Aims. The aim of this study was to assess medium-term improvements following total hip arthroplasty (THA), and to evaluate what effect different preoperative Oxford Hip Score (OHS) thresholds for treatment may have on patients’ access to THA and outcomes. Methods. Patients undergoing primary THA at our institution with an OHS both preoperatively and at least four years postoperatively were included. Rationing thresholds were explored to identify possible deprivation of OHS improvement. Results. Overall, 2,341 patients were included. Mean OHS was 19.7 (SD 8.2) preoperatively and 39.7 (SD 9.8) at latest follow-up. An improvement of at least eight-points, the minimally important change (MIC), was seen in 2,072 patients (88.5%). The mean improvement was 20.0 points (SD 10.5). If a rationing threshold of OHS of 20 points had been enforced, 90.8% of those treated would have achieved the MIC, but only 54.3% of our cohort would have had access to surgery; increasing this threshold to 32 would have enabled 89.5% of those treated to achieve the MIC while only depriving 6.5% of our cohort. The ‘rationed’ group of OHS > 20 had significantly better OHS at latest follow-up (42.6 vs 37.3; p < 0.001), while extending the rationing threshold above 32 showed postoperative scores were more significantly affected by the ceiling effect of the OHS. Conclusion. The OHS was not designed as a tool to ration healthcare, but if it had been used at our institution for this cohort, applying an OHS threshold of 20 to routine THA access would have excluded nearly half of patients from having a THA; a group in which over 85% had a significant improvement in OHS. Where its use for rationing is deemed necessary, use of a higher threshold may be more appropriate to ensure a better balance between patient access to treatment and chances of achieving good to excellent outcomes. Cite this article: Bone Jt Open 2022;3(3):196–204

Escalating health care expenditure worldwide is driving the need for effective resource decision-making, with medical practitioners increasingly making complex resource decisions within the context of patient care. Despite raising serious legal and ethical issues in practice, this has attracted little attention in Australia, or internationally. In particular, it is unknown how orthopaedic surgeons perceive their obligations to the individual patient, and the wider community, when rationing care, and how they reconcile competing obligations. This research explores legal and ethical considerations, and resource allocation by Australian orthopaedic surgeons, as a means of achieving public health cost containment driven by macro-level policy and funding decisions. This research found that Australian orthopaedic surgeon's perceptions, and resource allocation decision making, can be explained by understanding how principles of distributive justice challenge, and shift, the traditional medical paradigm. It found that distributive justice, and challenges of macro level health policy and funding decisions, have given rise to two new medical paradigms. Each which try to balance the best interests of individual patients with demands in respect of the sustainability of the health system, in a situation where resources may be constrained. This research shows that while bedside rationing has positioned the medical profession as the gate keepers of resources, it may have left them straddling an increasingly irreconcilable void between the interests of the individual patient and the wider community, with the sustainability of the health system hanging in the balance

The global economy has been facing a financial crisis. Healthcare costs are spiraling, and there is a projected £30 billion health funding gap by 2020 in the UK. 1. This has prompted a drive for efficiency in healthcare provision in the UK, and in 2012, the Health and Social Care Act was introduced, heralding a fundamental change to the structure of the National Health Service, especially in the way that healthcare is funded in England. 2. What is happening in the UK is a reflection of a global problem. Rationing of healthcare is a topic of much discussion; as unless spending is capped, providing healthcare will become unsustainable. Who decides how money is spent, and which services should be rationed? . In this article we aim to discuss the impact that rationing may have on orthopaedic surgery, and we will discuss our own experiences of attempts to ration local services. 3. We also seek to inform and educate the general orthopaedic community on this topic

