In this prospective study a total of 80 consecutive Chinese patients with Crowe type I or II developmental dysplasia of the hip were randomly assigned for hip resurfacing arthroplasty (HRA) or total hip replacement (THR).

Three patients assigned to HRA were converted to THR, and three HRA patients and two THR patients were lost to follow-up. This left a total of 34 patients (37 hips) who underwent HRA and 38 (39 hips) who underwent THR. The mean follow-up was 59.4 months (52 to 70) in the HRA group and 60.6 months (50 to 72) in the THR group. There was no failure of the prosthesis in either group. Flexion of the hip was significantly better after HRA, but there was no difference in the mean post-operative Harris hip scores between the groups. The mean size of the acetabular component in the HRA group was significantly larger than in the THR group (49.5 mm vs 46.1 mm, p = 0.001). There was no difference in the mean abduction angle of the acetabular component between the two groups.

Although the patients in this series had risk factors for failure after HRA, such as low body weight, small femoral heads and dysplasia, the clinical results of resurfacing in those with Crowe type I or II hip dysplasia were satisfactory. Patients in the HRA group had a better range of movement, although neck-cup impingement was observed. However, more acetabular bone was sacrificed in HRA patients, and it is unclear whether this will have an adverse effect in the long term.

Reports of improved functional outcome of Metal on Metal Hip Resurfacing Arthroplasty (mHRA) to Total Hip Replacement needs to be balanced with concerns of metal ion release. By removing cobalt-chrome, cHRA reduces these risks. To the author's knowledge, there is no data available on functional outcomes of cHRA, therefore the aim of the study was to compare the function between cHRA patients and mHRA patients. 24 patients received a unilateral cHRA (H1, Embody) and was compared to 24 age and gender matched patients with a unilateral mHRA (BHR, Smith and Nephew). All patients completed the Oxford Hip Score (OHS)[T2] and underwent gait analysis on an instrumented treadmill before and at a mean of 74wks (+/− 10) for mHRA and 53wks (+/− 2) for cHRA post op. Walking trials started at 4km/h and increased in 0.5km/h increments until a top walking speed (TWS) was achieved. Vertical ground reaction forces (GRF) were recorded along with the symmetry index (SI). Spatiotemporal measures of gait were also recorded. Vertical GRF were captured for the entire normalised stance phase using statistical parametric mapping (SPM; CI = 95%). The gain in OHS was similar: H1 (25-46), BHR(27-47). TWS increased by 19% with H1 (6.02 – 8.0km/hr), and 20% with BHR (6.02 – 7.37km/hr). SPM of the entire gait cycle illustrated the restoration of symmetry in both groups with no difference in GRF across the stance phase between groups at 5km/hr pre-op and post-op. At faster speeds (6.5km/hr), H1 patients had a mid-support GRF slightly closer to normal compared to BHR. Both groups increased step length similar from pre to post op (H1:0.76 – 0.85cm, BHR:0.77-0.86cm). In this study, subjective and objective functional outcome measures suggest that short term functional outcomes of ceramic resurfacing is not inferior to metal resurfacing

Purpose. This study was performed to evaluate clinical and radiographic outcomes of Hip Resurfacing Arthroplasty for treatment of haemophilic hip arthropathy. Material & Method. Between 2002 and 2013, 17 cases of hip resurfacing arthroplasties were performed in 16 haemophilic patients (13 cases of haemophilia A, 2 cases of haemophilia B, 2 cases of von Willebrand disease). The average age of the patients was 32.5(range: 18∼52) years. The average follow up period from the operation was 6.3 (range: 2∼13) years. In this study, the subjects that completed follow-up were composed of 5 cases composed of patients who were treated with Conserve plus. ®. hip resurfacing system, 5 cases composed of patients who were treated with Durom. ®. hip resurfacing system, 4 cases who were treated with ASR. ®. hip resurfacing system, and 3 cases who were treated with Birmingham. ®. hip resurfacing system. The Modified Harris hip score, the range of motion of the hip joint, perioperative coagulation factor requirements and complications associated with bleeding were evaluated as part of the clinical assessment. For the radiographic assessment, fixation of component, presence of femoral neck fracture, osteolysis, loosening and other complications were evaluated. Results. The modified Harris hip score improved from 65.4(47–80) points before surgery to 97.8(90–100) points at the last follow-up. The average further flexion improved from 103° (70–135) to 110°(80–130) after surgery. The average abduction improved from 22.4° (0–45) to 41.3° (20–50) after surgery. All the patients showed a significant reduction in pain. The mean requirement of factor VIII reduced from 2470 units per month before surgery to 1125 units per month at the time of the last follow-up. However, in the case of high-titer inhibitor to factor VIII, haemophilia B, von Willebrand disease, the average monthly factor requirement was not changed due to bleeding episode of other joints. There was two cases of re-bleeding. There were no femoral neck fracture, no osteolysis, and no implant loosening in last follow up. Conclusion. Hip resurfacing arthroplasty for haemophilic hip arthropathy in patients with mild deformity or relatively preserved range of the hip joint motion can bring reliable pain relief, functional improvement, and reduction of factor requirement for over two years follow-up study. However, bleeding-associated complications are a cause for concern, especially for patients with antibodies against coagulation factors

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

Humeral resurfacing arthroplasty has been advocated as an alternative to stemmed humeral component designs given its ability to preserve proximal bone stock. Further, these implants have become more attractive given the possibility of stem-related complications including humeral fracture, stress shielding, and osteolysis; complications that may necessitate fixation, revision to long stem components, or reverse total shoulder arthroplasty. As more total shoulder arthroplasties are performed in younger patient populations, the likelihood of increased revision procedures is inevitable. Maintaining proximal bone stock in these cases with use of a resurfacing arthroplasty not only facilitates explant during revision arthroplasty, but preservation of proximal metaphyseal bone facilitates reimplantation of components. Clinical results of these resurfacing components have demonstrated favorable results similar to stemmed designs. Unfortunately, resurfacing arthroplasty may not be as ideal as was hoped with regard to recreating native humeral anatomy. Further, resurfacing arthroplasty may increase the risk of peri-prosthetic humeral fracture, and lack of a formal humeral head cut makes glenoid exposure more difficult, which may be associated with a higher degree of neurovascular injury. Stemless humeral components are designed for strong metaphyseal fixation and avoid the difficulty with glenoid exposure seen in resurfacing designs, as these components require a formal humeral head cut. Early clinical outcomes of a single stemless design demonstrated significant improvements in clinical outcome scores, without evidence of component migration, subsidence or loosening. The only mid-term clinical results of stemless design implants are seen with the Arthrex Eclipse system (Arthrex, Naples, FL). In a prospective study involving 78 patients at 5-year follow-up, significant improvements were observed in clinical outcome scores. While there was evidence of proximal stress shielding in an older population, this did not influence shoulder function. The overall revision rate was 9% at 5 years, with no component necessitating revision as a result of humeral component loosening. Resurfacing arthroplasty and stemless humeral components in total shoulder arthroplasty remain attractive options to preserve proximal metaphyseal bone stock, avoiding stem-related complications. Early and mid-term clinical outcomes are comparable to stemmed designs and demonstrate no evidence of humeral component loosening

Aim: The aim of this study was to assess the role of Hip Arthroscopy in the patient with a symptomatic Resurfacing arthroplasty of the hip. Patients and Methods: Twelve consecutive patients who presented to our clinic with a painful resurfacing and indeterminate or normal investigations underwent an arthroscopy of their resurfacing were prospectively enrolled into the study following appropriate consent. The pre-operative investigations included haematological indices and acute phase reactants to rule out infection along with plain radiographs and an isotope bone scan. Results: (table deleted). Conclusions: Assessment of a symptomatic resurfacing is usually difficult and becomes more challenging in the background of normal or indeterminate investigations. However, in this situation, we found that in experienced hands, hip arthroscopy can be utilised as an effective tool for aiding diagnosis and offering therapeutic interventions in these patients

Introduction: The suitability of third generation metal-on-metal hip resurfacing for patients with a primary diagnosis of osteonecrosis (ON) has been debated. The preservation of femoral head bone stock for femoral prosthetic support is essential for long term stability of the implant. We hypothesized that the Kaplan-Meier survival estimates for resurfacing patients with a primary diagnosis of ON would be significantly lower than the survival estimates for resurfacing patients with a primary diagnosis of osteoarthritis (OA). Methods: One thousand one hundred and forty-eight patients were implanted with a modern hip resurfacing system as part of a United States multi-center investigational device exemption (IDE) study. Of these, 116 subjects had a preoperative diagnosis of ON. A multivariate analysis of variance was performed to identify risk factors for component revision for any reason. Results: A diagnosis other than OA was found to be one significant risk factor for revision. However, the survival estimates were not significantly different (95.9% and 95.8% at 24 months for OA and ON, respectively, p=0.46) when comparing the OA group to the ON group. Comparing only the Ficat stage III and IV to the OA population also did not show a significant difference in implant survival (95.9% OA and 96.1% ON III/IV at 24 months, p=0.57). Discussion: Resurfacing arthroplasty for patients with ON appears to be a reasonable alternative using judgments of implant size, patient gender, and size of proximal femoral deficiency. Further characterization will be needed to identify those specific patients with ON for whom resurfacing arthroplasty is not appropriate. For most patients, however, it appears to be a safe and reasonable option

The Birmingham reSurfacing Arthroplasty (BSA) is a metal on metal prosthesis with no published independent clinical studies. Despite this, it is increasing in popularity, especially as an alternative to stemmed prostheses in younger patients. This study presents the 1year migration results of the BSA femoral component using Roentgen Stereophotogrammteric Analysis (RSA). Twenty six subjects underwent a BSA, through the postero-lateral approach using CMW3G cement, with RSA marker balls placed intra-operatively. The femoral component migration was measured at intervals of 3, 6 and 12 months using the Oxford RSA system. Geometric algorhythms were used to identify the femoral component. The data was examined for distribution prior to analysis. All statistical analysis was performed using the t-test. The data was normally distributed. The 1 year migration results of the BSA femoral component are displayed below. All cemented implants migrate in vivo. The majority of cemented stemmed implant migration occurs within the first post-operative year. High rates of migration within the first post-operative year correlate with premature component failure in some instances. The BSA is a fundamentally different design to most cemented prostheses, despite this we know that very large migrations, those in excess of 2mm/year in any direction are generally regarded as poor indicators of long term outcome. These results suggest that the BSA femoral component is an inherently stable device as it does not migrate significantly within the first post-operative year. Only long-term independent clinical studies and continued RSA follow-up will enable a comprehensive evaluation of the device

Resurfacing arthroplasty of the hip is a relatively new procedure. This paper reports the technical and clinical problems one surgeon encountered in the first 50 consecutive resurfacing arthroplasties of the hip. The mean age of the 14 women and 32 men at the time of surgery was 44.8 years (20 to 65). Four patients underwent bilateral arthroplasty. Technical problems included failure of the acetabular component to seat fully in six hips and failure of the femoral component to seat fully in four. There was varus malalignment of the femoral component in three cases, retention of the alignment pin in one, and retention of a cable fragment in one. Surgical complications included one case of intra-operative femoral neck fracture, one transection of the psoas tendon during capsulotomy, and a femoral nerve palsy, which recovered after six months. Postoperative problems included superficial wound inflammation in five hips and one dislocation. There were radiological signs of impingement of the femoral neck on the acetabular rim in four cases and clinical symptoms of impingement in one. An undisplaced fracture of the femoral neck that occurred eight weeks after surgery was successfully managed conservatively by keeping the limb non-weight-bearing. Despite these problems, only one patient retains any noteworthy symptoms, apparently due to impingement of the femoral neck on the acetabular rim. Modest malalignment or seating failure appears to be of minimal clinical consequence. Patients typically mobilise rapidly and are able to return to a high level of physical activity. It is possible to avoid most technical problems by taking specific precautions

Introduction: Resurfacing arthroplasty of the hip joint has advantages of minimal bone resection, restoration of normal anatomy, and biomechanical circumstances. This study was undertaken to analyze the clinical and radiographic results of the resurfacing arthroplasty in patients with osteonecrosis of the femoral head (ONFH). Materials and Methods: Between September 1998 and September 2001, 40 hips in 39 patients with ONFH had a resurfacing arthroplasty with the Birmingham Hip Resurfacing (BHR) system. The mean age at the time of operation was 38.3 years. The average follow-up period was 36.8 months after operation. The patients were clinically evaluated by hip pain, Harris hip scores, range of motion, and radiographically evaluated for wear, change of cup position, loosening, and osteolysis. Results: The preoperative Harris hip score averaged 70.4 points and the degrees of flexion and internal rotation were 94° and 8°, respectively. The average Harris hip score at the last follow-up was 95.4 points. The degrees of flexion and internal rotation at last follow-up were 120°, and 20°, respectively. No patient complained of limb length discrepancy or pain in the hip or thigh. Rehabilitation programs and return to normal activities were earlier than that of conventional total hip arthroplasty (THA). There was no osteolysis, change of cup position, loosening, or detectable wear on the latest radiographic evaluation. Conclusions: Our experience with resurfacing arthroplasty for ONFH indicates that the overall results are superior than conventional THA with respect to pain relief, range of hip motion, earlier rehabilitation, and early return to preoperative activity. This procedure with BHR could be an alternative between joint preserving procedure and conventional THA in ONFH especially in younger patients

Purpose: A multicenter prospective evaluation of the Conserve Plus resurfacing implant (Wright Medical Technology) was undertaken to assess clinical and radiographic outcomes as well as ion levels. This study focuses on the serum, erythrocyte and urinary levels of cobalt and chromium in those patients undergoing hip resurfacing arthroplasty. Methods: A subset of patients enrolled in a multicenter trial to assess hip resurfacing arthroplasty had serum, erythrocyte and urinary cobalt and chromium levels measured. Levels were assessed preoperatively, then at three months, six months then yearly thereafter. Clinical outcome measurements were performed with WOMAC and Rand questionnaires. Results: Fifty-four out of 124 patients enrolled in the overall study had cobalt and chromium ion assessments performed. During the first year there was an increase in serum cobalt levels from 1.4 ug/l at 3 months to 2.4 ug/l at one year. Serum chromium levels increased from 1.4 ug/l at 3 months to 3.5 ug/l at one year. Erythrocyte cobalt levels increased from 0.8 ug/l at 3 months to 1.4 ug/l at one year. Erythrocyte chromium levels decreased from 1.5 ug/l at 3 months to 1.4 ug/l at one year. Urinary levels for cobalt increased from 12.7 ug/l at 3 months to 13.8 ug/l at one year. Urinary chromium levels rose from 4.0 ug/l at 3 months to 5.1 ug/l at one year. Conclusions: Increasing ion levels were seen during the first year post hip resurfacing arthroplasty. Clinical outcomes demonstrate predictable improvements in pain and function consistent with hip replacement surgery. Resurfacing arthroplasty is a viable option to total hip arthroplasty for younger active patients. The clinical significance of increased cobalt and chromium ions remains unknown. Funding: Commerical funding Funding Parties: Wright Medical Technology Inc

The early designs of hip resurfacing implants suffered high rates of early failure, making it impossible to obtain valuable mid-term radiostereophotogrammetric (RSA) results. The metal-on-metal Birmingham Hip Resurfacing arthroplasty has shown promising mid-term results and we present here the first mid-term RSA analysis of a hip resurfacing implant. The analysis was performed in 19 hips at five years post-operatively. The mean acetabular component translation and rotation, and femoral component translation were compared with the previous RSA measurements at two and six months, and one and two years. There was no statistical significance (t-test, p ≤ 0.05) between these consecutive movements, indicating the mid-term stability of the implant

Purpose of study: We report the results of a prospective case series of 10 patients who developed tumour-like masses following resurfacing arthroplasty. Method: Ten subjects were referred to the tumour service at the Nuffield Orthopaedic Centre with symptomatic masses around the hip, all had previously received a resurfacing arthroplasty. We report the clinical, radiographic and histologic features of these cases. Results: MRI and ultrasound scanning was preformed, which demonstrated masses with solid and cystic components. Biopsy was performed and subsequent histological examination revealed a profound plasma-cell lymphocytic response associated with metal wear debris. There were no infections in this series. Three subjects required revision surgery. Conclusion: Over 50,000 resurfacing arthroplasties have been implanted worldwide over the past ten years. Although the early clinical results are encouraging little is known about the long term consequences of large head metal on metal bearing surfaces. Despite this, these devices are being widely marketed and are often implanted in younger patients. Resurfacing arthroplasties are associated with high serum and urine metal ion concentrations, metal particles have also been shown to migrate along the lymphatic system. In addition, there is now evidence that high local metal ion concentrations can induce haempoietic cancers. This study suggests that resurfacing arthoplasty can also induce a local hypersensitivity reaction in response to metal wear debris. It therefore raises new concerns regarding the long-term safety of this procedure

