BACKGROUND:. Although most radiographs used for polyethylene wear measurements have been taken with the patient in the supine position in order to assess penetration by the femoral head into the acetabular polyethylene socket, we have questioned the effect of weight-bearing on the position of the head within the socket. The current study aimed to determine the effect of weight bearing, i.e. standing on the two-dimensional radiographic position of the femoral head within the socket. PATIENTS AND METHODS:. A total of three hundred and fifty patients (three hundred and eighty three hips) who had had a total hip arthroplasty had digital radiographs made a set of anteroposterior radiographs for each patient: one radiograph was made with the patient supine and one was made with the patient standing in full weight bearing on the replaced hip. The patients were divided into the following two groups: 1) seventy-five patients (eighty-three hips) with conventional polyethylene (CON) (group-1); 2) two hundred and seventy-five patients (three hundred hips) with highly cross-linked polyethylene (XPL) (group-2). The set of radiograph was taken at three weeks postoperatively and at the time of semiannual follow-up. The average ceramic femoral head penetration was measured with radiographs taken in the standing or supine position at the final follow-up and compared with those of three weeks postoperatively. A single researcher with use of a computerized measurement system performed all measurements on the radiographs of the two-dimensional position of the head. Follow-up period were 13.5 ± 1.0 (range. 11.0–15.5) years in group-1 and 7.6 ± 2.1 (range. 5.0–12.6) years in group-2. RESULTS:. Linear penetration rates in group-1 were 0.172 ± 0.069 mm/year in supine position and 0.178 ± 0.069 mm/year in standing position (p < 0.05, paired t-test; r. 2. = 0.88), and the rates in group-2 were 0.029 ± 0.024 mm/year and 0.035 ± 0.027 mm/year respectively (p < 0.0005, paired t-test; r. 2. = 0.16). The mean ceramic head penetration rate in XPL socket showed 80 to 83% reduction compared with those in CON. CONCLUSIONS:. We found significant difference between the average total ceramic femoral head penetration between supine and standing radiographs in using both CON and XPL socket. Standing radiographs were useful and recommended for polyethylene socket wear measurements. Figure legend. Fig. Wear measurement: With use of a computerized measurement system, the thickness of the polyethylene socket (a) was measured along a line connecting the center of the ceramic femoral head to the outer border of the socket at its shortest distance. The wear rate was determined by comparing the thickness in the latest follow up radiograph with the thickness in the initial postoperative radiograph at the same location. Each radiographically measured value was corrected for magnification by a factor derived from comparing the diameter of the ceramic head on the radiograph (b) with its known diameter of 22.225 mm

Twenty-two high-density polyethylene sockets from Charnley low-friction arthroplasties have been studied. Acrylic casts and shadowgraph techniques were used to measure both the real and radiographic rates of wear; these rates showed a significant correlation. In the sagittal plane, nine of the sockets had worn lateral to a line drawn vertically from the centre of curvature of the socket, 12 had worn medial to that line and only one was worn exactly in the line. In the coronal plane, nine sockets had worn in front of a similar vertical line, two behind that line and 11 had worn exactly in the line. Evidence of impingement of the neck of the stem onto the rim of the socket was found in 14 patients; this is considered to be one of the causes of socket loosening. The obvious solution is to reduce the diameter of the neck of the stem from 12.5 mm to 10 mm; provided that it is made of cold-formed, high nitrogen-content stainless steel, this narrower neck is strong enough not to fracture.

Limitations of the range of motion (ROM) of total hip prostheses lead to impingement causing dislocation and material failure. Due to wear, the femoral head penetrates polyethylene (PE)-sockets by about 0,1 mm/year (ceramic on PE) and 0,2–0,6 mm/year (metal on PE). Wear rate increases with steep acetabular cup position. In contrast to polyethylene, wear of alumina-ceramic cups appears to be independent from inclination angle and is only about 0,001 mm/year. Wear and design features may restrict the artificial joint mobility. The purpose of this study is to determine the effects of head penetration on ROM in relation to different cup positions.

