stability requires superficial/deep lateral side releases if non-constrained prostheses are utilized. The medial approach has disadvantages with more reported complications. The direct lateral approach, with/without tubercle osteotomy, is an approach option utilized in two reporting centers.

Methods: 255 valgus TKAs with 5- to15-year follow-up were reviewed. Demographics included 91% females, 15% rheumatoid, mean age 69. Prostheses utilized were LCS mobile-bearing (meniscal PCL-retaining/rotating PCL-sacrificing). Patella was non-resurfaced in 90%; cementless fixation in 86%. The direct lateral approach with similar lengthening techniques was used with tubercle osteotomy in one center and osteo-periosteal joint exposure in another.

Results: Good/excellent 91%, modified HSS score improvement 57 to 85. Deformity (12) improved < 8 to 12 points (> 15o valgus to < 5o valgus). ROM improved from mean 11o/97o to 1/110o latest. Technical/prosthetic-related complications included: 7 bearing failures (5 meniscal, 2 rotating platform), 2 aseptic loosenings (tibial), 1 patella ligament rupture and 2 screw loosenings in the osteotomy group, 1 patella re-dislocation in a 75-year-old female with dislocation since age 15 (non-osteotomy group), 2 infections, and 1 re-operation for arthrofibrosis .

Discussion/Conclusion: Valgus TKA using LCS move-able bearings implanted via a direct lateral approach are highly successful regarding stability and patella tracking. Failures correlate with inadequate/de-stabilizing releases and meniscal PCL-retaining prostheses. Rotating bearings allow for better stability and self-adjustment of common mal-rotation variables. The lateral approach allows for direct (step-wise) lengthening releases, improved patellar tracking, and precise gap balancing.

We have developed lameller etched titanium (L.E.T.) structure, as a new bone-prosthesis interface. L.E.T. has a laminating structure consisting of a thin board made of porous etched titanium layer. We call this structure, a space controlled interface, because its pore shape, pore size and porosity within the interface can be controlled easily.

Purpose: We compared the binding capacity of L.E.T. system with the conventional beads surface, by experimental study.

Materials and Methods: We implanted two types of interface in 30 canine femora, one with LET and, the other with a conventional beads surface structure as a control. Hydroxyapatite (HA) is coated on L.E.T. stem. The dogs were killed three, six, ten weeks later. The harvested femora were cut off seven sections follow by a push out strength test and calculate the rate of bone ingrowth by measuring images of backscattered electron imaging-scanning electron microscopy (BEI-SEM) of each cross section using the NIH Image. Thin-sectioned tissues were then stained with toluidine blue.

Results: The push-out strength of the L.E.T. stems were 146 to 384% greater and its rate of bone ingrowth were 193 to 226% greater than that of the conventional beads stems. HA coated L.E.T. implants had the new bone formation down to the bottom of the porous portion even after three weeks, the findings which was not seen in the conventional beads stems in microscopic and BEI-SEM finding.

Discussion and Conclusion: Space controlled interface (L.E.T.) was proven to keep an adequate pore within the interface and induce true bone ingrowth in the space. Using L.E.T. structure, faster bone ingrowth and stronger fixation of the stem to the bone can be obtained.

Although bone loss and ligamentous instability are usually indications for the use of constraining prostheses in revision total knee arthroplasty (TKA), several reports have documented a high rate of failure with these prostheses. We therefore tried using the cruciate retaining augmentable type prosthesis (NexGen CRA) if a good intraoperative ligamentous balance could be obtained with revision TKA.

CRA was used on nine knees of seven patients with an average age of 71.7 years. The follow-up lasted for an average of 1.6 years. Clinical evaluation consisted of instability ratings, knee score, range of motion and %MA (mechanical axis) as an index of the alignment. These patients showed improvement varus instability from a mean of 7.0° preoperatively to a mean of 1.5° postoperatively, and in valgus instability from 5.3° to 1.3°.

The knee score was significantly improved from 41 to 81, but the %MA resulted in an unsatisfactory improvement from −8.8% to 34.0%. The femoral anatomical-mechanical angle (FAMA) was measured as a parameter of bowing deformity of the femur, and the knees were divided into two groups, the bowing group consisting of the knees with an FMA of more than 8° (n=6, average 9.0°), the normal group of knees with an FAMA of less than 7° in FAMA (n=3, average 6.7°). The postoperative %MA showed a mean value of 40.9% for the normal group, and 30.6% in the bowing group. These results demonstrated that the discrepancy between FAMA for the bowing group(=9.0°) and the valgus angle of the stem of the femoral component (6.0°) was the cause of the malalignment in the bowing group. These clinical results suggest that the cruciate retaining augmentable type prosthesis can be used successfully for selected revision cases, but that malalignment in knees with bowed femora may remain a problem.

A changed kinematic elbow axis can cause early loosening of elbow endoprostheses and can decrease the functional outcome. Therefore, these prostheses and their alignment tools are designed to reconstruct normal joint kinematics. We investigated whether it is possible to reconstruct the pre-operative kinematic axis of the elbow when an iBP^™ elbow endoprosthesis (Biomet) has been placed.

The calibrated Flock of Birds® electromagnetic tracking device registered controlled passive elbow flexion of ten embalmed upper extremities. The pre-operative kinematic elbow axes were established using helical axes.

Results were expressed in the humeral coordinate system defined by the glenohumeral joint rotation centre and the lateral and medial epicondyle of the humerus. The glenohumeral joint rotation centre was determined using a regression method. The senior author implanted the iBP^™ elbow endoprosthesis using standard instrumentation for humeral component alignment. The post-operative kinematic axes were then calculated. A Student’s t-test was performed to compare the pre- and post-operative axes.

No significant differences were found in the direction of the kinematic elbow axes before and after surgery, indicating no alteration in the valgus/varus angle or change in longitudinal rotation of the ulna with respect to the humerus. However, the axis was located significantly more distal (mean difference 7.0 mm, p = 0.004) after surgery. The ventral-dorsal location of the kinematic axis was not significantly different (p = 0.748) after surgery, but there was some variation in individual axes. The iBP^™ Elbow System enables the reconstruction of the direction of the pre-operative kinematic elbow axis. While the exact position of the pre-operative axis could not be reproduced in vitro, the kinematic axis of the elbow is expected to be less distal in vivo as a result of the extensive destruction of the rheumatoid elbow. Individually adjustable alignment tools might enable more precise reconstruction.

We evaluated the geometry of the resected femoral surface according to the theory for total knee arthroplasty (TKA) using three-dimensional computed tomography (3D CT).

The 3D CT scans were performed in 44 knees indicated as requiring total knee arthroplasty. The 3D images of the femurs were clipped according to the following procedures. The distal femur was cut perpendicular to the mechanical axis at 10 mm proximal from the medial condyle. Rotational alignment was fixed at 3 degrees external rotation from the posterior condylar line. The anterior condyle was resected using the anterior cortex as the reference point. The posterior condyle was cut at 10 mm anterior from the medial posterior condyle.

The medial-lateral (ML) width/anterior-posterior (AP) length was 1.58 ± 0.14 (mean ± SD). AP length of the 3D images tended to be longer than the box length of the three kinds of components provided when the ML width of the images was approximately equal to that of each component. The widths of medial and lateral posterior condyles of the images were 30.1 ± 3.8 mm and 24.8 ± 3.0 mm, respectively. In all except one case, the widths of the resected medial posterior condyles were greater than those of the medial condyles of all components when those of resected lateral posterior condyles were equal to those of the lateral condyles of the components.

The shapes of the resected femoral surface did not always match those of the components. The configuration of Japanese knee joints is different from that of American knee joints. Components with appropriate geometry should be designed for Japanese patients.

In cementless fixation system, surface character becomes important factor. Alkali and heat treatments on titanium metal has been proved to show strong bonding to bone and higher ongrowth rate. In this study we examined the effect of alkali and heat treatments on titanium rod in rabbit femur intramedurally model, in consideration of cementless hip stem. The implant had a 5mm in diameter and 25 mm in length. The implants were and half of them were immersed in 5 mol/L sodium hydroxide solution and heated at 600 åé for one hour (AH implant), and the other half were untreated (CL implant). The implants were implanted into the distal femur of the rabbits, AH implant into left femur and CL implants into right. The bone-implant interfaces were evaluated at 3, 6, and 12 weeks after implantations.

Pull-out tests showed that AH implants significantly higher bonding strength to bone than CL implants at each week after operations. At 12 weeks mean pull-out load of AH implants was 411.7 N and that of CL implants 72.2 N. As postoperative time elapsed, histological examination revealed that new bone form on the surface of the both types of the implants, but significantly more bone contacted directly on the surface of AH implants. At 12 weeks AH implant was covered by the newly formed bone about 56% of the whole surface of the implants and CL implants was about 19%.

In conclusion, alkali- and heat-treated titanium offers strong bone-bonding and high affinity to bone instead of conventional mechanical interlocking mechanism. Alkali and heat treatments on titanium may be applicable to the surface treatment for cementless joint replacement implant.

Introduction: This study evaluated the sphericity of bearing surfaces in total hip arthroplasty.

Methods: All the prosthetic metal femoral heads and the UHMWPE liners evaluated in this study were obtained straight from manufacturers (DePuy Johnson and Johnson, Howmedica Osteonics, Kyocera, Smith and Nephew, Zimmer). Out-of-roundness was assessed as an indicator representing sphericity. A total of 50 femoral heads and 22 UHMWPE liners were evaluated in 1995. Out-of-roundness of ball bearings were measured for the control study. A total of 43 femoral heads and 40 UHMWPE liners were evaluated in 1999 and 2000.

Results: The out-of-roundness of the femoral heads and the UHMWPE liners were significantly inferior to those of ball bearings. The out-of-roundness of the UHMWPE liners was significantly inferior to that of the femoral heads. The out-of-roundness of the femoral head on the sagittal plane was significantly inferior to that on the transverse plane. Several significant differences were found among different manufacturers. Overall, the out-of-roundness of the femoral head on the sagittal plane and UHMWPE liners had improved significantly in 1999/2000 compared to that in 1995.

Discussion: We previously reported that UHMWPE wear in poor out-of-roundness coupling (femoral head: 9.5 μm, socket: 36 μm) was 148% greater compared to those in good out-of-roundness coupling (femoral head: 0.5 μm, socket: 0.6 μm) at 1 million cycle experiments (J Arthroplasty 15:332, 2000). Some prosthetic femoral heads indicated more than 9.5 μm out-of-roundness in the present study, and these femoral heads with poor sphericity might be unfavorable to wear if implanted. We consider that sphericity of UHMWPE liners should be also improved to reduce initial UHMWPE wear. The sphericity of bearing surfaces can be improved by appropriate changes in manufacturing technique. Further improvement is desirable, since this is expected to prolong the functional performance of the prosthesis after total hip arthroplasty.

We developed an endoscopically controlled device for cement removal out of the femoral canal. This system (Swiss OrthoClast) uses simple ballistic principles to effect mechanical fracturing of the bone cement. A special extraction set facilitates removal of the distal cement layer and of the intramedullary plug. The cement removal procedure, even in the depth of the femur, is controlled with an endoscopical system via monitor. Handling of this device will be demonstrated. We report our clinical results of 45 procedures with this device.

Material and methods: 45 patients (14 male ,31 female, average age at revision 72.9 years) were revised after an average follow-up period of 91.2 months (range 0-252 months) after primary THR due to mechanical loosening (n=38) or infection (n=7). All procedures were analysed and evaluated with a standardized documentation.

Results: 90% of the revisions showed type 1 bone defects according to Paprosky’s classification. In all but three cases cement removal with this method was complete. We saw one case of femoral fissuration in a patient with osteoporosis and one cortical perforation while drilling in the K-wire of the extraction tool. The time for cement removal varied between 5 and 75 minutes with an average of 27.1 minutes in the aseptical and 36.9 minutes in the septical group. Only in the very first cases we had problems with the endoscopic view.

Conclusion: Swiss OrthoClast facilitate cement removal out of the femur and avoids cortical fenestration. The optical system is effective and helpful, even for extraction of the distal cement layer and the medullary plug. This mechanical system has no side effects like development of heat, dust or toxic products during cement removal. Disadvantages might be the learning curve for the surgeon and its costs.

Purpose: Using the finite element analysis, the authors analyze the effect of the articulating material properties of the total hip arthroplasty to stress and micro-motion of the proximal femur and the femoral stem.

Material and methods: The head (28mm) and the acetabular component (outer diameter = 54mm, liner thickness = 11.4mm) were considered as ceramic on ceramic, cramic on polyethylene, metal on metal, metal on polyethylene and metal on metal-polyethylene. The femur was modeled with different friction coefficients according to the different contact portion of the femoral stem, which was modeled after Omni fit HA #9(Osteonics, Allendale, NJ). Non-linear contact analysis was proceeded in human with body weight 70Kg at one leg standing and stair climbing.

Result: The maximal yield strength was always higher in hard-hard coupling. In one leg standing, the site of maximal yield strength was represented at the contact point of articulation. In stair climbing, the site of maximal yield strength was represented at the same site in hand on hard coupling but at the lateral aspect of the neck in hard-soft couplings. There were no changes in the patterns of stress distribution but the micro-motions were up to the limit of bone in growth in hard-hard coouplings.

Conclusion: The maximal yield strength and the micro-motions revealed different values according to the articulating materials. These findings were considered valuable information to postoperative management and longavity of the total hip prosthesis but requiring the following experimental and clinical study.

Patellofemoral complications after TKA are mostly avoided with appropriate operative technique. Although most orthopedic surgeons performed using a medial parapatellar approach at TKA, but a large amount of the patellar blood flow is blocked by this procedure. A certain surgical exposure, including the midvastus and subvastus approach, has resulted in good clinical results. It is important to maintain the integrity of the extensor mechanism. But the southern or subvastus approach has inadequate exposure in some patients. And then we have had the primary total knee Arthroplasty using midvastus approach in 98 cases, 68 patients. Mean follow up is 30 months, between from 20 months to 43 months.

We estimated parameters of total blood loss, surgical time, difficulty of exposure, number of lateral releases. The clinical parameters of range of motion, ability to perform a straight leg raise, and the number of operative or postoperative complications were evaluated. The patients who had the midvastus approach had minor blood loss, resonable surgical time, no difficulty of exposure even in patients with severe varus or valgus deformities, required lateral retinacular releases only 5% of the cases. The range of motion was all above 120 degrees flexion, no extension loss, had a higher incidence of ability to straight leg raise and fewer complications as like superficial wound infection. The midvastus surgical approach have some more advantages with less pain and earlier control of the operative leg, and may be discharged from the hospital earlier. Because preserving the integrity of the vastus medialis insertion into the medial border of the quadriceps tendon and limited disruption of the extensor mechanism improves the rapid control of quadriceps muscle and improves the more stable patellofemoral articulation, and then evidenced a marked reduction in the need for lateral retinacular releases.

We recommend the mid-vastus surgical approach for total knee arthroplasty. The Midvastus approach is an efficacious alternative to the medial parapatellar approach for primary total knee arthroplasties in selected patients who are not obese and who have not had previous arthrotomy. And if needed more additional exposure, the muscle can be safely split by further dissection.

Introduction: Osteolysis is a silent disease with few clinical symptoms until significant bone loss has occurred. Advanced osteolysis, with associated bone loss, can make revision surgery more difficult and compromise the ultimate outcome. In order to delineate the natural history of screw osteolysis in the AMK (Anatomic Modular Knee, Depuy) TKA, a cohort of patient were followed prospectively to determine the incidence and progression of osteolysis.

Methods: Between October 1987 and November 1992, 370 patients had 450 uncemented AMK TKA performed at a single institution. Attempts were made to contact all patients in 1993 and 228 patients (280 TKA) agreed to participate in the study. Flouroscopically guided tangential views of the tibial tray were performed and any osteolysis was catalogued by location and graded based on the classification of Lewis et al. Eighty-seven knees had osteolysis for an incidence of 31%, with 52 line, 23 cyst, and 12 cavity. The patients with osteolysis were reassessed 3 years later. No progression was noted in patients with line osteolysis, but two patients with cyst and two patients with cavity had progressive osteolysis. Five knees had been revised for symptomatic osteolysis.

This cohort was reassessed by chart and radiograph review in 2000. All patients who initially had cavitary osteolysis had been revised. In addition, 13 patients with cyst osteolysis progressed to cavity and ten knees had been revised. Of the 52 knees that had line osteolysis, 21 progressed to cyst or cavity and 15 knees were revised. Furthermore, 57 additional knees had developed osteolysis with 24 knees being revised.

Osteolysis in the AMK is a silent and progressive disorder. We were unable to identify any risk factors that would classify certain patients as at risk for osteolysis. Consequently, we recommend regular periodic follow up in order to recognize osteolysis early.

As for the number of patients who requires total knee arthroplasty (TKA), Asian-Pacific countries will be the most important market. However, due to the paucity of anthropometric data on the proximal tibia in this population, many prostheses designed for Caucasian knees have been introduced without specific modification.The aim of the current study was to analyze the geometry of the proximal tibia to design the optimum component for the Japanese population.

Anthropometric data on the proximal tibia of 100 knees in 80 patients undergoing TKA was obtained. Briefly, anterior-posterior (AP) and medial-lateral (ML) lengths were measured with a combination of two different methods, namely on the computed tomography (CT) images obtained preoperatively and intraoperative direct measurement on tibial resection surface. Reproducible measurement was possible only when the intraoperative measurement was combined with the corresponding CT images while the direction of measurements being aligned to the epicondylar axis of the femur.

It was shown that smaller components with an ML of around 60 mm were rarely required. Tibial component size variation should focus on an ML length of 65 to 75 mm because 76 of 100 knees (76 %) fell into this size range. When the subjects were confined to women, 70 of 77 knees (91%) were included in this size range. The intraoperative AP to ML ratio had a negative correlation with the ML length (r = −0.412, P < 0.0001) indicating that bigger knees were shallower in the AP direction. The size variation of currently popular pros-theses were not in accordance with the geometry of the tibial resection surface shown in this study.

The results of this study applied to a cross-section of the Japanese population can be used by manufacturers to create a prosthesis suitable for most of the Asian-Pacific population.

BIONs (Bionic Neurons) are microminiature stimulators that can be injected into muscles. They receive power and commands from an external magnetic field. They have been shown to be safe and effective for stimulating muscles in animals. Clinical trials are underway to assess the efficacy and safety of BIONs for therapeutic exercise of weak or paralyzed muscles. In patients with knee osteoarthritis weakness of quadriceps muscle has been shown by different authors to be highly correlated with pain and functional impairment, while quadriceps strengthening is associated with significant improvements of clinical scores. Preliminary results of the use of BIONs to strengthen the quadriceps muscles in patients affected by knee osteoarthritis are reported.

Five patients have been recruited so far, three of them have completed the protocol. Patients are implanted with BIONs near the common femoral nerve and in the vastus medialis muscle, and stimulated for 12 weeks. Therapy starts three days after implantation with two-three stimulation sessions of 10–30 minutes each day. Stimulation parameters are intended to recruit the quadriceps muscles (up to 10 X threshold for muscle twitch) at relatively low frequencies (5–13 pps) in short trains (5–10 s) with pauses between trains (5 s). Outcome measures include WOMAC, Knee Society Score, muscle measurements with MRI, gait analysis, isokinetic tests. All patients found muscle stimulation to be agreeable. No adverse events or complications have been observed. Thresholds for eliciting muscle contractions remained stable over time. In the three patients knee function improved and pain decreased over the stimulation period, while muscle thickness, as measured by MRI, increased.

Results are preliminary but encouraging. We anticipate studying 15 patients to demonstrate clearly the safety and efficacy of this technology in this application. Plans are underway for additional clinical trials in orthopaedic patients as well as in stroke patients.

A modular neck allows to choose the offset of the femoral head and the degree of anti-retroversion, lateralization and varus-valgus intraoperatively. At the G. Pini Institute we have been using modular necks in custom prostheses since 1989. Excellent results in this application did open the way to a larger use in off-the-shelf prostheses. Modular necks can be now coupled with different stems, leaving the surgeon free to use the preferred prosthetic stem design. Modular necks have been implanted in more than 50,000 in the world. Medium term results in custom prosthesis and the experience in off-the-shelf non-cemented stems are presented, together with further improvements of this technology under study.

From 1989 to December 1999, 481 custom stems have been implanted. All patients but ten received modular necks. The prostheses were made of a titanium alloy and HA coated. 61 % of patients had dysplastic oxarthrosis. 372 implants performed between 1989 and 1996 were retrospectively evaluated. Data from off-the-shelf prosthesis, at a shorter follow-up, are also reported. Laboratory data showed that the use of an elliptical Morse cone of the neck reduced wear debris production to less than 1 mg/year. In custom implants, (mean follow-up: 7 years), we did not observe any thigh pain or radiological signs of osteolysis or fretting. Mean leg-length discrepancy was 2.8 cm pre-op and 0.3 cm post-operatively. Off-the-shelf implants also showed good clinical and radiological results. New design modular necks will increase the possible range of motion and provide more solutions for positioning the center of rotation. Modular neck is a safe and reliable solution to obtain the correct position of the center of rotation intra-operatively, without side effects. Applications in off-the-shelf prostheses allow to reduce costs while maintaining the advantages of this technology.

The success of total knee replacement surgery depends critically on proper limb alignment and implant position. Even with contemporary mechanical alignment instrumentation, errors in limb alignment and implant position do occur. To improve upon the accuracy and biomechanical efficacy of conventional surgical instrumentation while limiting the need for substantial pre-operative planning, a non-image-based computer-aided navigation system was developed for total knee replacement surgery. Clinical studies have demonstrated that use of this system, OrthoPilot® (Aesculap AG, Tuttlingen, Germany), for knee replacement surgery can lead to improved limb alignment and implant position.

In this study we investigated the repeatability and sensitivity of the OrthoPilot® computer-aided navigation system for total knee replacement surgery. To assess repeatability, total knee replacement surgeries were simulated on an idealized test bench using identical input parameters and the variation in output measurements was measured. To assess sensitivity, the effect of moderate movement of position sensors on system-level accuracy was measured. The results indicate that (1) the system functions in a highly repeatable manner if it is supplied with repeatable inputs; and (2) unintentional relative movement of position sensors during surgery can substantially affect accuracy of the system outputs.

Because computer-aided navigation systems are powerful tools for orthopaedic surgery, it is important to recognize that their accuracy and precision are highly dependent on pre-operative and intra-operative registration techniques. Like all instrumentation systems, their use is associated with a learning curve, even in the hands of experienced orthopaedic surgeons. The results of this study demonstrate that the OrthoPilot® in an inherently precise instrument that is sensitive to variations in surgical technique. It is critical that the users of these systems (i.e. surgeons) be aware of system sensitivities and pay careful attention to operative techniques required by the system.

Introduction: The majority of total knee systems available on the market were designed to accommodate limited flexion up to 130 degrees only, which does not satisfy many patients. The LPS Flex was designed to accommodate deep flexion safely (up to 160 degree of flexion). This is the first paper to report the clinical results of 108 TKA using the LPS flex system.

Material and methods: 108 surgeries were preformed on 86 patients from September 1999 to March 2001. All patients were treated for advanced degenerative arthritis. All surgeries were done by one surgeon. The Subvastus approach was used in all cases. Pre-op and post-op ranges of motion were documented. Patients who had over 145 degree of flexion and were able to sit on the ground (calf touching thigh) for at least one minute were considered to have full flexion. Statistical analyses were carried out on the data at University of Dundee.

Results: Full range of motion was obtained in 76 TKA. All these cases had a full movement preoperatively range of motion except for 5 cases. Complication rate were similar to those reported in other series. There were no complications that could be attributed to the ability to fully flex the knee. Full flexion was found to be the same in patients who had simultaneous bilateral total knee and those who had it on only one side.

Conclusion: LPS flex knee design offers a good option for patients who have good preoperative range of motion. The ability to fully flex the knee is important in certain cultures and in active patients of the western society. Our preliminary results show that there was no risk associated with deep flexion.

Loosening of the glenoid component after Total Shoulder Arthroplasty is an established phenomenon with long-term follow-up studies showing radiolucency in 65% of glenoid components at 10 years (Stewart and Gray, 1997). Glenoid component designs are based on anthropometric measurements of normal shoulder joints. The purpose of this study was to study the surface anatomy of both bony and cartilaginous layers of the normal glenoid fossa in more detail.

We have developed a reproducible and inexpensive technique of surface shape assessment using laser morphometric analysis and applied this to thirty normal glenoid fossae mounted in the scapular plane. Surface analysis was carried out before and after removal of the glenoid labrum and after papain digestion of the articular cartilage allowing assessment of the skeleton alone allowing comparison with other studies using bony or cartilaginous landmarks in assessment of glenoid version. Using a specially designed program, five equi-distant lines were placed across the glenoid from which analysis of the orientation of the fossa was determined.

None of the scapulae presented a single surface that could be judged anteverted or retroverted by an amount representable by a single figure. All scapulae demonstrated a twist about the vertical axis. Two main types were identified.

Type 1 – Superior retroversion (mean 16.0 degrees) becoming progressively less to the lower pole (mean 3.0 degrees)

Type 2 – Retroverted superiorly, twisting to reach the position of maximal anteversion in the lower half of the glenoid, twisting back into more retroversion towards the lower pole. None of the specimens were morphologically equivalent to currently available glenoid prostheses. The surface shape of the glenoid is so variable that we should explore the relationship between this and the kinematics of the shoulder joint. There may be implications for the design of shoulder replacements and possibly custom prostheses.

Introduction: Filling bone defects with Polymethylmetaacrylate (PMMA) has been a easy, safe and reliable technique for past four decade. Newly developed Calcium Phosphate Paste (CPP) is a mixture of alpfa Tri Calcium Phsphate (TCP), Tetra Calcium Phosphate, Calcium Hydrogen Phosphate and Hydroxyapatite. This paste hardens in 10 minutes and its stffness increases to 80Mpa in seven days. It generates no heat, no gas and requires no organic solvents. In process of hardening, the TCP structure changes to Hydroxyapatite.

Materials and methods: We have used CPP in two TKA cases associate with bone defect, and 14 fracture cases. In a MRSA infected revision TKA case, reconstruction was performed with PMMA-VCM articulated spacers, and they was fixed to bone with CPP-VCM. MRSA infection has been well controlled and weight bearing could be done in 10 days after surgery. In another TKA case, large bone necrosis in femoral condyle was filled with CPP and Cementless inplant were placed on it. Seven days later, this patient could walk with a cane.

Results: CPP filled in bones were not absorbed for a year, and exess CPP in soft tissue were absorbed in several weeks. In 16 cases no side effects were observed during as long as one year.

Conclusion: Handling CPP is much easier than Hydroxyapatite brick or granule. CPP can be useful for total joint arthroplasty, especially in large bone defect or infected cases. It can replace a part of PMMA as a bone cement for implants in the near future.

Between 1989 and 1993, 158 patients with a total of 187 damaged knees underwent TKA using AGC-S prosthesis (Biomet). Of these patients, six required revision surgeries due to metallosis. The average period from the first operation to the revision was 68.0 months (range: 41–97 months). In all six cases, the plain X-rays taken immediately before reoperation, showed sinking of the tibial component. The withdrawn implants showed severe abrasion of the polyethylene used in the posteromedial area. The percent share of the tibial component averaged 90.3% (range: 85.3–93.5%) on the anteroposterior view, and on the lateral view averaged 83.1% (range:76.9–94.0%). The tibial components used for AGC-S type TKA can be characterized by the presence of a rim. In some cases, however, the rim cannot be placed on the tibial cortex, and this obliges the surgeon to select smaller components, resulting in a smaller percent share of the tibial component. The tibial component can sink in such cases. The sinking of the tibial component probably leads to malalignment and joint instability. Furthermore the insert with a flat surface was likely to induce articular instability, thus enhancing the abrasion of the polyeth

We present the results of our initial experience with the use of the Birmingham metal-on-metal Hip Resurfacing. The Birmingham Hip Resurfacing(BHR) consists of a high carbon chrome cobalt uncemented hydroxyapatite cupand a cemented femoral component. For patients with severe dysplasia adysplasia cup with screws was used. We utilise this kind of prosthesis for the younger patients (< 65 year). Excellent clinical results are encountered; none of the early problems aswith the old Wagner resurfacing (metal-on-poly) are seen. Our early results are similar to the encouraging results of the series of D.McMinn/R.Treacy.

From September 1998 through April 2001, 185 BHR arthroplasties were performed. The mean age was 49.7 year (16–75). More male patients were operated with this method than female patients (64%–36%). The aetiology was osteoarthritis (81%), necrosis (9%), dysplasia (CDH) (6.6%).

Results: The last 115 patients were reviewed with a follow up from 1 month to 2.5year. Only two patients were lost for follow-up because of death. There was no pain in 92.3% of the cases. The total Harris Hip Score had a mean of97.91, a median score of 100 (71–100). Merle d’Aubigné total Score was 17.36 (12–18). There was a strenuous activity in 70.2% of the patients.

The mean length of stay in hospital was six days (range: 2–26). Complications were: One fractured neck of femur, one ischial nerve palsy and one guide pin was left in the femur. All patients were followed on regular basis and the X-rays were studied for angle of preoperative neck of femur, postoperative angle of the femoral component, angle of cup placement and the parallelism of both components.

