Introduction. Short-stem hip arthroplasty is gaining popularity as a method of treating hip arthritis in biologically younger patients. The potential benefit of using a short-stem is preservation of bone in the proximal femur for a future revision. We have compared the early clinical and radiological results of a short-stem hip arthroplasty versus a conventional total hip arthroplasty (THA) using a standard length femoral prosthesis with particular focus on functional outcome. Methods. We evaluated a prospectively collected data on consecutive series of 249 patients, who underwent uncemented total hip arthroplasty at our institution. They were distributed into 2 groups: Group I, 125 patients received an uncemented short femoral stem (Mini Hip Arthroplasty (MHA), Corin, Cirencester) and Group II, 124 patients received a conventional uncemented femoral stem (Accolade, Stryker, Michigan) with mean follow up of 3.2 years (2–4). The characteristics of the two groups have been presented in Table I. Evaluation was based on plain radiographs performed at 6 months, 1 year and 2 years postoperatively, while their clinical status was assessed using the modified Harris hip score (mHHS) preoperatively and postoperatively at 6 weeks, 6 months, 1-year, 2-years and annually thereafter. Results. The outcome measures and complications in the two groups are presented in Table II. The mHHS was split into their two components (pain and function) to evaluate any differences between the groups. The postoperative results for pain were similar in both groups (p > 0.05), but the functional element of mHHS was significantly better (p < 0.05)* in Group I compared to Group II. This difference however did not reach the level of the minimum clinically important difference. All femoral stems showed radiographic evidence of bony ingrowth. No evidence of stem subsidence was found in any of the patients. One femoral implant was revised for infection in Group II. Conclusion. Our study suggests that the results of short-stem hip arthroplasty are comparable to conventional uncemented THA in the short-term. The functional outcome scores appear to be better in the short-stem group compared to the conventional group, but the difference is not clinically relevant. Short-stem hip arthroplasty can be an optimal choice for use in younger patients with good bone quality, who are expected to require revision in the future

To date, the literature has not yet revealed superiority of Minimally Invasive (MI) approaches over conventional techniques. We performed a systematic review to determine whether minimally invasive approaches are superior to conventional approaches in total hip arthroplasty for (1) clinical and (2) functional outcomes. We performed a meta-analysis of level 1 evidence to determine whether (3) minimally invasive approaches are superior to conventional approaches for clinical outcomes.

All studies comparing MI approaches to conventional approaches were eligible for analysis. The PRISMA guidelines were adhered to throughout this study. Registries were searched using the following MeSH terms: ‘minimally invasive’, ‘muscle-sparing’, ‘THA’, ‘THR’, ‘hip arthroplasty’ and ‘hip replacement’. Locations searched included PubMed, the Cochrane Library, ClinicalTrials.gov, the EU clinical trials register and the International Clinical Trials Registry Platform (World Health Organisation).

Twenty studies were identified. There were 1,282 MI THAs and 1,351 conventional THAs performed.

Intermuscular MI approaches are equivalent to conventional THA approaches when considering all-cause revision, aseptic revision, infection, dislocation, fracture rates and functional outcomes. Meta-analysis of level 1 evidence supports this claim.

Introduction

The incorporation of computer navigation in total hip arthroplasty (THA) has been much slower then for total knee arthroplasty (TKA). Computer navigation has proven itself in the realm of TKA but still has yet to advance in THA. The reasons for this include the lack of ease of incorporation, accuracy and precision, and the addition of overall operative time. Another reason for this lack of progress is that a majority of THA's are done with the patient in the lateral position through a posterior or lateral approach making the tracker placement and the registration process somewhat cumbersome. In the direct anterior approach the patient is in the supine position, which accommodates pelvic tracker placement and significantly facilitates the registration process. At our institution we use the direct anterior approach and computer navigation on all of our primary THA's. We hypothesized that computer navigation facilitates cup placement and leg length determination with out significantly increasing our operative time.