Computer simulation was carried out with a three-dimensional CAD-program. 3-D models of modular cup, spherical head, and stem with cylindrical neck and 12/14 taper were generated. The femoral head was shifted 0, 1, 2, and 5 mm towards the pole of the cup. According to mean direction of penetration measured in retrieved PE-sockets, femoral head was also moved 0, 1, 2, and 5 mm in vertical direction. The joint motions were measured at different cup positions.

The study demonstrates that ROM is clearly reduced by increasing head penetration. After 2 mm penetration, e.g. maximum flexion is reduced by approx. 15° at 45° cup inclination. Restriction of flexion is more pronounced in the vertical penetration path. If the socket is placed in more horizontal position, less ROM of flexion, extension and abduction is observed. With steeper cup positions ROM of flexion increases but, as well as risk of dislocation, wear and penetration rate of PE sockets increase.

Modern hip prostheses should provide sufficient joint movements, precise implant positioning and low wear bearing couples avoiding penetration of femoral head. Additionally, design aspects like liner geometry, head-neck ratio have to be considered preventing impingement, dislocation or early failure by aseptic loosening.

It is probable that both genetic and environmental factors play some part in the aetiology of most cases of degenerative hip disease. Geneticists have identified some single gene disorders of the hip, but have had difficulty in identifying the genetics of many of the common causes of degenerative hip disease. The heterogeneity of the phenotypes studied is part of the problem. A detailed classification of phenotypes is proposed. This study is based on careful documentation of 2003 consecutive total hip replacements performed by a single surgeon between 1972 and 2000. The concept that developmental problems may initiate degenerative hip disease is supported. The influences of gender, age and body mass index are outlined. Biomechanical explanations for some of the radiological appearances encountered are suggested. The body weight lever, which is larger than the abductor lever, causes the abductor power to be more important than body weight. The possibility that a deficiency in joint lubrication is a cause of degenerative hip disease is discussed. Identifying the phenotypes may help geneticists to identify genes responsible for degenerative hip disease, and eventually lead to a definitive classification.

BACKGROUND. Hybrid total hip arthroplasty (THA) commonly recognized as cementless hemi-spherical acetabular component combined with cemented femoral stem. We have done so called “reverse” hybrid THA with cemented socket and cementless stem and compared with all-cemented THAs. PATIENTS AND METHODS. We have been collecting data on total hip arthroplasty since November, 1993. Reverse hybrid hip replacements were used mainly from February, 2001. We evaluated data on 272 reverse hybrid THAs (223 patients) from this year onward until May, 2010, and compared the results with those from 283 all-cemented THAs (237 patients) between 1993 and May, 2010. Eighty percent or more of patients had diagnosed as secondary osteoarthritis of the hip joint due to dysplasia in our hospitals. Highly cross linked ultrahigh molecular polyethylene (CLP) socket was introduced in October, 1999. We used conventional (not cross linked polyethylene) socket for 82 hips (cemented group-1) operated before October, 1999 and CLP socket for 201 hips (cemented group-2) in all-cemented cases. We used the Kaplan-Meier method for estimation of prosthesis survival and relative risk of revision. The endpoint was radiological loosening or revision. Socket linear wear rates were also assessed in radiographically. Clinical assessment was performed using the Japanese Orthopedic Association (JOA) scores and Merle d'Aubigne & Postel scores. RESULTS. We have 12 hips (11 sockets and 1 stem) with radiological loosening in all cemented series and no hips in reverse hybrid series. A case with stem loosening in all cemented THAs had fractured stem without bony support due to massive osteolysis caused by heavy polyethylene wear. All of the loosening cases had conventional polyethylene socket and six of them were revised. Socket linear wear rates were calculated as 0.171 +/− 0.069, 0.030+/− 0.027, and 0.035+/− 0.026 mm per year for cemented group-1, group-2 and reverse hybrid cases, respectively. Clinical scores were significantly improved those at the time of final follow up compared with those of preoperative assessment. There were significant differences between conventional and cross linked polyethylene cases. We found no significant difference survival to that from cemented THR at 12 years (all cemented: 96.1% (95% CI: 92.7–99.1); reverse hybrid: 100%) (Figure 1). DISCUSSION AND CONCLUSION. With a follow-up of up to 12 years, reverse hybrid THAs performed well, and similarly to all-cemented THRs from the same time period. The reason for loosening was mainly bone loss and osteolysis due to polyethylene socket wear. It is no problem if the stem was installed by cemented or cementless fixation, because the rates of stem loosening were very low in the current study. The reverse hybrid method might therefore be an alternative to all-cemented THR. Longer follow-up time is needed to evaluate whether reverse hybrid hip arthroplasty has any advantages over all-cemented THA