Aim: We present the outcome of Birmingham Hip Resurfacing Arthroplasty performed by a single surgeon after at least five years follow up. Patients and Methods: One hundred hips in 84 patients were studied with a mean follow-up of 6.4 years (5–8.3 years), performed by a single surgeon. Three patients died of unrelated causes and 2 patients were lost to follow-up, hence the study group comprised of 79 patients with 95 hips. Birmingham resurfacing femoral and acetabular components were used in all patients. The clinical outcome was measured using Harris, Charnley, Oxford hip scores and quality of life using SF-36. Radiographs were systematically analysed for implant position, fixation, and loosening. Results: The mean age was 54 years (20–74years) and BMI of 28 (19–35). Primary osteoarthritis was seen in 69 hips. Six patients (6.1%) underwent revision of the femoral component (3 for peri-prosthetic fractures of the neck of femur, 2 for deep infection and 1 for collapse due to AVN). None of the patients had evidence of loosening around the acetabular component and femoral components in 28 patients. Type 1 pedestal sign was seen in 61 hips and Type 2 in 2 hips. The clinical scores were respectively, Harris 85 (25–100), Oxford 21.5 (12–52), mean Charnley score 4.8 for pain, 5.3 for movement and 4.3 for mobility; the mean SF-36 score were 44 (12–58) for the physical and 51.4 (19–71) for the mental component. With an end point of definite or probable aseptic loosening, the probability of survival at 5 years was 100% and 97.3% (95% CI = 2.9) for acetabular and femoral components respectively. Overall survival at 5years with removal or repeat revision of either component for any reason as the end point was 91% (95% CI: 82 to 97%). Conclusion: The results of this study support the continued use of Birmingham Hip Resurfacing Arthroplasty in young active individuals. As loosening can occur as a late phenomenon, a longer follow up is needed to determine longevity, durability of this prosthesis

Introduction. Hip Resurfacing Arthroplasty (HRA) has been performed in the United States for over 10 years and is an alternative to standard Total Hip Arthropastly (THA). It is appealing to younger patients with end stage osteoarthritis who seek to maintain active lifestyles. Benefits of HRA versus THR include a larger femoral ball size, potential to return to impact activities, decreased dislocation rates, and restoration of normal hip biomechanics. Patients ≤50 years old are a particularly challenging patient group to treat with THA because of their young age and high activity level, and as such, are well-suited for HRA. However, there are limited reports in the literature about clinical, radiographic and functional outcomes for this patient cohort. We present results of a clinical investigation at our institution for this patient cohort with minimum 5-year follow up, including long term survivorship and outcome scores. Methods. HRA, using the Birmingham Hip Resurfacing (BHR), was performed for 538 procedures between 2006–2009 by a single surgeon at a United States teaching hospital. After Institutional Review Board approval, medical and radiographic study records were retrospectively reviewed. Harris Hip Scores (HHS) were routinely collected. Patients who had not returned for follow-up examination were contacted by telephone for information pertaining to their status and implant, and a modified HHS was also administered. A Kaplan Meier survival curve was constructed to evaluate time to revision. Statistical analysis was performed (SAS version 9.3; SAS Institute, Cary, NC). Results. Of the 538 patients who underwent HRA from 2006–2009, 238 were aged ≤50 years (44%). Five-year follow up data was obtained from 209 of these patients (88%), using medical record documentation, and telephone survey as needed. The mean follow-up for all patients was 6 years (range 5–8 years). A total of 3% (8/238) were revised. Reasons included: (i) femoral loosening in 4, (ii) Iliopsoas impingement in 1, (iii) metallosis/adverse tissue reaction in 1, (iv) femoral neck fracture following motor vehicle accident in 1, and (v) unknown reasons in 1. Of the 238 patients, 55 (23%) were female, 2 (2/55; 3.6%) of whom have since undergone revision surgery for either metallosis/adverse tissue reaction, or unknown reasons. Of the 53 women who retained their BHR at 5-year follow up, the average HHS was 96.5. Of the 238 patients, 183 (77%) were male patients, 6 (6/183; 3.2%) of whom have since undergone revision surgery for femoral component loosening, iliopsoas impingement, or femoral neck fracture sustained in a motor vehicle accident. At 5-year follow-up, 177 male patients retained their implant and had an average Harris Hip Score of 98.8. The overall implant survival was 96.6% at approximately 5 years. Conclusion. In our cohort of patients aged ≤50 treated with BHR [Fig. 1], our results demonstrated 5-year survivorship of 96.6%, with average HHS of 98.8 in males and 96.5 in females. This study demonstrates HRA is a successful alternative to traditional THA in a challenging cohort of younger, active patients

Introduction. There is no consensus on the ideal management of young, active patients with disabling coxarthrosis. Within this group, patients with femoral head defects secondary to cysts or avascular necrosis pose particular challenges. Resurfacing arthroplasty is contraindicated and the results of traditional total hip arthroplasty are suboptimal in this group. The BMHR was designed to offer a bone conserving option for these patients. We report the outcome of this device in the short term. Methods. This prospective study examines the clinical and radiological outcome of a consecutive series of patients treated with the BMHR arthroplasty. All patients had femoral head defects and disabling hip pain. Patients were reviewed pre operatively and then at 6 weeks, 12 weeks, and 1year post operatively and then yearly. Oxford, Harris and WOMAC hip scores were calculated at each review. Radiological assessment was also performed at each follow up. Results. Forty one patients were included (28 males, 13 females). Average age was 48.0 years (3.8 to 65.1 years). All patients participated in 2 or more sporting activities. Average follow up was 12 months (3–19). Pre and post operative OHS, HHS and WOMAC scores were 34, 46 and 42 and 18, 91 and 6 respectively (p< 0.0001 in all cases). There were no complaints of pain or reduced function at last follow up and there were no revisions or pending revisions up to last follow up. All components were well fixed radiographically. Discussion. The BMHR arthroplasty has shown good early results in treatment of young, active patients with femoral head defects. It seems to offer a resurfacing option in this group with the inherent benefits of improved stability and while allowing preservation of femoral bone stock. There is also the potential for a technically less demanding future revision on the femoral side

Aims: Resurfacing arthroplasty of the hip is increasing in popularity. Recently concerns have been raised about resorbtion of the femoral neck after hip resurfacing, which may increase the risk of femoral neck fracture. We conducted a study to assess the degree of femoral neck resorbtion after using a cemented femoral component at hip resurfacing arthroplasty and to compare this with an uncemented femoral component. Patients and Methods: We included 130 patients who had undergone a hip resurfacing arthroplasty in our study. Our uncemented group included 70 consecutive patients who had received an uncemented Cormet hip resurfacing arthroplasty (Corin, Cirencester, UK). Our cemented group included 60 patients who had received a cemented Birmingham hip resurfacing arthroplasty (Smith and Nephew, Cambridge, UK). All patients were regularly followed up for a minimum of two years. Clinical outcome was assessed using Harris hip scores. Femoral neck resorbtion was assessed by measuring the cup-neck ratio on post-operative radiographs by two independent observers. Results: The mean age of the patients was 50.7 years for the cemented resurfacing group and 51.5 years for the uncemented resurfacing group. No difference was found in Harris hip scores between the two groups at any of the follow-up periods. The overall survival rate at two years was 100% for the cemented group and 98.6% for the uncemented group. There was however, a significant increase in femoral neck resorbtion for the cemented resurfacing group compared to the uncemented resurfacing group (median cup-neck ratio 1.11 vs. 1.04), p< 0.0001. Conclusion: We found a significant increase in femoral neck resorbtion with the use of a cemented femoral component at hip resurfacing arthroplasty compared with an uncemented femoral component. This may increase the risk of femoral neck fracture and could affect the long-term outcome if a cemented femoral component is used

Purpose: Resurfacing arthroplasty (RA) is becoming popular as an alternative to total hip arthroplasty (THA). Direct to consumer advertising reports good to excellent outcomes and patients sometimes seek RA on the assumption that it provides increased survivorship over THA. We report the 5 year survivorship of 25 RA procedures done at one institution. Method: 25 patients were prospectively followed after receiving a Conserve Plus RA through a direct lateral approach between 2002 and 2005. There were 22 males and 3 females with an mean age at surgery of 42 years. The average length of follow-up was 40 months. Failure was defined as revision of the components or a pending revision. Results: At a mean of 2 years follow-up, 3 patients had been revised and 2 more were scheduled for revision surgery for a failure rate of 20%. Reasons for revision included 1 neck fracture and 2 aseptically loose acetabular components. The 2 patients waiting for revision also had aseptically loose acetabular components. Patients receiving or requiring revision were operated on throughout the series and were not necessarily part of the surgical learning curve. Conclusion: RA of the hip done through a direct lateral approach in this series had an unacceptably high failure rate for aseptic loosening of the acetabular component

A ceramic-on-ceramic hip resurfacing implant (cHRA) was developed and introduced in an MHRA-approved clinical investigation to provide a non metallic alternative hip resurfacing product. This study aimed to examine function and physical activity levels of patients with a cHRA implant using subjective and objective measures both before and 12 months following surgery in comparison with age and gender matched healthy controls.

Eighty-two unilateral cHRA patients consented to this study as part of a larger prospective, non-randomised, clinical investigation. In addition to their patient reported outcome measures (PROMs), self- reported measures of physical activity levels and gait analysis were undertaken both pre- operatively (1.5 weeks) and post operatively (52 weeks). This data was then compared to data from a group of 43 age gender and BMI matched group of healthy controls. Kinetics and kinematics were recorded using an instrumented treadmill and 3D Motion Capture. Statistical parametric mapping was used for analysis.

cHRA improved the median Harris Hip Score from 63 to 100, Oxford Hip score from 27 to 48 and the MET from 5.7 to 10.3. cHRA improved top walking speed (5.75km vs 7.27km/hr), achieved a more symmetrical ground reaction force profile, (Symmetry Index value: 10.6% vs 0.9%) and increased hip range of motion (ROM) (31.7° vs 45.9°). Postoperative data was not statistically distinguishable from the healthy controls in any domain.

This gait study sought to document the function of a novel ceramic hip resurfacing, using those features of gait commonly used to describe the shortcomings of hip arthroplasty. These features were captured before and 12 months following surgery. Preoperatively the gait patterns were typical for OA patients, while at 1 year postoperatively, this selected group of patients had gait patterns that were hard to distinguish from healthy controls despite an extended posterior approach. Applications for regulatory approval have been submitted.

Introduction: Preliminary results of the Birmingham Hip Resurfacing Arthroplasty were promising. The first series with minimum 5 year follow up was published in 2005 and came from the designing centre. Survivorship and functional results were good. This is the first series with a minimum 5 year follow up not from the designing centre. Methods: All patients who underwent BHR between the dates of October 1999 and May 2002 were included in the study. Results: We report 114 of 117 (97% follow up) consecutive metal-on-metal hip resurfacings in 105 patients with a minimum of 5 years follow up. Revision of either the femoral or acetabular component during the study period is defined as failure. We had 4 failures giving a survivorship at 5 years of 96.5% (95% confidence interval (CI) 93–100). The mean follow up was 72 months and the mean age at implantation was 54.5 years old (Range 35–75). All patients were followed up clinically and radiographically. The mean Harris hip score at follow up was 96.4. The mean Oxford Hip Score fell from 41.6 preoperatively (Range 16–57) to 15.3 postoperatively (Range 12–49) p< 0.0001. The UCLA Activity Scale rose from 3.93 preoperatively (Range 1–10) to 7.54 postoperatively (Range 4–10) p< 0.001. Radiographic analysis revealed an average stem shaft angle of 130.6 degrees (Range 112–148) with average cup alignment of 36 degrees (Range 22–47). Neck thinning was present in 16 hips (14%) and we define a technique for measuring thinning. Discussion: This study confirms that metal-on-metal resurfacing produces an excellent clinical and functional outcome in the younger patient who requires surgical intervention for hip disease. The results compare favourably with those from the originating centre and confirm that resurfacing is well suited for younger higher demand patients

In 1997 the Birmingham Hip Resurfacing was introduced to address the needs of young active patients. Alternative designs were introduced to try and improve wear performance. The aim of this study was a comparative cohort study of two types of metal-on-metal bearing to determine the mechanism of failure at 15 years.

The study reviewed 91 Brimingham Hip Resurfacings (BHR) (Smith and Nephew) and 715 DUROM hip resurfacing (Zimmer) procedures in prior to 2009. Failure was defined as revision of either component for any reason. Kaplan-Meyer survivorship analysis performed. Routine follow-up with serum metal ion levels and radiographs.

Mean follow-up was 17.9 years (range 15.2 – 25.1). The mean age at operation was 51.6 years (SD 8.6, range 20.7 to 70.2), including 299 women (37.1%). The Birmingham resurfacing demonstrated 92.3% survivorship at 15 years (SE 2.8, 95% CI 3.9 – 7.8) and 90.0% at latest follow-up (SE 3.5, 95% CI 4.9 to 9.4). By comparison, the DUROM survivorship at 15 years was 89.1% at 15 years (SE 1.2, 95% CI 2.0 to 2.5) and 87.4% (SE 1.3, 95% CI 2.5 to 2.3) at latest follow-up. There was no statistically significant difference in survivorship between groups (p= 0.32). Survival in male patients was 92.7% compared to 80.0% in females. The reported failures occurred from Adverse Reaction to Metal Debris (32 patients), periprosthetic femoral neck fracture (6) and aseptic loosening (41), PJI (12) and undiagnosed pain (6). The mean cobalt and chromium levels at last follow-up were 33.4 nmol/L and 36.5 nmol/L respectively.

This study demonstrates two differently designed metal-on-metal hip resurfacing provided a durable alternative to total hip replacement, particularly in younger male patients with osteoarthritis. Differences in design did determine the reason for revision with acetabular fixation being one of the principal failure mechanisms for the DUROM compared to elevated ion levels.

Abstract

Iliopsoas tendonitis occurs in up to 30% of patients after hip resurfacing arthroplasty (HRA) and is a common reason for revision. The primary purpose of this study was to validate our novel computational model for quantifying iliopsoas impingement in HRA patients using a case-controlled investigation. Secondary purpose was to compare these results with previously measured THA patients.

We conducted a retrospective search in an experienced surgeon's database for HRA patients with iliopsoas tendonitis, confirmed via the active hip flexion test in supine, and control patients without iliopsoas tendonitis, resulting in two cohorts of 12 patients. The CT scans were segmented, landmarked, and used to simulate the iliopsoas impingement in supine and standing pelvic positions. Three discrete impingement values were output for each pelvic position, and the mean and maximum of these values were reported. Cup prominence was measured using a novel, nearest-neighbour algorithm.

The mean cup prominence for the symptomatic cohort was 10.7mm and 5.1mm for the asymptomatic cohort (p << 0.01). The average standing mean impingement for the symptomatic cohort was 0.1mm and 0.0mm for the asymptomatic cohort (p << 0.01). The average standing maximum impingement for the symptomatic cohort was 0.2mm and 0.0mm for the asymptomatic cohort (p << 0.01). Impingement significantly predicted the probability of pain in logistic regression models and the simulation had a sensitivity of 92%, specificity of 91%, and an AUC ROC curve of 0.95.

Using a case-controlled investigation, we demonstrated that our novel simulation could detect iliopsoas impingement and differentiate between the symptomatic and asymptomatic cohorts. Interestingly, the HRA patients demonstrated less impingement than the THA patients, despite greater cup prominence. In conclusion, this tool has the potential to be used preoperatively, to guide decisions about optimal cup placement, and postoperatively, to assist in the diagnosis of iliopsoas tendonitis.

Background

Hip resurfacing arthoplasty (HRA) showed promising early and mid-terms results at the beginning of the new millennium. Adverse local tissue reactions associated with metal debris considerably slowed down the implantation of HRA which use is now limited to a few specialized centers. The long term success of this procedure, however, is still largely unknown. This study aimed to provide the clinical results of a series of 400 consecutive HRA with a minimum follow-up of 20 years.

