Background. High functional aspirations and an active ageing population equate to a growing number of patients awaiting hip arthroplasty demanding superior biomechanical function. The purpose of this study was to compare the biomechanics of top walking speed between two commonly used hip arthroplasty procedures to determine if a performance advantage existed. Methods. A retrospective comparative study was performed using sixty-seven subjects, twenty-two subjects in both hip resurfacing and total hip arthroplasty groups along with twenty-three healthy controls. All arthroplasty subjects were recruited based on high psychometric scoring and had been performed through a posterior approach, and had been discharged from follow-up. On an instrumented treadmill each subject was measured by a researcher blinded to which procedure that patient had undergone. After a six minute acclimatization period, the speed was increased incrementally until top walking performance had been attained. At all increments, ground reaction forces and temporospatial measurements were collected. Results. The two arthroplasty groups were well matched demographically, with no significant differences with regards to age, sex, height, BMI and pre-operative radiological severity. Treadmill temporospatial analysis demonstrated significant differences between the two groups. The hip resurfacing group were able to walk statistically faster (p=0.023) with an increased step length(p=0.041). The top walking speed mean of 2.06m/sec by the resurfacing almost matched the healthy controls. Assessing ground reaction forces and symmetry also demonstrated hip resurfacing was superior (Graph 1). [Graph 1: Mean Gait Biomechanics at Top Speed]. Conclusion. This study is the first to focus on high end performance following hip arthroplasty, encouraging patients to achieve as high a speed as they comfortably could. The total hip arthroplasty group walked nine percent faster than the previously published top speed of 1.73m/sec, however the resurfacings still walked ten percent faster, matching the normal controls for speed and step length

Metal on Metal hip resurfacing (MoM HR) can be an effective operation for the young arthritic hip population. However, errors in cup orientation have been associated with increased wear, circulating blood metal ions, and soft tissue abnormalities that can lead to premature failure of the bearing surface and subsequent revision surgery. While image free computer guidance has been shown to increase surgical accuracy in total hip arthroplasty, the role of image based technology in MoM HR is unclear. In this study, we compared the accuracy of cup orientation in MoM HR performed by either freehand technique or CT based navigation. Seventy five patients (81 hips) underwent either freehand (n=42) or navigation (n=39) surgery, both requiring a three dimensional (3D) CT surgical plan. Surgery was conducted by hip specialists blind to the method of cup implantation until the operation. Deviation in inclination and version from the planned orientation, as well as, number of cups within a 10° safe zone and 5° optimal zone of the target position was calculated using post operative 3D CT analysis. Error in inclination was significantly reduced with navigation compared to freehand technique (4° vs 6°, p=0.02). We could not detect a difference between the two groups for version error (5° vs 7°, p=0.06). There was a significantly greater number of hips within a 10° (87% vs 67%, p=0.04) and 5° (50% vs 20%, p=0.06) safe zone when navigated. Image based navigation can substantially improve accuracy in cup orientation. The results of our freehand group appear better than historic controls, suggesting the use of a 3D plan may help to reduce technical error and improve the learning curve in this technically demanding procedure. We advocate the use of image based navigation in MoM hip resurfacing arthroplasty

Background. We have previously described the relationship between wear rates of MOM components and soft tissue necrosis. In this study we investigated the link between wear rates, metal ion concentrations and osteolysis. Methods. All unilateral patients who underwent revision of hip resurfacings at our centre were included. Retrieved components were analysed using a coordinate measuring machine to determine total volumetric material loss and rates of wear. Given the accuracy of the wear calculations (which we have previously published), wear rates were considered “abnormal” if ≥3mm. 3. /yr. ROC curves were constructed to determine a Co concentration which would be clinically useful to detect abnormal wear. During revision, the presence/absence of osteolysis was documented. Results. There were 65 patients in total (mean time to revision was 41 months (2 to 98). 60 patients had suffered ARMD. 2 hips were revised for infection, 1 for osteolysis and 1 due to a loose cup and 1 for unexplained pain. A blood cobalt concentration >5µg/l was found to be 100%(62.2–100) specific and 94.4%(84.2–98.6) sensitive for the detection of abnormal wear. All patients with wear rates greater than 12mm. 3. /yr (n=21) were found to have osteolysis (the minimum total loss of material in this group of patients was 16mm3). ROC analysis showed that a blood cobalt ≥44.6µg/l was 97.2% specific for the detection of this rate of wear. 3 of the 21 patients with these rates of wear were asymptomatic. They decided on revision after discussion with the surgeon. Two were revised following acute femoral collapse but were completely pain free prior to these events. Conclusion. These data suggest that a blood cobalt concentration of 5µg/l can reliably identify an abnormally wearing resurfacing prosthesis. Elevated metal ion concentrations are associated with osteolysis, even in the absence of symptoms