Introduction. The long-term wear performance of highly cross-linked polyethylene (HXLPE) in cemented total hip arthroplasty (THA) has rarely been reported. Here we report a prospective randomized comparative analysis of radiographic wear after a minimum follow-up of 10 years in cemented THAs with either HXLPE or conventional polyethylene (CPE), and assess its clinical relevance. Patients and Methods. From 1999 to 2001, we conducted 94 primary cemented THAs with a 22.225-mm head at our hospital as part of a prospective randomized trial. All surgeries were performed using a direct lateral approach with a trochanteric osteotomy (Dall's approach). The patients were divided into 4 groups. Twenty-six hips in group A were implanted with CPE sockets against zirconia heads and Charnley-type stems. HXLPE sockets (Aeonian, Kyocera Medical Corp) were implanted in all hips in the other 3 groups. Twenty-five hips in group B were implanted with zirconia heads and KC stems (Kyocera Medical Corp), 23 hips in group C with zirconia heads and distal cylindrical stems, and 20 hips in group D with stainless steel heads and C-stem (DePuy Inc). The sockets were highly cross-linked by gamma irradiation at a dose of 35 kGy, heat annealed at 110ºC, and sterilized with 25 kGy of gamma irradiation in nitrogen. For radiographic evaluation, anteroposterior radiograms were taken for each patient annually, and every two years postoperatively for wear analyses. Two-dimensional head penetration was measured on each postoperative radiogram using a computer-aided technique. Results. Wear measurements were performed for 59 cases followed up over 10 years. Linear wear rates were 0.138±0.074 (mm/year±SD) for group A, 0.010±0.015 for group B, 0.013±0.020 for group C, and 0.012±0.027 for group D. Linear wear rates differed significantly between group A and other groups, and no significant difference was found among groups B, C, and D. There were four revision cases. Among them, two sockets of group A were revised for aseptic loosening at 7 and 14 years postoperatively with linear wear rates of 0.749 and 0.153 mm, respectively. Two stems of group B and C were revised for aseptic loosening at 10 and 9 years postoperatively with linear wear rates of 0.007 and 0.041 mm, respectively. There were no other cases with aseptic loosening in any group. Osteolysis was found in 10 cases (group A: 7, group B: 1, group C: 1, group D: 1), and there was a significant difference in linear wear rates between the cases with and without osteolysis (0.157±0.083 and 0.030±0.053 mm/year±SD respectively). Discussion. The two revision cases of HXLPE did not have aggressive socket wear, and possibly cement fracture caused osteolysis and stem instability. The results of this study indicate that there is a significant difference in wear rate between CPE and HXLPE, and it was evident that PE wear was associated with osteolysis and aseptic loosening of the socket

We report the long-term radiological results of 58 total hip arthroplasties (THA) using the Charnley offset-bore acetabular socket. Wear was measured at four sites and radiolucent lines and possible migration were recorded. Four cups were retrieved at revision and were examined using light microscopy, SEM and X-ray microanalysis. At a mean follow-up of seven years the mean wear in the DeLee and Charnley zone I was 0.4 mm and in zone II 0.26 mm. The wear rate was 0.06 and 0.04 mm/year, respectively. Progression of radiolucent lines was seen in five cases (8.6%). Three sockets (5.2%) were revised because of aseptic migration at a mean follow-up of 9.8 years and one socket for infection at two years. The offset-bore acetabular cup had excellent wear behaviour and a low migration and revision rate. We recommend that it should be considered in THA since the use of small cups is increasing, particularly in revision cases

