How Is Variability in Femoral and Acetabular Version Associated With Presentation Among Young Adults With Hip Pain?

BACKGROUND: Acetabular and femoral version contribute to hip pain in patients with femoroacetabular impingement (FAI) or dysplasia. However, definitions and measurement methods of femoral version have varied in different studies, resulting in different "normal" values being used by clinicians for what should be the same anatomic measurement. This could result in discrepant or even inappropriate treatment recommendations. QUESTIONS/PURPOSES: In patients undergoing hip preservation surgery, (1) what is the range of acetabular and femoral version at presentation, and how much do two commonly used measurement techniques (those of Murphy and Reikerås) differ? (2) How are differences in acetabular and femoral version associated with clinical factors and outcomes scores at the time of presentation? METHODS: This was a retrospective analysis of data gathered in a longitudinally maintained database of patients undergoing hip preservation at a tertiary care referral center. Between June 2020 and December 2021, 282 hips in 258 patients were treated for an isolated labral tear (9% [26 hips]), hip dysplasia (21% [59 hips]), FAI (52% [147 hips]), mixed FAI and dysplasia (17% [47 hips]), or pediatric deformity (slipped capital femoral head epiphysis or Perthes disease; 1% [3 hips]) with hip arthroscopy (71% [200 hips]), periacetabular osteotomy (26% [74 hips]), surgical hip dislocation (2.5% [7 hips]), or femoral derotation osteotomy (0.5% [1 hip]). We considered those with complete radiographic data (CT including the pelvis and distal femur) and patient-reported outcome scores as potentially eligible. Exclusion criteria were age younger than 18 or older than 55 years (5 hips, 3 patients), signs of hip osteoarthritis (Tönnis grade ≥ 2; 0), pediatric deformity (slipped capital femoral head epiphysis or Perthes disease; 3 hips, 3 patients), previous femoral or acetabular osteotomy (2 hips, 2 patients), avascular necrosis of the femoral head (0), history of neuromuscular disorder (Ehlers-Danlos syndrome; 3 hips, 3 patients) or rheumatoid disease (ankylosing spondylitis; 1 hip, 1 patient), and when CT did not include the knees (19 hips, 19 patients). Based on these criteria, 249 hips in 227 patients were included. Of patients with bilateral symptomatic hips, one side was randomly selected for inclusion, leaving 227 hips in 227 patients for further analysis. The patients' median age (range) was 34 years (19 to 55 years), the median BMI (range) was 27 kg/m2 (16 to 55 kg/m2), and 63% (144) were female; they were treated with hip arthroscopy (in 74% [168]) or periacetabular osteotomy (in 23% [52]). Patients underwent a CT scan to measure acetabular version and femoral version using the Murphy (low < 10°; normal: 10° to 25°; high > 25°) or Reikerås (low < 5°; normal: 5° to 20°; high > 20°) technique. The McKibbin index was calculated (low: < 20°; normal: 20° to 50°; high > 50°). Based on the central acetabular version and femoral version as measured by Murphy, hips were grouped according to their rotational profile into four groups: unstable rotational profile: high (high acetabular version with high femoral version) or moderate (high acetabular version with normal femoral version or normal acetabular version with high femoral version); normal rotational profile (normal acetabular version with femoral version); compensatory rotational profile (low acetabular version with high femoral version or high acetabular version with low femoral version); and impingement rotational profile (low acetabular version with low femoral version): high (low acetabular version with low femoral version) or moderate (low acetabular version with normal femoral version or normal acetabular version with low femoral version). Radiographic assessments were manually performed on digitized images by two orthopaedic residents, and 25% of randomly selected measurements were repeated by the senior author, a fellowship-trained hip preservation and arthroplasty surgeon. Interobserver and intraobserver reliabilities were calculated using the correlation coefficient with a two-way mixed model, showing excellent agreement for Murphy technique measurements (intraclass correlation coefficient 0.908 [95% confidence interval 0.80 to 0.97]) and Reikerås technique measurements (ICC 0.938 [95% CI 0.81 to 0.97]). Patient-reported measures were recorded using the International Hip Outcome Tool (iHOT-33) (0 to 100; worse to best). RESULTS: The mean acetabular version was 18° ± 6°, and mean femoral version was 24° ± 12° using the Murphy technique and 12° ± 11° with the Reikerås method. Eighty percent (181 of 227) of hips had normal acetabular version, 42% (96 of 227) to 63% (142 to 227) had normal femoral version per Murphy and Reikerås, respectively, and 67% (152 to 227) had a normal McKibbin index. Patients with an impingement profile (low acetabular version or femoral version) were older (39 ± 9 years) than patients with an unstable (high acetabular version or femoral version; 33 ± 9 years; p = 0.004), normal (33 ± 9 years; p = 0.02), or compensatory (high acetabular version with low femoral version or vice versa; 33 ± 7 years; p = 0.08) rotational profile. Using the Murphy technique, femoral version was 12° greater than with the Reikerås method (R2 0.85; p < 0.001). There were no differences in iHOT-33 score between different groups (impingement: 32 ± 17 versus normal 35 ± 21 versus compensated: 34 ± 20 versus unstable: 31 ± 17; p = 0.40). CONCLUSION: Variability in femoral version is twice as large as acetabular version. Patients with an impingement rotational profile were older than patients with a normal, compensatory, or unstable profile, indicating there are other variables not yet fully accounted for that lead to earlier pain and presentation in these groups. Important differences exist between measurement methods. This study shows that different measurement methods for femoral anteversion result in different numbers; if other authors compare their results to those of other studies, they should use equations such as the one suggested in this study. LEVEL OF EVIDENCE: Level III, prognostic study.