Introduction. Metal on metal hip resurfacing arthroplasty (MoM HR) has the highest revision rates according to the UK National Joint Registry. Revisions for lesions associated with soft tissue necrosis (pseudotumors) have been associated with poor outcomes. There is a relative paucity of information on early revision of painful HR prostheses. We present the results of a series of patients who underwent early revision of painful MoM HR procedures. Methods. This prospective study involved a consecutive series of patients undergoing revision of HR to THA. The diagnoses leading to revision are discussed. Clinical and radiological assessments were performed pre operatively as well as 6 weeks, 12 months postoperatively and yearly thereafter. Pre and post operative Harris Hip Score, Oxford Hip Score and WOMAC scores were calculated. Patient satisfaction was assessed using a visual analogue scale. Results. Revisions were performed for recurrent pain and effusion, infection and proximal femoral fractures. Both components were revised in 20 cases. There were 12 male and 13 female patients with average time to revision of 34.4 and 26.4 months respectively. The mean follow up period was 12.7 months (3 to 31). All patients reported relief of pain and excellent satisfaction scores (9/10 compared to 2/10 pre-operatively). Two patients experienced stiffness up to three months post operatively. Pre operative Oxford, Harris and WOMAC hip scores were 39.1, 36.4 and 52.2 respectively. Mean post operative scores at last follow up were 17.4, 89.8 and 6.1 respectively (p< 0.0001 for each score). All patients except those with femoral neck fractures had at least a small effusion. Conclusion. These results show that conversion of painful hip resurfacing prostheses to total hip arthroplasty is associated with improved function, pain relief and high levels of patient satisfaction

Hip resurfacing may be a useful surgical procedure when patient selection is correct and only implants with superior performance are used. In order to establish a body of evidence in relation to hip resurfacing, pseudotumour formation and its genetic predisposition, we performed a case-control study investigating the role of HLA genotype in the development of pseudotumour around MoM hip resurfacings. All metal-on-metal (MoM) hip resurfacings performed in the history of the institution were assessed. A total of 392 hip resurfacings were performed by 12 surgeons between February 1st 2005 and October 31st 2007. In all cases, pseudotumour was confirmed in the preoperative setting on Metal Artefact Reduction Sequencing (MARS) MRI. Controls were matched by implant (ASR or BHR) and absence of pseudotumour was confirmed on MRI. Blood samples from all cases and controls underwent genetic analysis using Next Generation Sequencing (NGS) assessing for the following alleles of 11 HLA loci (A, B, C, DRB1, DRB3/4/5, DQA1, DQB1, DPB1, DPA1). Statistical significance was determined using a Fisher's exact test or Chi-Squared test given the small sample size to quantify the clinical association between HLA genotype and the need for revision surgery due to pseudotumour. Both groups were matched for implant type (55% ASR, 45% BHR in both the case and control groups). According to the ALVAL histological classification described by Kurmis et al., the majority of cases (63%, n=10) were found to have group 2 histological findings. Four cases (25%) had group 3 histological findings and 2 (12%) patients had group 4 findings. Of the 11 HLA loci analysed, 2 were significantly associated with a higher risk of pseudotumour formation (DQB1*05:03:01 and DRB1*14:54:01) and 4 were noted to be protective against pseudotumour formation (DQA1*03:01:01, DRB1*04:04:01, C*01:02:01, B*27:05:02). These findings further develop the knowledge base around specific HLA genotypes and their role in the development of pseudotumour formation in MoM hip resurfacing. Specifically, the two alleles at higher risk of pseudotumour formation (DQB1*05:03:01 and DRB1*14:54:01) in MoM hip resurfacing should be noted, particularly as patient-specific genotype-dependent surgical treatments continue to develop in the future

Background. Proper positioning of the acetabular component is critical for prevention of dislocation and excessive wear for total hip arthroplasty (THA) and hip resurfacing. Consideration of preoperative pelvic tilt (PT) may aid in acetabular component placement. The purpose of this study was to investigate how PT changes after hip resurfacing, via pre and post-operative radiographic analysis of anterior pelvic plane (APP), and whether radiographic analysis of the APP is a reproducible method for evaluating PT in resurfaced hips. Methods. A consecutive group of 228 patients from a single surgeon who had hip resurfacing were evaluated. We obtained x-rays from an institutional database for these patients who had their surgeries between January 1. st. , 2014 to December 31. st. , 2016. Pelvic tilt (PT) was measured by two observers before and after resurfacing utilizing a standardized radiographic technique. Correlation coefficients were calculated for PT measurements between observers, and pre- and post-surgery. Results. Mean preoperative PT was 0.7° (SD ± 6.6°) and 0.4° (SD ± 6.1°). Mean post-operative PT was −1.2° (SD ± 6.2°) and −1.2° (SD ± 6.0°). Correlations between pre and post-operative PT were R=.829 (p<.001) and R = .837 (p<.001). 80.6% to 82.5% of patients had variation <5°, 15.8% to 17.8% had variation between 5–10°, and 1.6 to1.8% had a variation >10°. Intraclass correlation coefficients between observers were R = .987 (95% CI, .963–.981; p<.001) preoperatively, and R=.985 (95 CI, .963–.981; p<.001) postoperatively. (See Fig 1). Conclusion. After hip resurfacing arthroplasty, the mean difference between preoperative and postoperative PT was less than 1°. These results suggest that near-native PT is maintained with consistency after hip resurfacing, a finding that is variable following THA. Since variations in PT affect functional acetabular position, these results support the use of pelvic tilt measurement in pre-operative planning for hip arthroplasty with a high degree of inter-observer reliability. For any figures or tables, please contact the authors directly