A 34-year-old woman with a benign form of osteopetrosis developed osteoarthritis of the hip. In order to avoid the difficulties associated with inserting the femoral component of a conventional total hip arthroplasty, a hybrid metal-on-metal resurfacing was performed. There were several technical challenges associated with the procedure, including the sizing of the component, press-fit fixation of the acetabular component and femoral head preparation, as well as trying to avoid a fracture. No surgical complication occurred. After more than a year following surgery, the patient showed excellent clinical function and remained satisfied with the outcome. We conclude that the hybrid metal-on-metal resurfacing arthroplasty represents a valuable option for the treatment of patients with osteopetrosis and secondary hip osteoarthritis.

We performed 96 Birmingham resurfacing arthroplasties of the hip in 71 consecutive patients with avascular necrosis of the femoral head. A modified neck-capsule-preserving approach was used which is described in detail. The University of California, Los Angeles outcome score, the radiological parameters and survival rates were assessed. The mean follow-up was for 5.4 years (4.0 to 8.1). All the patients remained active with a mean University of California, Los Angeles activity score of 6.86 (6 to 9). Three hips failed, giving a cumulative survival rate of 95.4%. With failure of the femoral component as the endpoint, the cumulative survival rate was 98.0%. We also describe the combined abduction-valgus angle of the bearing couple, which is the sum of the inclination angle of the acetabular component and the stem-shaft angle, as an index of the optimum positioning of the components in the coronal plane.

Using a modified surgical technique, it is possible to preserve the femoral head in avascular necrosis by performing hip resurfacing in patients with good results.

Patients undergoing hip resurfacing arthroplasty (HRA) is typically reserved for highly active patients. Patient Reported Outcome Measures (PROMs) such as the Oxford Hip Score (OHS) are reported to have ceiling effects, which may limit physicians' ability to measure health gain in these patients. The Metabolic Equivalent of Task (MET) index is a validated compendium assigning energy expenditure to a wide range of activities; for example, a slow walk expends 2.9 kcal/kg/hour, golf expends 4.0 kcal/kg/hour, while moderate lacrosse typically expends 8.1 kcal/kg/hour. We hypothesized that for patients with high OHS (47–48) after HRA, the MET index could better discriminate between high-performing individuals.

We evaluated 97 consecutive HRA patients performed by a single surgeon. They prospectively completed an online Oxford Hip Score. They also listed three activities which they had performed independently in the preceding 2 weeks with a Likert-scale slider denoting intensity of effort. Matched data-sets were obtained from 51 patients, from which 23 had OHS of 47–48 at 6-months. Their activity with the highest MET index was selected for analysis. The 23 patients' OHS improved from 29.3 ± 7.0 preoperatively to 47.6 ± 0.5 after 6-months, while their MET indices improved from 8.5 ± 3.7 to 12.9 ± 3.5 kcal/kg/hr. The activities performed by these high-performance individuals ranged from the lowest, pilates (8.05 kcal/kg/hour), to highest, running at 22km/hr (23 kcal/kg/hour). 45% of patients undergoing HRA in this cohort had OHS of 47 and 48 at 6-months after surgery.

Unlike the OHS, the MET index described variation in physical activity in these high-performance individuals, and did so on an objective measurable scale.

Introduction

Hip resurfacing arthroplasty (HRA) lost its popularity because of excessive wear of the ASR M/M design. Now that causes of wear have been identified, it remains an attractive treatment option for young patients because of its bone-conserving nature, the preservation of bone mineral density, a low dislocation rate, and its biomechanical precision.

Hip resurfacing remains a safe and effective option according to registry data. Results in women were less reliable, in part owing to soft tissue impingement. Biolox Delta ceramic bearing couples are now in widespread use with very low complication rates. We set about merging these three elements to develop a novel hip resurfacing arthroplasty.

Contours of both acetabular and femoral components were generated from biometric data, adapted to the constraints of ceramic machining, to ensure that radii blended from the bearing surface avoiding any sharp boundaries. Plasma spray coating with titanium and hydroxyapatite direct onto ceramic was developed and tested using shear, tensile and taber abrasion testing. Wear testing was carried out to 5 million cycles according to the ASTM. Destructive testing was carried out in a variety of test conditions and angles.

Cadaveric testing demonstrated stability using a single use disposable instruments for both conventional and patient specific procedures. Very low dose CT enabled the entire interface to be observed as the Ceramic is radiolucent, enhancing migration analysis, which will be undertaken at 4 intervals to confirm stability. Functional scores and gait analysis will be used in the safety study.

The CE study recruitment is underway, with first in human trials starting in summer 2017. PMA submission will follow the safety study. Commercial release of the device in Europe is unlikely before 2019, and in the USA may not be until 2027. The path to novel device development in 2017 is very costly in time and money.

We aimed to demonstrate the clinical safety of a novel anatomic cementless ceramic hip resurfacing device. Concerns around the safety of metal on metal arthroplasty have made resurfacing less attractive, while long term function continues to make the concept appealing. Biolox Delta ceramic is now used in more than 50% of all hip arthroplasties, suggesting that it's safety profile is acceptable. We wondered if a combination of these concepts might work?

The preclinical testing of anatomic hip resurfacing device developed by our group was presented last year. A twenty patient safety study was designed. Patients had to be between the ages of 18 and 70. The initial size range was restricted to femoral heads between 46 and 54, representing the common sizes of hip resurfacing. The primary outcomes were clinical safety, PROMs and radiological control. Secondary outcomes include CTRSA and metal ion levels.

20 patients were recruited, aged 30–69. 7 were women and 13 were men. There were no operative adverse events in their operations undertaken between September 2017 and February 2018. One patient had a short episode of atrial fibrillation on the second postoperative day, and no other complications. At three months the median oxford hip score had risen from 27 (range 14–38) to 46 (31–48). Cobalt and chromium levels were almost undetectable at 3 months. Fixation appeared satisfactory in all patients, with no migration detected in either component. CTRSA is in process.

The initial safety of a novel cementless ceramic resurfacing device is demonstrated by this data. The 10 year, 250 case efficacy study will continue in 5 other European centres.

Introduction

Metal on metal hip resurfacing (MMHR) has been advocated for the younger patient for several reasons including for the preservation of bone stock and ease of revision to total hip replacement (THR), thus ‘buying an additional operation’ for the patient. This rationale however assumes a good functional outcome after the revision to a THR and that the results of the ‘revision primary’ will not be compromised by the resurfacing which preceded it. We present our data on a consecutive series of 68 revised MMHRs.

Introduction

Because of concerns regarding excessive wear and short-term failures attributed to the metal-on-metal bearings, the use of metal-on-metal hip resurfacing arthroplasty (MOMHRA) has been greatly reduced since 2008, despite great mid-term results for well-designed implants and in certain patient populations. The true cause of excessive wear was then unknown. Therefore, identification of true risk factors for the procedure became paramount to refine indications and improve survivorship outcomes.

As an alternative to total hip arthroplasty (THA), hip resurfacing arthroplasty (HRA) provides the advantage of retaining bone stock. However, femoral component loosening and femoral neck fracture continue to be leading causes of revision in HRA. Surgical technique including cementation method and bone preparation, and patient selection are known to be important for fixation. This study was designed to understand if and to what extent compromise in bone quality and the presence of cysts in the proximal femur contribute to resurfacing component loosening.

A finite element (FE) model of a proximal femur was used to calculate the stress in the cement layer. Bone density to Young's modulus relationship was used to calibrate the bone stiffness in the model using computed tomography. A contemporary resurfacing implant (BHR, Smith & Nephew) was used in the FE model. The effect of reduced bone quality (35% reduction relative to normal baseline; osteoporosis threshold) and presence of cysts on stress in the bone cement layer was then assessed using the same FE model. The center of the cyst (a localized spherical cavity 1 cm in diameter) was located directly under the contact patch. Simulations were run with two locations of the center of the cyst, on the surface of the resected bone and 1 cm below it. The surface cyst was filled with bone cement, but the inner cyst was empty. The contact force and location for the model were obtained from instrumented implant studies. Simulations were run representing the peak loads during two activities, jogging and stand-up from seated position.

While density reduction of the bone reduced the stress in the CoCr femoral head, the Von-Mises stress in the cement layer was amplified. The peak Von-Mises stress in the cement layer under the contact patch increased more than six times for the jogging activity, and more than ten times for the stand-up activity, relative to values for normal bone density. The impact of cysts on the cement layer stress or the strain distributions in the bone were minimal.

The results show a greater risk of failure of the cement layer under conditions of reduced bone density. In contrast cement stresses and bone strains appeared to be relatively immune to a surface cyst filled with bone cement or an empty inner cyst. Contraindications of hip resurfacing include severe osteopenia and multiple cysts of the femoral head, however no strict or quantitative criteria exist to guide patient selection. Research similar to the one presented herein, maybe key to developing better patient selection criteria to reduce risk associated with compromised femoral head fixation.

In a study of 76 consecutive hip resurfacing arthroplasty procedures, the reasons for choosing this procedure rather than total hip arthroplasty (THA) were reviewed. Patient age, preoperative diagnosis, presence of bone deficiency and other technical factors were considered.

The mean age of patients, 79% of whom were men, was 44 years (20 to 76). The preoperative diagnosis in 59% of patients was osteoarthritis and in 37% avascular necrosis. The decision to resurface the hip rather than to perform THA was influenced primarily by the patient’s choice. In 43 cases (57%), the patient had prior knowledge of the procedure and specifically that it be considered. Other important considerations were the patient’s level of physical activity, the expectation of non-compliance with mobilisation and rehabilitation, the expectation of instability of the hip, the quality of bone and the surgeon’s experience with the surgical technique.

As experience of the procedure grew, the mean age of patients who underwent resurfacing arthroplasty increased. The early clinical results of resurfacing indicate that the range of motion is less than in hip replacement, that the resurfaced hip demands less care against dislocation or wear, and that the patient mobilises and rehabilitates more rapidly and reaches a higher level of physical ability than with THA. As mid-term and long-term results become available, the indications for and prevalence of hip resurfacing arthroplasty are likely to increase.

There is only a paucity of information on the outcome of resurfacing arthroplasty in patients suffering from hip osteoarthritis secondary to developmental dysplasia (DDH). When performing arthroplasty in dysplastic hips, the anatomic abnormalities offer reconstructive challenges, in particular in resurfacing. The present study was therefore conducted to address the following questions: Can hip resurfacing arthroplasty provide satisfactory clinical results in patients with DDH? Can the patients return to sports and recreational activities? Can the hip biomechanics be restored? And finally, can surface arthroplasty reestablish a normal, symmetric gait pattern? The study comprised 24 consecutive patients (32 hips) with a mean age of 44.2 years who underwent surface replacement due to hip osteoarthritis secondary to DDH. Surgery was performed by two senior surgeons using either the Durom implant or the Birmingham Hip Resurfacing prosthesis, dependent on the surgeon’s preference. At a mean follow-up of 43 months, all patients were evaluated cross-sectionally. We assessed clinical and radiographical data and investigated spatiotemporal gait parameters using an electronic mat. The Harris Hip Score improved from 54.7 +/−13.3 to 97.3 +/−5.2 (p< 0.001) and University of California at Los Angeles (UCLA) activity levels increased from 5.3 +/−2.0 to 8.6 +/−1.6 (p< 0.001), respectively. Hip flexion improved from 95.7° +/−16.5° to 106.7° +/−10.6° (p< 0.001). At a mean of 11.2 +/−4.8 weeks after surgery, all patients returned to sports activity. They participated in a mean of 6.0 +/−2.6 different disciplines, 2.8 +/−1.3 times and 4.1 +/−3.6 hours per week. The most common disciplines were cycling, swimming, exercise walking and downhill-skiing. Spatiotemporal parameters of gait demonstrated a symmetrical gait pattern without major differences to normative data. Both, the hip lever arm ratio and the femoral offset increased significantly (p< 0.001) from 0.48 +/−0.07 to 0.57 +/−0.08 and from 39.3 +/−8.2 mm to 45.6 +/−6.2 mm, respectively. Grade I heterotopic ossifications were seen in two hips, there were no Grade II or III ossifications. Two surface replacements failed, both failures could be attributed to surgical errors. The surface arthroplasty risk index was 3.2 +/−1.4 for the entire cohort and 4.5 for the revision cases. Femoral radiolucencies were detected in ten of the remaining 30 hips. The present study demonstrated that hip resurfacing achieved satisfactory clinical results in patients with hip osteoarthritis secondary to DDH. The failure rate of 6.3% did not reach our expectations, however, both failures could be attributed to surgical errors. Further follow-up is nevertheless of utmost importance to assess the significance of femoral stem radiolucencies in this young and active group of patients.

The modern humeral head resurfacing was developed by Stephen Copeland, M.D. and introduced in 1986 as an alternative to stemmed humeral implants. At the time, first and second generation monoblock and modular stems with non-offset humeral heads posed many challenges to the surgeon to recreate the pre-morbid humeral head anatomy during anatomic TSA. The consequences of non-anatomic humeral head replacement were poor range of motion, increased native glenoid or glenoid component wear and premature rotator cuff failure. Additionally, the early generation humeral stems were very difficult to extract when revision was needed. The original stemless devices were cup resurfacing implants that were designed based on the early hip experience. The Copeland resurfacing device offered the ability to better match native humeral head anatomy and was considered less invasive and easier to revise. Glenoid exposure required more extensive dissection but TSA could be successfully completed.

Clinical results for motion, function and outcome scores are similar to stemmed implants. The survivorship of the implants is also on par with other available implants and loosening has not been an issue. Stress shielding is not reported. Multiple manufacturers offered similar products all designed to try to predictably recreate the pre-morbid anatomy and to make insertion easier.

Critical review of resurfacing arthroplasty radiographs has raised concern about the challenges of placing the implant with proper sizing and position. Most surgeons have implanted resurfacing implants as hemiarthroplasties. The development of anatomic TSA implants has allowed surgeons to better recreate the normal pre-morbid anatomy of the humerus. Newer stem designs are convertible or easily removable. This counters many of the original design benefits of resurfacing. The primary reason for revision of resurfacing implants is malposition followed by glenoid arthrosis and rotator cuff failure. Revision surgery after resurfacing has had mixed results.

Stemless implants were introduced in Europe 13 years ago. Stemless devices share the benefits of resurfacing as minimally invasive and easier to revise. The added benefit of better glenoid access allows the surgeon to implant a glenoid. Most available implants have minimal follow-up. Mid-term follow-up of one design has demonstrated good fixation and loosening is uncommon. No studies are available that critically evaluate the surgeon's ability to recreate normal pre-morbid anatomy, whether revision arthroplasty is bone preserving and if results of revision will improve.

Stemless shoulder arthroplasty implants for the proximal humerus provide cementless metaphyseal prosthetic fixation. A near-perfect anatomic restoration of the proximal humeral articular surface is possible with this canal-sparing design—avoiding the risks associated with humeral stems and preserving bone for later revision.

When compared with proximal humeral resurfacing, stemless arthroplasty avoids the potential technical errors that may lead to oversized implants, abnormal shift of the glenohumeral joint center of rotation, and excessive strain on the native rotator cuff.

While canal-sparing stemless implants represent a new concept in shoulder arthroplasty without mid- and long-term results, the failures associated with resurfacing humeral arthroplasty have been documented in the literature. Unlike a stemless component, use of a resurfacing technique (and hence preservation of the humeral head) makes glenoid prosthetic implantation challenging and often impossible.

Metal-on-metal hip arthroplasty is nowadays a well spread technique for hip replacement. It is a technically demanding procedure with sine qua non steps. Most of the large Australian, British and north-American clinical outcomes found about 20% early failure, within 3 months, during the steep part of the learning curve. In a biomechanical study on cadaver we showed that valgus and version placements should be appropriate in order to get the most effective strength in compression. But valgus placement is drastically limited by lateral neck notching which leads to early fracture. Anteversion also should be manage to address the cam-type shape of the ventro-lateral femoral neck, since most of the young patient with hip arthritis present retroverted misalignment of the head along the neck axis. The size of the femoral head is another issue because big head component needs a big acetabular cup. Sparing large amount of bone on the femoral side might lead to bone lost on the pelvic side. In order to enhance the placement of the femoral component – smallest one, in valgus, without retroversion and without neck notching – manufacturers propose mechanical device based on neck intraoperative palpation. Digitalized versions of this principle are also available. These systems still demand experienced surgeon to make slight adjustment on entry point and trajectory of the guide-wire. Imageless computer navigation based on proximal femur palpation and atlas is interesting on almost normal bone but could be inaccurate on altered bone, especially cam-type shape. Navigation based on CT scan gives exact 3D information and accurate planning but is still time consuming. Navigation on 2D fluoroscopic view shows good clinical results with only about 20 minutes more than a standard procedure.