In this study we compare survivorship and patient reported outcome measures in robotically assisted versus conventional Total Hip Arthroplasty (THA). This paper investigates the hypothesis that implant survival and PROMS following THAs performed with robotic assistance were not different to outcomes following conventional THAs. Data included all patients undergoing THA for osteoarthritis between 19 April 2016 and 31 December 2020. Analysis of PROMS outcomes was restricted to those who had completed PROMS data preoperatively and at 6 months postoperatively. There were 157,647 procedures, including 3567 robotically assisted procedures, available for comparison of revision rates. 4557 procedures, including 130 robotically assisted procedures, had PROMS data available. The revision rate of primary THA performed with robotic assistance was not statistically different from THA performed by conventional methods (4 year cumulative percent revision 3.1% v 2.7%; HR = 1.05, p=0.67). The Oxford Hip Score, VAS for pain and the EQ-VAS score for overall health showed no statistically significant difference between the groups. The EQ-5D Utility Score showed an improved score (median score 1 v 0.88; OR = 1.58, p=0.007) for the robotically assisted group compared to the conventional group. Robotic assisted THA was not associated with significant improvement in early revision or joint-specific PROMs. The findings may have been biased, in either direction, by unmeasured patient, surgeon, hospital and prosthesis factors. The findings (including the difference in health-related quality of life) may have also been influenced by lack of blinding. Future research should include methods to minimise these biases

There has been a renewed interest in surface replacement arthroplasty over the last decade, with the hope and expectation that this procedure would provide an advantage over conventional total hip arthroplasty, especially in the young, active patient. More specifically, the promises of surface replacement arthroplasty have been: 1) preservation of bone stock so that future revisions would be easier, 2) potential to be minimally invasive in their approach, 3) better functional outcomes because of the stability associated with a larger femoral head with potential associated proprioceptive advantages, and 4) improved survivorship. Unfortunately, these promises have not been realised. Surface replacement arthroplasty does maintain more initial bone stock on the femur, but also tends to remove more bone initially on the acetabular side. Long term, it is the loss of acetabular bone stock that is more problematic from a reconstructive perspective. Further, the “simple” revision afforded in surface replacement arthroplasty has led to reports of inferior clinical outcomes, especially with respect to subjective complaints of pain. Surface replacement arthroplasty is more invasive than conventional total hip arthroplasty as the femoral head is maintained and the window to the acetabulum is subsequently partially blocked. This is exacerbated by the fact that many of these patients are young active males. There is no compelling evidence that surface replacement arthroplasty offers improved functional outcomes over conventional total hip arthroplasty, particularly when considering gait and proprioception. Some studies have in fact shown inferior outcomes. The concept of the larger femoral head in surface replacement arthroplasty providing increased range of motion and subsequent better function is flawed as it is the head-to-neck ratio that appears to be a more important determinant of outcome in this sense. Total hip arthroplasty generally has a more favorable ratio. Surface replacement arthroplasty has inferior survivorship to conventional total hip arthroplasty, even when accounting for the younger age of this patient cohort. This finding is consistent across multiple national joint replacement registries. The outcomes and survivorship are particularly poor in females, with many authors now advocating that the procedure be reserved for males. Surface replacement arthroplasty has introduced several new problems and mechanisms of failures, most concerning of which is the formation of pseudotumors in some patients. It is unclear as to who is at risk for this significant complication, and the ability to diagnose and treat this disorder is difficult and still in evolution. Likely associated is the significant elevation of metal ions in the serum and urine of some surface replacement arthroplasty patients. Neck fractures and loss of bone stock around the femoral implant have also been noted as problematic for these devices. Some of these problems have led to specific surface replacement arthroplasty systems being recalled. Finally, surface replacement arthroplasties are premium products with associated increased costs, which, frankly, are not justified

