Background. As the number of ceramic THR bearings used worldwide is increasing, the number of implants that experience off-normal working conditions, e.g. edge loading, third bodies in the joint, soft tissues laxity, dislocation/subluxation of the joint, increases too. Under all such conditions the bearing surfaces can be damaged, leading eventually to a limitation of the expected performances of the implant. Methods. We characterised the damage resistance of different bearing surfaces (alumina matrix composite BIOLOXdelta, alpha-alumina BIOLOXforte, zirconia 3Y-TZP, oxidized zirconium alloy Zr-2.5Nb, CoCr-alloy) by scratch tests performed following the European standard EN 1071–3:2005. Also the scratch hardness of same materials has been assessed. Results. The Lc1 value (i.e., the load for the onset of a scratch) measured for BIOLOXdelta is about fivefold the one measured for the oxidized zirconium alloy (OXZr) surface and about tenfold the Lc1 measured for the CoCr alloy. The height of ridges along the scratch edges due to plastic flow in the composite ceramic BIOLOXdelta are only 21% in height than in CoCr, and only a small fraction (0.04%) of the height of ridges measured on OXZr surfaces. The scratch hardness of the metal samples tested (CoCr, OXZr) results one order of magnitude lower than the ones of ceramics. This behavior is not influenced by of the presence of the coating on OXZr surface. Conclusions. The transformation toughened ceramics tested (BIOLOXdelta, 3Y-TZP) are the materials that exhibit the higher resistance to scratching. Ridges at scratch edges are lower in ceramics than in coated or uncoated metals. The result show the superior scratch resistance behavior of toughened ceramics for THR wear couples with respect to coated or bare alloys. Level of Evidence. Level 1

The current, most popular recommendation for cup orientation, namely the Lewinnek box, dates back to the 70's, that is to say at the stone age of hip arthroplasty. Although Lewinnek's recommendations have been associated with a reduction of dislocation, some complications, either impingement or edge loading related, have not been eliminated. Early dislocations are becoming very rare and most of them probably occur in “outlier” patients with atypical pelvic/hip kinematics. Because singular problems usually need singular treatments, those patients need a more specific personalised planning of the treatment rather than a basic systematic application of Lewinnek recommendations. We aim in this review to define the potential impacts that the spine-hip relations (SHRs) have on hip arthroplasty. We highlight how recent improvements in hip implants technology and knowledge about SHRs can substantially modify the planning of a THR, and make the « Lewinnek recommendations » not relevant anymore. We propose a new classification of the SHRs with specific treatment recommendations for hip arthroplasty whose goal is to help at establishing a personalized planning of a THR. This new classification gives a rationale to optimize the short and long-term patient's outcomes by improving stability and reducing edge loading. We believe this new concept could be beneficial for clinical and research purposes

There is a critical need for safe innovation in total joint replacements to address the demands of an ageing yet increasingly active population. The development of robust implant designs requires consideration of uncertainties including patient related factors such as bone morphology but also activity related loads and the variability in the surgical procedure itself. Here we present an integrated framework considering these sources of variability and its application to assess the performance of the femoral component of a total hip replacement (THR). The framework offers four key features. To consider variability in bone properties, an automated workflow for establishing statistical shape and intensity models (SSIM) was developed. Here, the inherent relationship between shape and bone density is captured and new meshes of the target bone structures are generated with specific morphology and density distributions. The second key feature is a virtual implantation capability including implant positioning, and bone resection. Implant positioning is performed using automatically identified bone features and flexibly defined rules reflecting surgical variability. Bone resection is performed according to manufacturer guidelines. Virtual implantation then occurs through Boolean operations to remove bone elements contained within the implant's volume. The third feature is the automatic application of loads at muscle attachment points or on the joint contact surfaces defined on the SSIM. The magnitude and orientation of the forces are derived from models of similar morphology for a range of activities from a database of musculoskeletal (MS) loads. The connection to this MS loading model allows the intricate link between morphology and muscle forces to be captured. Importantly, this model of the internal forces provides access to the spectrum of loading conditions across a patient population rather than just typical or average values. The final feature is an environment that allows finite element simulations to be run to assess the mechanics of the bone-implant construct and extract results for e.g. bone strains, interface mechanics and implant stresses. Results are automatically processed and mapped in an anatomically consistent manner and can be further exploited to establish surrogate models for efficient subsequent design optimization. To demonstrate the capability of the framework, it has been applied to the femoral component of a THR. An SSIM was created from 102 segmented femurs capturing the heterogeneous bone density distributions. Cementless femoral stems were positioned such that for the optimal implantation the proximal shaft axis of the femurs coincided with the distal stem axis and the position of the native femoral head centre was restored. Here, the resection did not affect the greater trochanter and the implantations were clinically acceptable for 10000 virtual implantations performed to simulate variability in patient morphology and surgical variation. The MS database was established from musculoskeletal analyses run for a cohort of 17 THR subjects obtaining over 100,000 individual samples of 3D muscle and joint forces. An initial analysis of the mechanical performance in 7 bone-implant constructs showed levels of bone strains and implant stresses in general agreement with the literature