We proposed a bone morphing^® procedure with emphasis of surface palpation on head-neck junction to get accurately the personal shape of each femur. Preliminary results on pathological bones showed safe reaming of the head without notching.

Introduction

Hip resurfacing arthroplasty has been surgical options in younger and more active patients with osteoarthritis (OA) and osteonecrosis (ON) of the femoral head. Although excellent midterm results of this procedure have been reported, there is a concern about postoperative impingement between the preserved femoral neck and the acetabular component. There were few reports about kinematics after hip resurfacing. Therefore, the purpose of this study was to investigate the postoperative motion analysis after hip resurfacing using a noble dynamic flat-panel detector (FPD) system by which clear sequential images were obtained with low dose radiation exposure.

Background

The Copeland shoulder resurfacing arthroplasty (CSRA) (Figure1) is a cementless, pegged humeral head surface replacement which has been in clinical use since 1986. The indications for CSRA are more or less the same as conventional stemmed arthroplasty. This procedure can be considered for all patients who require shoulder replacement due to GHJ arthritis resulted from primary or secondary OA, RA, and other variations of inflammatory arthritis. It is also suggested as the first choice option for relatively young patients with post-traumatic arthritis, avascular necrosis (AVN), and instability arthropathy. This observational study reports functional and radiological outcome in CSRA during 4 years follow-up.

Introduction: A common criticism of the modern hip resurfacing arthroplasty is its high early complication rate, in particular femoral neck fracture, displacement of the acetabular component and avascular necrosis. The overall complication rate varies widely in different published series. The sometimes alarmingly high rate of complications, as much as 22% for femoral neck fractures alone (Mont et al. 2005), has deterred many surgeons from using resurfacing implants. As a specialist elective hip practice we wished to specifically determine the early complication rate of hip resurfacing arthroplasty using the metal-on-metal Cormet 2000 implants. We defined an early complication as any resurfacing procedure which required inpatient readmission and/or further intervention within 12 months of the primary operation.

Material and methods: We assessed 253 consecutive hip resurfacing procedures (226 patients). All procedures were performed by the same surgical team using the same surgical approach (posterolateral). Operations were performed between 2001–2005. The mean operating time for was 51.8 minutes. The mean age of patients was 50 years (27 to76) at the time of surgery. 141 patients (62.4%) were male and 85 (37.6%) were female. The preoperative diagnosis was osteoarthritis for the majority of patients 246 (97.2%), the remainder having avascular necrosis (4 cases, 1.6%), chondrolysis (2 cases, 0.8%) or large osteochondral defects (1 case, 0.4%).

Results: In this series there were two infections (one superficial and one deep), one intraoperative femoral neck fracture (converted to THR), no episodes of avascular necrosis, one revision because of acetabular component loosening and one readmission because of a postoperative haematoma 10 days after surgery. All together two patients needed a further operation within one year of the primary operation (one two-stage revision because of deep infection, one revision to THR because of acetabular component shift). The haematoma was treated conservatively. There was one deep vein thrombosis (DVT), one case of iliopsoas tendonitis, one case of trochanteric bursitis and one patient wore an abduction brace for 6 weeks because of slight instability although there was no dislocation. The patient with DVT was readmitted as an inpatient. The overall complication rate (readmission as an inpatient) was 1.6% (4 patients) with the Cormet 2000 implant. Reoperation rate was 1.2% (3 patients) (including the intraoperative conversion to THR).

Discussion: The Cormet 2000 is a fully uncemented hydroxy-apatite coated hip resurfacing implant. In our series we found a low early reoperation and infection rate. All the reoperations were performed for cases were the primary operation was carried out in the first 6 months of this series. There were no complications associated with the uncemented femoral component of the Cormet 2000 implant.

Introduction: ‘Revisability’ has been touted as one of the major advantages of resurfacing arthroplasty of the hip. However, this theoretical advantage has never been clearly demonstrated. The objective of the present study was to test the hypothesis that a failed, modern generation metal-on-metal resurfacing arthroplasty (MMRA) can be converted to a total hip (THA) as easily and with comparable results as a primary (THA).

Methods: Twenty-two failed MMRA’s in 21 patients with an average age of 49.5 years (23 – 72 years) were converted to a THA. In 18 hips, the acetabular component was retained, and in 4 hips both components were revised. The control group of primary THA’s, implanted during the same time period by the same surgeon, consisted of 64 patients with an average age of 50.8 years (27 – 64 years).

Results: There was no significant difference in operative time, blood loss and complication rates between the conversions and the controls. The average follow-up was 47 months (12 – 113 months) for the conversions and 57 months (24 – 105 months) for the controls. Clinical outcomes measures were comparable with average Harris Hip Scores of 92.7 and 90.3 for the MMRA conversions and primary THA’s, respectively. The UCLA activity scores were 6.6 and 6.4 in the conversion group and THA group, respectively. There have been no cases of aseptic loosening of the femoral or acetabular components in either group, and there have been no dislocations after MMRA conversion.

Conclusion: Conversion of failed MMRA to a THA appears to be as safe and effective as a primary THA.

The Birmingham hip resurfacing (Smith & Nephew, Tennessee) (BHR) has been used in younger more active patients.

Aim: The purpose of the study was to compare the placement of the guide wire for the femoral components in hip resurfacing, implanted using computer navigation and a new alignment device(jig).

Materials and Methods: The study was conducted on 13 cadaveric femora. Registration of the femoral head was carried out using Computer Aided Navigation system, Brainlab (BL) by the senior author. Guide wires were inserted using BL by the senior author and subsequently with the alignment device (jig) by the junior author. The junior author was blinded to the templated position and implanted the wire using the jig. In 6 femurs the implantation of the prosthesis was carried out in the position suggested by the BL and in 7 by the jig. All the femora were sectioned transversely after implantation and measurements were taken using callipers and subsequently using Autocad.

Results: There was no notching of the superior femoral neck in either of the groups. The mean and standard deviation of the anatomic neck-shaft angles was 124.91° ± 14.25°. The wire-shaft angle in the BL group was 131.46° ± 5.27° and in the jig group 134.08° ± 3.80°. In the BL group the wire was in 0.85° ± 2.15° of retroversion as compared to 1.38° ± 4.19° of anteversion in Jig group. The position of the wires at the narrowest cross section of the femoral neck is shown in figure.

Conclusion: The alignment device consistently positioned the wire more valgus and anteverted than Computer aided navigation, which was desired. In all cases, the wire position was well within acceptable limits. Computer aided navigation does not seem to offer distinct advantages in resurfacing hip replacements.

Introduction: Pain after total hip arthroplasty (THA) can be caused by infection, aseptic loosening, heterotopic ossification, and referred pain. Psoas tendonitis is a rare cause of groin pain after THA and resurfacing arthroplasty. It is believed to be caused by psoas tendon impingement against a malpositioned acetabular component due to defective anteversion or centring and the use of oversized cups. We report 4 cases of psoas tendonitis following resurfacing arthroplasty and hybrid surface arthroplasty.

Methods: Between April 2004 and June 2005, we diagnosed 4 cases (3 female and 1 male) of psoas tendonitis among 152 cases of resurfacing arthroplasty and hybrid surface arthroplasty (2.6%). 116 patients had a hip resurfacing with ASR prosthesis (2 cases, 1.7%) and 36 patients had hybrid surface arthroplasty with ASR unipolar head on S ROM stem (2 cases, 5.6%). All these patients presented 2–5 months postoperatively with severe groin pain which was exaggerated when moving from the sitting position to the upright position and when going up stairs. Common causes of pain after hip arthroplasty, infection and loosening were ruled out. Radiological and ultrasound examination were performed.

Results: Ultrasound examination revealed thickening of psoas tendon in all cases and fluid collection around the tendon in one case. All cases were treated with corticosteroid injection under ultrasound guidance. Significant but temporary symptomatic relief was achieved in all cases.

Discussion: Psoas tendonitis should be considered in the differential diagnosis of groin pain after hip resurfacing procedures. Ultrasound examination is the initial investigation of choice and corticosteroid injection around the tendon is initial method of treatment. Computerized tomography and surgical options of management should be considered in resistant cases.

There has been renewed interest in metal-on-metal bearings as hip resurfacing components for treatment in young, active patients. This study examines the effects of fixation (cemented or uncemented heads) and bone-implant interface conditions (stem-bone and head-bone) on the biomechanics of the Birmingham hip resurfacing (BHR) arthroplasty, using high resolution, 3-d computational models of the bilateral pelvis from a 45-year-old donor. Femoral bone stress and strain in the natural and BHR hips were compared. Bone remodelling stimuli were also determined for the BHR hips using changes in strain energy. Proximal femoral bone stress and strain were non-physiological when the BHR femoral component was fixed to bone. The reduction of strain energy within the femoral head was of sufficient magnitude to invoke early bone resorption. Less reduction of stress was demonstrated when the BHR femoral component was completely debonded from bone. Bone apposition around the distal stem was predicted based on the stress and strain transfer through the stem. Femoral stress or strain patterns were not affected by the type of fixation medium used (cemented vs. Uncemented). Analysis of proximal stress and strain shielding in the BHR arthroplasty provides a plausible mechanism for overall structural weakening due to loss of bony support. It is postulated that the proximal bone resorption and distal bone formation may progress to neck thinning as increasing stress and strain transfer occurs through the stem. This may be further exacerbated by additional proximal bone loss through avascular necrosis. Medium term retrieval specimens have shown bone remodelling that is consistent with our results. It is unclear if the clinical consequences of neck thinning will become more evident in longer-term follow-ups of the BHR.

Introduction

Female gender, old age (men >60y and women > 55y), severe acetabular dysplasia, poor proximal femoral bone geometry, large (>1cm) femoral head cysts, limb-length discrepancy (> 2cm) and small prosthetic head size (less than 50mm for men and less than 46mm for women) are risk factors for hip resurfacing arthroplasty (HRA).

Introduction:

More and more metal-on-metal hip resurfacing arthroplasty (HRA) implants have been used for active younger patients because of its higher success rate and better function outcomes for this group of patients compared to the traditional total hip arthroplasty (THA). One of the advantages of HRA is femoral neck preservation, which provides better bone structure in case a revision is necessary in the future. However, some believe that the outcomes after revision of hip resurfacing were not as good as the traditional THA. The purpose of this study was to provide our outcomes of the revisions, due to various causes, from over 3000 HRAs.

Introduction: Total hip replacement in one of the most commonly performed operation in orthopaedics in the UK with similar numbers being operated in other parts of the world (2). The main reasons for this magnitude are marked improvement in function and the quality of life. The hip prosthesis has evolved significantly over half a century and better prostheses are available today. These newer implants are required to have a survival of 90% for a minimum of 10 years. The improved survival of the implant tends to have effect on the quality of life as well as the life expectancy. There has been a continuous attempt to quantify this increased life expectancy and survival following total hip arthroplasty.

Materials and Methods: We compared the mortality figures of 3947 patients who had hip resurfacing arthroplasty with the national mortality figures of the UK. The cause of death was determined by telephone call to the next of kin and from the national death register.

Results: The average standardized mortality ratio of hip resurfacing patients compared to national figures over the nine year period was 0.524(99 percent C.I. 0.39 to 0.69). Individual SMR for each year is shown in Table. The number of observed deaths were 86 as compared to the expected deaths number 164. Out of the total 86 deaths over a nine year period, 36 deaths were due to cancer, 25 due to cardiovascular causes, eight due to respiratory conditions, four following accidents and 13 due to other causes such as suicide, old age. In the cancer group 7 patients died of lung cancer and 8 died of blood cell neoplasms. National figures for year 2007 were not yet compiled so SIR for cancer was not calculated.

Conclusion: The results of this study are comparable to other follow up studies on mortality following total hip replacement. This indicates that increased activity following hip resurfacing may help the patients maintain better fitness.

The incidence of cancer needs to be interpreted with caution and can only be ascertained by a prospective study.

The Birmingham Hip Resurfacing (BHR) has been used in the younger more active patient for the treatment of advanced osteoarthritis. Long-term follow-up of the BHR is limited. The Australian national joint replacement registry shows that failure rates vary greatly, depending on implant types. 77 consecutive BHR procedures with a minimum ten year follow-up are reported.

There were 70 patients (44 males and 26 females) with an average operation age of 57.4 years (SD ±12.6). All patients were evaluated, including the “learning curve” patients. The mean follow-up period was 11.42 years (SD ±0.50). The arthroplasties were performed between April 1999 and December 2000 by one surgeon, with a standardised patient selection set of criteria. Data and outcome measurements were collected prospectively and analysed retrospectively. We evaluated Harris Hip Scores, Short Form-36 (SF-36v2) Scores, Tegner Activity Score Scores and McMaster Universities Osteoarthritis Index Scores (WOMAC) comparatively at preoperative, six month and yearly intervals

In 8 patients (10 procedures) the implant was in situ at the time of death. Revision was carried out in 6 hips (7.8%) at a mean time period of 2.5 years (0–10) post-operatively. Failure was due to femoral neck fracture in four patients, acetabular loosening in one and avascular necrosis of the femoral head, leading to loosening, in one patient. Kaplan-Meier analysis showed survivorship of 92.2% to 10 years. The mean Harris Hip scores (paired t-test, p<0.05) improved significantly from 59.7 preoperatively to 80.1 at ten years. The mean SF-36v2 physical scores (paired t-test, p<0.05) improved significantly from 35.09 preoperatively to 47.83 at ten years. WOMAC scores (paired t-test, p<0.05) improved significantly from 54.61 preoperatively to 85.89 at ten years.

The BHR prosthesis, in this series, has been shown to be effective, reliable, and durable in this group of highly active, relatively young patients. Problems with metallic debris, sensitivity reactions, and osteolysis have not been seen. However, we believe that with better selection criteria, improved understanding of component positioning and surgical techniques, results can be improved.

Purpose

To evaluate the radiological changes after metal on metal resurfacing arthroplasty.

Background

The aim of this study is to analysis the ability of these patients, treated with MOMHR, to resume sport activities by gait analysis and clinical evaluations. Metal on metal hip resurfacing (MOMHR) is indicated to treat symptomatic hip osteoarthritis in young active patients. These patients require a high level of function and desire to resume sport activities after surgery.

Introduction: Prevalence of femoral neck fracture in resurfacing hip arthroplasty continues to question if failure is technique-related or due to the inherent bone quality. This study aimed to correlate cement penetration profile during resurfacing hip with inherent bone density. The hypothesis is that osteoporotic bone is unable to support the prosthesis leading to fatigue failure.

Methods: Fifteen patients scheduled for total hip replacement (THR) were recruited to undergo resurfacing arthroplasty prior to THR. Each patient was implanted with a resurfacing femoral component (BHR, Smith & Nephew, Memphis, TN). Antibiotic simplex cement was inserted one minute after mixing at 18°C to fill 10% of the femoral component volume. The femoral head-implant section was removed and kept in buffered formalin. The patients then proceeded with standard THR. The femoral head-cement-prosthesis section was separated using electrical discharge (ED) machining technique and CT-scanned. The depth and volume of cement penetration were measured from the CT scans and correlated with femoral neck bone densities.

Results: Cement penetration was compared for three groups of bone density: normal, osteopenic, osteoporotic. Average cement thickness were found to be 0.36 ± 0.16mm (proximal), 0.28 ± 0.11 mm (centre) and 0.12 ± 0.05 mm. During hip resurfacing, cement is forced into the porous structure, e.g. the trabeculae and airspaces when the femoral component is fixed onto the head of the femur. In normal bone, the trabeculae is dense and air spaces occupy a small volume of the bone. Greater cement penetration was expected in osteopenic and osteoporotic bones. However, no significant difference was found between cement thickness and volume against inherent patient bone density (p> 0.05). High viscosity of the cement may have prevented more cement to penetrate the bone. While the exterior cortex of the femoral head is strengthened by a cement layer, the interior structure of the femoral neck is still susceptible to fracture at high loads. In addition, increased bone necrosis due to the exothermic reaction during cement fixation may predispose patients to fracture.