Conclusion: Performing only alternate bearings in patients under the age of 75, the metal-on-metal Birmingham Hip Resurfacing looks a good alternative in young active patients and the results are promising.

This study examined the inhibitory effects of anti-TNF-a antibody (anti-TNF) and a new bisphosphonate (TRK-530) on peri-implant oseteolysis in a rat model with continuous infusion of polyethylene particles. TRK-530 is a novel synthetic bisphophonate to have a direct effect on osteoclastic bone resorption as well as suppressive effects on bone resorbing cytokines from macrophages.

Materials and methods: Sixty Wister rats were randomized to three groups (n=20 each). In each rat, a Kirshner wire (K-wire) was inserted into the femur and polyethylene particles (HDPE, mean size; 2 microns) were continuously infused into the knee joint using an osmotic pump. The animals were subcutaneously injected with saline (control group) or 1 mg/kg of TRK (TRK group) or intraperitoneally injected with 100 mg of anti-TNF (anti-TNF group) every second day after surgery until 8 weeks. At 4 weeks or 8 weeks after surgery, rats were sacrificed. Rdiographs were evaluated for the presence of osteolysis, thereafter, garnulation tissues were stored for PCR analysis for IL-1 mRNA as well as TNF-a mRNA. Then, femurs were prepared for the histology.

Results: Radiographic peri-implant osteolysis was seen more frequently in TRK group compared to other two groups (p< 0.01). The interfacial membrane was significantly thinner in TRK and anti-TNF group compared to the control group (p< 0.01). The average number of osteoclasts around K-wire was significantly fewer in the TRK group compared to the other groups (p< 0.01). The expression of IL-1 mRNA and TNF-a mRNA was significantly suppressed in the TRK group at 8 weeks after surgery.

Discussion: The present study demonstrates that cumulative effects of TRK such as the suppression of bone resorbing cytokines as well as direct suppression of osteoclasts reduce the polyethylene induced peri-implant osteolysis. In addition, single anti-cytokine therapy appears not to be enough to inhibit peri-implant osteolysis in our model.

We developed LET (Lamellar Etched Titanium) porous structure as a new bone-prosthesis interface, which is made by piling up and fusing the etched titanium thin layers. This method can control pore size and porosity easily and obtain definite interconnective open pore structure (average porosity 65%, average pore size 500 micrometer)

Materials and method: The characteristics of bone ingrowth of LET coated with hydroxyapatite (HA) have been studied in a transcortical rabbit model.

We implanted two types of interface, one with LET and the other with a conventional rough surface structure, which is made with inert gas-shielded arc spraying (ISAS) technique (Ra 40 micrometer) Both materials have coated with HA using the flame spray method. Mechanical and histological studies were performed at 2, 4, 9 and 12 weeks.

Results: Previous scanning electron microscopy study of HA coated LET revealed an even HA layer consecutively distributed from its surface to the bottom without pore obstruction. Mechanical detaching tests showed that the interfacial tensile strength of LET increased with time and were significantly higher than that of ISAS at 4, 9 and 12 weeks (P< 0.05). Histological studies demonstrated that LET had induced deep and wide bone ingrowth into the pore structure. Even at 2 weeks, the immature bone trabeculae were observed stretching to the bottom of LET and, at 9 and 12 weeks, the new bones infiltrated into porous structure changed into maturing osseous tissue. Further, residual new bones of the detached side were observed in and on the pores of LET. It suggested that detaching occurred inside of new bones. In contrast, no residual bone was found onto ISAS implant at 4, 9 and 12 weeks.

Conclusion: The LET structure was proved to have desirable properties for bone ingrowth and, furthermore, the osteoinductivity of HA could enhance its character.

Flexion after total knee arthroplasty (TKA) has recently been improved by changing implant designs, surgical techniques and early postoperative rehabilitation protocols. Especially for Asian people, deep knee flexion is essential because of their life style. Small numbers of patients can achieve full flexion after TKA, however, most current prostheses are not designed to allow deep knee flexion safely. Furthermore, the kinematics involved in knee flexion greater than 90 degrees in cases of TKA is still unknown, even though fluoroscopic studies have shown the paradoxical anterior femoral translation in posterior cruciate retaining (CR) TKA with knee flexion up to 90 degrees. The purpose of this study was to determine the femoro-tibial contact pattern in deep knee flexion.

The knee that had been operated upon was passively flexed from 90 degrees up to the maximum flexion under anesthesia soon after the surgery. Lateral roentgenograms of the knee were taken during flexion, and the three-dimensional kinematics was analyzed using image-matching techniques. Nine patients with CR type were included.

The average maximum flexion angle was 131.8 °. The contact point moved posteriorly with deep knee flexion except for one patient. Five out of nine patients showed external rotation of the femoral condyle. Two patients showed internal rotation, and the other two exhibited no rotational movement. None of the patients showed dislocation or disengagement of the components. At the maximum flexion, the edge of the posterior flange of the femoral component contacted the polyethylene insert.

This study was performed under non-weight-bearing conditions, but deep knee flexion is not usually performed in weight-bearing conditions. Most of the CR type showed posterior roll back during deep knee flexion. The design of the posterior flange of the femoral component should be changed to prevent damage to the polyethylene.

New prosthesis designs should be compared to a standard implant in randomized studies evaluated by radiostereometric analysis (RSA). The Unique customized prosthesis (UCP) is a newly developed concept for fitting uncemented prosthesis to the exact internal shape of the proximal femur [1]. We evaluated the new UCP design with the null hypothesis that this implant would be no more stable than a standard cemented implant.

Material and methods: 38 patients, mean age 51.6 years (31–65) were randomized to a UCP HA coated femoral stem or an Elite Plus (DePuy) cemented stem. All patients were implanted with a Duraloc (DePuy) uncemented cup except one patient with a protrusio who was primary impaction grafted with a cemented cup. Most patients received a Zirconium head, and all heads were 28 mm. The femoral stems were fitted with 3 tantalum balls and 4–10 tantalum balls were implanted in the femur during operation. RSA pictures were taken postoperatively, after 6 and 12 months.

Results: The Elite Plus stem rotated more into retroversion after 6 and 12 months (0.79° versus 0.31° after 12 months, P< 0.05). Nearly all of this rotation took place during the first 6 months. The Elite Plus stem migrated medially while the UCP migrated laterally (0.04 mm medially versus 0.03 mm laterally, P=0.06). The Elite Plus stem also migrated more distally than the UCP (0.17 mm versus −0.06 mm, P=0.055).

Discussion: Customized implants were more stable than the cemented Elite Plus prosthesis. Compared to other results with the Elite Plus rotations and migrations were small in this study [2]. Initially all patients had good clinical results, and only by long time follow up any clinical differences due to the small differences in stability as measured by RSA can be found.

The role of the posterior cruciate ligament (PCL) after total knee arthroplasty has been controversial. Previous studies have reported that function of the preserved PCL after TKA was questionable and that it was difficult to determine the appropriate PCL tension to reproduce rollback. However, several in vivo studies have reported that prosthesis geometry directly affects knee kinematics, making it difficult to determine which factors most influence knee kinematics. The purpose of this two-center, two surgeons study was to evaluate knee kinematics of a single design of CR TKA. A total of 23 TKAs were studied fluoroscopically during a single-limb step-up/down maneuver. The average patient age at the time of TKA, knee score (HSS/KSS) and ROM were 70.6 years, 91.1 points and 116.9 degrees respectively. All patients had a PCL-retaining prosthesis of the same design using an unconstrained “flat” tibial insert. TKAs were performed by one surgeon at each hospital (Group 1:13 knees, Group 2: 10 knees). Both groups of knees exhibited ‘screw-home’ type axial rotations from 20° of flexion to full extension. In Group 1, rollback occurred early in the flexion range and was maintained until 80° of flexion. In Group 2, the lateral condyle exhibited rollback in early flexion, but both condyles translated forward as flexion increased to 80°. Medial and lateral contact were more posterior in Group 1 over most of the range of motion (p< 0.05). Although femoral rollback has been infrequently observed in similar studies of PCL retaining arthroplasties, our two-center, two surgeon data suggest that rollback can be achieved using this unconstrained prosthesis with PCL retention. However, there were consistent and statistically significant differences in the knee kinematics exhibited by the two groups of patients.

Polyethylene wear in total knee arthroplasty (TKA) is a complex and mutifactorial process. It is generally recognized that wear is directly related to a material wear factor, contact stress, and sliding distance. Conventional methods of predicting polyethylene wear in TKA mainly focus on peak contact stress or subsurface shear stress using finite element method analysis. By incorporating kinematics and contact stress, a new predictor for polyethylene wear in TKA (“Wear Index”) has been developed. The Wear Index was defined by multiplying deformation by femoro-tibial sliding velocity. The purpose of this study was to determine the predictive value of the Wear Index for polyethylene wear in TKA using both a numeric and an in vitro model.

Four commercially available total knee prostheses were modeled for this study. Deformation and sliding velocity were calculated based on the three-dimensional geometry of the components and the gait kinematic inputs using Hertz’s formula. One specimen of each of the four types of total knee prostheses was mounted on a custom-designed knee simulator. Vertical loads and flexion-extension uni-axial motion were simulated using computer controlled servohydraulic actuators. The same gait kinematic inputs used in the theoretical study were used in the simulation test. After the simulations, the surface of the tibial insert was examined microscopically and macroscopically and compared with the theoretically generated Wear Index.

This study showed a high correlation between the numeric model and the simulation. The depth of wear on the tibial insert correlated significantly with the Wear Index. Microscopic findings also demonstrated a good correlation between the Wear Index and observed wear patterns. Sliding velocity is an important factor for understanding wear in TKA. In conclusion, this study suggests that the Wear Index is a reliable predictor of polyethylene wear in TKA, as it incorporates both contact stress and kinematics in its calculation.

It is widely accepted that a wide contact area between bone and artificial materials is necessary in the fixation of hip joint prostheses. It is also considered important that the load should be applied to the proximal femur. However, these two concepts are contradictory in that the contact point cannot be determined in a wide contact area. Therefore, in this study, we revised the available concepts to improve the method of fixation of joint prostheses using finite-element-method (FEM) analysis of the equivalent mathematical models. The first model was designed based on the intramedullary cruciate fixation stem. In this model, the total contact area was limited to the small area of legs-on-plane. Another model was designed based on the fit-and-fill-type stem, and in this model, the total contact area of the plane-on-plane was equal to the total surface area of the stem. In the plane-on-plane model, there was an unstable vibrating pattern in stress distribution, and we considered that deterministic cha

Introduction: Septic total hip arthroplasty is a devastating complication. Most treatment protocols for infection of more than 2 – 3 weeks duration recommend removal of the prosthesis and cement followed by 4 – 6 weeks of IV antibiotics. Results using an antibiotic spacer to allow mobility of the patient and local antibiotic deliverance by elution from the spacer are reported.

Methods: Since January of 1994, antibiotic spacers have been used as adjunctive treatment along with IV antibiotics and prosthetic resection in 18 septic total hips. The spacer is fashioned intraoperatively using a femoral Rush Rod as reinforcement. Antibiotics are chosen based upon either a previous hip aspiration result or empirically chosen on intraoperative gram stain results.

Results: Fifteen patients have been reimplanted and are, to date, apparently free of infection. The average time to reimplantation was approximately 8 weeks (range: 4 to 24 weeks). Two patients were unable to be reimplanted due to persistent infection and currently have resection arthroplasties. One patient died prior to reimplantation.

Discussion and conclusions: The use of a spacer has allowed the mobilization of the patient in a manner similar to a total hip arthroplasty while keeping the patient’s leg length approximately the same. Reimplantation is less traumatic for the surgeon as well as the patient and allows for the local deliverance of antibiotics to the tissues similar to the use of antibiotic beads. The authors believe the use of an antibiotic spacer in the treatment of septic total hip has been extremely useful in these difficult cases.

Introduction: This study addresses the long term results of 1225 uncomplicated primary total knee arthroplasties performed between 1986 and 1995, using one design with various tibial fixation methods.

Methods: 1225 primary total knees were performed using a press fit total condylar cruciate retaining design. 108 cases were eliminated because of death and 171 due to lack of follow up leaving a group of 946 knees. Mean time insitu is 9.2 years. 500 knees had both the tray and stem cemented, 374 had only the tray cemented, and 72 used no cement. Both clinical and radiographic Knee Society Scores were tabulated preoperatively and annually thereafter. The SF-36 has been recorded both pre and postoperatively since 1993.

Results: Overall revision rates for the cemented, tray only and non-cemented groups were 1.0%, 3.4% and 12.5%, respectively. A combined 20 cases had the tibial component revised due to polywear and osteolysis with 0.6% from the cemented group, 2.4% from the tray only group and 11.1% from the tray only group. The joint portion of the Knee Society score was comparable for the cemented and tray only groups (88.9 and 88.3, respectively) but only 80.9 for the non-cemented group.

Discussion and conclusion: Using a component design that meets the needs of the majority of patients regardless of bone quality has proven to be successful and cost effective for this institution. The authors believe these excellent results and low revision rate for loosening indicate this design has much to offer with its flexibility of tibial fixation.

Malalignment and cement mantle quality have been implicated in loosening of the Charnley stem [2]. Several types of cemented prosthesis have adopted a modern insertion technique, which has not been available for the Charnley stem. We implemented a new technique for insertion of the Charnley stem via the Hardinge approach including a distal centralizer, broaches and specific entry into the femoral canal via the piriformisfossa, and compared it to the old technique for alignment of the stem and cement mantle quality.

Material and methods: Forty-two patients (34 women) operated with an old technique were compared with forty-nine patients (39 women) with the modern technique. All patients were operated through the Hardinge lateral approach, with primary hemiprosthesis by residents. Post-operative anteroposterior and true lateral radiographs were taken and evaluated for cementing quality [1], mantle thickness in the 14 Gruen zones, and alignment of the femoral stem in both planes.

Results: For the Barrack classification there was 9 grade A with the new technique, compared to none with the old (p< 0.0001, Table 1), and only 1 grade B with the old technique. The cement mantle thickness was more uniform (p< 0.0001), and the mean thickness was higher with the new technique for zones 1-3, 5-10 and 12 compared to the old technique. Alignment as measured in the lateral plane by the mean anteroposterior angle was 5.2° with the old technique, compared to 2.2° for the new technique (p=0.0001). In the frontal plane there was no difference.

Discussion: A modern insertion technique for the Charnley stem gave a much better cementing quality, better cement mantle uniformity and a thicker mantle in the critical zones, and more neutral alignment of the stem. As poor alignment and thin or absent cement mantle has been implicated in loosening the results should hopefully confer into longer survival.

The ‘first generation’ Metal on Metal bearing devices was typically produced from cast, high carbon CoCrMo alloy and was in the as-cast condition. They exhibited course, hard primary, and block carbides supported by a softer matrix material. This bi-phasic condition has been verified through reported literature and forensic scientific studies of ‘long-term survived’ retrieved ‘first generation’ devices. The as-cast microstructure of CoCrMo alloys possesses superior wear resistance to the microstructures formed following post cast thermal treatments. It has been well reported that the improvement of mechanical properties, such as tensile or fatigue strength, can be achieved through the thermal treatment of this alloy. Thermal treatments of this alloy have been found to alter its’ microstructure with a significant modification to the carbide phase morphology. The modifications vary with a tendency for a refinement of the carbide size through dissolution of the chromium and molybdenum through solid state solution. Through the examination of the wear patterns of retrieved devices and wear testing of this material in its’ various microstructural conditions, it has been shown that modifications to the carbide morphology, to achieve improved mechanical properties, reduces its’ bio-tribological properties/performance leading to a lower wear resistance. The as-cast carbide morphology is the most mechanically stable condition and with its’ volume fraction, reduces the potential for adhesive wear of the matrix through ‘matrix to matrix’ contact of the two opposing bearing surfaces. It has been reported that abrasive wear is the typical mechanism for metal on metal bearings due to the generation of ‘third body’ particles from carbide asperity tips fracturing during the initial ‘running-in’ period [typically 500k to 1M cycles]. After this stage the carbides become almost level with the surrounding softer matrix material with ‘third body’ scratches dominating the surface topography. Evidence of surface pitting on ‘first generation’ devices [McKee Farrar and Muller] and modern high carbon wrought devices [Metasul] has been attributed to adhesive/fatigue wear following surface-to-surface contact. Therefore, in microstructural conditions, where there is a reduced carbide volume fraction, or no carbides present, wear resistance is reduced. To test this hypothesis two wear tests have been carried out on CoCrMo samples produced from the same chemistry alloy, with varying microstructures, using Calowear [abrasive] and Pin on Dist [adhesive] tests. The as-cast microstructural condition was determined to have the lowest wear coefficient [k=mm3/Nm] in both tests, however statistical significance at 90% confidence interval was only confirmed in the Calowear Test. Examination of wear scars confirmed the mechanical stability of the as-cast carbide phase. It is noted, however that there are papers which have been published offering a divergence of opinion to this hypothesis and which have been considered by this author.

Introduction: Concerns of backside wear have made the use of the all polyethylene tibial component a viable choice in primary total knee arthroplasty. This study compares the results of two groups, one with a modular tibial component and one with an all polyethylene tibial component.

Materials: Between 1986 and 1995, 670 patients underwent total knee arthroplasty using one design with a PCL retaining prosthesis. 500 patients in this group were implanted with a modular tibial component and 170 an all polyethylene tibial tray. The groups were comparable in sex and age (74.1 years for the metal trays and 75.8 years for the all polyethylene components.). The average follow up is 83.9 months for the metal tray group and 74.8 months for the all poly tibial group. The arthroplasties were evaluated annually using the Knee Society guidelines.

Results: The postoperative Knee Society Score were 74.5 (metal) and 73.9 (all polyethylene). Joint specific scores for the all polyethylene were slightly higher at 89.9 compared to 88.5 for the metal tray group. Revision rates were 1.8% (3 cases in the polyethylene group) and .8% for the metal group (8 cases). The 3 revisions in the all polyethylene group were for late infections while 5 of the 8 in the metal group demonstrated polyethylene wear/osteolysis.

Discussion and conclusions: The clinical results of the all polyethylene group are equal the modular tibial tray group. Because of the excellent radiographic results and non-existent mechanical failure rate to date, the all polyethylene group also provides an opportunity to reduce wear debris with subsequent osteolysis.

Introduction: The purpose of this paper is to present the results of a prospective study involving one stem design used in primary total hip arthroplasty with three different surface enhancements to include a simple textured geometry, a plasma sprayed coating and an hydroxyapatite (HA) coating.

Methods: Between 1990 and 1994, 138 patients underwent primary THA using a simple femoral component. Thirty-eight patients received a textured geometry while 50 were implanted with a HA coated stem and 50, a plasma sprayed stem. The hips were evaluated annually both clinically and radiographically. The results are reported using the Harris Hip Score and the Engh radiographic scale to determine the level of bone ingrowth and type of fixation.

Results: The average length of follow up is 8 years 11 months (range: 6 to 10 years). The average postoperative Harris Hip scores were 81.0% for the textured stems, 89.6 for the HA coated stems and 85.7 for the plasma sprayed stems. The revision rates are 13.2% for textured stems, 0% for HA and 5.4 % for plasma sprayed. Radiographic results show that fixation of the 3 surface coatings to be optimal in 100% of HA, 88.2% in plasma sprayed and 84.2% in textured.

Discussion and conclusion: At this point in the study, it is obvious that the coating enhancement of choice is hydroxyapatite. The next step in this research will be to match the HA coated stems with a comparable porous coated stem of the same design for further comparison.

A total knee design has been developed to support high flexion requirements of post-total knee replacement lifestyles. The extent of flexion, following total knee replacement, is influenced by relative femoral tibial kinematics, posterior knee soft tissue impingement, patella and patellar tendon tracking, preoperative knee flexion, and postoperative physical therapy. A new implant design incorporates features to prevent posterior tibial displacement in high flexion, improved conformity of the femoral/tibial articular surface contact to 155 degrees of flexion, greater femoral/tibial articular surface contact area in high flexion, and a shortened patellar tendon pathway. The requirement for tibial internal-external rotation during some knee flexion activity is accommodated by a rotating tibial poly-ethylene option within the implant system. Laboratory tests indicate the achievement of greater articular surface contact in high flexion conditions through extending the posterior femoral condyle curvature and accommodating the tibial polyethylene articular surface. Joint simulator testing indicates improved wear performance of the high flexion design. A prospective controlled multicenter clinical trial has been initiated to evaluate this high flexion implant design along with surgical techniques and post-surgery physical therapy developed to support patient achievement of high knee flexion following total knee arthroplasty.

We developed K.K.S. (Keio-Kyocera Series) THA sytem. The aim is to develop original THA system suitable for Japanese patients. We produced MCF (means Medullary Canal Filling) stem, based on the anatomical anlysis of Japanese typical osteoarthritic patients (53 cases) by the measurements with CT scan. By the use of this stem, excellent canal fitting and initial rigid fixation can be obtained. We used this stem together with non-cement porous socket from 1992. At first the surface of this stem was smooth (S groupe), from 1994 the surface was altered to porous surface (P groupe), and then from 1995 HA coating to porous surface (H groupe) was added. The purpose of this study is to compare the biological fixation ability among stems with same shape and different surface.

Material and methods: Materials were patients for which Non-cement K.K.S. THA was done, 33 cases, 35 joints. Average age at operation was 55 (43-64) years old. Follow-up terms were 5-8 years. According to stem surface, all cases were divided to 3 groupes (S: 14 joints, P: 10 joints, H: 11 joints) and evaluated clinically and radiographically. The evaluation was done at the point of 5 years after operation for all cases. Clinically existence of thigh pain was evaluated. Radiographically sinking of the stem and osteolysis around femur were evaluated.

Results: Thigh pain was existed on S group: 6/14; 43%, P groupe: 0/10; 0%, H groupe: 2/11; 18%. Stem sinking was seen only on S groupe: 12/14; 84%. Osteolysis was seen only on 1 joint in S groupe. The result of S groupe was apparently poor clinically and radiographically.

Conclusion: To keep the early biological fixation of stem, not only anatomical shape for getting excellent canal fitting but also porous surface structure is needed.

New generation alumina-on-alumina (A-A) prostheses have been introduced to try and overcome the problem of osteolysis often attributed to polyethylene wear particles liberated within conventional metal-on-ultra high molecular weight polyethylene (UHMWPE) joints. This study uses a hip simulator to compare the volumetric wear rates of five different radial clearances of A-A joints. Atomic force microscopy (AFM) provided topographic characterisation of the prosthesis surfaces throughout the wear test.

Materials and methods: The wear test was performed on the Durham hip joint wear simulator. The 28 mm diameter alumina ceramic couples investigated were manufactured by Morgan Matroc Ltd., in accordance with ISO 6474. Four radial clearances (33, 40, 48 and 74 μm) of A-A joints were tested to one million cycles with 25% new-born calf serum as the lubricant. Contact mode AFM (TopoMetrix Explorer SPM) was used to produce a topographical map of the poles of the four alumina heads every 0.1 million cycles. Every 0.2 million cycles the wear was assessed gravimetrically using a Mettler AE 200 balance (accurate to 0.1 mg).

Results and discussion: There was no measurable wear of either the heads or cups during this one million cycle wear period. Throughout the wear test the alumina equiaxed grain structure became apparent on the AFM images, the mean alumina grain size was 2 μm. The grain surfaces were below the mean femoral head surface height. Such topography was not observed on an as-received head. Some granular pull-out also took place. As the wear test proceeded, the average area surface roughness increased from 2.33 nm to 4.42 nm for the heads but stayed relatively constant for the cups (from 2.75 nm to 2.97 nm).

Conclusions: The very low wear produced by these A-A hip joints is very difficult to measure gravimetrically as it is close to the limits of resolution of the weighing equipment. The surface topography analysis, however, shows changes to the ceramic surfaces during the wear test and gives an indication of the wear processes and lubrication regimes acting within such joints. The authors wish to thank EPSRC for funding this research and Morgan Matroc Ltd. for supplying the joints.

Longevity of the implants is the most respected factor in THA. Except from this fact, complications like dislocation, wear and osteolysis are reported in literature most frequently. But there is an underestimation in the orthopedic community in the importance of joint function, which is directly related to accurate restoration of joint geometry. This might be due to a lack of functional parameters for the measurement and availability of adequate implants for accurate restoration of joint geometry.

From our point of view the two problems: stable stem fixation and joint geometry have to be addressed separately: Safe stem fixation on the one hand, adequate joint geometry on the other hand. With the use of standard implants compromises have to be made on either side. To avoid this dilemma, we propose alternative systems: A modular system with interchangeable necks as a standard implant for better fit and adequate joint geometry or a custom implant. In the presentation we address the interference of stem fit and joint geometry and discuss problems and advantages of modularity and custom implants.

Introduction: This study investigates the influence of surgical approach on the early migration of a cemented Total Hip Replacement (THR), assessed by Roentgen Stereo-photogrammetric Analysis (RSA). Rapid early migration has been correlated with premature implant failure.

Method: 46 patients awaiting THR were allocated into Posterior Approach (PA) and Lateral Approach (LA) groups. RSA was used to assess post-operative stem position and migration at 1 year. Post-operative gait was examined for a subgroup of patients.

Results: There was no difference in initial stem position within the medulla. Significant differences in distal migration were found; (LA 0.78±0.07mm and PA 1.27±0.15mm), p< 0.01. Posterior head migration for the PA group (0.78±0.18mm) was twice that for the LA group (0.46±0.08mm), p< 0.05. The PA group showed greater medial migration of the prosthesis tip (0.62±0.24mm), compared to the LA group (0.11±0.08mm), p< 0.05. During gait, the legs of the PA group were relatively internally rotated when compared to those of the LA group.

Discussion: The PA implants rotate internally and into valgus further than the LA implants. The starting positions of the prostheses were the same with similar cement and prostheses characteristics. We can infer that surgical approach and therefore muscle function have a significant effect upon component migration. During gait, the PA group has relatively internally rotated legs, probably due to short external rotator weakness. Hence, the internally rotating torque on the femoral stem will be larger, explaining the rapid migration in this direction. With the LA approach, the abductors are likely to be damaged. Therefore, the PA joint reaction force will be more laterally directed, explaining the higher coronal plane rotation rates seen in this group.

Conclusion: Profound differences exist in early migration, between the LA and PA. Different muscle function may account for this and probably influences long-term outcome.

Our experience with metal/metal desings in France date from 1994. The goal of this study is to communicate our primary and comparative clinical results of 90 implants followed a minimum of 6 years

Material and method: We have reviewed the first 94 patients from our first year using metal/metal.90 case files were complete and we compare thes patients (group 1) to a control group of 90 patients receiving ceramic/poly couple, operated in the same time period (group two) with the same hybrid TH system. Average follow up: Five years and eight months.

Results and discussion: 4 of the 94 were unavailable for follow up at six years. None of these patients experienced clinical problems relared to the metal/metal. The clinical results (Merle and Harris score) are all good or excellent and there is no difference between the 2 groups. The x-ray results: For acetabular cup the two groups are identical and for femoral component (Barrack evaluation) all two groups have the same quality of cementation and maintain the cement mantle integrity achieved post-op. We decided therefore to examine specially the RLL changes in zone seven (comparison 3 month x-ray/latest follow-up x-ray); significant differences between the two groups were found in this study: The lower incidence of zone seven radiolucent changes in group one indicates a better clinical tolerance in the metal/metal configuration (p=0.0256). Considering the results reported here and the advanced studies, we can confirm that metal/metal systems are not the unique answer to PE-wear and THA longevity, but it is one solution that is available today and seems trustable.

A method to extensively cross-link polyethylene for total hip application has been developed and tested in hip wear simulation. Extensively cross-linked polyethylene was prepared by exposing GUR 1050 polyethylene resin to 90 kg to 110 kg of e-beam radiation. For total hip application, the material was evaluated in an AMTI joint simulator in normal debris-free conditions and in a Shorewestern simulator for the adverse condition of added bone cement and aluminum oxide debris. The normal condition testing was conducted to 30 million cycles, while the adverse condition tests were conducted to 5 million cycles. Femoral head sizes from 22 mm to 46 mm were evaluated. The wear performance of extensively cross-linked material was compared to control material (GUR 1050 gamma sterilized in nitrogen). The results demonstrate a significant improvement in wear (greater than 80 percent reduction) of extensively cross-linked GUR 1050 acetabular components compared to the control acetabular components. The adverse condition wear of both materials was greater than the normal wear; however, when compared to the controls, the extensively cross-linked material had improved wear performance in both normal and adverse conditions. The wear of femoral heads larger than normal 32 mm sizes showed accelerated wear in the control material and desirable low wear in the extensively cross-linked condition. The polyethylene particles generated in the wear simulation were of similar size and shape between the extensively cross-linked and controlled polyethylene. As demonstrated in the laboratory simulation, this extensively cross-linked polyethylene has the potential to substantially reduce particular debris generation in total hip applications. A multicenter randomized controlled clinical study of extensively cross-linked and control acetabular components is ongoing.

Infected hip prosthesis, a devastating complication of primary total hip arthroplasty (THA) can lead to a serious condition. We report here the treatment outcome of our method of two-stage revision THA for infected hip arthroplasty using a temporary antibiotic-impregnated cement spacer for the period between resection and reimplantation.