Aim: To assess the factors affecting cup survivorship in cemented Total Hip Replacements carried out for DDH. Methods: A retrospective study of 292 cemented total hip replacements carried out at Wrightington. The hips were classified according to the Crowe and Hartofilakidis classifications. Revision was used as the end point for prosthetic survivorship. The results were analysed statistically using SPSS for Windows. Results: The mean age at time of surgery was 42.6 years with a mean follow-up of 15.7 years. The acetabulum was grafted in 48 cases. The commonest cause for revision was aseptic loosening of the acetabular component (88.3%). There was a higher rate of premature failure of the acetabular component with increasing severity of hip dysplasia, especially after 10years. There was a correlation with age of the patient, accelerated socket wear and previous pelvic osteotomy. There were higher rates of failure with the Charnley CDH stem and the offset bore cup. Conclusion: Factors having an adverse effect on cup survival are severity of hip dysplasia, younger age at time of primary surgery, accelerated polyethylene wear and previous pelvic osteotomy. Bone grafting of the acetabulum and the operating surgeon did not influence long term cup survival

In laboratory tests, the ultra-high molecular weight polyethylene used for the acetabular cups of Charnley hip prostheses has a very low wear rate against steel. In the body radiographic measurements indicate that the polyethylene wears more rapidly. In order to investigate this higher wear rate, the sockets of acetabular cups removed at post-mortem have been examined using optical and electron microscopy. It has been shown that a socket wears predominantly on its superior part and that this is a direct consequence of the orientation of the cup in the body and the direction of loading of the hip. In the worn region the femoral head in effect bores out a new socket for itself, a process which is visible with the naked eye after approximately eight years. Electron microscopy shows that the predominant wear mechanism is adhesion, but after about eight years the appearance of surface cracks suggests that surface fatigue is taking place in addition to this. Laboratory wear tests have shown that pure surface fatigue is not sufficient to account for the high clinical wear rate. Other deformation processes are suggested and discussed with regard to the higher clinical wear rate

Introduction: Approximately 0.5 % of patients with metal on metal hip replacements develop post operative pain which is thought to be due to an immune reaction to metal wear particles, known as Aseptic Lymphocyte Dominated Vasculitis Associated Lesion (ALVAL). Treatment usually requires revision to a non metal on metal hip.. Is the development of ALVAL more likely in those patients with high wear rates?. Methods: Retrieved Metal on Metal (MOM) hip implants; periprosthetic tissue and blood samples were obtained from patients (n = 18) undergoing revision for unexplained pain at a mean of 2 years post operatively. The following variables were measured:. linear wear rate (depth of the femoral head and acetabular socket wear patch/time from operation);. the diagnosis and severity of ALVAL from histological sections of periprosthetic tissue (Wilhert grading system);. pre-revision whole blood cobalt, and chromium levels using Inductively Coupled Plasma Mass Spectrometry. All implants and tissue samples were analysed against control samples from patients undergoing revision of MOM hips for fractured femoral neck or impingement. Results: Linear wear rates of retrieved implants, and blood levels of cobalt and chromium from patients with unexplained plain were greater than from control patients. Histolopathological analysis of tissue showed dense inflammatory infiltrates with healthy looking endothelial cells in all vessels from both patient groups. Discussion and Conclusion: A painful MOM hip was associated with high wear rates and blood metal levels. The local inflammatory response was similar to “ALVAL”, ie lymphocyte dominated, but not exclusive to those patients with unexplained pain. We question whether ALVAL represents a vasculitis, or merely a classical lymphocyte driven inflammatory tissue response to metal debris particles

