Hip arthroscopy (HA) is an effective treatment for various hip conditions but has a steep learning curve and its effect on long-term joint preservation is unclear. This study uses population-level data to assess (1) the 90-day complication rate, and (2) the frequency and timing of revision HA, total hip replacement (THR), and pelvic osteotomy (PO) following primary HA.

We performed a retrospective analysis of the National Hospital Episode Statistics database, examining all patients who underwent primary HA in NHS hospitals in England from 2010 to 2023 using relevant OPCS-4 codes. We evaluated patient demographics, 90-day complications, and reoperation rates for revision HA, THR, and PO. Descriptive statistical analyses were performed to calculate frequencies and average time to reoperations.

We included 22,401 HA procedures in the study. The mean LOS was 0.82±2.04 days. The 90-day readmission rate was 0.17% at a mean of 54.4±8.1 days. The most common reasons for readmission were reoperation (0.071%), followed by infection (0.031%), pulmonary embolism (0.027%), pain (0.022%), bleeding (0.018%), and deep vein thrombosis (0.004%). One patient died within 90 days.

Overall, 4942 patients (22.1%) required further surgery at a mean of 2.71±2.27 years. The rates of revision HA, conversion to THR, and PO were 6.94%, 14.6%, and 0.50% at a mean of 2.39±1.79, 2.87±2.46, and 2.26±1.80 years respectively. Female patients had higher rates of reoperation than males for conversion to THR (9.99% vs 4.63%), revision HA (4.92% vs 2.02%), and subsequent PO (0.43% vs. 0.06%) (p<0.001).

This study demonstrates a low short-term complication rate after primary HA, supporting existing literature. However, a large proportion of patients required further surgery, especially females. These findings highlight the need for careful patient selection and counselling before HA to optimise outcomes, as well as further research on factors influencing longer-term outcomes and cost-effectiveness.

Hip arthroscopy (HA) and pelvic osteotomy (PO) are surgical procedures used to treat a variety of hip pathology affecting young adults, including femoroacetabular impingement and hip dysplasia respectively. This study aimed to investigate the trends and regional variation in the provision of HA and PO across England from 2010 to 2023 to inform healthcare resource allocation.

We analysed the National Hospital Episode Statistics database for all HA and PO procedures in NHS England using specific OPCS-4 codes: HA: ‘W83+Z843’ or ‘W84+Z843’; PO: ‘X222+Z75’. We collected patient demographics, age, sex, and region of treatment. We performed descriptive and regression analyses to evaluate temporal trends in PO volume, age, sex and regional variation.

22,401 HAs and 1,348 POs were recorded between 2010 and 2023. The annual number of HAs declined by 28.4%, whilst the number of POs increased by 64% (p<0.001). Significantly more females underwent PO vs HA (90% vs 61.3%) and were older than males undergoing the same procedure (PO: 29.0±8.7 vs 25.8±9.2 years; HA: 36.8±12.0 years vs 35.8±11.2 years, p<0.001). For HA, the mean age of both sexes decreased by 3.3 and 2.9 years respectively (p<0.001), whereas the age of PO patients did not change significantly over the study period. There were significant regional variations with a mean incidence of 1.60/100,00 for HA (ranging from 0.70–2.66 per 100,000) and 0.43/100,000 for PO (ranging from 0.08–2.07 per 100,000).

We have observed a decline in HA volume in England, likely due to improved patient selection and the impact of COVID-19, whilst PO volume has significantly increased, with regional variation persisting for both procedures. These trends highlight the need for equitable HA and PO access to improve patient outcomes and call for strategic healthcare planning and resource allocation to reduce disparities and improve training opportunities.

Hip dysplasia is a common cause of hip pain in young adults. Pelvic osteotomy (PO) techniques are the gold standard for treating symptomatic patients, albeit technically demanding. This study aimed to (1) evaluate the 90-day complication rate, and (2) investigate the reasons, frequency and timing of reoperations following primary PO procedures.

We retrospectively analysed the National Hospital Episode Statistics database, examining all patients aged over 14 who underwent PO in NHS England hospitals from 2010 to 2023. We identified index procedures and reoperations using relevant OPCS-4 codes. We analysed patient demographics, 90-day complications, and readmission rates for ipsilateral metalwork removal, revision PO, hip arthroscopy (HA), and THR conversion, and calculated the mean time to reoperations.