Between 1996 and 2000, we performed two-stage revision THA using a temporary antibiotic-impregnated cement spacer on eight hips in eight patients with infected hip arthroplasty including hemiarthroplasty, with the infection presenting itself between four days and 19.4 years after last operation. There were four females and four males, with a mean age of 67 years (58 to 72). The mean period of follow-up was 2.5 years (0.3 to 4.3). Cementless THA was implanted as the second srage procedure. Bone defects were restored with frozen allografts. The clinical outcome was evaluated using the hip score of the Japanese Orthopaedic Association (JOA hip score).

The duration of follow-up was 33.9 months (range, 8 to 55 months). The mean JOA hip score at follow-up improved from 32.6 (19 to 74) to 77.1 (59 to 96). The mean interval period was 10.3 weeks (range, 6 to 19 weeks). Seven patients with infected hip arthroplasty successfully received implantation by two-stage cement-less revision THA.

One patient with MRSA infection had a recurrence after four months of revision of THA. However, the two-stage procedure using a vancomicin-impregnated bone cement spacer and beads implantation successfully treated this patient 14 months after the first revision of THA. No recurrence of infection was found at 42 months of follow-up.

These results suggest that two-stage revision THA using a temporary antibiotic-impregnated cement spacer is a useful technique for infected hip arthroplasty.

Introduction: The Step Activity Monitor (SAM) is a microprocessor worn on the ankle that measures ambulatory activity in real time.

Methods: Activity magnitudes, speed parameters and activity patterns were analyzed in 31 patients with 37 primary total hips. Wear was measured from digitized radiographs using a validated two-dimensional, edge detection-based computer algorithm.

Results: On average, patients walked 5.6 hours per day (range: 1.9–9.8); averaging 5,266 gait cycles (range: 1,737–11,805), at 20 cycles/minute (range: 12.7–32.8) with a maximum speed of 63 cycles/minute (range: 45.0–88.0). Fast and very fast walking (30–49 and > 50 cycles/minute) accounted for 9.4% and 4.4% of total walking time. Patients started and stopped walking about 66 times per day (range: 34–113), with about 81 cycles between stops (range: 28.1-200.1) in average active intervals of 5.3 minutes (range: 3.3–10.3).

There was no difference in the average number of gait cycles between females and males. However, polyethylene wear per million cycles was significantly higher in males (p=0.006). Even after adjustment for greater height and weight in males, their wear rate was still significantly higher (p< 0.01). Males walked at a higher average speed (p=0.07), spent 33.9% more time walking fast or very fast, had 4% more starts/stops per day, with 13% less strides between stops. The percentage of time spent walking slow (5–9 cycles/minute) was negatively correlated to wear (p< 0.05).

Discussion and Conclusion: The SAM allows assessment of patterns and intensity of joint use. Similar to a set of automobile tires, polyethylene wear is a function of the amount and type of use; faster walking with more frequents starting and stopping is associated with a higher polyethylene wear rate. As the clinical performance of crosslinked polyethylenes is being monitored, it is critical to consider the influence of the amount and type of patient activity on wear.

It is widely accepted that a wide contact area between bone and artificial materials is necessary in the fixation of hip joint prostheses. It is also considered be applied to the proximal femur. However, these two concepts are contradictory in that the contact point cannot be determined in a wide contact area. Therefore, in this study, we revised the available concepts to improve the method of fixation of joint prostheses using finite-element-method (FEM) analysis of the equivalent mathematical models.

The first model was designed based on the intramedullary cruciate fixation stem. In this model, the total contact area was limited to the small area of legs-on-plane. Another model was designed based on the fit-and-fill-type stem, and in this model, the total contact area of the plane-on-plane was equal to the total surface area of the stem. In the plane-on-plane model, there was an unstable vibrating pattern in stress distribution, and we considered that deterministic chaos existed in the stress filled wide

Carbon nanotubes are an exciting new type of material and have extraordinary properties (1). A special category of carbon nanotubes (multiwalled or MWNT) is flexible yet have tensile strengths 200 times stronger than traditional carbon fibers (2). Because of their extremely large surface area-to-volume ratio, theory suggests that MWNTs can bond more strongly to polymethylmethacrylate (PMMA) than any other material tested (2). The combination of large tensile strength and strong interfacial (PMMA matrix) bonding suggests that when added to bone cement, MWNTs could bridge and arrest fatigue or impact cracks and thereby favorably improve the clinical performance of bone cement.

The objective of this study was to determine the validity of this hypothesis and whether MWNTs can significantly improve the tensile properties of PMMA. Methods MWNTs (20–30 nanometers in diameter, 20–100 microns long) were grown on a fused quartz substrate by the thermal decomposition of xylene in the presence of a metal catalyst. They are formed in well-aligned mats and grow perpendicular to the walls of a tubular reactor. As a first approach MWNTs were separated and dispersed through the liquid monomer component of PMMA by using an ultrasonic probe. The remaining polymer component was then mixed with this dispersion and the product was used to prepare specimens by casting in molds. Since prior work in other polymer systems (3) indicated that small concentrations of MWNTs could significantly affect a polymer’s physical properties, only fractions (1/16, ¼ and ½) of 1% of MWNTs (by weight) were used to prepare tensile test specimens. Control (0% MWNTs) and experimental (MWNT containing) groups of PMMA specimens were cured in air at room temperature for 7 days and then pulled to failure at 6 mm/min in a protocol conforming to ASTM D638. Maximum load, strength, results a total of 41 specimens have been prepared and tested: 13 controls, 9 with 0.063%, 10 with 0.25%, and 9 with 0.5% (by weight) of MWNTs. Carbon nanotubes improved the tensile load bearing properties of all experimental groups from 17% to 24%, and these values were significant (p=0.01 and p=0.02) for the 0.25% and 0.5% concentrations. The lowest concentration of MWNTs made the smallest improvement (17%) and this was not significant (p=0.07). Scanning electron microscopic examination of the fractured surface revealed nanotubes that were well distributed throughout the matrix.

Discussion: These preliminary results clearly demonstrate that carbon nanotubes can significantly improve the mechanical performance of bone cement. This result is especially encouraging because the MWNTs were added only to the monomer component. Additional performance enhancement may be expected from ongoing work using higher concentrations of MWNTs and their dispersion into the polymer component of bone cement in addition to the monomer component.

Since MWNTs are also electrically conducting and have magnetic properties, MWNTs may also help dissipate the heat generated by polymerization or permit bone cement with an “engineered” mechanical anisotropy. Although static tensile tests are an incomplete measure of bone cement, these preliminary results are very encouraging and motivate continuing study of the more clinically relevant (impact resistance, fatigue properties, etc.) measures of the mechanical performance of MWNT augmented bone cement.

Introduction: Ceramic/ceramic articulation has a long history and is accepted as a low wear couple for total hip joint application. Due to the requirements for strength of the ball-head it may be necessary to combine products from different Alumina manufacturers.

Material and methods: Alumina components according to ISO 6474 for commercial hip joint prosthesis were obtained from 3 sources and subjected to a series of simulator tests up to 5 million cycles. Variations were the type of testing and the quality and type of the Alumina. Wear tests were performed with two different types of simulators and different protocols also including micro-separation testing. Wear was characterised by weight loss, change in surface appearance and particle analysis.

Results: Standard wear testing yielded very low wear rates below 0.5 mm3 per million cycles for the Alumina combinations of the third generation with a running in period and a steady state wear after 1 million cycles. Increasing the inclination of the cup up to 60° did not increase the wear rate. Mixing the components from various sources did not affect the wear rate significantly. Micro-separation testing increased the overall wear rate significantly and showed clinical relevant patterns with grain pullout and grain relieve. After a running in period a steady state without “avalanche” effect was observed again. The particle analysis compared favourably with retrieval studies. Although the wear rate was lower for the mixed couples it was statistically not significant.

Conclusion: An improved test method for ceramics demonstrates clinically relevant wear in respect of amount, appearance and particle size. The new generation Alumina is more wear resistant and less sensitive to cup position and to micro-separation. Mixing of Alumina components from a single implant manufacturer does not change the low wear rates of ceramic/ceramic articulation and can, therefore, be applied.

Introduction: Alumina exhibits excellent hardness and wear properties, however it is a brittle material with an inherent risk of fracture. Therefore, the feasibility of a new family of Alumina based ceramics with improved toughness for hip joint articulation applications was investigated.

Materials and methods: The addition of 25% Zirconia to Alumina during the manufacturing process to achieve the objective has been proposed. Two types of Zirconia Toughened Alumina (ZTA) ceramics were analysed; one binary and the other pentary by composition. Following tests were used: structural analysis, mechanical testing of components, determination of hardness (HV), fl exural strength (ASTM C1161), indentation fracture toughness, X-ray diffraction (XRD), aging (accelerated and real-time) and wear simulator testing. The test data was analysed by descriptive statistics.

Results: The structure of the two ZTAs is similar with small-grained Zirconia dispersed in a matrix of larger grained Alumina. X-ray diffraction analysis showed no phase transformation after accelerated and real-time aging and the strength values did not change. Flexural strength was statistically significant increased by > 50% over Alumina. The indentation fracture toughness was also increased by up to 50% while the hardness of the ZTA ceramics was not affected. The wear testing showed that ZTA – ZTA couples articulating against themselves produce not significant lower wear than Alumina – Alumina couples, but the combination of ZTA ball-heads with Alumina inserts produced significantly lower wear rates, also in micro-separation.

Conclusions: The toughness and bending strength of the Alumina was successfully increased while all other properties of the Alumina were maintained. No change in properties after aging was observed and the wear properties of the ZTA were lower wear than for Alumina. Zirconia Toughened Alumina looks promising for the next generation of fracture and wear resistant ceramic bearings.

Objective: We had performed bipolar hemi-arthroplasty for osteoarthritis of the hip, with the technique of ace-tabular reaming until 1991. We studied the long-term results of this procedure radiographically.

Materials and methods: 62 patients (70 hips) were followed up for at least eight years after bipolar hemi-arthroplasty without cement. The diagnosis of all patients was osteoarthritis of the hip, which mainly came from dysplasia of the hip. The patients consisted of 13 men and 49 women. The average age at the operation was 43 years old (36–74 years old). The average duration of follow-up was 11 years (8–14 years). Smooth-surface press-fit type stem (Omnifit, Osteonics) was implanted for all cases. Focal osteolysis around component, the migration of the outer head and the subsidence of stem, were evaluated radiographically. By reviewing serial A-P radiographs, the first recognition of osteolysis and the extension of the lesion were researched.

Results: The mean migration of the outer head was 3.0mm medially and 9.1mm superiorly. The mean subsidence of stem was 7.2mm at final follow-up. The ace-tabular focal osteolysis was identified in 31 hips (44 %) and was first recognized at average 3.1years(1–9years) postoperatively. The femoral focal osteolysis was identified in 33 hips (47%) and was first recognized at average 2.3 years (1–9years) postoperatively. After the first recognition of osteolysis, the lesion was progressively spreading, especially on femoral side.

Conclusion: From these results, bipolar hemi-arthroplasty with the technique of acetabular reaming should not be indicated for osteoarthritis of the hip. This procedure causes osteolysis, which is progressive, and the migration of the outer head so often that it is difficult to preserve acetabular bone stock.

We have utilized arthroscopic arthroplasty of the hip joint (arthroscopic partial resection of the acetabular edge) for the treatment of advanced osteoarthritis of hip joint.

We have utilized arthroscopic Arthroplasty to widen the joint space and tried to improve the outcome of joint preserving operation. We have treated advanced osteoarthritis of nine hip joints of eight patients (age from 41 to 56, averaged 44.3 years old) by arthroscopic arthroplasty in the past six years. The patient was put on the surgical traction table in the supine position. Arthroscope was inserted into the hip joint from antero-medial approach under fluoroscopic control and the acetabular edge was shaved until bleeding from subchondral bone was seen. In eight joints of seven patients, additional surgical procedures were applied later.

Acetabular edge resection alone might resulted in the lateral-proximal displacement of the femoral head and to acquire good result in the long term, some additional procedure should be considered. However, in one case of this series showed good roof osteophyte formation after arthroscopic arthroplasty with improved JOA score. This might be a result of improved blood supply at the edge of acetablum. We believe that arthroscopic arthroplasty for advanced osteoarthritis in combination with other procedures may avoid total hip arthroplasty.

Introduction: It is not uncommon situation, in a hip fracture patient treated with dynamic hip screw(DHS) system, that the hip arthroplasty should be done after removal of DHS. However multiple screw holes and postplating osteopenia under the barrel plate will be created in the proximal femur resulting adverse mechanical effects.

Purpose: The authors analysed the micromotion of femoral stem and the stress concentration of proximal femur in hip replacement performed after removal of DHS using finite element analysis.

Methods: For simulation of femoral cortical defects after removal of 4-holed DHS system, four Φ4.5 mm cortical screw holes on medial and lateral cortices of the femur and one Φ12mm lag screw. One 20mmx90mm weakened cortical bone area on lateral cortex was made for simulation of the postplating osteopenia created under the barrel plate. After meshing with eight node linear hexahedron, nonlinear contact analysis was done using ABAQUS 5.8 package system. For the postplating osteopenia we decreased the bony strength of cortical bone up to 20%.

Results: In one leg stance, the maximal micromotions at metal to bone interface were around 150& #13211; (142.3-160.6& #13211;) even in the osteoporotic femur. However, in stair climbing, it increased over 150& #13211; (170.1-191.1& #13211;) even in the non-osteoporotic intact femur. The maximal micromotions were 170.1& #13211; in intact non-osteoporotic femur and 191.1& #13211; in osteoporotic DHS removed femur in a stair climbing. The pattern of stress distribution on the surface of the femur was changed showing distal transfer of the point with maximal stress from the proximal medial area to the stem tip area. The maximal stress increased up to 89% at the lag screw hole.

Conclusion: This study suggests that the femoral stem for primary cementless hip replacement could be used in the DHS removed femur regardless of bone quality, if it is long enough to pass the screw holes and also if the post-operative rehabilitation is strictly controlled.

Introduction: Recently, highly cross-linked polyethylene has been highlighted in THAs, which is thought to reduce wear. However, little is known about an accurate nature of cross-linked polyethylene particles and long term wear in vivo. One of the authors implanted all polyethylene cups irradiated by 100 Mrad in 1970’s. Recently, we performed two revisions with this cup. In the present study, we extracted polyethylene particles and analyzed them.

Methods: Case1 was revised for a stem fracture and ace-tabular loosening at 25 years postoperatively and case2 for acetabular loosening at 27 years postoperatively. There was no osteolysis on X rays. We extracted polyethylene particles using a tiussue digestion and iamge analysis using computed iamge analyzer developed by Cambell.

Results: Equivalent circle diameter (ECD) was 0.73mm, roundness was 0.69, aspect ratio (AR) was 1.4 and number of particles was 6.0x108/g wet tissue in case1. ECD was 0.57mm, roundness was 0.62, AR was 1.54 and number of particles was 5.8x108/g in case2. SEM showed that granule or globular shapes were abundant and fibril shapes were rare.

Discussion and conclusion: Cross-linked polyethylene particles were less, a little smaller and much rounder in compared with our previous result of conventional polyethylene particles in peri-implant tissue after more than 25 years postoperatively in vivo.

Polyethylene wear is the most important risk factor affecting the durability of total knee arthroplasty. We developed a new method of measuring wear of the tibial polyethylene insert in total knee arthroplasty (TKA) on standard standing radiographs.

Methods: We developed a new method of measuring the shortest distance between the femoral component and the tibial metal tray taking its 3-D position into consideration. The accuracy of the method was examined in 3 conditions. An in vitro examintion measured the thickness of the polyethylene on radiographs of a new PFC prosthesis set on a table. The radiographs were taken from various directions. An in vivo examination measured the polyethylene thickness on patient discharge radiographs of 78 knees. These measurements were compared with known thicknesses of the used inserts. In the third study, wear of the tibial polyethylene insert was measured retrospectively in a series of 84 PFC TKAs with follow-up of 2 to 10 years (6.6 years on average).

Results: The average measurement error was 0.05 mm (SD 0.09 mm) in the in vitro study and 0.14 mm (SD 0.17 mm) in the in vivo study using discharge radiographs. In the series of 84 PFC TKAs, impending failure occurred in 7 knees, 4 of which were revised. Radiographically measured wear of the tibial insert was significantly greater in these failed TKAs than in the other TKAs. The radiographic measurements were well correlated with 3-D measurements of 4 retrieved inserts.

Discussion: Although the radiographic measurement of the tibial insert in TKA was less accurate than that of the socket in THA, it is useful enough to identify TKAs at risk of failure. When the radiographic wear exceeded 1mm, there was a significantly increased probability of impending failure or need for revision.

Introduction: Recent studies showed that the position of the center of rotation and the prosthetic neck may infl uence implant fixation in hip arthroplasty. The purpose of this study is to evaluate the use of modular necks and their limits to restore hip geometry after the arthroplasty.

Methods: The study radiographically evaluates 117 cases of unilateral hip arthroplasty using a modular neck / head concept (Wright Medical). The analysis evaluated on a weight-bearing frontal pelvis view: center of rotation, horizontal abductor ratio, and vertical abductor index, comparatively to the controlateral hip using the student’t test. On the computerized templates of the association effectively used in each case was measured: neck length, lever arm and neck anteversion.

Results: In craniopodal the center of rotation averaged 0.19 in women and 0.23 in men. In mediolateral it averaged 0.26 in women and 0.32 in men. The mean horizontal abductor ratio was 0.65 in women and 0.70 in men. The mean vertical abductor index was 6:..4° in women and 6.5° in men. The mean neck length was 55.2 mm, the mean lever arm 39.3 mm, and the 15° ante or retroverted neck was noted in 10 %.

Discussion and conclusion: Restoration of the center of rotation was more accurate in mediolateral than in craniopodal, with a higher location as previously noted in the litterature. Abductor function was correctly restored excepted for the vertical index in women, probably due to the large variations of pelvis width. The limits of modular necks are large hip dysmorphy where neck length averages 60 mm, lever arm 45 mm and neck anteversion requires 30° of correction.

Introduction: Minimally invasive surgery (MIS) has recently been proposed for unicompartmental arthroplasty to allow quick function recovery. The purpose of this study is to evaluate retrospectively the indications in which this technique would have been possible and successful.

Methods: The requirements for the minimal invasive technique are: a pre-operative flexion of 100° and a lesion limited to one compartment of the knee. The preoperative status, operative findings and clinical outcome of 160 cases of unicompartmental knee arthroplasty (MG, Zimmer) were analyzed to determine whether the criteria for MIS would have been possible.

Results: Preoperatively 12 knees had a flexion less than 100°. Postoperatively four of them had a limited flexion ranging from 90° to 100°. In 53 knees (33 %), peripheral osteophytes were removed on the opposite tibiofemoral joint. None of them were revised for progression of osteoarthritis. In 33 knees (21 %) a patelloplasty was associated to the procedure for peripheral osteophytes. Two of them were revised at 12 and 20 months for osteoarthritis progression.

Discussion: Removal of peripheral osteophytes can be successfully associated to the unicompartmental procedure when using a conventional surgical approach. In 96 of the 160 knees (60 %) MIS was not recommended either for limited preoperative flexion or for peripheral osteophytes. In 2 knees unicompartmental arthroplasty itself was not the correct indication and total knee arthroplasty would have been the right solution. Finally, in 62 of the 160 knees (39 %) unicompartmental arthroplasty using MIS was indicated. In conclusion unicompartmental knee arthroplasty may be either performed by conventional or minimal approach based on the preoperative clinical and radiological evaluation.

The traditional stem in cement-less total hip replacement was designed as a straight stem. This design was chosen to compensate for lack of initial stability provided by cement. Specifically the box shape of the implant achieved rotational stability and the wedge shape promised proximal press fit. Therefore also the first robot-assisted surgeries were performed using straight stems.

Primarily those surgeons using the antero-lateral approach soon felt limitations of the use of straight stems during robot-assisted surgery. The reamer, in order to guarantee a straight positioning of the implant, used a straight approach to the proximal femur, thereby damaging the insertion site of the gluteus muscle in some cases. This then led to persisting muscular deficit with a consecutive positive Trendelenburg sign.

Surgeons began to monitor during computer–assisted planning not only the final position, but also the cutting path, which was – as requested by the surgeons – displayed on the screen. At the same time anatomic stems became available for computer-assisted planning and surgery. With the introduction of anatomic stems also oblique cutting became available, thus avoiding compromising the greater Trochanter.

Clinical results of anatomic stems in robot-assisted surgery seem to be satisfactory. Although most users allow immediate weight bearing, no loosening or visible subsidence was reported. Cadaver studies and animal experiments suggest that exactness of robot-assisted preparation with the resulting close fit of the implant – no press fit though – provide sufficient stability to allow for anatomic designed stems in cement-less procedures.

Impaction allografting is one of the techniques for reconstruction of femur during revision total hip arthroplasties. The initial stability of the stem fixed with impacted morsellized allogtafts and cement depends on multiple factors. The aim of this study was to investigate the stability of stem in reference to the size of bone chips, femoral bone defect and implant design.

Morsellized grafts of human femoral heads were prepared using a reciprocating type bone mill or a rotating type bone mill. Femoral bone defect was created at proximal medial cortex. Two types of polished stem were tested; CPT stem and VerSys CT stem (Zimmer Inc.). The cross section of the stem was relatively rectangular in CPT stem, while round in VerSys CT stem. Morsellized grafts were impacted into an over-reamed plastic bone and the stem was fixed with PMMA bone cement. Cyclic compression test and torsional test were performed using an Instron type machanical tester. Bone chips prepared by a reciprocating type bone mill contained large chips with broad size distribution, which represented high stiffness in compression test and high maximum torque in torsional test. Femoral bone defect and implant geometry did not affect the axial stability of stem, while large bone defect and round shape stem showed significantly lower maximum torque.

These results indicated that the size of bone chips, femoral bone defect and implant geometry affected the initial stability of the stem. Impaction grafting seems to be a technically demanding procedure, however several factors can be controlled to obtain secure implant stability.

This paper outlines and defines a research, which was conducted in order to gauge the efficiency of the Elective Orthopaedic Assessment Clinic in the Department of Orthopaedics, Kilcreene Orthopaedic Hospital, Kilkenny, Ireland. The study was conducted in the year 1999. During this year, 380 patients were seen in the clinic. Of these, 328 patients were on the waiting list for joint replacement and 52 were on the waiting list for other elective procedure. In the process of the study it was observed that 204 patients were found fit on their first preassesment visit. Of all the 328 patients on the waiting list, 48 of those who were awaiting joint replacement were found to have dental caries or infected gums and 28 were diagnosed with some minor infective foci elsewhere in the body. However as according to procedure the patients that did not meet the preassessment criteria due to infection, but were pronounced fit for an operation had to wait for the infection to settle before they could be rescheduled for surgery.

The study in question has proved that the clinic acts as an intermediary between the patients and the operation theatre, by determining patient’s fitness for surgery and appropriately placing them on the corresponding waiting lists. This fact is of primary importance as it aids in preventing possible and sometimes last minute cancellations, thereby attesting to the effectives and efficiency of the clinic. The clinics efficiency can also be measured by the fact that it has initiated a number of improvements, such as the introduction of a checklist card for patients on the waiting list for joint replacements. This checklist includes dental health, and also arranges for patients to be examined by their general practioners and dentists before the preassesment checkup.

Successful outcome in TKA is influenced by the accuracy of the bone cuts, the reconstruction of the anatomical axes,implant design geometry and the active and passive soft tissue structures surrounding the articulation. They determine stability,range of motion and interface stress of the replaced knee joint and of course the clinical result. Since August 2000 we use regukarly the GALILEO-CAS and GALILEO-NAV System in TKA with the TC-PLUS(TM) Solution Knee.

Method: For preoperative planning there is no need of any CT-Scan, neither of the knee,nor of the hip. We need a single-leg-stand-up a-p and m-l X-ray to determine the the mechanical axis and Alpha-angle. Starting the navigated operation 20 measurements are taken to determine the rotational center of the hip. The several anatomical points are measured to construct a virtual model of the operated knee. After measurement the GALILEO-System proposes size and position of the prosthesis. After confirmation of these parameters the motor driven cutting blocks are automatically positioned to produce reliable bone cuttings. Step by step the femoral and tibial cuts can be performed under navigated computer assistance. Nevertheless all the time, the surgeon has the opportunity to manually overwrite the recommended position. At the end of the implantation we can test the ligamentous stability of the joint using Computer Assisted Surgery (CAS)system.

Evaluation: For evaluation of the clinical and biomechanical outcome of CAS, we started a prospective randomized study to compare it with the conventional operated TKAs. From Sept.2000 to June 2001 we performed 200 TKAs with the TC-PLUS(TM)Solution Knee. 100 of them were operated on conventionally; for the remainer we used CAS. The outcome was assessed according to HSS-Score and Insall-Score, pre op,post op 12 days,12 weeks and 6 months.

First results: First trends show a higher reliability of bone cuts in the CAS-Group, better restitution of anatomical axes, an improvement of the ROM 6 months post op and a higher clinical score.

Further evaluation of the mid and long term results are necessary to evaluate the effectiveness of Computer Assisted Surgery in Total Knee replacement.

Introduction The first ceramic knee implant in a human patient was used by Dr. G. Langer of the Orthopaedic Clinic at the University of Jena, Germany in 1972. In 1980, Drs. Oonishi and Hasegave began using a alumina femoral component on a polyethylene tibial component. These early attempts all involve the search for solutions to the wear and degradation problems. The application of ceramics was limited by:

polyethylene wear and degradation

Excellent Scratch resistance AMC Ceramics is much harder than most surgical instruments. In comparison, metal components are easily scratched and damaged during surgery with the consequence of increasing wear.

Surface quality: Surface quality of the articulation surfaces components made from AMC Ceramics provide excellent articulation surfaces.

Low Friction: Knee Components made of AMC Ceramics show a low coefficient of friction. The resulting frictional forces on the prostheses are lower and offer the option for a reduction of aseptic loosening.

Low Allergic Potential: Ceramics are generally not considered as elicitors of allergic reactions. Hypersensitive reactions – especially to nickel – in total joint replacement are discussed as one possible reason for postoperative syndromes.

Surface Lubrication: AMC is a material with a very good surface lubrication capability. A low wetting angle is exhibited by the material.

Conclusion: Knee implants have become an area of great interest in the past years. For more than 10 years ceramic femoral components are used in Japan. Published follow-up data in scientifically journals are promising. Leading orthopaedic surgeons are interested in this option today to reduce the risk of pitting and delamination of Polyethylene. Material improvements are required for young active patients and nickel sensitive patients.

The novel AMC Ceramic offers a solution to minimise the allergic and wear related problems of knee implants. New concepts on the basis of hard on hard combination are technically already realised. The use of knee endoprosthesis with ceramic on ceramic combination is an option for ”zero” wear bearings in the knee.

The first Ceramic knee implant in a human patient was used by Dr. G. Langer of the Orthopedic Clinic at the University of Jena, Germany in 1972 [1]. In 1980, Drs. Oonishi and Hasegave began using an Alumina femoral component on a polyethylene tibial component [2]. These early attempts all involve the search for solutions to the wear and degradation problems. The application of ceramics was limited by the demand of thin components. In the present feasibility study the in vitro wear behavior of a knee concept with a novel Alumina Matrix Composite (AMC) Ceramic was examined [3,4].

The wear behaviour of the Ceramic components for the knee system were tested in accordance to ISO/WD 14243-3 for 5*106 cycles. Six samples were tested. The lubricant was calf serum diluted with deionized water. All tests have been performed with components made of the novel AMC Ceramic. The wear test performed showed an average gravimetric wear rate below 1 mg/1*106 cycles on each of the six components. A change of geometry was not measurable after 5 million cycles. No significant change of the surface structure was detectable with a conventional surface tracer. SEM and AFM pictures show traces of ultra mild abrasive wear at the surface.

The performed investigation on the novel knee concept shows the following potential benefits for a Ceramic knee bearing:

approx. 500 times lower volumetric wear

The novel AMC Ceramic offers a solution to minimize the allergic and wear related problems of knee implants. New concepts on the basis of hard on hard combination are to be realized. The use of knee endoprosthesis with Ceramic on Ceramic combination is an option for ”zero” wear bearings in the knee. These first results motivate to start further R& D on Ceramic on Ceramic bearings for total knee implants.

Introduction: Understanding the in vivo motions of human joints has become increasingly important. Researchers have used in vitro (cadavers), non-invasive (gait labs), and in vivo (RSA, fluoroscopy) approaches to assess human knee motion. The objective of this study was to use fluoroscopy and computer tomography (CT) to accurately determine the 3D, in vivo, weight-bearing kinematics of normal knees.

Methods: Five normal knees clinically assessed as having no pain or ligamentous laxity were analyzed. Using CT scanning, slices were obtained six inches proximal to the joint line on the femur and six inches of the proximal tibia. Three-dimensional CAD models of each subject’s femur, tibia and patella were recreated from the 3D bone density data. Each subject was then asked to perform five weight-bearing activities while under fluoroscopic surveillance: (1) deep knee bend, (2) normal gait, (3) chair rise, (4) chair sit, and (5) stair descent. The computer-generated 3D models of each subject’s femur and tibiaon (> 1

Aim: We studied the effect of filling the femoral entrance hole in relation to the total blood loss during and after the procedure of Total knee arthroplasty in 72 patients performed between 1997 and 1999 performed in our unit.