Summary Statement. This data may help explain the variability in physical function after primary TKR as compared to primary THR. Introduction. Total knee replacement (TKR) and total hip replacement (THR) reliably relieve pain, restore function, and ensure mobility in patients with advanced joint arthritis; however these results are not uniform across all patient populations. We compared baseline demographic and symptom profiles in patients from a US national cohort undergoing primary TKR and THR. Methods. Patients undergoing primary TKR and THR between 7/1/2011 and 3/30/2012 were identified from the national research consortium which collects comprehensive data on enrolled patients from 120 surgeons across 23 states. Gathered data includes patient demographics, comorbidity (Charlson Comorbidity Index), operative joint pain severity, physical function (SF-36; Physical Component Score (PCS)), emotional health (SF-36 Mental Component Score (MCS)), and musculoskeletal burden of illness (Hip and Knee Disability and Osteoarthritis Outcome Scores; Oswestry Disability Index). Descriptive statistics compared baseline demographic and symptom profiles. Results. Our analysis compared 1362 primary TKR patients and 1013 primary THR patients. US TKR patients were significantly older (66.5 vs. 64.3 years), more obese (BMI 31.7 vs. 29.3), and less educated (p<0.005). TKR patients had higher rates of comorbidities, specifically diabetes, gastrointestinal ulcers, and cerebrovascular disease (p≤0.006). THR patients had significantly worse physical function (PCS 31.6 vs. 33.3), lower back pain (35.6% vs. 30.5% moderate-severe), and operative joint pain, stiffness, and function (p<0.005). Conclusion. US patients undergoing primary TKR are older with more comorbidities, however THR patient baseline functional and musculoskeletal limitations are significantly greater than primary TKR patients

Studies using roentgen stereophotogrammetric analysis (RSA) have shown that the femoral components of cemented total hip replacements (THR) migrate distally relative to the bone, but it is not clear whether this occurs at the cement-implant or the cement-bone interface or within the cement mantle. Our aim was to determine where this migration occurred, since this has important implications for the way in which implants function and fail. Using RSA we compared for two years the migration of the tip of the stem with that of the cement restrictor for two different designs of THR, the Exeter and Charnley Elite. We have assumed that if the cement restrictor migrates, then at least part of the cement mantle also migrates. Our results have shown that the Exeter migrates distally three times faster than the Charnley Elite and at different interfaces. With the Exeter migration was at the cement-implant interface whereas with the Charnley Elite there was migration at both the cement-bone and the cement-implant interfaces