Two-Year Results of Ceramic-on-Ceramic Hip Resurfacing in an International Multicenter Cohort.

BACKGROUND: Hip resurfacing arthroplasty (HRA) is a bone-conserving alternative to total hip arthroplasty. We present the 2-year clinical and radiographic follow-up of a novel ceramic-on-ceramic HRA in an international multicenter cohort. METHODS: Patients undergoing HRA between September 2018 and January 2021 were prospectively included. Patient-reported outcome measures (PROMs) in the form of the Forgotten Joint Score, Hip Disability and Osteoarthritis Outcome Score Jr., Western Ontario and McMaster Universities Arthritis Index, Oxford Hip Score, and University of California, Los Angeles, Activity Score were collected preoperatively, and at 1 and 2 years postoperation. Serial radiographs were assessed for migration, component alignment, evidence of osteolysis or loosening, and heterotopic ossification formation. RESULTS: The study identified 200 patients who reached a minimum 2-year follow-up (mean 3.5 years). Of these, 185 completed PROMs follow-up at 2 years. There was a significant improvement in Hip Disability and Osteoarthritis Outcome Score (P < .001) and Oxford Hip Score (P < .001) between the preoperative, 1-year, and 2-year outcomes. Patients had improved activity scores on the University of California, Los Angeles, Active Score (P < .001), with 45% reporting a return to high-impact activity at 2 years. At 1 and 2 years, the Forgotten Joint Score was not significantly different (P = .38). There was no migration, osteolysis, or loosening of any of the implants. No fractures were reported over the 2-year follow-up, with only 1 patient reporting a sciatic nerve palsy. There were 2 revisions, 1 for unexplained pain at 3 months due to acetabular component malposition and 1 at 33.5 months for acetabular implant failure. CONCLUSIONS: The ceramic-on-ceramic resurfacing at 2 years postoperation demonstrates promising results with satisfactory outcomes in all recorded PROMs. Further long-term data are needed to support the widespread adoption of this prosthesis as an alternative to other HRA bearings.

The Otto Aufranc Award: Does Hip Arthroscopy at the Time of Periacetabular Osteotomy Improve the Clinical Outcome for the Treatment of Hip Dysplasia? A Multicenter Randomized Clinical Trial.