This study included 1,348 PO cases (mean age: 28.7±9.1 years, 89.5% female). The mean hospital stay was 5.4±3.9 days, with a 90-day readmission rate of 0.52% at a mean of 51.0±17.2 days. The most common causes were infection (0.22%) and reoperation (0.15%). The 90-day rate of pulmonary embolism and deep vein thrombosis was 0.074%. One patient died within 90 days.

Overall, 810 patients (60.1%) were readmitted for a subsequent hip procedure at a mean of 2.12±1.90 years following their primary PO. Metalwork removal was required in 616 patients (45.7%) at a mean of 1.70±1.19 years. Readmission rates for revision PO, HA, and THR, were 4.23% (mean time: 2.89±0.82 years), 4.15% (mean time: 2.91±2.28 years) and 6.01% (mean time: 5.24±3.08 years) respectively.

This study highlights a low 90-day complication rate following primary PO, but a high reoperation rate, mainly for metalwork removal. We provide the most up-to-date report of revision PO, HA and THR conversion rates in England. These findings provide valuable insight that can facilitate informed decision-making, expectation-setting, and post-operative planning, also establishing a benchmark for future quality improvement.

OpenPredictor, a machine learning-enabled clinical decision aid, has been developed to manage backlogs in elective surgeries. It aims to optimise the use of high volume, low complexity surgical pathways by accurately stratifying patient risk, thereby facilitating the allocation of patients to the most suitable surgical sites. The tool augments elective surgical pathways by providing automated secondary opinions for perioperative risk assessments, enhancing decision-making. Its primary application is in elective sites utilising lighter pre-assessment methods, identifying patients with minimal complication risks and those high-risk individuals who may benefit from early pre-assessment.

The Phase 1 clinical evaluation of OpenPredictor entailed a prospective analysis of 156 patient records from elective hip and knee joint replacement surgeries. Using a polynomial logistic regression model, patients were categorised into high, moderate, and low-risk groups. This categorisation incorporated data from various sources, including patient demographics, co-morbidities, blood tests, and overall health status.

In identifying patients at risk of postoperative complications, OpenPredictor demonstrated parity with consultant-led preoperative assessments. It accurately flagged 70% of patients who later experienced complications as moderate or high risk. The tool's efficiency in risk prediction was evidenced by its balanced accuracy (75.6%), sensitivity (70% with a 95% confidence interval of 62.05% to 76.91%), and a high negative predictive value (96.7%).

OpenPredictor presents a scalable and consistent solution for managing elective surgery pathways, comparable in performance to secondary consultant opinions. Its integration into pre-assessment workflows assists in efficient patient categorisation, reduces late surgery cancellations, and optimises resource allocation. The Phase 1 evaluation of OpenPredictor underscores its potential for broader clinical application and highlights the need for ongoing data refinement and system integration to enhance its performance.

This study used a national registry to assess the outcomes of hip arthroscopy (HA) for the treatment femoroacetabular impingement (FAI).

All HAs for FAI recorded in the UK Non-Arthroplasty Hip Registry (NAHR) between January 2012 and September 2023 were identified. Cases were grouped according to the index procedure performed for FAI (cam, pincer, or mixed). Patient outcomes captured included the International Hip Outcome Tool (iHOT)-12.

7,511 HAs were identified; 4,583 cam (61%), 675 pincer (9%), 2,253 mixed (30%). Mean age (34.8) was similar between groups. There was a greater proportion of females in the pincer group (75%) compared to cam (52%) and mixed (50%). A higher proportion of patients had a recorded cartilage injury in association with a cam lesion compared to pincer. The pincer group had poorer mean pre-op iHOT-12 scores (31.6 \[95%CI 29.9 to 33.3\]; n=364) compared to cam (33.7 \[95%CI 32.1 to 34.4\]; n=3,941) and achieved significantly lower scores at 12 months (pincer = 52.6 (50.2 to 55); n=249, cam = 58.3 (57.1 to 59.5); n=1,679).

Overall, significant (p < 0.0001) iHOT-12 and EQ-5D improvement vs baseline pre-operative scores were achieved for all FAI subtypes at 6 months (overall mean iHOT-12 improvement +26.0 \[95%CI 25.0 to 26.9\]; n=2,983) and maintained out to 12 months (+26.2 \[25.1 to 27.2\]; n=2,760) at which point 67% and 48% of patients continued to demonstrate a score improvement greater than or equal to the minimum clinically important difference (>/=13 points) and substantial clinical benefit (>/=28 points) for iHOT-12 respectively.

