Introduction. Ultra-high molecular weight polyethylene (UHMWPE) is the sole polymeric material currently used for weight- bearing surfaces in total joint replacement. However, the wear of UHMWPE in the human body after total joint replacement causes serious clinical and biomechanical reactions. Therefore, the wear phenomenon of UHMWPE is now recognized as one of the major factors restricting the longevity of artificial joints. In order to minimize the wear of UHMWPE and to improve the longevity of artificial joints, it is necessary to clarify the factors influencing the wear mechanism of UHMWPE. Materials and Methods. In a previous study (Cho et al., 2016), it was found that roundness (out-of-roundness) of the retrieved UHMWPE acetabular cup liner [Figure 1(a)] had a tendency to increase with increasing roundness of the retrieved metal femoral head [Figure 1(b)]. It appears that roundness of the femoral head contributes to increase of wear of the polyethylene liners. We focused on the roundness of femoral head as a factor influencing the wear of polyethylene liner in hip prosthesis. In this study, further roundness measurements for 5 retrieved metal femoral heads were performed by using a coordinate measuring machine. The elasto-plastic contact analyses between femoral head and polyethylene liner using the finite element method (FEM) were also performed in order to investigate the influence of femoral head roundness on the mechanical state and wear of polyethylene liner in hip prosthesis. Results. The range of roundness of the 5 retrieved metal femoral heads measured in this study was 14.50∼44.70 µm. Two examples of the results of FEM contact analyses are shown in Figure 2. Figure 2(a) is the results of the repeated contact analysis between femoral head and polyethylene liner under constant axial loading of 1000 N. Figure 2(b) is the results of the repeated contact analysis between femoral head and polyethylene liner under hip joint loading during normal gait. These figures show the distribution of the contact stress (von Mises equivalent stress) in the polyethylene liner. The graph in Figure 3 shows the changes in the maximum contact stress in the polyethylene liner with the flexion/extension angle of femoral head. Discussion and Conclusions. As the results of a series of the FEM contact analyses, it was found that repeated high contact stresses which exceed the yield stress of UHMWPE caused by roundness of the metal femoral head occurred in the polyethylene liner as shown in Figures 2 and 3. It was also found that the magnitude and amplitude of the repeated contact stresses had a tendency to increase with increasing roundness of the femoral head and axial loading applied to the femoral head. The results of this analytical study suggest that the roundness (out-of- roundness) of the femoral head is associated with accelerating and/or increasing wear of the UHMWPE acetabular cup liner in a hip prosthesis after total hip replacement. For any figures or tables, please contact authors directly

Introduction. Ultra-high molecular weight polyethylene (UHMWPE) is the sole polymeric material currently used for weight- bearing surfaces in total joint replacement. However, the wear of UHMWPE and the polyethylene wear debris generated in the human body after total joint replacement cause serious clinical and biomechanical reactions. Therefore, the wear phenomenon of UHMWPE in total joint replacement is now recognized as one of the major factors restricting the longevity of these implants. In order to minimize the wear of UHMWPE and to improve the longevity of artificial joints, it is necessary to clarify the factors influencing the wear mechanism of UHMWPE. Materials and Methods. The wear and/or failure characteristics of 33 retrieved UHMWPE acetabular cup liners of hip prostheses were examined in this study. The retrieved liners had an average in vivo duration of 193.8 months (75 to 290 months). Several examples of the retrieved liners are shown in Figure 1. The elasto-plastic contact analyses between metal femoral neck and polyethylene liner and between metal femoral head and polyethylene liner using the finite element method (FEM) were also performed in order to investigate the factors influencing the wear and/or failure mechanism of the polyethylene liner in hip prosthesis. Results. In the examination of the retrieved polyethylene liners, the generation of component impingement was observed in 24 cases of the 33 retrieved liners (72.7%) as shown in Figures 1(a) and (b). In addition, the generation of cold flow into the screw holes in the metal acetabular cup was observed in 27 cases of the 33 retrieved liners (81.8%) as shown in Figures 1(c) and (d). Several examples of the results of the FEM contact analyses are shown in Figure 2. In the simulation of the component impingement, it was found that high contact stresses which exceed the yield stress of UHMWPE and considerable plastic strains occurred in the rim of the polyethylene liner as shown in Figures 2(a) and (b). In the simulation of the cold flow, it was found that the stress concentration near the edge of screw hole has significant influence on the states of contact stresses and plastic strains in the surface and undersurface (backside) of the polyethylene liner as shown in Figures 2(c) and (d). Discussion and Conclusions. In this study, we focused on the impingement between the metal femoral neck and the polyethylene liner and the cold flow into the screw holes on the backside of the polyethylene liner as the factors influencing the wear and/or failure of the UHMWPE acetabular cup liner in hip prosthesis. The results of these retrieval and analytical studies confirmed that the component impingement and the cold flow into the screw holes contribute to increase of wear and/or failure of the polyethylene liner. Therefore, it is necessary to improve resistance to the component impingement and the cold flow in order to decrease the wear and/or failure of the UHMWPE acetabular cup liner and to increase the longevity of hip prosthesis. For any figures or tables, please contact authors directly

Introduction. Ultra-high molecular weight polyethylene (UHMWPE) is the sole polymeric material currently used for weight- bearing surfaces in total joint replacement. However, the wear of UHMWPE in knee and hip prostheses after total joint replacement is one of the major restriction factors on the longevity of these implants. In order to minimize the wear of UHMWPE and to improve the longevity of artificial joints, it is necessary to clarify the factors influencing the wear of UHMWPE. A number of studies have investigated the factors influencing the wear of UHMWPE acetabular cup liner in hip prosthesis. Most of these studies, however, have focused on the main articulating surfaces between the femoral head and the polyethylene liner. Materials and Methods. In a previous study (Cho et al., 2016), the generations of cold flow into the screw holes in the metal acetabular cup were observed on the backside of the retrieved UHMWPE acetabular cup liners as shown in Figure 1. We focused on the screw holes in the metal acetabular cup (Figure 2) as a factor influencing the wear behavior of polyethylene liner in hip prosthesis. In this study, computer simulations of the generation of cold flow into the screw holes were performed using the finite element method (FEM) in order to investigate the influence of the screw holes in the metal acetabular cup on the mechanical state and wear behavior of polyethylene liner in hip prosthesis. Results. An example of the results of the FEM simulations performed in this study is shown in Figure 3. In the region which the cold flow into the screw holes occurred, it was found that locally high contact stresses which exceed the yield stress of UHMWPE and considerable plastic strains were generated throughout the overall thickness between the backside and top surface of the polyethylene liners. On the contrary, in the case of the polyethylene liner combined with the metal acetabular cup without screw hole, although the regions of high contact stress and high plastic strain had a tendency to be limited around contact surface compared with those of the combination with screw holes, the values of contact stress and plastic strain were lower than the combination with screw holes. Discussion and Conclusions. The results of this study suggest that the cold flow generated by the existence of the screw holes in the metal acetabular cup of hip prosthesis reduces the wear resistance of the UHMWPE acetabular cup liner. It would appear that the cold flow into the screw holes contributes to structural weakening of the UHMWPE and reduction of the polyethylene thickness, thus increase of internal stresses and plastic strains in and around the regions of cold flow. Therefore, it is required that improvement of the screw holes in the metal acetabular cup and/or improvement of fixation method of the metal acetabular cup to a pelvis in order to enhance the wear resistance of the polyethylene liner. For any figures or tables, please contact authors directly

The accurate differentiation of aseptic loosening from periprosthetic infection in the painful hip prosthesis is a major clinical challenge. FDG-PET imaging has shown great promise in various clinical settings for detection of infection. This prospective study was designed to determine the efficacy of FDG-PET imaging in the assessment of patients with painful hip prosthesis. One hundred and thirteen patients with 127 painful hip prostheses were evaluated by FDG-PET. Approximately 60 minutes after the intravenous administration of FDG images of the lower extremities were acquired using a dedicated PET machine. FDG-PET images were interpreted by experienced nuclear medicine physicians. Images were considered positive for infection if PET demonstrated increased FDG activity at the bone-prosthesis interface of the femoral component of the prosthesis. Surgical findings, histopathology, and clinical follow-up served as the “gold standard”. FDG-PET was positive for infection in 35 hips and negative in 92 hips. Among 35 positive PET studies, 28 were proven to be infected by surgical and histopathology findings as well as follow-up tests. Of 92 hip prostheses with negative FDG-PET findings, 87 were proven to be aseptic. The sensitivity, specificity, positive and negative predictive values for FDG-PET were 0.85 (28/33), 0.93 (87/94), 0.80 (28/35), and 0.95 (87/92), respectively. The overall accuracy of FDG-PET in this clinical setting was 90.5% (115/127). The results demonstrate that FDG-PET is a highly accurate diagnostic test for differentiating infected from non-infected painful hip prosthesis. Therefore, FDG-PET imaging is considered the study of choice in the evaluation of patients with suspected hip prosthesis infection