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

Navigation in total hip arthroplasty has been shown to improve acetabular positioning and can decrease the incidence of mal-positioned acetabular components. The aim of this study was to assess two surgical guidance systems by comparing intra-operative measurements of acetabular component inclination and anteversion with a post-operative CT scan. We prospectively collected intra-operative navigation data from 102 hips receiving conventional THA or hip resurfacing arthroplasty through either a direct anterior or posterior approach. Two guidance systems were used simultaneously: an inertial navigation system (INS) and optical navigation system (ONS). Acetabular component anteversion and inclination was measured on a post-operative CT. The average age of the patients was 64 years (range: 24-92) and average BMI was 27 kg/m. 2. (range 19-38). 52% had hip surgery through an anterior approach. 98% of the INS measurements and 88% of the ONS measurements were within 10° of the CT measurements. The mean (and standard deviation) of the absolute difference between the post-operative CT and the intra-operative measurements for inclination and anteversion were 3.0° (2.8) and 4.5° (3.2) respectively for the ONS, along with 2.1° (2.3) and 2.4° (2.1) respectively for the INS. There was significantly lower mean absolute difference to CT for the INS when compared to ONS in both anteversion (p<0.001) and inclination (p=0.02). Both types of navigation produced reliable and reproducible acetabular cup positioning. It is important that patient-specific planning and navigation are used together to ensure that surgeons are targeting the optimal acetabular cup position. This assistance with cup positioning can provide benefits over free-hand techniques, especially in patients with an altered acetabular structure or extensive acetabular bone loss. In conclusion, both ONS and INS allowed for adequate acetabular positioning as measured on postoperative CT, and thus provide reliable intraoperative feedback for optimal acetabular component placement

Hip resurfacing arthroplasty (HRA) is a bone conserving alternative to total hip arthroplasty. We present the early 1 and 2-year clinical and radiographical follow-up of a novel ceramic-on-ceramic (CoC) HRA in a multi-centric Australian cohort. Patient undergoing HRA between September 2018 and April 2021 were prospectively included. Patient-reported outcome measures (PROMS) in the form of the Forgotten Joint Score (FJS), HOOS Jr, WOMAC, Oxford Hip Score (OHS) and UCLA Activity Score were collected preoperatively and at 1- and 2-years post-operation. Serial radiographs were assessed for migration, component alignment, evidence of osteolysis/loosening and heterotopic ossification formation. 209 patients were identified of which 106 reached 2-year follow-up. Of these, 187 completed PROMS at 1 year and 90 at 2 years. There was significant improvement in HOOS (p< 0.001) and OHS (p< 0.001) between the pre-operative, 1-year and 2-years outcomes. Patients also reported improved pain (p<0.001), function (p<0.001) and reduced stiffness (p<0.001) as measured by the WOMAC score. Patients had improved activity scores on the UCLA Active Score (p<0.001) with 53% reporting return to impact activity at 2 years. FJS at 1 and 2-years were not significantly different (p=0.38). There was no migration, osteolysis or loosening of any of the implants. The mean acetabular cup inclination angle was 41.3° and the femoral component shaft angle was 137°. No fractures were reported over the 2-year follow-up with only 1 patient reporting a sciatic nerve palsy. There was early return to impact activities in more than half our patients at 2 years with no early clinical or radiological complications related to the implant. Longer term follow-up with increased patient numbers are required to restore surgeon confidence in HRA and expand the use of this novel product. In conclusion, CoC resurfacing at 2-years post-operation demonstrate promising results with satisfactory outcomes in all recorded PROMS