Discussion: Resurfacing hip replacement is a viable technique if the fracture risk can be reduced by gaining the best possible cement penetration. This would provide continuous cement stiffness with the bone.

Background: Hip resurfacing preserves bone stock on the femoral head. Some authors believe that this is at the expense of sacrificing more bone on the acetabulum and they point out two main reasons for this. Since resurfacing tends to be used in younger and more active individuals a larger head to neck ratio seems desirable in order to provide a better range of movement before impingement. In addition, the acetabular component has to be a minimum of 5 mm thick to prevent deformation on implantation and the subsequent compromise in the congruency of the bearings.

Method: We report the average size of the acetabular components of 220 Cormet resurfacings and 199 Pinnacle cups implanted in our department over a period of 18 months. From these sizes we estimated the mean acetabular bone loss for each procedure.

Results: The mean cup size was 53.7 mm for Cormet and 54.1 mm for Pinnacle i.e. the acetabular component of the resurfacing was smaller than the equivalent uncemented total hip replacement.

Conclusions: These figures show that resurfacing arthroplasty does not necessarily lead to greater acetabular bone loss than a total hip replacement. In our practice, we concentrate upon preserving acetabular bone rather than establishing a large head to neck ratio. In spite of this approach, the occurrence of impingement and dislocation among our patients seems to be as rare as in other comparable series.

Introduction: Patients suitable for hip resurfacing are often young, active, in employment and have bilateral disease. One-stage bilateral total hip replacement has been demonstrated to be as safe as a two-stage procedure and more cost effective. The aim of this study was to compare the results of one-stage with two stage bilateral hip resurfacing.

Methods: Between July 1994 and August 2006 a consecutive series of 93 patients underwent bilateral hip resurfacing within a year. 34 patients in the one-stage group. 44 patients in the two-stage group. The age, gender, diagnosis, ASA grade, total operative time, blood transfusion requirements, medical and surgical complications, length of stay, revision and costs were recorded.

Results: There were no significant differences in age, gender, and ASA grade between the two groups. There were 4 minor complications in the one stage group and 5 in the two-stage group. All complications were of a short-term nature. There was no significant difference in the blood transfusion requirements. There was a significantly longer total mean hospital stay of 5 days (95% c.i. 4.0–6.9) for the two-stage group. No patients had undergone a revision. The hospital received a mean of £6338 per patient for the one-stage group and a mean of £9726 per patient for the two-stage group. However, this included a longer total hospital stay, two anaesthetics and on average two extra out-patient appointments.

Conclusions: This study demonstrates no detrimental effects when performing a one-stage bilateral hip resurfacing in comparison to a two-stage procedure. The advantages of the one-stage procedure are that total hospital stay is reduced by a mean of 5 days and the cost is reduced by a mean of £3388 per patient, a 35% reduction of the cost of a two-stage procedure. These benefits do not appear to come at the cost of increase complications.

Purpose of the study: During resurfacing arthroplasty, excessive valgus of the femoral neck or an insufficient surgical technique can lead to formation of a notch in the femoral head. Although the mechanisms weakening the femoral neck and subsequent fractures are well described, the effects of altered blood supply via the retinacular vessels on potential ischemia of the femoral head are largely unknown. The purpose of our study was to assess blood supply to the femoral head when a notch occurred in the femoral neck during total hip replacement surgery and to deduct possible implications concerning the resurfacing procedure.

Material and methods: Blood supply to the femoral head was measured with laser Doppler fluorometry in 14 hips undergoing total hip replacement for osteoarthritis via a lateral approach with anterior dislocation. An optical laser probe for the fluorometry (Moor Instruments, Wilmington Delewar, 20 mW laser, probe length 780 nm) was introduced via a 3.5 mm hole drilled in the antrolaeral quadrant of the femoral head (leg in neutral position). The position of the probe was checked on the x-ray of the femoral head after resection. A notch was simulated in the lateral posterior portion of the femoral neck using a bone gouge.

Results: Mean patient age was 65 years (range 48–77 years). There were eight men and six women. Two measurements were made: one after dislocation of the hip and the second after simulating the notch. A significant decrease in blood supply measured at more than 50% was observed in all but four hips after simulating the notch. The median decrease in blood flow was 76% (4.4–90.4, p< 0.001).

Conclusion: The retinacular vessels appear to be equally important for the blood supply for osteoarthritic and non-osteoarthritic femoral heads. A notch occurring during hip resurfacing would not only weaken the mechanical resistance of the neck but would also increase the risk of osteonecrosis and subsequent loosening of the femoral component. Consequently, approaches compromising retinacular blood supply (for example the posterior approach) would add a supplementary danger for the integrity and viability of the femoral head.

Introduction: The incidence of younger people requiring arthroplasty is on the rise. Metal on metal Hybrid hip resurfacing arthroplasty is an exciting alternative to conventional arthroplasty, to Orthopaedic surgeons, in young active patients where preserving bone stock is important.

Materials and Methods: All patients with a hybrid Birmingham hip resurfacing arthroplasty (cemented femoral component and a hydroxyappitie coated press fit acetabulum) from 1997–2001, operated by the senior surgeon were followed up. They had annual AP and lateral x-rays, the pre and post op Harris hip scores were recorded and a patient satisfaction survey was done. Results: There were 36 patients, aver follow up 17.2 months, the aver age was 52.Except for 2 patients with femoral neck fractures which required revision there were no other significant complications. Both these patients had a notched femoral neck intraoperatively. There were no revisions for aseptic loosening .The average preop and post op Harris hip scores were 45.5 and 92.1 respectively. There were no radiological signs of loosening. 93% said they would recommend it to others, 93 % rated the surgery as being excellent to good and 96 % returned to normal or near normal level of activity as

Conclusions: We feel that Conservative Hip arthroplasty with resurfacing of the femoral head is an attractive concept particularly in younger patients.

The advantages are preservation of bone stock, non violation of the proximal femur, reduction of stress shielding in the proximal femur and it is quite physiological.

The one important thing is to avoid notching the neck to prevent disastrous fractures. The implant is less forgiving and the learning curve is steep. The ultimate usefulness can only be gauged once longer follow-ups are available.

Introduction:

One reason that young and active patients choose hip resurfacing arthroplasty (HRA) rather than stemmed total hip arthroplasty (THA) is that they wish to return to high impact sports after their operation. Few studies have addressed the outcome in hip arthroplasty patients who choose to participate in high impact sports post-operatively. We therefore wanted to determine if the durability of HRA in highly active patients was decreased.

The use of hip resurfacing arthroplasty (HRA) has largely regressed due to the fear of metal-on-metal bearings. However committed HRA users continue to assert the functional advantages that a geometry retaining implant would have on a patient”s hip. Currently worldwide, HRA is only recommended to men who demand an active lifestyle. Despite this precarious indication, it is not clear to what extent HRA has on higher activity function. The aim of this study was to determine the functional extent to which could be achieved with HRA. The primary objective is to assess the loading pattern change for patients implanted with HRA at high walking speeds and inclinations. The second objective is to compare their loading features to a healthy group to determine if a normal gait pattern could be achieved.

Between 2012 and 2016, a total of 28 prospective unilateral HRA patients were analysed on an instrumented treadmill from a single centre. All 28 patient patients had a uniform implant type and had no other lower limb operations or disease. Perioperative plain orthogonal radiographs were used to measure hip length and global hip offset change. A healthy control group (n=35) were analysed to compare. All HRA patients gait characteristics were assessed at incrementally higher speeds and inclinations to determine the extent of improvement HRA has on a challenging activity. A Student t-test along with a multivariate analysis was done with significance set at α=0.05. Weight and height variance was accounted with Hof normalisation.

The HRA and control group were reasonably matched for age (57 vs 55yrs), BMI (27 vs 25) and height (175 vs 170cm) respectively. Hip measurements revealed less than 5mm change for all cases. The mean time from initial preoperative gait assessment to postoperative assessment was 30 months (24–48months). The mean top walking speed for controls was 1.97m/s and postoperatively 2.1 m/sec for the HRA group. The significant (p<0.001) loading change during flat walking can be seen with restoration of symmetry. Walking at an inclination demonstrated a marked change during weight acceptance (p<0.001) and a loading pattern returning to near normal.

This prospective study found HRA patients walking faster than age matched controls. They demonstrated a significant change in their loading pattern, by significantly shifting load from the unaffected side to the implanted side. Uphill walking, an activity which requires more hip flexion, demonstrated a change in stance phase which was near normal. This small comparative study confirms near physiological function can be achieved with HRA at higher activity levels.

Femoral neck fracture is a serious complication in hip resurfacing arthroplasty and reducing its risk is a major challenge. From a biomechanical point of view changing the geometrical characteristics in surgery could affect the stresses in the femoral neck. We analysed standing AP X-rays of 85 randomly selected patients having pain in the pelvic region in order to gain better understanding of the geometrical influences. Patients were selected on age, weight, pelvis visibility and no deformations of the proximal femur. A variety of geometrical characteristics has been measured and analysed using the two-sided t-test.

A significant difference was found between men and women, which was compared to previous publications in order to verify the measurement method. Statistical indication could not be found for leg-dominancy influencing geometrical dimensions. This is not mentioned in literature, but it is mentioned that the BMC and BMD differs between the legs. Several linear relations have been found between geometrical characteristics and demographics. The average head-neck ratio for both left and right was about 1.4 and the ratio of the abductor moment arm and body moment arm was about 2.1. The linear relation between femoral head diameter and femoral neck diameter indicates that the femoral component should be chosen according to the natural head diameter. The ratio between the abductor arm and body arm in combination with the bodyweight determines the static stresses in the femoral neck and can be changed in surgery by altering the hip axis length and neck shaft angle.

Conclusion: The geometrical characteristics can be changed in surgery and can reduce the stresses in the neck, but in hip resurfacing these changes are relatively small. The question is how much can the geometry be changed and could these changes lead to complications.

Metal on metal hip articulations are associated with the release of cobalt and chromium ions. There are few published reports of these levels following hip resurfacing arthroplasty. This study was undertaken to determine cobalt and chromium ion levels following hip resurfacing arthroplasty.

Ninety-one patients were prospectively entered in a study assessing ion levels following hip resurfacing arthroplasty. Serum, erythrocyte and urine cobalt and chromium levels were measured. Samples were collected preoperatively then at three months, six months and yearly thereafter. Each sample was analyzed with an ICPMS assay machine.

Preoperatively the median values for serum, erythrocyte and urine cobalt and chromium levels were all within the normal range. Median serum cobalt levels increased from baseline (0.1 ug/l) to 1.1 ug/l at one year and 1.6 ug/l at two years. Median serum chromium levels increased from baseline (0.2 ug/l) to 1.9 ug/l at one year and 3.3 ug/l at two years. Median erythrocyte cobalt levels increased from baseline (0.1 ug/l) to 1.0 ug/l at one year and 1.3 ug/l at two years. Median erythrocyte chromium levels increased slightly from baseline (1.0 ug/l) to 1.2 ug/l at both one and two year follow-up. No correlation was seen between ion levels and patient activity, implant position, clinical scores or BMI. No clinical effects of elevated ions were observed. Outliers of either cobalt or chromium were seen in twelve patients (13%) in the series.

Hip resurfacing arthroplasty is associated with significant elevations of cobalt and chromium ions. An increase in serum levels of both cobalt and chromium has been noted at two years. This trend also occurs with erythrocyte cobalt but not with erythrocyte chromium. There is a close correlation between serum and erythrocyte cobalt levels but not between serum and erythrocyte chromium levels. We recommend using serum cobalt and serum chromium measurements as a standardised method of ion analysis following metal on metal hip replacement. This allows for capture of maximal levels of both ions in vivo. Further study is required to determine if any clinical effect will be seen as a result of these elevated ions.

Aim: The purpose of this study was to analyze the in-vivo wear rates of Birmingham Hip Resurfacing (BHR, Midland Medical Technologies Ltd., Birmingham, U.K.) explants and to contrast the results to the wear rates of conventional 28 mm metal-on-metal bearings (Metasul, Zimmer GmbH, Winterthur, Switzerland).

Methods: The wear rates, measured by a coordinate measuring machine (CMM5, SIP, Geneva, Switzerland), of 6 femoral components and two complete pairings of the BHR retrieved from 8 hips were contrasted to 43 28 mm heads from second generation metal-on-metal bearings (Metasul, Sulzer Orthopaedics Ltd., Winterthur, Switzerland).

Results: After 13 months (7 to 24) the BHR femoral heads showed a median volumetric wear rate of 2.9 mm³ (interquartile range: 0.8 to 7.1), slightly, but not significantly higher than the investigated 43 28mm Metasul heads (0.8 mm³/year, p = 0.067, 14 months [7 to 24] in-situ). One BHR case with a cup abduction angle of 70° showed a significant higher wear rate of 17.8 mm³. All BHR cases showed only small amounts of metallic particle histological and correspondingly, a mild histiocytic tissue response without foreign body granuloma formation.

Discussion: During the first two years after surgery the investigated BHR components showed wear rates substantially lower than conventional polyethylene bearings, comparable to Metasul bearings, implanted with very successful clinical results. But whether the wear rates will drop down after the so called running-in period comparable to conventional metal-on-metal bearings and provide young and active patients with a biologically acceptable particle volume over a long time period, still remains to be seen.

Metal-on-metal hip resurfacing is increasingly common. Patients suitable for hip resurfacing are often young, more active, may be in employment and may have bilateral disease. One-stage bilateral total hip replacement has been demonstrated to be as safe as a two-stage procedure and more cost effective. The aim of this study was to compare the in-patient events, outcome and survival in patients undergoing one-stage resurfacing with a two-stage procedure less than one-year apart.

Methods. Between July 1994 and August 2006 a consecutive series of 93 patients underwent bilateral hip resurfacing within a year. 34 patients in the one-stage group. 44 patients in the two-stage group. The age, gender, diagnosis, ASA grade, total operative time, blood transfusion requirements, medical complication, surgical complications, length of stay, duration of treatment, revision and Oxford hip scores were recorded.

Results. There were no significant differences in age, gender, ASA grade between the one-stage and the two-stage. There were 4 minor complications in the one stage group and 5 in the two-stage group. All patients that suffered a complication made a full recovery. There was no significant difference in the blood transfusion requirements. The mean anaesthetic time was 136 minutes in the one stage group and 92 minutes in the two-stage group with a significant mean difference of 44 minutes(95% c.i. 31–52). The mean total length of hospital stay was 11 days in the one-stage group and 16 days in the two-stage group with a significant mean difference of 5 days(95\% c.i. 4.0–6.9). The mean difference in length of treatment time of 6.5 months was significant(95\% c.i. 4.0–9.0).

No patients have undergone a revision procedure during the study period and no patient is awaiting revision surgery.

Conclusions. This study demonstrates no detrimental effects when performing a one-stage bilateral metal-on-metal hip resurfacing in comparison to a two-stage procedure. There are advantages of a one-stage procedure over a two-stage procedure for bilateral disease. Total hospital stay is reduced by 31.3% and the mean length of treatment is reduced by 50.0%. These benefits do not appear to come at the cost of increase complications. The complication rate in both groups was very low and all of the complications were short-term and are unlikely to have any bearing on the longevity of the prosthesis.

Pre-existing hip pathology such as femoroacetabular impingement is believed by some, to have a direct causal relationship with osteoarthritis of the hip. The strength of this relationship remains unknown.

We investigate the prevalence of abnormal bone morphology in the symptomatic hip on the pre-operative anteroposterior pelvic radiograph of consecutive patients undergoing hip resurfacing. Rotated radiographs were excluded. One hundred patients, of mean age 53.5 years were included (range 33.4–71.4 years, 32% female). We examined the films for evidence of a cam-type impingement lesion (alpha angle >50.5°, a pistol grip, Pitt's pits, a medial hook, an os acetabuli and rim ossification), signs of acetabular retroversion or a pincer-type impingement lesion (crossover sign, posterior wall sign, ischial sign, coxa profunda, protrusio, coxa vara, Tonnis angle < 5°), and hip dysplasia (a Tonnis acetabular angle >14° and a lateral centre-edge angle of Wiberg <20°).

Pre-existing radiographic signs of pathology were present in a large proportion of hips with low grade (Tonnis grade 1–2) arthritis. There is a group of patients who presented with more advanced osteoarthritis in which we suspect abnormal bone morphology to be a causative factor but, for example, neck osteophytes obscure the diagnosis of a primary cam lesion.