Materials and methods: This was a retrospective review and the patients were be broadly classified into three groups, the first (Group A) who had the entrance holes left unblocked (n= 21), the second (Group B) had the holes filled with bone cement (n= 21) and the third (Group C) with the holes filled with bone (n= 26).

Results: The average Blood loss for group A was 1019, group B was 11077 and group C was 1162. The Average Blood transfusion for group A was 0.70 units, group B was 0.40 units and group C was 0.30 units.

Conclusions: We found no significant difference in the Total Blood loss between the three groups and conclude that filling the entrance holes does not effectively reduce the Total Blood Loss in Total Knee arthroplasty and that there is no advantage to be gained in respect of the total transfusion needed for these patients.

This study assesses the clinical performance of the Souter-Strathclyde elbow arthroplasty with a standardised index and long-term survivorship analysis.

We undertook assessment of 68 primary Souter-Strathclyde total elbow replacements. Of 53 patients assessed with pre-operative Souter-Strathclyde charts, nine died and one was lost to follow-up, 43 had radiographic and telephone review, and 38 (88%) had clinical examination according to the Mayo Elbow Performance Index.

Survival of the 43 elbows was to a mean of 72 months (range 8 to 187). A cohort of 25 elbows available for review with > 5-year follow up had improvement in pain, motion, stability and function. Eight of ten elbows in deceased patients had satisfactory scores at the last assessment. Ulnar neuropraxia occurred in eight elbows (12%), persistent sensory deficit in two (3%) and motor deficit in one. Two triceps abscesses required local skin flap cover. Revision was undertaken in 14 elbows (20%) for instability (6) bony injury (3), loosening (3) and intraoperative problems (2).

The survivorship at 13 years was 74% with 62 (91%) of all elbows achieving a satisfactory Mayo score.

Introduction: The goal of this study was to determine the difference between weight-bearing and non weight-bearing range of motion (ROM) for Japanese subjects having either a fixed or mobile bearing TKA with either a resurfaced (RP) or unresurfaced (UP) patella.

Methods: Forty subjects were evaluated using video fluoroscopy. Twenty subjects had a fixed bearing posterior cruciate retaining (PCR) TKA (10 RP, 10 UP) and twenty subjects had a mobile bearing (MB) TKA (10 RP, 10 UP). Under weight-bearing conditions, each subject performed successive deep knee bends to maximum flexion. Then, under passive, non weight-bearing conditions the subjects stood on one leg and passively flexed their knee to maximum flexion. Each trial was recorded and analyzed digitally. The angle between the femoral and tibial longitudinal axes was subtracted from 180o to obtain the amount of flexion.A single surgeon control was used. The average age of the subjects was 66.4, 78.1, 70.3, and 71.1 for subjects having PCR RP, PCR UP, MB RP, and MB UP, respectively. All total knee subjects were judged excellent clinically with HSS scores > 90 points. None complained of pain during testing.

Results: The preoperative ROM for the implanted knee groups was 115, 122, 110, and 120 degrees for subjects having a PCR RP, PCR UP, MB RP, and MB UP, respectively. The average passive ROM was 106 (90–131) and 108 (72–128) degrees for subjects having a PCR RP and PCR UP, respectively. Subjects having a MB TKA experienced greater passive ROM, 120 degrees for both the MB RP (105–136o) and MB UP (105–167o). Under weight-bearing conditions, ROM decreased for all groups, with the average ROM of 101 (90–125), 108 (86–128), 109 (92–134), and 114 (94–142) degrees for subjects having a PCR RP, PCR UP, MB RP, and MB UP, respectively. The greatest amount of ROM occurred for a subject having a MB UP, 167o during passive ROM and 142o during a weight-bearing ROM.

Discussion: Subjects in this study having a MB TKA experienced greater ROM for all of the compared four parameters. Subjects having a MB RP experienced greater passive (120 vs. 106) and weight-bearing (109 vs. 101) ROM compared to the PCR RP group. Similarly, subjects having a MB UP experienced greater passive (120 vs. 108) and weight-bearing (114 vs. 108) ROM compared to the PCR UP group. Interestingly, subjects having an UP TKA experienced greater ROM compared to subjects having a RP TKA. The results from this study may suggest that a mobile bearing TKA may lead to greater ROM for the Japanese populations, where achieving deep flexion is essential for normal daily activities.

Introduction: Recently, many different mobile bearing TKA designs are being implanted throughout the world. Also,fluoroscopy has been used to evaluate variousTKA under in vivo conditions to determine the kinematics. The objective of this study was to utilize a randomized prospective study to evaluate the kinematic patterns, for Japanese subjects implanted with two different mobile bearing TKA.

Methods: Twenty Japanese subjects were entered into a prospective study. Ten subjects were implanted with a mobile bearing TKA, which is free to rotate around the longitudinal axis of the tibia (MB1). The other ten subjects were implanted with a mobile bearing TKA that allows for unrestricted translation and rotation (MB2). Femorotibial contact positions were analyzed using video fluoroscopy. Each subject, while under fluoroscopic surveillance, was asked to perform gait. Video images were downloaded to a workstation computer and analyzed at varying degrees of gait stance. Femorotibial contact paths for the medial and lateral condyles were then determined using a computer automated model-fitting technique. Femorotibial contact anterior to the tibial midline in the sagittal plane was denoted as positive and contact posterior was denoted as negative.

Results: During gait, on average, subjects implanted with MB1 experienced minimal A/P translation of either condyle. Also, all subjects having MB1 experienced similar motion patterns throughout the stance phase of gait. Axial rotation was evident in these subjects, as one condyle would move in the anterior direction, a similar amount to the other condyle moving posterior. On average, subjects implanted with MB2 experienced both translation and rotation. The amount of translation for subjects with MB2 was greater than subjects with MB1. The kinematic patterns for subjects having MB2 were also more variable than subjects having MB1. Axial rotation was also evident for subjects having MB1.

Discussion: This study has shown that the kinematic patterns for subjects having two different mobile bearing TKA designs differed considerably. Subjects implanted with a mobile bearing TKA that only allows for free rotation, experienced minimal A/P motion and significant axial rotation (MB1). Subjects implanted with a mobile bearing TKA that allows for free translation and rotation did experience both types of motions (MB2). There was minimal variability in the kinematic patterns for subjects implanted with MB1, while subjects implanted with MB2 experienced more variable kinematic patterns.

Background: A common problem following total joint arthroplasty is urinary retention, which often necessitates catheterisation in the postoperative period. Most of these catheterisations are done as an emergency in the ward where the sterility is less than optimal.

Methods : A retrospective study of the incidence of emergency urinary catheterisation in 300 male patients who underwent total joint Arthroplasty under spinal anaesthesia over an eighteen-month period is presented. The patients were divided into three groups according to their age Group 1 (50 to 65 yrs), Group 2 (65 to 70 yrs) and Group 3 (70 + yrs).

Results: The incidence of catheterisation for acute urinary retention in Group 1 was 20%, Group 2 – 65% and Group 3 –69%.

Discussion: Urinary stasis predisposes to infection. The direct relationship between urinary catheterisation and infections in total joint Arthroplasty is already well documented. The potential for infection is compounded if the procedure is carried out in the unsterile ward environment. This study shows that the incidence of emergency catheterisation in patients aged 65 or above was high (average 67%) .

Conclusion: We conclude that these patients in groups 2 and 3 should be catheterised electively in the optimal sterile environment of the operating theatre. Catheterization should be performed after the patient has had the anaesthetic and the prophylactic intravenous antibiotic has been administered. The potential occurrence of joint and urinary tract infection is reduced and consequently patient morbidity is lessened.

This study addresses four questions:

Does laminar flow exist in our operating theatres?

Do perioperative warming blankets affect laminar flow?

Do perioperative warming blankets cause displacement of particles into a wound perioperatively?

Do conventional theatres have adequate airflow?

It has been widely recognised that laminar flow theatres decrease colony forming units in operating theatres and thus decrease the risk of infection in arthroplasty surgery. It is also accepted that perioperative warming blankets improve patient haemodynamic stability and may reduce the risk of wound infection.

However, there has been great debate as to whether these perioperative warming blankets cause disruption of laminar flow and excess displacement of dust into a wound, and thus increase the risk of infection of total joint arthroplasty surgery. Using digital video imaging and airflow measurement techniques as used in formula 1 racing design, this independent study reveals that the Bair Hugger system has no effect on laminar flow or paticle displacement. It also shows that factors out of the surgeon’s control disrupt laminar flow and that general theatre design may be inherently flawed. This would seriously affect the risk of infection.

Background: Aseptic loosening of total joint arthroplasty is characterised by osteolysis, which is caused by osteoclasts and macrophages. Collagen cross link molecules N Telopeptides (NTx) are released during osteolysis and represents a highly specific marker for bone resorption. NTx could be a potential marker in the laboratory investigation of aseptic loosening with the advantage of being cheaper and easier to perform compared to present established markers. The aim of this study was to show that NTx generated during osteolysis by cells extracted from human interface membranes of aseptically loosened hips correlates with the established radiolabelled 45Ca bone resorption model.

Methods: Cells from human interface membranes of aseptic loosened hip joints were cultured with dead radiolabelled (45Ca) mice calvaria discs and in the control culture no cells were added to the culture system. Calvaria discs used in each experiment comparison were from the same parietal bone. The supernatant culture medium were extracted on day 3,7,10 & 14 and assayed for NTx and by scintillation counting. On day 14 the remaining culture medium and cells were assayed by scintillation counting and the total remaining 45Ca in the bone were measured.

Results: All results were expressed as the ratio of bone exposed to cells (BC)/bone only (B). Supernatant samples for 45Ca and NTx showed a rise in BC/B ratio with time. These were 0.83, 0.88, 0.97 & 1.08 (p=0.0001) and 1.06, 1.21, 1.41 & 1.40 (p = 0.03) respectively. In the bottom sampling for 45Ca the mean ratio of BC/B was 1.8 (p=0.0001) and the mean BC/B ratio for the remaining 45Ca in the bone at the end of the culture was 0.81 (p=0.0007). There was a strong correlation between 45Ca and NTx (r = 0.88).

Discussion: The initial drop of calcium levels can be explained by calcium uptake by the cells. We believe this is the first time human interface membrane cells have been shown to release NTx during osteolysis in an in vitro model. Replacing 45Ca radilabelled bone with NTx as a marker represents an important step towards simplifying and reducing the cost of an in in vitro model of particle induced osteolysis.

Introduction: Previously, in vivo kinematic studies have determined the in vivo kinematics of the femur relative to the metal base-plate. These kinematic studies have reported posterior femoral rollback in posterior stabilized (PS) TKA designs, but the actual time of cam/post engagement was not determined. The objective of this present study was to determine, under in vivo conditions, the time of cam/post engagement and the kinematics of the femur relative to the polyethylene insert.

Methods: Femorotibial contact positions for twenty subjects having a PS TKA, implanted by two single surgeons, were analyzed using video fluoroscopy. Ten subjects were implanted with a PS TKA that is designed for early cam/post engagement (PSE) and ten subjects with a PS TKA designed for later cam/post engagement (PSL). Each subject, while under fluoroscopic surveillance, performed a weight-bearing deep knee bend to maximum flexion. Video images were downloaded to a workstation computer and analyzed at ten-degree increments of knee flexion. Femorotibial contact paths for the medial and lateral condyles, axial rotation and condylar lift-off were then determined using a computer automated model-fitting technique.

Results: Subjects implanted with the PSE TKA experienced, on average, the cam engaging the post at 48° (10 to 80°). Subjects having the PSL TKA experienced more consistent results and did experience engagement in deep flexion (Average 75°). Subjects having the PSE TKA experienced, on average, −5.5 mm (1.5 to −9.3) of posterior femoral rollback (PFR), while subjects having the PSL TKA experienced only −2.6 mm (8.5 to −9.0) of PFR. Subjects having the PSE TKA experienced more normal axial rotation patterns. Nine subjects having the PSE TKA experienced condylar lift-off (maximum = 1.9 mm), while only 4/10 having the PSL TKA experienced condylar lift-off (maximum = 2.7 mm).

Discussion: This is the first study to determine the in vivo contact position of the cam/post mechanism. Subjects having a PSE TKA experienced earlier cam/post engagement than subjects having the PSL TKA. Some subjects did not experience any cam/post engagement throughout knee flexion. Subjects having the PSE TKA experienced more PFR and better axial rotation patterns, but subjects having a PSL TKA experienced lesser incidence of condylar lift-off. Results from this study suggest that there may be an advantage to early cam/post engagement, which leads to more normal axial rotation patterns caused by the medial condyle moving in the anterior direction as the lateral condyle rolls in the posterior direction.

Total knee arthroplasty (TKA) after proximal tibial valgus osteotomy is thought to be technical demanded and its outcome is not as sufficient as primary TKA. Purpose of this study is to identify particular surgical procedures and outcome of TKA after proximal tibial valgus osteotomy in the different type of osteotomies. Fourteen TKA after proximal tibial valgus osteotomies were underwent for 13 patients with osteoarthritis. Average age at surgery was 72 years old. The mean duration from proximal tibial valgus ostetomy to TKA was 9 years and 10 months and the mean follow up period after TKA was three years and nine months. Four closed wedged osteotomies, five modified Levy’s reversed V shaped osteotomies and five domed osteotomies were underwent before TKA. The V-Y lengthening of quadriceps tendon or osteotomy of the tibial tubercle was necessary for each one knee. Both knee had patella infera due to previous osteotomies of tibial tubercle for patello- femoral osteoarthritis. 11 lateral releases including release of lateral collateral ligament and two lengthening of iliotbial tract were needed to achieve sufficient ligament balance. The stems of tibial components could be placed almost centrally especially in knees, which had reversed V shaped oseteotomies and laterally in knees, which had domed or closed wedged osteotomies. Clinical results evaluated by Japan Orthopedic Association score had improved from 53 points before TKA to 84 points after TKA. This study suggests that 1) approach is difficult in the knee, which had previous osteotomy of tibial tubercle, 2) lateral release including lateral collateral ligament and iliotibial tract is necessary to achieve sufficient ligament balance, 3) the stem of tibial component might be placed laterally in knees, which had previous domed oseteotomy or closed wedged osteotomy, 4) outcome of TKA after proximal valgus osteotomy is as good as primary TKA.

Introduction: The purpose of this study is to evaluate the clinical and radiogra phic outcome of patients with secondary osteoarthritis of the hip, who underwent custom-made cementless THA.

Methods: Between January 1994 and June 1997, 98 prim ary cementless custom-made THA’s were performed in 76 patients with secondary osteoarthritis and reviewed at mean 6 years follow-up (range: 4 – 7.5 years). Nine patients had a previous femoral osteotomy. There were 69 females and seven males. The mean age at operation was 54 years (40 – 73 years). Custom-made, 125 mm-long, titanium femoral components with blasted surface were fabricated based on the computerized tomography.

Results: The mean Harris Hip Score improved from 43 to 95 points. 97 patients (99%) had more than 80 points for total score, and 2 patients (2%) had thigh pain at the latest follow-up. Radiographically, 86 hips (87%) showed obviously extensive bone ongrowth onto the middle part of the stem while 8 hips (9%) showed stable fibrous fixation. Four hips (4%) were unstable: more than 2 mm subsidence in 2 hips and more than 2 degrees varus migration in 2 hips. Of these 4 hips, 2 had intraoperative cracks of the poximal femur and 2 had varus positioning of the stem.

Discussion and conclusion: Cementless THA has been advocated to enhance fit and fill of variable hip geometry. However, some clinical studies failed to show that custom implants significantly improve clinical success or implant longevity because their surface finish was not optimal. Custom-made titanium femoral components with blasted surface showed good clinical results. The reasons for radiolographical failures were because of intraoperative technical errors and these might be derived from 125 mm-long stem with maximum canal fill. A shorter stem may be an option because it may improve the feasibility of stem insertion and the distal fill.

Sciatic nerve palsy is a troublesome complication of total hip arthroplasty, and may be caused by direct injury or over-traction at the time of the operation. We investigated the effects of over-traction on the blood flow of the sciatic nerve by placing the hip and knee joints in various positions. Twenty hip joints of 10 adult dogs were examined. Using a posterior surgical approach, the sciatic nerve was exposed and a site 1 cm distal to the greater trochanter was selected for blood-flow measurement. The blood-flow was measured using a Laser Doppler Flowmetry, with the hip and knee joints at various positions. Blood flow decreased as flexion angle increased and internal rotation angle of the hip joint increased, and decreased with as flexion angle of the knee joint decreased.

When we positioned the hip joint at 160 degrees of flexion and 30 degrees of internal rotation and the knee joint at 0 degrees of flexion, we found that the mean blood-flow decreased by 69% from the value measured when the hip joint was at 90 degrees of flexion and the knee joint was 90 degrees of flexion. When knee flexion was 90 degrees there was no significant difference in average blood flow between 30 degrees of internal rotation of the hip and 0 degrees internal rotation. When knee flexion was 0 degrees there was a significant difference in average blood flow between 30 degrees of internal rotation of the hip and 0 degrees of internal rotation.

Our results suggest that surgeons should pay attention to extension of the knee and the flexion and internal rotation positions of the hip to prevent sciatic nerve palsy as a complication of total hip arthroplasty

A prospective randomized study was performed to evaluate the role of cold therapy in the postoperative treatment of total hip arthroplasty (THA). Forty consecutive patients underwent primary total hip arthroplasty for osteoarthritis. All components were not cemented. The patients were randomized: 20 were fitted with a cold therapy device for four days, and 20 were not. They were evaluated in terms of blood loss, creatine phosphokinase (CPK) level, C-reactive protein (CRP) level, and pain relief. No significant difference was found in the amount of postoperative wound drainage between the two groups of patients. The use of cold compressive dressing after THA was not associated with an increase in CPK and CRP level.

The pain score in the postoperative period of THA was significantly lower in the cold therapy group than in the control group. The results of this study support the potential benefit in pain reduction by use of the cold compressive device in the postoperative recovery of patients undergoing THA.

Introduction: The aims of this paper are to compare the results of Measuring migration rates on radiographs manually and by computer assisted analysis of digitised images.

Methods: Standardised anteroposterior standing hip radiographs taken post operatively and then yearly following hip replacement were used. The radiographs were then scanned at 150 dpi (gray scale) and saved as tif files. The migration was measured manually by drawing a line along the long axis of the femoral component connecting the distal tip, to the notch, which is used to impact the stem proximally. This gives us the length of the hip replacement and an axis along which migration can be measured. The tip of the greater trochanter was selected as a bony landmark. On the plain radiographs two sets of readings were made by one observer. The digitized images were then analysed in the same way using a software package (designed in-house at the University of Dundee). Two sets of readings were performed by observer one and a second set by an independent observer. Statistics: Inter and Intra observer rates were calculated using a paired sample t test.

Results: For the manual readings intra observer mean difference was 0.53mm (Cl 0.31–0.74mm). Comparing manual vs computer readings for observer one there was a correlation of 0.89. For the computer readings intra observer mean difference was 0.36mm (CI 0.64–0.8mm) and inter observer mean difference 0.16 mm, both non-significant differences. This evidence shows that the readings made manually and by computer were not significantly different and that there was no significant inter and intra observer variation. The advantage of computer storage and reading being the faster analysis, the ability to store and access large numbers of radiographs. The disadvantages being the need to scan the radiographs to allow measurement.

The use of prostheses with porous surfaces in cementless total hip arthroplasty now predominates. Beads are popular for use as a porous coating, but their mechanical strength may be insufficient because of displacement of some of the beads from the coating. In this study, we propose a new porous surface, created by making direct holes in the metal surface using a YAG laser. A titanium-alloy (Ti-6Al-4V) rod was used. A Bead-type prosthesis was made by diffusion bonding pure titanium beads to the rod; it was 5 mm in diameter and 35% in porosity. A Laser type was made by directly creating holes in the same rod surface using a YAG laser; it was 5 mm in diameter and 33.7% in porosity. Both implants were evaluated in vivo using the hemitranscortical cylindrical model in two beagle dogs. Four prostheses were implanted into each femur through the lateral cortex, for a total of eight of each type, and remained in place for 12 weeks. Except for the proximal implant, push-out tests were performed to measure the shear strength of fixation of the implants to the cortical bone. For observations of the implant-bone interface, decalcified specimens of the proximal femur were stained with toluidine blue and observed with an optical microscope. The mean push-out strength of the Laser type was approximately 10.2 MPa and that of the Beads type was approximately 10.7 MPa. There was no significant difference in interface push-out strength between the groups. Bone ingrowth into both types was sufficient, however, some specimens of the Beads type demonstrated displacement of some of the beads from the rod surface. This study indicates that a porous surface created with a YAG laser might be useful not only for its shear strength, but also for the strength of the surface itself.

Biodegradable porous scaffolds play an important role in tissue engineering as the temporary templates for transplanted cells to guide the formation of the new organs. The most commonly used porous scaffolds are constructed from two classes of biomaterials. One class consists of synthetic biodegradable polymers such as poly (α-hydroxy acids), poly(glycolic acid), poly(lactic acid), and their copolymer of poly(DL-lactic-co-glycolic acid) (PLGA). The other class consists of naturally derived polymers such as collagen. These biomaterials have their respective advantages and drawbacks. Therefore, hybridization of these biomaterials has been expected to combine their advantages to provide excellent three-dimensional porous biomaterials for tissue engineering. Our group developed one such kind of hybrid biodegradable porous scaffolds by hybridizing synthetic poly (α-hydroxy acids) with collagen. Collagen microsponges were nested in the pores of poly (α-hydroxy acids) sponge to construct the poly (α-hydroxy acids)-collagen hybrid sponge.

Observation by scanning electron microscopy (SEM) showed that microsponges of collagen with interconnected pore structures were formed in the pores of poly (α-hydroxy acids) sponge. The mechanical strength of the hybrid sponge was higher than those of either poly (α-hydroxy acids) or collagen sponges both in dry and wet states. The wettability with water was improved by hybridization with collagen, which facilitated cell seeding in the hybrid sponge. Use of the poly (α-hydroxy acids) sponge as a skeleton facilitated formation of the hybrid sponge into the desired shapes with high mechanical strength, while collagen microsponges contributed good cell interaction and hydrophilicity. One of such kind of hybrids. Additionally, our group developed a hydrostatic pressure bioreactor for chondrocyte culture. And our study showed that hydrostatic pressure (0–3 MPa) had promotional effects on the production of proteoglycan and type II collagen by cultured chondrocytes. Therefore, it would be a promising pathway for reconstructing cartilage-like tissue to culture chondrocytes in this three-dimensional hybrid sponge under physiological hydrostatic pressure.

Introduction: In general a loose-balanced total knee arthroplasty (TKA) are believed to gain good postoperative range of motion (ROM), however, too much laxity is thought to be a cause for persistent pain and catastrophic long-term results.

Materials and methods: We measured the antero-posterior and medio-lateral laxity to evaluate the influence of stability after cruciate-retaining TKA on ROM, pain score in Knee Society score and Functional score at 4–7 years after the operation. Twenty-one knees in 15 patients with an average age of 68 years (range, 58–78) who had a PCL retaining TKA for osteoarthrosis were examined (YS-4, 16 knees; AGC-S, 5 knees). There were 12 women and 3 men. Anteroposterior laxity was examined using a KT 2000 arthrometer at 30-degree knee flexion. Mediolateral laxity was examined at full extension with manual stress x-rays.

Results: Average ROM was 112 degrees (range, 90–140 degrees), antero-posterior laxity was 9.7 mm (range, 2–27 mm) and mediolateral laxity was 10.6 degrees (range, 5–22 degrees). Knee Society pain score was 47 (range, 10–50) and Functional score was 82 (range, 40–100). No significant difference in ROM and clinical scores were noted between the lax and the stable knees. Correlations between ROM and anteroposterior or medio-lateral laxity were not significant (P = 0.55, P = 0.05, respectively; Spearman’s correlation efficient).

Discussion and conclusion: A loose-balanced TKA did not gain good post-operative ROM. No parameters suggested that lax knees got better flexion angle, worse pain score and functional score than stable knees.

Introduction: The aims of this study are:

To report and validate the early migration rates of the collarless polished tapered hip replacement using manual and computer measurements

To report early clinical results of the CPT hip

Patients and methods: 80 patients undergoing primary total hip replacement in a single centre were prospectively recruited into the trial. There were 59 females and 21 males: age range 31–84 years, (mean 68 years sd 9.86). Surgery was performed through an anterolateral approach in all cases. A standard cementing technique using a cement gun and cement restrictor was employed. The patients had standardised anteroposterior standing hip radiographs taken post operatively, then yearly. The migration was measured along the long axis of the femoral component In the anteroposterior plane, using the tip of the greater trochanter as a bony landmark. Measurements were made by two independent observers (specialist registrars). Plain radiographs were measured manually using a ruler and set square and digitised images using a software package designed in-house at Dundee University. Correction for magnification was incorporated. Hip assessments were performed at each review by an independent reviewer.

Results: The mean migration rates and 95% confidence intervals (Cl) and mean Harris pain and Harris hip scores and Std Deviations were:

There was no significant difference between inter or intra observer measurements for hip migration.

This is the first study to date that we are aware of that describes the subsidence rates of the CPT hip which includes validation by inter and intra observer readings.

To evaluate the osseointegration enhancement, a consecutive randomized series of 50 on a total of 483 cementless titanium prostheses were prospectically studied. The features of the stem were the following: tapered, straight, low-profile neck, metaphyseal and hystmic fit, proximal 1/3 hydroxyapatite coated (HA) and titanium porous coated (PC). The acetabular component was hemispherical, titanium porous coated. A zircornia or Co/Cr head (28mm) was used. Female were 53% and average age 65. The general diagnosis was ostheoarthritis, congenital hip dysplasia, fracture, aseptic loosening, osteonecrosis, previous femoral osteotomy, previous pelvic osteotomy. Clinical objective assessment was based on the HHS. A patient oriented evaluation (Womac and SF12) was obtained. Radiological assessment was based on the Engh’s method. The general and prospectical group results have been evaluated.

In all the groups the HHS, Womac and SF12 questionnaires showed a statistically significant improvement in quality of life. Consistent evidence of proximal bone ingrowth were present in 100 % (HA) and 96 % (PC), stable proximal fibrous ingrowth in 4 % (PC). Cortical hypertrophy (50 % zone 3–5), stress shielding (56 % zone 1) and pedestal ( one case) were assessed. Nor osteolysis neither subsidence were identified. No significant general complications such as infections or periprosthetic fractures were observed. The use of HA seems to improve the mechanism of osseointegration and earlier clinical outcomes, even if this difference is not significant. Patient oriented evaluation and radiographic assessments confirmed the reliability of this cementless prosthesis. Less osteolysis could be predicted in the future, according to the reported results of other authors in the HA coated stems.

Bone Loss is the main problem in failed total hip arthroplasties. Revision surgery must be conformed to the degree of the bone loss. Since 1986, 330 cases of failed THA underwent to revision surgery. Different solutions were adopted according to Paprosky femoral defects classification. In type I, a primary cementless stem was implanted (23%). In type II and IIIa, were proximal fixation is still possible to achieve, Mid PCA-Howmedica (5%) and modular S-ROM-J& J revision stems (18%) were implanted. In all the other degree of bone loss (IIIb–IV) cementless distal fixation stems, Long PCA-Howmedica (17 %), Wagner-Sulzer (18 %) and modular (MP-Link, Profemur-Wright) (19 %), were used. Patients were clinically and radiographically evaluated by HHS and according to Engh’s criteria. Best results were observed in Type I group (HHS=90). Long and mid PCA stems presented poor clinical (HHS=60) and radiographical results and required re-revision in 15% of cases. Intermediate results were observed in Wagner prostheses. Modular revision stems showed best results although earlier F-U. (HHS=80). Of these, re-revision surgery was performed in two cases, one of which because of infection and the other one due to severe thigh pain.

Cementless modular stems seem to be the most suitable technique. Distal fixation associated with proximal fill permit to manage the majority of femoral bone defects minimizing bone grafts. The modular stems, allow to conform the design of the components to the bone defects permitting to achieve primary stability (press-fit), restoring the centre of rotation and muscles tension, reducing pain and restoring hip function.

Early micromotion of joint prostheses with respect to the bone can be assessed very accurately by a method called Roentgen Stereophotogrammetric Analysis (RSA); a method that uses two simultaneous X-ray exposures of the joint and has an accuracy of 0.1 mm for translations and 0.3 degree for rotations [1]. In order to reach this accuracy, metallic markers are inserted into the bone and attached to the surface of the prosthesis. These markers can then be identified automatically in the two radiographs [2]. Since the adjustments to the prosthesis are difficult, time-consuming and expensive, RSA has only been applied in a limited number of clinical trials.

In a previous study we have developed a Model-based RSA algorithm, which does not require the attachment of markers to the prosthesis [3]. This algorithm is based on minimisation of the non-overlapping area (NOA) between the automatically detected contour of the prosthesis from the roentgen image, with the virtually projected contour of a three-dimensional model of the prosthesis.