This study demonstrates excellent early functional outcomes following HA undertaken for FAI in a large national registry.

There is little known about how patient socioeconomic status impacts clinical outcomes in hip preservation surgery. The aim of this study was to evaluate the relationship between indices of multiple deprivation, funding provider (NHS Funded or Private Funded) and clinical outcomes following surgery for femoroacetabular impingement (FAI)

The study analysed the data of 5590 patients recorded in the NAHR who underwent primary hip arthroscopic treatment for FAI between November 2013 and July 2023. Records were matched to the UK National index of multiple deprivation using the lower layer super output area. Using iHOT12 score, patient reported outcome measures were analysed at base line and 1 year following surgery.

2358 records were matched to LLSOA deciles. Between the lowest (most deprived) 3 deciles and the highest (least deprived) the average baseline iHOT12 score was 28.98 (n=366) and 35.33 (n=821). The proportion of patients receiving treatment through NHS funding compared to independent funding for the most deprived, 292 (90%) 37 (10%) respectively compared to the least deprived 515 (70%) and 244 (30%) respectively. At 1year, iHOT12 scores for each group were 51.64 (29.1 SD) compared to 61.5 (28.06 SD) respectively.

The study demonstrates that patients from lower socioeconomic backgrounds had poorer baseline and one-year post-surgery iHOT12 scores compared to those from higher socioeconomic strata. Furthermore, a higher reliance on NHS funding was observed among the most deprived, while more affluent patients predominantly opted for private funding. These findings underscore the significant influence of socioeconomic status on both the quality of healthcare received and recovery outcomes in hip preservation surgery, calling attention to the need for more equitable healthcare solutions.

Femoroacetabular Impingement (FAI) syndrome, characterised by abnormal hip contact causing symptoms and osteoarthritis, is measured using the International Hip Outcome Tool (iHOT). This study uses machine learning to predict patient outcomes post-treatment for FAI, focusing on achieving a minimally clinically important difference (MCID) at 52 weeks.

A retrospective analysis of 6133 patients from the NAHR who underwent hip arthroscopic treatment for FAI between November 2013 and March 2022 was conducted. MCID was defined as half a standard deviation (13.61) from the mean change in iHOT score at 12 months. SKLearn Maximum Absolute Scaler and Logistic Regression were applied to predict achieving MCID, using baseline and 6-month follow-up data. The model's performance was evaluated by accuracy, area under the curve, and recall, using pre-operative and up to 6-month postoperative variables.

A total of 23.1% (1422) of patients completed both baseline and 1-year follow-up iHOT surveys. The best results were obtained using both pre and postoperative variables. The machine learning model achieved 88.1% balanced accuracy, 89.6% recall, and 92.3% AUC. Sensitivity was 83.7% and specificity 93.5%. Key variables determining outcomes included MCID achievement at 6 months, baseline iHOT score, 6-month iHOT scores for pain, and difficulty in walking or using stairs.

The study confirmed the utility of machine learning in predicting long-term outcomes following arthroscopic treatment for FAI. MCID, based on the iHOT 12 tools, indicates meaningful clinical changes. Machine learning demonstrated high accuracy and recall in distinguishing between patients achieving MCID and those who did not. This approach could help early identification of patients at risk of not meeting the MCID threshold one year after treatment.

Adult hip dysplasia AHD is a complex 3D pathology of lateral coverage, version and/or volume and is often associated with increased femoral anteversion. The Mckibbin index MI is the combination of acetabular version AV and femoral version FV and is used as a measure of anterior hip Stability/ Impingement(1). The Bernese Periacetabular osteotomy PAO is a powerful tool in treating AHD, but it does not address FV. De-rotational femoral osteotomies FO increases risk of complications, operative time and might condemn the patient to Secondary osteotomies to balance the gait. We aim to investigate the effect of MI and FV on PROMs in patients undergoing PAO only.

593 PAOs identified on the Local Hip preservation registry between 01/2013 and 7/2023. PAOs for retroversion, residual Perthes and those combined with FO were excluded. Patients with no available PROMS at 2 years were excluded. Independent variables were collected from E-notes and imaging including MI and FV. A multiple linear regression analysis was performed against preoperative iHot12, and iHot12 change at 2years.