We report a rare case of Hip Resurfacing dislocation three years after a bilateral Hip Resurfacing in a very strong patient and show the maneuver to do a closed reduction on a film done at the surgical theatre under general anesthesia. Hip resurfacing dislocation is a very rare entity described in the literature and more rare after three years. With conventional total hip replacement the dislocation rate is 2–5%. In the international literature the dislocation rate with resurfacing is 0.21%. We describe a case of a 47 years old male patient who was submitted to a biltateral 54 × 60 mm Hip Resurfacing in November 16 th and 18th, 2011 (two separate days). He had a normal post op and returned to his work after six weeks and recreational activities after four months. Three years later, on November 8th, 2014 he did an extreme movement of hip flexion, adduction and internal rotation when he was gardening and planting a tree seedling suffering a left hip dislocation. Hopefully we could reduce the dislocated hip in a closed manner in the following morning. Patient went home next day but on that same night had important abominal pain needing to return to hospital when numerous gallbladder stones where found being submitted to a total laparoscopic colecistectomy two days later. It was really a bad luck week. Metal ions are still normal and patient is symptomless until today having returned to his recreational activities. We will show in a movie the maneuver to do this closed reduction and hope by showing this maneuver that our colleagues do not have to do an open dislocation in the future in case they face a Hip Resurfacing dislocation

The purpose of this study is to assess the accuracy of component positioning and incidence of peri-operative and 90-day post-operative complications following robotic arm-assisted and conventional total hip arthroplasty (THA). Three groups of patients were analyzed for this study: those that underwent conventional THA performed by Surgeon 1, conventional THA performed by Surgeon 2, or robotic arm-assisted THA performed by Surgeon 2. All patients underwent primary uncemented THA via a posterior approach. Patient characteristics, intra-operative data, and 90-day post-operative complications were collected. Post-operative standing pelvic radiographs were utilized to measure acetabular position and to identify post-operative complications. Acetabular component position measurements revealed substantially less variation in both inclination and anteversion in the Surgeon 2 – Robotic group. Nine patients had intra-operative cables placed for intra-operative calcar fracture in the Surgeon 1 group compared to one patient and three patients in Surgeon 2 – Robotic and Surgeon 2 – Traditional groups, respectively. Nine instances of femoral stems subsidence were identified in the Surgeon 1 group compared to one patient in Surgeon 2 – Traditional. There were four instances of dislocation in the Surgeon 1 group compared to one in the Surgeon 2 – Robotic group. Robotic arm-assisted THA decreases the variation in acetabular component positioning compared to conventional THA. However, the benefit of this is unclear as there is little difference in dislocation rate. This study may demonstrate additional value in CT-based implant planning as this cohort had the lowest incidence of femoral component complications

A conceptually new, to the North American market, acetabular design is currently available when performing a total hip arthroplasty – the dual mobility socket. Essentially this is a press-fit acetabular component with a polished surface (either modular or monoblock) that articulates with a large polyethylene head with a 28 mm ball inserted into that polyethylene in a similar fashion to a bipolar design. Proponents of this design advocate its use to reduce the risk of dislocation, and it is being offered as an alternative to constrained liners and also as a potential prophylactic application in revision and high risk patients. The concerns regarding this construct include:. Wear - A large polyethylene head articulating against a polished metal surface may have much greater wear than a conventional metal against polyethylene bearing. Hip simulator data has shown this previously. Additionally there are two articulating surfaces, potentially leading to a greater combined wear than one would see with just a singular surface. Clinical data - At present there are predominately short term published reports on this implant, many from the same centers. There are no control groups with other implants in these same “at risk” patients. There is no registry data to date on this implant. Patient Population - A difficult question to answer is which patient is at risk for dislocation and if one was going to apply this new technology, which patient would receive it? In the original published series, 26% of patients undergoing THA had this implant. Does the increased risk of wear and osteolysis warrant the use of this implant in a primary setting?. Unique complication - A unique complication has been described labeled intra-prosthetic dislocation. This occurs when the inner femoral ball disassociates from the polyethylene. The incidence has been reported up to 2% in some series. This complication alone equals the current rate of hip instability in a Medicare database with a conventional total hip replacement. Cost - In our current era of containing health care costs, this implant is offered to most at a significant cost premium to a more conventional total hip construct, without evidence of superiority, or for that matter equivalence at this point. There are many options available to both manage and to prevent hip instability. Any new implant must show equivalence to current devices on the many fronts of wear, fixation, mid-term results, complications and costs

