Our understanding of pre-arthritic hip disease has evolved tremendously but challenges remain in categorizing diagnosis, which ultimately impacts choice of treatments and clinical outcomes. This study aims to report patient reported outcome measures (PROMs) comparing four different condition groups within hip preservation surgery by a group of fellowship-trained surgeons.

From 2018 to 2021, 380 patients underwent hip preservation surgery at our center and were classified into five condition groups: dysplasia: 82 (21.6%), femoro-acetabular impingement (FAI): 173 (45.4%), isolated labral tear: 103 (27.1%), failed hip preservation: 20 (5.3%) and history of childhood disease/other: 2 (0.5%). International hip outcomes Tool 12 (IHOT-12), numeric pain score and patient-reported outcomes measurement information system (PROMIS) were collected pre-operatively and at 3 months and 1 year post-operatively, with 94% and 82% follow-up rate respectively.

Arthroscopy (75.5%) was the most common procedure followed by peri-acetabular osteotomy (PAO) (22.4%) and surgical dislocation (2.1%). Re-operation rate were respectively 18.3% (15), 5.8% (10), 4.9% (5), 30% (6) and 0%. There were 36 re-operations in the cohort, 14 (39%) for unintended consequences of initial surgery, 10 (28%) for mal-correction leading to a repeat operation, 8 (22%) progression of arthritis, and 4 (11%) for incorrect initial diagnosis/intervention. Most common re-operations were hardware removal 31% (7 PAO, 3 surgical hip dislocation and 1 femoral de-rotational osteotomy), arthroscopy 31% (11) and arthroplasty 28% (10). All groups had significant improvements in their IHOT-12 as well as PROMIS physical and numerical pain scales, except those with failed hip preservation. Dysplasia group showed a slower recovery.

Overall, this study demonstrated a clear relation between the condition groups, their respective intervention and the significant improvements in PROMs with isolated labral pathology being a valid diagnosis. Establishing tertiary referral centers for hip preservation and longer follow-up is needed to monitor the overall survivorship of these various procedures.

Traditional radiographic criteria might underestimate or fail to detect subtle types of acetabular dysplasia. Acetabular sector angles (ASA) can measure the degree of anterior and posterior coverage of the femoral head on computed tomography (CT). This study aims to determine ASA values at different axial levels in a cohort of (1) asymptomatic, high-functioning hips without underlying hip pathology (controls); and (2) symptomatic, dysplastic hips that underwent periacetabular osteotomy (PAO). Thereby, we aimed to define CT-based thresholds for hip dysplasia and its subtypes.

This is an IRB approved cross-sectional study of 51 high functioning, asymptomatic patients (102 hips) (Oxford Hip Score >43), without signs of osteoarthritis (Tönnis grade≤1), who underwent a CT scan of the pelvis (mean age: 52.1±5.5 years; 52.9% females); and 66 patients (72 hips) with symptomatic hip dysplasia treated with peri-acetabular osteotomy (PAO) (mean age: 29.3±7.3 years; 85.9% females). Anterior and posterior acetabular sector angles (AASA & PASA) were measured by two observers at three CT axial levels to determine equatorial, intermediate, and proximal ASA. Inter- and intra-observer reliability coefficient was high (between 0.882–0.992). Cut-off values for acetabular deficiency were determined based on Receiver Operating Characteristic (ROC) curve analysis, area under the curve (AUC) was calculated.

The dysplastic group had significantly smaller ASAs compared to the Control Group, AUC was the highest at the proximal and intermediate PASA. Controls had a mean proximal PASA of 162°±17°, with a cut-off value for dysplasia of 137° (AUC: 0.908). At the intermediate level, the mean PASA of controls was 117°±11°, with a cut-off value of 107° (AUC 0.904). Cut-off for anterior dysplasia was 133° for proximal AASA (AUC 0.859) and 57° for equatorial AASA (AUC 0.868). Cut-off for posterior dysplasia was 102° for intermediate PASA (AUC 0.933).

Measurement of ASA on CT is a reliable tool to identify dysplastic hips with high diagnostic accuracy. Posterior ASA less than 137° at the proximal level, and 107° at the intermediate level should alert clinicians of the presence of dysplasia.

Aims

Spinopelvic characteristics influence the hip’s biomechanical behaviour. However, to date there is little knowledge defining what ‘normal’ spinopelvic characteristics are. This study aims to determine how static spinopelvic characteristics change with age and ethnicity among asymptomatic, healthy individuals.

Aims

The aims of this study were to determine the incidence and factors for developing periprosthetic joint infection (PJI) following hemiarthroplasty (HA) for hip fracture, and to evaluate treatment outcome and identify factors associated with treatment outcome.

The study of spinopelvic anatomy and movement has received great interest as these characteristics influence the biomechanical behavior (and outcome) following hip arthroplasty. However, to-date there is little knowledge of what “normal” is and how this varies with age. This study aims to determine how dynamic spino-pelvic characteristics change with age, with well-functioning hips and assess how these changes are influenced by the presence of hip arthritis.

This is an IRB-approved, cross-sectional, cohort study; 100 volunteers (asymptomatic hips, Oxford-Hip-sore>45) [age:53 ± 17 (24-87) years-old; 51% female; BMI: 28 ± 5] and 200 patients with end-stage hip arthritis [age:56 ± 19 (16-89) years-old; 55% female; BMI:28 ± 5] were studied. All participants underwent lateral spino-pelvic radiographs in the standing and deep-seated positions to determine maximum hip and spine flexion. Parameters measured included lumbar-lordosis (LL), pelvic incidence, pelvic-tilt (PT), pelvic-femoral angles (PFA). Lumbar flexion (ΔLL), hip flexion (ΔPFA) and pelvic movement (ΔPT) were calculated. The prevalence of spinopelvic imbalance (PI–LL>10?) was determined.

There were no differences in any of the spino-pelvic characteristics or movements between sexes. With advancing age, standing LL reduced and standing PT increased (no differences between groups). With advancing age, both hip (4%/decade) and lumbar (8%/decade) flexion reduced (p<0.001) (no difference between groups). ΔLL did not correlate with ΔPFA (rho=0.1). Hip arthritis was associated with a significantly reduced hip flexion (82 ±;22? vs. 90 ± 17?; p=0.003) and pelvic movements (1 ± 16? vs. 8 ± 16?; p=0.002) at all ages and increased prevalence of spinopelvic imbalance (OR:2.6; 95%CI: 1.2-5.7).

With aging, the lumbar spine loses its lumbar lordosis and flexion to a greater extent that then the hip and resultantly, the hip's relative contribution to the overall sagittal movement increases. With hip arthritis, the reduced hip flexion and the necessary compensatory increased pelvic movement is a likely contributor to the development of hip-spine syndrome and of spino-pelvic imbalance.

In 2007, the National Hip Fracture Database (NHFD) was conceived in the United Kingdom (UK) as a national audit aiming to improve hip fracture care across the country. It now represents the world's largest hip fracture registry. The purpose of the NHFD is to evaluate aspects of best practice for hip fracture care, at an institutional level, that reflect the evidence-based clinical guidelines and quality standards developed by the National Institute for Health and Care Excellence. No national program currently exists, equivalent to the NHFD, in Canada despite evidence suggesting that national audit programs can significantly improve patient outcomes. The purpose of this study was to evaluate aspects of best practice for hip fractures at our Canadian academic tertiary referral center using the Key Performance Indicators (KPI) and benchmarks used by the NHFD. In doing so, we aimed to compare our performance to other hospitals contributing to the NHFD database.

A retrospective cohort study was conducted on consecutive patients who presented to our Canadian center for surgical management of a hip fracture between August 2019 to September 2020. Fracture types included intertrochanteric, subtrochanteric, and femoral neck fractures treated with either surgical fixation or arthroplasty. Cases were identified from the affiliate institute's Operatively Repaired Fractures Database (ORFD). The ORFD prospectively collects patient-level data extracted from electronic medical records, operating room information systems, and from patients’ discharge summaries. All applicable data from our database were compared to the established KPI and benchmarks published by the NHFD that apply to the Canadian healthcare system.

Six hundred and seven patients’ data (64.5% female) were extracted from the ORFD, mean age 80.4 ± 13.3 years. The NHFD contains data from 63,284 patients across the entire UK. The affiliate institute performed inferiorly compared to the NHFD for two KPIs: prompt surgery (surgery by the day following presentation with hip fracture, 52.8% vs. 69%) and prompt mobilization after surgery (mobilized out of bed by the day after operation, 43.0% vs. 81.0%). However, more patients at the affiliate institute were not delirious when tested postoperatively (89.6% vs. 68.4%). There was no significant difference in the average length of stay (12.23 days versus 13.5 days) or in 30-day mortality rate (8.4% versus 8.3%).

More than half of all KPI's and benchmarks for patients receiving a hip fracture surgery at our tertiary referral center in Canada ranked significantly lower than patients receiving a hip fracture surgery in the UK. These findings indicate that perhaps a national audit program should be implemented in Canada to improve aspects of hip fracture care, at an institutional level. Following evidence-based clinical guidelines and using standardized benchmarks would encourage change and foster improvement across Canadian centres when necessary.

Adverse spinopelvic characteristics (ASC) have been associated with increased dislocation risk following primary total hip arthroplasty (THA). A stiff lumbar spine, a large posterior standing tilt when standing and severe sagittal spinal deformity have been identified as key risk factors for instability. It has been reported that the rate of dislocation in patients with such ASC may be increased and some authors have recommended the use of dual mobility bearings or robotics to reduce instability to within acceptable rates (<2%).

The aims of the prospective study were to 1: Describe the true incidence of ASC in patients presenting for a THA 2. Assess whether such characteristics are associated with greater symptoms pre-THA due to the concomitant dual pathology of hip and spine and 3. Describe the early term dislocation rate with the use of ≤36mm bearings.

This is an IRB-approved, two-center, multi-surgeon, prospective, consecutive, cohort study of 220 patients undergoing THA through anterolateral- (n=103; 46.8%), direct anterior- (n=104; 27.3%) or posterior- approaches (n=13; 5.9%). The mean age was 63.8±12.0 years (range: 27.7-89.0 years) and the mean BMI 28.0±5.0 kg/m² (range: 19.4-44.4 kg/m²). There were 44 males (47.8%) and 48 females (52.2%). The mean follow-up was 1.6±0.5 years. Overall, 54% of femoral heads was 32 mm, and 46% was 36mm.

All participants underwent lateral spinopelvic radiographs in the standing and deep-flexed seated positions were taken to determine lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic-femoral angle (PFA) and pelvic incidence (PI) in both positions. Spinal stiffness was defined as lumbar flexion <20° when transitioning between the standing and deep-seated position; adverse standing PT was defined as >19° and adverse sagittal lumbar balance was defined as mismatch between standing PI and LL >10°.

Pre-operative patient reported outcomes was measured using the Oxford Hip Score (OHS) and EuroQol Five-Dimension questionnaire (EQ-5D). Dislocation rates were prospectively recorded. Non-parametric tests were used, significance was set at p<0.05.

The prevalence of PI-LL mismatch was 22.1% (43/195) and 30.4% had increased standing PT (59/194). The prevalence of lumbar stiffness was 3.5% (5/142) and these patients had all three adverse spinopelvic characteristics (5/142; 3.5%).

There was no significant difference in the pre-operative OHS between patients with (20.7±7.6) and patients without adverse spinopelvic characteristics (21.6±8.7; p=0.721), nor was there for pre-operative EQ5D (0.651±0.081 vs. 0.563±0.190; p=0.295).

Two patients sustained a dislocation (0.9%): One in the lateral (no ASC) and one in the posterior approaches, who also exhibited ASC pre-operatively.

Sagittal lumbar imbalance, increased standing spinal tilt and spinal stiffness are not uncommon among patients undergoing THA. The presence of such characteristics is not associated with inferior pre-operative PROMs. However, when all characteristics are present, the risk of instability is increased. Patients with ASC treated with posterior approach THA may benefit from the use of advanced technology due to a high risk of dislocation. The use of such technology with the anterior or lateral approach to improve instability is to date unjustified as the rate of instability is low even amongst patients with ASCs.

With an ageing population and an increasing number of primary arthroplasties performed, the revision burden is predicted to increase. The aims of this study were to 1. Determine the revision burden in an academic hospital over a 11-year period; 2. identify the direct hospital cost associated with the delivery of revision service and 3. ascertain factors associated with increased cost.