The mean FV was 18.86± 12.4 SD. Mean MI was 36.07, SD 15.36. Mean preop iHot12 score was 29.83 ± 17.38 SD. Mean change in iHot12 at 2 years was+36.47 ± 28.44 SD. Females and a higher BMI were statistically correlated to a lower preoperative iHot12. A lower preop iHot12 score and a higher preop AI were correlated to a bigger change in iHot12 at 2years with statistical significance. MI and FV were not found to have a statistically significant correlation with Outcome measures,

An increased Mckibbin index and femoral anteversion were not correlated with worse outcomes at two years. PAO alone in the presence of increased femoral anteversion avoids risks associated with FO which can be performed later if required.

MCID and PASS are thresholds driven from PROMS to reflect clinical effectiveness. Statistical significance can be derived from a change in PROMS, whereas MCID and PASS reflect clinical significance. Its role has been increasingly used in the world of young adult hip surgery with several publications determining the thresholds for Femoro-acetabular impingement FAI. To our knowledge MCID and PASS for patient undergoing PAO for dysplasia has not been reported.

593 PAOs between 1/2013 and 7/2023 were extracted from the Northumbria Hip Preservation Registry. Patients with available PROMS at 1year and/or 2years were included. PAOs for retroversion, residual Perthes and those combined with FO were excluded. MCID was calculated using the distribution method 0.5SD of baseline score(1). PASS was calculated using anchor method, ROC analysis performed, and value picked maximizing Youden index. A Logistic Regression analysis was performed to determine which independent variables correlated with achieving MCID and PASS.

The MCID threshold for iHOt12 was 8.6 with 83.4 and 86.3 % of patients achieved it at 1 and 2 years respectively. The PASS score at 1 and 2 year follow up was 43 and 44 respectively, with 72.6 and 75.2% achieving it at 1 and 2 year postop. At 2 years a Higher preop iHOT 12 was associated with not achieving MCID and PASS (p<0.05). Preop acetabular version was negatively correlated with achieving MCID and previous hip arthroscopy was negatively correlated with PASS.

The % of patients achieving MCID and PASS mimics that of FAI surgery (2). The negative correlation with preop iHOT12 reaffirms the importance of patient selection. The negative correlation of hip arthroscopy highlights the importance of having a high index of suspicion for dysplasia prior to hip arthroscopy and poorer outcomes of patients with mixed CAM and dysplasia pathology.

Periacetabular osteotomy (PAO) is an established treatment for developmental hip dysplasia (DDH) in young adults and can also be utilised in the management of femoroacetabular impingement (FAI) with acetabular retroversion. This study used a national registry to assess the outcomes of PAO for DDH and FAI.

PAOs recorded in the UK Non-Arthroplasty Hip Registry between 2012 and November 2022 were identified along with recorded patient and surgical characteristics. Cases were grouped according to the primary pathology (DDH or FAI). Patient reported outcome measures (PROMs) captured included the International Hip Outcome Tool (iHOT)-12 (primary outcome) and the EuroQol-5 Dimensions (EQ-5D) index preoperatively and at 6 months, 1, 2, and 5 years post-operatively.

1,087 PAOs were identified; 995 for DDH (91%), 98 for FAI (9%). Most patients (91%) were female. The DDH group were significantly older (mean 31.7 years) than the FAI group (25.4 years) but had similar body mass index (mean 25.7kg/m2). Overall, significant (all p<0.0001) iHOT-12 and EQ-5D improvement (delta) vs baseline pre-operative scores were achieved at 6 months (mean iHOT-12 improvement +27.4 (95%CI 25.3 to 29.5); n=515) and maintained out to 5 years (+30.0 (21.4 to 38.6); n=44 [9.8% of those eligible for follow-up at 5 years]), at which point 71% and 55% of patients continued to demonstrate a score improvement greater than or equal to the minimum clinically important difference (≥13 points) and substantial clinical benefit (≥28 points) for iHOT-12 respectively.

This study demonstrates excellent functional outcomes following PAO undertaken for DDH and FAI in the short to medium term in a large national registry.

Abstract

Abstract

Aims

This study uses prospective registry data to compare early patient outcomes following arthroscopic repair or debridement of the acetabular labrum.