Background. It is hypothesised that good torsional resistance of the acetabular cement mantle can increase the stability and longevity of cemented THR. Surgeons aim to achieve this by drilling keyholes (KH) in the acetabulum for the cement to penetrate. This study aims to reduce the surgical variability by investigating the influence of KH diameter on torsional resistance for a range of acetabular diameters. Methods. Three most common diameters of acetabula were tested (50, 54 and 58 mm) to compare three types of KHs: A) 3 × 12 mm diameter, 120° apart, 6 mm deep blind holes; B) 6 × 6 mm diameter, 60° apart, 6 mm deep blind holes; C) 6 × 6 mm diameter, 60° apart, through holes. An anatomically accurate experimental rig to simulate the implanted acetabulum was used, it allowed the torque strength of a cement mantle to be measured. The cups were cemented into the rig to create a 4 mm mantle and left to cure for 24 h at room temperature. Each sample was tested in the torque rig by applying a ramp displacement at 1.5 °/min until failure. The test was repeated four times for each acetabulum-keyhole combination. Peak torque was used for quantifying torsional resistance. Results. The mean and standard deviation peak torque for the A keyholes was 194 Nm (25.7), 251 Nm (25.3) and 334 Nm (20.9) for 50, 54 and 58 mm respectively; for the B keyholes the peak torque was 146 Nm (54.0), 143 Nm (48.6), 123 Nm (29.5); and for the C keyholes the peak torque was 208 Nm (6.0), 278 Nm (25.5), 244 Nm (74.1). Mann-Whitney test detected significant differences only between A and B groups at 54 mm (p = 0.021) and 58 mm (p=0.021). The torsional resistance increased with acetabular diameter only for the A keyholes (Kruskal Wallis Test, p = 0.01). Conclusions. The larger keyholes provided more consistent and substantially higher peak torque values. The difference was more evident with the increasing acetabular diameter. The large variability in the B keyholes was caused by poor cement penetration, this could potentially be the case clinically. C keyholes were an improvement, yet there were still consistency issues for the larger acetabulum. The limiting factor was the cement-cup interface, which is also where the failure occurred (except for most of the B keyholes and 58 mm acetabulum C keyholes). Level of Evidence. II b

Summary Statement. In young, active patients cementless THR demonstrates excellent prosthetic stability by RSA and outstanding clinical outcomes at 5 years using a tapered titanium femoral stem, crosslinked polyethylene liners and either titanium or tantalum shells. Introduction. Early femoral implant stability is essential to long-term success in total hip replacement. Radiostereometric analysis (RSA) provides precise measurements of micromotion of the stem relative to the femur that are otherwise not detectable by routine radiographs. This study characterised micromotion of a tapered, cementless femoral stem and tantalum porous-coated vs. titanium acetabular shells in combination with highly cross-linked UHMWPE or conventional polyethylene liners using radiostereometric analysis (RSA) for 5 years following THR. Patients and Methods. This IRB-approved, prospective, double randomised, blinded study, involved 46 patients receiving a primary THR by a single surgeon. Each patient was randomised to receive a titanium (23) (Trilogy, Zimmer) or tantalum (23) (Modular Tantalum shell, Zimmer) uncemented hemispheric shell and either a highly-crosslinked or conventional polyethylene liner. Tantalum RSA markers were implanted in each patient. All patients had a Dorr A or B femoral canal and received a cementless, porous-coated titanium tapered stem (M/L Taper, Zimmer). All final femoral broaches were stable to rotational and longitudinal stress. RSA examinations, Harris Hip, UCLA, WOMAC, SF-12 scores were obtained at 10 days, 6 months, and annually through 5 years. Results. All patients demonstrated statistically significant improvement in Harris Hip, WOMAC, and SF-12 PCS scores post-operatively. Evaluation of polyethylene wear demonstrated that median penetration measurements were significantly greater in the conventional compared to the HXPLE liner cohorts at 1 year through 5 years follow-up (p<0.003). At 5 years, conventional liners showed 0.38 ± 0.05mm vertical wear whereas HXLPE liners showed 0.08 ± 0.02mm (p<0.003). Evaluation of the femoral stems demonstrated that the rate of subsidence was highest in the first 6 months (0.09mm/yr), with no other detectable motion through 5 years. Two outlying patients had significantly higher stem subsidence values at 6 months (0.7 mm and 1.0mm). One stem stabilised without further subsidence after 6 months (0.7mm), and the other stem stabilised at 1 year (1.5mm). Neither patient has clinical evidence of loosening. Evaluation of acetabular shells demonstrated less median vertical translation in tantalum than titanium shells at each time-point except at 3-years follow-up, however due to large standard errors, there was no significant difference between the two designs (p>0.05). These large standard errors were predominantly caused by two outliers, neither of which had clinical evidence of loosening. Discussion/Conclusion. In this RSA study of young THR patients, cementless tapered femoral stems, highly crosslinked polyethylene liners, and tantalum or titanium acetabular shells all demonstrated excellent performance through 5 years follow-up. Highly crosslinked polyethylene liners demonstrated significantly less wear than conventional liners. The femoral stem showed excellent stability through 5 years, with no clinical or radiologic episodes of failure. The small amount of micromotion seen is less than that previously reported for similar tapered, cementless stems and approaches the accuracy of RSA (0.05mm). Both acetabular shells demonstrated excellent stability with minimal micromotion at 5 years without significant differences in migration. All patients demonstrated significant clinical improvement in pain and function and additional RSA evaluation of these patients is planned