This is an IRB-approved, retrospective, single tertiary referral center, consecutive case series. Using the hospital data warehouse, all patients that underwent revision hip or knee arthroplasty surgery between 2008-2018 were identified. 1632 revisions were identified (1304 patients), consisting of 1061 hip and 571 knee revisions. The majority of revisions were performed for mechanical-related problems and aseptic loosening (n=903; 55.3%); followed by periprosthetic joint infection (n=553; 33.9%) and periprosthetic fractures (176; 10.8%). Cost and length of stay was determined for all patient. The direct in-hospital costs were converted to 2020 inflation-adjusted Canadian dollars. Several patients- (age; gender; HOMR- and ASA-scores; Hemoglobin level) and surgical- (indication for surgery; surgical site) factors were tested for possible associations.

The number of revisions increased by 210% in the study period (2008 vs. 2018: 83 vs. 174). Revision indications changed over study period; with prevalence of fracture increasing by 460% (5 in 2008 vs. 23 in 2018) with an accompanying reduction in mechanical-related reasons, whilst revisions for infection remained constant. The mean annual cost over the entire study period was 3.9 MMCAD (range:2.4–5.1 MMCAD). The cost raised 150% over the study period from 2.4 MMCAD in 2008 to 3.6 MMCAD. Revisions for fractured had the greatest length of stay, the highest mean age, HOMR-score, ASA and cost associated with treatment compared to other revision indications (p < 0 .001). Patient factors associated with cost and length of stay included ASA- and HOMR-scores, Charlson-Comorbidity score and age.

The revision burden increased 1.5-fold over the years and so has the direct cost of care delivery. The increased cost is primarily related to the prolonged hospital stay and increased surgical cost. For tertiary care units, these findings indicate a need to identify strategies on improving efficiencies whilst improving the quality of patient care (e.g. efficient ways of reducing acute hospital stay) and reducing the raise of the economic burden on a publicly funded health system.

The presence of hip osteoarthritis is associated with abnormal spinopelvic characteristics. This study aims to determine whether the pre-operative, pathological spinopelvic characteristics “normalize” at 1-year post-THA.

This is a prospective, longitudinal, case-control matched cohort study. Forty-seven patients underwent pre- and post- (at one-year) THA assessments. This group was matched (age, sex, BMI) with 47 controls/volunteers with well-functioning hips. All participants underwent clinical and radiographic assessments including lateral radiographs in standing, upright-seated and deep-flexed-seated positions. Spinopelvic characteristics included change in lumbar lordosis (ΔLL), pelvic tilt (ΔPT) and hip flexion (pelvic-femoral angle, ΔPFA) when moving from the standing to each of the seated positions. Spinopelvic hypermobility was defined as ΔPT>30° between standing and upright-seated positions.

Pre-THA, patients illustrated less hip flexion (ΔPFA −54.8°±17.1° vs. −68.5°± 9.5°, p<0.001), greater pelvic tilt (ΔPT 22.0°±13.5° vs. 12.7°±8.1°, p<0.001) and greater lumbar movements (ΔLL −22.7°±15.5° vs. −15.4°±10.9°, p=0.015) transitioning from standing to upright-seated. Post-THA, these differences were no longer present (ΔPFApost −65.8°±12.5°, p=0.256; ΔPTpost 14.3°±9.5°, p=0.429; ΔLLpost −15.3°±10.6°, p=0.966). The higher prevalence of pre-operative spinopelvic hypermobility in patients compared to controls (21.3% vs. 0.0%; p=0.009), was not longer present post-THA (6.4% vs. 0.0%; p=0.194). Similar results were found moving from standing to deep-seated position post-THA.

Pre-operative, spinopelvic characteristics that contribute to abnormal mechanics can normalize post-THA following improvement in hip flexion. This leads to patients having the expected hip-, pelvic- and spinal flexion as per demographically-matched controls, thus potentially eliminating abnormal mechanics that contribute to the development/exacerbation of hip-spine syndrome.

In patients admitted to hospital with a hip fracture, urinary issues are common. Despite guidelines that recommend avoiding foley catheter usage when possible, it remains a common part of perioperative care. To date, there is no prospective data on the safety and satisfaction associated with catheter use in such cohort. The aim of this study was to evaluate the satisfaction of patients when using a foley catheter while they await surgery for their fractured hip and the safety associated with catheter use.

In our prospectively collected database, 587 patients were admitted to our tertiary care center over a 1 year period. Most patients (328) were catheterized within the first 24h of admission, primarily inserted in ED. Of these patients, 119 patients (61 catheterized and 58 noncatheterized) completed a questionnaire about their perioperative management with foley catheter usage administered on day 1 of admission. This was used to determine satisfaction of catheter use (if catheterized) and pain levels (associated with catheterized or associated with transferring/voiding if not catheterized). Adverse effects related with catheter use included urinary tract infection (UTI) and post-operative urinary retention (POUR).

Ninety-five percent of patients found the catheter to be convenient. Only 5% of patients reported any pain with catheter use. On the contrary, 47.5% of non-catheterized patients found it difficult to move to the bathroom and 30.4% found it difficult to urinate. Catheterized patients had significative less pain than uncatheterized patients (0.62/10 vs 2.45/10 respectively, p < 0 .001). The use of nerve block reduced pain levels amongst catheterized patients but was not associated with reduced pain levels or satisfaction amongst non-catheterized patients. The use of catheter was not associated with increased risk of UTI(17.5% in the catheterized vs 13.3% in the non-catheterized, p = 0.541) or POUR (6.8% in the catheterized vs 11.1% in the non-catheterized, p = 0.406).

This study illustrates the benefits and safety associated with the use of urinary catheters in the pre-operative period amongst hip fractures. The use of catheters was associated with reduced pain and satisfaction without increasing post-operative UTI or POUR. These findings suggest that pre-operative catheter use is associated with less pain and more satisfaction for patients awaiting hip surgery and whom other measures, such as nerve blocks, are unlikely to reduce the discomfort associated with the mobility required to void. A prospective randomized control study could lead to a more evidence based approach for perioperative foley catheter usage in hip fracture patients.

Short cementless femoral stems are increasingly popular as they allow for less dissection for insertion. Use of such stems with the anterior approach (AA) may be associated with considerable per-operative fracture risk. This study's primary aim was to evaluate whether patient-specific femoral- and pelvic- morphology and surgical technique, influence per-operative fracture risk. In doing so, we aimed to describe important anatomical thresholds alerting surgeons.

This is a single-center, multi-surgeon retrospective, case-control matched study. Of 1145 primary THAs with a short, cementless stem inserted via the AA, 39 periprosthetic fractures (3.4%) were identified. These were matched for factors known to increase fracture risk (age, gender, BMI, side, Dorr classification, stem offset and indication for surgery) with 78 THAs that did not sustain a fracture. Radiographic analysis was performed using validated software to measure femoral- (canal flare index [CFI], morphological cortical index [MCI], calcar-calcar ratio [CCR]) and pelvic- (Ilium-ischial ratio [IIR], ilium overhang, and ASIS to greater trochanter distance) morphologies and surgical technique (% canal fill). Multivariate and Receiver-Operator Curve (ROC) analysis was performed to identify predictors of fracture.

Femoral factors that differed included CFI (3.7±0.6 vs 2.9±0.4, p3.17 and II ratio>3 (OR:29.2 95%CI: 9.5–89.9, p<0.001).

Patient-specific anatomical parameters are important predictors of fracture-risk. When considering the use of short stems via the AA, careful radiographic analysis would help identify those at risk in order to consider alternative stem options.

A stiff spine leads to increased demand on the hip, creating an increased risk of total hip arthroplasty (THA) dislocation. Several authors propose that a change in sacral slope of ≤10° between the standing and relaxed-seated positions (ΔSSstanding→relaxed-seated) identifies a patient with a stiff lumbar spine and have suggested use of dual-mobility bearings for such patients. However, such assessment may not adequately test the lumbar spine to draw such conclusions. The aim of this study was to assess how accurately ΔSSstanding→relaxed-seated can identify patients with a stiff spine.

This is a prospective, multi-centre, consecutive cohort series. Two-hundred and twenty-four patients, pre-THA, had standing, relaxed-seated and flexed-seated lateral radiographs. Sacral slope and lumbar lordosis were measured on each functional X-ray. ΔSSstanding→relaxed-seated seated was determined by the change in sacral slope between the standing and relaxed-seated positions. Lumbar flexion (LF) was defined as the difference in lumbar lordotic angle between standing and flexed-seated. LF≤20° was considered a stiff spine. The predictive value of ΔSSstanding→relaxed-seated for characterising a stiff spine was assessed.

A weak correlation between ΔSSstanding→relaxed-seated and LF was identified (r2= 0.15). Fifty-four patients (24%) had ΔSSstanding→relaxed-seated ≤10° and 16 patients (7%) had a stiff spine. Of the 54 patients with ΔSSstanding→relaxed-seated ≤10°, 9 had a stiff spine. The positive predictive value of ΔSSstanding→relaxed-seated ≤10° for identifying a stiff spine was 17%.

ΔSSstanding→relaxed-seated ≤10° was not correlated with a stiff spine in this cohort. Utilising this simplified approach could lead to a six-fold overprediction of patients with a stiff lumbar spine. This, in turn, could lead to an overprediction of patients with abnormal spinopelvic mobility, unnecessary use of dual mobility bearings and incorrect targets for component alignment. Referring to patients ΔSSstanding→relaxed-seated ≤10° as being stiff can be misleading; we thus recommend use of the flexed-seated position to effectively assess pre-operative spinopelvic mobility.

Aims

The primary aim of this study was to determine the ten-year outcome following surgical treatment for femoroacetabular impingement (FAI). We assessed whether the evolution of practice from open to arthroscopic techniques influenced outcomes and tested whether any patient, radiological, or surgical factors were associated with outcome.

Short cementless femoral stems are increasingly popular as they allow for less dissection for insertion. Use of such stems with the anterior approach (AA) may be associated with considerable per-operative fracture risk. This study's primary aim was to evaluate whether patient-specific femoral- and pelvic- morphology and surgical technique, influence per-operative fracture risk. In doing so, we aimed to describe important anatomical thresholds alerting surgeons.

This is a single-centre, multi-surgeon retrospective, case-control matched study. Of 1145 primary THAs with a short, cementless stem inserted via the AA, 39 periprosthetic fractures (3.4%) were identified. These were matched for factors known to increase fracture risk (age, gender, BMI, side, Dorr classification, stem offset and indication for surgery) with 78 THAs that did not sustain a fracture. Radiographic analysis was performed using validated software to measure femoral- (canal flare index [CFI], morphological cortical index [MCI], calcar-calcar ratio [CCR]) and pelvic- (Ilium-ischial ratio [IIR], ilium overhang, and ASIS to greater trochanter distance) morphologies and surgical technique (% canal fill). Multivariate and Receiver-Operator Curve (ROC) analysis was performed to identify predictors of fracture.

Femoral factors that differed included CFI (3.7±0.6 vs 2.9±0.4, p<0.001) and CCR (0.5±0.1 vs 0.4±0.1, p=0.006). The mean IIR was higher in fracture cases (3.3±0.6 vs 3.0±0.5, p<0.001). % Canal fill was reduced in fracture cases (82.8±7.6 vs 86.7±6.8, p=0.007). Multivariate analysis and ROC analyses revealed a threshold CFI of 3.17 was predictive of fracture (sensitivity:84.6% / specificity:75.6%). Fracture risk was 29 times higher when patients had CFI>3.17 and II ratio>3 (OR:29.2 95%CI: 9.5–89.9, p<0.001).

Patient-specific anatomical parameters are important predictors of fracture-risk. When considering the use of short stems via the AA, careful radiographic analysis would help identify those at risk in order to consider alternative stem options.

Aims

The lateral centre-edge angle (LCEA) is a plain radiological measure of superolateral cover of the femoral head. This study aims to establish the correlation between 2D radiological and 3D CT measurements of acetabular morphology, and to describe the relationship between LCEA and femoral head cover (FHC).

Aims

Periacetabular osteotomy (PAO) is an established treatment for acetabular dysplasia. It has also been proposed as a treatment for patients with acetabular retroversion. By reviewing a large cohort, we aimed to test whether outcome is equivalent for both types of morphology and identify factors that influenced outcome.

Over 62,000 total hip arthroplasty (THA) cases are performed each year in Canada, with an estimated annual healthcare system cost of $1.4 billion and resulting in 4 billion tonnes of waste annually (6,600 tonnes per day). The aims of this study were 1) Assess satisfaction of current/standard set-up amongst different stakeholders. 2) Assess energy, economic and waste cost of current set up and apply lean methodology to improve efficiency 3. Design and test SLIM setup based on lean principles and its ability to be safely implemented into everyday practice.