Young adult hip pathology commonly affects patients of reproductive age. The extent to which hip arthroscopy (HA) treatments influence sexual function is not well described and limited to small cohorts. This study aims to describe trends in self-reported reported sexual function before and after HA.

Adult (≥18 years) patients who underwent HA between 1^st January 2012 and 31^st October 2020 were extracted from the UK Non-Arthroplasty Hip Registry. International Hip Outcome Tool 12 (iHOT-12) questionnaires were collected pre-operatively and at 6 and 12 months. Patients are first asked if ‘questions about sexual activity are relevant to them’. The iHOT-12 then asks asking patients to quantify ‘how much trouble they experience with sexual activity because of their hip?’ with responses converted to a continuous scale (0–100) to measure function. Chi-squared and t-tests were used to compare categorical and continuous variables respectively.

Of 7639 procedures (59% female, mean age 36.5 years (SD 11)), 91% (5616 of 6151 respondants) indicated pre-operatively that questions about sexual activity were relevant to them (male 93%, female 90%, p < 0.001). Overall, mean pre-operative sexual function increased from 42.0 (95%CI 41.2 to 42.8, n=5267) to 61.8 (60.6 to 63.1, n=2393) at 6 months, and 62.1 (60.8 to 63.5, n=2246) at 12 months post-operatively.

At 12 months, both sexes saw significant improvement in their pre-operative sexual function scores (p<0.0001). Males started from significantly higher baseline sexual function (53.3 vs 34.2) and achieved higher scores by 12 months (68.8 vs 58.0) compared to female patients. There was no significant difference in pre- or post-operative scores when comparing younger (<40 years) and older (>40 years).

Most patients can expect to experience improvement in their sexual function following hip arthroscopy, regardless of sex or age group.

Periprosthetic joint infection (PJI) causes significant morbidity. Methicillin sensitive Staphylococcus Aureus (MSSA) is the most frequent organism, and the majority are endogenous. Nasal MSSA colonisation is a proven risk factor for S. aureus infection. Decolonisation reduces PJIs but there is a paucity of evidence comparing treatments. Aims; compare 3 nasal decolonisation treatments at (1) achieving MSSA decolonisation, (2) preventing PJI.

Our hospital trust introduced MSSA screening and decolonisation prior to hip and knee arthroplasty in 2010. Data was prospectively collected since 2013, including all MSSA carriers, decolonisation treatment received, MSSA status at time of surgery and all PJIs. Prior to 2017 MSSA carriers received nasal mupirocin or neomycin, from August 2017 until August 2019 nasal octenidine was used.

During the study period 15,958 primary hip and knee replacements were performed. 3,200 (20.1%) were MSSA positive at preoperative screening and received decolonisation treatment, 698 mupirocin, 1,210 neomycin and 1,221 octenidine. Mupirocin (89.1%) and neomycin (90.9%) were more effective at decolonisation than octenidine (50.0%, P<0.0001). There was no difference in S. aureus PJI rates (P=0.452). Of those negative at original screening 9.1% were positive on the day of surgery (1,164/12,758).

MSSA decolonisation is an effective method to decrease PJI rates but there is little research into the best treatment. Both mupirocin and neomycin are more effective than octenidine at achieving MSSA decolonisation. There was poor correlation between the MSSA status after treatment and PJI rates. There is debate if treatment should be targeted by screening or if all patients she be treated without screening. Global decolonisation without screening is supported by the 26.7% of carriers that were negative at original screening in our study.

Further research is needed comparing decolonisation treatments to reduce PJI rates and avoid the risk of drug resistance.

This study aims to describe the characteristics and outcomes of patients who reported their pre-operative quality of life (QoL) was ‘worse than death’ (‘WTD’) prior to hip arthroscopy (HA) or peri-acetabular osteotomy (PAO).

Adult patients who underwent HA or PAO between 1^st January 2012 and 31^st October 2020 were extracted from the UK Non-Arthroplasty Hip Registry. International Hip Outcome Tool 12 (iHOT-12) and EuroQol-5 Dimensions (EQ-5D) index questionnaires were collected pre-operatively and at 6 and 12 months. WTD was defined as an EQ-5D score of less than zero. Chi-squared and t-tests were used to compare categorical and continuous variables respectively.