Background: Revision total hip replacement is challenging when there is severe proximal bone loss. The Kent hip femoral prosthesis – a distally locked femoral stem – was designed to overcome this difficulty, however no study to date has assessed its durability. Methods: We independently reviewed the results of 105 Kent Hip Prostheses used at one hospital between 1987 and 2000. The indication for revision was aseptic loosening in 64, periprosthetic fracture in 19, septic loosening in 4, and severe bony deformity in 14. In the remaining 4 cases, a Kent hip prosthesis was inserted in the presence of metastatic tumour in the proximal femur to enable mobilisation. A functional evaluation of these patients using the Oxford Hip Score and a survival analysis of the stems was performed. Results: The mean duration of follow-up was 5.3 years (range 20 months to 15 years). The mean time to full weight bearing following surgery was 4 days and mean hospital stay was 13 days. Almost all patients experienced substantial improvement in hip related pain and disability (as measured by the Oxford Hip Score). 12 stems required further revision. Taking removal of the stem for any cause as the end point, cumulative survival at 15 years was 88%. Conclusions: Cumulative survival rates for the Kent hip femoral prosthesis compare favourably with other revision stems used where there is severe proximal bone loss. It enables early full weight bearing and hospital discharge, resulting in a low post-operative medical complication rate. However the need for continuing follow-up remains, since the rate of complications such as locking screw fracture, aseptic loosening, and periprosthetic fracture, may increase in the future

The Huckstep ( Bbraun Medical) interlocking hip prosthesis has been used in the Sheffield Lower Limb Arthroplasty Unit in cases of complex primary and revision hip arthroplasty since 1996. We reviewed the outcomes in cases performed prior to October 2001. Eighty cases were identified. Of these, eight died within one year of surgery, four of which were in the peri operative period. A further thirteen were lost to follow up in the first year due to medical deterioration, move from area or refusal to attend. The remaining 57 patients had a mean time to follow up of 34 months (12–81m). As a primary prosthesis the Huckstep was used to allow corrective osteotomy. In revision cases it was employed to bypass periprosthetic fractures and fragile proximal femoral bone, in cases requiring extended trochanteric osteotomy to facilitate cement removal, and to enable use of bulk proximal femoral allograft. The use of the Huckstep was planned pre operatively in 67 cases and as a salvage option in 13.The design of the implant allowed a stable construct without the need for bone cement which could interpose and prevent bone healing or graft incorporation. It avoids problems incurred in pressurising cement or impaction grafting against fragile bone. Complications included infection requiring further surgery (5), dislocation (5), periprosthetic fracture (2), screw breakage (4), and mechanical failure (2). Eleven patients required further revision surgery. The apparently high complication rate reflects the complex nature of the surgery and the high degree of co morbidity in the elderly patient group. In conclusion, we have found the Huckstep hip prosthesis to be a useful option in cases of complex hip surgery. Whilst the long term outcome is as yet unknown, our short term results show it to have allowed healing of fractures, osteotomy sites and cortical defects, allograft incorporation and replenishing of bone stock, hence facilitating further arthroplasty surgery

Introduction. After total hip arthroplasty, dislocation is one of the most frequent serious early complications. This occurs in part due to impingement (catching and leverage of the neck-cup on the inlay/cup border). Impingement may also negatively impact long-term outcomes. Materials and Methods. A preliminary model for an optimised hip endoprosthesis system was developed to offer a mechanical solution to avoid impingement and dislocation. A computer-supported range of motion simulation using parameters of cup anteversion and inclination as well as torsion and CCD shaft angle was then performed to localise areas of anterior and posterior impingement of typical acetabular cups. Results. Through isolation of the two main trajectories of motion, and modifications with corresponding gaps to the inlay/cup areas as well as oppositional banking in the abduction/adduction plane, the combination of a snap-fit acetabular cup with reduced cup profile was the result: the “bidirectional total hip prosthesis.”. Under standardised parameters, the ranges of impingement for typical implants are not directly opposite one another (at 180°), but are found instead at an angle of 108.3°. Conclusion. Complications such as dislocation and impingement may possibly be avoided with the bidirectional total hip prosthesis. Typical implantation parameters yield an implant design with rotational asymmetry. [Fig. 1, 2]

Fracture of the femur in association with total hip arthroplasty is a challenging complication that has been well described. A variety of surgical treatment options have been reported. We present our experience of the Kent hip prosthesis in the management of periprosthetic femoral fractures. We reviewed all patients (46) who had a Kent hip inserted for a periprosthetic femoral fracture. This group consisted of 16 males and 30 females of average age 73 years (43–96 years) at the time of fracture. Follow up ranged from 2 to 85 months (average, 4 years). In 26 cases the primary prosthesis was a Charnley stem. Of the remaining cases the primary prostheses were as follows: 6 Austin Moore prostheses, 5 Howse, 4 Custom, 1 Exeter, 1 DHS, 1 Richards and 1 Thompson stem. There were 6 intraoperative fractures. Of the postoperative fractures forty-four were associated with a traumatic event. Time to fracture varied from 3 weeks to 20 years (average, 8 years). Prior to fracture 42 patients were living in their own home and 24 patients were mobile unaided. Twenty patients had pain prior to their fracture. The majority of patients were deemed ASA grade II or III. Thirty fractures were Johanssen type II, 14 type I, and 2 type III. At the time of surgery, 32 patients had a loose stem and/or cup. Operating time was on average 143 minutes (range, 65–235 minutes) and intraoperative transfusion requirements ranged from 0–7 units of packed red cells (average, 3 units). Duration of hospital stay was on average 23 days (range, 7–77 days). Two patients developed superficial wound infections, six patients dislocated their prosthesis and one patient developed a chronic wound sinus. In 34 cases fracture union was complete at latest review. Three patients required revision surgery for stem breakage and in 10 cases there was evidence of screw breakage. At latest review, of the 31 patients that could be contacted 18 are still resident in their own homes. Twenty-six patients require the use of a walking aid (most commonly one stick). Ten patients have ongoing pain in relation to their operated hip. In conclusion, we feel that the Kent hip prosthesis is a useful surgical option in the one-stage management of periprosthetic femoral fractures

We report the result of 46 patients (30 female, 16 male) with periprosthetic femoral fractures who underwent insertion of the Kent Hip Prosthesis. Average age was 73 years (range 43–96years) and follow-up ranged from one to seven years (average, 4 years). The primary implants involved were as follows: Charnley (26), Austin Moore (6), Howse (5), Custom (4), Exeter (1), DHS (1), Thompson (1) and Richards (1). Average time to fracture from insertion of the primary implant ranged from 3 weeks to 20 years (average, 8 years). Forty cases were post-primary implant fractures (38 traumatic, 2 atraumatic) and 6 occurred intraoperatively. Using the Johanssen classification there were 12 type I, 30 type II and two type III fractures. Of the 46 cases, prior to fracture, 42 were living in their own home, 24 were mobile unaided and 20 had thigh and/or groin pain. Thirty-two had a loose stem and/or cup assessed at the time of surgery. Operating time was on average 143 mins (65–235mins). At latest follow-up, 43 were living in their own home, 5 were walking unaided and 10 had ongoing pain. In 34 cases complete union was achieved. There were no cases on non-union. Three patients required revision surgery for broken stems. Three patients sustained wound infections and there were six posterior dislocations. All of the complications were treated satisfactorily. We conclude that the Kent Hip Prosthesis is a useful option in the management of periprosthetic femoral fractures