A Needs Assessment Survey was circulated to OR nursing staff to assess the need for change in the current THA OR setup at an academic tertiary referral hospital. Through feedback, surgeon input, and careful analysis of current instrumentation, the “SLIM setup” was created. Standard instrument tray numbers for elective THA were reduced from 9 to 3 trays. Eighty patients were then randomised to either the standard or SLIM setup. Four staff arthroplasty surgeons each randomised 20 patients to either standard or SLIM setup. OR time, blood loss, 90-day complication rates, cost/case, instrument weight (kg/case), total waste in kg/case (non-recyclable), case set-up time, and number of times and number of extra trays required were compared between groups.

The majority of nursing staff demonstrated dissatisfaction with the current THA setup and felt current processes lacked efficiency. Use of the SLIM setup, was associated with the following savings in comparison to standard (Trays = −6 (720kg/case); Waste = −1.5 kg/case; Cost = − $560 ($50.00 × 6 trays + 10min saved × $26.00 /min OR setup time)). OR time, blood loss and 90-day complication rate were not statistically different (p >0.05); however, set up time was significantly shorter in comparison to standard. Extra instrumentation was opened in < 10% of cases.

A more minimalist approach to THA can be undertaken using the SLIM setup, potentially resulting in cost, energy and waste savings. Estimate savings of $560,000 and 1.65 tonnes reduction in waste per 1,000 THAs performed may be realised.

This matched cohort study aims to (a) assess differences in spinopelvic characteristics of patients having sustained a dislocation following THA and a control THA group without dislocation; (b) identify spinopelvic characteristics associated with risk of dislocation and; (c) propose an algorithm to define the optimum cup orientation for minimizing dislocation risk.

Fifty patients with a history of THA dislocation (29 posterior-, 21 anterior dislocations) were matched for age, gender, body mass index, index diagnosis, and femoral head size with 100 controls. All patients were reviewed and underwent detailed quasi-static radiographic evaluations of the coronal- (offset; center-of-rotation; cup inclination/anteversion) and sagittal- reconstructions (pelvic tilt, pelvic incidence, lumbar lordosis, pelvic-femoral-angle, cup ante-inclination). The spinopelvic balance (PI-LL), combined sagittal index (CSI= Pelvic-femoral-angle + Cup Anteinclination) and Hip-User-Index were determined. sagittal index (CSI= Pelvic-femoral-angle + Cup Anteinclination) and Hip-User-Index were determined. Parameters were compared between the two groups (2-group analysis) and between controls and per direction of dislocation (3-group analysis).

There were marginal coronal differences between the groups. Sagittal parameters (lumbar-lordosis, pelvic-tilt, CSI, PI-LL and Hip-User-Index) differed significantly. PI-LL (>10°) and standing pelvic tilt (>18°) were the strongest predictors of dislocation risk (sensistivity:70%/specificity:70%). All hips with a standing CSI<195° dislocated posteriorly and all with CSI>260° dislocated anteriorly. A CSI between 200–245° was associated with significantly reduced risk of dislocation (OR:6; 95%CI:2.5–15.0; p<0.001). In patients with unbalanced and/or rigid lumbar spine, standing CSI of 215–245° was associated with significantly reduced dislocation risk (OR:10; 95%CI:3.2–29.8; p<0.001).

PI-LL and standing pelvic-tilt determined from pre-operative, standing, lateral spinopelvic radiograph can be useful screening tools, alerting surgeons of patients at increased dislocation risk. Measurement of the pelvic-femoral angle pre-operatively provides valuable information to determine the optimum, cup orientation associated with reduced dislocation risk by aiming for a standing CSI of 200–245°.

Aims

The aim of this study was to radiologically evaluate the quality of cement mantle and alignment achieved with a polished tapered cemented femoral stem inserted through the anterior approach and compared with the posterior approach.

Surgical treatment options for Femoroacetabular impingement (FAI) includes both surgical dislocation and hip arthroscopy techniques. The primary aim of this study was to evaluate and compare the survivorship of arthroscopies (scope) and surgical dislocations (SD) at minimum 5-year follow-up. The secondary aim was to describe differences in functional outcomes between the 2 groups.

This was a retrospective, single surgeon, consecutive, case-series from a large tertiary care centre. We evaluated all surgeries that were performed between 2005 and 2011. Our institutional database was queried for any patient undergoing surgery for FAI (pincer (n=23), cam (n=306), or mixed (n=103) types). Patients with childhood pathologies i.e. Legg Calve Perthes and slipped capital femoral epiphysis were excluded. This resulted in 221 hips (169 males, 52 females) who underwent either SD (94, 42.5%) or scope (127, 57.5%). A manual chart review was completed to identify patients who sustained a complication, underwent revision surgery or progressed to a total hip arthroplasty (THA). In addition, we reviewed prospectively collected patient reported outcome measure (PROMs) using (SF12, HOOS, and UCLA). Survivorship outcome was described for the whole cohort and compared between the 2 surgical groups. PROMs between groups were compared using The Mann-Whitney U test and the survival between groups was assessed using the Kaplan-Meier Analysis and the Log-Rank Mantel Cox test. All analyses were performed in SPSS (IBM, v. 26.0).

The cohort included 110 SDs and 320 arthroscopies. The mean age of the whole cohort was 34±10; patients in the SD group (32±9) were younger compared to the arthroscopy group (39±10) (p<0.0001). There were 16 post-operative complications (similar between groups) and 77 re-operations (more common in the SD group (n=49) due to symptomatic metal work (n=34)). The overall 10-year survival was 91±3%. Survivorship was superior in the arthroscopy group at both 5- (96% (95%CI: 93 – 100)) and 8- years 94% (95%CI: 90 – 99%) compared to the SD Group (5-yr: 90% (95%CI: 83 – 98); 8-yr: 84% (95%CI:75 – 93)) (p=0.003) (Figure 1). On average HOOS improved from 54±19 to 68±22 and WOMAC from 65±22 to 75±22. The improvement in PROMs were similar between the 2 groups.

We report very good long-term joint preservation for the treatment of FAI, which is similar to those reported in hip dysplasia. In addition, we report satisfactory improvement in function following such treatment. The differences reported in joint survival likely reflect selection biases from the treating surgeon; more complex cases and those associated with more complex anatomy were more likely to have been offered a SD in order to address the pathology with greater ease and hence the inferior joint preservation identified in this group.

For any figures or tables, please contact the authors directly.

Abstract

Management of acetabular fractures in the elderly population remains somewhat controversial in regards to when to consider is open reduction internal fixation (ORIF) versus acute primary total hip. study aims to (1) describe outcome of this complex problem and investigate predictors of successful outcome.

This retrospective study analyzes all acetabular fractures in patients over the age of 60, managed by ORIF at a tertiary trauma care centre between 2007 and 2018 with a minimum follow up of one year. Of the 117 patients reviewed, 85 patients undergoing ORIF for treatment of their acetabular fracture were included in the analysis. The remainder were excluded based management option including acute ORIF with THA (n=10), two-stage ORIF (n=2), external fixator only (n=1), acute THA (n=1), and conservative management (n=1). The remainder were excluded based on inaccessible medical records (n=6), mislabelled diagnosis (n=6), associated femoral injuries (n=4), acetabular fracture following hemiarthroplasty (n=1). The mean age of the cohort is 70±7 years old with 74% (n=62) of patients being male. Data collected included: demographics, mechanism of injury, Charlson Comorbidity Index (CCI), ASA Grade, smoking status and reoperations. Pre-Operative Radiographs were analyzed to determine the Judet and Letournel fracture pattern, presence of comminution and posterior wall marginal impaction. Postoperative radiographs were used to determine Matta Grade of Reduction. Outcome measures included morbidity-, mortality- rates, joint survival, radiographic evidence of osteoarthritis and patient reported outcome measures (PROMs) using the Oxford Hip Score (OHS) at follow-up. A poor outcome in ORIF was defined as one of the following: 1) conversion to THA or 2) the presence of radiographic OA, combined with an OHS less than 34 (findings consistent with a hip that would benefit from a hip replacement). The data was analyzed step-wise to create a regression model predictive of outcome following ORIF.

Following ORIF, 31% (n=26) of the cohort had anatomic reduction, while 64% (n=54) had imperfect or poor reduction. 4 patients did not have adequate postoperative radiographs to assess the reduction. 31 of 84 patients undergoing ORIF had a complication of which 22.6% (n=19) required reoperation. The most common reason being conversion to THA (n=14), which occurred an average of 1.6±1.9 years post-ORIF. The remainder required reoperation for infection (n=5). Including those converted to THA, 43% (n=36) developed radiographic OA following acetabular fracture management. The mean OHS in patients undergoing ORIF was 36 ± 10; 13(16%) had an OHS less than 34. The results of the logistic regression demonstrate that Matta grade of reduction (p=0.017), to be predictive of a poor outcome in acetabular fracture management. With non-anatomic alignment following fixation, patients had a 3 times greater risk of a poor outcome. No other variables were found to be predictive of ORIF outcome.

The ability to achieve anatomic reduction of fracture fragments as determined by the Matta grade, is predictive of the ability to retain the native hip with acceptable outcome following acetabular fracture in the elderly. Further research must be conducted to determine predictors of adequate reduction in order to identify candidates for ORIF.

Introduction

Interactions between hip, pelvis and spine, as abnormal spinopelvic movements, have been associated with inferior outcomes following total hip arthroplasty (THA). Changes in pelvis position lead to a mutual change in functional cup orientation, with both pelvic tilt and rotation having a significant effect on version. Hip osteoarthritis (OA) patients have shown reduced hip kinematics which may place increased demands on the pelvis and the spine.

Sagittal and coronal planes assessments are commonly done as these can be adequately studied with anteroposterior and lateral radiographs. However, abnormal pelvis rotation is likely to compromise the outcome as they have a detrimental effect on cup orientation and increased impingement risk. This study aims to determine the association between dynamic motion and radiographic sagittal assessments; and examine the association between axial and sagittal spinal and pelvic kinematics between hip OA patients and healthy controls (CTRL).

Introduction

Acetabular component orientation is an important determinant of outcome following total hip arthroplasty (THA). Although surgeons aim to achieve optimal cup orientation, many studies demonstrate their inability to consistently achieve this. Factors that contribute are pelvic orientation and the surgeon's ability to correctly orient the cup at implantation. The goal of this study was to determine the accuracy with which surgeons can achieve cup orientation angles.

As our understanding of hip function and disease improves, it is evident that the acetabular fossa has received little attention, despite it comprising over half of the acetabulum’s surface area and showing the first signs of degeneration. The fossa’s function is expected to be more than augmenting static stability with the ligamentum teres and being a templating landmark in arthroplasty. Indeed, the fossa, which is almost mature at 16 weeks of intrauterine development, plays a key role in hip development, enabling its nutrition through vascularization and synovial fluid, as well as the influx of chondrogenic stem/progenitor cells that build articular cartilage. The pulvinar, a fibrofatty tissue in the fossa, has the same developmental origin as the synovium and articular cartilage and is a biologically active area. Its unique anatomy allows for homogeneous distribution of the axial loads into the joint. It is composed of intra-articular adipose tissue (IAAT), which has adipocytes, fibroblasts, leucocytes, and abundant mast cells, which participate in the inflammatory cascade after an insult to the joint. Hence, the fossa and pulvinar should be considered in decision-making and surgical outcomes in hip preservation surgery, not only for their size, shape, and extent, but also for their biological capacity as a source of cytokines, immune cells, and chondrogenic stem cells.

Cite this article: Bone Joint Res 2020;9(12):857–869.

Introduction

In total hip arthroplasty, a high radiographic inclination angle (RI) of the acetabular component has been linked to short- and long-term complications. There are several factors that lead to RI outliers including cup version, pelvic orientation and angle of the cup introducer relative to the floor. The primary aim of this study was to analyse what increases the risk of having a cup with an RI outside the target zone when controlling cup orientation with a digital inclinometer.

Introduction

Spinopelvic mobility has been associated with THA outcome. To-date spine assessments have been made quasi-statically, using radiographs, in standing and seated positions but dynamic spinopelvic mobility has not been well explored. This study aims to determine the association between dynamic (motion analysis) and quasi-static (radiographic) sagittal assessments and examine the association between axial and sagittal spinal kinematics in hip OA patients and controls.

The use of cementless acetabular components is currently the gold standard for treatment in total hip arthroplasty (THA). Porous coated cups have a low modulus of elasticity that enhances press-fit and a surface that promotes osseointegration. Monoblock acetabular cups represent a subtype of uncemented cup with the liner moulded into the metal shell, minimizing potential backside wear and eliminating the chance of mal-seating. The aim of this study was to compare the short-term clinical and radiographic performances of a modular cup with that of a monoblock cup, with particular interest in the advent of lucent lines and their correlation with clinical outcomes.