Our findings corroborate those of Harris and Ganz. Impingement is radiographically detectable in a large proportion of patients who present with early arthritis of the hip, and therefore we agree that it is a likely pre-cursor for osteoarthritis. Treatments directed at reducing hip impingement may stifle the progression of osteoarthritis.

Hip resurfacing arthroplasty (HRA) in patients with a varus deformity of the femoral neck-shaft angle (NSA) is associated with poorer outcomes. Our experience has not reflected this. We examined the Oxford Hip Scores (OHS), Harris Hip Scores (HHS) and outcomes of patients with varus hips against a normal cohort to ascertain any significant difference.

We identified 179 patients. Measurement of the femoral neck-shaft angle was undertaken from antero-posterior radiographs pre-operatively. The mean NSA was 128.5 degrees (SD 6.3). Patients with a NSA of less than 122.2 were deemed varus and those above 134.8 valgus. These parameters were consistent with published anatomical studies.

The varus cohort consisted of 23 patients, mean NSA 118.7 (range 113.6-121.5), mean follow-up 49 months (range 13-74). Mean OHS and HHS were 16 and 93.5 respectively. Complications included 2 cases of trochanteric non-union; no femoral neck fractures, early failures or revisions. Normal cohort consisted of 125 patients, mean NSA 128 degrees, mean follow-up 41 months (range 6-76). The OHS and HSS were 18.8, 88.9 respectively. Complications included 5 trochanteric non-unions and 1 revision due to an acetabular fracture following a fall. Statistical analysis demonstrated no statistical difference between the cohorts OHS (p=0.583) or HHS (p=0.139).

Our experience in patients with a varus femoral neck has been positive. Our analysis has demonstrated no statistical difference in hip scores between the cohorts. We have not yet experienced any femoral neck fractures, which we believe is due to the use of the Ganz trochanteric flip and preservation of blood supply.

Hip resurfacing arthroplasty (HRA) in patients with a varus deformity of the femoral neck-shaft angle (NSA) has been cited in the literature as contributory factor towards a poorer outcome. Our experience has not reflected this. We examined the outcomes of patients with varus hips against a normal cohort.

Measurement of the femoral neck-shaft angle was undertaken from standard antero-posterior radiographs pre-operatively. The mean NSA was 128.5 degrees (SD 6.3). Patients less than 122.2 were deemed varus and those above 134.8 valgus. These parameters were consistent with the published literature.

The varus cohort consisted of 23 patients, mean NSA 118.7 (range 113.6-121.5), mean follow-up 49 months (range 13-74), mean OHS & HHS, 16 & 93.5 respectively. Complications included 2 cases of trochanteric non-union; no femoral neck fractures or revisions. The normal cohort consisted of 125 patients, mean NSA 128 degrees, mean follow-up 41 months (range 6-76), mean OHS & HSS, 18.8 & 88.9 respectively. Complications included 5 cases of trochanteric non-union and 1 revision. Statistical analysis demonstrated no difference between the cohorts OHS (p=0.583) or HHS (p=0.139).

Our experience in patients with a varus femoral neck has been positive. Our analysis has demonstrated no difference in outcomes between the cohorts.

Introduction: Metal-on-metal resurfacing is a type of total hip arthroplasty that is conservative on the femoral side. It is controversial whether this procedure should be used in patients with avascular necrosis where the femoral resurfacing component is cemented on dead bone. This study analyzed the clinical and radiographic outcome of patients with avascular necrosis treated with metal-on-metal total hip resurfacing arthroplasty.

Materials and Methods: Thirty-seven patients (41 hips) treated with late-stage avascular necrosis of the hip with a metal-on-metal resurfacing hip arthroplasty were studied. There were 27 men and 10 women who had a mean age of 40 years (range, 16 to 62 years). Patients were followed both clinically and radiographically for a minimum of two years (mean of 3 years).

Results: Overall, there were good and excellent clinical outcomes in 38 hips (93%). Fair results were found in three patients who had excessive heterotopic bone (2 hips) and persistent groin pain (1 hip). There were no cases of component loosening. Radiographic zonal analysis revealed no evidence of impending failure or progressive radiolucencies.

Discussion: Excellent short-term results were found with metal-on-metal total hip resurfacing in this difficult patient population. The authors await long-term results to see if these early excellent results are maintained.

Aims: To determine pre and post-op patient satisfaction and to document complications. Methods: A questionnaire based study of a consecutive series of 71 Birmingham Hip Resurfacings performed by a single surgeon over a two year period. Mean age 54 (range 29 to 70 years). Outcome measures used were the Oxford Hip Score and Short Form 36 Results: There was a signiþcant improvement in outcome scores following surgery. Oxford hip score improved from 41.1 to 16.6 (signiþcant p< 0.05) SF36 score improved from 24.8 to 48.2 (signiþcant p< 0.05) Complications were 2 femoral nerve palsies, 1 lateral popliteal nerve palsy, 1 re-operation for a retained guide pin, 1 post operative fracture, 1 DVT, 1 PE and 8 patients received oral antibiotics for wound erythema or discharge but there were no deep infections. 89% would recommend the operation to a friend, with males rating the operation more highly. Mean visual analogue score of 91% for overall satisfaction, again males rating higher. Conclusions: Birmingham Hip Resurfacing gave signiþcant improvements in patient function, comparable or better than other similar results looking at conventional hip replacement. Patient satisfaction is high despite the younger patient group with active life styles. The group includes one Jiu Jitsu instructor and a triple marathon runner. One patient had previously had a contralateral conventional uncemented total hip replacement which he was pleased with... until he had experienced Òthe ÒfeelÒ of my Birmingham HipÒ

Individuals learn to master new motor skills (such as learning a new surgical technique) by evaluating available feedback to alter future performance. Continuous concurrent augmented feedback is supplementary information presented to the learner throughout the performance of a task. An example of this type of feedback is the visual information provided by computer navigation during arthroplasty surgery. This type of feedback is a potentially powerful tool for learning because it theoretically guides the learner to the correct response, reduces errors, and reinforces correct actions. However, motor learning theory suggests that this type of feedback may impair learning because of development of dependence on the additional feedback or distraction from intrinsic feedback. In the current era of reduced number of training hours it is essential to assess the role of computer navigation on trainees.

Our objective was to determine whether computer navigation influences the learning curve of novices performing hip resurfacing arthroplasty. We conducted a systematic review and critical appraisal of the literature. There is some evidence from randomised controlled trials that navigation use by trainees facilitates accurate placement of arthroplasty components compared to conventional instrumentation. There is no evidence that training with computer navigation impairs performance in retention tests (re-testing on same task after an interval of time) or transfer tests (re-testing in different conditions i.e. without concurrent feedback).

We conclude that although there are significant limitations of the published literature on this topic there is no available evidence that supports concerns regarding the theoretical detrimental effects of computer navigation on the learning curve of arthroplasty trainees.

Adverse bone remodeling in the proximal femur may be detrimental to the long term survival of resurfacing prosthesis. Bone resorption beneath the femoral shell and thinning of the femoral neck have been observed. We present a radiological analysis of the incidence, rate, site of neck thinning and changes observed within the femoral neck, in 100 cases, with a minimum of five years follow-up.

Femoral neck diameter was measured at zero, two and five years post-operatively, at the head neck junction and five mm distally. Pre and post-operative head to neck ratios, natural and reconstructed offset, femoral neck-shaft and stem-shaft angles and cup inclination angle were measured.

Two distinct patterns of neck thinning were observed. In 76 cases (slow thinning group), we observed a reduction of < 5% of original neck diameter at two years and < 10 % at five years (mean 1.5%, sd+/− 1.5). In 24 cases (rapid thinning group), a reduction of > 5% of original neck diameter at two years and > 10% at five years (mean 10.4%, sd+/− 4.8) was observed. The difference in the percentage reduction in neck diameter was significantly different between the two groups at both time points (p< 0.01). Larger head-neck ratios were observed in the rapid thinning group, both pre and post operatively (p< 0.01).

The viability of bone underneath the femoral head may be compromised as a consequence of a non-physiological bone loading mechanism. FEA has predicted stress shielding underneath the femoral head and loading of the mini stem. Compromised blood supply of the retained epiphyseal remnant may play a part in femoral head resorption.

Femoral neck thinning is a phenomenon of unproven aetiology which affects almost 25% of our resurfacing cases.

Background: Resurfacing is becoming increasingly popular as an option for primary hip arthroplasty. However, there is minimal documentation of objective post-operative outcomes which support the perceived benefits of resurfacing over traditional stemmed THR. Most comparative studies have reported differences in X-ray findings, such as component alignment and femoral offset, which only allow speculation of their relative effects on patient function. Studies have also reported general clinical outcomes following resurfacing, and although resurfacing shows promising medium term results, these studies have been largely subjective and have lacked a direct same study comparison with standard THR.

Potential benefits of resurfacing include improved abductor muscle function, resulting from preservation of the femoral neck offset, and greater range of hip motion, resulting from the larger diameter bearings. Mont et al (2007) compared biomechanical outcomes during gait for individuals with unilateral resurfacing and standard arthroplasty and concluded that hip resurfacing yielded superior function, as defined by faster walking speeds. However, comprehensive data of 3-dimensional moments and hip kinematics was not presented and functional assessment was limited to gait analysis only.

Methods: Kinematic and kinetic outcomes were evaluated for 28 individuals (age 40–60) with unilateral resurfacing (Durom, Zimmer) or standard stemmed THR (ceramic-on-ceramic Trident, Stryker) at 3 and 12 months following surgery. Data was collected using an 8 camera Vicon 612 motion analysis system and two Kistler force plates while subjects completed level walking and stair ascent and descent activities using a 4-step stair case, instrumented with a force plate on the second step. A lower limb marker set was used with pointer trial calibration of anatomical landmarks. 3-dimensional hip moments, angles and temporospatial parameters were compared and preferred motion patterns analysed.

Results: Peak hip moments showed no statistically significant group difference during the ambulatory activities although slightly greater peak hip angles were achieved by those with standard THR. Stair negotiation highlighted greater differences in biomechanical outcomes between the groups than level gait analysis. Those with hip resurfacing exhibited less protective motion patterns and performed walking and stair negotiation at a faster pace.

Conclusions: The greater diameter bearings of the resurfacing prosthesis do not appear to yield a greater functional range of motion post-operatively. Preserving the femoral offset with a hip resurfacing does not appear to benefit abductor muscle function. Statistically, both arthroplasty types demonstrate equivalent functional outcomes.

Background: There is a paucity of published literature with regard to metal ion levels following bilateral hip resurfacings.

Method: Recent research has identified femoral component size and acetabular cup anteversion and inclination as important variables involved in metal ion release into the blood. We compared 13 patients with bilateral joints resurfaced using the ASR and 11 patients with bilateral BHRs to those with unilateral joints of similar size and cup inclinations/anteversions. Patients were excluded if the last procedure was within 12 months of blood sampling and if they had other metallic implants. Analysis of standing radiographs to determine cup orientation was carried out using EBRA software. Blood samples were analysed using ICPMS.

Results: Median whole blood Cr and Co values were higher in the BHR bilateral group when compared to the unilateral BHR group by a factor of 1.12 and 1.24 respectively. (5.17 vs 4.59 for Cr, 2.40 vs 1.93 for Co). The difference was significant for Co (p=0.030) but not for Cr (p=0.136). For the large ASR joints (53mm), median Cr and Co values were higher in the bilateral group by a factor of 1.5 and 1.85 respectively. (4.55 vs 2.97 (Cr) 2.83 vs 1.53 (Co)). The difference was significant for both Cr (p=0.001) and Co (p=0.022). For the small ASR joints (< 53mm), median Cr Co values were higher in the bilateral group by a factor of 1.95 and 2.30 respectively. (8.29 vs 4.25 (Cr), 6.78 vs 2.94 (Co)) (p=0.019 Co) (p=0.007 Co).

Conclusion: Metal ion concentrations are significantly greater in patients with bilateral resurfacings. The Cr Co concentrations observed in our patients with bilateral small ASR joints are double those in the published literature on bilateral 28mm metal on metal(MoM) joints implying that the lubrication achieved by small ASRs is sub optimal.

Introduction: In recent retrieval studies over-penetration of cement, incomplete seating of the prosthesis with a resultant polar cement mass, or both, have been associated with femoral failures of current generation resurfacing arthroplasties. We developed a laboratory model to analyze differences in cement penetration, cement pressures and interface temperatures for hip resurfacing arthroplasty.

Materials and Methods: A carbon foam was demonstrated to closely simulate human femoral heads. Custom aluminum shells were made by DePuy with the same inner geometry as the femoral resurfacing components. (ASR™ system, Size 49, DePuy; Leeds, England).

Analyses of six different cementing techniques (cemtech) were performed using high viscosity (HVC) (Smart Set GHV, DePuy, Blackpool, England) and low viscosity cement (LVC) (Endurance, DePuy, Blackpool, England):

Manual application HVC

A force of 150N was used to press five shells in each cemtech group on foam specimens. During seating cement pressures and polymerization heat 5 mm under the foam surface were measured.

Specimens were cut into quarters, surfaces were digitalized and cement penetration areas and depths were quantified using a pixel-analysis-software. The effects of the cemtech were examined by Kruscal-Wallis and Mann-Whitney-U-tests (two-sided, p-value< 0.05, SPSS)

Results: The mean cement pressures increased going from cemtech A to E. HVC cemtech C and E showed higher pressures than the comparable LVC cemtech B and D.

Maximum temperatures were A) 36.0± 4.1°C, B) 45.0±5.7°C, C) 36.2±4.2°C, D) 53.5±2.5°C, E) 48.3±6.5°C and F) 53.2±12.6°C. D, E and F exceeded 50°C.

A provided even cement penetration over the available fixation area without involvement of the internal area and the stem. Cemtech that used LVC cement (B, D and F) showed higher interior area cement contents than HVC (A, E and C). The cement content in the interior area was A) 39.3±26.4mm2, B) 72.1±16.9mm2, C) 37.7±10.5mm2, D) 99.0±24.6mm2, E) 67.5±15.6mm2 and F) 121.0±29.0mm2.

A showed mainly complete seating with a cement mantle thickness of 0.5±0.7 mm. All other cemtech had incomplete seating in all specimens with significantly thicker polar cement mantles (p=0.032) up to a maximum of 4.6±1.2mm for E.

Discussion: Component filling cemtech and LVC resulted in variable degrees of over-penetration, exposure to high temperatures or a risk for incomplete seating, which have been associated with bone necrosis and early fracture. The use of the manual application and HVC cement showed clear advantages in our model. It was possible to utilize all of the available fixation area without negative effects.

Risk of impingement after total hip resurfacing arthroplasty may be great because femoral head-neck unit is preserved and there is little flexibility to adjust limb length and femoral offset, but this potentially worrisome phenomenon has been rarely reported. Impingement between femoral neck and acetabular cup was observed in a cohort of patients who underwent contemporary total hip resurfacing arthroplasty. We then questioned whether patient demographics, component features or suboptimal position of components would be risk factors for impingement.

We reviewed a consecutive series of 51 patients (61 hips) who underwent contemporary total hip resurfacing arthroplasty. The mean age at the time of the index arthroplasty was 38 years (18 to 64). The most common diagnosis leading to the total hip resurfacing arthroplasty was osteonecrosis of the femoral head in 41 hips (67%). All the procedures were performed by single surgeon through an anterolateral approach. All the patients were assessed clinically and radiographically at a mean of 32 months (24 to 53) postoperatively.

Femoro-acetabular cup impingement, defined as the presence of bony spur at the femoral neck corresponding to abutment site of the metallic cup, was observed in seven of the 61 hips (11.5%). Of these, five patients reported limitation of activities due to groin pain. The average postoperative Harris hip score of impingement hips was inferior to those of non-impingement hips (p = 0.004). No significant difference was detected between the impingement hips and non-impingement hips with regard to of patient demographics, component features and radiographic measurements including cup inclination, cup version, femoral component version, anterior femoral offset, stem-shaft angle, femoral offset and limb length discrepancy. Our multivariate analysis revealed that only acetabular cup uncoverage ratio had a significant association with femoro-acetabular cup impingement (p = 0.04, odds ratio 1.385 [95% CI, 1.014 – 1.891]). There was no aseptic loosening of components or femoral neck fracture.