Because the accuracy of this NOA algorithm was not as high as the accuracy of the currently used Marker-based RSA, we have studied alternative algorithms for Model-based RSA. From a simulation study in which we used models of the Interax Total Knee Prosthesis (Stryker-Howmedica) and the G2 Hip Prosthesis (Johnson & John-son), we found that the results of the NOA algorithm can be improved substantially. The newly developed Model-based RSA algorithm is based on minimisation of the mean distance between the points of the actual contour and the virtually projected contour. The simulation study shows that the new algorithm is superior to the NOA-algorithm in situations where part of the contour is occluded, as well as in situations where the contour is distorted by noise. With the new algorithm, the residual position error can be reduced to 0.1 mm. and also the residual orientation error can be reduced to 0.3 degree, making Model-based RSA a future alternative to Marker-based RSA.

Biomechanical alignment of the knee is a major determinant in the outcome of Total Knee Arthroplasty. However, the best method to assess the alignment is yet undecided. Conventional methods use hip to ankle “long” standing x-rays but these suffer from technical difficulties and hence are a potential for error. Short x-rays are considered to have doubtful accuracy.

This study aimed to assess if the “short” AP x-rays could be used to assess the lower limb axis within a range of statistically insignificant and clinically acceptable difference.

The results indicate the readings from the short x-rays were not statistically different from those obtained from the long x-rays in four sets of observations. The largest difference between any two readings was 0.68 degrees. The analysis of data showed that the measurements from the short x-rays could indeed be used to assess the long axis of the lower limb with the provison that there is no gross femoral shaft deformity.

Introduction/purpose: Cementless femoral fixation in TKA varies regarding philosophy of design, materials, and surgical technique. This study evaluates autograft enhancement with AML (porocoated) stems. Impaction autograft (head reamings) enhances cortico-cancellous fit in canals of different geometry, preserves bone, decreases potential for stress shielding and seals the stem from wear particles.

Materials/methods: Clinical/radiologic evaluation of 110 AML prostheses (proximal/extensive porous-coated) with 4- to 11-year (mean 6.9) follow-up was performed. Demographics included 68 females, 42 males, age 34–90 (mean 66). Diagnoses included OA (86), RA (16), other (8). Key surgical points included: 1) stem matching/sizing to proximal cortical contact; 2) head/neck reaming with acetabular graters; 3) autograft delivery (distal-lateral) prior to partial stem insertion and proximal-medial prior to prosthetic seating.

Results: Femoral stem fixation was successful in 98%. Autograft fill was visualized radiographically within the first 6 weeks. Stem fit-fill ratios were .63 proximally and .73 distally, suggesting that most stems were stabilized via cortico-cancellous bone. The 2 fixation failures (1 stem fracture, 1 aseptic loosening) occurred in large males with undersized stems. Radiologic stability was noted in 95%. There were 6 cases of proximal osteolysis secondary to wear without distal extension, and no lucency > 2mm. Mean subsidence was.6mm. There were 10 acetabular failures secondary to wear/loosening and 1 traumatic neck fracture. There were no infections.

Conclusion: The technique of impaction autograft using femoral head reamings is a biological (osteoinductive-osteoconductive), practical, and simple treatment method to accommodate and fill femoral canal voids frequently encountered in THA. Large, stiff stems (with distal fixation) can be avoided with less risk of technical problems and long-term bone loss secondary to stress shielding. The technique can be utilized, with variation, in any current cementless femoral stem.

Introduction: Understanding the forces across the human lower extremity joint is of considerable interest to the clinician. In the past, telemetric hip implants have been used to determine the forces across the hip joint, but the forces at the knee joint remain unvalidated. Recently, video fluoroscopy has been utilized to accurately determine the in vivo kinematics of human joints during various activities. The objective of this study was to predict muscle and joint forces from a mathematical model utilizing fluoroscopy as the input motion data.

Methods: Initially, two subjects (one with a total knee and a second with a total hip arthroplasty) were asked to perform normal gait and a deep knee bend while under fluoroscopic surveillance. A fully automated computer model-fitting algorithm was employed to convert the two dimensional (2D) fluoroscopic videos to 3D, and the in vivo motion of the implanted joint was determined. The kinematic data then served as input to a mathematical model in which the relative motions of the segments and the interaction forces between the foot and the ground were also treated as input data. The predicted forces for the implanted joint, quadriceps muscles and patellar ligament were plotted with respect to time, percent gait cycle and knee flexion angle.

Results: The resultant force at the implanted knee joint ranged from 2.0 to 3.5 times body weight (BS) during gait, depending on walking speed and walking motion. A forward leaning pattern resulted in significantly higher knee joint forces. During a deep knee bend, the knee joint forces could rise as high as 3.5 BW. The resultant forces at the implanted hip joint ranged from 2.0 to 4.0 BW, depending on the activity (greater during deep knee bend), walking speed, walking motion and the incidence of hip separation. The patellofemoral forces were minimal during walking (< 0.5 BW), but increased significantly with greater knee flexion to a maximum of 3.5 BW. The quadriceps muscle and patellar ligament forces were similar during gait (1.0 BW), but the quadriceps force was 40% greater in deep knee flexion.

Discussion: The present study has determined that the predicted hip joint forces are similar to telemetrically derived joint forces at the hip joint. Both knee, hip and muscle forces were greater in deep flexion compared to gait. A sensitivity analysis determined that the model is extremely sensitive to patellar ligament and patella motion. Altering the kinematics of the patella and patellar ligament could increase the knee joint forces by 1.0 BW.

Introduction: Previous in vivo kinematic analyses of the hip joint have determined that femoral head separation from the medial aspect of the acetabular component occurs in metal-on-polyethylene THA. The present study analyzes subjects having either an alumina-on-alumina (AOA),alumina-on-polyethylene (AOP),metal-on-metal (MOM) or metal-on-polyethylene (MOP) THA during gait to determine if the incidence of hip joint separation varies based on articular surface material.

Methods: Forty subjects were analyzed in vivo using video fluoroscopy. Ten subjects had a AOA THA, ten an AOP THA, ten a MOM THA, and ten having a MOP THA. All THA subjects were implanted by two surgeons and were judged clinically successful (Harris hip scores > 90.0). Each subject performed normal gait on a treadmill and an abduction/adduction leg lift maneuver while under fluoroscopic surveillance. The two-dimensional (2D) fluoroscopic videos were converted into 3D using a computer automated model-fitting technique. Each implant was analyzed at varying flexion angles to assess the incidence of hip joint separation.

Results: During gait and the abduction/adduction leg lift, no separation was observed in subjects having an AOA THA or in subjects having a MOM THA. Similar to our previous studies pertaining to subjects having a THA with a polyethylene acetabular insert, all ten subjects having a MOP THA and 6/10 subjects having an AOP THA experienced hip joint separation. The maximum amount of separation was 7.4 mm for a subject having an AOP THA and 3.1 mm for a subject having a MOP THA.

Discussion: This study shows femoral head separation from the medial aspect of the acetabular component can occur in the presence of a polyethylene liner. The femoral head often remains in contact with the liner, hinging superolaterally. Potential detrimental effects resulting from hip joint separation include premature polyethylene wear, component loosening (secondary to impulse loading conditions) and hip instability. Wear may be enhanced due to creation of multidirectional wear vectors or excessive loads due to eccentric femoral head pivoting. The absence of separation observed in AOA and MOM THA designs may be related to increased wettability of these materials and tighter radial tolerances resulting in a cohesive lubrication film. This data may be of value in hip simulation studies to better duplicate wear patterns observed in retrieval analyses and assist in the understanding of the lubrication regime and wear rates in AOA and MOM designs, allowing for the synthesis of prosthetic components that minimize wear and optimize kinematics.

Introduction: In 1970’s, Oonishi et al found out that the polyethylene cross-linked by gamma-ray irradiation (dose=100Mrad) had high wear performance, and then clinically used it as the material for acetabular sockets. He has reported excellent outcomes. In this study, we measured the wear three-dimensionally, and the oxidation by microscopic Fourier transform infrared spectrophotometry in retrieved high-dose cross-linked polyethylene [100Mrad PE] sockets implanted over 25 years.

Materials and methods: We revised two 100Mrad PE sockets (SOM type manufactured by Mizuho medical (JAPAN)), due to aseptic loosening, which had been implanted for 27 years approximately. The liner and volumetric wear were measured as previously reported [1]. Measuring points for oxidation index were (1) near surface point in unworn area, (2) near surface point in worn area, and (3) inner area which left any surface by > =2.5mm.

Results and discussion: The liner wears were 0.06mm and 0.29mm respectively. The volumetric wears were 25.8mm3 and 91.8mm3. The liner-wear rate of them were 0.002mm/year and 0.010 mm/year. The oxide index of each socket was 0.75, 0.62, 0.25 and 1.73, 0.67, 0.28, in order of the unworn area, the worn area and the inner area. Many researchers have reported that the annual liner-wear rate of UHMWPE sockets is from 0.1 to 0.2mm/year. We showed extremely less wear rate of the 100 Mrad PE sockets in comparison with UHMWPE sockets. Oxidation index in the worn area was approximately the same as that of UHMWPE sockets, which were determined in our previous study [2]. These results showed that 100Mrad PE sockets had maintained the high performance to the wear for long-term clinical use.

By 1998, 10 patients had undergone 12 revision total knee arthroplasties at our institute. One patient died three weeks after surgery due to cerebral infarction, leaving 11 knees of nine patients for evaluation. Average follow-up was 4.8 years (1 to 9 years). All components were subjected to revision surgery in five knees, the tibial tray and insert in four knees, and only the insert in two knees. Patients were evaluated with clinical examinations, radiographs, and the Knee Society Clinical Rating System.

After revision surgery, the Knee Scores and ROMs were restored to almost the same level as just after the first TKA. Re-revision was performed on two patients, one 103 months and the other 82 months after revision TKA. In those two patients, huge bone loss of the proximal tibial canal was filled with cement without bone graft. The other patients, however whose tibial trays were fixed with cement on adequate grafted bone obtained good results.

The femoral components that were not treated with revision surgery despite small flaws or scratches due to wear and tear of the tibial insert did not cause marked wear of the new tibial insert.

Conclusion: Bone loss of the proximal tibial canal should be filled with bone graft, not with cement only. Femoral components with small flaws or scratches, and without other ploblems, need not to be treated with revision surgery.

After having completed more than 150 primary knee arthroplasties with a new navigation system both analyzing the position of the implants as well as the soft tissue balancing in each range of motion, we performed the first revision surgeries in February 2001 using this device. At present we have revised 15 arthroplasties with the support of navigation. The reasons for revision were early loosening in 11 cases and instability in 4 cases. Intra-operatively, we were able to analyze the malpositioning of the implants and the disturbed soft tissue balance.

In most cases (n = 12), a femoral internal malposition was found. There was, therefore, extreme polyethylene wear on the medial plateau of the tibia and instability of the soft tissues on the lateral side. We were also able to find an incorrect joint-line and a malrotation of the tibial component. In all these cases specific intra-operative kinematics showed us the primary reason for early loosening. The navigation system screen provides not only information about the incorrect angle of the implant position but also indirectly via the kinematics, information about the relationship of the malpositionings between the implants. In many cases (n = 10) there were combined errors in positioning of the implants.

The first 15 cases show that malpositioning of knee implants can be analyzed with the new generation of navigation systems. These devices help the surgeon, in the operation room, to make his decision how to proceed.

The malpositioned implants showed extreme polyethylene wear demonstrating that the positioning of the implants does influence the outcome very much.

A useful navigation system in revision surgery is the one which is not related to a specific design of an implant but is usable in all cases so that every implant can be measured.

One hundred twenty eight revision hip arthroplasties performed before Dec. 1995 using the Wagner self locking prosthesis were followed for five to ten years. Obviously, the shape of this revision prosthesis complements optimal primary stability; however, one must pay attention not to undersize the stem. Hence, the most significant feature contributing to this self-locking type is the accomplishment of appropriate canal filling when revision with optimum anchorage length of prosthetic component. According to the clinical and radiological data obtained from our midterm results, we confirm the excellent validity of this system for treating the advanced cases of bone resorption for revision. Obviously the classification based on the femoral bone deficiency by the AAOS and DGOT are well documented. Even though we agree with the recent concept of Bourne-Rorabeck that is worthwhile tending to revert to a simple, but practical classification based on the cancellous bone’s quality and the intactness of the cortical tube, we believe that four of Bourne-Rorabeck had better be five in order to be clearer. Furthermore, additional seven various cases series of recent for subsidence of the femoral components were included in this study.

We beieve that the only contraindication is conversion from arthrodesis when the patient has long standing history of heavy plate and screws because of undue discrepancy of the stress shielding. Lastly, it is very unusual, however, we describe the operative technique which Wagner stem is inevitably removed.

An argument against the use of canal-filling, customised femoral stems has been that such implants have a large cross-sectional area and therefore are stiffer than standard, uncemented implants, thus inducing more stress shielding and bone loss in the proximal femur. The purpose of this study was to evaluate the association between the volume of the femoral stem and the change in periprosthetic bone mineral density (BMD) measured with DEXA.

Material and methods. Forty-eight patients with a mean age of 46 years had a THR using a customised femoral stem (Unique, SCP, Norway). BMD was measured in the 7 Gruen zones postoperatively and after then 3, 6, 12 and 24 months. Based on the 3-D computer model of the implant the volume of the intrafemoral part of the stem was computed. The association between the relative change in BMD at the 2 years follow-up and the volume of the stem was assessed using correlation analyses.

Results. No statistically significant correlation between the volume of the intrafemoral part of the stem and change in BMD could be found for the most proximal zones (1, 6 and 7). Neither was there an association between the postoperative BMD value and the degree of stress shielding. However, a weak correlation between the volume of the stem and change in BMD was found in Gruen zones 2, 4, 5 and for the overall BMD in all zones.

Discussion. No consistent or strong association between the volume of the femoral stem and the periprosthetic stress shielding at 2 years postoperatively was found in this study. In particular, the bone remodeling in the most proximal part of the femur was not correlated to the size of the stem. Contrary to other studies, our findings imply that stem size or stiffness is not a major determinant for proximal femoral stress shielding following THR.

The common factor in all (mechanical) prosthetic failure mechanisms is the induction of osteolysis around the endoprosthesis with subsequent prosthetic migration and finally loosening of the prosthesis. Both initial prosthesis-bone fixation and long-term prosthesis survival depend on the quality of the peri-prosthetic bone mass. The effects of treatment of RA patients with prednison are inhibition of osteoblastic activity and inhibition of calcium resorption from the intestines. The bone mass loss during the first six months of prednison treatment is substantial and will seldom be regained. Bisphosphonates are known to decrease osteoclastic activity and may therefore stop osteolysis at the bone-prosthesis interface.

The aim of the study was to evaluate a possible association of bisphosphonates with reduced migration of total knee prostheses (Interax, Howmedica Osteonics, Rutherfort, USA) in a high-risk group. Roentgen Stereophotogrammetric Analysis (RSA-CMS, Medis, The Netherlands) was used to measure the micromotion.

Retrospectively a group of nine RA patients treated with prednison (non-bisphosphonates group) and a group of fourteen RA patients (bisphosphonates group) treated with prednison in combination with bisphosphonates (Etidronate) were included from a prospective randomized study of 82 patients (Nelissen et al., 1998).

At the two-year follow-up evaluation, functional scores and knee scores did not differ significantly among the two groups. At the two-year follow-up evaluation, the non-bisphosphonates group subsided −0.47 ± 0.8 mm, and the bisphosphonates components subsided 0.07 ± 2.9 mm. In the analysis of variance with repeated measurements, with correction for follow-up time, sedimentation rate, and prosthesis fixation type, the bisphosphonates group migrated 1.20 mm less in the total migration (95% c.i.: 1.07–1.30 mm) compared to the non-bisphosphonates group.

In this study, bisphosphonates medication in addition to corticosteroid medication was associated with reduced migration of knee prostheses compared to corticosteroid medication alone.

Osteotomy of the greater trochanter continues to be an important surgical technique, especially in revision and difficult primary hip replacement, which implied the tightness of abductors.

We advocate the frog-leg lateral radiograph to determine the reducibility of the dislocation at the level of true acetabulum in order to identify the sufficient length of abductors while sitting. This flexibility of soft tissue structure composed of abductor is compromised once hip is reduced, because of difficulty in bringing the trochanter down to its bed.

In practice, transtrochanteric approach and shortening of proximal femur were applied and greater trochanter was transferred distally for restoring of abductors power(modified osteotomy), while reducing the possibility of trochanteric dislodgement. In fact, the wire force is reduced by 25 % while the bone union compressive force is unchanged in the modified osteotomy compared with conventional osteotomy. We evaluated 17patients(23 hips) in DDH and 15 patients in tuberculous hip. Conventional osteotomy was performed in tuberculous hip and modified osteotomy in DDH.

Nonunion of osteotomized trochanter was found in the case of 5 tuberculous hips especially irreducible in the frog-leg lateral radiograph preoperatively.

Radiographs historically have not been standardized according to magnification. Depending upon the size of a patient, a film will either magnify a bone and joint (of large patients with more soft tissue) or minify (in the case of thin patients). An orthopedic surgeon must guess at the degree of over or under magnification to select an implant that is neither too large nor too small. The surgeon may be aided by the incorporation of a marker of known size. By calculating the difference between the size of the marker displayed on the film and the actual size of the marker, the orthopedic surgeon can identify the degree of magnification/minimization and compensate accordingly when selecting a prosthetic template.

This activity takes time and also is subject to mathematical error. Digital pre-op planning allows for an image to be displayed electronically, and with the use of a known sized marker, automatically calculate the magnification and recalibrate the image so that it is sized at 100% from the perspective of the user.

Digital pre-op planning incorporates a library of electronic templates of prostheses, which can be standardized to exactly match the size of diagnostic image being displayed. Traditionally, an orthopedic surgeon places an acetate template enlarged to be 110% to 120% over an X-ray film magnified to be110% to 130%. When there is a significant variation in magnification between the template and the procedure, this can contribute to surgical error. This type of error will be virtually eliminated with digital templating that has the capability to identically scale electronic templates to the X-ray image being displayed. Digital pre-op planning enables surgeons to select from a library of templates and electronically overlay them on an image as well as perform the necessary measurements critical to the templating procedure which not only speeds up this process but, as will be shown, has the potential of delivering unprecedented accuracy.

Positioning and secure fixation of the acetabular component without bone cement in dysplastic and deficient acetabulum is technically challenging because of the distorted anatomy of the acetabulum such as shallow and very thin medial and anterior wall, deficient super-olateral dome. Several treatment options have been reported to solve these problems when total hip arthroplasty is needed.

The author developed a new technique of circumferential acetabular medial wall displacement osteotomy to get secure fixation of the cementless hemispherical acetabular component at the site of the original acetabulum. This technique preserves the thin medial wall, deepens, and enlarges the acetabulum without additional structural bone graft. The procedure can also provide appropriate positioning and sufficient coverage of the acetabular cup.

From October 1989 to October 1995, we analyzed 84 hips in 80 patients who had a cementless total hip replacement with circumferential acetabular medial wall osteotomy at the Kyung Hee University Hospital. There were 28 male and 52 female patients with an average age of 49 years (range 25–71). Initial diagnoses were congenital dislocation, severe dysplasia, infection sequelae, and secondary osteoarthritis. The follow-up period ranged from 5 years to 11 years, the average being 7.2 years. All acetabular components used in this procedure were cementless porous coated hemispherical Harris-Galante (HG) I or II cup. The acetabular cup had secure fixation at the site of the original acetabulum without bone cement in all cases. Cup coverage ratio has become 97.7% in average. There was no radiolucent line around the cup or loosening. None of the acetabular cups with circumferential acetabular medial wall osteotomy had signs of medial migration. Bone union at the site of osteotomy was achieved in all cases. Bony ingrowth into the porous surface and remodeling around osteotomized acetabular medial wall was excellent. Technical pitfalls and advantages in biomechanical viewpoint of the procedure will be discussed.

Introduction: A 2-stage approach is often employed to treat infected TJA. Success rates have been reported between 85–100%. Other authors favor multiple routine debridements (I& D) to lower the infection rate. This study compares the relative effectiveness of 2-, 3- and 4 stage treatment approaches.

Methods: Between 1988 and 1998, all infected TJA at our institution were treated with a 2-, 3- or 4 stage approach. In the 2-stage approach, prosthesis removal was followed by 6 weeks of IV antibiotics and reimplantation. In the 3-stage approach, an additional I& D was added 5–7 days after prosthesis removal. In the 4-stage protocol, a third I& D was performed after completion of antibiotics. Negative cultures led to reimplantation. Positive cultures led to an additional 6-week course of antibiotics, and then repeat 3rd and 4th stages. Patients retained their components if free of infection, on chronic antibiotic suppression or after additional I& D. Patients were free of infection if no more treatment was needed.

Results: 83 patients with infected TJA were treated. Average follow-up was 25 months. Of the 2 stage patients, 9/10 (90%) retained their components, and 7/10 (70%) was free of infection. Of the 3 stage patients, 32/37 (86%) retained their components, and 28/37 (76%) was free of infection. Of the 4 stage patients, 34/36 (94%) retained their prosthesis, and 30/36 (83%) was free of infection. Seventeen additional patients in the 4-stage group had positive cultures at the third stage. After additional treatment 13/17 (76%) retained their components and 12/17 (71%) was free of infection. No correlation was found between infection severity (gram positive vs. negative organisms; single vs multiple organisms) or initial diagnosis.

Discussion. Our ten-year experience with infected THA suggests that multiple I& D are required for successful treatment. Repeat I& D assures a sterile wound, as tissue culture is more sensitive than aspiration. Importantly, persistent infection after three I& D and appropriate antibiotics led to poorer results, suggesting that other host factors may preclude these patients from reimplantation. Given the exorbitant costs of treating failed reimplantations, an additional routine I& D may in fact be cost-effective across an entire population of infected TJA patients. Further analysis will focus upon cemented versus cementless implants, cost-benefit ratios of multiple debridements, nutritional parameters, functional assessments of patients at latest follow-up, cost analysis, and the value of preoperative.

Conclusion: We recommend a 4-stage approach to the treatment of infected THA.

The aim of this study was on the one hand to compare the fixation of a posterior stabilised prosthesis (PS) and a PCL retaining mobile bearing design (Interax, Howmedica Osteonics, Rutherfort, USA) and on the other hand to measure the mobility of the mobile bearing. All measurements were carried out by means of Roentgen Stereophotogrammetric Analysis (RSA-CMS, Medis, Netherlands).

A prospective,randomised,double-blind study (N=28) was conducted to assess the micromotion of the components. At the one-year follow-up evaluation, the micromotion of the PS-components and the mobile bearing components were not significantly different. The PS-tibial components subsided −0.063 ± 0.177 mm and the mobile bearing knee tibial components subsided 0.067 ± 0.084 mm. The PS tibial component showed a higher variability in the migration results indicating a number of PS with rather large micromotion.

For three patients, the in vivo motion of the mobile bearing with respect to the metal backing was assessed at 30, 60 and 90 degrees of passive flexion. Two of mobile bearings moved posteriorly (2.4 and 2.9 mm) at respectively 60 and 90 degrees of flexion and showed a medial-lateral translation of 0.03 and 3.5 mm. One mobile bearing moved only 0.4 mm posteriorly at 90 degrees of flexion but showed a lateral-medial translation of 3.1 mm.

The broad range of kinematic patterns of mobile bearings during flexion that is observed in fluoroscopic studies is also observed in this study. A possible positive effect of mobile bearing movement may be found in the smaller variability of the micromotion of the mobile-bearing knees compared to the PS knees. The assumption was that shear forces in tibial bones implanted with a mobile bearing prosthesis would be better dissipated from the prosthesis-bone interface resulting in less micromotion. The kinematics of an additional number of mobile bearing knees -already included in the micro-motion study- will have to be assessed in order to determine the relation between mobility and micromotion.

The advantages of high viscosity Simplex AF cement (PMMA) compared to low viscosity Simplex P are the low porosity, the high fatigue strength, the lower polymerization time, and the lower maximum polymerization temperature. A prospective, randomized, double-blind clinical study was conducted to assess the in vivo effects of viscosity of bone cement on the micromotion of a polished tapered stem and UHMWP-cup (Exeter, Stryker-Howmedica). Roentgen Stereophotogrammetric Analysis (RSA-CMS, Medis, The Netherlands) was used to measure micromotion.

Twenty patients were included in a Simplex AF group (70 ± 4.3 years), and twenty patients were included in a Simplex P group (71 ± 7.3 years). No significant differences in body mass index and clinical hip scores were observed between the two studied groups.

There was no significant difference of the subsidence of both high and low viscosity cemented Exeter stems. The subsidence was according to the literature and showed that the viscosity of the bone cement did not influence the cement-implant bond of this polished tapered stem design.

The total migration of the cups and the migration along the medial-lateral axis were significantly larger for the Simplex AF cemented cups compared to the Simplex P cemented cups (p=0.037). This can be explained by the higher cement mantle thickness in acetabular Gruen zone 2 (p=0.003) and 3 (p=0.004) of the Simplex AF cemented cups.

We conclude from this study that the viscosity of the bone cement has no effect on the subsidence of polished tapered stems and that a high cement mantle thickness around an UHMWP-cup has a negative effect on fixation.

Polyethylene wear is a significant factor limiting survivorship of total knee arthroplasty (TKR). Crosslinking of polyethylene has been shown to significantly reduce wear in hip arthroplasty but has not been reported for TKR. This study measured wear in polyethylene cross-linked to two levels in a knee wear simulator.

Six polyethylene knee inserts were tested in a knee wear simulator. Inserts were manufactured from polyethylene crosslinked to two different levels: 2.5 Mrad (Low-X) and 10.5 Mrad (High-X). Each implant was enclosed in a closed lubricant (50% alpha fraction calf serum) recirculation chamber, maintained at 37°C and changed every 500,000 cycles. Physiologic levels of load and motion were applied at 1 Hz for a total of 6,000,000 cycles. Wear was measured by the gravimetric method before wear testing and at every 500,000 cycles. Semi-quantitative wear assessment was performed by imaging the insert surfaces at 10x magnification.

The Low-X inserts demonstrated significantly higher wear rates (mean 4.66 mg/million cycles) than the High-X inserts (mean 1.55 mg/million cycles, p < 0.001). Wear scars on the Low-X inserts were irregular and visibly deeper than those on the High-X inserts. The machining marks on the surface of the insert were also better preserved in the High-X insert wear scars. These results suggest that crosslinked PE can significantly reduce wear in TKR under physiologic conditions. This can result in reduced lysis and increased survivorship. Localized damage can cause catastrophic failure in polyethylene knee inserts. Therefore, further studies are necessary to evaluate wear under these conditions.

Introduction: Proximal porous coating for cementless fixation of femoral stems enjoys increasing popularity. We report on the intermediate to long-term results with a circumferentially proximally coated stem with a non-porous cylindrical diaphyseal portion. The smooth stem provides temporary rotational stability so that proximal bony ingrowth can occur.

Materials and methods: Between 1991 and 1994, 124 Multilock stems were implanted in 101 patients. Patients were followed prospectively and re-evaluated at a minimum five years postop (range 60 to 117 months) by an author other than the surgeon. Four patients (5 hips) were lost to follow-up. Five patients (6 hips) had died. Twenty-six patients (30 hips) had phone interviews more than five years after surgery, but no radiographs as they refused to return for followup. None of these patients had required additional surgery and all were extremely satisfied with their outcomes. Sixty-six patients (83 hips) had clinical and radiographic followup at minimum five-years post-op. This report focuses upon this last group.

Results. The average age at surgery was 53.8 years (range, 27–75). The average follow-up was 78 months (range, 60–117). The average Harris Hip Score was 93 (range, 52–100). One stem had been revised for loosening (1%), and none were radiographically loose. Eight patients (9.6%) had minimal thigh pain related to excessive activity. These patients required mild analgesics only. Eighty-two stems (99%) achieved bony ingrowth. Twenty-nine stems (35%) had minimal osteolysis limited to Zones 1 and 7. There were no cases of diaphyseal lysis. Radiolucent lines adjacent to the porous coating were evident in 3 stems (3.6%), and along smooth portions in 20 stems (24%). No radiolucent lines were progressive or divergent. Some degree of stress shielding in the proximal metaphysis was evident in 52 hips (63%), but only 2 had cortical resorption.

Discussion and conclusion. Given the young age and high activity level of this cohort of patients, the Multilock stem has fared extremely well. Loosening and revision rates were very low, and distal osteolysis had not occurred. Bony fixation occurred reliably. Proximal stress shielding remains concerning and further follow-up will determine whether this becomes clinically significant. Lastly, patient function and satisfaction were high. In conclusion, the Multilock proximally porous-coated stem can be expected to perform well in the intermediate to long-term in young, active patients.

An anatomical cementless stem sometimes does not fit the femur of Japanese osteoarthritis (OA) patients due to deformity of the proximal femoral canal.

In order to develop a new stem, we performed morphological analysis of 36 normal femora and 113 OA femora by using a computer aided design system and a three-dimensional canal fill ratio of anatomical stem was calculated.

Thirty-six normal femora and 113 OA femora were reconstructed from 3D-CT data by using a computer aided design system. We analyzed each femur, and it became clear that there are 3 types of proximal femur in Japanese OA patients. In typeI, the configuration is the same as normal (42%). In typeII, the medial cortex is more steep (29%). In typeIII, the posterior cortex inclines anterior (26%). We chose 5 femora of the same size from each of the three types, and applied the anatomical stem of the most suitable size to each femur in the computer, we then calculated a three-dimensional canal fill ratio of the anatomical stem in the proximal portion of femoral canal.

