The creep and wear behaviour of highly cross-linked polyethylene and standard polyethylene liners were examined in a prospective, double-blind randomised, controlled trial using radiostereometric analysis.

We randomised 54 patients to receive hip replacements with either highly cross-linked polyethylene or standard liners and determined the three-dimensional penetration of the liners over three years.

After three years the mean total penetration was 0.35 mm (SD 0.14) for the highly cross-linked polyethylene group and 0.45 mm (SD 0.19) for the standard group. The difference was statistically significant (p = 0.0184). From the pattern of penetration it was possible to discriminate creep from wear. Most (95%) of the creep occurred within six months of implantation and nearly all within the first year. There was no difference in the mean degree of creep between the two types of polyethylene (highly cross-linked polyethylene 0.26 mm, SD 0.17; standard 0.27 mm, SD 0.2; p = 0.83). There was, however, a significant difference (p = 0.012) in the mean wear rate (highly cross-linked polyethylene 0.03 mm/yr, SD 0.06; standard 0.07 mm/yr, SD 0.05). Creep and wear occurred in significantly different directions (p = 0.01); creep was predominantly proximal whereas wear was anterior, proximal and medial.

We conclude that penetration in the first six months is creep-dominated, but after one year virtually all penetration is due to wear. Highly cross-linked polyethylene has a 60% lower rate of wear than standard polyethylene and therefore will probably perform better in the long term.

Few independent studies have reported the outcome of resurfacing arthroplasty of the hip. The aim of this study was to report the five-year clinical outcome and seven-year survival of an independent series.

A total of 610 Birmingham Hip Resurfacing arthroplasties were performed in 532 patients with a mean age of 51.8 years (16.5 to 81.6). They were followed for between two and eight years; 107 patients (120 hips) had been followed up for more than five years. Two patients were lost to follow-up. At a minimum of five years’ follow-up, 79 of 85 hips (93%) had an excellent or good outcome according to the Harris hip score. The mean Oxford hip score was 16.1 points (sd 7.7) and the mean University of California Los Angeles activity score was 6.6 points (sd 1.9). There were no patients with definite radiological evidence of loosening or of narrowing of the femoral neck exceeding 10% of its width. There were 23 revisions (3.8%), giving an overall survival of 95% (95% confidence interval 85.3 to 99.2) at seven years. Fractured neck of femur in 12 hips was the most common indication for revision, followed by aseptic loosening in four. In three hips (three patients) (0.5%), failure was possibly related to metal debris.

Considering that these patients are young and active these results are good, and support the use of resurfacing. Further study is needed to address the early failures, particularly those related to fracture and metal debris.

Significant proximal femoral bone deficiency in revision hip surgery poses a considerable challenge, especially as revision hip surgery is increasing in prevalence. Many femoral prosthetic devices, which compensate for this bone loss, are available to surgeons but ideally one wants to restore viable proximal bone stock. The Oxford Universal Hip (OUH) has been designed and modified with these challenges in mind. This is atrimodular, non-locking device that allows for some rotation and subsidence in the cement. Load transfer occurs at the proximal wedge, thus avoiding proximal stress shielding. The OUH has been used extensively in both primary and revision hip surgery and is particularly useful when used in conjunction with proximal impaction bone grafting. The main aim of this study was to determine the clinical outcome of the patients. The viability and survivorship of the impacted bone graft was assessed in order to give some indication of adequate perfusion of the incorporated bone grafting.

Between 1999 and 2002 the OUH, in combination with proximal impaction bone grafting, was implanted in 72 hip revisions in 69 patients. All patients were clinically evaluated using the Oxford Hip score. Histological samples of impacted bone grafting were analysed by a pathologist 2 years after implantation to assess viability and perfusion of the impacted bone graft.

