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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.
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.
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.
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.
Clinical results were determined according to the hip joint function criteria of the Japanese Orthopaedic Association (JOA).
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.
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.
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.
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.
This study has been cleared by the Ethical Committee, University of Zurich, Switzerland.
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.
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.
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.
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.
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.
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.
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.
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.
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%).
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.
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.
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)
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.
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 [
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
Malalignment and cement mantle quality have been implicated in loosening of the Charnley stem [
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.
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.
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.
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.
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
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.
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).
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 (
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 (
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.
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.
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.
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.
Further evaluation of the mid and long term results are necessary to evaluate the effectiveness of Computer Assisted Surgery in Total Knee replacement.
polyethylene wear and degradation demand of thin components
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.
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 [
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 low risk of tribologically induced failure no PE particle induced osteolysis
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.
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.
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.
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.
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.
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.
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
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 [
In a previous study we have developed a Model-based RSA algorithm, which does not require the attachment of markers to 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.
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.
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.
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 (
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.
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.
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). Per – operative group: custommade implants based on a mould of the femoral cavity in the proximal femur and manufactured during surgery. The prosthesis was size for size and the HA coating was applied on the proximal 1/3 of the implant. (13 cases with a minimum follow-up of two 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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[
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 [
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.
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.
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.
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 !) -Use of GoldFinger System (4 yrs on) -First implantations in Sept. 00 (only simple clinical impressions today)
Clinical, X-ray follow-up system: All NewWave users can consult the computer Letterbox :
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..
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.
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.
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.
Validation of input parameters and the resulting polyethylene damage is essential for knee joint wear simulators to be useful in prospective evaluations. The purpose of this study was to compare damage patterns on polyethylene inserts wear tested on a knee simulator with inserts retrieved after well-functioning total knee arthroplasty (TKA).
Five polyethylene tibial inserts from a PCL-retaining knee prosthesis (Natural Knee) were wear tested on an Instron/Stanmore simulator in 50% bovine serum. The input consisted of ISO 14243 force-controlled testing standard to simulate human gait for 5 million cycles. Nine polyethylene tibial inserts (Natural Knee) were retrieved from patients after 52+45 months (13-124) of successful function. The inserts were retrieved post-mortem (n=7) and for pain (n=2). Articular damage was assessed and the circumference of each damage region digitized. The damage size, location and linear surface deformation were measured and the deformation rate (mm/106 cycles or mm/year) was calculated.
The linear deformation rate for all inserts decreased considerably with time. Lateral damage was located significantly more posterior than the medial damage on both the simulated and retrieved inserts, corresponding to femoral external rotation. Retrieved inserts had larger lateral damage, whereas simulator inserts had larger medial damage. The AP extent of damage on the retrieved inserts was significantly greater than the extent on the simulator inserts. Three retrieved inserts had substantial delamination, whereas none of the simulator inserts had delamination.
There was good agreement in the deformation rates for the simulator and retrieved inserts. However, retrieved inserts with delamination show an increased deformation rate and this type of damage did not occur on simulator inserts. The greater AP extent of damage and larger lateral damage on the retrieved inserts suggest that in vitro wear simulation should perhaps include a more complete range of patient activity dynamics to better predict in vivo damage.