The mean canal fill ratio was 76.4% in typeI, 60.0% in typeII, and 57.2% in typeIII. The canal fill ratio in typeI was significantly higher than the other types.

It is thought that to fill the proximal femoral canal with cementless stem is important to stabilize the stem and can lead to a good result. The anatomical stem fitted for the typeI, but did not fit for typeII and III, so we must consider developing a more suitable stem for typeII and typeIII.

We want to prove that you cannot make a good fitting stem of a THP before surgery because the resulting shape of the femoral cavity is set after all the tools have been introduced in the femur. We are fully aware that fit and fill alone is not enough to obtain good fixation therefor all the investigated implants were plasma spray coated with HA.

We have investigated two groups of patients:

Pre – operative group: custommade implant based on CT scans and manufactured before surgery. The proximal part was size for size and coated with HA; the distal part is cylindrical (44 cases, followup from 2.6 years to 6.2 years).

The manufacturing procedures and coating specifications for both groups were exactly the same. We’ve compared the Harris hip score for both groups and we’ve performed a radiolographical analysis.

Of the preoperative group 6 protheses had to be revised. This results in a revision rate of 13 % which is not acceptable. In the peroperative group however, no revisions have been performed. Radiografically the peroperative group showed much better results than the preoperative group.

The obtained results suggest that it is not only important to have a good bone growth initiator such as HA but the implant needs to be in close contact with the bone.

In primary malignant bone tumours, the “en – block” excision with the sacrifice of soft tissues causes a functional deficit of the interested limb. There are many possibilities for reconstruction after a wide resection of the proximal humerus. The Authors report their experience using megaprostheses, focusing to soft tissue reconstruction, in order to obtain a good and fast functional recovery of the involved limb. 13 megaprostheses of the proximal humerus were employed. All patients were affected of primary malignant bone tumors with different histology. The tumor was staged according to Enneking’s system. 8 cases were classified as IIB and the remaining as IIA. All the tumors were treated with an intrarticular resection. Soft tissues reconstruction was performed, in 8 cases, using a mesh (Trevira tube), dressed all along the prosthesis, with a high resistance to traction. Radio and/or chemotherapy were employed referring to the histology.

At a medium follow – up of two years, for the surviving patients, we have obtained excellent functional results in 1 case, good in seven cases, fair in three cases and poor in two cases. The size of the resection is a main factor in order to obtain a good functional recovery of the joint motion. A wide excision (below deltoid insertion) with the sacrifice of large muscular masses and of the osteoarticular structures can represent a functional amputation causing the loss of muscles that are important to have an acceptable joint movement.

In our experience we retain that the use of modular prostheses in reconstructive orthopaedic surgery is advantageous because of its versatility and of its quick implantation, despite of other reconstructive systems. Moreover the use of a device, as that described, for an easy anchorage of the myotendinous structures, allows a quick functional recovery offering the patients considerable advantages for their social life.

Zirconia has considered a good material for manufacturing of ball heads in total hip replacement due to high mechanical properties of this ceramic material. However in the literature the problem of heads biocompatibility is still debated. The Authors reported their experience in ten years of research on the biological properties of this material. In vitro tests were performed onto materials in form of powders, analyzing the inhibitory effects on human lymphocyte mitogenesis, and in form of plates measuring adhesion and spreading of 3T3 fibroblasts. A mutagenic test was also performed. In vivo tests were performed by injection of powders in mice and evaluating the survival of animals according to ASTM F – 750. We also inserted ceramic in form of cylinders into proximal tibial metaphysis of NZW rabbits and analysed local and systemic reaction due to material diffusion. We also developed a system of production of Zirconia particles by inserting ceramics under patellar tendon of NZW rabbits.

In vitro tests showed that Zirconia powders and plates induced a similar effect of Alumina ones; no mutagenic effect were observed using our samples, demonstrating that Zirconia has no carginogenic effects. In any case the diffusion of particles didn’t show modifications into internal organs (lung, kidney, liver, spleen) of mice and rabbits. In time (one year after operation) the connective tissue present at bone ceramic interface is transformed into lamellar bone.

Our experience demonstrates that Zirconia may be considered a good material for prosthetic implants.

The Authors analysed two cases of catastrophic failures of Total Hip Prostheses due to the disruption of the PE inlay and the Ti-alloy metal back of the acetabular components. In the cases reported the PE inlay (4 mm in thickness) was coupled with a 32 mm in diameter Alumina ball heads. At time of revision the alumina ball heads showed many black marks due to the contacts with the Ti-alloy metal back. The sockets showed severe damages, concentrated in the superolateral zone. The PE inlays were disrupted. Almost a third of the metal back is missing. A large metallosis was also visible in the membrane at the interface between implant and bone. Histologic sections showed a large amount of metallic debris in a pseudovillous membrane. At higher magnification oligonuclear cells in a rich in vessels stroma were in contact with metal particles. PE debris with the characteristic birifrangent aspect to the polarised light microscope was contained into polynuclear giant cells. SEM showed that the size of 25% of particles was less than 1 μm, while the size of 53% of wear debris is in the range from 1 to 5 mm. EDAX confirmed that these particles consisted of Ti alloy. The Authors analysed the possible roles of different factors in the etiology of this cup failures and concluded that in both the cases analysed the initiator of the failure was the size selection of the prosthesis, and in particular the PE thickness, followed by the positioning of the acetabular component. The deformation of the PE inlay leads to rupture of the inlay itself, followed by the direct contact between the Alumina ball head and the titanium alloy cup, causing the disruption of the Ti-alloy metal back, with massive release of wear debris in the surrounding tissues.

Introduction: Tapered proximally porous-coated stems have many advantages, including no diaphyseal reaming, proximal fixation, and less thigh pain. Conventional rehabilitation suggests that touch-down weight-bearing (TDWB) is required for bone ingrowth and soft-tissue healing to occur. Immediate weight-bearing as tolerated (WBAT) could provide rapid mobilization and quicker recovery and faster return to functionality. This study examines early results with WBAT after implantation of a tapered stem.

Materials and methods: During 1999 and 2000, all THAs were performed with a fiber-metal taper (FMT) component and WBAT was allowed immediately. No cemented or hybrid THAs were performed during this time-period. Radiographs were obtained in the recovery room, and then at 6, 12 and 52 weeks postoperatively. Patients with a minimum 12-week follow-up were included to answer five study questions: Does immediate WBAT affect ingrowth of the stem? Does immediate WBAT lead to more subsidence and/or instability? Does immediate WBAT affect the acetabular component? Does immediate WBAT affect Harris Hip Score? Is there an age limitation? Forty-one cases performed had a minimum 12-week follow-up. Four intraoperative fractures occurred (4.8%), and these patients were excluded as they were made TDWB for 6 weeks. Thus, 37 cases remained and comprised the study group.

Results: Of the 37 patients, 21 were perfomed for OA, 14 for AVN and two for post-acetabular fracture DJD. The average age was 57 (range, 16–78). The average follow-up was 6 months (range, 3–20 months). Radiographically, all 37 stems were ingrown by the 12-week radiograph. Seven patients (17%) had subsidence of the stem, with an average of 0.9 mm (range, 0–7 mm). There were no dislocations. Thirty-six acetabular components (97%) achieved bony ingrowth by the 12-week radiograph. No cups had measurable migration and 9 had nonprogressive radiolucent lines present in one zone. The average HHS was 88 (range, 64–100). Among patients older than age 70, 5/5 stems were ingrown with one stem showing subsidence prior to ingrowth. Two patients (5.4%) had minimal thigh pain.

Discussion and conclusions: This study demonstrates that immediate WBAT does not preclude bony fixation of the stem or acetabulum after Cementless THA. Clearly, longer follow-up will determine whether issues regarding fixation arise at later dates. However, it would be expected that since bony ingrowth occurs, reliably, fixation should remain stable for long periods of time. One immediate advantage of WBAT is that rehabilitation can be facilitated.

Radiographs are often used to determine the varus/ valgus alignment of the prosthesis in relation to the long axis of femur. This is usually considered to be one of the important parameters in predicting early mechanical failure of the total hip replacement.

The measurements made by the University of Dundee X-Ray Analysis Software and skilled manual operators of the varus and valgus angulations of hip prosthesis in relation to the femoral shaft were compared for inter and intra-observer reliability.

The manual measurements were carried out on the same randomly selected digitised images of 78 postoperative X-rays by two independent observers and by the same analysis software twice.

The results of the study showed a very high agreement between the readings of the two methods (the largest difference was 0.6 degrees) and two observers (the largest difference being 0.08 degrees) indicating excellent intra and inter observer reliability. The lowest correlation was 0.82 and this was between software reading 1 of observer 1 and software reading 1 of observer 2. The highest correlation of 0.99 was between software reading 1 and software reading 2 for the same observer. The software analysed the x-rays with precision and accuracy and was much faster than manual measurement. A further benefit of the computerised method is an unskilled operator can be trained in 15 minutes to use the software

The Pyramid stem is a tecnical evolution of the previous Zweimuller, in order to have the best press fit. It has no more longitudinal grooves and neck, but has a distal arcuate fissura to improve the elasticity and to avoid distal stress by a uniform contact with the bone. We show the breaking test and resistence test. It has a rectangular section, a uniform thickness along all its lenght to have a good diaphyseal anchorage on four zones of the internal cortex to avoid torsional stress and to maintain endomi-dollar vascularization. This stem has the maximum contact surface not only with the dyaphysis, but also with the metaphysis and the trochanter. It has been studied with the femur morfology, to fill the bigger ones with a cylindric canal and the smallest ones with a conic canal. Transverse section has increased by the pyramids that increase contact surface bone-prosthesis, primary stability and press-fit. It is straight both in the frontal and in the sagittal plane to realise a good primary stabilization according with the concept of the three support point. We present our surgical experience to obtain a correct position of the stem, and the best use of the instrumentation. From June 1997 to May 2001 we have used this stem in 257 hips; we have obtained excellent and good results in 87% of patients. We show some cases and the only one stem removed. This stem allows a rapid postoperative rehabilitation following our protocol as explained.

Introduction: Previously, in vivo kinematic studies have determined that axial rotation patterns are quite variable between implant type and specific subjects. Previously, kinematic studies have determined that subjects having a mobile bearing TKA experience axial rotation, but it was unknown as to whether the bearing was rotating. Therefore, the objective of this present study was to analyze the in vivo kinematics for subjects having a mobile bearing prosthesis to determine if the polyethylene rotates relative to the femoral and/or the tibial components.

Methods: Femorotibial contact positions for ten subjects having a mobile bearing TKA, implanted by a single surgeon, were analyzed using video fluoroscopy. Each subject, while under fluoroscopic surveillance, performed a weight-bearing deep knee bend to maximum flexion. Video images were downloaded to a workstation computer and analyzed at varying degrees of knee flexion. Each polyethylene component had four metallic beads, inserted at known positions. Using a 3D model-fitting process, the femoral, tibial and polyethylene insert components were overlaid onto the fluoroscopic images. Initially, the polyethylene insert was made transparent, but the computer would overlay the four metal beads. Then, the polyethylene insert was made viewable and analyzed relative to the metal femoral and tibial components.

Results: All of the subjects experienced polyethylene bearing rotation relative to the metal tibial component and minimal rotation relative to the metal femoral component. On average, relative to the metal tibial component, the subjects experienced 4.7° (2.1 to 7.9°) of polyethylene bearing rotation. The subjects experienced a similar amount of metal femoral component rotation, relative to the metal tibial component. On average, the subjects experienced 4.0° (−0.7 to 10.0°) of rotation of the metal femoral component relative to the metal tibial component. Therefore, on average, subjects experienced only 0.7° of rotation for the metal femoral component relative to the polyethylene bearing. Also, on average, from full extension to 90° of knee flexion the subjects experienced −2.9 mm of posterior femoral rollback of their lateral condyle and –0.4 mm of their medial condyle.

Discussion: This is the firs study to determine the in vivo rotation of the polyethylene bearing for subjects having a mobile bearing TKA. The results from this study determined that the polyethylene bearing is rotating relative to the metal tibial component, but not relative to the metal femoral component. Therefore, as the metal femoral component axially rotates the polyethylene bearing is rotating a similar amount in the same direction. Since bearing rotation does occur under in vivo conditions, subjects implanted with a mobile bearing prosthesis may be subjected to lesser amounts of contact stresses, which may be beneficial to them.

Load-controlled knee simulators, representing the passive constraints and joint loads observed in the natural knee, have been developed to assess device-dependent kinematics and wear damage of total knee replacements (TKR) in a controlled mechanical environment. Using a finite element model (FEM) to represent the simulator, our objective in this study was to quantify the variations in kinematics, contact stresses, and contact areas that occur with variations in the ‘soft-tissue’ spring stiffness and coefficient of friction for a conforming knee design.

A finite element model was created of the Insall-Burstein Posterior-Stabilized II knee system. The model conditions corresponded with the International Standards Organisation (ISO) test protocol #14243-1 and consisted of the prescribed flexion angle, the axial compressive load, the anterior-posterior (AP) force, the internal-external (IE) moment, and linear springs mounted to provide AP and IE restraints. This setup has been validated as a reasonable equivalent system for this design in the Instron-Stanmore knee simulator. The linear spring constant was set at 7.24 N/mm and the coefficient of friction was 0.01; both values were then varied by an order of magnitude. The implant kinematics and the maximum contact stress and areas of contact over the loading cycle were determined.

Varying the spring constant by a factor of two changed the AP motions and IE rotations of the tibial insert by about 20%. The maximum contact stresses, occurring during peak loads and moments, varied by 40%, while the area of contact over the full cycle changed by 30%. Changing the coefficient of friction had little effect upon the dependent variables. Wear is a function of both stresses and kinematics. This study indicates that stresses in this design are more sensitive than kinematics to changes in ‘soft-tissue’ stiffness. Therefore, both must be considered to determine wear potential.

After having completed more than 150 primary knee arthroplasties with a new navigation system both analyzing the position of the implants as well as the soft tissue balancing in each range of motion, we performed the first revision surgeries in February 2001 using this device. At present we have revised 15 arthroplasties with the support of navigation. The reasons for revision were early loosening in 11 cases and instability in 4 cases. Intraoperatively, we were able to analyze the malpositioning of the implants and the disturbed soft tissue balance.

In most cases (n = 12), a femoral internal malposition was found. There was, therefore, extreme polyethylene wear on the medial plateau of the tibia and instability of the soft tissues on the lateral side. We were also able to find an incorrect joint-line and a malrotation of the tibial component. In all these cases specific intra-operative kinematics showed us the primary reason for early loosening. The navigation system screen provides not only information about the incorrect angle of the implant position but also indirectly via the kinematics, information about the relationship of the malpositionings between the implants. In many cases (n = 10) there were combined errors in positioning of the implants.

The first 15 cases show that malpositioning of knee implants can be analyzed with the new generation of navigation systems. These devices help the surgeon, in the operation room to make his decision how to proceed.

The malpositioned implants showed extreme polyethylene wear demonstrating that the positioning of the implants do influence the outcome very much.

A useful navigation system in revision surgery is the one which is not related to a specific design of an implant but is usable in all cases so that every implant can be measured.

Introduction: The consequences of incorrect implant orientation and improper limb alignment in TKR surgery are: 1) accelerated implant wear; 2) early prosthesis loosening; 3) sub optimal clinical function. Although mechanical alignment guides have improved the precision of TKR surgery, it has been estimated that alignment errors of more than 3 degrees occur in at least 10% of TKR even when performed by experienced surgeons using mechanical alignment systems of modern design. The purpose of this study was to determine the accuracy of TKR surgery performed with conventional instruments using a computer assisted navigation system (OrthoPilot) as a measurement tool.

Methods: 35 patients underwent primary TKR performed with a conventional intramedullary, mechanical instrumentation system. Minimal follow-up was 1 year. The OrthoPilot was used to measure: 1) pre-operative limb alignment; 2) pre-operative medial-lateral stability; 3) pre-operative flexion; 4) post-operative alignment; 5) post-operative medial-lateral stability; 6) post-operative flexion. Patients consented to the use of the Ortho-Pilot as part of an Investigation Review Board approved study. Limb and implant alignment were measured on pre- and post-operative x-rays and compared to the alignment results measured by OrthoPilot. Knee society scores were obtained on all patients.

Results: No complications were associated with the use of the OrthoPilot. Post-operative pain and function were not affected by the use of the OrthoPilot. Pre-operative angular deformities measured by OrthoPilot ranged from 12 degrees varus to 20 degrees valgus and 12 degrees flexion to 7 degrees hyperextension. Post-operative angular deformities ranged from 2.5 degrees varus to 2 degrees valgus and 5 degrees flexion to 2 degrees hyperextension. Pre-operative medial-lateral laxity ranged from 0 to 10 degrees. Post-operative medial-lateral laxity ranged from 3–5 degrees. Pre-operative flexion ranged from 95 to 125 degrees. Post-operative flexion ranged from 115 to 136 degrees. Movement of the pins that hold the diode containing rigid bodies occurred in 5 cases. Inconsistencies of more than 3 degrees in limb registration by the OrthoPilot occurred in 7 cases. Pre- and post-operative x-ray measurements varied from OrthoPilot measurements by more than 3 degrees in 25 cases. Surgery time with OrthoPilot.

Conclusions: OrthoPilot is safe. No complications occurred attributable to the system. It took approximately 10 cases to establish a consistent registration technique using the OrthoPilot. Pin movement can occur and significantly affects the accuracy of the measurements. The OrthoPilot was useful as a measurement tool for determining the pre- and post-operative alignment, stability and range of motion of a TKR. The use of conventional intramedullary mechanical TKR instruments can result in accurate and reproducible frontal and sagittal limb alignment. X-rays are not accurate for determining pre- and post-operative limb and implant alignment.

Introduction: Polyethylene wear debris is the main contributing factor that leads to aseptic loosening and osteolysis. The main objective of this study was to evaluate the role of hydroxyapatite (HA) in third-body polyethylene wear in total hip arthroplasty.

Materials: 199 primary cementless THA’s (174 patients) performed by a single surgeon were enrolled in a prospective randomized study comprising Hydroxyapatite and non-hydroxyapatite coated femoral implants. The femoral component had metaphyseal-diaphyseal fit design with proximal plasma sprayed titanium circumferential porous coating. The hydroxyapatite coating was 50 – 75 micrometers over the porous surface with the components of identical design. The acetabular component was plasma sprayed titanium porous coated shell without hydroxyapatite

Introduction: This purpose of this prospective review is to evaluate the 12-year results of a previously unreported collarless, cemented, normalized, straight-backed Omnifit femoral stem with a surface roughness of 30–40 microinches.

Methods: Between January 1986 and June 1991, a single surgeon prospectively implanted 305 consecutive cemented THA’s (275 patients) utilizing second-generation cement technique and a posterolateral exposure. The acetabular component was cemented all-polyethylene (4150 resin), with calcium stearate and gamma sterilized in air. Two independent observers employing a patient administered questionnaire, HSS scores and established radiographic criteria performed clinical and radiographic evaluation. The cumulative survivorship analysis was analyzed in terms of best case and worst case.

Results: The demographics included a mean age of 70 years with 170 females and 105 males and a mean body weight of 154 lbs. The preoperative diagnosis was osteoarthrosis in 260 hips, rheumatoid arthritis in 20, fracture in 13, AVN in 8, Paget’s in 2 and hip dysplasia in 2. The mean HSS score was 37.5 out of 40 at last follow-up. The mean clinical follow-up was 12 years and mean radiographic follow-up was 10 years. The overall projected clinical survival was 95.1% at 15 years (CI +3.4%). The cement mantle was grades A or B in 90% and grade C1 in 10%. Femoral stem alignment was neutral in 53%, valgus in 31% and varus in 16%. Revision THA was performed in 9 hips. Both components were revised in 3 cases (2 infection, 1 recurrent dislocation). Socket revision was performed in 4 cases (1.31%) and femoral component revision in 2 cases (0.65%) due to aseptic loosening.

Discussion: This report demonstrates the excellent results of the collarless, cemented, normalized femoral stem with a surface roughness of 30–40 microinches. Although controversy exists on surface roughness and porosity reduction, meticulous technique in the attainment of a centralized femoral stem with a good cement mantle, provides a reproducible, high quality of function and durability of THA in patients 60 – 80 years of age at 12-year follow-up.

Introduction: Although the problems of patello-femoral kinematics in contemporary total knee arthroplasty are multifactorial, meticulous surgical technique is pivotal in providing optimal and durable function. The goal of this study was to evaluate the incidence of lateral release comparing fixed and mobile bearing posterior stabilized modular press-fit condylar TKA’s with patellar resurfacing.

Materials and methods: Cohort 1 comprised 100 consecutive cemented Press-Fit Condylar Sigma, (Johnson & Johnson, Raynham, Massachusetts) modular total knee prostheses with a posterior cruciate substituting design and dome shaped single peg patellar component implanted prospectively by a single surgeon. Cohort 2 comprised 100 consecutive cemented Press-Fit Rotating Platform Sigma (Johnson & Johnson, Raynham, Massachusetts) modular total knee prostheses with the same posterior cruciate substituting design and patellar component.

The surgical technique comprised cutting the tibial surface perpendicular to the long axis, ligament balancing in extension followed by femoral component rotation referenced off the proximal tibial cut to produce a rectangular flexion gap. The patella was cut to the level of the lateral facet and tibial component rotation was referenced off the center of the ankle. Lateral release was performed if congruent patello-femoral contact was not attained in knee flexion. Clinical and radiographic review was performed as per Knee Society criteria. Additional radiographic evaluation included patellar displacement, tilt, residual bone thickness and coverage ratio. A patient-administered questionnaire was used to evaluate anterior knee pain and patello-femoral function 1 year after surgery.

Results: The incidence of lateral release in the fixed-bearing cohort was 10% 1 compared to 0% in the mobile bearing cohort (p< 0.05). There were no significant differences in terms of clinical or radiographic parameters at short term.

Discussion: This study demonstrates the benefit of self-correction of tibiofemoral rotational mismatch with mobile bearing TKA’s and improvement in patello-femoral tracking. Longer follow-up is necessary to confirm the effect on patello-femoral wear, fixation and durability.

Currently available uncemented acetabular components appear to provide very reliable fixation for at least 10 years. However, these cups have been associated with a significant incidence of polyethylene wear. Osteolysis associated with this wear is emerging as the most significant problem in total hip replacement surgery. The purpose of this presentation is to describe the rationale for reducing polyethylene wear through the use of an uncemented acetabular component made of a polyethylene/ Tantalum (Trabecular Metal) composite and to describe the initial clinical experience with this cup.

Clinical and radiographic data were prospectively collected on the first 125 consecutively performed total hip replacements in which a tantalum (Trabecular Metal), monoblock acetabular component was used. Minimum follow-up was 24 to 46 months. Sixty three percent of the patients were female. Mean age was 61. The diagnoses were: OA-74%; AVN-12%; RA-10%; other-4%. 50% of the hips had cemented femoral components. 20% of the patients were Charnley Class 1, 30% Charnley Class 2, and 50% Charnley Class 3. At most recent follow-up, all patients were pain free (Ave. pain score pre-op.- 6.7, post-op.-1.4). No patient’s function was limited by hip function (Ave. Harris hip score pre-op.-38, post-op.-92). All hips had radiographic findings consistent with bone-ingrowth. Gaps in zone 2 were seen in 10% of hips, but filled in by one year. The rate of polyethylene wear as measured by the Martel technique was less than 0.07mm/year in the first two years.

There were three complications in the group: 2 dislocations which re. The early experience with the monoblock, tantalum cup indicates that initial fixation is secure, even without screws, and that initial polyethylene wear is very low.

Introduction: This prospective review provides an update on a cohort of 150 consecutive primary TKA’s with intermediate follow-up (mean 10 years) and provides insight into the benefits of the device and casts light on the effects of polyethylene wear in posterior stabilized modular designs.

Materials: Between February 1988 and February 1990, 150 consecutive cemented Press-Fit Condylar (PFC, Johnson & Johnson, Raynham, Massachusetts) modular total knee prostheses (118 patients) with a posterior cruciate substituting design were implanted prospectively by a single surgeon. Two independent observers employing a patient administered questionnaire and clinical and functional Knee Society scores assessed the clinical outcome. Radiographic review was performed per the Knee Society criteria. The cumulative survivorship analysis was performed in terms of best case and worst case.

Results: 20 patients (30 TKR) died and 14 patients (15 TKR −10%) were lost to follow-up. The mean duration of follow-up in this cohort of survivors was 10 years (range 8.5 – 12 years). The mean clinical and functional scores were 88 and 73 points respectively. Of the 105 TKR followed up, good to excellent results have been attained in 89.5%. 45 patients reported participation in recreational sports. The overall projected clinical and radiographic survival was 93.6% at 12 years (CI +5.9%). Revision TKA was performed in 5 knees – 2 infection, 1 instability and 2 polyethylene wear, synovitis and osteolysis. There were no cases of aseptic loosening in the absence of polyethylene wear.

Discussion: Although the 12-year survivorship results of the cemented, posterior cruciate substituting press-fit condylar modular total knee prosthesis have been successful in terms of quality of fixation, the phenomenon of ‘back-side’ polyethylene wear at the modular tibial base-plate and resultant osteolysis offset the benefits of the modularity with longer follow-up. Attention needs to be focused on the improvement of the locking mechanism or alternatives with improved newer wear-resistant polyethylene, one-piece tibial components or newer implant designs with mobile bearings such as rotating platforms with posterior substituting design.

It is estimated that there will be over 12,000 total shoulder replacements implanted this year. In the best series, the survivorships of these devices are 90% at 7 years. However, there are radiographic indications that the long term success will be limited to wear and damage to the polyethylene glenoid components. Like tibial insert in total knee replacements, the glenoid is subjected to both rolling sliding motions of a metal counterface. Additionally, the compressive loads on the glenoid have been estimated to be as high as 2800N under ‘normal’ conditions. In contrast to tibial inserts, glenoid components are all typically less than 6 mm thick. In metal backed glenoid devices, the polyethylene thickness is often < 3 mm. The effect of these parameters and kinematics on polyethylene damage has not previously described. Although total shoulder replacements have been in use for over 25 years, there have been no reports describing the nature and extent of glenoid polyethylene wear and damage.

We report the determination of polyethylene damage type and severity of 38 retrieved glenoid components of at least 4 different designs. Wear and damage were considered significant when either 80% of the glenoid surface was damaged or if over 25% of the component was worn away. Abrasion, burnishing and pitting were the main modes of damage. There were 2 fractured components. There was significant UHMWPE wear and damage in 17 (45%) components. In nine of these, the component was completely worn through.. These findings are consistent with high stress, high wear conditions and thin polyethylene components.

These results indicate polyethylene wear and damage is expected to be a key factor in limiting the survivor-ship total shoulder replacements and that polyethylene damage and wear in total shoulder replacements may be higher than that found for either total hip or knee replacements.

Besides the numerous variations of TKR designs addressing fixation, wear, or specific indications, there are variations from competing design philosophies such as conformity and shape of the articulating surfaces and mobile versus fixed bearing designs. With the same resected ACL and retained PCL ligament combinations and similar surgical procedure, the subset of different implants for these very indications should be expected to produce only minor variations in kinematics. This study set out on a comprehensive series of detailed and intricately controlled in-vitro tests to examine this hypothesis. Six different posterior cruciate retaining medium size knees from different manufacturers were used. Four were fixed bearing condylar types of low to high constraint; and two mobile bearing ones which allowed rotational and translational freedom, one fully and one partially conforming. The implants were aligned according to the manufacturer’s recommendations and subjected to the same ISO force-control simulation. The kinematics captured from the averaged simulated cycles of walking showed AP displacement contained within an envelope of 4 mm for most of the stance phase. This increased with most to a maximum range of 5mm just before toe-off at the end of the stance phase. In rotation, the designs showed ranges during stance from about 2–13 degrees. The kinematics from the different implant designs were thus significantly different; a controversial answer regarding the hypothesis posed. This means the “performance” must be different between these implants if installed “ideally” on the same patient with the PCL retained. Studies are worthwhile to determine if these differences in performance are reflected in clinical functional conditions.

Introduction: Mid-term follow-up has demonstrated good implant longevity for titanium fiber mesh and sintered bead designs, but few reports exist demonstrating the results of titanium plasma spray coated acetabular components in primary THR.

Methods: Between 1992 and 1995, a single surgeon performed 305 non-cemented primary THA’s in 260 patients. The selection criteria for non-cemented fixation were age younger than 65 and/or good bone quality. The hemispherical titanium plasma sprayed acetabular components were implanted with under reaming of 2 mm. Solid shells were used if a snug fit was attained with the trial. Screws were used to supplement fixation based on the surgeon’s judgment. The polyethylene liners were machined molded from ram extruded Hi-fax 1900H polyethylene resin gamma-sterilized in air or argon (inert) gas with elevated walls and locked into the shell via a Ring-Loc mechanism. These were mated with a 28mm cobalt-chrome femoral head and modular femoral component of metaphyseal-diaphyseal fit design with proximal titanium plasma spray porous coating. 15 patients have died, and 35 patients were lost to follow-up, leaving 225 hips in 210 patients that constitute the study cohort. The mean age was 55 years (range 24 – 60 years), and average.