Introduction. This study reports outcomes of 35 revisions of a recalled metal-on-metal (MOM) monoblock prosthesis performed by a single surgeon. Methods. We prospectively collected data on all patients who underwent revision of a recalled metal-on-metal monoblock prosthesis between 2010 and 2015. Average follow-up was 2.5 years post-revision and 6.9 years post-primary procedure. We evaluated the cohort for age, BMI, gender, existence of medical comorbidities, and post-op complications. We compared pre and post-revision cup abduction angles, anteversion angles, combined angles, cup sizes, and Harris Hip Scores. Cobalt and chromium levels were followed throughout the study period for each patient. Results. Thirty-one patients underwent 35 revisions surgeries for pain, high metal ions, infection, aseptic loosening, failure of ingrowth, leg length discrepancy and/or pseudotumor. Two of these revisions were subsequently re-revised – one for continued pain and one for failure involving multiple dislocations, breakage of screws, and acetabular fracture. The survival rate for our revisions to date is 94.3%. Female patients comprised a majority of revisions (54%) despite comprising a minority (28%) of primary hip replacements using the studied prosthesis. Revised patients were an average of 51.8 years of age with a BMI of 31.07. Demographics are included on Table 1. There were five post-operative complications, including 2 infections, 2 dislocations, and one DVT. Cups were revised from a mean abduction angle of 47.5° in primary hips to 42.3° in revisions. Cups were revised from a mean of 53.4 to 57.8. Cobalt and chromium levels were followed in all patients and showed significant decrease after revision (Graph 1). Cobalt levels decreased from an average of 33.7 to 13.1 ng/mL while Chromium levels decreased from an average of 12.4 to 9.2 ng/mL. Harris Hip Scores increased significantly after revision (45.8 to 72.1). Conclusion. This study presents 35 revisions of a recalled monoblock hip prosthesis performed by a single surgeon at our institution from 2010 to 2015. To our knowledge, this is the largest single-surgeon study reported in the literature. Acetabular cups were revised to a lower average abduction angle. Patients have had significant improvements in Harris Hip Scores and significant decreases in Cobalt and Chromium levels after revisions. Our revision survival rate to date is 94.3% at an average of 2.5 years (range 2 weeks – 4.3 years). To view tables/figures, please contact authors directly

Previous scientific studies have highlighted how coupling is an important element affecting total hip arthroplasty's survival.

This study aims to evaluate whether metal-on-metal (MOM) coupling could be a statistically significant risk factor.

The data from the regional joint registry (Registro dell'Impiantologia Protesica Ortopedica, RIPO) was used for analysis. The data collection accuracy of this registry was 97.2% in 2017.

We retrospective evaluate all MOM total hip arthroplasties (THAs) implanted in our department between January 01st 2000 and December 31st 2011. We used a control group composed by all other prosthesis implanted in our Department in the same time lapse.

We registered 660 MOM THAs. Mean age of patients was 66.9 years. 603 patients have a >36mm head, while 78 a <36 mm one. Neck modularity was present in half of patients. 676 implants were cementless. We registered 69 revisions, especially due to aseptic mobilization (16 THAs), implant breakage (9 THAs) and periprosthetic fracture (6 THAs).

The MOM THAs overall Kaplan-Meier survival rate was 87.2 at 15 years, and the difference between MOM THAs and other implants two curves is statistically significant (p<0.05). Male sex is a significant risk factors. Further evaluations are in progress to establish the presence of any additional risk factors. We think weight and/or BMI may be included in this category.

Our study confirms the data currently present in the literature regarding a lower survival of metal-on-metal hip prostheses.

The male sex is a statistically significant risk factor (p<0.05), while age, head size and modularity of the prosthetic neck are not statistically significant (p>0.05).

Any new finds will be presented at the congress venue.

Elderly patients with a high mortality risk for revision surgery are severely handicapped by a loosened hip prosthesis. Loosening is mainly caused by particle-induced osteolysis leading to the formation of a synovium-like interface tissue. As an alternative to revision surgery we have investigated the possibility of removing the tissue using a gene therapy approach and thereafter stabilizing the prosthesis with percutaneous cement injection. First we demonstrated that transduction of interface cells with a gene coding for E.coli nitroreductase (NTR) resulted in a 60-fold increase in sensitivity to the prodrug CB1954 that is converted to a toxic metabolite by NTR. Given these in-vitro data, we explored if intra-articular administration of this adenoviral vector encoding NTR followed by the prodrug was able to kill sufficient tissue in-vivo to allow refixation of the prosthesis by cement. We report the first three patients from a phase 1 study of 12 patients with a loosened hip who are experiencing debilitating pain and have significant comorbidity. On day 1 the vector is injected into the hip joint and on day 3 the prodrug is injected. On day 10 three holes are drilled in the femur and one in the acetabulum. Biopsies are taken from the periprosthetic space and low viscosity cement (Osteopal, Biomet Merck, Sjöbo, Sweden) is injected under fluoroscopic guidance. The first three patients have been included in the study and five more are planned for treatment before June 2005. The patients are females of 86, 72, and 79 years old. There were no adverse effects from vector injection (3x10 exp 9 particles). Six hours after prodrug injection the patients experienced nausea, (WHO grade 1) a commonly reported reaction to this prodrug. There was vomiting in two patients. Hip pain increased, but this was anticipated as this therapy will increase prosthesis loosening. 16 ml of cement was subsequently injected into the periprosthetic space in the first patient and 18 ml in the second. The patients were ambulated the day after surgery. The first two patients have a follow-up of twelve and six weeks. There was no pain in the hip. The maximum walking distance had increased from 5 to 30 meters in the first patient. The current study is the first to use in vivo intra-articular adenoviral mediated gene transfer in a clinical setting. Our preliminary results suggest that gene therapy and cement injection for hip prosthesis refixation is clinically feasible

Nine cases of acetabular erosion following insertion of the Monk "hard top" hip prosthesis for subcapital fractures are presented. All of these patients had significant symptoms and represented 5% of the total group. In our experience acetabular erosion has proved to be a significant complication of the Monk "hard top" prosthesis

We report the clinical and operative details of seven cases of fracture of the femoral stem of the Ring TiMESH cementless hip prosthesis (two were cemented and five uncemented). Six fractures occurred in the proximal one-third of the stem and one at mid-stem. The failures are attributed mainly to two defects in stem design, the narrowness of the anteroposterior dimensions and the depth of the recess for the titanium mesh pads. Great difficulty was experienced in removing the osseo-integrated distal fragments of the broken stems

Aims: The authors report oncological and functional results after 15 acetabular reconstructions, followed tumor resection, with an original technique using homo-lateral proximal femoral autograft and total hip prosthesis. Material and method: The modiþed Musculoskeletal Tumor Society Score (MSTS) and the Toronto Extremity Salvage Score (TESS) were used for functional analysis. Functional results were available for only 10 patients who presented with a minimal of 2 years follow-up. Results: Fifteen consecutive patients, 9 men and 6 women with a median age of 50 years, were managed in our department for acetabular bone malignant tumor. The tumors involved the zones II in 5 patients, the zones II and III in 5 patients. The tumors included 10 chon-drosarcomas, 1 malignant þbrous histiocytoma, 1 radio-induced sarcoma, 1 myeloma and 2 metastasis. The mean follow-up was 31 months (Range, 12 to 50 months). Local recurrence occurred in 1 case and metastases in 3 cases. Three patients died of tumoral disease and one of intercurrent disease. Eight complications were observed: aseptic failure (n=1), obturator nerve damage (n=1), deep infection (n=4), skin necrosis (n=2), pros-thesis dislocations (n=1) and deep venous thrombosis (n=1). Five revision were performed. The mean MTS was 72% (range, 40 to 96%) and the mean TESS was 82.5% (range, 56 to 86%). Fusion occurred in all reconstructions and all patients recovered an active hip abduction and ßexion. Discussion: This original technique, using an autograft and a standard total hip prosthesis, is available for zone II and III acetabular reconstructions

A 70-year-old man with an uncemented metal-on-polyethylene total hip prosthesis underwent revision arthroplasty 33 months later because of pain, swelling and recurrent dislocation. There appeared to be corrosion and metal release from the prosthetic head, resulting in pseudotumour formation and severe local soft-tissue destruction. The corrosion occurred at the junction between the titanium-molybdenum-zirconium-iron taper and the cobalt-chrome-molybdenum head, but the mechanism was unproven