In this multi-surgeon, prospective, randomized, controlled trial, 86 patients undergoing unilateral THA were recruited. Participants were randomized to either a porous-coated, modular metal-on-polyethylene (MoP) acetabular component (n=46) or a hydroxyapatite (HA)- and titanium-coated monoblock shell with ceramic-on-ceramic (CoC) bearing (n=42). The porous-coated cup had an average pore size of 250 microns with an average volume porosity of 45%, whereas the monoblock shell had an average pore size of 300 microns with an average volume porosity of 48% and a HA coating thickness of 80 nm. There were no baseline demographic differences between both groups regarding sex, age, body mass index (BMI), or American Society of Anaesthesia (ASA) class (p>0.05). All of the sockets were under-reamed by 1 mm. Radiographs and patient-reported outcome measures (PROMs), including modified Harris Hip Score (mHHS), Western Ontario and McMaster Universities Arthritis Index (WOMAC) and University of California at Los Angeles (UCLA) Hip Score, were available for evaluation at a minimum of 2 years of follow-up. A radiolucent distance between the cup and acetabulum of ≥0.5 mm was defined as gap if it was diagnosed from outset or as radiolucency if it had sclerotic edges and was found on progressive x-ray analyses.

Thirty-two gaps (69%) were found in the modular cup group and 28 (6%) in the monoblock one (p=0.001). Of the former, 17 filled the gaps whereas 15 turned into a radiolucency at final assessment. Of the latter, only 1 of the gaps turned into a radiolucency at final follow-up (p 0.05) in both groups. Only the porous-coated cup was an independent predictor of lucent lines (OR:0.052, p=0.007). No case underwent revision surgery due to acetabular loosening during the study period. Only 2 cases of squeaking were reported in the CoC monoblock shell.

Both porous-coated modular and hydroxyapatite-coated monoblock cups showed successful clinical results at short-term follow-up, however, the former evidenced a significantly higher rate of radiolucent line occurrence, without any association with PROMs. Since these lines indicate the possibility of future cup loosening, longer follow-up and assessment are necessary.

Spinopelvic mobility describes the change in lumbar lordosis and pelvic tilt from standing to sitting position. For 1° of posterior pelvic tilt, functional cup anteversion increases by 0.75° after total hip arthroplasty (THA). Thus, spinopelvic mobility is of high clinical relevance regarding the risk of implant impingement and dislocation.

Our study aimed to 1) determine the proportion of OA-patients with stiff, normal or hypermobile spino-pelvic mobility and 2) to identify clinical or static standing radiographic parameters predicting spinopelvic mobility.

This prospective diagnostic cohort study followed 122 consecutive patients with end-stage osteoarthritis awaiting THA. Preoperatively, the Oxford Hip Score, Oswestry Disability Index and Schober's test were assessed in a standardized clinical examination. Lateral view radiographs were taken of the lumbar spine, pelvis and proximal femur using EOS© in standing position and with femurs parallel to the floor in order to achieve a 90°-seated position. Radiographic measurements were performed for the lumbar lordosis angle (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI) and pelvic-femoral-angle (PFA). The difference in PT between standing and seated allowed for patient classification based on spino-pelvic mobility into stiff (±30°).

From the standing to the sitting position, the pelvis tilted backwards by a mean of 19.6° (SD 11.6) and the hip was flexed by a mean of 57° (SD 17). Change in pelvic tilt correlated inversely with change in hip flexion.

Spinopelvic mobility is highly variable in patients awaiting THA and we could not identify any clinical or static standing radiographic parameter predicting the change in pelvic tilt from standing to sitting position. In order to identify patients with stiff or hypermobile spinopelvic mobility, we recommend performing lateral view radiographs of the lumbar spine, pelvis and proximal femur in all patients awaiting THA. Thereafter, implants and combined cup inclination/anteversion can be individually chosen to minimize the risk of dislocation.

No predictors could be identified. We recommend performing sitting and standing lateral view radiographs of the lumbar spine and pelvis to determine spinopelvic mobility in patients awaiting THA.

Purpose

Spinopelvic parameters are associated with the development of symptomatic femoroacetabular impingement and subsequent osteoarthritis. Pelvic incidence (PI) characterizes the sagittal profile of the pelvis and is important in the regulation of both lumbar lordosis and pelvic orientation (i.e. tilt). The purpose of this imaging-based study was to test the association between PI and acetabular morphology.

Aims

Our study aimed to 1) determine if there was a difference for the HOOS-PS score between patients with stiff/normal/hypermobile spinopelvic mobility and 2) to investigate if functional sagittal cup orientation affected patient reported outcome 1 year post-THA.

Aims

Our study aimed to 1) Describe the changes in spinopelvic mobility when transitioning from standing, to ‘relaxed-seated’ and thereafter to ‘deep-seated’ position and 2) Determine the change in spinopelvic mobility types 1 year post-THA compared to preoperatively.

During a periacetabular osteotomy (PAO), intra-operative assessment of correction of acetabular parameters is typically performed using fluoroscopy of the hip, a technique that has not been shown to produce predictable measurements. Furthermore, paralysing agents are used in order to facilitate dissection and fragment mobilization. The effect of paralysing agents on spino-pelvic posture is yet to be investigated.

This study aims to: 1. Compare the reliability of intra-operative x-rays versus hip fluoroscopy in the assessment of acetabular fragment correction and 2. Evaluate the effect of changes in spino-pelvic alignment on the assessment of acetabular correction. An IRB approved, retrospective review of all patients who underwent a PAO at our institution between 2006–2018 was performed. Patient demographic data was collected and all available imaging studies were retrieved. Patients were excluded if there was no available to review intra-operative AP pelvis x-ray or intra-operative fluoroscopic PA image of the hip.

Using a validated hip analysis software (Hip2Norm), the lateral center edge angle (LCEA) and acetabular index (AI) of plain radiographs were measured. The sacro-femoral-pubic angle (SFP), along with the LCEA and AI of the fluoroscopic image were measured using ImageJ. A oneway ANOVA was used to detect differences between measured parameters in the intra-operative x-ray, the post-operative x-ray and the fluoroscopic image. A total of 93 patients were identified. 26 patients were excluded due to missing data. The mean LCEA in the post-operative, intra-operative, and fluoroscopic groups were as follows: 33.67° (range 5.3° to 52.4°), 30.71°(range 9° to 55.6°), and 29.23°(range 12.4° to 51.4°) respectively. The mean AI in the post-operative, intra-operative, and fluoroscopic groups were as follows: −0.65° (range −18.10° to 27.30°), 0.35°(range −16.10° to 17.20°), and 5.54°(range −11.66° to 27.83°) respectively.

When comparing intra-operative to post-operative plain radiographs, there was no statistically significant difference in AI (ΔAI −1±1.29° p=0.71) or LCEA (ΔLCEA 2.95±1.38° p=0.09). When comparing fluoroscopy to post-operative plain radiographs, there was a statistically significant difference in AI (ΔAI −6.21±1.29° p < 0 .0001) as well as LCEA (ΔLCEA 4.44±1.38° p < 0 .0001). Statistical analysis revealed no influence of demographics (age, BMI, gender), on acetabular correction parameters. The mean SPF angles measured from intra-operative and post-operative x-rays were 69.32±5.11° and 70.45±5.52°. There was a statistically significant difference between these 2 measurements with a ΔSFP of 1.03° (p < 0 .0001).

The results of our study show that the use of intra-operative x-ray for the assessment of LCEA and AI is more reliable than fluoroscopic images. Further, we found a difference in SFP angle, which offers an indirect assessment of pelvic tilt, between the intra-operative and the post-operative plain x-rays. This suggests that there are changes in pelvic tilt during the surgery, which can be attributed to either patient positioning or changes in spino-pelvic posture secondary to the paralysing agents used by the anesthetists. The use of intra-operative x-rays as well as the effect of paralysing agents on spino-pelvic alignment should be considered by surgeons performing PAO's.

Acetabular dysplasia (AD) can cause hip pain and early osteoarthritis. Lateral Centre Edge Angle (LCEA) and sourcil angle (AI) are plain radiographic measures of acetabular morphology, however there is little agreement as to what constitutes mild, moderate or severe dysplasia. This study aims to establish the correlation, if any, between two-dimensional (XR) and three-dimensional (CT) measurements of acetabular morphology and to establish the level of femoral head cover (CTFHC) for different levels of dysplasia.

Introduction

Patients with reduced lumbar spine mobility are at higher risk of dislocation after THA as their hips have to compensate for spinal stiffness. Therefore our study aimed to 1) Define the optimal protocol for identifying patients with mobile hips and stiff lumbar spines and 2) Determine clinical and standing radiographic parameters predicting high hip and reduced lumbar spine mobility.

Aims

The aims of the study were to determine the differences in spinopelvic mobility between a cohort of hip OA patients and a control group for the 1) standing to relaxed-seated and 2) standing to deep-seated task.

Introduction

Porous coated cups have a low modulus of elasticity that enhances press-fit and a surface that promotes osseointegration as well as permitting modularity. Monoblock ceramic acetabular cups represent a subtype of uncemented cup permitting the use of large femoral heads. The aim of this study was to compare the short-term clinical and radiographic performances of both cups.

Aims

This study of patients with osteoarthritis (OA) of the hip aimed to: 1) characterize the contribution of the hip, spinopelvic complex, and lumbar spine when moving from the standing to the sitting position; 2) assess whether abnormal spinopelvic mobility is associated with worse symptoms; and 3) identify whether spinopelvic mobility can be predicted from static anatomical radiological parameters.

Introduction

The periacetabular osteotomy (PAO) improves hip joint mechanics in patients with symptomatic dysplasia. As a consequence of the multi-planar acetabular re-orientation, the course of the iliopsoas tendon over the hip may be affected, potentially resulting in iliopsoas tendon-related pain. At present, little information regarding the incidence of iliopsoas-related pathology following PAO exists.

We aimed to identify the incidence of iliopsoas-related pain following PAO. Secondarily, we aimed to identify any risk factors associated with this pathology.

Introduction

Acetabular dysplasia is typically characterised by insufficient antero-superior femoral head coverage. It is postulated (yet unproven) that patients with dysplasia compensate by reducing pelvic tilt (anterior pelvic rotation), effectively retroverting their acetabulum to improve antero-superior cover. We aimed to 1) define pelvic tilt (PT) in patients with bilateral and unilateral dysplasia, and 2) quantify PT changes following a successful periacetabular osteotomy (PAO).

Aims

Cardiac magnetic resonance (CMR) was used to assess whether cardiac function or tissue composition was affected in patients with well-functioning metal-on-metal hip resurfacing arthroplasties (MoMHRA) when compared with a group of controls, and to assess if metal ion levels correlated with any of the functional or structural parameters studied.

Introduction

Peri-acetabular-osteotomy (PAO) was initially described for the correction of acetabular dysplasia. Anteverting PAO is an established treatment for acetabular retroversion. By reviewing a large cohort, we aimed to (1) Test whether PAO outcome is equivalent in different types of deformity (classic dysplasia vs. retroversion) and (2) Determine whether outcome in acetabular retroversion is different between impinging-only hip and hips with combined pathology (impingement & dysplasia).

Introduction

Acetabular retroversion (AR) can cause pain and early osteoarthritis. The sagittal pelvic position or pelvic tilt (PT)has a direct relationship with acetabular orientation. As the pelvis tilts anteriorly, PT reduces and AR increases. Therefore, AR may be a deformity secondary to abnormal PT (functional retroversion) or an anatomical deformity of the acetabulum and/or pelvic ring.

This study aims to:

Define PT at presentation is in AR patients and whether this is different to controls (volunteers without pain).

Aims

This study aims to: determine the difference in pelvic position that occurs between surgery and radiographic, supine, postoperative assessment; examine how the difference in pelvic position influences subsequent component orientation; and establish whether differences in pelvic position, and thereafter component orientation, exist between total hip arthroplasties (THAs) performed in the supine versus the lateral decubitus positions.

Introduction

The resultant cup orientation depends upon the orientation of the pelvis at impaction. No studies to date have assessed whether patient-position during total hip arthroplasty (THA) has an effect on cup orientation. This study aims to 1) Determine the difference in pelvic position that occurs between surgery and radiographic, supine, post-operative assessment; 2) Examine how the difference in pelvic position influences subsequent cup orientation and 3) Establish whether pelvic orientation, and thereafter cup orientation, differences exist between THAs performed in the supine versus the lateral decubitus positions.