We found a high incidence of impingement between retained femoral neck and metallic acetabular cup after contemporary total hip resurfacing arthroplasty in association with an increased acetabular cup uncoverage ratio. As patients with femoro-acetabular cup impingement showed inferior clinical results, it is crucial to avoid excessive protrusion of acetabular cup beyond bony margin by proper selection of acetabular component size and appropriate positioning.

Although total hip arthroplasty (THA) is quite predictable and durable in older patients, young and active patients have higher rates of revision and these rates are especially increased when the etiology is osteonecrosis. Recent advancement of hip resurfacing technology, HRA has been revived again. Numerous advantages and promising results of HRA have been published. But patient selection and techniques etc still remain issues for HRA in general and especially for patients with osteonecrosis. In the case of HRA in patients with osteoarthritis, the bone quality is stronger and there is no head necrosis and surgical techniques are fundamentally different when compared to osteonecrosis. In osteonecrosis, there is a higher risk and greater concern of the neck fracture due to necrosis and osteoporosis, insecure fixations as well as a progression of necrosis in the subchondral bone. These factors should be considered when assessing hips with osteonecrosis. The ultimate assessment is the condition of the prepared femoral head. This makes resurfacing arthroplasty for osteonecrosis a challenging procedure.

This study was performed to assess the overall clinical and radiological results of the total resurfacing arthroplasty for the patients with osteonecrosis of the femoral head(ONFH) after a minimum 5 year-follow-up.

444 hips of ONFH received resurfacing arthroplasty from Sep 1998 to Mar.2008. 88 hips which were followed up minimally 5 years were included in this study.

Among 88 hips(79 patients) of ONFH that have underwent hip resurfacing arthroplasties from Dec 1998 to Apr 2003, 85 hips(76 patients) were available for the complete study. The mean age at the time of operation was 37 (16–67) years old. The average follow-up period was 80 (60–112) months. The patients were clinically evaluated with the Harris hip score, hip or thigh pain, limb length discrepancy and range of motion. As a radiological evaluation, we observed the changes of implant position, patterns of bone remodeling in the neck and complications such as femoral neck fracture, loosening and osteolysis. Metal ion in the serum was also analysed.

The Harris hip score increased from 77.8 preoperatively to 98.4 at the final visit. Hip abduction/adduction and rotations significantly improved after the operation. Flexion contracture disappeared and further flexion also returned to almost normal. No patient complained of limb length discrepancy and pain on the hip or thigh at the last visit. Although they are not related to the clinical result, some cases showed various types of radiographic changes in the neck of the proximal femur. Neck narrowing was observed in 3 hips. There was no detectable wear or change of position of the acetabular cup and femoral stem.

Our experience with resurfacing arthroplasty in osteonecrosis of the femoral head indicates that the overall results are superior to conventional THA in the aspect of pain relief, the range of hip motion, earlier rehabilitation and earlier return to preoperative activity. This procedure of his resurfacing arthroplasty could be an alternative between joint preserving procedures and THA in the case of early-to-mid staged osteonecrosis of the femoral head especially in younger patients who need arthroplasty. Extent and location of necrosis, and bone quality are the most important factors in resurfacing arthroplasty in osteonecrosis. Precise preoperative planning and meticulous surgical technique is needed to perform resurfacing arthroplasty. But long-term studies are needed to determine the survivorship and to evaluate the metal toxicity after resurfacing arthroplasty.

Introduction

High early failure rates have been reported with certain metal-metal surface arthroplasties and good results have been reported with others. This is a minimum 10-year review of the first 1000 consecutive resurfacings including all ages and diagnoses from one centre.

761 cases in 613 patients with minimal two years follow-up had both metal ion levels and quality pelvis X-ray identified in our database and are included in this study. The UCLA activity score, femoral shaft angle, body mass index, weight, American Society of Anesthesiologists (ASA) score, combined range of motion (CROM), diagnosis, age, implant brand, gender, AIA, bearing size, and duration of implantation were analyzed to determine the potential risk factors for elevated metal ion levels with use of uni- and multi-variable logistic regression models. A safe zone for hip resurfacing (RAIL: Relative Acetabular Inclination Limit) was calculated based on implant size and AIA on AP pelvis X-ray. For AIA below the RAIL, there were no adverse wear failures or dislocations, and only 1% of cases with ion levels above 10 μg/L. We have not found a lower limit of AIA where failures occurred. Other than high inclination angle and small bearing size, female gender was the only other factor that correlated with high ion levels in the multivariate analysis. We have described the robust “safe zone” for acetabular component position based on metal ion levels in a large patient cohort for metal-on-metal hip resurfacing arthroplasty. Our study suggests that adverse wear failures with hip resurfacing may be highly predictable and avoidable. If the AIA is below the RAIL, rare dislocations are also prevented.

The potential for bone remodeling in the proximal femur may be detrimental to the long term survival of resurfacing prosthesis.

A retrospective analysis of radiological changes in the femoral neck was undertaken for 96 patients (100 hips, 76 males and 24 females), with a minimum of 5 years following hip resurfacing. The mean age at surgery was 53.8 years. Femoral neck diameter was measured post-operatively, at 2 and 5 years. Pre and post-operative head to neck ratios, femoral head-shaft offset, femoral neck and implant stem-shaft angles were also measured.

Two groups of patients were identified with differing rates of reduction in their femoral neck diameter. Over the first 2 years, Group A (24%) mean reduction was 2.02mm/year while Group B (76%) mean reduction was 0.33 mm/year. At 5 years, the Group A mean reduction was 5.64mm (sd±2.03mm) while Group B reduction was 1.16mm, (sd±0.97mm). The difference was significant at both time points (p< 0.01). Larger head-neck ratios were observed in the group A, both pre and post operatively (p< 0.01).

Finite Element Analysis has predicted stress shielding underneath the femoral head and loading of the mini stem. This may explain bone resorption underneath the shell and remodeling around the mini stem. Compromised blood supply of the retained epiphyseal remnant may also play a part in femoral head resorption. Group A with a larger proportion of females and femoral heads will potentially have a larger proportion of epiphyseal remnant retained. A further mechanism that could be influential in the development of neck thinning and bone resorption may be due to fluid pumping mechanism causing osteolytic erosion at the bone cement interface.

In conclusion, femoral neck thinning is a phenomenon of unproven aetiology which is affecting almost 25% of our resurfacing cases. Further investigations are needed to determine its aetiology and remedy.

Introduction: Hip resurfacing has become re-established in recent years as a viable option in younger, active individuals. The results of a multi-centre evaluation of the Cormet resurfacing device are presented.

Materials and Methods: Data has been entered from 1997 onwards from 5 centres, patients being selected as suitable by 8 individual surgeons. Pre and intraoperative details recorded including indications, patient details, implant used, Harris Hip Score (HHS) and surgical approach.

Results: A total of 781 procedures in 676 patients have been recorded (54% posterior approach, 40% antero-lateral, 6% Ganz approach). The mean follow-up is 2.5 years (0.1–9.7 yrs) and the mean postoperative HHS is 85.9 (range 25–100). The mean age at surgery was 54.2 years. 60% of implantations were on male patients. The principal diagnosis was; OA 87%, RA 5%, AVN, post-traumatic OA and DDH 2% each, Perthes 1% and the remainder 1%. It is thought likely that many cases of OA had many of the above-named pathologies as a precursor. The mean maximum flexion postoperatively was 98.6 degrees. Uncemented heads (a recent innovation) were used in 7%. Kaplan-Meier survivorship is 93% at 9 years. In the OA subgroup 3.3% have been revised, approximately equal numbers for femoral head collapse, dislocation and cup loosening, but the vast majority due to femoral neck fracture, which in turn was generally associated with the posterior approach.

Conclusions: The results of this cohort (which includes the learning period of the contributing surgeons) indicate highly satisfactory outcomes in terms of HHS and implant longevity. Sub-classification of cases into those presenting abnormal anatomy and those with ‘ordinary’ OA indicates better survivorship still in the latter group. The surgical challenge varies more with hip resurfacing than with standard hip arthroplasty and this should be considered when results of surgery are reviewed. The revision options are generally much simpler than after standard THR.

Introduction: Hip resurfacing has become re-established in recent years as a viable option in younger, active individuals. The results of a multi-centre evaluation of the Cormet resurfacing device are presented.

Methods: Data has been entered from 1997 onwards from 5 centres, patients being selected as suitable by 8 individual surgeons. Pre and intraoperative details recorded including indications, patient details, implant used, Harris Hip Score (HHS) and surgical approach.

Results: A total of 905 procedures in 782 patients have been recorded (52% posterior approach, 39% anterolateral 9% Ganz approach). The mean follow-up is 2.8 years (0.1–9.5 yrs) and the mean postoperative HHS is 86.1 (range 25–100). The mean age at surgery was 54.4 years. 61% of patients were male. The principal diagnosis was; OA 88.3%, RA 4.3%, AVN 2.1%, posttraumatic OA 1.1%, DDH 2.1%, Perthes 0.7% and the remainder 1.4%. It is thought likely that many cases of OA had many of the above-named pathologies as a precursor. The mean maximum flexion postoperatively was 98.7 degrees. Uncemented heads (a recent innovation) were used in 10%. Kaplan-Meier survivorship is 93% at 9 to 10 years. Survivorship in the OA subgroup was 96.7% with approximately equal numbers for femoral head collapse, dislocation and cup loosening, but the vast majority due to femoral neck fracture, which in turn was generally associated with the posterior approach.

Discussion: The results of this cohort (including all contributors’ learning curves) indicate highly satisfactory outcomes in terms of HHS and implant longevity. Subclassification of cases into those presenting abnormal anatomy and those with ‘ordinary’ OA indicates better survivorship still in the latter group. The surgical challenge varies more with hip resurfacing than with standard hip arthroplasty and this should be considered when results of surgery are reviewed. The revision options are generally much simpler than after standard THR.

Introduction Pridie and Steadman independently noticed the development of a smooth layer of fibrocartilage when treating exposed subchondral bone in the knee using their techniques of drilling or microfracture respectively. Since 1997, patients presenting to our unit for a Copeland cementless Surface Replacement Arthroplasty (CSRA) with a congruent glenohumeral joint have routinely undergone biological resurfacing of the glenoid using a technique similar to that described by Pridie and Steadman. We present this technique of glenoid resurfacing, the histological and surgical outcomes in a consecutive group of patients.

Methods/Results Between 1987 and 2002, 218 CSRA were performed without replacing the glenoid. From 1997, 133 CSRA have been performed with multiple drilling of the glenoid face with a guide wire through the subchondral bone in to the underlying soft cancellous bone to stimulate bleeding. This causes formation of a fibrocartilaginous layer – biological resurfacing. 9 (6.8%) of the patients with biological resurfacing have subsequently undergone a shoulder arthroscopy for postoperative impingement pain. This allowed us to evaluate the glenoid surface – macroscopically a layer of cartilage was noted in all patients, intraoperative biopsies have confirmed this layer to be fibrocartilage microscopically. In the biological resurfacing group, the mean postoperative Constant score (CS) is 86.9 (age/sex adjusted), with a mean improvement in CS of 71.0. 3 (2.3%) patients have required revision.

Conclusion Our results confirm that glenoid drilling at the time of CSRA leads to the formation of a fibro-cartilaginous layer over the glenoid, with significant improvements in Constant scores and functional outcomes. These results are comparable to other published results for total shoulder replacement with polyethylene resurfacing of the glenoid and better than patients that have undergone stemmed shoulder hemiarthroplasty.

This study evaluates metal ion levels in patients enrolled in a prospective evaluation of hip resurfacing arthroplasty utilizing the Conserve Plus implant (Wright Medical Technology). Serum, urine and erythrocyte metal ion levels were assessed preoperatively and postoperatively. Average levels at three months were 24 nmol/l for cobalt and 40 nmol/l for chromium. These increased to 40 nmol/l for cobalt and 80 nmol/l for chromium at the six-month mark. The clinical significance of increased metal ion levels is yet to be determined.

To evaluate the clinical, functional and radiographic outcome of hip resurfacing arthroplasty utilizing the Conserve Plus implant (Wright Medical Technology). Serum, urine and erythrocyte metal ion levels were evaluated both pre and postoperatively.

Ion levels for both cobalt and chromium increased from the three-month to the six-month mark postoperatively and were significantly elevated relative to preoperative values.

This study helps to establish a baseline for metal ion levels following hip resurfacing arthroplasty.

Serum, urine and erythrocyte metal ion levels were assessed preoperatively and postoperatively. All levels were within normal range preoperatively. Average serum levels at three months were 24 nmol/l for cobalt and 40 nmol/l for chromium. These increased to 40 nmol/l for cobalt and 80 nmol/l for chromium at the six-month mark. Average erythrocyte metal ion levels at three months were 0.92 ug/l for cobalt and 1.8 ug/l for chromium. The average erythrocyte levels at six months were 1.3 ug/l for cobalt and 2.0 ug/l for chromium.

A prospective multi-center study to evaluate the outcome of hip resurfacing arthroplasty was initiated in July 2003. Each patient was evaluated preoperatively and postoperatively with outcome scores, radiographs as well as serum, urine and erythrocyte metal ion levels.

The results of this prospective evaluation show a rise in ion levels from three to six months postoperatively. Further follow-up is necessary to assess future trends with respect to the ion levels as well as the clinical significance.

Funding: This study has been sponsored in part by Wright Medical Technology.

Introduction: The incidence of femoral neck fracture is approximately 2% after resurfacing hip replacement. Avascular necrosis is thought to be a contributory factor. The aim of this study was to investigate oxygen concentration in the femoral head during metal-on-metal hip resurfacing (MMHR).

Materials and Methods: In ten patients, following division of the fascia lata, a calibrated gas-measuring electrode was inserted into the supero-lateral quadrant of the femoral head via the femoral neck. Xsrays confirmed placement of the electrode 2-3 cms below the femoral head surface. Baseline oxygen concentration levels were recorded immediately upon electrode insertion and used as a reference for all intra-operative measures. Oxygen levels were monitored continuously throughout the operation.

Results: Oxygen concentration was reduced during the surgical approach and average oxygen concentration following dislocation and circumferential capsulotomy dropped significantly (p< 0.005) to 38% of baseline (SD=26%). Insertion of implants resulted in a further significant drop in oxygen concentration (p< 0.04) to 21% of baseline (SD=28%). Oxygen concentration rose slightly, but not significantly after relocation of the resurfaced joint and reconstruction of posterior soft tissues, reaching 22% of initial baseline oxygen levels. Considerable variation between subjects was observed.

Discussion: Intra-operative measurement of oxygen concentration in blood perfusing the femoral head is possible. During MMHR there is a dramatic decrease in femoral head 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 a different surgical approach can protect the blood supply to the femoral head and neck. Measurements of femoral head oxygenation during metal-on-metal hip resurfacing demonstrated a significant concentration decrease during surgical approach and implant fixation.

Introduction:

Alignment of the initial femoral guidewire is critical in avoiding technical errors that may increase the risk of failure of the femoral component. A novel alternative to conventional instrumentation for femoral guidewire insertion is a computed tomography (CT) based alignment guide. The aim of this study was to assess the accuracy of femoral component alignment using a CT-based, patient specific femoral alignment guide.

This study was designed to determine the risk of femoral neck fracture after anterior or posterior notching of the femoral neck. The anterior femoral neck is under tensile forces during gait similarly to the superior neck [6].

Method: Fortyseven 4th generation synthetic femora were implanted with Birmingham Hip Resurfacing pros-theses (Smith & Nephew Inc. Memphis, USA). Implant preparation was performed using imageless computer navigation (VectorVision SR 1.0, BrainLAB, Germany). The prosthesis was initially planned for neutral version and translated anterior, or posterior, to create a femoral neck notch. The femora were fixed in a single-leg stance and tested with axial compression. This method enabled comparison with previously published data. The synthetic femora were prepared in 8 experimental groups: 2mm and 5mm anterior notches, 2mm and 5mm posterior notches, neutral alignment with no notching (control), 5mm superior notch, 5mm anterior notch tested with the femur in 25° flexion and 5mm posterior notch tested with the femur in 25° extension

We tested the femora flexed at 25° flexion to simulate loading as seen during stair ascent. [3] The posterior 5mm notched femoral necks were tested in extension to simulate sporting activities like running. The results were compared to the control group in neutral alignment using a one- way ANOVA:

Results: Testing Group Mean load to failure Significance

Neutral (Control) 4303.09 ± 911.04N

The anterior 5mm notch tested in single-leg stance and anterior notch in flexion displayed lower compressive loads to failure (3374.64N and 3048.11N). The mean load to failure value for the posterior 5mm notches in extension was 3104.62N compared to 4303.09N for the control group.