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

Because we encountered a high failure rate of the acetabular component of the uncemented, hydroxy-apatite coated, Omnifit total hip prosthesis (Osteonics corporation, Allendale, NJ, USA), we conducted a retrospective study of 418 consecutive total hip arthroplasties with a mean follow up of 60 months. The results of 418 hydroxy-apatite coated, uncemented Omnifit total hip arthroplasties, conducted between 1989 and 1996 were evaluated. Two different acetabulum cups were used: 145 screwcups with one central screwhole, and 273 press fit (PF) cups with several screwholes. The internal geometry of these cups and the fixation of the polyethylene insert in the metal cups were identical. In 339 arthroplasties a 32-mm femur-head was used, in 79 a 28-mm head. Patients’ records and x-rays were evaluated for clinical findings, polyethylene (PE) wear, acetabular and femoral osteolysis and findings during revision surgery. Revision surgery was performed in 73 patients, mainly because of symptomatic acetabular osteolysis (79%). Mean PE wear was 0.16 mm/year (0.19 mm in PF cups, 0.11 mm in screwcups). Acetabular osteolysis was found to be present in178 hips (70 screwcups and 108 PF cups). In both cupdesigns the osteolysis was mainly found around the screwholes of the metal cups. During revision surgery these osteolytic defects were a lot larger than suggested by x-ray imaging. In 22.6% of the hips osteolysis was also present in the proximal femur. Kaplan-Meier survival analysis showed, after 6 year follow up, a better survival for of the screwcup (96%, confidence interval 93–99%) than the PF cup (66%, 95%CI 56–77%). We hypothesized that this specific combination of metal cup and polyethylene insert -possibly due to an insufficient fitting- is responsible for the migration of polythylene wear particles through the screwholes in the metal cup, causing acetabular osteolysis and neces-satating revision surgery. For this reason we abandonned the use of this type of uncemented acetabular component

Introduction: One of the primary complications in total hip and knee arthroplasty is infection. One of the major risk factors for deep periprosthetic infection is wound infection. This alone is associated with a substantial morbidity-increase which, in turn, increases hospital admittance time and therefore adds significant costs to the healthcare system. The aim of this study is to determine whether contamination of instruments used during primary insertion of a prosthesis, can be considered an early indicator for the occurrence of prolonged wound discharge. Early antibiotic treatment could then prevent this and decrease hospital admittance time and costs to the health care system. Material and Methods: During 121 procedures, swabs were taken from the first unused broach at the beginning and at the end of the procedure. Removed material from the bone (acetabulum and femur in the hip joint; femur and tibia in case of the knee joint) was tested for contamination as well. During 50 procedures a control swab was taken. The patients on the ward were also monitored to find out whether prolonged wound discharge occurred and to see after how many days the patients were discharged. Results: In 46 cases (38%) at least one culture showed microbial growth. In the other 75, there was no growth at all. If one of the cultures is positive, there is a 52% risk of prolonged wound discharge. Ifall cultures are negative, this risk is reduced to 13% (Chi-square: PO.001). Patients with a positive peroperative culture have to remain in the hospital for an additional 2.4 days (T-test: P-0.001). Conclusion: Peroperative culturing during primary insertion of a knee or hip prosthesis, provides a reliable tool to predict postoperative duration of wound discharge and hospital-admittance time

Introduction. Total hip arthroplasty in young patients is still associated with high failure rates, especially at the acetabular side. Purpose of this study was to evaluate the long-term results of the Alloclassic cementless Zweymüller total hip prosthesis in patients younger than 50 years at the time of surgery. Methods. Between 1987 and 1994, 73 Zweymüller total hip arthroplasties with a titanium threaded cup were placed in 67 patients younger than 50 years. Mean age at surgery was 43 years (23–49 years). Patients were followed clinically with use of the HHS, revisions were determined and radiographs were analyzed. Kaplan-meier analysis was used to determine survival for different endpoints. Results. Three hips were revised for septic loosening, 3 cups for aseptic loosening and 1 hip because of periprosthetic fracture. Four patients (4 hips) died and 8 patients (9 hips) were lost to follow-up without any revision. 48 patients with 53 prostheses could be evaluated after a mean follow-up of 208 (170–253) months and the mean HHS was 90 (52–100). Cumulative survival analysis with endpoint revision for any reason was 89% (C.I. 85–93) at 17 years. With endpoint aseptic loosening, survival was 95% (C.I. 91–98) at 17 years. Conclusion. Alloclassic Zweymüller total hip arthroplasty with a titanium threaded cup showed good long-term results, even in this group of patients younger than 50 years

The ABG total hip prosthesis had been studied to prevent any kind of stress shielding and to allow the localization of the loads in the metaphiseal region of the femur. The aim of this study was to analize the effective behaviour of the loads in long-term implants and the possible correlations of those findings with the clinical situation of the patients. We considered 87 total hip arthroplasty implants executed from 1989 to 1995 and performed by using Anatomique Benoist Girard I uncemented prosthesis. The radiographical findings have been classified observing Engh’s stability criteria according to Gruen’s subdivision of the periprosthetic femoral zones. The radiographical analysis shows a higher presence of can cellous densification in Gruen’s zones 3 and 5 than the one found in zones 2 and 6. Furthermore the presence of a cortical reaction is more relevant in the distal zones.> Radiolucent lines are present in 16% of the cases in zone 4; their percentage in zones 3 and 5 decreases to 7.14% and 10.71%. Our study shows the certain presence of the stress shielding mechanism in long-term analysis and documents that the main region of late anchorage is the distal, not hydroxyapatite-coated, one.> The comparison with other similar studies shows the decrease of the presence of radiolucent lines in proximal femoral zones with the rise of the follow-up: it can be interpreted as the lesser presence of micro movements of the tip of the prosthesis due to the distalization of the anchorage

Purpose: The surgical approach is an essential element for precise reduction and rigid fixation of fractures of the acetabulum. In cases where the anterior column is mainly involved and total hip arthroplasty (THA) is indicated, classical approaches do not allow double assess to the anterior column necessary for reduction and fixation and to the femoral canal for insertion of the prosthesis. Combining Heuter’s anterior approach and Letournel’s ilio-femoral approach provides access to the anterior column and to the often associated posterior hemi-transverse fracture, while allowing insertion of the total hip prosthesis. Material and method: This combined approach was used for ten among 60 THA performed for fracture of the acetabulum. Seven were primary procedures and three were differed reconstruction procedures. Mean patient age was 60.6 years (range 50 – 85 years). Fracture types were: acetabular wall and anterior column (n=8), anterior column and posterior hemi-transverse (n=2). All fresh fractures exhibited major acetabular damage associated with fracture of the femoral neck. A hybrid THA was used for all cases after fixation of the fracture. The femoral heads were used as graft material for deficient anterior columns in two patients and as “piecemeal” grafts for the others. Results: Mean follow-up was 36 months (range 24–35 months). At last follow-up all fractures had healed and all acetabular components exhibited solid fixation with no sign of migration. The mean outer diameter of the ace-tabular components inserted was 56 mm (52–64) using a 2 mm press-fit and one screw. The only complication was one postoperative anterior dislocation. Pain relief and function were satisfactory in all patients at last follow-up with a Postel Merle d’Aubigné score of 16 (13–18). Discussion: This anterior surgical approach enables good access to the acetabular walls and anterior columns, allowing solid fixation and relatively easy THA. The Kocher-Langenbech approach is still better in case of posterior deficiency or when posterior fixation requires space for inserting an acetabular component. We reserve it for THA used to treat fresh fractures of the acetabulum with major damage to the acetabulum and/or the femoral head, with or without neck fracture in patients aged 55 years or more. For differed reconstruction, we also use this approach if the acetabular damage involves the anterior column

Introduction: Proximal bone resorption is a common problem after total hip arthroplasty. This has been attributed to stress shielding and has been reported to be more pronounced for cemented than for uncemented implants. Aim: To investigate the cortical strain distribution of a new proximal “fit and fill” cementless, titanium, femoral, hip prosthesis based on the SROM design. Methods: Strain gauges were mounted on five fresh-frozen cadaveric and five saw-bone femora and checked against a template for the prosthesis. The strain gauges were placed at four levels on the anterior, posterior, medial and lateral cortices corresponding to the Gruen zones. Two extra strain gauges were placed on the proximal posteromedial cortex. Loading was applied to the intact and reconstructed femora in the ISO 7206–4 orientation and single legged stance in an MTS servo-hydraulic testing machine. Data were analysed using analysis of variance. Results: The strain distributions following reconstruction and multi-axis loading (ISO 7206–4 orientation) approximated the strains in an intact femur in the diaphysis. The proximal posteromedial cortical strains were approximately 50% of those of the intact femur. Conclusions: The strains observed in the proximal femur following reconstruction in the present study are considerably higher than most others reported in the literature. A number of factors may contribute to the high proximal strains observed. This study has illustrated that geometric design and material selection along with surgical technique may allow for greater loading to proximal bone and enhance the long term integrity of this type of implant