The Oxford Hip Score improved from a pre-operative to a post-operative score of 45 (26–58) to 24.3 (12–43) respectively (p< 0.001). The mean follow up time was 32.7 months and in that time there were no re-revisions for aseptic loosening. Histology demonstrated viable bone stock in the proximal femur where bone grafting had been impacted 2 years previously.

The OUH is a versatile hip prosthesis for use in revision hip arthroplasty and is especially well suited to proximal impaction bone grafting where it is possible to restore viable bone stock

Bone stock loss secondary to debris and mechanic alin-stability presents a challenge in revision hip arthroplasty. The aim of our study is to evaluate the clinical outcome of revision hip arthroplasty using the Oxford hip prosthesis combined with impaction allografting.

Between 1999 and 2002, we revised 72 hips in 69 patients using this technique (mean age 65years). Indications were aseptic loosening (56), infection (8), peri-prosthetic fracture (7) and a broken stem (1). The mean time to revision was 8.5 years (1–21years). Patients were assessed clinically and with the Oxford Hip Score (OHS) pre- and post-operatively. Fifty-seven patients also had acetabular revision. Four patients required femoral osteotomy to remove the old prosthesis. We used a mean of 1.8 (1–4) femoral heads per operation.

Patients were mobilised partially weight bearing (8weeks) followed by a gradual return to full loading. Complications included peri-operative femoral fracture (6), infection (6), dislocation (10), DVT (1)and PE (2). The average blood transfusion was 1.8 units (0–9). The OHS improved from 45 (26–58) pre-operatively to 24.3 post-operatively (12–43). No hip has been re-revised for aseptic loosening at a mean follow-up of 32.7months (16–51).

The Oxford hip is a trimodular prosthesis with a polished tapered metaphyseal section that is free to slide and rotate on the stem. The stem is first inserted uncemented into the diaphysis. Bone graft is impacted proximally, with mesh if necessary, and then the proximal wedge is cemented in. The wedge allows for some subsidence in the cement and creates optimal radial force transmission, which is essential for bone-remodelling stimulation and preventing proximal stress shielding. Although this is a short-term experience, we believe that the use of the tri-modular Oxford stem combined with minimal proximal impaction allografting is a reliable method of dealing with difficult revision femoral surgery. The results were comparable with a primary arthroplasty in terms of pain relief and functional results.

Oxford Unicompartmental knee arthroplasty (UKA) is now performed using a minimally invasive surgical (MIS) technique. Although early results are encouraging, the studies assessing outcome could be criticised for the restricted number of patients and limited follow-up. Aim of this study was to assess clinical outcome and prosthetic survival rate inpatients with minimally invasive Oxford medial UKA.

This prospective study assessed 500 consecutive patients, who underwent cemented Oxford UKA for medial OA using MIS technique. Patients were assessed using objective and functional Knee Society Score (KSS).

This study has confirmed preliminary findings that Oxford UKA using a minimally invasive approach is safe, reliable and effective.

The Charnley Elite femoral component was first introduced in 1992 as a new design variant of the original Charnley femoral component (De Puy, Leeds, UK) with modified neck and stem geometry. The original component had undergone few changes in nearly forty years and has excellent long-term results. Early migration of the new stem design was determined by Roentgen Stereophotogrammetric Analysis (RSA)1. Rapid early migration of a component relative to the bone, measured by RSA, is predictive of subsequent aseptic loosening for a number of femoral stems. As there was rapid early migration and rotation of the Charnley Elite stem, we predicted that the long-term results would be poor. An outcome assessment is indicated as stems of this type are still being implanted.

One hundred Charnley Elite stems, implanted in our centre between 1994 and 1997 were included in a prospective, cross-sectional follow-up study. Outcome measures include validated clinical scores (Charnley hip score, Harris hip score and Oxford hip score) and radiological scores (Gruen classification) as well as revision rates over the past 10 years.

The clinical follow-up supports the RSA predictions of early failure of the Charnley Elite femoral stem.