Our data suggests that anterior and posterior 2mm notches are not significantly weaker in axial compression. The anterior 5mm notches was not significant in axial compression (p=0.38), but trended towards significance in flexion (p=0.087). A 5mm posterior notch was not significant. (p=0.995, p=0.117). The 5mm superior notch group was significantly weaker with axial compression supporting previous published data (p=0.003).

Conclusion: We conclude that anterior and posterior 2mm notching of the femoral neck has no clinical implications, however a 5mm anterior femoral neck notch may lead to fracture. The fracture is more likely to occur with stair ascent rather than normal walking given the reduction in strength noted after testing in flexion. Posterior 5mm notches are not likely to fracture. Hip resurfacing is commonly performed on active patients and 5mm notching of anterior cortex has clinically important implications.

The purpose of this study is to evaluate short to mid-term clinical and radiological results of metal on metal resurfacing arthroplasty in osteonecrosis of the femoral head (ONFH).

185 hips of 169 patients who underwent metal on metal resurfacing arthroplasty using Birmingham Hip Resurfacing system (Midland Medical Technololgies, Birmingham, UK) between December 1998 and May 2005 were available for this study and all cases were followed up over 3 years. All preoperative diagnoses were ONFH. The extents of necrotic area were analyzed by preoperative MRI scanning. Their mean age at the time of operation was 37.7(range, 16–67) years old and mean period of follow-up was 88(range, 36–113) months. For the clinical assessments, Harris hip scores, UCLA activity scores, pain and ROM were evaluated. Radiological changes such as radiolucencies around the stem, impingement sign, neck narrowing, osteolysis around head and neck junction, loosening of implants, heterotopic ossifications were evaluated in the serial antero-posterior, translateral radiographs of the hip joint.

Preoperative necrotic area was average 42.7(range, 11.5–60) %. Clinically, the average Harris hip score was improved from 85.2 points to 97.1 points at final follow-up. Average UCLA activity scores at the last follow-up was 8.8 and almost of the patients showed high activity and returned to their original job. ROM were very satisfactory. Radiologically, the mean inclination of acetabular component was 48.0°. There were no radiolucent lines around the acetabular components, but 3 cases showed radiolucent lines around the stem of femoral components. Osteolytic lesions were noticed in 10 cases around head-neck junction. Nine hips had impingement signs around the head-neck junction. There was no case which showed evidence of stress shielding. Moderate neck narrowing were shown in 3 cases. There were 6 cases of heterotopic ossification. One hip had a revision surgery to a total hip arthroplasty using big metal ball because of loosening of acetabular component. There was no patient complained limb length discrepancy and no infection, dislocation, thigh pain.

The midterm performance of metal on metal resurfacing arthroplasty in ONFH was very excellent in the aspects of pain relief, ROM of hip joints, rehabilitation and return to preoperative activity and minimization of common complications of conventional total hip arthroplasty. There was no mechanical failure related to the osteonecrosis and we can conclude that performing resurfacing arthorplasty in osteonecrosis less than 50% of extent can be justified. However, performing resurfacing arthroplasties in osteonecrosis of femoral heads needs meticulous surgical techniques and longer learning curve to prevent early failure. Even though our midterm follow-up study revealed excellent results, more long-term follow-up studies are mandatory to determine the survivorship and to verify the problems related to the increased serum metal ion and metal ion toxicity after resurfacing arthroplasty.

Variability in femoral head preparation and high cement pressures may be associated with failure to seat femoral components during hip resurfacing. Furthermore, excessive pressures may lead to over penetration of bone by cement with resulting necrosis of the underlying bone. We designed an experimental model to test the hypothesis that partial-length pressure-relief slots made longitudinally in the proximal bone of the femoral head, without extending to the head neck junction, would allow controlled leakage of cement during initial insertion of a femoral head resurfacing component, but would then become sealed during final insertion to prevent excessive loss of cement while still allowing accurate seating of the component.

Thirty-one resurfacing femoral components were cemented onto foam femoral head models. The clearance between foam model and implant was measured to determine the minimum space available for cement. Eleven components were inserted using hand pressure alone, 20 were hammered. Pressure relief slots were prepared in 10 femoral heads. The slots, 4mm deep grooves, were made in the proximal bone only, without extending to the head-neck junction. Cement pressure inside the component was measured during insertion. Implants were sectioned after implantation in order to determine whether they had been fully seated or not. The clinical relevance of the measures taken was tested by measuring the diameter of prepared femoral heads during 20 hip resurfacing operations in order to determine the extent of variability in intra-operative femoral head preparation.

Mean intraoperative clearance between bone and implant was −0.19mm (0.11 to −0.93mm). Mean clearance between foam model and implant was −0.30mm (0.35 to −0.94mm). Full seating was obtained in 22/31 components. Of those not fully seated, all had clearance less than −0.74mm. Full seating with a clearance of less than −0.35mm was only possible when pressure relief slots had been made in the femur. The use of a pressure relief slot longer than half the femoral head length allowed full seating in 9/9 cases, compared to 13/22 without. Cement pressure obtained with a hand pressure technique was less than half that observed with hammering (20.8vs56.0psi, p=0.0009) but was not associated with failure to seat the implant if a slot was used.

Variability of the actual diameter of the femoral head prepared may be associated with difficulty in fully seating resurfacing components. The same degree of variability in the space available for cement was observed in both intra-operative and test specimens. The use of a pressure-relief slot allows full seating of resurfacing implants with hand pressure alone, thereby halving cement pressure, in an experimental model, even when clearance between implant and bone is less than optimal.

Introduction

Modern metal-on-metal bearing resurfacings have been in use for nearly two decades. Local and systemic metal ion exposure continues to cause concern. We could not find a prospective metal ion study in such patients with a 10-year follow-up. This is the first ten year prospective study of metal ion levels in blood and their release in urine following hybrid fixed metal-on-metal surface arthroplasty.

The Birmingham mid-head hip resurfacing arthroplasty (Smith & Nephew, Tennessee) (BMHR) is designed for use in patients with avascular necrosis of the femoral head. The BMHR has limited short-mid term follow-up results. We report the experience of 27 consecutive BMHR procedures with a minimum two year follow-up.

23 patients (20 males and 3 females) with an average operation age of 49.8 years (SD ±10.9) (22–65) were investigated. The mean follow-up period was 3.0 years (SD ±0.77). The operations were between April 2008 and November 2011 by one surgeon. Data and outcome measurements were collected prospectively and analysed retrospectively. Procedures were reviewed to determine function. We evaluated Harris Hip Scores, Short Form-36 (SF-36v2) Scores, Tegner Activity Score Scores and McMaster Universities Osteoarthritis Index Scores (WOMAC) comparatively at preoperative, six month and yearly intervals. Paired samples t-tests were applied to determine improvements where p<0.05 was deemed as significant.

There were no patient deaths. There were no revisions. Harris Hip scores for pre-operative 6, 12, 24 and 36 month intervals were: 52.30, 84.14, 83.07, 87.50 and 89.50. Average pre-operative 6, 12, 24 and 36 month SF36v2 Total scores were: 116.54, 124.32, 130.44, 135.97 and 133.18. Tegner scores for pre-operative 2.75, 3.29, 3.00, 3.67 and 3.01. WOMAC Total scores for aforementioned intervals for the posterior approach were: 59.51, 84.22, 90.30, 86.86 and 92.25.

The mean Harris Hip scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.001). The mean SF-36v2 physical scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.016). WOMAC scores improved significantly between preoperative and 6, 12, 24 and 36 months (p<0.017).

The presence of avascular necrosis significantly increases the revision rate for hip resurfacing surgery. The BMHR prosthesis, in this short term follow-up, appears to avoid the main cause of failure, femoral component loosening. Longer term efficacy remains to be seen. We plan to continue close supervision of these patients.

Introduction: The Birmingham Hip Resurfacing(BHR) has shown encouraging early to medium term results. It has tended to be used in patients wishing to achieve high functional activity. However there is little data available to support this notion. The purpose of the study was to report the functional levels of patients following BHR.

Methods: Since February 2000, 313 patients have undergone resurfacing by the senior author. Two hundred and sixty four patients with a minimum 12 month follow-up were assessed for functional activity using the modified UCLA activity score. Patients were asked to score their activity level during the pre-symptomatic period as well as pre-operatively and during follow-up.

Results: The mean age at surgery was 55.7 years. The mean follow-up period was 46.72 months. The revision rate for any reason was 3.8%. The mean pre-symptomatic, pre-operative, one year post-operative and final follow-up UCLA scores were 7.9, 3.7, 6.6 and 7.0 respectively. At one year 89% (235 patients) had improved by at least one activity grade from pre-operative levels and 35% (93 Patients) achieved functional scores the same as, or better than their pre-symptomatic levels. This increased to 45% at final follow-up. Of the 242 patients previously involved in moderate activity(UCLA> =5), 31% regained this activity level at one year, rising to 40% at last follow-up. Only 19% of the 180 patients participating in very active/impact sports(UCLA> =8) obtained these levels at one year, rising to 30% at last follow-up.

Conclusion: This is the first assessment of function after BHR comparing pre-symptomatic scores with those obtained during follow-up. Functional scores continue to improve beyond one year in all groups. Significant numbers of patients can achieve functional levels at least as good as before they developed symptoms from their hip, however, the proportion of patients achieving this goal reduces with increasing pre-symptomatic activity.

Background

There is much research on metal on metal hip resurfacing arthroplasty (HRA) but few studies have reported the outcome with respect to implant characteristics from non-specialist centres.

Introduction

It was the purpose to evaluate the biomechanical changes that occur after optimal and non-optimal component placement of a hip resurfacing (SRA) by using a subject specific musculoskeletal model based on CT-scan data.

Hip resurfacing arthroplasty (HRA) is increasingly carried out as an alternative to total hip arthroplasty (THA) in young patients. During the procedure, a metal stem on the retrosurface of the HRA is inserted into the femoral head to ensure the implant is located centrally with respect to the femoral neck. It has been suggested that the stem may interfere with bone loading. In light of this, the current study employed finite element (FE) models to investigate the change in the HRA-implanted bone mechanics as a result of removing the stem. FE models of a cadaveric femur pre- and post-HRA surgery were analysed to determine changes in bone stress/ strain.

The implanted models simulated geometry for a cemented HRA with and without a non-cemented stem (HRA-Stem and HRA-NoStem, respectively) and included more accurate multiple material parameters to simulate the non-homogeneous material distribution in the femoral bone. The models included loading conditions simulating an instant at 10% of the gait cycle. Bone stresses/strains in the femoral head and neck of the implanted models were compared with the intact condition to assess the change in bone mechanics. Changes in cement mantle stresses between the HRA-Stem and HRA-NoStem models were also compared.

When comparing similar volumes of bone in the femoral neck, both HRA models showed a similar variation in stress from the intact condition and bone stresses were low in comparison to the ultimate strength of cortical bone. There was less change in peak strain energy in the femoral head of the HRA-NoStem model than the HRA-Stem model. Cement mantle stresses in the HRA-NoStem model were slightly higher than for the HRA-Stem model and the peak compressive stress was close to the fatigue limit for bone cement.

These preliminary results suggest that the bone loading is more normal without the stem. However, there are increased cement mantle stresses.

Introduction

Hip resurfacing arthroplasty has gained popularity as an alternative for total hip arthroplasty. Usually, cemented fixation is used for the femoral component. However, each type of resurfacing design has its own recommended cementing technique.

In a recent investigation the effect of various cementing techniques on cement mantle properties was studied. This study showed distinct differences in cement mantle volume, filling index and morphology.

In this study, we investigated the effect of these cement mantle variations on the heat generation during polymerization, and its consequences in terms of thermal bone necrosis.

Purpose: Hip resurfacing techniques utilize mechanical jigs to align a femoral guide-pin that directs implant placement. Errors in alignment may lead to premature failure. The purpose of this study was to compare femoral guide-pin placement using a computer-assisted surgical (CAS) navigation system to a currently available manual alignment device.

Methods: A computer-assisted navigation system was developed by our group. Target guide-pin position was determined for each cadaveric hip from radiographs. A guide-pin was driven into each hip using either the CAS method or a manual alignment jig (Durom; Zimmer) by a novice or expert surgeon respectively. Radiographic pin position was compared to the target and accuracy was compared between the two techniques.

Results: Guide-pin insertion trajectory using the CAS system was significantly less variable in varus/valgus alignment than the mechanical jig (2.0° SD vs. 5.5° SD; p < 0.05). Ante/retroversion variability was also lower using CAS (4.4° SD vs. 7.7° SD) as was alignment error (CAS: 2.0° ± 2.2° SD valgus vs. Durom: 3.3° ± 5.5° SD varus, p=0.17; CAS: 0.1° ± 4.6° SD anteverted; Durom 3.2° ± 7.7° SD retroverted, p=0.48) but not significantly. Both methods proved accurate in placing the pin within 2 mm from the centre of the neck axis. Procedure time was similar between the two methods

Conclusions: Computer-assisted surgical navigation significantly improves reliability of guide-pin placement. This technique may help achieve better femoral implant alignment regardless of experience and contribute to improving hip resurfacing outcomes.

Funding : Other Education Grant

Funding Parties : Zimmer/UBC Research Fund

Introduction

Lesion location and volume are critical factors to select patients with osteonecrosis for whom resurfacing arthroplasty is appropriate. However, no reliable surgical planning system which can assess relationship between necrotic lesions and the femoral component has been established. We have developed a 3D-MRI-based planning system for resurfacing arthroplasty. The purpose of the present study was to evaluate its feasibility.

Introduction:

Uncemented acetabular component fixation has been considered the most reliable fixation method in contemporary metal-on-metal hip resurfacing arthroplasty (HRA). During prospective long-term follow-up of a HRA device, we have encountered a surprisingly high incidence of this complication and wish to alert surgeons and manufacturers of this problem.

The modern generation of hip resurfacing arthroplasties was developed in the early 1990’s with one of the original designs being the McMinn Resurfacing Total Hip System. This was a hybrid metal on metal prosthesis, with a smooth hydroxyapetite coated press fit mono block cobalt chrome shell with a cemented femoral component. Although no longer produced in this form, lessons may be learned from this original series of components. With metal on metal resurfacing arthroplasty now facing criticisms and concerns with regard function, bone preservation capability and soft tissue issues such as ‘pseudotumors’, it is the aim of this long-term study to assess the outcome and survival of an original series of resurfacing arthroplasties.

27 resurfacing arthroplasties were performed in 25 consecutive patients between June 1994 and November 1996. 16 right hips and 11 left were performed in 14 female patients and 11 male patients. The average age at the time of surgery was 50.5 years (SD 7.9, range 30–63). All surgeries were performed by a single surgeon using a posterior lateral approach. Following the initial early care, each patient received bi-annual follow up along with open access to the clinic with any concerns or complications. A retrospective review of the case notes was conducted and outcome scores retrieved from a prospectively updated database. Radiographs were analyzed and a Kaplan Meier survival chart was constructed for the group.

At latest review 3 patients have died (5yrs, 8yrs and 13.8yrs) and 1 patient has been lost to follow up (5yrs). 7 resurfacings have required revision, all due to acetabular loosening, at a mean follow up of 7 years 11months (SD 2.03years, range 4–10). Metallosis was documented in 4 of the revision cases, however no extensive soft tissue inflammation or ‘pseudotumor’ identified. The mean follow up of the remaining 16 hips is 12years and 10months (SD 12.8months, Range 10.4yrs–14.0 years). The Kaplan Meier survival at a minimum follow up of 10 years is 75.8% (95% CI 0.67–0.95). Mean Oxford hip scores at latest follow up was 20.6 (SD 8.8, range 12–38). There was no significant difference between cup inclination angles for the surviving cohort and those who required a revision procedure with mean cup inclinations of 52.5 (SD 5.5, range 45–60) and 58 degrees respectively (SD 9.1, range 50–70)(p=0.255).

This original series of hip resurfacings, with up to 14 years follow up, shows a survival of 76% at the minimum follow up of 10 years. All failures were due to loosening of the smooth backed acetabulum, which with a modern porous coating, failure may have been avoided or delayed. Despite high inclinations angles no soft tissue reactions were identified within this series. No femoral failures were identified suggesting unlike much literature focus, long-term failure may not be related to the femoral head or neck.