Introduction and aims: To study the survivorship and subsidence patterns of the first 433 Exeter stems inserted between 1970 and 1975 by 16 different surgeons utilising first generation cementing techniques. Method: A survivorship study up to the 33rd year of follow-up was performed, the end-point being revision for aseptic stem loosening. Stem subsidence was measured in all survivors, as well as assessing the grade of cementing, ‘calcar’ resorption, visible cement fractures, focal lysis and radiolucent lines at the interfaces. Results: Of the 433 hips, 21 were revisions of previously failed hips. 21.7% of patients have had a re-operation of some sort including 3.69% for stem fracture, 3.46% for neck fracture (all from a group of 95 stems with excessively machined necks), 9% for aseptic cup loosening, 3.46% for aseptic stem loosening, 1.84% for infection and 0.23% for recurrent dislocation). For the overall series, with revision for aseptic stem loosening as the end-point, the survivorship is 91.42% (95%CI: 70.82 to 100%). The average age at operation of the survivors was 57.6 years. No significant bone-cement subsidence was found. Mean stem-cement subsidence was 2.15mm, most occurring in the first 5 years and in all but 1 being less than 4mm. Cementing grades were B in 65%, C in 27%, D in 8%. Resorption of the neck (13%) was associated with excessive socket wear or cement left over the cut surface of the neck (the ‘pseudocollar’). Visible cement fractures were found in 14%, none associated with focal lysis, which was seen in 11%. Conclusions: Although 21.7% of patients in this series of the first 433 Exeter hips to be inserted in Exeter needed a re-operation of some sort, the stem rarely required surgery for aseptic loosening and was associated with benign long-term X-Ray appearances in spite of 1st generation cementing

Introduction & Aims: To study the survivorship and subsidence patterns of the first 433 Exeter polished, totally collarless, double tapered, cemented stems that were inserted between November of 1970 and the end of 1975 by 16 different surgeons (13 of them in the training grades) utilising first generation cementing techniques. Method: A survivorship study up to the 33rd year of follow-up, using the contingency table method, was performed for all 433 hips, the end-point being revision for aseptic stem loosening. Stem subsidence in relation to the cement and the bone was measured in all survivors by a single observer on digitised films (magnified 200%) using the Orthochart™ software. Stem subsidence, the grade of cementing, ‘calcar’ resorption, visible cement fractures, focal lysis and radiolucent lines at the interfaces were assessed. Results: Of the 433 hips, 21 were revisions of previously failed hips. 21.7% of patients have had a re-operation of some sort including 3.69% for stem fracture, 3.46% for neck fracture (all from a group of 95 stems with excessively machined necks), 9% for aseptic cup loosening, 3.46% for aseptic stem loosening, 1.84% for infection and 0.23% for recurrent dislocation). For the overall series, with revision for aseptic stem loosening as the end-point, the survivorship is 91.42% (95%CI: 70.82 to 100%). When all cases lost to follow-up (28 hips) are regarded as failures, survivorship is 82.9% (95%CI: 58.37 to 100%). The average age at operation of the survivors was 55.7 years. No significant radiological subsidence between the cement and bone was found. Mean subsidence between the stem and the cement was 2.15mm, most occurring in the first 5 years and in all but 1 being less than 4. The maximum was 18mm (grade D cementing). Cementing grades were B in 65%, C in 27%, D in 8%. Resorption of the neck (13%) was associated with excessive socket wear or cement left over the cut surface of the neck (the ‘pseudocollar’). Visible cement fractures were found in 14%, none associated with focal lysis, which was seen in 11%. Conclusions: Although 21.7% of patients in this series of the first 433 Exeter hips to be inserted in Exeter needed a re-operation of some sort, the stem rarely required surgery for aseptic loosening and was associated with benign long-term X-Ray appearances in spite of 1st generation cementing