8493 procedures (6355 HA, 746 PAO) were identified in whom 7101 (84%) returned pre-operative EQ-5D questionnaires. 283 HA and 52 PAOs declared their pre-operative QoL to be ‘WTD’. Compared to those patients with pre-operative QoL ‘better than death’ (n=6072, control group) (EQ-5D ≥ zero) patients reporting ‘WTD’ function prior to HA were more likely to be female (66% vs 59%, p = 0.013), of higher body mass index (mean 27.6 kg/m² (SD 5.9) vs 25.7 kg/m² (4.5), p < 0.0001) however there were no statistically significant differences in mean age (36.8 vs 36.4 years), femoroacetabular impingement pattern, or femoral or acetabular cartilage lesion severity. There were no significant demographic differences for PAO.

For HA, iHOT-12 scores in WTD patients were significantly poorer pre- [10.8 (95% CI 9.6 to 12.0) vs 33.3 (32.8 to 33.8)] and 12 months post-operatively [34.9 (29.0 to 40.8) vs 59.3 (58.2 to 60.4)] compared to controls. Whilst the majority of patients saw improvement in their scores (p <0.0001), a significantly smaller proportion achieved the minimum clinically important difference for iHOT-12 by 12 months. (51% in the WTD group vs 65% in the control group). Similar trends were observed for PAO.

Patients with WTD quality of life may benefit less from hip preservation surgery and should be counselled accordingly regarding expectations. Although the scores improve, only 51% achieve scores beyond MCID.

This trial aims to assess the effectiveness of quality improvement collaboratives as a technique to introduce large-scale change and improve outcomes for patients undergoing primary elective total hip or total knee arthroplasty.

41 NHS Trusts that did not have; a preoperative anaemia screening and optimisation pathways, or a methicillin sensitive Staphylococcus Aureus (MSSA) decolonisation pathway, in place were randomised to one of two parallel collaboratives in a two arm, cluster randomised controlled trial. Each collaborative focussed on implementing one of these two preoperative pathways. Collaboratives took place from May 2018 to November 2019. 27 Trusts completed the trial. Outcome data were collected for procedures between November 2018 and November 2019.

Co-primary outcomes were perioperative blood transfusion (within 7 days of surgery) and deep surgical site infections (SSI) caused by MSSA (within 90 days) for the anaemia and MSSA arms respectively. Secondary outcomes include deep and superficial SSIs (any organism), length of stay, critical care admissions, and readmissions. Process measures include the proportion of patients receiving each preoperative initiative.

19,254 procedures from 27 Trusts are included. Process measures show both preoperative pathways were implemented to a high degree (75.3% compliance in MSSA arm; 61.2% anaemia arm), indicating that QICs can facilitate change in the NHS. However, there were no improvements in blood transfusions (2.9% v 2.3% adjusted-OR 1.20, 95% CI 0.52–2.75, p=0.67), MSSA deep SSIs (0.13% v 0.14% adjusted-OR 1.01, 95%CI 0.42–2.46, p=0.98), or any secondary outcome.

Whilst no significant improvement in patient outcomes were seen, this trial shows quality improvement collaboratives can successfully support the implementation of new preoperative pathways in planned surgery in the NHS.

Modular femoral stems offer surgeons great flexibility in biomechanical configuration during total hip replacement (THR) however introduce a taper-trunnion articulation known to be a source of additional wear debris through crevice, fretting and galvanic corrosion with mixed material combinations. This study aimed to investigate the influence of the trunnion bearing surface combination on the revision rate following primary total hip replacement (THR).

All patients who underwent THR using an Exeter V40 cemented stainless steel stem and monobloc cemented polyethylene acetabular component (uncemented cups excluded to standardise the acetabular bearing surface and fixation) between January 2003 and December 2019 were extracted from the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man. The primary exposure was the head substrate used corresponding to the trunnion bearing.

Time-to-event was determined by duration of implantation from primary surgery to revision with cases censored at death or end of available follow-up. Multivariable Cox proportional hazard models were used to identify predictors of all cause revision, adjusted for age, sex, American Association of Anaesthesiologists (ASA) grade, body mass index, surgical indication (osteoarthritis or other), and femoral head size.

229,870 THR were identified (66% female, mean age 73.4 years (SD 9.1) with the majority (91%) performed for osteoarthritis of which 4,598 were revised. Mean time from primary to revision or censoring was 6.8 years (SD 4.0).