BACKGROUND: A periacetabular osteotomy (PAO) is often sufficient to treat the symptoms and improve quality of life for symptomatic hip dysplasia. However, acetabular cartilage and labral pathologies are very commonly present, and there is a lack of evidence examining the benefits of adjunct arthroscopy to treat these. The goal of this study was to compare the clinical outcome of patients undergoing PAO with and without arthroscopy, with the primary end point being the International Hip Outcome Tool-33 at 1 year. METHODS: In a multicenter study, 203 patients who had symptomatic hip dysplasia were randomized: 97 patients undergoing an isolated PAO (mean age 27 years [range, 16 to 44]; mean body mass index of 25.1 [range, 18.3 to 37.2]; 86% women) and 91 patients undergoing PAO who had an arthroscopy (mean age 27 years [range, 16 to 49]; mean body mass index of 25.1 [17.5 to 25.1]; 90% women). RESULTS: At a mean follow-up of 2.3 years (range, 1 to 5), all patients exhibited improvements in their functional score, with no significant differences between PAO plus arthroscopy versus PAO alone at 12 months postsurgery on all scores: preoperative International Hip Outcome Tool-33 score of 31.2 (standard deviation [SD] 16.0) versus 36.4 (SD 15.9), and 12 months postoperative score of 72.4 (SD 23.4) versus 73.7 (SD 22.6). The preoperative Hip disability and Osteoarthritis Outcome pain score was 60.3 (SD 19.6) versus 66.1 (SD 20.0) and 12 months postoperative 88.2 (SD 15.8) versus 88.4 (SD 18.3). The mean preoperative physical health Patient-Reported Outcomes Measurement Information System score was 42.5 (SD 8.0) versus 44.2 (SD 8.8) and 12 months postoperative 48.7 (SD 8.5) versus 52.0 (SD 10.6). There were 4 patients with PAO without arthroscopy who required an arthroscopy later to resolve persistent symptoms, and 1 patient from the PAO plus arthroscopy group required an additional arthroscopy. CONCLUSIONS: This randomized controlled trial has failed to show any significant clinical benefit in performing hip arthroscopy at the time of the PAO at 1-year follow-up. Longer follow-up will be required to determine if hip arthroscopy provides added value to a PAO for symptomatic hip dysplasia.

Prevalence of anemia and association with outcome in joint arthroplasty - is there a difference between primary and revision cases?

PURPOSE: Anemia has been shown to be a modifiable pre-operative, patient factor associated with outcome following arthroplasty. The aims of this retrospective study were to (1) ascertain the prevalence of preoperative anemia in patients undergoing primary and revision hip and knee arthroplasty at a tertiary referral center and (2) to test the association with outcome and whether it differs between primary and revision cases. METHODS: All hip and knee primary and revision arthroplasties performed at a Canadian academic, tertiary-care, arthroplasty center between 2012 and 2017 were included in this study. The study group consisted of 5944 patients, of which 5251 were primary Total Hip and Knee Arthroplasties or Hip Resurfacings and 693 were revision arthroplasties (65% hip revisions/35% knee revisions). Anemia was classified as per WHO definition (hemoglobin < 130 g/L for men and < 120 g/L for women). All anemic patients were grouped into mild, moderate or severe anemia. Length-of-stay, perioperative transfusion-rate, 90-day readmission, overall complication rate and reoperation rates were recorded. The effect of preoperative anemia and the effect of severity of the anemia was evaluated through multivariable regression analysis controlling for relevant covariates. RESULTS: Preoperatively, 15% (786/5251) of the primary patients and 47% (322/693) of the revision arthroplasty patients were anemic preoperatively. Anemic revision patients were 3.1 times more likely (95% CI: 1.47-6.33) to obtain blood transfusions during the hospital stay, compared to a 4.9 times higher risk in primary patients. The odds ratio to sustain any postoperative complication if anemic was 1.5 times higher (95% CI: 0.73-3.16) in revision patients and 1.7 in primary cases. In addition, the 90-day readmission rate among both groups was 1.6 times higher in anemic patients. Furthermore, anemic revision patients had a 5.3 days longer length of stay (95% CI: 2.63-7.91), compared to only 1 additional day in anemic primary patients (95% CI: 0.69-1.34). CONCLUSION: In this study cohort, the prevalence of anemia in patients awaiting revision arthroplasty was 3 times higher (46.6%) than in primary arthroplasty patients (18.7%). Preoperative anemia was associated with similarly, inferior outcomes in both groups. To reduce postoperative complications and the "burden" associated with anemia, these findings strongly recommend optimizing the preoperative hemoglobin in all arthroplasty patients. However, revision patients are affected more frequently, and particular attention must therefore be taken to this growing group in the future. LEVEL OF EVIDENCE: Level III.

Strategies to Manage Poorer Outcomes After Hip or Knee Arthroplasty: A Narrative Review of Current Understanding, Unanswered Questions, and Future Directions.