Hip resurfacing offers an attractive alternative to conventional total hip arthroplasty in young active patients. It is particularly advantageous for bone preservation for future revisions. Articular Surface Replacement (ASR) is a hip resurfacing prosthesis manufactured by DePuy Orthopaedics Inc. (Warsaw, IN). The manufacturer voluntarily recalled the ASR system in 2010 after an increasing number of product failures. The present study aimed to determine the long-term results in a large cohort of patients who received the ASR prosthesis. Between February 2004 and August 2010, 592 consecutive hip resurfacings using the ASR (DePuy Orthopaedics Inc., Warsaw, IN) resurfacing implant were performed in 496 patients (391 males and 105 females). The mean age of the patients at the time of the surgery was 54 (range: 25 to 74) years. Osteoarthritis was the most common diagnosis in 575 hips (97.1%). The remaining patients (2.9%) developed secondary degenerative disease from ankylosing spondylitis, avascular necrosis, developmental hip dysplasia, and rheumatoid arthritis. Clinical and radiographic information was available for all patients at the last follow up. Cobalt (Co) and chromium (Cr) levels were measured in 265 patients (298 hips) by inductively coupled plasma-mass spectrometry (ICP-MS). The average follow up of the study was 8.6 years (range: 5.2 to 11.6 years). The mean Harris hip and UCLA scores significantly improved from 44 and 2 pre-operatively to 85.3 and 7.1 respectively. The median Co and Cr ion level was 3.81 microgram per liter and 2.15 microgram per liter respectively. Twenty-seven patients (5.4%) were found to have blood levels of both Co and Cr ions that were greater than 7 microgram per liter. Fifty-four patients (9.1%) were revised to a total hip arthroplasty. Kaplan-Meier survival analysis showed a survival rate of 87.1% at 8.6 years with revision for any cause and 87.9% if infection is removed. A significantly higher survival rate was observed for the male patients (90.2%, p <0.0001) and for the patients with ASRs with femoral heads diameters larger than 52 mm (90.1%, p=0.0003). This study confirms that patient selection criteria are of great importance to the overall survivorship of hip resurfacing arthroplasty. Improved clinical results have been reconfirmed with the use of larger diameter femoral heads

INTRODUCTION. THA as primary treatment for displaced femoral neck fractures in elderly still remains a prominent concern. Overall dislocation rate after total hip arthroplasty (THA) is reported form 1∼5%. But, it is quiet different in situation of femur neck fracture in elderly. The THA is associated with higher rates of dislocation (8%∼11%) in eldery compared to hemiarthroplasty even though THA showed better clinical and functional scores. Recently resurgence about THA using DMC comes after improvement of manufacturing technology. The aim of this prospective multicenter study is to assess the rates of dislocation and re-operation for displaced femoral neck fractures in elderly with THA with Dual Mobility Cup (DMC) and to review systematically comparison of previous reports. Up to our knowledge, this is first report from asian conutry about the clinical outcomes THA using DMC for displaced femur neck fracture in elderly. METHODS. Prospective consecutive groups of patients treated for displaced femoral neck fractures by three surgeons at each three center were included. 131 hips underwent THA with DMC for acute displaced femoral neck fracture in patients aged older than 70 years. Data regarding rates of dislocation and re-operation were obtained by review of medical records. Additionally From 2009 which the US FDA first approved the DMC, the authors searched reports regarding to THA using DMC for displaced femur neck fracture in elderly using the MEDLINE including cases series and comparative studies with bipolar hemiarthroplasty and THA. Therefore, current report was compared with previous reports. RESULTS. The reports about THA using DMC for displaced femur neck fracture in elderly were limited. Most of them comes from European countries. Comparative study with THA from Sweden reported the dislocation rate of THA using DMC with average aged 75-year is 0%. In Denmark study, the bipolar hemiarthroplasty showed 14% of dislocation rate for femur neck fracture in patient aged 75 years but, THA using DMC is 4.6%. Two cases series from French reported about 1–4% in patients aged 80 years. In our multicenter study, dislocation occurred in 6/131 hips (4.6%) treated with total hip arthroplasty using DMC for displaced femur neck fracture over 70 years older patients. Reoperations including periprosthetic fracture and fixation failure of cup were required in 1/43 (2.3%) hips treated with total hip arthroplasty using DM cup. These result is comparable to European reports. DISCUSSION AND CONCLUSION. Our findings indicate that THA with DMC can not guarantee to prevent the dislocation for high risk elderly patients, but the overall rate of dislocation can be comparable to those of bipolar hemiarthroplasty and reduced compared to conventional total hip arthroplasty. This result might be a valuable messages for burden of the medical cost by dislocation after arthroplasty especially for older patient. Therefore, adding advnatages of THA compared with hemiarthroplasty, the THA with DMC can be a wise option for displaced femoral neck fracture in eldely. But, the randomized controlled study still is needed to clarify to confirm this findings