Objectives. To define Patient Acceptable Symptom State (PASS) thresholds for the Oxford hip score (OHS) and Oxford knee score (OKS) at mid-term follow-up. Methods. In a prospective multicentre cohort study, OHS and OKS were collected at a mean follow-up of three years (1.5 to 6.0), combined with a numeric rating scale (NRS) for satisfaction and an external validation question assessing the patient’s willingness to undergo surgery again. A total of 550 patients underwent total hip replacement (THR) and 367 underwent total knee replacement (TKR). Results. Receiver operating characteristic (ROC) curves identified a PASS threshold of 42 for the OHS after THR and 37 for the OKS after TKR. THR patients with an OHS ≥ 42 and TKR patients with an OKS ≥ 37 had a higher NRS for satisfaction and a greater likelihood of being willing to undergo surgery again. Conclusions. PASS thresholds appear larger at mid-term follow-up than at six months after surgery. With- out external validation, we would advise against using these PASS thresholds as absolute thresholds in defining whether or not a patient has attained an acceptable symptom state after THR or TKR. Cite this article: Bone Joint Res 2014;3:7–13

Summary Statement

Corin has developed bone conserving prosthesis (MiniHip™) to better replicate the physiological load distribution in the femur. This study assessed whether the MiniHip™ prosthesis can better match the pre-osteoarthritic head centre for patient demographics when compared to contemporary long stem devices.