Introduction and Aims: To study the survivorship and subsidence patterns of the first 433 Exeter polished, totally collarless, double tapered, cemented stems that were inserted between November 1970 and the end of 1975 by 16 different surgeons (13 of them in the training grades) utilising first generation cementing techniques. Method: A survivorship study up to the 33rd year of follow-up, using the contingency table method, was performed for all 433 hips, the end-point being revision for aseptic stem loosening (including also a ‘worst case’ scenario). Stem subsidence in relation to the cement and the bone was measured in all survivors by a single observer on digitised films (magnified 200%) using the Orthochart™ software. Repeated measurements allowed the analysis of intra-observer errors. Stem subsidence, the grade of cementing, ‘calcar’ resorption, visible cement fractures, focal lysis and radiolucent lines at the interfaces were assessed. Results: Of the 433 hips, 21 were revisions of previously failed hips. 21.7% of patients have had a re-operation of some sort, including 3.69% for stem fracture, 3.46% for neck fracture (all from a group of 95 stems with excessively machined necks), 9% for aseptic cup loosening, 3.46% for aseptic stem loosening, 1.84% for infection and 0.23% for recurrent dislocation). For the overall series, with revision for aseptic stem loosening as the end-point, the survivorship is 91.42% (95%CI: 70.82 to 100%). When all cases lost to follow-up (28 hips) are regarded as failures, survivorship is 82.9% (95%CI: 58.37 to 100%). The average age at operation of the survivors was 57.6 years. No significant radiological subsidence between the cement and bone was found. Mean subsidence between the stem and the cement was 2.15mm, most occurring in the first five years and in all but one being less than four. The maximum was 18mm (grade D cementing). Cementing grades were B in 65%, C in 27%, D in 8%. Resorption of the neck (13%) was associated with excessive socket wear or cement left over the cut surface of the neck (the ‘pseudocollar’). Visible cement fractures were found in 14%, none associated with focal lysis, which was seen in 11%. Conclusion: Although 21.7% of patients in this series of the first 433 Exeter hips to be inserted in Exeter needed a re-operation of some sort, the stem rarely required surgery for aseptic loosening and was associated with benign long-term x-ray appearances in spite of 1st generation cementing

Introduction: In a pioneer study Oonishi et al (1988) found reduced socket wear with the use of polyethylene subjected to high radiation doses. This observation has stimulated the development of a new generation polyethylene. In addition to high radiation doses the plastic is also subjected to various types of heat treatment to reduce the amount of free radicals. The purpose of the present study is to evaluate one of the new highly cross-linked polyethylenes in a randomized controlled study of cemented THA. The hypothesis is that the improved wear resistance will reduce the prevalence of osteolytic lesions with long-term follow-up. Methods and materials: Patients in clinical and radiographic need of a THR with non-inflammatory osteoarthritis of the hip were randomized in two groups. Group 1 received a cemented Weber cup (Sulzer®, Switzerland) made of highly cross-linked (WIAM) polyethylene, group 2 got a conventional cup. All patients received a cemented Spectron (Smith & Nephew, USA) with a 28mm cobalt-chromium head. So far 15 patients, (6 male and 9 females) with a median age of 55 years (range 42–62) have been evaluated in group 1 and 14 (9 male and 5 females) with a median age of 55 years (range 45–70) in group 2. The penetration of the femoral heads has so far been measured postoperatively (all hips supine), after 3 month (17 hips supine and standing) and after 6 month (11 hips supine and standing) using radiostereometry. Results: The median proximal and three-dimensional (3-D) penetration (total wear) 0–6 month (supine position) was almost equal in the two groups. Group 1 had a proximal penetration of 0.08 mm (range 0.00–0.17) and a total penetration of 0.11 mm (range 0.06–0.14). The corresponding values for group 2 were 0,10 mm (0.05–0.21) for proximal penetration and 0.13 mm (0.10–0.16) for total penetration. Between 3 and 6 month the penetration (median values) was 0.04 mm/0.10 mm (proximal/3-D) for group 1 and 0.07 mm/0.12 mm for group 2. With the patients standing we found a proximally migration of the socket (0–6 month) in group 1 of 0,08 mm (−0.07 – 0.21) and 0.12 mm (0.1–0.13) in group 2. Discussion: Use of a highly cross-linked polyethylene in the socket did not influence the early penetration rate after THR. Early creep of the material is possible explanation. 1-year follow-up on approximately 50% of the patients will be presented at the meeting

Aims

In the 1990s, a bioactive bone cement (BABC) containing apatite-wollastonite glass-ceramic (AW-GC) powder and bisphenol-a-glycidyl methacrylate resin was developed at our hospital. In 1996, we used BABC to fix the acetabular component in primary total hip arthroplasty (THA) in 20 patients as part of a clinical trial. The purpose of this study was to investigate the long-term results of primary THA using BABC.