PURPOSE: Although hip or knee arthroplasty is generally a successful intervention, it is documented that 15%-30% of patients undergoing arthroplasty report suboptimal outcomes. This narrative review aims to provide an overview of the key findings concerning the management of poorer outcomes after hip or knee arthroplasty. METHOD: A comprehensive search of articles was conducted up to November 2023 across three electronic databases. Only studies written in English were included, with no limitations applied regarding study design and time. RESULT: Efficiently addressing poorer outcomes after arthroplasty necessitates a thorough exploration of appropriate methods for assessing recovery following hip or knee arthroplasty, ensuring accurate identification of patients at risk or experiencing poorer recovery. When selecting appropriate outcome measure tools, various factors should be taken into consideration, including understanding patients' priorities throughout the recovery process, assessing psychometric properties of outcome measure tools at different time points after arthroplasty, understanding how to combine/reconcile provider-assessed and patient-reported outcome measures, and determining the appropriate methods to interpret outcome measure scores. However, further research in these areas is warranted. In addition, the identification of key modifiable factors affecting outcomes and the development of interventions to manage these factors are needed. CONCLUSION: There is growing attention paid to delivering interventions for patients at risk or not optimally recovering following hip or knee arthroplasty. To achieve this, it is essential to identify the most appropriate outcome measure tools, factors associated with poorer recovery and management of these factors.

Development and content validation of a questionnaire identifying patients' functional priorities and abilities after hip or knee arthroplasty.

PURPOSE: To develop a self-report questionnaire evaluating functional priorities after hip or knee arthroplasty and evaluate patients' understanding of its items and conceptual relevance. METHODS: A self-report questionnaire was first developed based on the International Classification of Functioning, Disability, and Health (ICF) core set for osteoarthritis (OA). In the second stage, two research physiotherapists thoroughly reviewed and refined the questionnaire, and another physiotherapist conducted cognitive think-aloud interviews with 18 patients to assess the face and content validity of the questionnaire. RESULTS: All categories and corresponding activities of ICF core set for OA were used to develop the questionnaire. Several questionnaire issues were identified and addressed. Most challenges were related to comprehension, followed by item ordering and visual elements. Patients identified ambiguous wording which we subsequently simplified. Ten activities of the core set were excluded due to lack of face validity, two activities were added, and four activities were modified. CONCLUSION: The findings suggest that the ICF core set for OA needs to be adjusted for patients undergoing hip or knee arthroplasty and highlight the feasibility of applying a modified core set to assess functional priorities after hip or knee arthroplasty.

The questionnaire developed in this study can be used to assess patients' functional priorities after hip or knee arthroplasty for osteoarthritis.Several activities that comprise the International Classification of Functioning, Disability and Health (ICF) core set for osteoarthritis could be used to assess functional priorities after hip or knee arthroplasty.Some categories need to be removed or modified within this core set based on feedback from patients during the think-aloud sessions in our study.Using our questionnaire to determine postoperative patient priorities can help identify appropriate patient-centered outcome measures to use after hip or knee arthroplasty.

Functional patient-reported outcome measures after hip or knee arthroplasty: A systematic review and content analysis using the International Classification of Functioning, Disability and Health (ICF).

OBJECTIVE: This systematic review aimed to identify the existing patient-reported outcome measures (PROMs) used in hip or knee arthroplasty for adults with osteoarthritis and assess their content validity using the modified International Classification of Functioning, Disability and Health (ICF) core set for osteoarthritis (OA). METHOD: Four databases were systematically searched to identify disease or joint-specific PROMs evaluating function after hip or knee arthroplasty. Two reviewers independently evaluated the content of PROMs based on established ICF linking rules. RESULTS: From 449 studies included in this review, 50 PROMs were identified. The mobility chapter of activities and participation was the most common component, followed by sensory function and pain chapter of body function and structure. The most frequent ICF activity and participation categories were d451:going up and down stairs, d4701:using private motorized transportation, d4104:standing, and d4154:maintaining a standing position. However, 11 ICF categories of the modified OA coreset were not captured in any PROMs. This ICF-based content analysis of PROMs revealed that included activity and participation categories vary widely, with little overlap between PROMs. The Knee injury and Osteoarthritis Outcome Score and Hip disability and Osteoarthritis Outcome Score had the most coverage for activity and participation (36.7%). CONCLUSION: Even though our search identified 50 specific PROMs, there remain gaps in content related to activity and participation coverage. By providing a content analysis of the PROMs used after hip or knee arthroplasty, this study may help clinicians select PROMs based on covered categories and relevant clinical objectives.

How to Best Identify Acetabular Retroversion on Radiographs: Thresholds to Guide Clinical Practice.