Results: From this cohorts of patients, seven hips have been revised, two for infection, one for instability and four for osteolysis. The remaining patients had an average HSS score of 38 out of 40 at recent follow-up. Radiographically, the average cup inclination was 38.8 degrees. Eight hips had one zone interface lucencies, while three had two zone lucencies. There were no cases of continuous interface radiolucency or failure to achieve bone ingrowth. Nine hips demonstrated osteolysis, mostly in zones 2. The acetabular components in the cases with osteolysis were shells with unfilled screw holes in 3 and shells fixed with screws in 6. No osteolysis was detected in cases with solid hemispherical acetabular shells.

Discussion: Hemispherical titanium plasma sprayed ace-tabular components have achieved excellent durability at medium term follow-up, with a low incidence of fixation failure or osteolysis, and a low re-operation rate, even in a young, active group of patients. However, shells with screw holes appear to predispose to osteolytic lesions.

Introduction: The objectives of this study were to evaluate acetabular bone deficiency in revision THA with a simple classification on the anteroposterior pelvis radiograph and correlate the results of cementless hemispherical porous coated cup and cancellous bone graft reconstruction.

Methods: 70 acetabular revisions reconstructed employing large ‘jumbo’ porous coated cups with cancellous allo-grafting were evaluated at a mean follow-up of 5 years (range 2 – 10 years). During this time period 7 additional acetabular reconstructions required impaction grafting, cage reinforcement and cemented cups. Pre- and postoperative measurements of acetabular bone loss and the position of the revision component were performed with respect to a previously described triangle defining the placement and size of an idealcup. Impaction bone allo-grafting techniques were employed to fill defects. A minimum of 40% implant contact to host bone, especially in the weight-bearing dome region was attained in all cases and a minimum of 2 screws supplemented fixation to the ilium. Clinical evaluation comprised the HSS score and a patient assessment questionnaire (PAQ). Radiographically, cups were examined for filling of defects, ingrowth, graft consolidation, and stability.

Results: The mean HSS score improved from 18 to 33 out of a maximum of 40. The mean superior bone defect was 18 mm (range 10 – 25mm) and the mean medial bone defect was 7 mm (range 0 – 22mm). All the cement-less acetabular components were bone ingrown with the exception of one stable fibrous union. Allograft incorporation occurred at a mean of 7 months after surgery. Neither the status of Kohler’s line nor the Paprosky class correlated with eventual radiographic or clinical results.

Discussion: We present a simple method of evaluation of acetabular bone deficiency on the A-P pelvis radiograph employing a triangle that locates the ideal center of rotation of the hip. Superior bone loss upto 25 mm and medial migration as much as 22 mm has been successfully reconstructed employing impacted, cancellous allograft, large porous coated hemispherical Cementless acetabular components and screw fixation with excellent outcomes at intermediate-follow-up. Larger defects necessitate complex reinforced cage reconstruction.

Numerous studies have reported on the effects of modular insert design on stress at the tibial/femoral articular surface. However, while the insert / tibial component surface (“backside”) wear and motion have been investigated, backside stress is not well delineated. Because stress may be related to observed backside damage, this study addressed the backside stress response to insert thickness, material, and articular geometry.

Twelve Natural Knee II tibial inserts (Sulzer Orthopedics Inc.) with three thicknesses (6, 12.5, and 18.5 mm), two materials (Durasul and 4150 UHMWPE), and two types of condylar geometry (congruent and ultra-congruent) were tested. Fuji film was placed between the baseplate and insert. A femoral component was loaded onto the insert in axial compression at four times Body Weight. The film was scanned into Adobe Photoshop to measure mean and peak luminosity, which was converted into stress. Analysis of Variance was performed with main effects and all two-way interactions to determine significance.

The mean stress ranged from 0.61 to 3.92 MPa and the peak stress ranged from 2.17 to 10.4 MPa. Insert thickness significantly influenced both mean (p=0.001) and peak (p=0.001) backside stress. Stress for the 6 mm inserts (7.17 MPa mean, 9.91 MPa peak) were approximately 2.1 times the 12.5 mm inserts (3.47 MPa mean, 4.66 MPa peak), and were approximately 2.6 times the 18.5 mm inserts (2.74 MPa mean, 3.71 MPa peak). There was not a significant effect on mean or peak stress from material or condylar geometry. None of the interactions were significant.

This study provides two important contributions. First, it establishes the backside stress magnitude during simple loading. Second, the relationship between backside stress and the insert thickness is experimentally quantified. Understanding this stress magnitude and response may be important to controlling observed in-vivo backside damage.

We have been using a Charnley type hip prosthesis with an alumina ceramic head. Three sizes of alumina head, 28, 26 and 22mm, were employed and the Ortron 90 Charnley total hip prosthesis was used at the same period. The objective of this study was to compare the survival rate and the wear rate of those four groups. There were 90, 62, 322 and 88 hips in 28, 26, 22mm alumina head and 0rtron 90 head group. Average age at operation was 49.5, 57.8, 58.0 and 60.6, respectively. A 28 mm prosthesis was indicated for relatively young patients. The mean duration of follow-up was 156, 97, 49 and 110 months, respectively. Twenty patients were chosen at random for each of four groups and the linear wear as seen on X-ray film was measured every two years with a computer and scanner.

Results: The average linear wear rate (mm/yr) was 0.179 for the 28mm, 0.112 for the 26mm, 0.115 for the 22mm alumina head and 0.075 for the Ortron 90 head. The difference between the 28mm group and the other three groups was analyzed statistically. The Kaplan-Meier survivorship analysis, with revision for aseptic loosening as the endpoint, showed the survival rate of the 28mm group appeared to be inferior to that of the other three groups.

Discussion: Our study showed that the wear rate of the 28mm alumina group was highest because low grade alumina was used. In addition, the polyethylene socket used for the 28mm group was thinner than that for the other groups. No clinical superiority of ceramics to metal in terms of polyethylene wear can be shown in this study. A randomized prospective study should be carried out to determine whether an alumina ceramic head is clinically superior to a metallic head in terms of polyethylene wear.

Introduction: Analyses of the 3-D kinematics of TKA in vivo using the x-ray image matching techniques have been widely reported. However, the accuracy of those techniques has seemed not to be discussed enough. To demonstrate more accurate technique for those analyses, we developed the new calibration flame to detect the geometry of the x-ray source and more accurate image matching methods.

Materials and methods: A calibration flame was composed of four ball bearing markers. First, the optimal distributions of those ball markers were determined by computer simulations, and then, using the high-resolutional computed radiography (CR) of a metallic ball taken with the obtained optimal calibration flame, the resolving power of three degrees of freedom (DOF) translations were calculated. Next, the computer-synthesized projected images of the femoral component of TKA were calculated using the estimated x-ray source geometry and experimentally measured geometric data of the prosthesis when the full six DOF poses of the prosthesis were calculated. Matching the computer-synthesized images with the extracted and binalized 2-D CR images of the prosthesis was done automatically using computer in order to minimize the exclusive OR (XOR).

Results: The geometry of the x-ray source was estimated with accuracy of below 0.5 mm in computer simulations. The CR images of the prosthesis were matched with the computer-synthesized images until the XOR reached under one pixel and then, the accuracy of below 1.0 mm translations and 1.0 degrees rotation were recognized for the resolving power of six DOF poses of the prosthesis.

Discussion: The more accurate measurement of full six DOF poses is indispensable to estimate not only the 3-D kinematics but also the contact stresses or predicted polyethylene wear on TKA in vivo. The new calibration flame and the image matching technique we developed appear to be effective for analyses of TKA in vivo.

Introduction: Our previous study1) suggested that addition of vitamin E(dl-α-Tocopheror) at the grain boundarie of UHMWPE dramatically prevented delamination destruction. This study examined the microscopic and macroscopic mechanical performances of the vitamin E added UHMWPE by using micro indenter testing and high-speed tensile testing.

Methods: UHMWPE powder (GUR1050, Ticona) was directly molded at 10MPa with and without Vitamin E (DL-α-Tocopherol, Wako Pure Chemical Industries. Ltd.) addition. The Vitamin E was compounded to UHMWPE powder in air using a blend mixer. Gamma-ray irradiation (a dose of 25kGy) was performed on each group at room temperature in air, and then, the specimens were aged at 80°C for 23 days. Hardness at grain boundary was measured using dynamic micro indentation testing machine (Shimadzu Dynamic Ultra Micro Hardness Tester, DUH-200) where triangular-pyramid indenter with 115 degrees point angle was used. High-speed tensile testing was performed to dumbbell-shaped test specimens (JIS K7113 No.2, thickness=3mm) with crosshead speed of 1000 mm/min (corresponding strain rates : 0.4/s).

Results and discussion: Results of micro indenter test showed that the dynamic hardness at grain boundary was higher than that in grain and was increased by gamma irradiation. This hardening at grain boundary was reduced by adding vitamin E. Results of high-speed tensile test showed no significant change in Young’s modulus and strength by the vitamin-E addition. However, the elongation at break was increased to more than 10 times as much as that of virgin (aged) UHMWPE.

These results suggest that mechanism for the prevention of delamination by vitamin-E-addition is caused by increased elongation at break by increasing toughness at grain boundary. The addition of vitamin E is a simple and extremely effective method to prevent destruction of UHMWPE joint component.

Bankston et. al. reported that the clinical wear rates of molded acetabular cups was 50% less than a group of machined UHMWPE cups. However, due to covariables between groups including different femoral stems, cement technique, polyethylene resins and surgeons, unequivocal attribution of the low wear rates to direct molding could not be made.

In order to more directly assess the benefits of directly molded acetabular cups vs. machined cups, we report the comparison of hip simulation wear rates of machined and directly molded cups. These simulator results will then compared to two recent clinical reports on molded and machined cups of the same hip stem and cup design. The molded cups were made from 1900 resin and gamma sterilized in an inert atmosphere. The machined cups were made from HSS reference UHMWPE (4150) and gamma sterilized in air. The molded 1900 cups had a 55% lower wear rate after 5 million cycles on the hip simulator (14 v. 31mg/million cycles). Ranawat reported the average linear head penetration rate for 235 direct-lymolded, all polyethylene, cemented cups at a mean follow-up time of 6 years was .075mm/year. This is 56% lower than the rate of .17 mm/year he reported previously for the machined, uncemented metal-backed cups of the same design. These results provide further evidence that directly molding acetabular cups can provide wear rates over 50% less than machined cups both in both clinical and hip simulator evaluations. It is interesting to note based on other reports, that there is no osteolysis at 10 years of follow-up when the wear rates are < 1mm. The clinical and simulation wear rates reported here for the directly molded cups are within this performance range.

Purpose: Prosthetic arthroplasty is the most common method of reconstruction of segmental bone defects following resection of bone sarcomas about the knee. The purpose of this study was to determine the survivorship of the reconstructions in short- and long-term follow-up.

Methods: A retrospective study was performed on all patients diagnosed with a bone sarcoma between 1984 and 1995 who were treated with a limb-sparing osteoarticular resection and rotating hinge prosthetic knee arthroplasty. Prosthetic survival was calculated with endpoints of analysis based on any event, any prosthesis-related event and aseptic loosening of the prosthesis, which led to prosthetic revision, removal or limb amputation.

Results: A total of 154 reconstructions were performed involving the distal femur (n=111) and proximal tibia (n=43). The median resection length was 155 mm (105–250mm) for the distal femur and 117 mm (85–150 mm) for the proximal tibia. All implants were fixed with polymethylmethacrylate cement. Early complications (within one year postoperatively) developed in fewer than 2 % of patients. Aseptic loosening accounted for the majority of events resulting in prosthetic failures (distal femur = 17 [median failure 34 mos]; proximal tibia = 10 [median failure 100 mos]). Polyethylene bushing wear was observed in seven patients (median time to replacement = 156 months).

Conclusion: The early outcome of prosthetic arthroplasty was extremely favorable supporting this method of reconstruction following excision of high-grade bone sarcomas about the knee. Long-term survival of these prostheses is suboptimal and can be anticipated to be poor for the proximal tibia. Aseptic loosening continues to be the primary cause of prosthetic failure about the knee.

Polyethylene wear debris in TKA arises from several sources, including the tibiofemoral articulation and the interface between the backside surface of the tibial insert and the metal tibial tray. In this study we identify a new source of abrasive damage to the polyethylene bearing surface: impingement of resected bony surfaces, osteophytes and overhanging acrylic cement on the tibial bearing surface during joint motion.

One hundred forty-eight tibial components of 24 different designs in a retrieval collection were examined. A digital image of the articular surface of each insert was recorded. The presence, location and projected area of abrasive wear to the non-articulating edges of the insert were assessed using image analysis software.

Significant abrasive wear was observed in 24% of the retrievals with cemented femoral components and 9% from non-cemented components. Of the retrievals exhibiting this abrasive wear mode, 46% experienced multiple site damage. The average damage area for each individual abrasive scar was 78±11mm^2. Within the group of worn inserts, the abrasive scars were seen with a frequency of 69% on the extreme medial edge, 19% on the extreme lateral edge, 38% on the posterior-medial edge and 23% on the posterior-lateral edge. In posterior stabilized components with an open femoral box design, scarring of the superior surface of the tibial post was also observed. This proposed mode of damage was confirmed with several retrieved femoral components containing either fixed cement protruding from the posterior condyles, from the medial and lateral edges or osteophytes embedded in the posterior capsule. The corresponding inserts exhibited significant abrasive scarring at those locations.

We have observed a previously unrecognized source of polyethylene damage resulting in gouging, abrasion and severe localized damage in cemented and uncemented total knee replacement. Clearly, acrylic cement, in bulk or particulate form, often contributes to severe damage of the tibial surface and improvements to instruments and techniques for cementing are needed to prevent this wear mechanism.

Introduction: We compared the discrepancies between postoperative femoral component and the preoperatively predicted postoperative femoral component anteversions from CT data in cases of cementless THA, in which custom-made femoral components prepared from CT data were inserted directly without reaming or broaching.

Materials and methods: The subjects were 44 females (51hips) and 11 males (11 hips) with an average age at surgery of 54 years (range, 21–74). The average duration of follow-up was 44 months (range, 24–75). The femoral component was designed from 2 circles showing the corner of the medial and lateral rims of the component along the medial and lateral inner cortex on each CT slice. The anterior and posterior rims of the component were designed as lines connecting the 2 circles. From a CT slice of the planned osteotomy site and a slice passing through the knee, the preoperative femoral neck anteversion was measured. The postoperative femoral component anteversion was measured from the CT slice passing through the center of the ball and the slice passing through the knee.

Results: The mean discrepancy between the postoperative femoral component anteversion and the preoperatively predicted postoperative anteversion was 1.9° (range, −29.5–38). The average preoperative Harris hip score was 44 points (range, 17–80). At the most recent follow-up, the score was 88 points (range, 51–98). Sixty-one hips were evaluated as bone-ingrown fixations and one hip was evaluated as a stable fibrous fixation. There were no loosed femoral components.

Discussion and conclusion: There were 22 hips whose discrepancy between the postoperative femoral component anteversion and the preoperatively predicted postoperative anteversion was over 10°. However, the rotational angle on insertion did not influence the stability of the custom-made femoral component in this short-term follow-up survey. This probably indicates the effectiveness of the non-reaming or non-broaching technique.

Malfunctioning of Total Knee Replacements is often related to patella-femoral problems. As the patella groove guides the patella during flexion, the difference between anatomic- and prosthetic groove geometry may be of major influence concerning patella-femoral problems. This study focusses on the orientation or direction of the femoral patella groove, relative to the mechanical axis of the femur. Literature shows a controversy in measured groove orientation: Eckhoff et al. (1996) have measured a lateral groove, and Feinstein et al. (1996) have measured a medial groove, relative to the mechanical axis. Current femoral knee components have a lateral, or neutral directed patella groove. As most TKA surgical techniques subscribe an exorotation of the femoral component during implantation, the prosthetic in vivo situation will show a lateral groove. The objectives were to clarify the described controversy and to determine whether there is a difference in anatomic- and prosthetic groove orientation, which might cause patella-femoral problems.

The patella groove orientation of 100 human femora was measured using a 3-D measurement system. A spherical measurement probe was moved through the groove, starting at the notch and finishing at the cartilage edge, to simulate patella motion. The patella groove angle was defined as the angle between the mechanical axis and the measured groove points, in the frontal plane. A medial patella groove angle of 1.8±2.6° was measured. An implanted situation of a femoral component with neutral groove showed a lateral groove angle of 1.3°. An implanted situation of a femoral component with assymmetrical groove showed a lateral groove angle of 2.6°. The authors measured a medial oriented patella groove. This anatomical groove orientation is in contradiction with current femoral knee component design and surgical practice, because that results in a lateral oriented groove. This difference in anatomic- and prosthetic groove orientation may be a cause of patella-femoral problems.

Purpose: Osseointegration is crucial for favorable outcomes after total hip arthroplasty (THA) using cement-less femoral components. Osseointegration is recognized on radiographs as the endosteal spot weld, which is the bony bridge between the implant and surrounding bone (Engh et al, CORR, 1989). The purpose of this study is to evaluate the clinical and radiographic results for patients who had hydroxyapatite (HA)-coated rough surfaced implants compared with those who had identical implants without HA-coating at three-year minimum follow-up.

Methods: Ninety-one patients, one hundred and two hips who had primary THA with titanium arc sprayed rough surfaced femoral implants were retrospectively studied. Sixty-four hips had received HA-coated implants (HA) and 38 hips had an identical component but without HA (Non-HA). Radiographical parameters analyzed included 1) endosteal spot welds, 2) radiolucent lines, 3) calcar responses, 4) pedestal formation, 5) implant loosening, 6) endosteal osteolysis.

Results: At a minimum follow up of 3 years after operation (mean, 5.5 years), the mean Harris hip score was 89.4 points in the HA group and 89.0 points in the Non-HA group. The radiographic analysis did show the significantly earlier appearance of the endosteal spot welds in HA group. The spot welds at 1 and 2 year after operation were present in 48% and 70% of HA group, while 13% and 42% of Non-HA group. There was no significance at 3 years (71% vs 66%). More than 80% of the spot welds were seen at Gruen zone 6 in the both groups. No differences were noted regarding the radiolucent lines, calcar response, pedestal formation between the groups. There were no implant loosening and osteolysis in both groups.

Conclusions: These results suggest that the use of HA-coating does provide improved fixation in the early periods and the possibility of improved durability.

Introduction: Fibroin sponge is purified silk protein from which high-strength gel sponge can be produced. The purified fibroin sponge causes no immune response. This study evaluates unique performances of the fibroin sponge for articular-cartilage regeneration, and mechanical properties of regenerated cartilage were also measured.

Methods: Refined silk yarn was dissolved in 9M lithium bromide aqueous solutions, and was frozen in −20& #8451 freezer for 12 hours. Hydrogel sponge was formed under the room temperature. Articular cartilage slices were taken from the proximal humerus, distal femur and proximal tibia of 4-week-old Japanese white rabbits. The cartilage slices cut into small pieces and were digested with 0.25% trypsin in DMEM containing antibiotics for 30 min at 37& #8451. After rinsing with Tyrode’s balanced solution and centrifuging at 180 G for 5 min, the chondrocytes were isolated with 0.25% collagenase for 8 h at 37& #8451. These cells were harvested and inoculated into the fibroin sponge. The constructs of the chondrocytes and the fibroin sponge were cultured in DMEM containing 10& #65285 FCS and 50mL L-ascorbate for 4weeks. Indentation test and dynamic visco-elastic measurement were carried out for these constructs.

Results and discussion: Cell density of the inoculated chondrocytes was increased to about five times as much as initial volume. This regenerated tissue was intensely stained with safranin-O fast green and showed a meta-chromatic reaction. This also stained positively with immunostain for type & #8545 collagen, but negatively with immunostain for type & #8544 collagen. Mechanical tests showed that time constants of compressive creep and E’ values were increased with cultivation days, and the peak value and frequency of tan& #948 shifted to a lower amount. The change in dynamic visco-elastic properties of the regenerated cartilage is caused by synthesis of extracellular matrix.

How total knee replacements (TKR) articulate is directly related to their functional and wear performance. Recently, significant interest has concerned the center of axial rotation, or pivot point. Since the tibia exhibits internal rotation with knee flexion, the pivot point describes condylar translations: a medial pivot implies posterior lateral condylar translations with flexion, a lateral pivot implies anterior medial condylar translations with flexion.The purpose of this study was to describe the location of the pivot point, as related to TKR design, in a large number of knees studied under dynamic weight-bearing conditions.

Two hundred and four well functioning TKR’s were studied using fluoroscopy as subjects performed a stair ascent. There were 131 cruciate retaining fixed bearing knees (11 designs), 33 mobile bearing knees (5 designs), and 40 posterior stabilized knees (4 designs). CAD model based shape matching was used to determine 3D knee kinematics and the pivot point location from 21,837 images. The pivot location was described as a percentage of tibial width, −50% (lateral) to +50% (medial).

Posterior stabilized knees exhibited medial pivots (mean +14%, +7% to +30%) while cruciate retaining (mean −9%, −35% to +21%) and mobile bearing knees (mean −20%, −48% to +5%) exhibited lateral pivots on average (p< 0.001).

How a TKR design provides A/P stability dictates the location of its center of axial rotation and the A/P motions of the condyles. As the relationship between constraint and in vivo motions becomes clearer, TKR designs can be enhanced to achieve more favorable functional and wear performance.

Wear of the underside of modular tibial inserts (“backside wear”) has been reported by several authors. However, the actual volume of material lost through wear of the backside surface has not been quantified. This study reports the results of computerized measurements of tibial inserts of one design known to have a high incidence of backside wear in situ.

A series of retrieved TKA components of one design (AMK, Depuy) with evidence of severe backside wear and extrusions of the polyethylene insert were examined. The three-dimensional surface profile of the backside of each insert was digitized and reconstructed with CAD software (UniGraphics). The volume of material removed was calculated from the volume between the worn backside surface and an “initial” surface defined by unworn areas.

Computer reconstructions showed that in all retrievals, the unworn surface of the remaining pegs, the rim of material extruded over the medial edge and unworn surfaces on the anterior-lateral edge all lie in a single plane. This demonstrates that the “pegs” present on the backside of these inserts correspond to residual, unworn protrusions remaining on each retrieved component and do not represent cold flow extrusions through the base plate holes. The average volume of material lost due to backside wear was 608mm^3 ± 339mm^3 (range:80–1599 mm^3). This corresponds to an average loss of 569mg and an average linear wear rate of 103mg/year, based on the time in situ for each implant.

The volume of material removed due to backside wear is significant and is of a magnitude large enough to generate osteolysis. Our results indicate that the appearance of pegs on the underside of components with screw holes on the baseplate are not due to creep, but instead are due to severe wear of the insert. The mechanisms of material removed due to pitting and burnishing actually produce debris of a size more damaging in terms of osteolysis than wear at the articulating surface making it clear that significant improvements in implant design are needed to prevent backside wear and osteolysis.

Condylar liftoff can undoubtedly occur with total knee replacements (TKR); it occurs in the surgeon’s hands and has been shown to occur in vivo. However, the reported incidence of condylar liftoff and the implications for articular surface damage require further scrutiny. A three-part argument is made that the incidence of condylar liftoff has been overstated, and there is little direct evidence that condylar liftoff is a significant factor in the wear performance of coronally flat-on-flat TKR’s. First, an analysis of fluoroscopic measurement errors based on the uncertainty in measuring varus/valgus angles (the parameter used to determine liftoff) reveals that the standard error for liftoff measurements is 1.2mm, nearly identical to the mean liftoff value in recent published reports. Second, because most TKR’s have some anterior/posterior curvature of the tibial insert, any axial rotation of the knee induces a varus/valgus angulation that can be interpreted as liftoff, even though the condyles remain in contact. Third, condylar liftouff has been used to justify the need for coronally round-on-round geometries, yet an analysis of 100 unselected retrieved tibial inserts from three coronally flat designs reveals no difference in wear type, magnitude, severity, depth, or symmetry between the medial and lateral aspects of the tibial inserts. Although condylar liftoff certainly can occur in vivo, an argument can be made that the incidence of liftoff in experimental studies has been overstated, and that there is little evidence from retrievals that contemporary coronally flat-on-flat TKR’s are uniquely susceptible to articular damage from condylar liftoff.

The limiting factor in the growth of RSA as a wide spread clinical tool is the man-hours needed to run a study. Calibration takes more than half of the processing time. The aim of this study is to develop automatic calibration method applicable to the grid and line patterns common in all RSA systems. This method uses a Harris Corner detector to find candidate positions on an image one 16th the original area (16 times quicker). Canny edge detection in regions of interest around the candidate positions on the full size image produce circular edges for marker-balls. A conic section is fitted to this edge using the Bookstein method to produce an accurate estimation of position to a local accuracy of 0.01 mm. Scanner distortion was modeled using a stabilised B-spline mesh to produce global accuracy of 0.03mm. A model based pattern recognition method can be used to label the marker-balls correctly. For sets of 4 marker balls a Homography was calculated and used to predict the positions of the other points in the grid. If supporting marker-balls are found in the predicted positions, they are counted. The four-point set, which returns the greatest number of support marker-balls, is the best estimate of a grid. Reference markers in the grid are used to localise it.

The method had a ninety- percent success rate on a set of 20 clinical X-rays. In two X-rays not enough marker-balls were visible due to a poor exposure. It finds marker-balls in a 15-MB image in 50 seconds on a 180 MHz silicon graphics O2. Labelling speed depends on the number of marker-balls and is 45 seconds per group of 50. This method is widely implementable, as it requires just the 3D positions of the markers in each plate of the calibration object for input.

Polyethylene wear remains an important cause of failure in knee replacements. Retrieval studies, simulators and simple X-ray methods produce wear data that may be inaccurate or unrealistic. We have developed an accurate RSA system for measuring wear in-vivo. Using this system we have found wear rate in a fixed bearing TKR to be about 0.1mm/yr[1]. In this abstract we extend the study to fully congruent mobile bearings.

Four Oxford uni-compartmental knee replacements, with excellent clinical results were studied ten years after implantation. RSA X-rays were taken in double leg stance with the knee in full extension and 15 and 30 degrees flexion. Following RSA calibration, silhouettes of the components on the stereo X-rays were extracted using a Canny edge detector and were matched to silhouettes projected using CAD models to determine the 3D component position. The average minimum thickness of the bearing was determined and was compared with the measured minimum thickness of 14 unused bearings to calculate linear penetration.

The average linear penetration after average 10 years implantation (range 8.5 to 10.25 years) was 0.16 mm (SD 0.13 mm). The average penetration rate was 0.017 mm/year (SD 0.011 mm/year). The maximum linear penetration rate was 0.027 mm/year.

The penetration rate is similar to that obtained in a retrieval study [2]. Compression of the bearing is minimal due to 6sqcm of contact area. This study therefore demonstrates that polyethylene wear on the upper and lower surfaces is minimal in fully congruous mobile bearing knee replacements.

The low contact stress and self-aligning properties of mobile bearing total knee replacements (TKR) make them an increasingly popular implant choice worldwide. Two variations on the mobile bearing knee concept have been commonly adopted: systems that retain the posterior cruciate ligament (PCL) and provide free rotation and translation (RT) of the mobile bearing, and systems that sacrifice the PCL and provide for rotation only (RO) motion of the mobile bearing. The purpose of this study was to evaluate the in vivo kinematics of these two types of mobile bearing TKR during gait, stair, and two deep knee flexion activities.

Twelve patients (6 RT, 6 RO) with unilateral mobile bearing knee arthroplasty and excellent functional outcomes at least one year after TKR were studied. Fluoroscopic images of the knee were acquired as patients walked on a treadmill, ascended a step, performed a deep knee bend, and knelt to maximum flexion. Knee kinematics were derived from CAD model based shape matching techniques.

The RT knees exhibited greater posterior translation of the femur on the tibia during early stance in gait (RT: 5mm vs. RO: 2mm) and during knee extension during stair ascent (RT: 5mm vs. RO: 1.5mm). There were no differences between the two groups in the flexion angles achieved during deep knee bend or kneeling.

Although there were no significant clinical or functional differences in these patients, the RO knees exhibited smaller tibio-femoral translations and less intersubject variability in knee kinematics during dynamic weight-bearing activities.

Introduction: The excellent character of cross-linked polyethylene on wear has been reported from basic researches. However, few clinical results were seen about irradiated polyethylene sockets. This presentation reports a long-term clinical result of irradiated polyethylene sockets.

Material and method: Two 100M-rad gamma irradiated polyethylene sockets were retrieved, each 25 and 27 years after implantation. Socket joint surface were scanned by 3-D scanner and analyzed. On the other hand, ten patients had total hip replacements with 6.5M-rad irradiated polyethylene sockets. Anterior-posterior and lateral radiograph were taken and the movement of the head to the socket was analyzed by 3-D wear measurement software GAWDI. The results were compared to conventional polyethylene sockets of matched patients.

Results: Wear of the 100M-rad sockets were 0.23mm/ 25yrs and 0.46mm/27yrs respectively. The direction of wear was observed over the whole surface. Wear of the conventional polyethylene socket retrieved 15yrs after implantation were 2.54mm/15yes and 1.76mm/12yrs. The wear were toward weight bearing directions.