Introduction. Rationing of orthopaedic services is increasingly being used by Care Commissioning Groups (CCG) within the United Kingdom to restrict the numbers of patients being referred for Total Hip Arthroplasty (THA). In Devon, only patients with an Oxford Hip Score (OHS) less than 20 are referred on for specialist Orthopaedic Review. The aim of this study was to look at long term outcomes after THA to see if this rationing has any rational base to justify its use. Methods. Consecutive patients undergoing THA in Exeter between 1996 and 2012 had OHS' collected prospectively pre-operatively and a minimum of 4 years post-operatively. These scores were analysed looking for trends in patient related outcome scores. Results. 2341 patients had an OHS at a minimum of 4 years' post-op (mean 4.97 years, SD 0.33, range 4.0–5.5). This accounted for just under 50% of patients operated on in this period. Average improvement in OHS post THA was 19.6 points (range 0–44). 45.7% of patients undergoing THA had a pre-operative OHS of greater than the CCG threshold of 20. Patients did have a significantly better increase in post-operative OHS when their starting score was less than 20 but patients above this threshold still had a significant benefit from THA. However, patients with a pre-operative OHS less than 32 seemed to have more benefit from THA compared to those with a pre-op OHS of greater than 32. Interesting 7.8% of patients did not achieve the mean detectable change of 5 points in OHS at a minimum of 4 years' post THA. Conclusion. Rationing has been introduced in many CCG's around the country. Little of the rationing decisions have their basis in scientific fact and reasoning. Our data would suggest that 92.2% of patients undergoing THA have excellent outcomes. If rationing were to be fully patient centred all patients with an OHS less than 32 should be considered for THA

A spine compression fracture is a very common form of fracture in elderly with osteoporosis. Injection of polymethyl methacrylate (PMMA) to fracture sites is a minimally invasive surgical treatment, but PMMA has considerable clinical risks. We develop a novel type thermoplastic injectable bone substitute contains the proprietary composites of synthetic ceramic bone substitute and absorbable thermoplastic polymer. We used thermoplastic biocompatible polymers Polycaproactone (PCL) to encapsulate calcium-based bone substitutes hydroxyapatite (Ca10(PO4)6(OH)2, HA) and tricalcium phosphate (TCP) to form a biodegradable injectable bone composite material. The space occupation ration PCL:HA/TCP is 1:9. After heating process, it can be injected to fracture site by specific instrument and then self-setting to immediate reinforce the vertebral body. The thermoplastic injection bone substitute can obtain good injection properties after being heated by a heater at 90˚C for three minutes, and has good anti-washout property when injected into normal saline at 37˚C. After three minutes, solidification is achieved. Mechanical properties were assessed using the material compression test system and the mechanical support close to the vertebral spongy bone. In vitro cytotoxicity MTT assay (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) was performed and no cell cytotoxicity was observed. In vivo study with three New Zealand rabbits was performed, well bone growth into bone substitute was observed and can maintain good mechanical support after three months implantation. The novel type thermoplastic injection bone substitute can achieve (a) adequate injectability and viscosity without the risk of cement leakage; (b) adequate mechanical strength for immediate reinforcement and prevent adjacent fracture; (c) adequate porosity for new bone ingrowth; (e) biodegradability. It could be developed as a new option for treating vertebral compression fractures

Introduction. Osteoarthritis in the foot and ankle affects approximately 30,000 patients annually in the UK. Evidence has shown that excess weight exacerbates foot pain, with significant increases in joint forces. However, despite the current trend for Clinical Commissioning Groups to ration surgery for obese patients, studies have not yet determined the effect of weight loss in obese patients with foot and ankle arthritis. Aim. Pilot study to investigate the effect of simulated weight loss on pain scores in obese patients with symptomatic foot and ankle arthritis. Methods. Following ethical approval, a prospective study of 17 obese patients (mean BMI 39.2, range 31.2 – 50.3) with foot and ankle arthritis was undertaken (BOFAS funded). Under physiotherapist supervision, patients walked for one minute on an anti-gravity treadmill, which allowed simulated weight reduction. Following baseline assessment, reduced BMI was simulated, starting at 20, rising in increments of 5, until each patient's usual BMI was reached. Pain was assessed using a Visual Analogue Scale (VAS). Repeated measures ANOVA was used to assess for significant changes in pain, comparing baseline with each simulated BMI category (significance set at p< 0.05). Results. Simulated weight loss caused a significant reduction in pain (p=0.005, power 0.91). Mean VAS pain scores improved by 24% (p=0.003) and 17% (p=0.040) for BMI categories 20 and 25, compared with baseline. Pain scores were not significantly different comparing BMI categories of 25 and 20. Conclusion. Simulated weight loss to normal BMI significantly decreased pain in obese patients with foot and ankle arthritis. The use of the anti-gravity treadmill to demonstrate the feeling of normal BMI has also provided motivation to several patients to lose weight. The current study could be used to power future studies to investigate the effects of weight loss in foot and ankle patients