BACKGROUND: Acetabular retroversion is associated with impingement and instability. An adequate interpretation of acetabular version and coverage on radiographs is essential to determine the optimal treatment strategy (periacetabular osteotomy vs hip arthroscopic surgery). The crossover sign (COS) has been associated with the presence of acetabular retroversion, and the anterior wall index (AWI) and posterior wall index (PWI) assess anteroposterior acetabular coverage. However, the radiographic appearance of the acetabulum is sensitive to anterior inferior iliac spine (AIIS) morphology and pelvic tilt (PT), which differs between the supine and standing positions. PURPOSE: To (1) identify differences in the acetabular appearance between the supine and standing positions among patients presenting with hip pain; (2) determine factors (acetabular version, AIIS morphology, and spinopelvic characteristics) associated with the crossover ratio (COR), AWI, and PWI; and (3) define relevant clinical thresholds to guide management. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Patients who presented to a hip preservation surgical unit (n = 134) were included (mean age, 35 ± 8 years; 58% female; mean body mass index, 27 ± 6). All participants underwent supine and standing anteroposterior pelvic radiography to assess the COS, COR, AWI, and PWI as well as standing lateral radiography to determine standing PT. Computed tomography was used to measure supine PT, acetabular version, and AIIS morphology. Acetabular version was measured at 3 transverse levels, corresponding to the 1-, 2-, and 3-o'clock positions. The correlation between radiographic characteristics (COR, AWI, and PWI) and acetabular version, AIIS morphology, and PT was calculated using the Spearman correlation coefficient. Receiver operating characteristic curve analysis was performed to define thresholds for the COR, AWI, and PWI to identify retroversion (version thresholds: <10°, <5°, and <0°). RESULTS: The COS was present in 55% of hips when supine and 30% when standing, with a mean difference in the COR of 12%. The supine COR (rho = -0.661) and AWI/PWI ratio (rho = -0.618) strongly correlated with acetabular version. The COS was more prevalent among patients with type 2 AIIS morphology (71%) than among those with type 1 AIIS morphology (43%) (P = .003). COR thresholds of 23% and 28% were able to identify acetabular version <5° (sensitivity = 81%; specificity = 80%) and <0° (sensitivity = 88%; specificity = 85%), respectively. An AWI/PWI ratio >0.6 was able to reliably identify acetabular version <0° (sensitivity = 83%; specificity = 84%). In the presence of a COR >30% and an AWI/PWI ratio >0.6, the specificity to detect retroversion was significantly increased (>90%). CONCLUSIONS: The presence of the COS was very common among patients with hip pain. False-positive results (high COR/normal version) may occur because of AIIS morphology/low PT. Relevant thresholds of COR >30% and AWI/PWI ratio >0.6 can help with diagnostic accuracy. In cases in which either the COR or AWI/PWI ratio is high, axial cross-sectional imaging can further help to avoid false-positive results.

Determining Appropriateness of Total Joint Arthroplasty for Hip and Knee Osteoarthritis: A Patient-Centred Conceptual Model.

INTRODUCTION: Total joint arthroplasty (TJA) for osteoarthritis is one of several treatment options with benefits and harms that patients value differently. However, the process for determining TJA appropriateness does not sufficiently acknowledge patient perspectives. The aim of this paper is to propose an evidence-informed patient-centred conceptual model for elective TJA appropriateness for hip and knee osteoarthritis. METHODS: Our interprofessional team developed a conceptual model for determining the appropriateness of adults considering elective TJA. The model was informed by a review of the evidence, a qualitative study we conducted with adults who underwent TJA for osteoarthritis to determine barriers and facilitators to the use of appropriateness criteria, and the research and clinical experience of team members. RESULTS: Appropriateness is providing health services (e.g., TJA) with net benefits to the right patient at the right time. The proposed Patient-centred Elective TJA Appropriateness Conceptual Model involves three key steps. First, assess adults with osteoarthritis to determine eligibility for TJA. Second, acknowledge the patient's informed preferences including their expectations and goals. Third, explore and support their mental and physical readiness for TJA. Given that osteoarthritis is a chronic condition, these steps can be revisited over time with patients. DISCUSSION AND CONCLUSION: Our proposed conceptual model reconceptualises the appropriateness of TJA to be more patient-centred. Hence, this approach has the potential to be a more inclusive approach and ensure patients undergoing TJA are eligible, ready to proceed, and achieve what matters most to them. Future research is needed to test and validate the model.

The relationship of pain catastrophizing with postoperative patient-reported outcome measures in adults with pre-arthritic hip disease.