Introduction

The mechanisms of how spinal arthrodesis (SA) affects patient function after total hip replacement (THA) remain unclear. The objectives of this study were to a) Determine how outcome post-THA compares between patients with- and without-SA, b) Characterize sagittal pelvic changes that occur when moving between different functional positions, and test for differences between patients with- and without-SA, and c) Assess whether differences in sagittal pelvic dynamics are associated with outcome post-THA.

Introduction

The changes in sagittal spino-pelvic balance from standing to sitting in patients with end-stage osteoarthritis (OA) of the hip remain poorly characterized. Our aim was to 1) investigate the contribution of sagittal spino-pelvic movement and hip flexion when moving from a standing to sitting posture in patients with hip OA; 2) determine the proportion of OA-patients with stiff, normal or hypermobile spino-pelvic mobility and 3) identify radiographic parameters correlating with spino-pelvic mobility.

Endoprosthetic replacement (EPR) is an available option for the management of massive bone loss around failed knee implants. The aim of this study was to determine the results of knee EPRs performed for non-tumour indications. Since 2007, 85 EPRs were performed for in a single tertiary centre by seven surgeons. Mean age at surgery was 73.5 years (range:35–95) with infection as the most common indication (49%), followed by aseptic loosening (18%), complex primary replacement (16%), fracture (15%) and mechanical failure (2%). Mean follow up was 4 years (range:1–9). Functional outcome was determined using the Oxford Knee Score (OKS). At follow-up, 21 patients were deceased and 2 lost to follow-up. Complication rate was 19%. Of the 7 infected cases, 6 were treated with DAIR (debridement, antibiotics, and implant retention) and one underwent above knee amputation. Four of the patients undergoing DAIR were cleared of infection and 2 are on long-term antibiotics. Accounting for implant revision, loss to follow-up and those on long-term antibiotics as failures, 5-year survival was 89% with an average OKS of 25 (SD=10). This mid-term study shows that distal femur EPR is a valuable option for the increasing burden of complex revision knee surgery

Introduction

This study aims to determine how the acetabular version changes during the key developmental stage of adolescence, and what contributes to this change. In addition, we examined whether patient factors (BMI, activity levels) or the femoral-sided anatomy contribute to any observed changes.

Introduction

Acetabular and spino-pelvic (SP) morphological parameters are important determinants of hip joint dynamics. This study aims to determine whether acetabular and SP morphological differences exist between hips with and without cam morphology and between symptomatic and asymptomatic hips with cam morphology.

Introduction

Acetabular dysplasia is associated with an increased risk of hip pain and early development of osteoarthritis (OA). The Bernese peri-acetabular osteotomy (PAO) is the most well-established technique in the Western world for the treatment of symptomatic acetabular dysplasia. This case-control study aims to assess whether the severity of acetabular dysplasia has an effect on outcome following Peri-Acetabular Osteotomy (PAO) and/or the ability to achieve desired acetabular correction.

A modular hemiarthroplasty has a Metal-on-Metal (MoM) taper-trunnion junction, which may lead to increased wear and Adverse-Reaction-to-Metal-Debris (ARMD). To-date no wear related issues have been described in the elderly and less active that receives a hemiarthroplasty. This study aims to determine in vivo wear (i.e. serum metal ion levels) in hip hemiarthroplasty, and identify factors associated with increased wear.

This is a prospective, IRB approved, single-centre, cohort study of patients that received an uncemented, modular hemiarthroplasty of proven design for the treatment of hip fracture between 2013–2015. All, alive, patients at 12-months post-implantation with AMTS≥6 were invited to participate. Of the 125 eligible patients, 50 accepted the invitation and were reviewed, including clinical/radiological assessment, metal-ion ([Chromium (Cr) and Cobalt (Co)]) measurement and Oxford Hip Score (OHS). Acetabular erosion was graded (0–3: normal-protrusio). Metal ion levels were considered high if ≥7ppb.

The mean OHS was 37 (SD: 10). No acetabular erosion was detected in 21, whilst the remaining had either grade-1 (n=21) or grade-2 (n=8). The median Cr and Co levels were 2.9 (SD:9) and 2.2 (SD:4) respectively. There were 8 cases (16%) with high ion levels. To-date only 2 of them has an ARMD lesion, and none have been revised. Patients with metal ion levels had similar pre-fall mobility, taper- and head- size and OHS to those with low metal ion levels (p=0.2–0.7) However, all hips with high metal ion levels had evidence of acetabular erosion (≥1).

Modular Hip hemiarthroplasties and their taper-trunnion junction are not immune to high wear and ARMD despite being implanted in a less active cohort. Acetabular erosion should alert clinicians, as it is associated with 20× increased-risk of taper wear, presumably due to the increased transmitted torque. Whether the use of modular hemiarthroplasties should remain is debatable.

Degenerative hip and spine pathologies often co-exist, as Hip-Spine-Syndrome (HSS). Many patients eventually need surgery in both hip (THR) and spine [decompression-spinal-arthrodesis (DSA)]. This case-control study aims to determine whether the presence of a DSA compromised THR outcome and whether outcome of THR is better if performed prior to- (THR-1^st) or after- DSA (THR-2^nd).

This is a single centre, multi-surgeon, retrospective, case-control study. Of the 748 patients that underwent DSA between 2004–15, 43 patients (54 THRs) have also had a 1° THR(s) at our unit and formed the cases. Thirty-two THRs were performed prior to the DSA (THR-1^st) and 22 were done following the DSA (THR-2^nd). Most cases had either 1- (n=3) or 2-level (n=20) DSA. The most common DSA level was L4/5 (n=23). The mean THR-DSA interval was 3.6 years. Controls were patients (n=67) without DSA or previous spinal surgery, that had a THR in our unit over the same study period matched for age, gender and type of THR implanted.

Patient Reported Outcome Measures (PROMs) were obtained using the Oxford-Hip- and Harris-Hip-Scores (OHS/HHS), with the difference between post- and pre-operative scores defined as Δ. Outcome was compared between Cases and Controls and between THR-1^st and THR-2^nd Groups. Outcome measures included complications, revisions, PROMs and cup orientations achieved.

The mean age at THR was 67 years old (SD: 11) and most patients were female (n=82, 68%). The mean cup inclination and anteversion angles were 41° (SD:8) and 21° (SD:8). At a mean follow-up of 6 years, the OHS improved from OHS_pre:16 (SD: 7) to OHS_fu:41 (SD:10) and the HHS improved from HHS_pre:51 (SD:14) to HHS_fu:88 (SD:13).

A greater incidence of complications were seen in the Cases (n=10; ARMD-3, infection-4, loosening-2, dislocation-1) compared to the Controls (n=3; dislocation-2, loosening-1) (p=0.01). Consequently, more THRs required revision in the Cases (n=7) compared to the Controls (n=1) (p=0.01). There were no differences in OHS_pre/OHS_fu/ΔOHS/HHS_pre/HHS_fu/ΔHHS between cases and controls (p=0.1 – 0.9).

There were no difference in complications (7/29 Vs. 3/25; p=0.3), nor revision rates (5/29 Vs. 2/25; p=0.3) between THA-1^st and THA-2^nd Groups. Greater differences in PROMs were detected between the groups. The THA-1^st Group, compared to the THA-2^nd Group had higher OHS_pre (19 Vs 12), HHS_pre (54 Vs 48), OHS_fu (43 Vs 32) and HHS_fu (93 Vs 76), (p=0.001–0.005). However, no statistically significant difference in ΔOHS (24 Vs 17) and ΔHHS (39 Vs 26) were seen between the THA-1^st and THA-2^nd Groups (p=0.1).

Patients with a 1° THR and DSA, had a greater rate complications and revisions compared to a matched control. Overall, no difference in PROMs were seen between Cases and Controls. No significantly increased risk of dislocation was seen in this predominantly 1- and 2-level DSA cohort. The superior PROMs detected in the THA-1^st Group provide evidence that the hip pathology should be addressed 1^st (in cases with 1- or 2-level planned DSA).

Aims

Advocates of debridement, antibiotics and implant retention (DAIR) in hip periprosthetic joint infection (PJI) argue that a procedure not disturbing a sound prosthesis-bone interface is likely to lead to better survival and functional outcome compared with revision. This case-control study aims were to compare outcome of DAIRs for infected primary total hip arthroplasty (THA) with outcomes following primary THA and two-stage revision of infected primary THAs.

Aim

Advocates of Debridement-Antibiotics-and-Implant-Retention (DAIR) in hip peri-prosthetic joint infection (PJI) argue that a procedure not disturbing a sound prosthesis-bone interface is likely to lead to better survival and functional outcome compared to revision. However, no evidence supports this. This case-control study's aims were to compare outcome of DAIRs for infected 1° total hip arthroplasty (THA) with outcomes following 1° THA and 2-stage revisions of infected 1° THAs.

Introduction

The burden of peri-prosthetic joint infection (PJI) following hip and knee surgery is increasing. Endoprosthetic replacement (EPR) is an option for management of massive bone loss resulting from infection around failed lower limb implants.

Objectives

A possible solution for the management of proximal femoral bone loss is a modular femoral endoprosthesis (EPR). Although the outcome of EPRs in tumour surgery has been well described, the outcome of their use in revision hip surgery has received less attention. The aim of this study was to describe the outcome of using EPR for non-neoplastic indications.

Image-guided intra-articular hip injection of local-anaesthetic and steroid is commonly used in the management of hip pain. It can be used as a diagnostic and/or therapeutic tool and is of low cost (£75). The aim of this study was to assess how often a hip injection has a therapeutic effect.

This is a retrospective, consecutive, case series of intra-articular hip injections performed in a tertiary referral hospital over a 2-year period (2013–4). Patients were identified from the radiology department's prospectively entered database. Clinical information, reason for injection and subsequent management was obtained from hospital records. All patients prospectively reported their pain levels in a numeric pain scale diary (out of 10) at various time points; pre-, immediately post-, 1st day-, 2nd day- and 2 weeks- post-injection. Only patients with complete pain scores at all time points were included (n=200, of the 250 injections performed over study period, 80%).

The majority of injections were performed for osteoarthritis (OA) treatment (82%). The pain was significantly reduced from a pre-injection score of 7.5 (SD:2) to 5.0 (SD:3) immediately post-injection(p<0.001); only 24 (11%) reported any worsening of pain immediately post-injection. Pain significantly reduced further to 3.8(SD:3) at 2-weeks post-injection (p<0.001). 50% of patients had at least a 3 point drop in reported pain. No improvement was seen in 18 patients and 10 (5%) reported worse pain at 2-weeks compared to pre-injection. Of the OA cohort, 10% have required repeat injections, 45% required no further intervention and 45% underwent or are due for hip replacement. No immediate complications occurred.

Intra-articular hip injection reduced pain in 86% of cases and has delayed any further surgical treatment for at least 2 years in over 50% of OA cases. It is hence a cost-effective treatment modality. Further work is necessary to describe factors predicting response.

The management of proximal femoral bone loss is a significant challenge in revision hip arthroplasty. A possible solution is the use of a modular proximal femur endoprosthesis (EPR). Although the survivorship and functional outcome of megaprostheses used in tumour surgery has been well described, outcome of EPRs used in revision hip surgery has received less attention. The aim of this study was to determine the 5-year outcome following proximal femur EPR and determine factors that influence it.

This was a retrospective consecutive case series of all EPRs (n=80) performed for non-neoplastic indications, by 6 surgeons, in our tertiary referral centre, between 2005–2014. Patient demographics and relevant clinical details were determined from notes. The most common indications for the use of EPRs included infection (n=40), peri-prosthetic fracture (n=12) and failed osteosynthesis of proximal femoral fractures/complex trauma (n=11). Outcome measures included complication and re-operation rates, implant survival and assessment of functional outcome using the Oxford-Hip-Score (OHS).

The mean age at surgery was 69 years and mean follow-up was 4 (0 – 11) years. The mean number of previous hip operations was 2.4 (range: 0 – 17). Twenty-five patients sustained a complication (31%), the most common being infection (n=9) and dislocation (n=4). By follow-up, further surgery was required in 18 (22%) hips, 9 of which were EPR revisions. 5-yr implant survivorship was 87% (95%CI: 76 – 98%). Mean OHS was 28 (range: 4 – 48). Inferior survival and outcome were seen in EPRs performed for the treatment of infection. Infection eradication was achieved in 34/41 with the index EPR procedure and in 40/41 hips by follow-up.

Limb salvage was achieved in all cases and acceptable complication- and re-operation rates were seen. EPRs for periprosthetic fractures and failed osteosynthesis had best outcome. We recommend the continued use of proximal femur EPR in complex revision surgery.