Abstract. Introduction. Component mal-positioning in total hip replacement (THR) and total knee replacement (TKR) can increase the risk of revision for various reasons. Compared to conventional surgery, relatively improved accuracy of implant positioning can be achieved using computer assisted technologies including navigation, patient-specific jigs, and robotic systems. However, it is not known whether application of these technologies has improved prosthesis survival in the real-world. This study aimed to compare risk of revision for all-causes following primary THR and TKR, and revision for dislocation following primary THR performed using computer assisted technologies compared to conventional technique. Methods. We performed an observational study using National Joint Registry data. All adult patients undergoing primary THR and TKR for osteoarthritis between 01/04/2003 to 31/12/2020 were eligible. Patients who received metal-on-metal bearing THR were excluded. We generated propensity score weights, using Sturmer weight trimming, based on: age, gender, ASA grade, side, operation funding, year of surgery, approach, and fixation. Specific additional variables included position and bearing for THR and patellar resurfacing for TKR. For THR, effective sample sizes and duration of follow up for conventional versus computer-guided and robotic-assisted analyses were 9,379 and 10,600 procedures, and approximately 18 and 4 years, respectively. For TKR, effective sample sizes and durations of follow up for conventional versus computer-guided, patient-specific jigs, and robotic-assisted groups were 92,579 procedures over 18 years, 11,665 procedures over 8 years, and 644 procedures over 3 years, respectively. Outcomes were assessed using Kaplan-Meier analysis and expressed using hazard ratios (HR) and 95% confidence intervals (CI). Results. For THR, analysis comparing computer-guided versus conventional technique demonstrated HR of 0.771 (95%CI 0.573–1.036) p=0.085, and 0.594 (95%CI 0.297–1.190) p=0.142, for revision for all-causes and dislocation, respectively. When comparing robotic-assisted versus conventional technique, HR for revision for all-causes was 0.480 (95%CI 0.067 –3.452) p=0.466. For TKR, compared to conventional surgery, HR for all-cause revision for procedures performed using computer guidance and patient-specific jigs were 0.967 (95% CI 0.888–1.052) p=0.430, and 0.937 (95% CI 0.708–1.241) p=0.65, respectively. HR for analysis comparing robotic-assisted versus conventional technique was 2.0940 (0.2423, 18.0995) p = 0.50. Conclusions. This is the largest study investigating this topic utilising propensity score analysis methods. We did not find a statistically significant difference in revision for all-causes and dislocation although these analyses are underpowered to detect smaller differences in effect size between groups. Additional comparison for revision for dislocation between robotic-assisted versus conventionally performed THR was not performed as this is a subset of revision for all-causes and wide confidence intervals were already observed for that analysis. It is also important to mention this NJR analysis study is of an observational study design which has inherent limitations. Nonetheless, this is the most feasible study design to answer this research question requiring use of a large data set due to revision being a rare outcome. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Objectives. Total hip replacement (THR) is one of the most successful and cost-effective interventions in orthopaedic surgery. Dislocation is a debilitating complication of THR and managing an unstable THR constitutes a significant clinical challenge. Stability in THR is multifactorial and is influenced by surgical, patient and implant related factors. It is established that larger diameter femoral heads have a wider impingement-free range of movement and an increase in jump distance, both of which are relevant in reducing the risk of dislocation. However, they can generate higher frictional torque which has led to concerns related to increased wear and loosening. Furthermore, the potential for taper corrosion or trunnionosis is also a potential concern with larger femoral heads, particularly those made from cobalt-chrome. These concerns have meant there is hesitancy among surgeons to use larger sized heads. This study presents the comparison of clinical outcomes for different head sizes (28mm, 32mm and 36mm) in primary THR for 10,104 hips in a single centre. Methods. A retrospective study of all consecutive patients who underwent primary THR at our institution between 1st April 2003 and 31st Dec 2019 was undertaken. Institutional approval for this study was obtained. Demographic and surgical data were collected. The primary outcome measures were all-cause revision, revision for dislocation, and all-cause revision excluding dislocation. Continuous descriptive statistics used means, median values, ranges, and 95% confidence intervals where appropriate. Kaplan-Meier survival curves were used to estimate time to revision. Cox proportional hazard regression analysis was used to compare revision rates between the femoral head size groups. Adjustments were made for age at surgery, gender, primary diagnosis, ASA score, articulation type, and fixation method. Results. 10,104 primary THRs were included; median age 68.6 years with 61.5% females. A posterior approach was performed in 71.6%. There were 3,295 hips with 28 mm heads (32.6%), 4,858 (48.1%) with 32 mm heads and 1,951 (19.3%) with 36 mm heads. Overall rate of revision was 1.7% with the lowest rate recorded for the 36mm group (2.7% vs. 1.3% vs. 1.1%). Cox regression analysis showed a decreased risk of all-cause revision for 32mm & 36mm head sizes as compared to 28mm; this was statistically significant for the 32mm group (p = 0.01). Risk of revision for dislocation was significantly reduced in both 32mm (p = 0.03) and 36mm (p = 0.03) head sizes. Analysis of all cause revision excluding dislocation showed no significant differences between head sizes. Conclusion. There was a significantly reduced risk of revision for all causes, but particularly revision for dislocation with larger head sizes (36mm & 32mm vs. 28mm). Concerns regarding increased risk of early revision for aseptic loosening, polyethylene wear or taper corrosion with larger heads appear to be unfounded in this cohort of 10,104 patients with a mean of 6.0-year follow-up. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Cannulated hip screws are frequently used in the management of hip fractures. There have been concerns over the failure rate of the technique and the outcomes of those that subsequently require conversion to total hip replacement (THR). This study utilised a database of over 600 cannulated hip screw (CHS) fixations performed over a 14-year period and followed up for a minimum of one year (1-14). We identified 57 cases where a conversion to THR took place (40 females, 17 males, mean age: 71.2 years). Patient demographics, original mechanism of injury, fracture classification, reason for fixation failure, time until arthroplasty, implant type and post-arthroplasty complications were recorded. Clinical outcomes were measured using the Oxford Hip Score. The failure rate of cannulated screw treatment was 9.4% and the mean time from initial fixation to arthroplasty was 15.4 (16.5) months. Thirty six fractures were initially undisplaced and 21 were displaced. As one might expect the displaced cases tended to be younger but this didn't reach statistical significance [66.5(14.3) vs 72.7(13.1), p=0.1]. The commonest causes of failure were non-union (25 cases, 44%) and avascular necrosis (17 cases, 30%). Complications after THR consisted of one leg length discrepancy and one peri-prosthetic fracture. The mean Oxford score pre-arthroplasty was 12.2 (8.4), improving to 38.4 (11.1) at one-year. Although the pre op Oxford scores tended to be lower in patients with undisplaced fractures and higher ASA scores, the improvement was the same whatever the pre-op situation. The one-year Oxford score and the improvement in score are comparable to those seen in the literature for THR in general. In conclusion, CHS has a high success rate and where salvage arthroplasty is required it can provide good clinical outcomes with low complication rates