Introduction: In case of massive bone defect, femoral stem revision may cause significant problems to the orthopaedic surgeons. The periprosthetic infection introduces a further element of complication which often leads to complex surgical strategies. The aim of this study was to assess the preliminary results of femoral revision with modular resection femoral stems in a selected group of patients with infected total hip arthroplasty and extensive bone defect. Materials and Methods: The study group included five patients (three women – two men) with an average age of 72 years (range 62–81 years). From 2006 to 2008 the patients underwent a prosthetic femoral revision with resection modular stems to treat a septic loosened primary hip prosthesis (one case) or revision hip prosthesis (four cases). The bacteria responsible for the infection were MRSE in three cases, MSSE and Str. Agalactie in one case, Proteus Mirabilis in one case. Three patients were treated in election for septic loosening of hip implant and two were admitted in our Department as emergency for a periproshtetic femoral fracture (Duncan type B3). In all the patients the femoral bone defect was grade III-B according to Paprosky classification of femoral bone deficiency. One patient with periproshtetic femoral fracture underwent a one-stage prosthetic revision and four patients sustained a two-stage prosthetic revision. In one patient a local flap was performed and Vaacum Assisted Therapy was applied in order to treat an associated loss of substance. The patients underwent periodical clinical controls in which the result has been evaluated by means of Merle-d’Aubigné hip score. Results: The follow-up period ranged from 10 to 28 months. We observed one case of recurrence of infection in the patient treated with a one-stage revision. At present, we did not observe signs of infection in the remaining four patients who underwent a two-stage revision. As for functional result, four patients walked with supports and one without them. No patient referred moderate or severe residual pain. Discussion: The preservation of bone stock is one of the most important goals in prosthetic revision procedures. In some circumstances the amount of femoral bone loss can be so wide to prevent the application of conventional or modular uncemented femoral stems. In these selected cases cemented modular resection femoral stems may represent the only available option for femoral reconstruction. In our clinical experience this solution offered altogether successful outcomes. In our opinion two-stage revision is the preferable surgical choice

INTRODUCTION

Ceramic-on-ceramic hip resurfacing offers a bone conserving treatment for more active patients without the potential metal ion risks associated with resurfacing devices. The Biolox Delta ceramic material has over 15 years of clinical history with low wear and good biocompatibility but has been limited previously in total hip replacement to 48mm diameter bearings [1]. Further increasing the diameter for resurfacing bearings and removing the metal shell to allow for direct fixation of the ceramic cup may increase the wear of this material and increase the risk of fracture.

Purpose: Fracture of the neck of the femur in elderly subjects is generally treated by arthroplasty, either using a total or intermediary hip prosthesis, but with a high risk of dislocation, estimated at about 10% in the literature. We investigated the contribution of a double mobile cup to lower this risk. Material and methods: This prospective study was conducted by several operators in the same university unit between 1998 and 2001. A total of 177 mobile prostheses were implanted in patients with fracture of the anatomic neck of the femur (n=145), the neck and trochanter (n=22), or pathologic fracture (n=4). For six patients, the prosthesis was implanted after failed osteosynthesis of a trochanteric fracture. The postero-lateral approach was used for 136 women and 41 men (age range 61 – 92 years) living at home (n=124), or in an institution with a high degree of independence (n=53). The femoral stem was cemented (n=115) or impacted (n=62). A double mobile cup was used in all cases. A chromium-cobalt/ polyethylene couple was used and head diameters were 28 mm (n=150) or 22.2 mm (n=27). We studied outcome and risk of dislocation one year after implantation. Results: There were six deaths during the postoperative period. Among the 171 patients, 134 were seen at two months, 108 at six months and 89 at one year: 39 were questioned to ascertain outcome. During the first postoperative year, there were 37 deaths; these patients were followed. Six patients were lost to follow-up. We had two cases of intraprosthetic dislocation related to a defect in the chromium-cobalt head retention of the polyethylene insert. These two cases required revision and were reported to material surveillance with corrective measures for the manufacturer. There were three true dislocations (2%): 1) a posterior dislocation on day 24 in a female patient presenting a fracture with impaction of the femoral stem; 2) a posterior dislocation on day 22 in a female patient in very poor general condition (severe cardiorespiratory failure, death at 48 hr); 3) one recurrent posterior dislocation related to major acetabular retroversion, revised at four months. Discussion and conclusion: The double-mobile cup appears to be a simple reproducible method for preventing dislocation of prostheses implanted for fracture of the neck of the femur

Purpose: Wear of prosthetic implants, especially the metal-polyethylene head-cup couple, and dissemination of wear particles throughout the organisms the dominant long-term complication of total hip arthroplasty. We determined serum concentrations of chromium, cobalt, nickel, and molybdenum in patients bearing a total hip prosthesis with a chromium-cobalt metal-poly-ethylene head-cup couple. The purpose of our work was first to compare the levels observed with those found in a control population and then to study variations in these levels as a function of clinical and radiological signs commonly searched for during the follow-up of patients with a total hip arthroplasty. Material and methods: During a period of 30 months, a total hip arthroplasty (PVL®) was implanted in 53 patients suffering from degenerative hip disease. Forty-eight patients were assessed at a minimum follow-up of 32 months with physical examination and standard x-rays as well as serum assay of the specified metals using mass spectrometry on whole blood samples. The control group was composed of 56 patients scheduled for total hip arthroplasty. Results: At a mean follow-up of 44 months, 17% of the patients had a fair or poor functional score and 37% had radiological signs suggestive of femoral stem loosening. There was a significant increase in the serum level of cobalt compared with the control group. This increase was greater in patients with radiological signs of loosening. Discussion: The metal-on-metal couple does not appear to be the only couple which increases serum metal levels. Serum metal assay could be a diagnostic tool useful for following patients with total hip prostheses

Introduction: “Spongiosa metal” this unique implant surface was introduced in 1982 by ESKA implants Germany. Pore size was between 800 and 1500 microns with an overall porosity of 60%. The pore depth of the interconnecting surface structure reached up to 3000 microns. The purpose of this retrospective study is to report the long term results of Spongiosa Metal I cement less total hip prosthesis in Japan. Materials and Methods: Between 1986 and end 1990 total 113 prostheses were implanted and consecutive 106 implants could be evaluated. The all evaluated prosthesis combined 28mm ceramic head and polyethylene inlay. Results: Average follow up period was 17 years. 2 cups and 1 stem were revised by aseptic loosening. 2 stem breakage and 7 ceramic head fracture were seen while following up. 85% of the patients had retained the original prostheses (cup, stem, ceramic head, and inlay). Survival rate was investigated by Kaplan-Meier method. Survival rate for the cup component was 95%, and for the stem component was 93%. Discussion: Main reason of the revision surgery was the ceramic head fracture (7 implants 6%). We thought that beating with the hammer when we install the ceramic head to the taper was one problem. On the other hand, few aseptic loosening was seen while following up. These results suggest that spongiosa metal system can bear for long term of use. Conclusion: 85% of the patients had retained the original prostheses average 17years following up period. Main reason for the revision surgery is ceramic head fracture. We are convinced with this spongiosa metal surface can bear long term of use

The Kent hip is a distally-locked femoral stem which was developed to address severe proximal bone loss, severe bony deformity and peri-prosthetic fracture.

We reviewed the results of 145 consecutive Kent hips implanted into 141 patients between 1987 and 2000. The indications for implantation were aseptic loosening (75 hips), septic loosening (two), peri-prosthetic and prosthetic fracture (37), severe bony deformity (24), and fracture through a proximal femoral metastasis (seven).

The median time to full weight-bearing after surgery was two days and the mean length of follow-up was 5.1 years (2 to 15). Further revisions were required for 13 femoral stems. With removal of the stem for any reason as an end-point, the cumulative survival at five, ten and 15 years was 93%, 89% and 77%, respectively. In patients aged ≥ 70 years, the cumulative survival at 15 years was 92%, compared with 68% in those aged < 70 years. Because of these findings, we recommend the use of interlocking stems in patients aged ≥ 70 years, particularly in those with a peri-prosthetic fracture, for whom alternative methods are limited. Outcome scores and survival data, compared with other systems, indicate that the Kent hip should be used with caution in younger patients.