Introduction

The value of Debridement-Antibiotics-and-Implant-Retention (DAIR) in prosthetic-joint-infection (PJI) is still a matter of debate as most studies to-date are underpowered with variable end-points. In our, tertiary referral, bone infection unit we consider DAIR to be a suitable option in all PJIs with soundly fixed prostheses, despite chronicity. The aims of this study were to define the long-term outcome following DAIR in hip PJI and identify factors that influence it.

Debridement, antibiotics and implant retention (DAIR) is a surgical option in the treatment of prosthetic joint infection (PJI). It is thought to be most appropriate in the treatment of early (≤6 weeks post-op) PJI. Most studies to-date reporting on DAIRs in hip PJI have been underpowered by reporting on small cohorts (n= <45), or report on registry data with associated biases and limitations. In our, tertiary referral, bone infection unit we consider DAIR to be a suitable option in all cases of PJI with a soundly fixed prosthesis, with early or late presentation, especially in patients who are too elderly or infirm to undergo major surgery.

Aim: To define the 10-year outcome following DAIR in hip PJI and identify factors that influence it.

We retrospectively reviewed all DAIRs performed in our unit between 1997 and 2013 for hip PJI. Only infected cases confirmed by histological and microbiological criteria were included. Data recorded included patient demographics and medical history, type of surgery performed (DAIR or DAIR + exchange of modular components), organism identified and type/duration of antibiotic treatment. Outcome measures included complications, mortality rate, implant survivorship and functional outcome.

121 DAIRs were identified with mean age of 71 years (range: 33–97). 67% followed an index procedure of 1° arthroplasty. 53% included exchange of modular components. 60% of DAIRs were for early onset PJI. Isolated staphylococcus was present in 50% of cases and 25% had polymicrobial infection. At follow-up (mean:7 years, range: 0.3 – 18), 83 patients were alive; 5- and 10- year mortality rates were 15% and 35% respectively. 45% had a complication (persistence of infection: 27%, dislocation: 10%) and 40% required further surgery. Twenty hips have been revised to-date (17%). Performing a DAIR and not exchanging the modular components was associated with an almost 3× risk (risk ratio: 2.9) of subsequent implant failure (p=0.04). 10-yr implant survivorship was 80% (95%CI: 70 – 90%). Improved 10-year implant survivorship was associated with DAIR performed for early PJI (85% Vs 68%, p=0.04). Functional outcome will be discussed.

DAIR is a particularly valuable option in the treatment of hip PJI, especially in the early post-operative period. Whenever possible, exchange of modular implants should be undertaken, however DAIRs are associated with increased morbidity even in early PJI. Factors that predict success of DAIR in late PJI need to be identified.

Introduction

Joint preserving procedures have gained popularity in an attempt to delay arthroplasty in young, dysplastic hips. Excellent results can be achieved with peri-acetabular osteotomy (PAO) in congruent non-arthritic hips. The role of salvage procedures such as the Shelf acetabuloplasty remains undefined. This study aims to determine the long-term survival and functional outcome following Shelf acetabuloplasty and to identify factors that influence outcome.

We assessed the orientation of the acetabular component in 1070 primary total hip arthroplasties with hard-on-soft, small diameter bearings, aiming to determine the size and site of the target zone that optimises outcome. Outcome measures included complications, dislocations, revisions and ΔOHS (the difference between the Oxford Hip Scores pre-operatively and five years post-operatively). A wide scatter of orientation was observed (2sd 15°). Placing the component within Lewinnek’s zone was not associated withimproved outcome. Of the different zone sizes tested (± 5°, ± 10° and ± 15°), only ± 15° was associated with a decreased rate of dislocation. The dislocation rate with acetabular components inside an inclination/anteversion zone of 40°/15° ± 15° was four times lower than those outside. The only zone size associated with statistically significant and clinically important improvement in OHS was ± 5°. The best outcomes (ΔOHS > 26) were achieved with a 45°/25° ± 5° zone.

This study demonstrated that with traditional technology surgeons can only reliably achieve a target zone of ±15°. As the optimal zone to diminish the risk of dislocation is also ±15°, surgeons should be able to achieve this. This is the first study to demonstrate that optimal orientation of the acetabular component improves the functional outcome. However, the target zone is small (± 5°) and cannot, with current technology, be consistently achieved.

Cite this article: Bone Joint J 2015;97-B:164–72.

National Institute of Clinical Excellence guidelines state that cemented stems with an Orthopaedic Data Evaluation Panel (ODEP) rating of > 3B should be used for hemiarthroplasty when treating an intracapsular fracture of the femoral neck. These recommendations are based on studies in which most, if not all stems, did not hold such a rating.

This case-control study compared the outcome of hemiarthroplasty using a cemented (Exeter) or uncemented (Corail) femoral stem. These are the two prostheses most commonly used in hip arthroplasty in the UK.

Data were obtained from two centres; most patients had undergone hemiarthroplasty using a cemented Exeter stem (n = 292/412). Patients were matched for all factors that have been shown to influence mortality after an intracapsular fracture of the neck of the femur. Outcome measures included: complications, re-operations and mortality rates at two, seven, 30 and 365 days post-operatively. Comparable outcomes for the two stems were seen.

There were more intra-operative complications in the uncemented group (13% vs 0%), but the cemented group had a greater mortality in the early post-operative period (n = 6). There was no overall difference in the rate of re-operation (5%) or death (365 days: 26%) between the two groups at any time post-operatively.

This study therefore supports the use of both cemented and uncemented stems of proven design, with an ODEP rating of 10A, in patients with an intracapsular fracture of the neck of the femur.

Cite this article: Bone Joint J 2015;97-B:94–9.

There is great variability in acetabular component orientation following hip replacement. The aims of this study were to compare the component orientation at impaction with the orientation measured on post-operative radiographs and identify factors that influence the difference between the two. A total of 67 hip replacements (52 total hip replacements and 15 hip resurfacings) were prospectively studied. Intra-operatively, the orientation of the acetabular component after impaction relative to the operating table was measured using a validated stereo-photogrammetry protocol. Post-operatively, the radiographic orientation was measured; the mean inclination/anteversion was 43° (sd 6°)/ 19° (sd 7°). A simulated radiographic orientation was calculated based on how the orientation would have appeared had an on-table radiograph been taken intra-operatively. The mean difference between radiographic and intra-operative inclination/anteversion was 5° (sd 5°)/ -8° (sd 8°). The mean difference between simulated radiographic and intra-operative inclination/anteversion, which quantifies the effect of the different way acetabular orientation is measured, was 3°/-6° (sd 2°). The mean difference between radiographic and simulated radiographic orientation inclination/anteversion, which is a manifestation of the change in pelvic position between component impaction and radiograph, was 1°/-2° (sd 7°).

This study demonstrated that in order to achieve a specific radiographic orientation target, surgeons should implant the acetabular component 5° less inclined and 8° more anteverted than their target. Great variability (2 sd about ± 15°) in the post-operative radiographic cup orientation was seen. The two equally contributing causes for this are variability in the orientation at which the cup is implanted, and the change in pelvic position between impaction and post-operative radiograph.

Cite this article: Bone Joint J 2014;96-B:1290–7

The orientation of the acetabular component is influenced not only by the orientation at which the surgeon implants the component, but also the orientation of the pelvis at the time of implantation. Hence, the orientation of the pelvis at set-up and its movement during the operation, are important. During 67 hip replacements, using a validated photogrammetric technique, we measured how three surgeons orientated the patient’s pelvis, how much the pelvis moved during surgery, and what effect these had on the final orientation of the acetabular component. Pelvic orientation at set-up, varied widely (mean (± 2, standard deviation (sd))): tilt 8° (2sd ±32), obliquity –4° (2sd ±12), rotation –8° (2sd ±14). Significant differences in pelvic positioning were detected between surgeons (p < 0.001). The mean angular movement of the pelvis between set-up and component implantation was 9° (sd 6). Factors influencing pelvic movement included surgeon, approach (posterior >  lateral), procedure (hip resurfacing > total hip replacement) and type of support (p < 0.001). Although, on average, surgeons achieved their desired acetabular component orientation, there was considerable variability (2sd ±16) in component orientation. We conclude that inconsistency in positioning the patient at set-up and movement of the pelvis during the operation account for much of the variation in acetabular component orientation. Improved methods of positioning and holding the pelvis are required.

Cite this article: Bone Joint J 2014; 96-B:876–83.

INTRODUCTION

Metal-on-metal hip resurfacing (MoMHRA) requires a new standardized radiographic evaluation protocol. Evaluation of the acetabular component is similar to total hip arthroplasty but the femoral component requires different criteria since there is no component in the femoral canal and the metallic femoral implant overlies the junctions between bone-cement and cement-prosthesis. Lucencies around the metaphyseal HRA femoral stem can be described with the femoral zonal system into 3 peg-zones (Amstutz' et al) but this doesn't account for bony changes of the femoral neck away from the stem. This study proposes a new femoral zonal system for radiographic HRA assessment. We tested the efficacy of radiographs in identifying a problem by reviewing 711 radiographs of resurfaced hips and correlating radiographic features to outcome.

Introduction

Solid or cystic pseudotumour is a potentially destructive complication of metal on metal (MoM) couples, usually needing revision surgery. However, complete clearance of the pseudotumour is unlikely at times. This prospective case-controlled study reports cases which had recurrence after revision surgery for pseudotumour related to metal on metal hip couples.

Recent events have highlighted the importance of implant design for survival and wear-related complications following metal-on-metal hip resurfacing arthroplasty. The mid-term survival of the most widely used implant, the Birmingham Hip Resurfacing (BHR), has been described by its designers. The aim of this study was to report the ten-year survival and patient-reported functional outcome of the BHR from an independent centre.

In this cohort of 554 patients (646 BHRs) with a mean age of 51.9 years (16.5 to 81.5) followed for a mean of eight years (1 to 12), the survival and patient-reported functional outcome depended on gender and the size of the implant. In female hips (n = 267) the ten-year survival was 74% (95% confidence interval (CI) 83 to 91), the ten-year revision rate for pseudotumour was 7%, the mean Oxford hip score (OHS) was 43 (sd 8) and the mean UCLA activity score was 6.4 (sd 2). In male hips (n = 379) the ten-year survival was 95% (95% CI 92.0 to 97.4), the ten-year revision rate for pseudotumour was 1.7%, the mean OHS was 45 (sd 6) and the mean UCLA score was 7.6 (sd 2). In the most demanding subgroup, comprising male patients aged < 50 years treated for primary osteoarthritis, the survival was 99% (95% CI 97 to 100).

This study supports the ongoing use of resurfacing in young active men, who are a subgroup of patients who tend to have problems with conventional THR. In contrast, the results in women have been poor and we do not recommend metal-on-metal resurfacing in women. Continuous follow-up is recommended because of the increasing incidence of pseudotumour with the passage of time.

INTRODUCTION

Femoral neck narrowing (NN) following Metal-on-Metal Hip Resurfacing Arthroplasty (MoMHRA) is a well-recognised clinical phenomenon. The incidence of resurfaced hips with NN > 10% is reported to be up to 27%. Its pathogenesis is thought to be multi-factorial secondary to stress shielding, impingement, osteolysis secondary to wear/ion particles and as a result of reduced vascularity and pressure effect on cancellous bone secondary to the presence of a soft-tissue mass around the resurfaced hip. Recognised risk factors for its development include: female gender and the presence of a pseudotumour. Serum Chromium (Cr) and Cobalt (Co) are recognised surrogate markers of in-vivo wear of MoMHRA. The aims of this study were to establish whether NN is associated with increased wear.

INTRODUCTION

Metal-on-metal hip resurfacing arthroplasty (MoMHRA) is a surgical option in the treatment of end-stage hip disease. The measurement of systemic levels of metal ions gives an insight into the wear occurring and is advocated by regulatory bodies as routine practice in the assessment of resurfaced hips. However, the acceptable upper levels of Chromium (Cr) and Cobalt (Co) ions concentration with clinical significance still have to be established. The aim of this study is to address this issue in unilateral and bilateral resurfaced hips.

Introduction

Since the introduction of 3rd generation Metal-on-Metal-Hip-Resurfacing-Arthroplasty (MoMHRA), thousands of such prostheses have been implanted worldwide in younger patients with end-stage hip osteoarthritis. However, no independent centre has reported their medium-to-long term outcome. The aim of this study is to report the ten year survival and outcome of the Birmingham Hip Resurfacing (BHR), the most commonly used MoMHRA worldwide.