BACKGROUND. We originally performed metal-on-metal hip resurfacing using a Townley designed Vitallium Total Articular Replacement Arthroplasty (TARA) curved stemmed prosthesis. Neither the acetabular or femoral components were cemented or had porous coating. The bearing surfaces were consistently polar bearing. The surgical objectives were to preserve bone stock, maintain normal anatomy and mechanics of the hip joint and to approximate the normal stress transmission to the supporting femoral bone. The functional objectives were better sports participation, less thigh pain and limp, less perception of a leg length difference and a greater perception of a normal hip. Metal-on-metal was selected to conserve acetabular bone and avoid polyethylene associated osteolysis. Relatively few cases were performed until the Conserve Plus and later the Birmingham Hip Resurfacing systems became available. METHODS. We examined the results of metal-on-metal hip resurfacing in patient with at least 10 years of follow-up and an age less than 50 at the time of surgery. We did not have access to the Birmingham Prosthesis until 2006. We performed 101 TARA procedures and 397 Conserve Plus procedures for 357 patients. For the combined series the mean age was 43 and 62% of patients were male. 34 patients had a conventional total hip replacement on the contralateral side. We used both the anterolateral and posterior approaches. All acetabular components were placed without cement and all the Conserve Plus Femoral Components were cemented. RESULTS. There were no implant related failures with the TARA prosthesis. The average Harris Hip Score was 93. There were 2 revisions for femoral neck fracture at years 8 and 14 and one revision for infection. There was one dislocation but no instance of implant loosening. There were 29 (7%) revisions with the Conserve Plus Prosthesis. 14 revisions were for adverse reactions to metal wear debris and 10 of these patients had femoral components of size 46 mm or smaller. There were 5 revisions for acetabular loosening and 3 for femoral loosening. There were 7 revisions for femoral neck fracture and infection. The limb lengths were measured to be within 1 cm of equal in 98% of patients. 95% of patients had a UCLA activity score above 6 and 96% of patients rated their outcome excellent or good. 32 of 34 patients preferred their hip resurfacing to total hip replacement. The Kaplan-Meier survivorship was 93%. Narrowing of the femoral neck was seen in 9% of patients but acetabular osteolysis was not seen. Signs of impingement of the femoral neck against the acetabular prosthesis were seen in 14% of patients. CONCLUSIONS. Metal-on-metal hip resurfacing has been performed for more than 40 years using predicate prostheses such as the Townley TARA. The results of metal-on-metal resurfacing are favorable even in young and very active individuals. There were no instances of medical illness related to metal-on-metal implants with up to 41 years of follow-up. Metal-on-metal hip resurfacing has favorable outcomes at 10 years. There is an increased chance of an adverse reaction to metal wear debris with femoral component sizes 46 mm or smaller

Introduction. Bearing surfaces used for total hip arthroplasty must have characteristics including bio-compatibility, low friction and low wear rate. Bearing combinations are generally characterised as Soft on Hard/Hard. In general, all newer bearing combinations have reduced wear but may present with other issues that impact on patient outcomes. Materials. The Australian Orthopaedic Association – National Joint Replacement Registry classifies bearing surfaces into six categories. These are metal on polyethylene, ceramic on polyethylene, metal on metal, ceramic on ceramic, ceramic on metal and a sixth category relating to a small number of procedures where the bearing surface is yet to be classified. 147,422 conventional total hip arthroplasty procedures have been recorded by the Registry between 1 September 1999 and 31 December 2008 and analysis has been performed of the cumulative percentage revision in relation to bearing surface. Results. In general, metal on polyethylene has the lowest risk of revision compared to all other bearing surfaces and metal on metal has the highest revision rate. The risk of revision, however, does vary depending on head size, with larger head sizes having a lower risk of revision with the exception of metal on metal. Conclusion. When deciding which bearing surface is suitable for patients it must be emphasised that wear reduction is only one of several considerations when choosing the most appropriate combination