Aim: To investigate the functional and radiological outcome of shelf acetabuloplasty in adults with significantly symptomatic acetabular dysplasia, with a minimum of a 5 year follow-up.

Material and Methods: 77 consecutive shelf procedures (68 patients) with an average follow-up of 10.9 years (range: 6–14) were reviewed. The Oxford hip score (OHS) was used for clinical assessment. Centre-edge angle (CEA) and acetabular angle (AA) were measured as indicators of joint containment. The severity of osteoarthiritis was based primarily on the extent of joint space narrowing. Survivorship analyses using conversion to THR as an endpoint were performed. Logrank tests were used to compare the survivorship of the shelf procedure against the variables of age, preoperative osteoarthiritis, pre and postoperative AA, CEA angles.

Results: The average age at time of surgery was 33 years (range: 17–60). At the time of the last follow-up, the mean OHS was 34.6 (maximum score: 48). Mean postoperative CEA was 55 (Pre-operatively: 13 degrees) while mean postoperative AA was 31 (Pre-operatively: 48 degrees). Thirty percent of hips needed THR at an average duration of 7.3 years. The survival in the 45 patients with only slight or no joint space narrowing was 97% (CI, 93%–100%) at 5 years and 80% (CI, 56%–100%) at 10 years. This was significantly higher (p= 0.0007) than the survival in the 32 patients with moderate or severe osteoarthiritis, which was 72% (CI, 55%–89%) at 5 years and 29% (CI, 13%–45%) at 10 years. There was no significant relationship between survival and age, pre and postoperative AA, CEA angles (p> 0.05).

Conclusion: Shelf-acetabuloplasty offers symptomatic relief to adults with acetabular dysplasia but overall deteriorates with time. About 50% of the patients do not need THR for over 10 years. Best results with shelf-acetabuloplasty were achieved in patients with slight or no joint narrowing.

Introduction: The design philosophy of polished tapered THR stems, such as the Exeter, intend for them to migrate distally within the cement mantle. In addition it is likely that micromotion occurs as a result of functional activity. The pattern of induced stresses will be a function of stem geometry & surface finish, as well as applied loading. Aim: To investigate the stresses induced in the cement mantle of a polished tapered THR stem during functional activity.

Method: Using Roentgen Stereophotogrammetric Analysis (RSA) dynamically induced micro-motion (DIMM) was measured in 21 patients implanted with Exeter stems. DIMM was measured as the difference in stem position in going from double to single leg stance on the operated limb. All subjects were measured 3 months post-operatively. A finite element (FE) model of the femur, including all muscles was used to investigate the stress distribution within the cement; contact was modelled with sliding elements allowing separation. The model was validated by comparison to the DIMM measurements.

Results: The Exeter stem demonstrated significant DIMM(p < 0.017), the average motions are given in the table below. The FE model, with sliding contacts was able to predict similar distal migration of the head. The peak minimum principal stress in the mantle was approx 33MPa and occurred in the proximal medial region. Movements occurred at the stem/cement interface.

Discussion and Conclusion: It is possible to measure DIMM in the Exeter stem and combining this with FE modelling the mechanism of stress transfer between the stem and mantle can be investigated in a manner that can be validated.

Purpose This study aims to investigate blood flow in the femoral head during Metal-on-Metal Hip Resurfacing (MMHR) through the posterior approach by monitoring oxygen concentration during the operative procedure.

Methods Following division of fascia lata, a calibrated gas-measuring electrode was inserted into the femoral neck, aiming for the anterolateral quadrant of the head. Baseline oxygen concentration levels were detected after electrode insertion 2–3cm below the femoral head surface and all intra-operative measures were referenced against these. Oxygen levels were continuously monitored throughout the operation. Results of measurements from ten patients are presented.