Introduction

Osteoarthritis (OA) of the hip is an important cause of pain and morbidity. The mechanisms and pathogenesis of OA'sdevelopment remain unknown. Minor acetabular dysplasia and subtle variations in proximal femoral morphology are increasingly being recognized as factors that potentially compromise the joint biomechanically and lead to OA. Previous studies have shown that risk of hip OA increased as the femoral head to femoral neck ratio (HNR) decreased. Previous work has described the evolutionary change in inferior femoral neck trabecular density and geometry associated with upright stance, but no study has highlighted the evolutionary change in HNR. The aim of this study was to examine evolutionary evidence that the hominin bipedal stance has lead to alterations in HNR that would predispose humans to hip OA.

Introduction

Tribological studies have described a characteristic wear pattern of metal-on-metal hip resurfacings (MoMHRAs) with a run-in period followed by a ‘bedding-in’ phase minimising wear or by an increasing wear patch with edge loading. The use of metal ions as surrogate markers of in-vivo wear is now recommended as a screening tool for the performance of MoMHRAs. The aims of this retrospective, single-surgeon study were to measure ion levels in unilateral MoMHRAs at different stages during the steady-state in order to study the evolution of wear and factors affecting it.

INTRODUCTION

Studies have suggested that there is a reduction in head-neck-ratio (HNR) associated with MoMHRA. A reduction in HNR at operation would decrease range of movement and increase impingement risk. Impingement could lead to 20 edge loading, increasing wear. Serum ion levels of Chromium (Cr) and Cobalt (Co) are surrogate markers of wear. Although acetabular component orientation has been shown to contribute to wear and PT development, the role of a decrease in HNR has only been highlighted in PT development. This study aimed to measure changes in HNR that occur at resurfacing and determine any gender- and component size-specific differences. In addition it aimed to determine whether changes in HNR could be associated with increased wear.

INTRODUCTION

Although simulation studies have shown superior wear properties of metal-on-metal articulations, increased concern exists regarding the excess in-vivo wear of a small number of Metal-on-Metal-Hip-Resurfacing (MoMHRA) implants. Serum ion levels of Chromium (Cr) and Cobalt (Co) are surrogate markers of wear. Risk factors associated with increased wear include female gender, small components, dysplasia, cup orientation outside safe zone and femoral head downsize during surgery with an associated decrease in Head-Neck-Ratio (HNR). However, these factors are interlinked. This study aims to identify the factors that are most important for subsequent wear of MoMHRA, by performing a multivariate analysis.

INTRODUCTION

The introduction of hard-on-hard bearings and the consequences of increased wear due to edge-loading have renewed interest in the importance of acetabular component orientation for implant survival and functional outcome following hip arthroplasty. Some studies have shown increased dislocation risk when the cup is mal-oriented which has led to the identification of a safe-zone1. The aims of this prospective, multi-centered study of primary total hip arthroplasty (THA) were to: 1. Identify factors that influence cup orientation and 2. Describe the effect of cup orientation on clinical outcome.

A femoral head/neck ratio (HNR) of less than 1.27 is associated with an increased risk of arthritis. The aim of this study was to establish whether there is evolutionary evidence that the homonin, bipedal stance has led to alterations in HNR that predispose humans to osteoarthritis (OA).

Specimens provided by The Natural History Museums of London, Oxford and the Department of Zoology, University of Oxford were grouped according to gait pattern, HAKF (Hip and knee flexed), Arboreal (ability to stand with hip and knee joints extended) and homonin/bi-pedal. Specimens included those from Devonion, Triassic, Jurrasic, Cretaceous, Miocene, Paleolithic, Pleistocene periods to modern day. Three-dimensional skeletal geometries were segmented using CT images and HNR measurements were taken from coronal views. These were compared with the HNR of 119 asymptomatic human volunteers and 210 patients that had a hip joint replacement for primary OA.

Species of the HAKF group had the smallest HNR (1.10, SD:0.09). Species of the Arboreal group had significantly higher HNR (1.63, SD:0.15) in comparison to the Bipedal group (1.41, SD:0.04) (p=0.006), Human (1.33, SD:0.08) and the OA group (1.3, SD:0.09).

The range of movement associated with arboreal habitat caused an associated change in HNR. This study would suggest that the HNR peaked in the Miocene period with species that ambulated on both ground and trees. More recent homonin gait appears to have developed a smaller HNR and humans have the smallest amongst their close ancestors. Evolutionary theory would suggest that modern environmental pressures might pre-dispose future hominin evolution to OA, secondary to a further reduction in HNR.

Introduction: Metal-on-metal-hip-resurfacing-arthroplasty (MoMHRA) has been associated with the development of inflammatory pseudotumours(IP), especially in females. IPs have been linked to wear debris, which can be related to metal-ion blood levels. Acetabular component position has been shown to influence wear. We have identified an optimum component orientation minimising IP risk around an inclination/anteversion of 40°/20°±10°. Our aim was to see if this optimal position results in lower metal ions and to identify the boundary of an optimal placement zone for low wear.

Methods: A cohort of 104 patients(60M:44F) with unilateral MoMHRA was studied. Blood tests were obtained at a mean follow up of 3.9 years and serum Co/Cr levels were measured(ICPMS). High metal ion concentrations were defined as Co> 4.1ppb and Cr> 5.2ppb. Radiographic cup inclination/anteversion were measured using EBRA. The differences in ion levels between different orientation zones were investigated. Three orientation zones were defined centered on 40°/20°: Z1-within ±5°, Z2-outside ±5°/within ±10° and Z3-within ±10°.

Results: There was a wide range of cup placements. Females had significantly (p< 0.001) smaller components(mean:51, 44–60) than males(mean: 56, 52–64). Cr levels, but not Co, were higher in females(p=0.002) and those with small femoral components(< 50mm, p =0.03). Patients with cups within Z1 (n=13) had significantly lower Co(p=0.005) and Cr(p=0.001). Males with cups within Z3(n=27) had lower ion levels in comparison to those outside, which were significantly lower for Co(p=0.049) but not Cr(p=0.084). Females had similar ion levels within and out of Z3(Cr/Co: p=0.83/0.84). Co levels were significantly lower in Z1(n=13) in comparison to Z2(n=33)(p=0.048) but Cr levels were not different (p=0.06).

Discussion: MoMHRA cups placed within ±5° of the optimum(40°/20°) had significantly lower metal ions indicating lower wear within this narrow zone. This safe zone, could extend to ±10° for males only. The narrower safe zone coupled with smaller components implanted are possible factors contributing to the increased IP incidence seen in females.

Introduction: Metal on metal hip resurfacing arthroplasty(MoMHRA) is an alternative option to THR in the treatment of young adults with OA. A recognised MoMHRA complication is the development of an inflammatory pseudotumour(IP). Diagnosis is made with the aid of US and/or MRI. To-date, no radiographic indication of the presence of IP has been identified. Neck thinning is a recognised phenomenon in MoMHRA hips not associated with any adverse clinical events. Its pathogenesis is considered multi-factorial. Our aim was to establish whether excessive neck narrowing is associated with the presence of a pseudotumour.

Methods: Twenty-seven hips (26 patients) with IP confirmed clinically, radiologically, intra-operatively and histologically were matched for sex, age, pre-operative diagnosis, component size and follow-up with an asymptomatic MoMHRA cohort (Control n=60). For all patients, prosthesis-neck-ratio(PNR) was measured on plain AP pelvic radiographs post-operatively and at follow-up as previously described and validated.

Results: All IP patients (4M:23F) and all (12M:48F) but two controls had a posterior approach at the time of MoMHRA. Post-operatively, there was no difference in the PNR between the two groups (p=0.19). At an average follow up of 3.5 years (range:0.7–8.3), IP patients(mean 1.26, 1.10–1.79) had a significantly higher (p< 0.0001) PNR in comparison to their controls(mean 1.14, 1.03–1.35). Greater neck narrowing occurred in both genders. IP necks had narrowed by an average of 8% (range:3–23). The degree of neck narrowing was correlated with length of survival of implant (p=0.001).

Discussion: This study shows a strong association between IP and neck narrowing. Processes such as impingement and increased wear are considered to be involved in the pathogenesis of both IP and neck narrowing. Furthermore, the presence of an IP, could lead to altered vascularity via a mass effect and further contribute to neck narrowing. Neck narrowing in symptomatic MOMHRA patients should alert surgeons of the possible presence of IP.

Introduction: The development of Inflammatory Pseudotumour (IP) is a recognised complication following Metal on Metal Hip Resurfacing Arthroplasty (MoMHRA), thought to occur secondary to wear and elevated ion levels. Studies have shown that acetabular component orientation influences the wear of metal-on-metal hip replacement bearings. The aims of this study were to investigate the significance of cup orientation in the development of IP, and to identify a ‘safe-zone’ for cup placement with lower-risk for IP development.

Methods: Twenty six patients (n=27 hips) with IP confirmed radiologically, intra-operatively and histologically were matched for sex, age, pre-operative diagnosis, component size and follow-up with a cohort of asymptomatic MoMHRA patients (Control n=58). Radiographic acetabular anteversion and inclination were measured using EBRA. We calculated the distance in degree space of each acetabular component from the optimum position of 40° inclination and 20° anteversion, recommended by the designers, and thus compared acetabular component position between the two groups. Three different zones were tested as possibly optimum for acetabular placement. These were Lewinneck’s Zone (LZ) (inclination/anteversion; 30–50°/5–25°), and two zones defined by ±5° (Zone 1) or ± 10° (Zone 2) about the suggested target of 40°/20°. An optimal placement zone was determined based on a significant difference in IP incidence between components in the zone versus those outside.

Results: There was a wide range in cup orientations; mean inclination and anteversion were similar in the two groups: IP 47.5° (10.1°–80.6°)/14.1° (4.1°–33.6°) Vs Control 46.1° (28.8°–59.8°)/15.6° (4.3°–32.9°). Acetabular components in the IP group were significantly further away from the optimum position of 40°/20° in comparison to the controls (p=0.023). There was no difference in IP incidence between cups positioned within (IP:13/27, Control:35/58) or out of LZ (p=0.09) and within (IP: 2/27, Control: 10/58) or out of Zone 1 (p=0.156). Cups placed in Zone 2 (IP:6/27, Control:27/58) had significantly lower IP incidence versus those outside this zone (p=0.01). The odd’s ratio of developing IP when the cup is positioned out-of Zone 2 was 3.7.

Discussion: This study highlights the importance of ace-tabular component orientation in IP development. On the whole, patients with pseudotumour had acetabular components that were further away from the optimum position in comparison to the controls. However, a small number of IP patients had well-placed components implying that additional factors, possibly patient and/or gender specific, are involved in the development of pseudotumour. Furthermore, we defined an optimum, ‘safe-zone’ of ±10° around the cup position of 40°/20°. Patients with acetabular components outside this safe zone have an increased risk of IP development.

Introduction: Metal-on-metal hip resurfacing arthroplasty (MoMHRA) has gained popularity as an alternative to THR for younger patients with osteoarthritis. A growing concern has been the association of MoMHRA with the development of inflammatory pseudotumours (IP), especially in women. These have been linked to metal-on-metal wear, which can be related to metal ion concentrations. Elevated metal wear debris levels may result from impingement, rim contact and edge loading. Head-neck ratio (HNR) is a predetermining factor for range of movement and impingement. Neck thinning is a recognised phenomenon post-MoMHRA and we have found an association of IP with increased neck thinning based on a case control study. Our aims were to identify HNR changes a hip undergoes when resurfaced and at follow up; and whether greater neck thinning at follow-up could be associated with the presence of elevated metal ions.

Methods: A cohort of 91 patients (57M:34F) with unilateral MoMHRAs were included in this study. Blood tests were obtained at a mean follow up of 3.9 years (range 1.7–7 years) and serum (Co:Cr) ion levels were measured (ICPMS). High metal ion concentrations were defined as Co> 4.1ppb and Cr> 5.2ppb. For all patients, head-neck ratio (HNR) was measured on plain anterio-posterior pelvic radiographs pre-operatively, immediately post-operatively and at follow-up.

Results: Female patients had significantly bigger HNR pre-op (mean=1.35, range:1.22–1.64) compared to males(mean=1.22, range:1.05–1.38) (p< 0.01). Immediately post-op, female HNRs (mean: 1.26, range: 1.14–1.34) were not different to male patients(mean=1.24, range=1.11–1.38) (p=0.11). At follow-up HNR was once again significantly bigger (p< 0.01) in females (mean=1.35, range: 1.21–1.49), compare to males (mean=1.27, range:1.11–1.38). HNR alterations with operation (p=0.00) and at follow-up (p< 0.01) were significantly bigger in female patients. Furthermore, there was a significant correlation between high ion levels and HNR change at follow-up for both Co (p=0.02) and Cr (p< 0.01).