Abstract. Introduction. There is a longstanding presumed association between obesity, complications, and revision surgery in primary knee arthroplasty. This has more recently been called into question, particularly in centres where a high volume of arthroplasty is performed. We investigated the correlation between Body Mass Index (BMI), mortality, and revision surgery. Method. This was a cohort study of at least 10 years following primary knee arthroplasty from a single high volume arthroplasty unit. Mortality and revision rates were collected from all patients who underwent primary knee arthroplasty between 2009 and 2010. Kaplan Meier analysis was performed. Results. There were 1161 female and 948 male patients with a mean age of 69 (21 to 97). All cause survivorship excluding mortality was 97.2% up to 13yrs with a minimum of 10 years. The revision rate in this series was 2.8% with no significant difference in revision rates after 10 year between patients with BMI above and below 40 (p=0.438). There was no significant difference in 10-year mortality between patients above and below a BMI of 40 (p=0.238). Conclusion. This study shows no significant difference in the long term survival of total knee replacement between patients with normal and high BMI. Careful consideration should be given before rationing surgery based on BMI alone

There is a longstanding presumed association between obesity, complications, and revision surgery in primary knee arthroplasty. This has more recently been called into question, particularly in centres where a high volume of arthroplasty is performed. We investigated the correlation between Body Mass Index (BMI), mortality, and revision surgery. This was a cohort study of at least 10 years following primary knee arthroplasty from a single high volume arthroplasty unit. Mortality and revision rates were collected from all patients who underwent primary knee arthroplasty between 2009 and 2010. Kaplan Meier analysis was performed. There were 1161 female and 948 male patients with a mean age of 69 (21 to 97). All cause survivorship excluding mortality was 97.2% up to 13yrs with a minimum of 10 years. The revision rate in this series was 2.8% with no significant difference in revision rates after 10 year between patients with BMI above and below 40 (p=0.438). There was no significant difference in 10–year mortality between patients above and below a BMI of 40 (p=0.238). This study shows no significant difference in the long term survival of total knee replacement between patients with normal and high BMI. Careful consideration should be given before rationing surgery based on BMI alone

Aims. The aim of this study was to investigate whether the use of antibiotic-loaded bone cement influenced the risk of revision surgery after primary total hip arthroplasty (THA) for osteoarthritis. Methods. The study involved data collected by the National Joint Registry (NJR) for England and Wales, Northern Ireland and the Isle of Man between 1 September 2005 and 31 August 2017. Cox proportional hazards were used to investigate the association between use of antibiotic-loaded bone cement and the risk of revision due to prosthetic joint infection (PJI), with adjustments made for the year of the initial procedure, age at the time of surgery, sex, American Society of Anesthesiologists (ASA) grade, head size, and body mass index (BMI). We looked also at the association between use of antibiotic-loaded bone cement and the risk of revision due to aseptic loosening or osteolysis. Results. The cohort included 418,857 THAs of whom 397,896 had received antibiotic-loaded bone cement and 20,961 plain cement. After adjusting for putative confounding factors, the risk of revision for PJI was lower in those in whom antibiotic-loaded bone cement was used (hazard ration (HR) 0.79; 95% confidence interval (CI) 0.64 to 0.98). There was also a protective effect on the risk of revision due to aseptic loosening or osteolysis, in the period of > 4.1 years after primary THA, HR 0.57, 95% CI 0.45, 0.72. Conclusion. Within the limits of registry analysis, this study showed an association between the use of antibiotic-loaded bone cement and lower rates of revision due to PJI. The findings support the continued use of antibiotic-loaded bone cement in cemented THA. Cite this article: Bone Joint J 2020;102-B(8):997–1002