Results Oxygen concentration was reduced during the surgical approach and average oxygen concentration following dislocation and circumferential capsulotomy dropped to 43% of baseline (Std.dev +/−37%), this was a highly significant reduction (p< 0.005). Insertion of implants resulted in a further significant drop in oxygen concentration (p< 0.02) to 16% of baseline (Std. dev +/−27%). Oxygen concentration rose slightly after relocation of the resurfaced joint and reconstruction of posterior soft tissues, reaching 22% (Std.dev +/−31%) of initial baseline oxygen levels. Considerable variation between subjects was observed. Three subjects had no remaining oxygen concentration at the end of surgery.

Conclusion Intra-operative measurement of oxygen concentration in blood perfusing the femoral head is feasible. During MMHR there is a dramatic decrease in femoral oxygenation during surgical approach and implant fixation. This may increase the risk of avascular necrosis and subsequent femoral neck fracture. Future experiments will determine if less invasive procedures or a different approach can protect the blood supply to femoral neck and head.

Introduction Polyethylene wear debris is an important cause of failure in cemented total hip arthroplasty. As a result of the biological response to debris at the bone-cement interface, osteolysis and subsequent failure occurs in both femoral and acetabular components. Most acetabular components and liners are made of ultra high molecular weight polyethylene (UHMWPE). Cross-linking UHMWPE has been shown to significantly reduce abrasive wear in hip simulator studies. The wear rates measured in vitro do not always correlate with the wear rates measured in clinical studies[1]. Some new polyethylenes have shown catastrophic wear in clinical studies despite encouraging hip simulator study results[2]. The aim of this study was to compare the wear of standard UHMWPE to that of cross-linked UHMWPE (Longevity, Zimmer, Warsaw, USA)

Patients and Methods This was a prospective, double blind, randomised control trial. 50 subjects were recruited, all of whom received the cemented CPT stem and uncemented Trilogy liner (Zimmer, UK). Subjects were randomised to receive either a standard Trilogy liner or a Longevity liner at the time of operation. Both liners are identical in appearance. All liners were of a neutral configuration. RSA was used to measure linear wear. This was calculated by measuring the distance between the centre of the femoral head and the centre of the acetabular liner. The preliminary results of the study are presented.

Results Both groups underwent significant wear over two years. The two year linear wear of the cross-linked UHMWPE was 0.3mm (+/− 0.06mm, p< 0.001). The two year linear wear of the standard UHMWPE was 0.39mm (+/− 0.04mm, p< 0.001). No significant difference existed between the two groups (p=0.24). Both cohorts had around 0.15 to 0.2 mm of measured wear per year. Cross-linked UHMWPE therefore underwent less wear than standard UHMWPE at two years, however this difference was not statistically significant.

Discussion This study suggests that Longevity UHMWPE has similar wear properties to standard UHMWPE in the first two years following implantation. This does not correlate with in vitro hip simulator studies of Longevity polyethylene, which show a significantly lower wear rate than standard UHMWPE. It suggests that hip simulator studies may be of little value in predicting in vivo wear rates and that all new types of polyethylene should be evaluated clinically and radiologically prior to general release. Whether both cohorts continue to wear at similar rates will only be revealed through continued observation.

Introduction Metal-on-Metal Hip Resurfacing (MMHR) has been established as a successful alternative to Total Hip Replacement (THR). However, several series report a 2 % incidence of early femoral neck fractures. Avascular necrosis (AVN) was considered to be responsible for the majority of observed fractures, raising concerns about the femoral head blood supply during MMHR. This study aims to further understand the mechanisms of femoral blood flow restriction by monitoring gas levels (O2) during the operative procedure.

Methods Patients undergoing MMHR using the posterior approach were evaluated. Following division of fascia lata, a guide wire was introduced up the femoral neck, aiming for the anterosuperior quadrant of the head. It was then removed. A calibrated gas-measuring electrode was inserted in the created bone channel. X-ray confirmation was obtained to ensure that the active measurement area of the electrode was 2–3cm below the femoral surface. O2 and N2O levels were then continuously monitored throughout the operation.