SL-PLUS MIA stem (Smith & Nephew Orthopaedics AG) is a modified implant of Zweymuller type SL-PLUS standard stem (Smith & Nephew Orthopaedics AG). We constructed finite element (FE) models and analysed equivalent stresses in the femur. In addition, we measured bone mineral density (BMD) in the femur by dual-energy X-ray absorptiometry (DEXA) after THA. The purpose of this study was to investigate the equivalent stress and to compare the results of the FE analyses with changes in BMD after THA. Twenty-one patients (18 women and 3 men) who underwent primary cementless THA with SL-PLUS MIA or SL-PLUS formed the basis of this study. Eleven patients received SL-PLUS MIA and ten patients received SL-PLUS. Zones were defined according to Gruen's system (zones 1∼7). Computed-tomography (CT) images of the femur were taken before and at 1 week after THA. FE models of the femur and prosthesis were obtained from CT data by Mechanical Finder (Research Center of Computational Mechanics Inc., Tokyo, Japan), software that creates FE models showing individual bone shape and density distribution. Equivalent stresses were analysed in zones 1 to 7 and compared to the DEXA data. FE studies revealed that there was no significant difference in equivalent stress between SL-PLUS MIA and SL-PLUS. BMD was maintained after THA in zones 3, 4, and 5, whereas BMD decreased in zones 2, 6, and 7. In zone 1, BMD decreased in SL-PLUS MIA stem group by 14%, while BMD was maintained in SL-PLUS standard stem.

Introduction: The search for a gold standard uncemented hip prosthesis with long term results matching cemented Charnley implants continues. It has been suggested that biological fixation would reduce the incidence of aseptic loosening caused by cement and polyethylene particles. The ABG (Howmedica) is a titanium alloy stem with an anatomic design and a modular head option of vitallium or ceramic. The cup is hemispherical and is fully coated with hydroxyapatite while the stem is proximally coated for metaphyseal fixation. We present a prospective series of 100 Consecutive patients with an immediate term follow up. Methods: 100 patients who had an ABG prosthesis inserted between 1991 & 1996 were included in the study. All patients were operated upon by the senior author or under his direct supervision. Patients underwent a preoperative assessment including a detailed history, measurement of range of motion, Postel Merle D’Aubigne scoring and ADL assessment. Clinical and radiological review was Conducted at 3 months, 6 months, 1 year and then at yearly intervals. At each visit Patients were questioned regarding the presence of any thigh pain and Complications. All patients were clinically evaluated, Postel Merle D’Aubigne Score was obtained and ADL status assessed. AP and lateral radiographs were Taken and studied. Polyethylene wear was measured by using the Livermore Method. The Kaplan- Meier method was used to explore the survival pattern of the implants. Results: The mean age of the patients was 52 years (range 23–72). Follow up ranged from 3 To 8 years (mean 5 years ). The mean preoperative Postel Merle D’Aubigne score Was 7 ( range 0–14) and mean score at final follow-up was 17.7(range 15–18). Only 4 patients complained of thigh pain and most had dramatic and lasting improvement of the ADL status. Complications included 3 dislocations and 2 Superficial infections. Non progressive lucencies were noted in 6 stems and 2 cups. No stems were loose and one patient had a loose cup and is awaiting surgery. A high rate of superior polethylene wear of 0.2mm/year was identified in a Number of patients yet the survivorship was 99% after an average 5 year follow up. Conclusion: Our results demonstrate the efficacy and excellent medium term outcome of the ABG prosthesis. A higher rate of complications in the first 2 years reiterates the lesson that every surgeon has to complete a learning curve before being technically comfortable with a new prosthesis. Of concern was the high rate of superior polyethylene wear although this did not effect the survivorship

Purpose: A spacer can be used for two-phase replacement of an infected total hip prosthesis. The goal is to facilitate reimplantation by avoiding soft tissue retraction. Several types of spacers can be used. We searched for a spacer which avoids wear debris due to methacrylate friction against bone, delivers a local antibiotic, is easily removed, and does not worsen bone damage. Since 1995, we have used a Charnley Kerboull type prosthesis as a spacer. The purpose of the present study was to 1) verify the absence of spacer-related complications, 2) assess outcome in terms of cure of infection and improved function. Material and methods: We used 14 articulated spacers for two-phasee prosthesis replacement in nine men and five women, mean age 64 years. Erythrocyte sedimentation rate was 32 and C-reactive protein was 17. The mean Postel-Merle d’Aubigné (PMA) score was 3+5+2. All patients were reviewed at a minimum 37 months follow-up. Technique: The approach was generally a digastric trochanterotomy, associated with a more or less extensive femoral procedure (depending on the length of the plug to remove) to achieve removal of all implants and cement. A small-size polyethylene cup was inserted with cement delivering at least one antibiotic on a Surgicel bed to facilitate later extraction. A long small-diameter femoral stem was then inserted (bridging the femoral window) and blocked with cement, also on a Surgicel bed. Partial then total weight bearing was authorised between the phases. Results: There were no dislocations. All patients achieved total weight bearing between the two phases. The same germ identified at the first operation was also identified at the second in two patients, requiring prolonged antibiotic therapy. There was one septic failure, in a different patient. The mean PMA score was 5.7+5.8+5.2. Conclusion: This technique avoids methacrylate wear induced by classical spacers and does not modify polymorphonuclear chemotactism, facilitating the efficacy of medical treatment. Patient comfort is also improved between the two phases and muscle atrophy, which could compromise long-term function, is avoided

Total Hip Arthroplasty (THA) is a well-established, cost-effective treatment for improving function and alleviating pain in patients who have disabling hip disease with excellent long-term results. Based on the excellent results, there is an ongoing trend for THA to be performed in younger and more active patients, having higher physical demands on their new total joints.

Polyethylene (PE) wear and its biological consequences are one of the main causes of implant failure in THA. Macrophages phagocytise PE wear particles and this will result in osteolysis and loss of periprosthetic bone. The risk of these complications can be estimated in relation to the amount of volumetric wear based on two assumptions: that the number of PE particles dispersed in the peri-prosthetic tissues is controlled by the amount of PE wear; and that the development of osteolysis and the resulting aseptic loosening is triggered by these PE particles. Based on these assumptions, a model was developed to estimate the osteolysis-free life of a THA, depending on the Linear Wear Rate (LWR) and femoral head size of the PE bearing.

A review of the literature was conducted to provide an estimate of the radiologic osteolysis threshold based on the volumetric wear of the PE bearing. This review demonstrates that this radiologic osteolysis threshold is approximated 670 mm3 for conventional PE. The osteolysis-free life of the THA was estimated by simply dividing this threshold volume by the annual Volumetric Wear Rate (VWR) of the bearing. The annual VWR is basically controlled by two parameters: (1) annual LWR and (2) head size, and was calculated by using published formulae.

For 28 mm heads, following osteolysis-free life was determined in function of the annual LWR. LWR: 10 µm/y => 116.6 years / LWR: 25 µm/y => 46.6 years / LWR: 50 µm/y => 23.3 years / LWR: 100 µm/y => 11.6 years. For 40 mm heads, following osteolysis-free life was determined in function of the annual LWR. LWR: 10 µm/y => 57.1 years / LWR: 25 µm/y => 22.9 years / LWR: 50 µm/y => 11.4 years / LWR: 100 µm/y => 5.7 years.

The osteolysis-free life determined by this model is in good agreement with the clinical results of PE bearings having a 28 mm head size and demonstrates that extreme low LWRs are mandatory to assure a descent osteolysis-free life for THA (PE bearings) using large heads, such as 40 mm. For such head sizes, small variations of the LWR may have large impacts on the osteolysis-free life of the THA.