Primary Care Trusts across the country are being encouraged to ration service provision due to austerity measures. Obesity has been suggested as a rationing tool with poor clinical outcomes sited as justification. There is, however, a lack of evidence in the literature pertaining to clinical outcomes post elective foot and ankle surgery in patients with an increased Body Mass Index (BMI). All patients undergoing elective foot and ankle surgery at Queen Alexandra Hospital, Portsmouth are entered into a prospective database, which includes their BMI at time of assessment in clinic. From this, we analysed the notes of all patients with a BMI ≥30, excluding any not operated on between July 2007 and August 2009 or with a BMI of <30 at time of surgery, to determine whether there was an increased incidence of peri- or post-operative complications. Included in the study were 109 patients with a mean age of 54 (range 21 - 79). Female patients accounted for 63% of those notes reviewed and the mean BMI was 34 (range 30 - 50). A mixture of hindfoot and forefoot procedures were carried out (20 different procedures). Median length of stay was 0 nights (range 0 – 15 days). The causes for excessive length of stays (>4 nights) included a pre operative Lower Respiratory Tract Infection missed prior to intubation and the initiation of CPAP post operatively in a patient with known Obstructive Sleep Apnoea. We found 3 cases of post operative Venous Thrombo-embolism within 3 months of surgery and 1 proven wound infection in a non-insulin dependent diabetic patient. Also noted were 3 non-unions, all requiring further surgery. Based on our historical evidence of infective and thrombo-embolic complications in patients with a BMI <30, we conclude that peri- and post-operative complications in obese patients occur no more frequently than in a patient population with a BMI <30

Introduction. Computer navigation is a highly sophisticated tool in orthopedic surgery for component placement in total hip arthroplasty (THA). A number of recommendations have been published. Although Lewinnek's safe-zone is the best-known among these its significance is questioned in recent years since it addresses the acetabular socket only ignoring the femoral stem. Modern target definitions consider both socket and stem and provide well-defined recommendations for complementary component positioning. We present a new small-sized hand-held imageless navigation system that implies these targets and supports the surgeon in realizing the concept of combined anteversion and combined Target-Zone (cTarget- Zone) in THA and to control leg length and offset without altering the standard surgical work-flow and we report initial results. Methods. The targets for positioning the components of a total hip as expressed by radiographic cup inclination (cRI) and anteversion (cRA), stem antetorsion (sAT) and neck-to-shaft angle (sNSA) are determined for a specific prosthesis system using a computerized 3D-model. The optimizing goal is maximizing the size of the cSafe-Zone providing the largest target zone for an impingement-free prosthetic range of motion (pROM) in order to minimize the risk for dislocation in physiologic and combined movements. Independent parameters like head size, head-to-neck ration and also component orientations like cRI, cRA, sAT and sNSA were varied systematically and the optimal cSafe-Zone was computed in semi-automated batch runs. These optimized prosthesis-specific results were introduced into the software of the hand-held navigation system. This system measures leg length, offset, acetabular and femoral head centers intraoperatively. Results. In contrast to Lewinnek the outline of our cSafe-Zone is not rectangular but polygonal. Its size shows prosthesis-specific maxima. The largest zones are found for optimal sNSA values at 126° +/−4°, optimal ranges for cRI depend on head size and range from 44° to 36°, best sAT range from 10° to 18°, cRA from 18° to 25°. There is a prosthesis- specific linear correlation between sAT and cRA that denotes the combined anteversion. The target value for combined anteversion is not dependent on pelvic tilt but on sNSA. The hand-held navigation system displays all these orienting parameters as well as leg-length and offsets. Furthermore, it supports a virtual reduction work-flow thus accelerating surgery. All these information provide important decision-making details for the surgeon intraoperatively in real-time for augmented quality. Conclusion. The combined Target-Zone provides the basis for patient- and implant-specific control of prosthesis implantation. It includes all important positioning parameters of both total hip components and such gives well-defined individual recommendations for the targets. The new hand-held navigation system (Naviswiss) provides a smart way to direct and control the total hip implantation according to the best combined orientation considering also the concept of combined Safe-Zone. Such it prevents outliers, provides better safety and documents the surgical workflow and the final result of the surgery