Background. Since the development of modern total hip replacement (THR) more than 50 years ago, thousands of devices have been developed in attempt to improve patient outcomes and prolong implant survival. Modern THR devices are often broadly classified according to their method of fixation; cemented, uncemented or hybrid (typically an uncemented acetabular component with a cemented stem). Due to early failures of THR in young active patients, the concept of hip resurfacing was revisited in the 1990's and numerous prostheses were developed to serve this patient cohort, some with excellent clinical results. Experience with metal-on-metal (MoM) bearing related issues particularly involving the ASR (DePuy Synthes, Warsaw, Indiana) precipitated a fall in the use of hip resurfacing (HR) prostheses in Australia from a peak of 30.2% in 2004 to 4.3% in 2015. The effects of poorly performing prostheses and what is now recognised as suboptimal patient selection are reflected in the AOANJRR cumulative percent revision (CPR) data which demonstrates 13.2% revision at 15 years for all resurfacing hip replacements combined; with 11 different types of hip resurfacing prostheses recorded for patients less than 55 years of age and a primary diagnosis of OA. When this data is restricted to only those prostheses currently used in Australia (BHR; Smith and Nephew, Birmingham, UK & ADEPT; MatOrtho Ltd, Surrey, UK) there is a CPR of 9.5% at 15 years for all patients. Despite these CPR results, recognition is emerging of the important distinction between MoM THR and resurfacing. Furthermore, in light of current consensus for patient selection and the surgical indications for resurfacing, a gender analysis demonstrates a CPR for females of 14.5% at 10 years compared to 3.7% for males. Similar difference for head size >50mm with 6% CPR at 10 years compared to 17.6% for head size <50mm (HR=2.15; 1.76, 2.63; p<0.001). Leading to renewed interest in resurfacing particularly in the young, active male. In addition to registry based CPR data, several studies have concluded that a true difference in mortality rates between HR and other forms of THR exists independent of age, sex or other confounding factors. We hypothesised that a difference in adjusted mortality rates between HR and other forms of THR may also be present in the Australian population. We undertook an ad hoc data report request to the AOANJRR. The data set provided was deidentified for patient, surgeon and institution and included all HR and conventional THR procedures performed for the diagnosis of primary osteoarthritis recorded in the Registry since inception in 1999. We requested mortality and yearly cumulative percent survival (CPS) of patients for primary HR and THR with sub-group analysis by the mode of fixation. There were 12,910 hip resurfacings (79% male) compared to 234,484 conventional THR (46.8% male) over the study period. When adjusted for age and gender over the 15 years of available data, there was a statistically significant difference in cumulative percent survival (CPS) between conventional THR and hip resurfacing (HR 1.66 (1.52, 1.82; p<0.001)) and between cemented THR and hip resurfacing (HR 1.96 (1.78, 2.43; p<0.001)); between uncemented THR and hip resurfacing (HR 1.58 (1.45, 1.73; p<0.001)); and between hybrid THR and hip resurfacing (HR 1.82 (1.66, 1.99; p<0.001)). When adjusted for age, gender and ASA over the 3 years data available, there was no statistically significant difference in CPS between hip resurfacing and any individual fixation type of THR. Discussion. The results demonstrate a statistically significant adjusted survival advantage for hip resurfacing compared to conventional THR and between fixation methods for THR. These findings are consistent with previous studies. While a difference in adjusted mortality rate appears to exist, we are yet to definitively determine the complex interplay of causative factors that may contribute to it

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

Introduction. Patients who undergo hip resurfacing, total hip arthroplasty (THA), and total knee arthroplasty (TKA) are frequently assessed post-operatively using objective scoring indices. A small yet significant percentage of these patients report specific unfulfilled functions following surgery, indicating unmet expectations. The purpose of this study was to examine the types of functional deficits reported for each class of surgery, how frequently these limitations occur, and the demographic of patients who experience/report these limitations. Methods. Four groups of subjects were enrolled in this study: (i) 111 hip resurfacing patients at an average of 14 months after resurfacing, (ii) 170 patients at an average of 16 months post-primary THA, (iii) 61 patients at an average of 12 months post-primary TKA, and (iv) 64 control subjects with no history of hip or knee surgery or pathology. Each participant completed a self-administered Hip Function Questionnaire, Knee Function Questionnaire, or Hip Resurfacing Questionnaire which assessed each subject's overall satisfaction and expectations following surgery. The questionnaires included numerical scores of post-operative function as well as an open-ended question which inquired “Is there anything your knee/hip keeps you from doing?”. Results. A population of patients self-reported specific functional deficits after surgery, including 29 (26.1%) resurfacing, 5 (2.9%) THA, and 32 (52.5%) TKA. The unfulfilled functions varied based on the procedure, with most resurfacing and THA patients reporting trouble with running/jogging, while TKA patients experienced difficulty kneeling. Patients who reported functional deficits also tended to endorse lower overall satisfaction levels after surgery; the mean satisfaction score for hip resurfacing in those who reported deficits was 4.03 (scale of 1–5) versus 4.50 (p=0.09) in those who denied a functional deficit, 2.20 versus 4.47 (p=0.003) in THA patients, and 4.10 versus 4.36 (p=0.35) in TKA patients. The demographic of patients who reported limitations varied based on the type of surgery. After hip resurfacing 19.0% (4/21) of female patients reported specific deficits compared to 27.3% (23/84) of male patients; 6.1% (5/81) of female THA patients reported compared to 0% (0/84) of males, and 48.6% (18/37) of female TKA patients reported compared to 58.3% (14/24) of males. The mean age of those who reported deficits versus those who did not report deficits was not significant. Conclusions. Despite advances in arthroplasty and resurfacing techniques, a significant portion of patients are experiencing functional limitations following hip resurfacing, TKA, and THA procedures. The frequency and types of limitations reported vary based on the surgery, with TKA patients reporting deficits with the highest frequency and THA patients reporting with the lowest frequency. The gender of the patient appears to play a role in whether specific functional deficits are reported or not, with female patients more likely to report after THA and male patients slightly more likely to report after either hip resurfacing or TKA. Summary. A small portion of hip resurfacing, THA, and TKA patients report specific unfulfilled functions following surgery. The frequency and types of deficits, and the demographic of patients reporting them, varies based on the procedure