INTRODUCTION. Cementless Total Hip Replacement surgery is a well established procedure for relative young patients with severe hip disease. Excellent long term clinical results have been published on the performance of the femoral component. With growing clinical experience, our concern focused on excessive wear of the Ultra High Molecular Weight Polyethylene (UHMWPE) ringloc liner of the Mallory Head cementless Total Hip Prosthesis. After its introduction in our clinic in 1997, this implant is still in use without any modification. We were concerned that due to premature liner wear, the performance of this implant would not be compliant with the international guideline on implant survival (NICE guidelines: at 10 year follow up, 90% of all implants should still be in situ). Our objective was to establish the amount of liner wear in our first 200 MH implants. METHODS. Our first 200 patients consecutively treated with Mallory Head prostheses were followed up to obtain a recent digital image. Follow up was complete for 181 (90.5%) of our 200 patients. Ten had died and nine were not able or willing to come for follow up. The mean duration of follow up was 8.3 years (range: 8–13). The 181 recent digital images were classified as either excessive wear or no excessive wear by two independent orthopedic surgeons. Next, liner wear was measured in the 2D frontal plane using PolyWare Pro/3D Digital Version Rev 5.1 software (Draftware Developers, Conway, USA). A threshold for excessive liner wear was set at 0.2mm/year, according to literature. RESULTS. Using software for measuring PE wear, 46.7% of all patients had excessive UHMWPE wear (> 0.2mm/yr). There was no relation between the amount of wear and BMI, gender, component size or the acetabular inclination angle. Thirteen patients (6.5%) were revised. Nine of these revisions were for excessive liner wear or aseptic loosening (4.5%). For now, our series of cementless Mallory Head prostheses is compliant with the NICE guideline on implant survival. However, with the measured amount of wear we expect to see a significant increase in the number of revisions for liner wear in the near future. DISCUSSION. Our clinical observation of premature UHMWPE wear proved correct. The measured amount of UHMWPE wear is consistent with the few other studies published on this subject. Although we present a retrospective study, limiting the strength of our results, we have included a large group of patients with acceptable loss to follow up. It is unclear if the observed wear will lead to a sharp increase in the number of revisions within the next few years. Possibly, future revisions will be complicated by loss of acetabular bone stock following the pathofysiological reaction to wear particles. Our results can probably be generalised for any district hospital

Introduction: Unique spongiosa like surface structure was introduced in 1982 by ESKA implants Germany. It is called “Spongiosa-Metal I surface” The purpose of this retrospective study is to report and compare long term results of Spongiosa Metal I total hip prosthesis in Japan and Germany. Method: In Japan, between June 1986 and August 1990 total 113 prostheses were implanted and consecutive 106 implants could be evaluated. In Germany, between May 1983 and December 1985 total 209 prostheses were implanted and consecutive 165 implants could be evaluated. The all evaluated prosthesis combined ceramic head and polyethylene inlay. Results: In Japan, average follow up period was 17 years. 85% of the patients had retained the original prostheses (cup, stem, ceramic head, and inlay). Survival rate was investigated by Kaplan-Meier method. Survival rate for the cup component was 95%, and for the stem component was 93%. In Germany, average follow up period was 21.8 years. 88.5% of the patients had retained the original prosthesis. Survival rate for the cup component was 95%, and for the stem component was 85%. Discussion: Main reason of the revision surgery was the ceramic head fracture (7 implants 6%) in Japan and the stem component loosening (14 implants 8%) in Germany. There was no ceramic head fracture in Germany. We thought that beating with the hammer when we install the ceramic head to the taper was one problem. Stem loosening was seen in undersized stem component. On the other hand, survival rate for the cup component was 95% in Japan and Germany. This was good result in comparison with other reports about long term survival. Conclusion 85% of the patients had retained the original prostheses average 17years in Japan and 88.5% average 21.8 years in Germany. Main reason for the revision surgery is stem loosening and ceramic head fracture. Survival rate for the cup component was 95% in Japan and Germany. We are convinced with this spongiosa metal surface can bear long term use

Aims: The purpose of this study is to present our experience with the A.B.G.-I hip system after ten years follow-up. Methods: Prospective study about 162 hip prosthesis implanted from 1990 to 1992. We have assessed clinical and radiographic results immediately before surgery and at a minimum follow-up of ten years. Statistical analysis has been developed with S.P.S.S. Results: Sex distribution of the 162 initial prosthesis: 50.71% men and 49.29% women; affected side: right in 50.71%, left in 49.29%. First hip disease: rheumatoid arthritis in 7.48%, osteoarthritis in 77.57% and avascular necrosis in 14.95%. At this moment only 102 prosthesis continue on study: 8 revised (7.27%), 21 patients died (20.39%), 28 disappeared (17.18%) and 4 (2.45%) have not been considered. Clinical assessement let us be very satisþed, with a Merle DñAubigne score improving from 7.9 preoperative to 15.8 at ten years follow-up. Clinical results have been: excellent in 54.81%, good in 27.88% and bad in only 3.85%. Radiographic results are worse than expected: 84.11% of femoral stems developed some grade of stress shielding phenomenon and polyethylene inners wore excessively (mean value = 1.77 mm). The inßammatory response to polyethylene particles originated osteolytic lesions in 88.78% of femurs and 56.48% of periacetabular bones. Today 15.53% of patients in study are waiting for a revision. Conclusions: In spite of the very good clinical results, the radiographic assessement is very concerning. We think the þrst problem is the bad quality of polyethylene inner, that is responsible for grave osteolytic lesions

Aims

The aim of this study was to evaluate blood metal ion levels, leucocyte profiles, and serum cytokines in patients with a total hip arthroplasty (THA) involving modular dual-mobility components.

Background

The two-stage revision strategy has been claimed as being the “gold standard” for treating prosthetic joint infection. The one-stage revision strategy remains an attractive alternative option, however, its effectiveness in comparison to the two-stage strategy remains uncertain. A systematic review and meta-analysis was conducted to compare the effectiveness of one- and two-stage revision strategies to prevent re-infection after prosthetic hip infection.

Introduction

Post op cup anatomical and functional orientation is a key point in THP patients regarding instability and wear. Recently literature has been focused on the consequences of the transition from standing to sitting regarding anteversion, frontal and sagittal inclination. Pelvic incidence (PI) is now considered as a key parameter for the analysis of sagittal balance and sacral slope (SS) orientation. It's influence on THP biomechanics has been suggested. Interestingly, the potential impact of this morphological angle on cup implantation during surgery and the side effects on post op functional orientation have not been studied.

Our study explores this topic from a series of standing and sitting post-op EOS images

In the present study we describe the clinical results of the Scientific Hip Prosthesis® (SHP). With the goal of smoothening cement-bone interface stress peaks, the SHP was developed using shape optimization algorithms together with finite element modelling techniques. The resulting shape and cement stresses are seen in Figure 1. The introduction of the SHP prosthesis was performed in a stepwise fashion including a RSA study performed by Nivbrant et al¹. RSA studies for prosthetic types that are in long-term use are of great value in predicting the survivorship related to the migration rate and pattern for that specific type of prosthesis. If a stem in a patient shows a much higher migration rate than the typical one, the stem may be identified as at high-risk for early loosening. The study of Nivbrant et al¹ revealed unexpectedly high migration values and it was stated that the SHP stem was not the preferred stem to use despite the good Harris Hip Score and Pain score at two years follow-up.

In the present study the clinical results of a single surgeon study consisting of 171 hips with a follow-up of 5–12 years were evaluated. The mean follow-up was 8.2 years (5.0–12.0). The survival rate was 98.8% at ten years follow-up for aseptic loosening of the stem. The mean Harris Hip Score at 10 year follow-up was 89.2 ± 7.5. This study therefore indicates that a new prosthetic design may function clinically rather well, despite the relatively high migration rates which have been reported.

In case of a RSA study with a new prosthesis it may not be so evident what the expected “typical” migration rate or pattern is. So in order to predict early loosening the typical migration rate has to be known. Perhaps typical migration rates can be established using standardized cadaver migration experiments or computer simulation models techniques. Since these standardized tools are currently not available, the prediction of clinical survival of new prosthetic components remains a challenging task and the interpretation of migration rates with new designs should be considered with much caution.

Background

The worldwide withdrawal of the DePuy Articular Surface Replacement (ASR) device in both its resurfacing and total hip replacement (THR) form on 26 August 2010, after 93,000 were implanted worldwide, has had major implications. The 2010 National Joint Registry for England and Wales quoted figures of 12-13% failure at five years; however these figures may be an underestimate.

Purpose: Osteolysis is one of the important issues during the life of noncemented total hip arthroplasty (THA). The purpose of this study was to evaluate a series of 228 THA using an ABG-1 implant to determine the incidence of osteolysis and contributive factors.