The association between preoperative pain catastrophizing and postoperative patient-reported outcome measures of patients with pre-arthritic hip disease was evaluated. All patients scheduled for joint-preserving surgeries of the hip (JPSH) at our institution were approached. Patient demographics (age, sex, body mass index (BMI)), pain intensity (Numeric Pain Scale (NPS)) and pain catastrophizing (Pain Catastrophizing Scale (PCS)) were collected preoperatively. Patient function (12-Item International Hip Outcome Tool (iHot-12)) and physical and mental health (Patient-Reported Outcomes Measurement Information System (PROMIS-10) mental/physical) were collected preoperatively, three-month and one-year postoperatively. The analysis consisted of multivariate linear regression models fitted for continuous scores of outcome measures at three-month and one-year. Correlation between preoperative PCS and iHot-12 was assessed using the Pearson correlation coefficient. A total of 274 patients completed the PCS and were included in the multivariate linear regression models. Most patients were females (66.8%), mean age was 33 (SD 9), mean BMI was 26.5 (SD 5.8) and most were diagnosed with femoro-acetabular impingement (46.0%) and underwent arthroscopy (77.0%). There were statistically significant correlations between PCS and iHot-12 (preoperatively -0.615, P < 0.001; three-month -0.242, P = 0.002). Statistically significant associations were found for function (three-month PCS P = 0.046, age P = 0.014, NPS P = 0.043; one-year BMI P = 0.005, NPS P = 0.014), physical health (three-month BMI, P = 0.002, NPS P = 0.008; one-year BMI P = 0.002, NPS P = 0.013) and mental health (three-month BMI P = 0.047; one-year BMI P = 0.030). There is an association between function and preoperative pain catastrophizing in patients with pre-arthritic hip disease undergoing JPSH. When considering confounding variables, preoperative pain catastrophizing is associated with short-term recovery.

Factors influencing delays and overtime during surgery: a descriptive analytics for high volume arthroplasty procedures.

The aim of this article is to analyze factors influencing delays and overtime during surgery. We utilized descriptive analytics and divided the factors into three levels. In level one, we analyzed each surgical metrics individually and how it may influence the Surgical Success Rate (SSR) of each operating day. In level two, we compared up to three metrics at once, and in level three, we analyzed four metrics to identify more complex patterns in data including correlations. Within each level, factors were categorized as patient, surgical team, and time specific. Retrospective data on 788 high volume arthroplasty procedures was compiled and analyzed from the 4-joint arthroplasty operating room at our institution. Results demonstrated that surgical team performance had the highest impact on SSR whereas patient metrics had the least influence on SSR. Additionally, beginning the surgical day on time has a prominent effect on the SSR. Finally, the experience of the surgeon had almost no impact on the SSR. In conclusion, we gathered a list of insights that can help influence the re-allocation of resources in daily clinical practice to offset inefficiencies in arthroplasty surgeries.

Does pelvic tilt change with a peri-acetabular osteotomy?

Change in pelvic tilt (PT) during and after peri-acetabular osteotomy (PAO) is important for surgical planning. The aims of this study were to (i) determine how PT varies throughout the course of treatment in patients undergoing PAO, (ii) test what factors influence the change in PT and (iii) assess whether changes in PT influenced achieved correction. This is an retrospective, single-centre, consecutive case series of 111 patients treated with PAO for global (n = 79), posterior (n = 49) or anterior dysplasia (n = 6) (mean age: 27.3 ± 7.7 years; 85% females). PT was determined on supine, anteroposterior pelvic radiographs pre-, intra-, 1 day, 6 weeks and 1 year post-operatively, using the sacro-femoral-pubic (SFP) angle, a validated, surrogate marker of PT. An optimal acetabular correction was based on the lateral centre-edge angle (25°-40°), acetabular index (-5° to 10°) and cross-over ratio (<20%). There was a significant difference across pre- (70.1° ± 4.8°), 1-day (71.7° ± 4.3°; P < 0.001) and early post-operative SFP (70.6° ± 4.7°; P = 0.004). The difference in SPF between pre-operative and 1-year post-operative was -0.5° ± 3.1° (P = 0.043), with 9% of cases having a difference of >5°. The difference in SFP did not correlate with age, sex, body mass index, type of dysplasia or achievement of optimal acetabular correction (P = 0.1-0.9). In the early post-operative period, PT is reduced, leading to a relative appearance of acetabular retroversion, which gradually corrects and is restored by annual follow-up. The degree of change in PT during PAO did not adversely affect fragment orientation. PT does not significantly change in most patients undergoing PAO and therefore does not appear to be a compensatory mechanism.