Background. Delay in access to primary total hip (THA) arthroplasty continues to pose a substantial burden to patients and society in publicly funded healthcare systems. The majority of strategies to decrease wait times have focused on the time from surgical consult to surgery, however a large proportion of total wait time for these patients is the time from primary care referral to surgical consultation. Prioritization scoring tools and patient reported outcome measures are being used in an attempt to ration limited resources in the face of increasing demand. However, to our knowledge, no study has investigated whether a referral Oxford Hip Score (OHS) could be used to triage non-surgical referrals appropriately, in an effort to increase timely access to specialists for patients that are candidates for total joint replacement (TJR). Purpose. 1) To determine if a referral OHS has the predictive ability to discriminate when a hip patient will be deemed surgical versus conservative by the surgeon during their first consultation 2) To identify an OHS cut-off point that can be used to accurately predict when a primary THA referral will be deemed conservative by the consultant surgeon during the first consultation. Methods. We retrospectively reviewed all consecutive THA consultations from a single surgeon's tertiary, high volume practice over a 3-year period. Patients with a pre-consultation OHS, BMI <41, and no absolute contraindication to TJR were included. Consultation were categorized into two groups based on surgeon's decision, those that were offered THR during their first consultation (operative) versus those that were not (conservative). Baseline demographic data and OHS were abstracted. Variables of interest were compared between cohorts using the exact chi-square test and Wilcoxon rank-sum test. Spearman's rank correlation coefficients were used to measure association between pre-consult OHS and the surgeon's decision. A receiver operator characteristic (ROC) curve analysis was used to calculate the area under the curve (AUC) and to identify a cut-off point for the pre-operative OHS that identified whether or not a referral was deemed conservative. Results. The study 478 hips (388 patients) with a median OHS of 22 (IQR 16–29). Median pre-consultation OHS demonstrated clinically and statistically significant differences between the surgical versus conservative cohorts (p<0.001). Spearman's rank correlation coefficient between OHS and a patient being deemed surgical or conservative was strong for the OHS at −0.62 (95% CI −0.67 to −0.56). The ROC AUC values for hip consults (0.87, 95% CI 0.84–0.91) was good, indicating that pre-consult OHS has predictive ability to discriminate a surgeon's decision of surgical versus conservative. One plausible conservative threshold that optimized sensitivity and NPV for hips is OHS >34 (sensitivity=0.997 NPV=0.978). ROC analysis identified severable potential lower, depending on weight of prioritization of sensitivity, specificity, and NPV. Conclusion. Referral OHS demonstrate good ability to discriminate when a knee or hip TJR referral will be deemed non-surgical versus surgical at their first consultation in a single surgeon's practice. Multiple potential OHS thresholds can be applied as a tool to decrease wait times for primary THR. However, a cost analysis would aid in identifying the optimal cut-off score, and these findings need to be validated with multi-surgeon/center studies before they can be broadly applied