Material and methods: This series of 228 THA using noncemented ABG-1 anatomic implants coated with hydroxyapatite was implanted in 210 patients, 116 women and 112 men, mean age 62.2 years. The indication was primary osteoarthritis (53.6%), primary necrosis (21.5%), posttraumatic osteoarthritis (11.8%), rheumatoid disease (8.3%) and hip dysplasia (4.8%). The bearings were, 200 zirconium-polyethylene (87.7%), 28 metal-polyethylene (12.3%). At mean 88.6 months follow-up, a minimum 60 months postoperatively, we reviewed 163 patients (37 patients died without revision, 28 (12.3%) were lost to follow-up, and 17 had undergone a revision procedure). We analyzed osteolysis on the digitalized radiograms using the Delee-Charnley classification to which we added a fourth retroacetabular zone. Polyethylene wear was measured with the Imagika(r) software using the method described by Martell.

Results: The 17 cup revisions (8.5%) were required for instability (4 pt), loosening (4 pt), osteolysis (4 pt), infection (3 pt), and limping (1 pt). Overall implant survival was 92.1%. Implant survival, considering loosening and osteolysis as failure, was 96.1%. Mean wear at last follow-up was 1.26 mm, for an annual average of 0.17 mm (0.04 – 0.69 mm/yr). Acetabular osteolysis was observed in 41.6% of cases, mainly in the Delee-Charnley zone 1, but was also found in all the other zones. The average surface area was an estimated 223 mm2. Possible factors favoring osteolysis were: aetiology, age, gender, activity level, body mass index, Charnley ABC classification, presence of preoperative acetabular defects, cup size, polyethylene insert thickness, position of the insert rim, cup inclination, complementary fixation, bearing type, polyethylene offset and wear. There was a statistically significant relationship between osteolysis and: the Charnley classification (p=0.012), presence of preoperative acetabular defects (p=0.0034), cup inclination angle (p=0.035), cup size (p=0.042), polyethylene thickness (p< 0.01), use of complementary fixation (p=0.048), and polyethylene wear (p=0.0011). Paradoxically, we did not find any relationship with gender, age, body mass index, and the other factors.

Discussion: This analysis demonstrated the determining causes of osteolysis: time, polyethylene thickness, polyethylene wear, the Zicronium-polyethylene bearing. Wear was probably not only the consequence of the Zicronium-polyethylene bearing but was also related to the quality of the polyethylene, and the instability of the insert. Diffuse osteolysis is favored by orifices in the first-generation cups which have been eliminated in the ABG-2 cups.

A consecutive series of 30 total hip replacements using a hydroxyapatite (HA)-coated, modular implant (Omnifit) was followed clinically and by roentgen stereophotogrammetric analysis for two years and compared with two control groups, one of 27 cemented Charnley sockets and one of 40 cemented Charnley stems.

Omnifit sockets with a central gap between the dome of the socket and the acetabular bone in the postoperative radiographs, migrated less than sockets without such gaps (p = 0.01). After adjustment for patient-related factors (age, gender and weight), no significant difference was found between the two prostheses with respect to micromotion and wear.

We conclude that the early fixation of the HA-coated Omnifit prosthesis compares with that of the cemented Charnley prosthesis.

We reviewed 82 primary arthroplasties (in 71 patients) in which cementless porous-coated hip prostheses were used. The mean age of the patients at operation was 52 years (24 to 86); they were followed up for an average of 62.1 months (60 to 66). The diagnosis was avascular necrosis of the femoral head in 35%, fracture of the femoral neck in 24%, primary osteoarthritis in 16% and miscellaneous in 25%. The average preoperative Harris hip score was 56.7 points and the average postoperative score was 83.3 points. Eight hips (10%) had component loosening; four had been revised and four were awaiting revision. In 27 hips (33%) there was a radiolucent line wider than 2 mm in zones 1 and 7. In 55 hips (67%) there was calcar resorption of more than 10 mm. Twenty patients (28%) complained of thigh pain although they had no radiographic evidence of loosening of a component. Factors that may have contributed to the poor clinical and radiographic results were: 1) inadequate surface area for bone ingrowth, particularly on the lateral aspect of the upper part of the prosthesis, 2) poor initial fit of the stem in the metaphysis, which resulted in cantilever motion of the proximal part of the stem about the well-fixed distal stem, and 3) the collar of the prosthesis, which prevented it from subsiding to a naturally stable position and caused damage to the calcar.

This abstract is currently withdrawn to allow an independent review of findings to take place.

Between January 1984 and January 1986, 131 porous-coated anatomic total hip replacements were performed in 119 consecutive patients. Of these, 100 patients (110 hips) who were alive at a minimum of 18 years after replacement were included in the study. The mean age of the patients at surgery was 48.4 years and that of surviving patients at the latest follow-up was 67.8 years. The mean duration of the clinical and radiological follow-up was 19.4 years (18 to 20).

The mean Harris hip score initially improved from 55 points before to 95 points at two years after operation, but subsequently decreased to 91 points after six years, 87 points after 11.2 years, and 85 points after 19.4 years. At the final follow-up, 23 hips (18%) of the entire cohort and 21% of survivors had undergone revision because of loosening or osteolysis of the acetabular component and eight hips (6%) of the entire cohort and 7% of survivors for loosening or osteolysis of the femoral component. Only four femoral components (4%) were revised for isolated aseptic loosening without osteolysis and two (2%) for recurrent dislocation. On the basis of these long-term results, the porous-coated anatomic femoral component survived for a minimum of 18 years after operation while the acetabular component was less durable. The findings identify the principles of uncemented joint replacement which can be applied to current practice.

Aim

The objective of this study was to evaluate the intermediate term clinical and radiological results of a new short stem hip implant.

After a few years from its introduction, the limits of the THA became evident, mainly due to high rates of mobilization for polyethylene wear and to the release of metal ions from MOM and MOP couplings.

Ceramic bearings were thus introduced in surgery to obtain lower levels of friction and wear.

These issues have now been well recognized by several studies, which show that ceramic-on-ceramic joint has the lowest wear rate among various articulations and that ceramic particles induce less macrophage reaction and decrease cytokine secretion, allowing to have little periprosthetic osteolysis.

After the first results in the late 70′s and early 80′s, the mechanical reliability was improved due to the manufacturers' efforts to reduce the ceramic fragility evolving average grain microstructure and lowering the degree of impurity.

Betterment and standardization of production have led to 3^rd generation alumina, Biolox Forte in 1994, that achieved a lower incidence of fracture.

The purpose of our study has been to assess long-term follow-up results of alumina-on-alumina 3^rd generation ceramic total hip cementless arthroplasty performed at our institution from January 1995 to December 2000.

We prospectively followed more than 200 patients operated of THA for primary or secondary hip osteoarthritis analyzing clinical and radiographs features.

In this period, the total hip replacement were performed by a single surgeon, who is the senior author (A.T.) in our Institution.

All patients were clinically examined to confirm the diagnosis and all of them were checked with a standard plain radiographs in two projections and, when necessary, the radiographic examination was completed by CT scans.

The same prosthesis was used in all patients, a 3^rd generation alumina COC articulation, composed of a hemispherical titanium alloy cup and a 28-mm alumina ceramic femoral head. The modular ceramic head was fixed to a 12/14 taper cone.

Proximally plasma-spray hydroxyapatite coated Ti alloy stems completes the implant features. Modular necks were used in retro or anteversion and varus or valgus offset, allowing changes in neck-shaft angle and giving a perfect intraoperative stability.

Clinical assessment was performed using the Merle-D'Aubigne and Postel hip score. Each patient was assessed before surgery, after 30 days, afterwards at 4 months and annually after surgery.

The mode of femoral component fixation was radiographically classified as bone ingrowth fixation, stable fibrous fixation or unstable fixation, according to the criteria Engh-Bobyn.

Osteolysis was evaluated on the femoral side at each Gruen zone. Osteolysis on the acetabular side was evaluated by DeLee and Chanley zone.

Our study has concluded that cementless modular hip arthroplasty with 3^rd generation ceramic-on-ceramic bearing, with a 13 to 18 years follow-up, shows an excellent survivorship, in particular for the very low volume release of microparticles during friction, which consequently reduction of cytokine release, thus diminishing the risk of periprosthetic osteolysis and loosening of implant components.