Results A preliminary analysis of four patients is presented: Stable N2O- measurements throughout the procedure confirmed valid electrode measurements. Baseline oxygen concentration levels of 40%– 60% were detected before division of short rotators. After hip dislocation oxygen concentration dropped in all patients to levels ranging between 0% and 5%. Oxygen concentration was found to remain depressed at these levels throughout the entire operation in three patients. Recovery of O2 concentration to baseline levels was observed in one patient 15 minutes after dislocation.

Discussion In three patients the extended posterior approach and joint dislocation had a dramatic effect on the perfusion in the femoral head. These patients have a high risk for development of AVN and potential femoral neck fracture. Whilst the results require further verification, subsequent experiments will determine if less invasive procedures or specific positioning of the limb can protect the femoral blood supply.

Introduction: The Charnley Elite femoral component was first introduced in 1992 as a new design variant of the original Charnley femoral component (De Puy, Leeds, UK) with modified neck and stem geometry. The original component had undergone few changes in nearly forty years and has excellent long-term results.

Early migration of the new stem design was determined by Roentgen Stereophotogrammetric Analysis (RSA). Rapid early migration of a component relative to the bone, measured by RSA, is predictive of subsequent aseptic loosening for a number of femoral stems. As there was rapid early migration and rotation of the Charnley Elite stem, we predicted that the long-term results would be poor. An outcome assessment is required as stems of this type are still being implanted.

Materials and method: One hundred Charnley Elite stems, implanted in our centre between 1994 and 1997 were included in a prospective, cross-sectional follow-up study. Outcome measures include validated clinical scores (Charnley hip score, Harris hip score and Oxford hip score) and radiological scores (Gruen classification) as well as revision rates over the past 10 years.

Results: The preliminary analysis results are given. The mean time to follow-up was 8.28 years. 20 patients have died due to causes unrelated to their operations. 10 patients had stem revisions: 9 for aseptic loosening and 1 for a peri-prosthetic fracture. This indicates a significant 10% failure rate of the prosthesis in less than 10 years.

Preliminary clinical scores in the patients who had not undergone any subsequent surgery were adequate (Oxford Hip Score mean average of 23.9).

Thirteen percent of radiographs analysed had evidence of loosening, giving an overall loosening rate of 14% at 8 years.

Discussion and conclusion: The clinical follow-up supports the RSA predictions of early failure of the Charnley Elite femoral stem.

Background: Hip dysplasia is a complex developmental process. Untreated acetabular dysplasia is the most common cause of secondary hip osteoarthiritis. With increased interest in redirectional pelvic osteotomies, the role of the shelf procedure needs to be re-defined.

Aim of the study: to investigate the effectiveness of the shelf procedure in adults with symptomatic acetabular dysplasia by assessing the functional and radiological outcome at a minimum of five years follow-up.

Material and Methods: Seventy-six consecutive adults with symptomatic acetabular dysplasia treated with acetabular shelf augmentation, have been followed up for an average period of 11 years (range: 6–14). The mean age was thirty-three years (range: 17–60 years). The Oxford hip score (OHS) was used for clinical assessment. Centre-edge angle (CEA) and acetabular angle (AA) were measured to determine femoral head coverage. Osteoarthiritis severity was based primarily on the width of the joint space using the De Mourgues classification. Survivorship analyses using conversion to THR as an endpoint were performed. logrank test was used to compare the outcome of the shelf against the variables of age, preoperative osteoarthiritis, preoperative and postoperative AA, CEA angles.