There is controversy regarding the effect of different approaches on recovery after THR. Collecting detailed relevant data with satisfactory compliance is difficult. Our retrospective observational multi-center study aimed to find out if the data collected via a remote coaching app can be used to monitor the speed of recovery after THR using the anterolateral (ALA), posterior (PA) and the direct anterior approach (DAA). 771 patients undergoing THR from 13 centers using the moveUP platform were identified. 239 had ALA, 345 DAA and 42 PA. There was no significant difference between the groups in the sex of patients or in preoperative HOOS Scores. There was however a significantly lower age in the DAA (64,1y) compared to ALA (66,9y), and a significantly lower Oxford Hip Score in the DAA (23,9) compared to PA(27,7). Step count measured by an activity tracker, pain killer and NSAID use was monitored via the app. We recorded when patients started driving following surgery, stopped using crutches, and their HOOS and Oxford hip scores at 6 weeks. Overall compliance with data request was 80%. Patients achieved their preoperative activity level after 25.8, 17,7 and 23.3 days, started driving a car after 33.6, 30.3 and 31.7 days, stopped painkillers after 27.5, 20.2 and 22.5 days, NSAID after 30.3, 25.7, and 24.7 days for ALA, DAA and PA respectively. Painkillers were stopped and preoperative activity levels were achieved significantly earlier favoring DAA over ALA. Similarly, crutches were abandoned significantly earlier (39.9, 29.7 and 24.4 days for ALA, DAA and PA respectively) favoring DAA and PA over ALA. HOOS scores and Oxford Hip scores improved significantly in all 3 groups at 6 weeks, without any statistically significant difference between groups in either Oxford Hip or HOOS subscores. No final conclusion can be drawn as to the superiority of either approach in this study but the remote coaching platform allowed the collection of detailed data which can be used to advise patients individually, manage expectations, improve outcomes and identify areas for further research

Abstract. BACKGROUND. Hemi-arthroplasty (HA) as a treatment for fractured neck of femur has slightly increased since 2019 and remarkably after the COVID pandemic. The main drawback of the treatment is ongoing cartilage deterioration that may require revision to THR. OBJECTIVE. This study assessed cartilage surface damage in hip HA by reproducing anatomical motion and loading conditions in a hip simulator. METHODS. Experimental design. HA tests were conducted using porcine acetabula and CoCr femoral heads. Five groups (n=4) were included: a control group comprising natural tissue and four HA groups where the acetabula were paired with metal heads to allow radial clearance (RC) classed as small (RC<0.6mm), large (2mm<RC<4mm), extra-large (4mm<RC), and oversized (RC<−0.6mm). Tests were carried out in an anatomical hip simulator that reproduced a simplified twin peak gait cycle, adapted for porcine hip joints, from the ISO 14242 standard for wear of THR prostheses (peak load of 900N). The test length was 6 hours, with photogrammetry taken at 1-hour intervals. Ringers solution was used as a lubricant. RESULTS. No changes were observed in the control group. However, cartilage surface changes were observed in all hemi-arthroplasty groups. Discolouration on the cartilage surface was noticeable at the posterior-superior part of the acetabulum after 1-hour (extra-large and oversized groups). Damage severity and location were characteristic of each clearance group. Of all the groups, the oversized group showed more significant damage. No labrum separation was seen after the simulation. CONCLUSIONS. These results are relevant to understand the effect of femoral head clearance on cartilage damage risk after HA. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Abstract. Objectives. Impingement in total hip replacements (THRs), including bone-on-bone impingement, can lead to complications such as dislocation and loosening. The aim of this study was to investigate how the location of the anterior inferior iliac spine (AIIS) affected the range of motion before impingement. Methods. A cohort of 25 CT scans (50 hips) were assessed and nine hips were selected with a range of AIIS locations relative to the hip joint centre. The selected CT Scans were converted to solid models (ScanIP) and THR components (DePuy Synthes) were virtually implanted (Solidworks). Flexion angles of 100⁰, 110⁰, and 120⁰ were applied to the femur, each followed by internal rotation to the point of impingement. The lateral, superior and anterior extent of the AIIS from the Centre of Rotation (CoR) of the hip was measured and its effect on the range of motion was recorded. Results. There was found to be a significant (p<0.05) inverse relationship between the ROM of the THR and the lateral measure of the AIIS. Of the three measures, the lateral AIIS measure showed the strongest relationship with ROM to impingement (R=0.73) with the anterior and superior measures resulting in R values of 0.41 and 0.56 respectively. For every millimetre lateral the AIIS location, there was typically a loss of 1.2° of range of motion. With increasing lateralisation, the AIIS was positioned more directly over the femur, thereby reducing the ROM in the THR during high flexion positions. No soft tissue was included in the models which would have affected the ROM. Conclusions. The results from this study have shown that the lateral measure of the AIIS could be a predictor for bone-on-bone impingement. To build confidence, wider study of AIIS location variation is needed, as well as analysis under impingement prone activities of daily living. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