Pigmented villonodular synovitis (PVNS) is a rare proliferative process of the synovium which most commonly affects the knee and occurs in either a localised (LPVNS) or a diffuse form (DPVNS). The effect of different methods of surgical synovectomy and adjuvant radiotherapy on the rate of recurrence is unclear. We conducted a systematic review and identified 35 observational studies in English which reported the use of surgical synovectomy to treat PVNS of the knee. A meta-analysis included 630 patients, 137 (21.8%) of whom had a recurrence after synovectomy. For patients with DPVNS, low-quality evidence found that the rate of recurrence was reduced by both open synovectomy (odds ration (OR) = 0.47; 95% CI 0.25 to 0.90; p = 0.024) and combined open and arthroscopic synovectomy (OR = 0.19, 95% CI = 0.06 to 0.58; p = 0.003) compared with arthroscopic surgery. Very low-quality evidence found that the rate of recurrence of DPVNS was reduced by peri-operative radiotherapy (OR = 0.31, 95% CI 0.14 to 0.70; p = 0.01). Very low-quality evidence suggested that the rate of recurrence of LPVNS was not related to the surgical approach. . This meta-analysis suggests that open synovectomy or synovectomy combined with peri-operative radiotherapy for DPVNS is associated with a reduced rate of recurrence. Large long-term prospective multicentre observational studies, with a focus on both rate of recurrence and function, are required to confirm these findings. Cite this article: Bone Joint J 2015;97-B:550–7

The purpose of this study is to investigate what effect cross links have on scoliosis constructs and whether cross links may be used instead of pedicle screws at the apex of the deformity. The rotational stiffness of six different construct designs was investigated on scoliotic sawbone models with zero, one or two cross links. In three of the constructs the screws at the apex were removed. Testing was performed to an average torque of 3Nm and ration was detected using electromagnetic motion tracking system. The stiffness in axial rotation of all constructs increased with the number of cross links, however the difference was not statistically significant. In constructs with apical screws the stiffness increased by 3.01% and 12.9% for one and two cross links respectively. In constructs without apical screws the increase was 1.64% and 14.3% for one and two cross links respectively. The total stiffness of the construct increased with the addition of apical screws by 20%, 21.7% and 18.8% for zero, one and two cross links respectively. This increase was statistically significant using a paired t-test (p= 0.01142). On the basis of these results we conclude that the use of cross links in scoliosis correction surgery is not necessary. Pedicle screws positioned at the apex of the scoliosis curve statistically increase the stiffness in axial rotation and are therefore necessary to promote an environment suitable for bony fusion