Purpose. There are some concerns about doing hip resurfacing arthroplasty in ONFH due to bone defect which can cause mechanical weakness of femoral component and highly active young age of patients which can cause high wear rate and failure rate. The purpose of this study is to verify the HRA is safe procedure in ONFH in the aspect of mechanical and biological issue. Materials and Methods. Between December 1998 and May 2005, 185 hips of 169 patients underwent MoM HRA using Birmingham Hip Resurfacing System® at single center. 166 hips (26 hips of female, 140 hips of male) of 144 patients have been reviewed for at least 7 years after MoM HRA. Mean follow-up period was 101.8 (84–178) months. Their mean age at the time of operation was 37.7(16–67) years old. Clinically, Harris hip scores (HHS), UCLA activity scores and range of motion were evaluated. Radiologically, the extent of necrotic area in preoperative MRI and radiolucency around implants, narrowing of retained neck, impingement, stress shielding, and heterotopic ossification were evaluated in the serial anteroposterior and groin lateral radiographs of hip. Complications were defined as joint dislocation, infection, implant loosening, femoral neck fracture and pseudotumor. Failure was defined as revision arthroplasty due to the complications. Results. The extent of necrotic area in preoperative MRI was average 37.6 (13.3–65)%. Clinically, average HHS was improved from 81.7 points to 98.5 points at last follow-up. Average UCLA activity score at last follow-up was 9.0 points. Range of motion at last follow-up was very satisfactory. There was no patient with severe pain around hip joint. Radiologically, radiolucency was shown around acetabular component in 2 cases (1.2%) and around stem of femoral components in 3 cases (1.8%). Fracture of femoral neck was seen in 1 case(0.6%). Moderate narrowing changes of retained femoral neck were noticed in 4 cases (2.4%). Impingement was seen in 12 cases (7.2%). We found only 1 case of osteolysis at Gruen zone III of acetabulum. Heterotopic ossification was found in 5 cases (3.0%). There was no case with hip dislocation, infection or pseudotumor. Revision surgeries after the primary resurfacing arthroplasty were performed in 4 cases (2.4%). Three hips were revised to the conventional total hip arthroplasty (THA) because of loosening of acetabular component and femur neck fracture. One case of femoral component loosening was revised to THA using big metal head with retained acetabular component. Conclusions. MoM HRA in ONFH demonstrates good survivorship in average 101.8 months follow-up study. Most of patients show excellent clinical results with high level of activity postoperatively. Prevalence of complications is extremely lower than concern including the allergic reaction to the metal ion. There was no mechanical failure related to bone defect due to ONFH. This results suggests that MoM HRA in ONFH less than 50% of extent of necrosis can be justified

Metal-on-Metal devices generate significantly lower volumetric wear than conventional total hip replacements. However, clinically some patients may suffer some form of laxity in their joints leading to subluxation of the joint, which in turn may cause edge loading of an implant thereby increasing the chances of failure due to higher than expected wear. In this study, the effect of subluxation on MoM implant wear was investigated on a hip joint simulator. Materials & Methods. Two groups of 44 mm MoM devices were tested, n=3 in each group. The devices were subjected to 1 and 2 mm of subluxation. The flexion/extension was 30° and 15° respectively, internal/external rotation was ±10°, and cup inclination was 35°. The force was Paul type stance phase loading with a maximum load of 3 kN, with ISO swing phase load of 0.3 kN, run at 1 Hz. The test was carried out on a ProSim deep flexion & subluxation hip wear simulator (SimSol, UK). Rather than separating the head and the cup (microseparation), or reducing the swing phase load, this simulator is equipped with a novel mechanism to achieve translation of the head, while subjecting the devices to subluxation. During the swing phase, a controlled lateral force necessary for the translation of the head is applied by a cam mechanism, head retraction will then take place on heel strike. The lubricant used was new born calf serum with 0.2 wt. % sodium azide concentration diluted with de-ionised water to achieve average protein concentration of 20 g/l. Lubricant was changed every 250k cycles. Gravimetric wear measurements have been taken at 0.25 & 0.5 Mc stages. Results. Tests conducted with 1mm (Group 1) and 2mm (Group 2) subluxation significantly increased volumetric wear compared to standard hip simulator tests [1]. At 0.5 million cycles, group 1 and 2 produced an average volume loss of 4.38±0.98 mm. 3. (95% CL) and 7.07±1.64 mm. 3. (95% CL) respectively. Discussion/conclusion. Well positioned and well-fixed hip implants perform well in vitro and in vivo; however optimal performance a device can be affected by a number of factors from design, technical factors, patient factors, surgical technique to position of the device in vivo. The study presents test results of a hip joint simulator with a subluxation mechanism to simulate clinically relevant subluxation during the swing phase of a gait cycle under the ISO swing phase load of 0.3kN, with differing levels of luxation. Increasing the level of subluxation in turn increased volumetric wear due to greater head contact at the superior rim of the cup. Further tests will be conducted with high cup inclination angles (>45°) and subluxation to determine the effect upon wear. Tests which can simulate the (ideal and adverse) conditions clinically can help to improve the design and understanding of implant behaviour in vivo