Results: The shelf procedure improved the mean preoperative CEA from 11° (range: 20° to 17°) to 50° postoperatively (range: 30° to 70°) and the mean preoperative AA from 52° (range: 46° to 64°) to 32° postoperatively (range: 18° to 57°). The Mean OHS was 34.6 (hip score maximum: 48). Thirty percent of hips needed THR at an average duration of 7.3 years. Survival analysis using conversion to THR as an endpoint was 86% (CI, 76%–95%) at five years and 46% (CI, 27%–65%) at ten years. The survival in the 44 patients with only slight or no joint space narrowing was 97% (CI, 93%–100%) at 5 years and 75% (CI, 51%–100%) at 10 years. This was significantly higher (p= 0.0007) than the survival in the 32 patients with moderate or severe osteoarthiritis, which was 76% (CI, 55%–89%) at 5 years and 22% (CI, 5%–38%) at 10 years. There was no significant relationship between survival and age (p= 0.37), pre and postoperative centre-edge angle (p= 0.39), or acetabular angle (p= 0.85).

Conclusion: Shelf acetabuloplasty is a reliable, safe procedure offering medium-term symptomatic relief for adults with acetabular dysplasia. The best results were achieved in patients with slight or no joint space narrowing.

We inserted an electrode up the femoral neck into the femoral head of ten patients undergoing a metal-on-metal hip resurfacing arthroplasty through a posterior surgical approach and measured the oxygen concentration during the operation. In every patient the blood flow was compromised during surgery, but the extent varied. In three patients, the oxygen concentration was zero at the end of the procedure. The surgical approach caused a mean 60% drop (p < 0.005) in oxygen concentration while component insertion led to a further 20% drop (p < 0.04). The oxygen concentration did not improve significantly on wound closure. This study demonstrates that during hip resurfacing arthroplasty, patients experience some compromise to their femoral head blood supply and some have complete disruption.

We followed up 76 consecutive hips with symptomatic acetabular dysplasia treated by acetabular shelf augmentation for a mean period of 11 years. Survival analysis using conversion to hip replacement as an end-point was 86% at five years and 46% at ten years. Forty-four hips with slight or no narrowing of the joint space pre-operatively had a survival of 97% at five and 75% at ten years. This was significantly higher (p = 0.0007) than that of the 32 hips with moderate or severe narrowing of the joint-space, which was 76% at five and 22% at ten years. There was no significant relationship between survival and age (p = 0.37) or the pre- and post-operative centre-edge (p = 0.39) and acetabular angles (p = 0.85).

Shelf acetabuloplasty is a reliable, safe procedure offering medium-term symptomatic relief for adults with acetabular dysplasia. The best results were achieved in patients with mild and moderate dysplasia of the hip with little arthritis.

Introduction: The Birmingham Hip Resurfacing (BHR) is a metal on metal prosthesis with no published independent clinical studies. It is increasingly used as an alternative to stemmed prostheses in younger patients.

This study presents the 2 year migration results of the BHR femoral component using Roentgen Stereophoto-grammteric Analysis (RSA).

Methods: 26 hips in 24 subjects underwent a BHR, through the postero-lateral approach using CMW3G cement. RSA marker balls were placed in the cortical bone of the femur intra-operatively. The femoral component migration was measured at intervals of 3, 6, 12 and 24 months postoperatively using the Oxford RSA system. The implants were un-modified, geometric algorithms were used to identify the femoral component.

Results: The BHR femoral component showed no significant displacement from its immediate post-operative position. All components of migration showed no significant displacement in any direction, at 1 or 2 years.

Conclusion: The BHR femoral component does not migrate significantly within the first two post-operative years. Its’ migration compares favourably to other designs of femoral component. The BHR is therefore likely to remain stable in the future, as the majority of implant migration occurs within the first two years.

Polished, tapered stems are now widely used for cemented total hip replacement and many such designs have been introduced. However, a change in stem geometry may have a profound influence on stability. Stems with a wide, rectangular proximal section may be more stable than those which are narrower proximally. We examined the influence of proximal geometry on stability by comparing the two-year migration of the Exeter stem with a more recent design, the CPS-Plus, which has a wider shoulder and a more rectangular cross-section. The hypothesis was that these design features would increase rotational stability.