INTRODUCTION. The cup component of modern resurfacing systems are often coated creating a cementless press-fit fixation in the acetabulum based on surgical under-reaming, also enabling osseoconduction/integration. Due to the higher density of cortical bone along the antero-superior and postero-inferior regions of the acetabulum, the greatest forces occur between the anterior and posterior columns of the pelvis. This produces pinching of the implant that can result in deformation of the cup. Metal shell/modularpress-fit acetabular cups are susceptible to substantial deformation immediately after implantation. This deformation may affect the lubrication, producing point loading and high friction torques between the head and the cup that increase wear and may lead to head clamping and subsequent cup loosening. We sought to test a novel ceramic on ceramic (CoC) hip resurfacing system that should allay any concerns with the Adverse Reaction to Metal Debris associated with metal on metal (MoM) resurfacing devices. AIM. We sought to quantify the deformation of a novel CoC hip-resurfacing cup after implantation, using a standard surgical technique in a cadaveric model, and compare to the MoM standard. We also assessed if the design clearances proposed for this CoC hip resurfacing implant are compatible with the measured deformations, allowing for an adequate motion of the joint. METHODS. The pelvis from four fresh frozen cadavers were placed into the lateral position. One surgeon with extensive experience in hip resurfacing surgery (JH) prepared all the pelvises for implantation using a posterior approach to the joint and sequential reaming of the acetabulum to 1mm below the implant outer diameter. The acetabulum components were then impacted into the prepared pelvis. We used four ceramic and four metal implants of equal and varying size. (2 × (40/46mm, 44/50mm, 50/56mm, 52/58mm)). The acetabulum cup bearing surface diameter and deformation was measured using a GOM-ATOS optical high precision 3D scanner. 3-Dimensional measurements were taken pre-implantation, immediately after and at 30 minutes following implantation. Two techniques were used to analyse the 3D images: by maximum inscribed diameter and by radial segments. These were compared to the known articulating surface clearance values. RESULTS. The diameter of the cups in both metal and ceramic systems was reduced after implantation when analysing by maximum inscribed diameter and by radial segments. This deformation was maintained at 30 minutes. We can infer there is no significant bone stress relaxation effect following implantation. On ceramic cups, the deformation was larger in larger sizes. However, the 44/50 (the second smallest cup) deformed the least. Despite this, the difference in deformation between these two sizes is minimal. The deformation of sizes 50/56 and 52/58 was equivalent. For the metal cups, there was not a clear correlation between the cup size and the deformation. The largest cup size had the same deformation as the smallest size. CONCLUSIONS. The deformation following implantation of the cup component in a ceramic acetabulum resurfacing behave similarly to a metal implant. Cup deformation measured after implantation is minimal when compared to the minimum design clearance in both systems

INTRODUCTION. Experience with Metal on Metal (MoM) hip resurfacing devices has shown adequate cementation of the femoral head is critical for implant survival. Bone necrosis can be caused by the temperature change in the peri-prosthetic bone whilst the cement cures during implantation. This can lead to implant loosening, head/neck fracture and implant failure. During the implantation it is known that implants change shape potentially altering joint clearance and causing loosening. Given the history of Metal on Metal implant failure due adverse tissue reactions from Cobalt and Chromium particles we sought to test a novel Ceramic on Ceramic (CoC) bearing which may mitigate such problems. AIM. We set out to compare the behaviour of a novel ceramic femoral head component to a standard metal component in a hip resurfacing system after cemented implantation in a physiological warmed cadaveric model. Our first aim was to perform heat transfer analysis: To document time to, and extent of, maximum temperature change on the metal/ceramic surface and inside the resurfaced femoral head bone. Our second aim was to perform a dimensional analysis: To document any resulting deformation in the metal/ceramic femoral head bearing diameter during cementation. METHODS. Femurs were removed from four fresh frozen cadavers and placed into a vice. One surgeon with extensive experience in hip resurfacing surgery (JH) prepared all the femoral heads for implantation. Cadaveric warming was performed using a thermostatic silicone heating element to achieve near physiological conditions (28–32°C). The femur components were then implanted onto the femur head using Simplex P (Stryker) low viscosity bone cement. We used four ceramic (ReCerf™) and four metal implants (ADEPT®) of equal and varying size. (2 × (42mm, 46mm, 48mm, 50mm). Temperature change was measured using a thermometer probe placed into femur neck and head from the lateral side with position check using an image intensifier. Implant surface temperature was measured using a calibrated infrared thermometer at a standard 30cm distance. Head bearing surface diameter was measured using a micro-meter. Measurements were taken 2mins pre-implantation and sequentially at 1, 5, 10, 15, 20, 25 and 30 minutes after implantation. RESULTS. The bone temperature change for both metal and ceramic implants fell after implantation and then increased. The implant surface temperature increased and then stabilised for both implants. There was no significant difference in the bone or surface temperature change between metal and ceramic implants. The bearing surface diameter change was greater in the metal implants, although this was not significant. All implants returned to within one µm of initial surface diameter at 30 minutes. CONCLUSIONS. The femoral head component of a ceramic resurfacing has similar properties for surface temperature change following implantation to conventional MOM resurfacing. The periprosthetic bone is not at risk of significant heat necrosis during cementation (max temp 32°C). The deformation following implantation was similar for both metal and ceramic components. All implants returned to near initial diameter. The deformation and temperature changes following implantation of a ceramic resurfacing are similar to a metal implant