Background and aim. Arthroplasty registries and consecutive series indicate significantly worse results of conventional metal-on-polyethylene total hip arthroplasty (THA) in patients younger than 50 years compared to older patients, with inferior clinical outcomes and 10-year survivorship ranging between 70 and 90%. At our institution, patients under 50 needing a THA receive either a metal-on-metal hip resurfacing (MoMHRA) or a ceramic-on-ceramic (CoC)THA. In order to evaluate the outcome of these options at minimum 10 years, we conducted a retrospective review of all MoMHRA and CoCTHA with more than 10 years follow-up implanted in patients under 50. Methods. From a single surgeon patients’ prospective database, we identified all consecutive THA performed before May 2005 in patients under 50. All patients are contacted by phone and asked to present for a clinical exam and patient reported outcome questionnaires, standard radiographs and metal ion measurements unless the hip arthroplasty has been revised. Complications and reasons for revision are noted. Kaplan-Meier survivorship is analysed for the whole cohort and sub-analysis is performed by type hip arthroplasty, gender, diagnosis and component size. Results. We identified 773 hip arthroplasties in 684 patients under 50 years performed by a single surgeon between 1997 and May 2005. There are 626 MoMHRA, all Birmingham Hip Resurfacings (BHR) in 561 patients (65 bilateral BHR), 135 CoCTHA in 111 patients (24 bilateral CoC) and 12 Metasul MoMTHA in 12 patients. In the BHR group, there are 392 males (70%) (42 bilateral) and 169 females (30%) (23 bilateral). Mean age at surgery was 40.8 years (median 42 years; range 16–50 years). In 33 cases, a BHR dysplasia cup was used (23 in females). Mean follow-up is 11.5 years (median 11 years; range 10–17 years). In the Metasul MoMTHA, there are 8 males and 4 females. Mean age at surgery was 40.4 years (range 20–50 years). All THA were non-cemented and head size was 28mm in all cases. Mean follow-up is 16.8 years (median 17.5 years; range 12–19 years). In the CoCTHA group, there are 71 males (64%) (17 bilateral) and 40 females (36%) (7 bilateral). Mean age at surgery was 38.2 years (median 39 years; range 16–50 years). In 21 cases, the CoCTHA was a revision of a former hip replacement: 15 THA revisions and 6 hip resurfacing revisions. Three types non-cemented acetabular components were used and 7 types femoral stems (5 non-cemented; 2 cemented). Ceramic heads and inlays were Biolox forte in 128 cases and Biolox delta in 7. Head size was 28mm in 125, 32mm in 7 and 36mm in 3. Mean follow-up is 14.9 years (median 15 years; range 10–18 years). Discussion. Patients under 50 needing a hip arthroplasty often present with more complex anatomic abnormalities or bone damage as in congenital dysplasia, avascular necrosis, traumatic osteoarthritis or rheumatic diseases. Besides, the worse results with conventional THA in young patients may be related to a higher activity level. We present the outcome and survivorship of MoMHRA and CoCTHA in patients under 50 at more than 10 years postop