The Hospital (Trust) guidelines generally recommend 40mg of Low molecular weight heparin (LMWH) twice daily (BD) for all patients over 100kg for those undergoing total hip (THR) and knee replacements (TKR) respectively. British National Formulary (BNF) recommends 40mg of LMWH once daily (OD) for all patients regardless of their overall weight or body mass index (BMI). We evaluated the outcome of prophylactic LMWH dosage for patients undergoing THR and TKR by monitoring surgery related venous-thromboembolic events up to a minimum of three months after surgery. A retrospective audit was carried out after obtaining institutional approval and all consecutive elective patients weighing over 100kg and undergoing THR and TKR were included. All patients were followed up for a minimum of 3 months after their operation to investigate the dose of prophylactic LMWH received, and whether they had developed any venous thromboembolic events (VTE) post operatively. This was done using a combination of electronic notes, drug charts and deep venous thrombosis (DVT) or computed tomography pulmonary angiogram (CTPA) reports on the hospital/trust database. A total of 53 patients underwent elective THR (18) and TKR (35) between the period of March 2017 and September 2017. Forty-four patients received 40 mg OD and 9 patients had 40 mg BD. None of the patients developed a confirmed DVT or pulmonary embolism in the 3 months following surgery regardless of the dose received. We demonstrate that there is no clinical benefit in having patients over 100kg on twice daily LMWH with the aim of preventing post-op thromboembolic complications. This conclusion is in line with the BNF recommendations for VTE prophylaxis

Hip precautions are currently practiced in three-quarters of trauma hospitals in the UK, despite national recommendations from the ‘Blue Book’ not stating it as a requirement. Valuable therapist time is utilised alongside the need for specialised equipment, which can potentially delay discharge whilst it is being arranged. Objective of this study was to explore the current practice of the use of hip precautions on discharge following hemiarthroplasty for hip fractures. To also explore whether they are necessary and to identify areas for improvement to benefit patient care overall. Online survey distributed to various Trauma and Orthopaedic Departments across the UK. Survey was available over a 4-month period, collecting 55 responses overall. Majority of responses were from trauma and orthopaedic consultants who were aware of the ‘Blue Book’ recommendations. The majority of trusts who responded did not practice hip precautions and did not feel this increased the risk of dislocations on discharge. Recommendations included integration of hip precautions in the post-op advice in coordination with the physiotherapist and information leaflets on discharge regarding hip precautions. Hip precautions were not commonly practiced, for reasons including patient compliance and the inherently stable procedure of a hemiarthroplasty compared to a THR, reducing the need for hip precautions. Hip precautions are not widely regarded as a useful practice for post-hip hemiarthroplasty, viewed as utilising more resources and increasing costs and risk due to increased hospital stay. Thus, this potentially delays discharge overall. A consistent approach should be implemented in treating patients post-hip hemiarthroplasty