It's easy to say that hip resurfacing is a failed technology. Journals and lay press are replete with negative reports concerning metal-on-metal bearing failures, destructive pseudotumors, withdrawals and recalls. Reviews of national joint registries show revision risks with hip resurfacing exceeding those of traditional total hip replacement, and metal bearings fare worst among all bearing couples. Yet, that misses the point. Modern hip resurfacing was never meant to replace total hip replacement (THR). It was intended to preserve bone in young patients who would be expected to need multiple revisions due to their youth and high-demand activities. The stated goal of the developers of the Birmingham Hip Resurfacing (BHR) was to delay THR by 10 years. In the two decades that followed the release of BHR, this goal has been met and exceeded. Much has been learned about indications, patient selection, and surgical technique. We now know that this highly specialised, challenging procedure is best indicated in the young, active male with osteoarthritis, as a complementary, not competitive procedure, to THR. Resurfacing has many advantages. First and foremost, it saves bone, on the day of surgery, and over the next several years by preventing stress shielding. Dislocations are very rare. Leg length discrepancy and changes in offset are avoided. Post-operative activity, including heavy manual labor and contact sports, is unrestricted. More normal loading of the femur and joint stability has allowed professional athletes to regain their careers. Femoral side revisions, if necessary, are simple total hips, and dual mobility constructs allow one to keep the socket. Adverse reactions to metal debris (ARMD), including pseudotumors, have generated great concern. Initially described only in women, it was unclear whether the etiology was allergy, toxicity, or inflammation. A better understanding of the wear properties of the bearing, and its relation to size, anteversion, hip dysplasia and metallurgy, along with retrieval analysis, allow us to conclude that it is excessive wear due to edge loading which is the fundamental mechanism for the vast majority of ARMD. Thus, patient selection, implant selection and surgical technique, the orthopaedic triad, are paramount. What has been most impressive are the truly exceptional results in young, active men. The worst candidates for THR turn out to be the best candidates for resurfacing. The ability to return to full, unrestricted activity is just as important to these patients as the spectacular survivorship in centers specializing in resurfacing. If they are unlucky and face a revision, they are not facing the life-changing outcomes of a long revision femoral stem. So if the best indication for hip resurfacing is the young, active male, let's look at the results of resurfacing these patients in centers with high volumes, using devices with a good track record, such as BHR. Several centers around the world report 10–18 year success rates of BHR in males under 50 at 98–100%. Return to athletics is routinely achieved, and even professional athletes have regained their careers. Hip resurfacing doesn't have to be better than THR to be popular among patients. Just the idea of saving all that bone makes it attractive. In the young active male, however, the results exceed those of THR, while leaving better revision options for the future. This justifies its continued use in this challenging patient population

Background. Hip resurfacing has advantages for the young active patient with arthritis; maintaining a large range of motion, preserving bone stock, and reduced dislocation risk. However high serum metal ion levels with metal-on-metal resurfacing, and their clinical implications, has led to a decline in the use of hip resurfacing. Ceramic bearing surfaces display the lowest frictional torque and excellent wear rates. Recent developments have enabled large, strong ceramic materials to be used as resurfacing components. Any wear debris that is generated from these articulations is inert. However an all-ceramic hip resurfacing could be at risk of fracture at the head-stem junction. A new ceramic hip resurfacing system with a titanium-ceramic modular taper junction has been developed. The introduction of a taper introduces the potential for fretting corrosion; we sought to determine the extent of this in an in-vitro model, and compared this prosthesis to the conventional 12/14 titanium-cobalt chrome (Ti6Al4V-CoCr) taper junction. Methods. To simulate the gait cycle, sinusoidal cyclical loads between 300N-2300N, at a frequency of 3Hz, were applied to different head-neck offsets generating different bending moments and torques. The effect of increasing the bending moment and frictional torque were tested separately. Furthermore, the resurfacing head was mounted in a fixture held with just the stem, thus representing complete bone resorption under the head. An electrochemical assessment using potentiostatic tests at an applied potential of 200mV, was used to measure the fretting current (μA) and current amplitude (μA). In a short-term 1000 cycle test, six neck lengths (short to xxx-long) of the Ti6Al4V-CoCr taper were compared to the standard neutral (concentric), and 3mm A/P offset stem options for the resurfacing design. To represent frictional torque, four increments of increasing torque (2-4-6-8Nm) were applied to both tapers. In a long term test with the resurfacing stem, the worst-case scenario of the eccentric offset option and 8Nm of torque were applied, and potentiostatic measurements were taken every million cycles, up to 10 million cycles. Results. For bending moment through the centre of the head, the standard neutral resurfacing taper displayed equivalent fretting current (1.35μA) compared to its conventional taper equivalent, the short 12/14 Ti6Al4V-CoCr taper (Fig. 1a). That was despite the bending moment through the resurfacing taper being higher due to the offset nature of its taper in relation to the centre of the head. For applied torque, the resurfacing taper displayed reduced average fretting current and average maximum fretting current when compared to the conventional taper (Fig. 1b), though this did not reach statistical significance (Kruskal-Wallis test). Under long term testing for worst-case bending and torque, the resurfacing taper displayed low fretting currents (<2μA and <5μA respectively) with no significant variance of the median values across 10 million cycles (Figs. 2 and 3). Conclusion. When compared to the gold-standard taper junction, the LIMA ceramic hip resurfacing displays equivalent fretting corrosion for bending moment and improved fretting corrosion for frictional torque. Across long term testing, stable and low fretting currents at this taper junction highlight its potential in clinical use