Introduction. Total knee arthroplasty (TKA) is an excellent treatment for end-stage osteoarthritis of the knee. In Asian countries, the number of TKA performed has rapidly increased, and is expected to continue so with its 4.4 billion population and increasing life expectancy. Asians' knees are known to be kinematically different to Caucasians after TKA. Controversy exists as to whether multi-radius (MR) or the newer single-radius (SR) TKA has superior outcome. Studies regarding this have been largely based on Caucasian data with few small sample Asian data. Methods. This is a retrospective analysis of prospectively collected institutional registry data between 2004 and 2015. Outcomes of 133 single-radius (SR) (Scorpio NRG, Stryker) and 363 multi-radius (MR) (Nexgen LPS, Zimmer) primary TKA for primary osteoarthritis were compared. All TKA was performed or directly supervised by the senior author. Range of motion (ROM), Oxford Knee Score (OKS), SF-36 physical component score (SF36-PCS), SF-36 mental component score (SF36-MCS), Knee Society Function Score (KS-FS) and Knee Score (KS-KS) were recorded preoperatively and at 2 years post-operation. Results. The mean age in both groups were similar at 66 ± 8 years (p=0.66). Both groups were in majority female (71% and 70% females in SR and MR respectively, p=0.10) and ethnic Chinese (79% and 84% in SR and MR respectively, p=0.53). The preoperative ROM and outcome scores in both groups were similar. MR-TKA achieved significantly greater improvement over 2 years in terms of ROM (7.5º ± 18.2º vs. 3.5º ± 19.3º, p=0.04), KS-KS (49.0 ± 20.9 vs. 42.7 ± 21.1, p=0.01), OKS (17.4 ± 18.4, p=0.03), and SF36-PCS (17.1 ± 12.5, p=0.02). At 2-years follow up, MR-TKA group fared slightly better for SF36-PCS (48 ± 10 vs. 46 ± 10, p=0.032), but the absolute difference was only 2 points. There were no significant differences between SR-TKA and MR-TKA for ROM (115º ± 16º vs. 117º ± 16º, p=0.218), KS-KS (81 ± 16 vs. 85 ± 12, p=0.795), KS-FS (74 ± 21 vs. 75 ± 20, p=0.627), OKS (20 ± 7 vs. 18 ± 6, p=0.099), and SF36-MCS (56 ± 10 vs. 55 ± 10, p=0.324). There were larger proportions of MR-TKA patients who achieved the minimum clinically important difference (MCID) for OKS (95% vs. 82%, p<0.001) and SF36-PCS (67% vs. 55%, p=0.011) at 2-years follow-up. Logistic regression, controlling for all preoperative variables, showed SR-TKA is less likely to achieve MCID for OKS with an odds ratio of 0.275 (95% confidence interval: 0.114 – 0.663, p=0.004), and SF36-PCS with an odds ration of 0.547 (0.316 – 0.946, p=0.031). Discussion and conclusion. SR-TKA and MR-TKA produced similar outcomes, in concordance with current literature. However, SR-TKA has lower odds of achieving MCID in OKS and SF36-PCS, possibly due to its smaller improvement in flexion over 2 years. This subtle difference has a greater impact in the context of Asian patients due to the cultural practice of kneeling and/or squating

Dual mobility (DM) cups have 2 points of articulation – between the shell and the polyethylene (external bearing) and between the polyethylene and the femoral head (internal bearing). Primary motion occurs at the inner bearing while the outer bearing moves only in cases of extreme range of motion. Dislocation is a top reason for revision surgery and a major cost burden on society. Instability is also a significant problem after revision THA. While a variety of factors are important in hip stability, DM cups provide the safety of larger femoral heads in virtually all patients. These larger heads increase jump distance (the distance the femoral must travel before dislocation occurs) and they also increase ROM before impingement occurs. ROM and impingement are competing with each in primary THA. Especially in the flexible female with small bone structure, their increased ROM significantly increases the risk of impingement during physiologic activities. While not necessarily leading to dislocation, subluxation can occur resulting in pain. Further, ongoing impingement reduces the longevity of the PE. The ability to increase head size and head-neck ration with the DM cups in these patients is both an immediate and long-term advantage. PE thickness still can compromise the integrity of the liner. DM cups have thicker PE, especially in the smaller size cups than standard PE inserts. Even with the dual articulation, PE wear in DM cups are less, or at worst, equivalent to standard cups while at the same time providing adequate PE thickness for PE integrity and longevity

Objective. The relationship between the index (2D) to ring finger (4D) is one of the most commonly studied anthropometric measures, which is believed to offer insight into early growth and the foetal environment. This study aimed to determine the relationship between the 2D:4D ratio and the risk of Perthes' disease in children. Methods. The 2D:4D ratio was measured in 144 cases of Perthes' disease, and 144 controls. Cases and controls were frequency matched for age and sex. Measurements were recorded using a digital venier calliper on the palmar surface of the hand. Logistic regression was undertaken adjusting for age, with stratification for sex. Results. There was a significant negative association between Perthe's disease and digit ration in the right hand in affected females OR −0.78 (95% CI 0.65 – 0.93). There was no such association in males 0.97 (0.90 – 1.05). Conclusions. There is a significant association between degree of ‘masculinisation’ and Perthes' disease. This adds evidence to suggest that a significant aetiological component in disease acts prenatally, and may begin to explain the preponderance of disease amongst males