Conclusion: This study identified gender-specific changes in HNR that resurfaced hips undergo, not previously documented. Female hips have greater HNR pre-operatively, compared to male hips, and appear to be biomechanically disadvantaged when resurfaced. A decrease in HNR with resurfacing could result in impingement and lead to processes, known to be more prevalent in females, such as neck thinning, increased wear and IP development. In addition, we highlight a correlation between high ion levels and greater neck thinning at follow-up. Increased neck thinning in symptomatic MoMHRA hips could be secondary to increased wear and should be investigated further radiologically for the presence of IP.

Introduction: Metal on metal hip resurfacing arthroplasty (MoMHRA) has become an alternative option to THR in the treatment of young adults with OA. A recognised MoMHRA complication is the development of an inflammatory pseudotumour (IP). IPs can be cystic (predominantly posterio-laterally located), solid (mostly anteriorly located) or mixed in nature. Diagnosis is made with the aid of US and/or MRI. To-date, no radiographic aid in the diagnosis of IP has been identified. Neck thinning is a recognised phenomenon following MoMHRA, occurring in up to 90% of resurfaced hips, which has not been associated with any adverse clinical events. Its pathogenesis is considered multi-factorial secondary to stress shielding, impingement, pressure effect on cancellous femoral neck, bone necrosis secondary to femoral preparation and altered vascularity/AVN. Our aim was to establish whether neck thinning is associated with the presence of a pseudotumour.

Methods: Thirty-one hips (30 patients) with IP confirmed clinically, radiologically, intra-operatively and histologically were matched for sex, age, pre-operative diagnosis, component size and follow-up with an asymptomatic MoMHRA cohort without pseudotumour (Control n=60). Radiological and operative findings at the time of revision of all IP patients were reviewed regarding location of pseudotumour; 4 different locations were defined: anteriorly-extending, posteriorly-extending, anteriorly & posteriorly-extending and within joint only. For all patients, prosthesis-neck ratio (PNR) at follow-up was measured on plain AP pelvic radiographs as previously described and validated.

Results: All IP patients (6M:24F) and all (12M:48F) but two controls had a posterior approach at the time of MoMHRA. Mean femoral component size was 46 mm for both groups. At an average follow up of 3.5 years (0.7–8.3), IP patients (mean 1.26, 1.10–1.79) had a significantly higher (p< 0.0001) PNR in comparison to their controls (mean 1.14, 1.03–1.35). Greater neck thinning had occurred in both IP-males (p< 0.001) and IP-females (p=0.002) in comparison to their controls. Location of IP and hence nature did not appear to have an effect on the degree of neck thinning.

Discussion: This study shows that IP patients had significantly narrower femoral necks at follow-up. Processes, such as impingement and increased wear that are thought to contribute to the process of neck narrowing are also thought to be factors in IP development. Furthermore, the presence of an IP, could lead to altered vascularity via a mass effect and further contribute to neck narrowing. Interestingly, nature of IP did not have a significantly affect PNR. Although one cannot be certain whether neck narrowing is a consequence or a contributing factor for IP development, their association is significant. Surgeons should consider the possibility of pseudotumour in symptomatic MoMHRA patients with neck narrowing.

Introduction: Metal-on-metal hip resurfacing arthroplasty (MoMHRA) has gained popularity as an alternative to THR for younger patients with osteoarthritis. A growing concern has been the association of MoMHRA with the development of inflammatory pseudotumours (IP), especially in women. These have been linked to metal-on-metal wear, which can be related to metal ion concentrations. Although cup orientation has been shown to influence wear, the optimum cup position has not been clearly defined. We have identified an optimal cup orientation to minimise IP risk, based on a case controlled study, for inclination/anteversion within ±10° of 40°/20°. Our aim was to see if this optimal position results in lower metal ions, and to identify the boundary of an optimal placement zone for low wear.

Methods: A cohort of 104 patients (60M: 44F) with unilateral MoMHRA was included in this study. Blood tests were obtained at a mean follow up of 3.9 years (range 1.7–7 years) and serum Co and Cr ion levels were measured (ICPMS). High metal ion concentrations were defined as Co> 4.1ppb and Cr> 5.2ppb. Radiographic cup inclination and anteversion were measured using EBRA. The differences in ion levels between different cup orientation zones were investigated. Three orientation zones were defined centered on the target orientation of 40°/20°: Z1 within ±5°, Z2 outside ±5°/within ±10° and Z3: within ±10°.

Results: There was a wide range of cup placements; mean inclination/anteversion were 46.3°(21.5°–64.6°)/15°(2.7°–35.6°). Cr levels, but not Co, were higher in female patients (p=0.002) and those with small femoral components (< 50mm, p =0.03).

For the whole cohort, there was no significant difference in ion levels (Cr: p=0.092. Co=0.075) between cups positioned within Z3 (n=58) versus those outside (n=46 mean). Male patients with cups within Z3 (n=27) had lower ion levels in comparison to those outside Z3, which were significantly lower for Co (p=0.049) but not Cr (p=0.084). Female patients had similar levels within and out of Z3 for both ions (Cr: p=0.83, Co: p=0.84). However, patients with cups within Z1 (n=13) had significantly lower Co (p=0.005) and Cr (p=0.001) than those outside Z1 (n=95). Interestingly, Co levels were significantly lower in Z1 (n=13) in comparison to Z2 (n=33) (p=0.048) but Cr levels were not different (p=0.06).

Discussion: MoMHRA cups placed with ±5° of the ideal position of 40°/20°gave rise to significantly lower metal ions indicating lower wear within this narrow zone, in both sexes. This safe zone, could be extended to ±10° for male patients only. Gender specific factors, such as pelvic anatomy and joint flexibility, could be responsible for the narrower ‘safe’ zone seen in females. The narrower safe zone coupled with smaller components implanted are factors contributing to higher ion levels and hence the increased incidence of IP seen in females.

Pseudotumour is a rare but important complication of metal-on-metal hip resurfacing that occurs much more commonly in women than in men. We examined the relationship between head-neck ratio (HNR) and pseudotumour formation in 18 resurfaced hips (18 patients) revised for pseudotumour and 42 asymptomatic control resurfaced hips (42 patients).

Patients in whom pseudotumour formation had occurred had higher pre-operative HNR than the control patients (mean 1.37 (sd 0.10) vs mean 1.30 (sd 0.08) p = 0.001). At operation the patients with pseudotumours had a greater reduction in the size of their femoral heads (p = 0.035) and subsequently had greater neck narrowing (mean 10.1% (sd 7.2) vs mean 3.8% (sd 3.2) p < 0.001). No female patient with a pre-operative HNR ≤ 1.3 developed a pseudotumour.

We suggest that reducing the size of the femoral head, made possible by a high pre-operative HNR, increases the risk of impingement and edge loading, and may contribute to high wear and pseudotumour formation. As the incidence of pseudotumour is low in men, it appears safe to perform resurfacing in men. However, this study suggests that it is also reasonable to resurface in women with a pre-operative HNR ≤ 1.3.

Metal on Metal Hip Resurfacing Arthroplasty (MoMHRA) has gained popularity due to its perceived advantages of bone conservation and relative ease of revision to a conventional THR if it fails. Known MoMHRA-associated complications include femoral neck fracture, avascular necrosis/collapse of the femoral head/neck, aseptic loosening and soft tissue responses such as ALVAL and pseudotumours. This study’s aim was to assess the functional outcome of failed MoMHRA revised to THR and compare it with a matched cohort of primary THRs.

Method: We have revised 53 MoMHRA cases to THR; the reasons for revision were femoral neck fracture (Fracture Group, n=21), soft tissue reaction (Pseudotumour Group, n=16) and other causes (Other Group, n=16: loosening, AVN and infection). Average followup was 2.9 years. These MoMHRA revisions were compared with 103 matched controls from a primary THR cohort; matched for age, gender and length of followup. We compared, using the MannWhitney U test, operative time (OT, measured in minutes), and Oxford Hip Score (OHS) between the revised MoMHRA groups and their individual controls. We also compared, using the Kruskal Wallis test, UCLA Activity Score in the revised MoMHRA groups.

Results: There were no differences between the Fracture Group (mean OT 99.6, SD: 30.4; mean OHS 19.8, SD:9.2) and its controls (mean OT 95.9, SD: 31.8; mean OHS 17.3, SD: 7.5) nor between the Other Group (mean OT 129.4, SD: 36.7; mean OHS 22.2, SD: 9.4) and its controls (mean OT 104.4, SD: 39.2; mean OHS 20.3, SD: 10.1) in terms of OT and OHS. The Pseudotumour Group had significantly longer OT (mean 161.6, SD: 24.5, p< 0.001) and worse outcome (mean OHS 39.1, SD: 9.3, p< 0.001) than its controls (mean OT 113.1, SD: 51.7; mean OHS 20.0, SD: 9.2). In the Fracture Group, there were 3 infections requiring revisions. For the Pseudotumour Group, there were 3 recurrent dislocations, 1 femoral artery stenosis and 3 femoral nerve palsies. In the Other Group, there were 2 periprosthetic fractures. There was significant difference (p< 0.001) in UCLA scores between the MoMHRA groups. The Pseudotumour Group had the lowest mean UCLA score of 3.8 (SD: 1.89). The Fracture Group (mean: 7.0, S.D. 2.0) and the Other Group (mean: 6.7, S.D. 2.1) had similar UCLA scores.

Discussion: The results demonstrate that outcome after revision of MoMHRA is dependent upon the indication for revision. Patients revised for soft tissue reactions had significantly worse outcome. Patients with soft tissue reactions are more likely to experience complications and require further surgical intervention. The pseudotumour associated revisions were associated with a significantly prolonged OT. The overall complication rate for the study groups was quite high, with 11 (21%) revised MoMHRA cases experiencing a complication. The Pseudotumour Group had a higher complication rate (37%).

Pseudotumours are a rare complication of hip resurfacing. They are thought to be a response to metal debris which may be caused by edge loading due to poor orientation of the acetabular component. Our aim was to determine the optimal acetabular orientation to minimise the risk of pseudotumour formation.

We matched 31 hip resurfacings revised for pseudotumour formation with 58 controls who had a satisfactory outcome from this procedure. The radiographic inclination and anteversion angles of the acetabular component were measured on anteroposterior radiographs of the pelvis using Einzel-Bild-Roentgen-Analyse software. The mean inclination angle (47°, 10° to 81°) and anteversion angle (14°, 4° to 34°) of the pseudotumour cases were the same (p = 0.8, p = 0.2) as the controls, 46° (29° to 60°) and 16° (4° to 30°) respectively, but the variation was greater. Assuming an accuracy of implantation of ± 10° about a target position, the optimal radiographic position was found to be approximately 45° of inclination and 20° of anteversion. The incidence of pseudotumours inside the zone was four times lower (p = 0.007) than outside the zone.

In order to minimise the risk of pseudotumour formation we recommend that surgeons implant the acetabular component at an inclination of 45° (± 10) and anteversion of 20° (± 10) on post-operative radiographs. Because of differences between the radiographic and the operative angles, this may be best achieved by aiming for an inclination of 40° and an anteversion of 25°.

Introduction: Metal on metal Hip Resurfacing Arthroplasty (MoMHRA) has gained popularity due to its perceived advantages of bone conservation and relative ease of revision to a conventional THR if it fails. This retrospective study is aimed at assessing the functional outcome of failed MoMHRA revised to THR and comparing it with a matched cohort of primary THRs.

Method: Since 1999 we have revised 53 MoMHRA to THR. The reasons for revision were femoral neck fracture (Group A, n=21), pseudotumour (Group B, n=16) and other causes (Group C, n=16: loosening, avascular necrosis and infection). Average follow-up was 3 years months (1.2–7.3). These revisions were compared with 106 primary THRs which were age, gender and follow-up matched with the revision group in a ratio of 2:1.

Results: The mean Oxford Hip Score (OHS) was 20.1 (12–51) for group A, 39.1 (14– 56) for group B, 22.8 (12–39) for group C and 17.8 (12–45) for primary THR group. In group A, there were three infections requiring further revisions. In group B, there were three recurrent dislocations, three patients with femoral nerve palsy and one femoral artery stenosis. In group C, there were no complications. The differences in clinical and functional outcome between group B and the remaining groups as well as the difference in the outcome between group B and control group were statistically significant (p < 0.05).

Conclusions: THR for failed MoMHRA was associated with significantly more complications, operation time and need for blood transfusion for the pseudotumour group. In addition, the revisions secondary to pseudotumour also had significantly worse functional outcome when compared to other MoMHRA revisions or primary THR.