Introduction. Because of the low cost and easy access, surgical video has become a popular method of acquiring surgical skills outside operating rooms without disrupting normal surgical flow. However, currently existing video systems all use a single point of view (POV). Some complex orthopedic procedures, such as joint replacement, require a level of accuracy in several dimensions. So single and fixed POV video may not be enough to provide all the necessary information for educational and training purposes. The aim of our project was to develop a novel multiple POV video system and evaluate its efficacy as an aid for learning joint replacement procedure compared with traditional method. Materials and Methods. Based on the videos of a hip resurfacing procedure performed by an expert orthopedic surgeon captured by 8 cameras fixed all around the operating table, we developed a novel multiple POV video system which enables users to autonomously switch between optimal viewpoints (Figure 1). 30 student doctors (undergraduate years 3–5 and naive to hip resurfacing procedure) were recruited and randomly allocated to 2 groups: experiment group and control group, and were assigned to learn the procedure using multiple or single POV video systems respectively. Before learning they were first asked to complete a multiple choicetest designed using a modified Delphi technique with the advice and feedback sought from 4 experienced orthopedic surgeons to test the participants' baseline knowledge of hip resurfacing procedure. After video learning, they were asked to answer the test again to verify their gained information and comprehension of the procedure, followed by a 5-point Likert-scale questionnaire to demonstrate their self-perception of confidence and satisfaction with the learning experience. The scores in the 2 tests and in the Likert-scale questionnaire were compared between 2 groups using Independent-Samples t-test (for normally distributed data) or Mann-Whitney U test (for non-normally distributed data). Statistical significance was set as p<0.05. Results. There was no significant difference regarding the ages of the participants between the experiment group (22.27 ± 1.79 years) and the control group (23.00 ± 1.56 years) (p value=0.242). The 10 questions in the test were divided into 3 subcategories: 4 questions regarding spatial awareness, 4 regarding operation details and 2 regarding sequence comprehension. There was no significant difference between both cohorts in the baseline test scores (for overall scores or scores in any subcategory) before video-learning, thus ensuring homogeneity. Yet, there was a 31.6–75.4% significantly (p<0.033) higher test score after video learning in the experiment group compared with the control group (for overall, spatial awareness and operation details scores) (Figure 2). The mean Likert-scale questionnaire score in the experiment group was also 32% significantly greater than the control group (Figure 3). Conclusion. Trainees could gain better knowledge and comprehension of hip resurfacing procedure and show higher confidence and satisfaction after learning using the novel multiple POV video system compared with traditional single POV video. The novel system could serve as an effective tool for teaching hip resurfacing procedure before trainees proceed to the real operating room. For figures, please contact authors directly

As there are many reports describing avascular reactions to metal debris (ARMD) after Metal-on-Metal Hip Arthroplasty (MoMHA), the use of MoMHA, especially hip resurfacing, is decreasing worldwide. In cases of ARMD or a rise of metal ion blood levels, revision is commended even in pain free patients with a well integrated implant. The revision of a well integrated implant will cause bone loss. As most of the patients with a hip resurfacing are young and a good bone stock is desirable for further revision surgeries, the purpose of this study was to evaluate the stability of a cemented polyethylene cup in a metal hip resurfacing cup. Two different hip resurfacing systems were investigated in this study (ASR™, DePuy Orthopaedics, Leatherhead, UK; Cormet™, Corin Group, Cirencester, UK). Six different groups were formed according to the treatment and preparation of the cement-cup-interface (table 1). Before instilling cement in groups 1, 3, 5 the surface, which was contaminated with blood, was cleaned just using a gauze bandage. In groups 2, 4, 6 saline, polyhexanid and a gauze were used to clean the surface prior to the cement application. In group one and two the polyethylene cup (PE) was cemented either into Cormet™ or ASR™, just the ASR™ was further investigated in group three to six. A monoaxial load was applied while the cup was fixed with 45 degrees inclination (group 1–4) and 90 degrees inclination (group 5, 6: rotatory stability) and the failure torque was measured. In contrast to group 1 and 2, the cement penetrated the peripheral groove of the ASR™ in groups 3–6. The mean failure torque of five tests for each group was compared between the groups and the implants. The ASR™ showed mean failure torque of 0.1 Nm in group one, of 0.14 Nm in group two, of 56.9 Nm in group three, of 61.5 Nm in group four, of 2.96 Nm in group five and of 3.04 Nm in group six. The mean failure torque of the Cormet™ was 0.14 Nm both in groups one and two (table 2). In groups 1–6 there were no significant differences between the different preparations of the interface. Furthermore, in groups 1 and 2 there were no significant differences between the Cormet™ and the ASR™. The mean failure torque of group 4 was significant increased compared to group 3 (p=0.008). We saw an early failure of the cement fixation due to the smooth surface of the Cormet™ and the ASR™ components in groups 1, 2, 5, 6. In contrast to other hip resurfacing cups the ASR™ has a peripheral groove, which was not cemented except in groups 3 and 4 and therefore the lever-out failure torque was significant increased in these groups. Nevertheless, the groove did not provide stability of the cement-PE compound in case of rotatory movements. In conclusion we do not recommend the use of these methods in clinical routine. The complete removal of hip resurfacing components seems to be the most reasonable procedure