Multivariable modelling showed CoCr/SS trunnions were associated with a significantly higher risk of revision (hazard ratio (HR) 1.31 (95%CI 1.15 to 1.48, p<0.0001) as compared to SS/SS (reference). Both Alumina/SS (HR 0.74 (0.65 to 0.84), p<0.0001) and Zirconia/SS (HR 0.61 (0.49 to 0.74), p<0.0001) were associated with a significantly lower risk of revision

Ceramic heads on an Exeter stem were associated with significantly improved survivorship compared to metal heads in primary THR. CoCr/SS trunnion articulations had the poorest survivorship which may be contributed to by trunnionosis.

Identification of patients at risk of not achieving minimally clinically important differences (MCID) in patient reported outcome measures (PROMs) is important to ensure principled and informed pre-operative decision making. Machine learning techniques may enable the generation of a predictive model for attainment of MCID in hip arthroscopy.

Aims: 1) to determine whether machine learning techniques could predict which patients will achieve MCID in the iHOT-12 PROM 6 months after arthroscopic management of femoroacetabular impingement (FAI), 2) to determine which factors contribute to their predictive power.

Data from the UK Non-Arthroplasty Hip Registry database was utilised. We identified 1917 patients who had undergone hip arthroscopy for FAI with both baseline and 6 month follow up iHOT-12 and baseline EQ-5D scores. We trained three established machine learning algorithms on our dataset to predict an outcome of iHOT-12 MCID improvement at 6 months given baseline characteristics including demographic factors, disease characteristics and PROMs. Performance was assessed using area under the receiver operating characteristic (AUROC) statistics with 5-fold cross validation.

The three machine learning algorithms showed quite different performance. The linear logistic regression model achieved AUROC = 0.59, the deep neural network achieved AUROC = 0.82, while a random forest model had the best predictive performance with AUROC 0.87. Of demographic factors, we found that BMI and age were key predictors for this model. We also found that removing all features except baseline responses to the iHOT-12 questionnaire had little effect on performance for the random forest model (AUROC = 0.85). Disease characteristics had little effect on model performance.

Machine learning models are able to predict with good accuracy 6-month post-operative MCID attainment in patients undergoing arthroscopic management for FAI. Baseline scores from the iHOT-12 questionnaire are sufficient to predict with good accuracy whether a patient is likely to reach MCID in post-operative PROMs.

Greater trochanteric pain syndrome is a painful condition characterised by pain around the greater trochanter usually affecting middle-aged women. The majority of patients will improve with conservative management such as physiotherapy and non-steroidal anti-inflammatory drugs (NSAIDs); however, if this fails then more invasive treatments including corticosteroids and surgery may be required. Platelet-rich plasma (PRP) is an autologous blood product, which has a higher concentration of growth factors postulated to provide enhanced healing and anti-inflammatory properties. The Hip Injections PRP Vs Placebo (HIPPO) trial aims to assess the ability of ultrasound-guided PRP injections to improve symptoms and function in patients with GTPS.

64 patients were enrolled and randomised to either the PRP or placebo (normal saline) treatment arm. Two patients decided to drop out of the trial. Clinical outcomes in both groups were evaluated and compared using the International Hip Outcome Tool-12 (iHOT12), Visual Analogue Scale (VAS) of pain, the modified Harris Hip Score (mHHS) and the presence or absence of complications at 3 and six months. The level of significance was set at p<0.05. Both groups received physiotherapy after the injections.

The mean age was 57.5. There were 6 males and 56 females with M:F ratio of 1:9.3. Both groups were similar in terms of demography and preoperative scores. The iHOT12 score improved from 28.23 to 45.42 at three-months and decreased slightly to 42.44 at six-months in the Placebo group. The iHOT12 in the PRP group improved from 35.51 to 44.47 at three-months and decreased to 39.78 at six-months. Both groups showed improved VAS and mHHS at three-months compared to the baseline with no statistically significant difference between the two groups (p >0.05). The scores decreased at six-months however remained above the baseline. No complications were reported. Gender and age had no effect on outcomes.

Both groups similarly improved from baseline. Physiotherapy can be considered as an important factor in patients' treatment. Further research should be conducted to investigate the role of physiotherapy in the treatment of GTPS.