Total hip replacement (THR) is indicated for patients with osteoarthritis where conservative treatment has failed. Metal alloys used in THR implants such as cobalt-chromium (CoCr) have been known to cause pro-inflammatory reactions in patients, therefore leading to the need for costly revision surgery. This study therefore aimed to investigate the role of TLR4 in the activation of a human osteoblast model in response to CoCr particles in vitro. Human osteoblasts (MG-63 cell line) were seeded at a density of 100,000 cells and treated with 0.5, 5, 50mm3 CoCr particles per cell for 24-hours. Trypan blue and the XTT Cell Proliferation Kit II were then used in conjunction with the cells to assess CoCr-induced cytotoxicity. Cells were pre-treated with a commercially available TLR4-specific small molecule inhibitor (CLI-095) for 6 hours. Untreated cells were used as a negative control and lipopolysaccharide (LPS) was used as a positive control. Following treatment the cell supernatant was collected and used for enzyme-linked immunosorbant assay (ELISA) to measure the secretion of interleukin-8 (IL-8), CXCL10, and interleukin-6 (IL-6). Trypan blue and XTT analysis showed that there was no significant changes to cell viability or proliferation at any dose used of CoCr after 24 hours. There was a significant increase in protein secretion of IL-8 (p<0.001), CXCL10 (p<0.001), and IL-6 (p<0.001) in the cells which received the highest dosage of CoCr. This pro-inflammatory secretory response was ameliorated by TLR4 blockade (p<0.001). CoCr particles are not cytotoxic to osteoblasts but they do induce pro-inflammatory changes as characterised by increased secretion of chemokines IL-8, CXCL10, and IL-6. These responses occur via a TLR4-mediated pathway and upon inhibition they can be effectively ameliorated. This is particularly important as TLR4 could be a potential target for pharmacological intervention used in patients experiencing immunological reactions to metal implant debris

Non-optimal clinical alignment of components in total hip replacements (THRs) may lead to edge loading of the acetabular cup liner. This has the potential to cause changes to the liner rim not accounted for in standard wear models. A greater understanding of the material behaviours could be beneficial to design and surgical guidance for THR devices. The aim of this research was to combine finite element (FE) modelling and experimental simulation with microstructural assessment to examine material behaviour changes during edge loading. A dynamic deformable FE model, matching the experimental conditions, was created to simulate the stress strain environment within liners. Five liners were tested for 4Mc (million cycles) of standard loading (ISO14242:1) followed by 3Mc of edge loading with dynamic separation (ISO14242:4) in a hip simulator. Microstructural measurements by Raman spectroscopy were taken at unloaded and highly loaded rim locations informed by FE results. Gravimetric and geometric measurements were taken every 1Mc cycles. Under edge loading, peak Mises stress and plastic deformation occur below the surface of the rim during heel strike. After 7Mc, microstructural analysis determined edge loaded regions had an increased crystalline mass fraction compared to unloaded regions (p<0.05). Gravimetric wear rates of 12.5mm. 3. /Mc and 22.3mm. 3. /Mc were measured for standard and edge loading respectively. A liner penetration of 0.37mm was measured after 7Mc. Edge loading led to an increase in gravimetric wear rate indicating a different wear mechanism is occurring. FE and Raman results suggest that changes to material behaviour at the rim could be possible. These methods will now be used to assess more liners and over a larger number of cycles. They have potential to explore the impact of edge loading on different surgical and patient variables

First-time revision acetabular components have a 36% re-revision rate at 10 years in Australia, with subsequent revisions known to have even worse results. Acetabular component migration >1mm at two years following revision THA is a surrogate for long term loosening. This study aimed to measure the migration of porous tantalum components used at revision surgery and investigate the effect of achieving press-fit and/or three-point fixation within acetabular bone. Between May 2011 and March 2018, 55 patients (56 hips; 30 female, 25 male) underwent acetabular revision THR with a porous tantalum component, with a post-operative CT scan to assess implant to host bone contact achieved and Radiostereometric Analysis (RSA) examinations on day 2, 3 months, 1 and 2 years. A porous tantalum component was used because the defects treated (Paprosky IIa:IIb:IIc:IIIa:IIIb; 2:6:8:22:18; 13 with pelvic discontinuity) were either deemed too large or in a position preventing screw fixation of an implant with low coefficient of friction. Press-fit and three-point fixation of the implant was assessed intra-operatively and on postoperative imaging. Three-point acetabular fixation was achieved in 51 hips (92%), 34 (62%) of which were press-fit. The mean implant to host bone contact achieved was 36% (range 9-71%). The majority (52/56, 93%) of components demonstrated acceptable early stability. Four components migrated >1mm proximally at two years (1.1, 3.2, 3.6 and 16.4mm). Three of these were in hips with Paprosky IIIB defects, including 2 with pelvic discontinuity. Neither press-fit nor three-point fixation was achieved for these three components and the cup to host bone contact achieved was low (30, 32 and 59%). The majority of porous tantalum components had acceptable stability at two years following revision surgery despite treating large acetabular defects and poor bone quality. Components without press-fit or three-point fixation were associated with unacceptable amounts of early migration