Introduction. While fixation on the acetabular side in resurfacing implants has been uncemented, the femoral component is usually cemented. The most common causes for early revision in hip resurfacing are femoral head and or neck fractures and aseptic loosening of the femoral component. Later failures appear to be more related to adverse soft-tissue reactions due to metal wear. Little is known about the effect of cementing techniques on the clinical outcome in hip resurfacing, since retrieval analysis of failed hip resurfacing show large variations. Two cementing techniques have dominated. The indirect low viscosity (LV) technique as for the Birmingham Hip resurfacing (BHR) system and the direct high viscosity (HV) technique as for the Articular Surface replacement (ASR) system. The ASR was withdrawn from the market in 2010 due to inferior short and midterm clinical outcome. This study presents an in vitro experiment on the cement mantle parameters and penetration into ASR resurfaced femoral heads comparing both techniques. Methods. Five sets of paried frozen cadavar femura (3 male, 2 female) were used in the study. The study was approved by ethics committee. Plastic ASR replicas (DePuy, Leeds, UK), femoral head size 47Ø were used. The LV technique was used for the right femora (Group A, fig. 1 and 3) while the HV technigue was used for the left femora (Group B. Fig 2 and 4). The speciments were cut into quadrants. An initiial visual, qualitative evaluation was followed by CT analysis of cement mantle thickness and cement penetration into bone. Results. No significant differences were seen between the four quadrants within each group. The LV technigue resulted in greater cement penetration and increased cement mantle under the top proximally. The HV technique showed less penetration and lower cement mantle. See figures 1–4. Discussion. The aim was to analyze the effect of the cementing techniques used in hip resurfacing practice. The ASR implant was chosen to improve understanding of whether the implant may have been sensitive to cementing techniques and whether an analysis of cementing with the recommended HV technique may assist in explaning the high incidence of short-term ASR revisions due to fractures. Findings for the HV technigue would indicate a superior technique according to consensus in conventional arthropalsty However, this contradicts clinical evidence on resurfacing, where LV cementation has been shown tho be superior. The superficial intergration in the HV technigue may result in only a superficial integration and subsequently suboptimal fixation to bone. To view tables/figures, please contact authors directly

INTRODUCTION. Ceramic-on-ceramic hip resurfacing offers a bone conserving treatment for more active patients without the potential metal ion risks associated with resurfacing devices. The Biolox Delta ceramic material has over 15 years of clinical history with low wear and good biocompatibility but has been limited previously in total hip replacement to 48mm diameter bearings [1]. Further increasing the diameter for resurfacing bearings and removing the metal shell to allow for direct fixation of the ceramic cup may increase the wear of this material and increase the risk of fracture. METHODS. Eighteen implants (ReCerf™, MatOrtho, UK; Figure1) were wear tested; six were ⊘40mm (small) and twelve ⊘64mm (large). All small and six large implants were tested under ISO 14242 standard conditions for 5 million cycles (mc) at 30° inclination (45° clinically). The six remaining large implants were tested under microseparation conditions in which rim contact was initiated during heel strike of the gait cycle for 5mc. Cups were orientated at 45° inclination (60° clinically) to allow for separation of the head and cup with a reduced 50N swing phase load and a spring load applied to induce a 0.5mm medial-superior translation of the cup. Wear was determined gravimetrically at 0.5mc, 1mc and every mc after. RESULTS. Wear was low in both standard and microseparation tests, less than 1mm. 3. cumulatively over 5mc (Figure 2). Standard conditions showed a run-in wear phase over the first mc followed by negligible wear in both diameters. The run-in wear significantly increased from 0.2mm. 3. /mc in the 40mm diameter bearings to 0.5mm. 3. /mc with the larger diameter implants. Under microseparation conditions, there was low wear over the first mc, increasing to 0.28mm. 3. /mc between 1–3mc. The wear rate reduced to 0.11mm. 3. /mc from 3=5mc. Stripe wear was evidenced on the microseparated components. There were no incidences of fracture or squeaking. DISCUSSION. Biolox Delta is known for its low wear rates but published results have only reported testing up to ⊘36mm [2]. Increasing the diameter to 64mm showed increased wear compared to smaller diameters but this was only significant over the first mc suggesting similar performance long term. Microseparation testing of these large sized bearings doubled the cumulative wear produced over 5mc but wear measured was still much lower than other bearing combinations. Wear of metal-on-metal resurfacing implants under these high angle, microseparation conditions has been reported up to 10.5mm. 3. /mc [3], significantly higher than any wear rate reported in the current study. Despite the 3mm wall thickness, no fracture of the cup occurred but stripe wear was observed in the ceramic components. SIGNIFICANCE. Biolox Delta ceramic is appropriate for use in larger diameters without excessive wear or damage to the bearings. The improved biocompatibility of the material may allow for hip resurfacing to be offered to more patients than currently available. For any figures or tables, please contact the authors directly