The average movement of heads in 6.5M-rad irradiated polyethylene sockets was 0.22mm one year post operation and its direction was toward backside of patients’ body. The average movement of conventional polyethylene sockets was 0.24mm one year post operation and its direction was just the same as irradiated polyethylene sockets.

Discussion: The difference of long term results between 100M-rad irradiated polyethylene and conventional one was obvious. A definite wear path way was observed on conventional polyethylene sockets. However, it was ambiguous on 100M-rad irradiated polyethylene because it was small or it did not exist. No remarkable difference was observed in short term after operation between 6.5M-rad irradiated and conventional sockets. The present analysis suggests that a high dose irradiated polyethylene socket may benefit a good long-term clinical result.

Introduction: Previous in vivo kinematic studies have assessed total knee arthroplasty (TKA) motion under weight-bearing conditions. This in vivo study analyzed and compared posterior cruciate retaining (PCR) and posterior stabilized (PS) kinematics under passive and weight-bearing conditions in subjects implanted with both a PCR and PS TKA.

Methods: Eighteen subjects were implanted with a PCR and a PS TKA, by a single surgeon using a similar surgical technique. Both implant designs had similar condylar geometry. Femorotibial contact positions for all 18 subjects (PCR and PS), implanted by a single surgeon, were analyzed using video fluoroscopy. Each subject,while under fluoroscopic surveillance, performed a weight-bearing deep knee bend and a passive, nonweight-bearing flexion. Video images were downloaded to a workstation computer and analyzed at varying degrees of knee flexion. Femorotibial contact paths for the medial and lateral condyles, axial rotation and femoral condylar lift-off were then determined using a computer automated model-fitting technique. Femorotibial contact anterior to the tibial midline in the sagittal plane was denoted as positive and contact posterior was denoted as negative.

Results: Under passive and weight-bearing conditions, the PCR TKA experienced more paradoxical anterior translation than the PS TKA. Under passive, non weight-bearing conditions, the PS TKA, on average, experienced 3.5 mm of posterior femoral rollback, compared to only 0.6 mm for the PCR TKA. Under weight-bearing conditions, the PS TKA experienced only 0.6 mm of posterior femoral rollback, compared to 0.9 mm for the PCR TKA. The maximum anterior slide was 10.0 mm for the PCR TKA and only 2.7 mm for the PS TKA. There was greater variability in both the PCR and PS anteroposterior data. Subjects having a PCR TKA experienced more normal axial rotation patterns. Sixteen of 18 PCR TKA experienced a normal axial rotation pattern under weight-bearing conditions, while only 9/18 PS TKA experienced a normal pattern. Nonweight-bearing, passive axial rotation patterns were more abnormal for both groups than the weight-bearing patterns. The greatest difference between passive and weight-bearing conditions occurred in the condylar lift-off data. Under passive conditions, both TKA groups experienced significantly greater magnitude and incidence of condylar lift-off. The maximum amount of condylar lift-off under passive conditions was 5.0 mm for the PCR TKA and 6.4 mm for the PS TKA.

Discussion: This is the first in vivo kinematic study to assess a comparison between PCR and PS TKA implanted by the same surgeon in the same patient. Subjects in this study experienced more abnormal kinematic patterns, especially condylar lift-off, when tested under passive, nonweight-bearing conditions. Subjects having a PS TKA experienced less variability in their kinematic data, but PCR TKA, on average, experienced more normal axial rotation and less condylar lift-off.

The growing interest in the use of metal on metal bearings in the treatment of end stage hip arthritis in the young has raised the need to monitor metal ion levels in these patients. Blood levels are good indices of the safety of these devices. Total wear/corrosion over a given time period is best estimated from 12 or 24-hour urine collections. Whole blood samples of 52 patients with metal on metal hip arthroplasties were analysed for levels of chromium, cobalt and molybdenum using high-resolution induction coupled plasma mass-spectrometry. Fifteen of these were in an older age group (mean age 75.3years) and had metal on metal hip replacements performed 19–28 years before the assessment. The rest (37) were younger (mean age 52.9 years) and had hip resurfacings performed in the last 4 years. The results show higher levels of ions than those found in the normal population.

This agrees with other studies. However we found no significant difference between the levels in the older patients with THR and the younger patients with hip resurfacing. In another study, urine collections from 78 patients who had hip resurfacings in the past and are now at different postoperative durations (2, 4, 6, 8, 10, 12, 18, 24 and 36-month periods) were analysed for metal ions using the same technique. The mean levels show an increase compared to the preoperative values but this increase is not statistically significant.

The urinary excretion of cobalt in these groups have also been compared with the expected cobalt release due to corrosion in this alloy. They were found to rise above the corrosion levels only in the 8–12 month period, possibly due to “run-in” of the bearing. It can be concluded that the ion levels can be attributed mainly to corrosion and there is minimal contribution from wear.

An extra articular correction may be necessary in osteoarthritis with an important post traumatic or congenital deformity. In the last 5 years we performed 11 TKR associated with a tibial (9 cases) or a femoral Osteotomy (2 cases), in one time surgery. The average intra osseous deformity was 14°. The technical problems are different in varus and valgus knees.

1- Which type of osteotomy ? In varus knees with a tibial deformity (6 cases) we use a hight tibial valgus osteotomy with opening wedge. Pre operative planning with long standing X rays allows precise determination of the amount of correction needed. A rigide wire, driven up to the fibular head, is placed. A provisional wedge of the desired size (degree of correction) is maintened temporarily by a staple, which will be removed later. Once the correction has been performed and maintened, the standard instrumentation to implant the prosthesis is used. In valgus knees with a tibial deformity (2 cases) a hight tibial closing wedge osteotomy, and in valgus knees with a femoral deformity (2 cases), a low femoral closing wedge osteotomy, are used. In all cases a medial approach without any release and without fibular osteotomy is performed.

2- Which kind of prosthesis?

Two degrees of constraint are possible in fonction of particular needs.

Most of the time, a non-constrained PS articular implants will be used and when more constraint will be needed (in lateral instability), CCK-type articular surfaces will be choised.

In all cases, a stem will have to be, associated with the osteotomy (tibial or femoral). Different diameters will allow a good press-fit and if necessary, an offset stem will be used.

3- Associated osteosynthesis or not? Stability provided by the press-fit stem may allow not to use an osteosynthesis in most than 50% of cases. If a doubt remains about stability, a small plate can bee added on the medial tibial side of the tibia.

4- Which immediate post-op follow-up?

Full weight bearing will be immediate. A splint will be used only for walking during six weeks. A standard rehabilitation protocole will be followed. In our 11 patients with a short follow up (1 to 5 years) complications consisted in one hematom and one phlebitis. Post-operative alpha angle was 96° and beta angle 91°. TKR with an associated osteotomy seems to be a possible alternative when osteoarthritis is associated with an important extra articular deformity.

Metal on Metal bearings have functioned satisfactorily for up to 30 years without a full understanding of what shape the components were at the start, or as they were worn over time.

Modern metrology methods can use elegant computer driven coordinate measuring machines in both manufacturing and retrieval analysis as most manufacturers and laboratories do. This method however is fl awed in its ability to look at the much higher levels of resolution required for analysing these bearings. A method has been developed which will analyse to the sub micron deviances from roundness that the subleties of manufacturing can achieve, and allows an analysis of wear of explanted implants.

Both new and explanted Ring, McKee, Stanmore, Metasul and Resurfacing implants have demonstrated initial form variances that range from 1 to over 100 microns out of round. Roundness trace analysis has allowed linear wear on explanted implants to be measured from 0.5 to 150 microns. This represents combined head and cup linear annual wear rates from 2 to 65 microns per year.

Metal heads and cups are not manufactured as round as has been believed. The average wear rates over time for different Metal on Metal systems is not the same.

Introduction: Previously, in vivo kinematic studies have determined that posterior stabilized (PS) TKA experienced posterior femoral rollback during deep flexion, while posterior cruciate retaining (PCR) experience a paradoxical anterior slide during both gait and deep flexion. The objective of this present study was to analyze the in vivo kinematics for subjects implanted with a PS mobile bearing TKA to determine if there are any distinct advantages.

Methods: Femorotibial contact positions for ten subjects having a mobile bearing PS TKA, implanted by a single surgeon, were analyzed using video fluoroscopy. Each subject,while under fluoroscopic surveillance, performed a weight-bearing deep knee bend to maximum flexion and normal gait. Video images were downloaded to a workstation computer and analyzed at varying degrees of knee flexion. Femorotibial contact paths for the medial and lateral condyles, axial rotation and condylar lift-off were then determined using a computer automated model-fitting technique. Femorotibial contact anterior to the tibial midline in the sagittal plane was denoted as positive and contact posterior was denoted as negative.

Results: During a deep knee bend, subjects having the Sigma PS rotating platform experienced minimal motion of their medial condyle and posterior femoral rollback of their lateral condyle. On average, the subjects experienced −2.3 mm of posterior femoral rollback (PFR) of their lateral condyle. Nine of ten subjects experienced PFR of their lateral condyle. During gait, on average, subjects experienced minimal motion of their medial (0.8 mm) and lateral condyles (−0.4 mm) from heel-strike to toe-off. During a deep knee bend all ten subjects experienced normal axial rotation (average = 4.0°). During gait, 6/10 subjects experienced normal axial rotation, while four subjects experienced less than 0.8 degrees of reverse rotation. Only 1/10 of the subjects experienced greater than 1.0 mm of condylar lift-off during gait or a deep knee bend.

Discussion: Subject in this study experienced normal kinematic patterns during gait and a deep knee bend. Only one subject experienced greater than 1.0 mm of condylar lift-off, during a deep knee bend and gait. At the present time, it is uncertain if the excellent kinematic patterns for the subjects in this study were related to the chosen surgeon, surgical technique or implant design. If implant design was an influencing factor, subjects requiring a TKA may receive benefit from having a PS mobile bearing type TKA.

Development of the metal/ metal hip resurfacing began in 1989 with the first patient implantation in February 1991. In the first three years three methods of implant fixation were employed in a pilot study of 119 resurfacings and the optimum fixation was identified as Hydroxyapatite Coated (HA) uncemented cups and cemented femoral components.

From March 1994 until February 2001 the author has performed 1503 hybrid fixed resurfacing implants, 294 of the McMinn type (HA on Smooth Metal Cup) and 1209 Birmingham Hip resurfacings (BHR; HA on Porous Metal Cup). Mean age was 52.9 years, diagnosis – Osteoarthritis 78%; Dysplasia 7%; Inflammatory 2%; Avascular necrosis 5%; other 8%. In the 294 McMinn Resurfacings 8 have failed and 7 have been revised. Reasons for failure; 5 cup loosenings, two infections and one femoral head collapse in a patient with pre-existing avascular necrosis. High wear of the metal/ metal bearings, with altered metallurgy, is now presenting as a cause for concern with these McMinn resurfacings performed in 1996 where the metal was Solution Heat Treated (SHT) and Hot Isostatically Pressed (HIP). Patients from 1996 are exhibiting asymptomatic radiographic osteolysis and at revision metallosis is seen with high wear measured on the retrieved components. Laboratory studies have shown that SHT and HIP alters the carbide microstructure and increases wear on abrasive wear testing.

In the 1209 BHR’s 7 failures have occurred requiring revision. Reasons for revision – 4 femoral neck fractures, 2 infections and 1 collapsed femoral head from avascular necrosis. Implant fixation is reliable as judged by very low migration on an R.S.A. study. Bearing wear is very low as judged from wear analysis of explants as would be expected from the historically proven “As Cast” metal microstructure. Function is good as judged by the Harris Hip Score (mean 96.3 at 3years). Cumulative survival on all Hybrid fixed implants is 97% at 7–8 years.

Hip resurfacing, using metal on metal bearings with historically proven metallurgy using hybrid fixation, offers a viable treatment alternative for the young and more active patient with hip arthritis.

After a very short résume of his presentation in sept 2000 for the ISTA Conference in Berlin, the author looks briefly at the results of T.R.A.C knees after, what is now, four years of clinical follow-up.

Given the bad results this far regarding the femoropatellar joint and the uncemented version. M.D. François Pilon moves on to present an original concept, the latest evolution in knee systems: the rotary plateformed and posterior stabilised prosthesis, which offers a large congruence of polyethylene.

Originality of the newwave prothesis:

-Developement of a non-posteriorstabilised, fixed-plateau, prosthèses (GALICA, 8 yrs on !)

Clinical, X-ray follow-up system: All NewWave users can consult the computer Letterbox : newwave@groupe-lepine.com to have current results (up to the minute)

A NewWave reimplantation replacement prosthesis is at the moment on the drawing-board.

In four years time, Dr Pilon hopes to be presenting the real five year follow-up H.S.S. results of NewWave to the I.S.T.A..

Significance: Since DRG-based Medicare payments to hospitals, length of stay (LOS) after Total Knee Arthroplasty (TKA) has declined dramatically. This reduction was accomplished in part by transferring patients to DRG-exempt rehabilitation units. Despite the regular use and expense of inpatient rehabilitation after TKA, there have been no prospective studies defining its efficacy. Purpose: Determine the impact of inpatient rehabilitation on TKA outcome.

Methods: Prospective, observational, single surgeon, single facility design.Inclusion criteria:primary,cemented TKA for OA between 1998–1999. All postoperative and rehabilitative care dictated by clinical protocol. Subjects were evaluated pre-op, at 1,3 and 6 months post-op. Patient (demographics, comorbidities), psychological (depression, anxiety), surgical (implant type, fixation, alignment), resource utilization (LOS, outpatient/home PT visits, rehabilitation LOS), complications, functional (knee flexion, gait, assistive device, Knee Society Score (KSS)) and pain (visual analogue scale, medication use) data obtained. Principle outcomes were pain, knee flexion, function, KSS, number of PT visits.

Results: 125 knees, 56 bilateral. No patient lost to follow-up. Mean age 66 years (36–85). At six months follow-up, postoperative KSS score was 164.4(94–200), flexion 114.3(80–130), VAS 18(SD 21). Patients discharged to rehabilitation had significantly lower preoperative KSS scores (89, SD30) than those discharged to home (104.6, SD24.4)p=035. There were no other differences between groups. Patients discharged directly to home had a greater knee flexion (p=005), walk farther (p=024), climb stairs easier (p=036), and utilized less home physical therapy (p=030) than patients discharged to rehabilitation.

Conclusion: This study was unable to demonstrate a benefit of inpatient rehabilitation after TKA. However, patients transferred to inpatient rehabilitation were less functional before surgery than those discharged home. Further studies are needed to determine if these patients benefit from inpatient rehabilitation versus home care.

Introduction: Hospital accrediting organizations have recently emphasized the evaluation of and response to postoperative pain as the “fifth vital sign”. However, there are no prospective studies describing normal pain patterns after TKA to guide appropriate clinical responses. Similarly, there are no studies describing those at risk for unusual pain.

Purpose: To outline the pattern of normal recovery and identify factors predictive of significant pain after TKA.

Method: Prospective, observational, single surgeon design. Inclusion criteria: primary, cemented TKA for osteoarthritis. Clinical & radiographic measures obtained pre-op and at 1,3,6 and 12 months post-operatively. Predictive factors and post-operative outcomes included body mass index visual analogue scale (VAS), demographics, physical therapy, and component design, alignment and fixation. Psychometric testing included the Beck Depression Inventory and McGill Pain Questionnaire.

Results: 96 patients, 125 knees (mean age = 66, 55.2% women). Mean VAS at pre-op, 1,3, 6 and 12 month visits were 51.1(SD 23.8), 37.4(21.8), 27.0(22.2), 20.8(20.3), and 18.0(21.0), respectively. significant pain (VAS> 40) was reported by 61.51% of patients pre-op, 41.7% at 1 month, 24.0% 3 months, 16.7% 6 months, and 8.3% 12 months. There were no differences in pain based on the type of anesthesia, weight, age or gender. Preoperative elevated depression, anxiety and pain-related suffering descriptors predicted greater pain during the first 6 months after surgery, but did not ultimately affect recovery. Patients who had greater pain (VAS> 40) used more home and outpatient physical therapy (p=0.25).

Conclusion: Contrary to common beliefs, many patients (22%) still experience significant pain up to six months after TKA, despite absence of clinical or radiographic abnormalities. significant pain (VAS > 40mm) after six months may be indicative of an abnormal pain experience. Preoperative pain, depression and suffering are associated with increased early pain andutilization of therapy.

Introduction: Osteolysis of the pelvis secondary to polyethylene wear of uncemented acetabular implants has emerged as the most serious and challenging consequence of THR. A very large number of patients have and will continue to receive implants at the risk of being associated with osteolysis. The early detection of osteolysis allows the initiation of treatment programs that preserve bone stock. Because osteolysis occurs and progresses in the absence of clinical symptoms, appropriate follow-up surveillance must be instituted. Our initial study of the usefulness of CT scans in detecting clinically silent and radiographically unobservable osteolysis indicated that x-rays greatly understated the incidence and location of osteolysis. The purpose of this study was to determine the incidence of CT scan identifiable osteolysis in young, active patients with a single cup design and a minimum follow-up of 7 years.

Methods: Between 1990–1995, 117 hips (105 patients) underwent an uncemented total hip replacement with a patient-matched femoral component and a titanium plasma sprayed, multi-holed acetabular shell with a compression molded, polyethylene, irradiated in air. 57 patients underwent a CT scan using a metal subtraction software technique. All patients were classified based on their CT scans: Group I: no osteolysis; Group II: cavitary osteolysis; Group III: segmental osteolysis. All patients had standard AP, Frog – lateral and shoot-through lateral radiographs, performed at the time the CT scan was obtained.

Results: 37.2% of hips were in Group I, 53.5% in Group II and 9.3% in Group III. No patients in Group I had x-ray evidence of osteolysis (i.e. there were no false negative CT scans). 12% of patients in Group II had x-ray evidence of osteolysis. 22% of patients in Group III had x-ray evidence of osteolysis. There was no correlation between the incidence of osteolysis seen on CT scans with: 1) activity level; 2) age; 3) sex; 4) weight, and 5) size of acetabular component. There was no correlation between polyethylene wear measured using the Martel method and pelvic osteolysis. There was a correlation between the length of implantation and pelvic osteolysis. The average follow-up for patients in Group III was 105.5 months (range 85 – 115) vs. 89.4 months (57 – 117) for Group II and 81.5 months (51 – 112) for Group I. Of the patients with follow-up greater than eight years, 25% had Group III osteolysis. No patients have required revision or polyethylene liner exchange thus far.

Discussion: This study indicates that: 1) x-rays are an unreliable method for determining the presence. Location or extent of osteolysis, 2) the incidence of osteolysis based upon CT scans (Group II – III) is 63%; 3) Osteolysis, even if extensive (Group 3) is NOT associated with symptoms; 4) the pattern of osteolysis seen on CT scan strongly suggests that the presence of screws plays an important factor in the process; 5) CT scans are helpful in the planning process for acetabular revision. They allow the precise determination of the location and extent of osteolysis; 6) CT scans are also potentially useful for determining the impact of medical (e.g. alidronate) or surgical (e.g. bone grafting) treatment of osteolysis; 7) CT scans may be very helpful in assessing whether new polyethylenes are associated with reduced osteolysis.

The authors strongly recommend that: 1) a surveillance program be established for careful, regular follow-up of patients with THR in place more than 7 years; 2) CT scans be considered as part of that surveillance program, and 3) cups with screws NOT be used routinely in primary THR surgery.

Introduction: The modular IBPSII prosthesis was introduced in 1989 with modifications to the patello-femoral articulation and the posterior stabilized mechanism.

Methods: 100 consecutive IBPSII knee arthroplasties were followed prospectively. Age, gender, deformity and diagnoses were comparable to previous groups.

Results: Fifty-one knees were evaluated at 10 or more years with the Knee Society scores and radiographs. 14 were evaluated by phone. An additional 6 knees required revision and 29 were in patients who died. None were lost. Revisions were performed for instability (2 knees), sepsis (2), loosening from osteolysis (1), and stiffness (1). In the 10-year group, 12 patients required reoperations: Patellar revision for loosening (1), patel-lectomy for fracture (1), polyethylene exchange for dislocation of the spine and cam mechanism (3) and for dissociation (1), and arthroscopic resection of scar from the quadriceps tendon (patellar clunk) in 6 knees.

Conclusion: The smoother patello-femoral groove was associated with fewer patellar fractures, but resulted in scar on the quadriceps catching on the femoral component. The tibial spine was moved posteriorly from previous models to increase rollback. This resulted in dislocation of the spine and cam mechanism. One case failed due to loosening and extensive osteolysis presumably associated with modularity. The last two complications were not observed with earlier versions of this prosthesis. All complications occurred within the first five years.

It is well recognized that following excision of bone tumours around the knee, which often requires excision of the joint, cemented fixed hinged endoprosthetic replacements can give excellent results in terms of function (87%). However, for patients under 20 years of age the overall survivorship of distal femoral replacements in this age group is less than 45% at 10 years. To try and address this we have used HA ingrowth collars since 1989 and introduced the Smiles rotating hinge in 1991. In the younger patients we have also used uncemented prostheses using HA.

The HA collars at 70mm thickness are now standard protocol on all extremeity endoprosthetic replacements. We will present the results of retrieval specimens. We have also undertaken a study to determine the effect that HA collars and roating hinges have on enhancement of implant fixation. A survivorship and radiographic analysis has been carried out with three groups of patients: 1. Fixed hinge no collar. 2. Rotating hinge no collar. 3. Rotating hinge with HA collar

The selection criteria were all distal femoral replacements of patients who were over 16 years of age and had a cemented intramedullary stem. The study groups were consistent for age and amount of bone resected and all patients have been followed up.

Then SMILES (Stanmore Modular International Limb Salvage System) was first introduced in 1991 for use as a customized prosthesis in the treatment of malignant and aggressive bone tumours. However, the use of this pros-thesis has been extended to minimal customization, to be used in a situation of salvage surgery for the arthrosplasty, which has already undergone previous revision surgery. Between 1991 and 1997 32 SMILES prostheses were used in thismanner in 30 patients. 28 patients were available for review, all had a minimum of 3 years follow-up. The mean number of previous revision procedures was 2 and 6, average 2.6. There were 11 male and 19 female patients. The mean age at the time of the salvage procedure was 67 years (46 to 86). The mean age of the primary procedure was 57.8 (Range 43–71). The Knee Society score increased from 26 to 68 and the function score increase from 26 and 68 and the function score increased from 27 to 75. Average flexion improved post-operatively from 78 to 88 degrees. 84% of patients stated that they were pleased with the results in terms of pain and mobility.

We conclude that this prosthesis is a satisfactory alternative to complex reconstructions or amputation in the presence of infection, severe bone or soft tissue loss and has rendered acceptable results.

Hypothesis: 1. Increased wear results from modularity. 2. Modification of the patello-femoral articulation will decrease patellar fractures.

Materials & Methods: A prospective comparison of 100 consecutive Non-modular Insall Burstein Posterior Stabilized (IBPS) knee prostheses (1986–1989) with 100 consecutive modular IBPS II knee replacements (1989–1990). No patient was lost.

Results: IBI: Nine re-operations of which 6 were complete revisions: two for sepsis, one for tibial loosening, one for patellar wear and two for undiagnosed pain. Of seven patellar fractures, five required surgery. IBII: Nineteen re-operations of which six were complete revisions: two for sepsis, one for tibial loosening from catastrophic osteolysis, two for instability and one for stiffness. There were no revisions for patellar complications. Of 12 non-revision re-operations, two were for patellar fractures, three for dislocation of the posterior stabilized mechanism and one for failure of the modular locking mechanism. Six knees suffered patellar “clunks” treated arthroscopically.

Discussion: The femoral component patellar groove was smoothed and the posterior stabilized mechanism was relocated on the IB II. This increased motion and decreased patellar fractures but caused scar on the quadriceps tendon to “clunk” and lead to dislocations of the “spine and cam”. All failures occurred in the first five years.

Clinical Relevance: Specific patellar problems were improved with design modifications. New problems have been addressed and long-term survival has not been compromised by modularity

Both backside and articular surface wear have been linked to osteolysis after total knee arthroplasty (TKA). Prostheses with cementless fixation, screw holes in high load regions, and thin polyethylene are susceptible to backside wear. Factors associated with articular wear are similarly well defined. Micromotion at the modular polyethylene interface has been reported for many prostheses, but the relevance of such data compared to articular motions and wear are difficult to appreciate. This study compares in vivo motions and wear occurring at the backside and articular surfaces after TKA.

Contemporary PCL-retaining prostheses from one manufacturer were implanted by one surgeon using cement fixation. The polyethylene inserts were > 6mm thick with a full peripheral rim capture and anterior wire locking mechanism. Femoral condylar motions were measured in 20 knees using fluoroscopic analysis during stair and gait activities. All patients had good to excellent clinical outcomes at one year follow-up. Articular and backside surface damage was evaluated on 32 polyethylene inserts retrieved after 27 months (1 to 71) months in-situ for infection (9), autopsy (6), patellar resurfacing (4), patellar loosening (4), tibial loosening (3), osteolysis (2), and other (4).

Femoral condylar translation over the polyethylene articular surface ranged from 5-10 mm, which is substantially larger than the reported 50-500 micron range of backside interface micromotion measured in vitro. Damage covered < 33% of the backside surface and appeared as a cast impression of the opposed metal tibial component without scratches associated with micromotion. In contrast, damage consisting predominantly of scratching, burnishing and tractive striations covered 46% of the articular surface.

Different locking mechanisms for modular polyethylene inserts result in different degrees of backside wear. No significant backside wear was observed these retrieved inserts with a wire-supplemented peripheral capture. Given the abrasive wear mechanisms and particulate debris shed during femoral condylar sliding, efforts to control motions at the articular surface appear warranted.

Knee simulators are now widely used for the determination of performance and wear durability of TKR’s. The International Standards Organisation (ISO) force-control option synchronises AP force and IE torque with flexion angle and axial force for the walking gait cycle. The force control concept subjects the same input waveforms to different TKRs, allowing them to move (and wear) as their designs dictate. It however relies on a mechanical spring based assembly to simulate the restraint effects of ligaments in AP and rotation. The contribution of this restraint mechanism depends on the stiffnesses of the four springs, and on how they are set at the neutral position. The springs can be loose with a gap, such that compression only starts (or ends) when the motion exceeds the gap. Alternatively the springs can be pre-compressed such that they never go loose.

A detailed mathematical model was developed which included the stiffnesses of the four springs, their settings (level of pre-compression or gap), and geometry of the mechanism to calculate a matrix of AP restraint force curves with AP displacement, and how these curves change with int-ext rotation superimposed. The same was done for rotational restraint with simultaneous linear displacement. Through an interactive computational interface, the families of curves for any combination of variables were repeatedly plotted and compared to published data on the contribution of particular ligaments to the laxity of the knee (eg. Fukubayashi et al. 1982) to find the optimum spring stiffnesses and gap configuration. This was done for simulation arrangements retaining ACL, PCL or both retained or resected. The results showed the behaviour of the system to be as sensitive to the gap and level of pre-compression, as to the stiffnesses of the springs. For the resected ACL retained PCL situation, the optimum we recommend is soft (7.24 N/mm) springs on the ACL side, harder (33.8 N/mm) springs on the PCL side, with a 2.5 mm gap on each side. For both ACL and PCL resected, the soft (7.24 N/mm) springs for both sides are optimum, again with a 2.5 mm gap on each.

These settings are obviously different from each other, and are different from the tests with this simulator published by different laboratories. The same settings are a pre-cursor for valid comparison of wear and kinematics.

The perception that all cemented stems have reasonable assurance of success if implanted with contemporary cement technique has recently been questioned. Surface finish, stem shape, patient weight and high neck offset have been identified as factors contributing to early loosening. Small design changes to existing cemented stems have led to substantial differences in clinical performance. This study investigates the multi-factorial nature of stem loosening after a 24% early failure rate occurred within the initial three years.

Total hip arthroplasty was performed by the same surgeon on 67 patients with an average age and weight of 65 years (21-85) and 82 kg (49-127), respectively. Initial diagnosis was osteoarthritis (84%), osteonecrosis (7%), congenital dysplasia (4%), and other (5%). Modern femoral stems (Perfecta IMC) with increased lateral neck offset were implanted using contemporary cementing techniques. The stems are grit-blasted proximally, with intramedullary collar steps on the anterior/posterior surface. These design features are meant to enhance axial load transfer and stem-cement bonding. All acetabular cups were uncemented and used polyethylene (48 patients) or cobalt-chrome (20 patients) liners. Patients were evaluated with clinical and radiographic follow-up.

Revision for stem loosening was necessary in 16(24%) patients 9 to 38 months after index surgery, including 9 hips revised within the first 18 months. Radiolucencies at the cement/bone interface, stem subsidence and distal femoral osteolysis were consistently observed. Patients with loosening were significantly heavier than those with well-fixed stems (93 kg versus 78 kg, respectively). Revised hips included 7 cobalt-chrome and 9 polyethylene articulations.

It appears that several mechanical factors contributed to these early failures. Lateral offset stems with cement fixation appear to be at risk for loosening in young, heavy patients. Design features and a thin cement mantle may have resulted in increased cement stresses and cracks during the axial and torsional loading that occur with daily activities.