Both stems subsided approximately 1 mm relative to the femur during the first two years after implantation. The Exeter stem was found to rotate into valgus (mean 0.2°, sd 0.42°) and internally rotate (mean 1.28°, sd 0.99°). The CPS-Plus showed no significant valgus rotation (mean 0.2°, sd 0.42°) or internal rotation (mean −0.03°, sd 0.75°). A wider, more rectangular cross-section improves rotational stability and may have a better long-term outcome.

We describe a technique of ‘cross-hip distraction’ to reduce a dislocated hip with subsequent reconstruction of the joint for septic arthritis with extensive femoral osteomyelitis. A 27-year-old woman presented with a dislocated, collapsed femoral head and chronic osteomyelitis of the femur. Examination revealed a leg-length discrepancy of 7 cm and an irritable hip. A staged technique was used with primary clearance of osteomyelitis and secondary reconstruction of the hip. A cross-hip monolateral external fixator was used to establish normal anatomy followed by an arthroplasty. A good functional outcome was achieved. The use of cross-hip distraction avoids soft-tissue and nerve damage and achieved improved abductor function before arthroplasty.

We present the histological findings of bone retrieved from beneath the femoral components of failed metal-on-metal hip resurfacing arthroplasties. Of a total of 377 patients who underwent resurfacing arthroplasty, 13 required revision; for fracture of the femoral neck in eight, loosening of a component in three and for other reasons in two. None of these cases had shown histological evidence of osteonecrosis in the femoral bone at the time of the initial implantation.

Bone from the remnant of the femoral head showed changes of osteonecrosis in all but one case at revision. In two cases of fracture which occurred within a week of implantation, the changes were compatible with early necrosis of the edge of the fracture. In the remaining six fractures, there were changes of established osteonecrosis. In all but one of the non-fracture cases, patchy osteonecrosis was seen.

We conclude that histological evidence of osteonecrosis is a common finding in failed resurfaced hips. Given that osteonecrosis is extensive in resurfaced femoral heads which fail by fracture, it is likely to play a role in the causation of these fractures.

Aim: To investigate the functional and radiological outcome of shelf acetabuloplasty in adults with significantly symptomatic acetabular dysplasia, with a minimum of a 5 year follow-up.

Material and Methods: 77 consecutive shelf procedures (68 patients) with an average follow-up of 10.9 years (range: 6–17) were reviewed. The Oxford hip score (OHS) was used for clinical assessment. Centre-edge angle (CEA) and acetabular angle (AA) were measured as indicators of joint containment. The severity of osteoarthiritis was based primarily on the extent of joint space narrowing. Survivorship analyses using conversion to THR as an endpoint were performed. Logrank tests were used to compare the survivorship of the shelf procedure against the variables of age, preoperative osteoarthiritis, pre and postoperative AA, CEA angles.

Results: The average age at time of surgery was 33 years (range: 17–60). At the time of the last follow-up, the mean OHS was 34.6 (maximum score: 48). Mean postoperative CEA was 55 (Pre-operatively: 13 degrees) while mean postoperative AA was 31 (Pre-operatively: 48 degrees). Thirty percent of hips needed THR at an average duration of 7.3 years. The survival in the 45 patients with only slight or no joint space narrowing was 97% (CI, 93%-100%) at 5 years and 75% (CI, 51%-100%) at 10 years. This was significantly higher (p≤= 0.0007) than the survival in the 32 patients with moderate or severe osteoarthiritis, which was 76% (CI, 55%-89%) at 5 years and 22% (CI, 5%-38%) at 10 years. There was no significant relationship between survival and age, pre and postoperative AA, CEA angles (p> 0.05).

Conclusion: Shelf-acetabuloplasty offers symptomatic relief to adults with acetabular dysplasia but overall deteriorates with time. About 50% of the patients do not need THR for over 10 years. Best results with shelf-acetabuloplasty were achieved in patients with slight or no joint narrowing.