Mobility-related outcomes for periacetabular osteotomy in persons with acetabular dysplasia: setting the stage for measurement of real-world outcomes

ABSTRACT Periacetabular osteotomy (PAO) is a surgery for persons with symptomatic acetabular dysplasia (AD) that increases acetabular coverage of the femoral head for reducing hip pain and improving function. Patient-reported outcomes (PROs) are significantly improved following PAO, yet little is known regarding mobility-related outcomes. This narrative review provides a synthesis of evidence regarding PROs and mobility-related outcomes in persons with AD following PAO. We further identified important future research directions, chiefly the need for measurement of real-world outcomes. We searched PubMed using comprehensive predefined search terms. We included studies that (i) enrolled persons with AD undergoing PAO, (ii) included PROs and/or mobility-related outcomes and (iii) were written in English. We synthesized and summarized study characteristics and findings. Twenty-three studies were included in this review. Commonly evaluated PROs included pain (n = 14), hip function (n = 19) and quality of life (n = 9). Mobility-related outcomes included self-reported physical activity (PA; n = 11), walking speed and cadence (n = 4), device-measured PA (n = 2), and sit-to-stand, four-square-step and timed stair ascent tests (n = 1). Persons with AD had significant improvements in PROs following PAO, yet mobility-related outcomes (e.g. walking speed and device-measured PA levels) did not change over 1 year following PAO. Few studies have evaluated mobility-related outcomes following PAO, and these studies were of a low methodological quality. Future research might include experience sampling data collection approaches and body-worn devices as free-living, technology-driven methodologies to evaluate mobility and other outcomes in persons with AD undergoing PAO.

What is the pelvic tilt in acetabular dysplasia and does it change following peri-acetabular osteotomy?

To quantify the pelvic tilt (PT) in patients with symptomatic acetabular dysplasia and determine if it represents a compensatory mechanism to improve femoral head coverage, we studied a cohort of 16 patients undergoing 32 bilateral staged PAOs for acetabular dysplasia and compared this to a matched cohort of 32 patients undergoing PAO for unilateral acetabular dysplasia all with >1 year follow-up. The change in PT was determined with two validated methods, namely, the sacro-femoral-pubic (SFP) angle and the pubic symphysis to sacroiliac index (PS-SI). Despite an improvement in the lateral centre-edge and Tönnis angles to within normal limits following PAO, patients with unilateral and bilateral acetabular dysplasia have similar PT pre-operatively (8° ± 5°) and post-operatively (9° ± 5°). A change of >5° was observed in only six patients (13%) using the SFP angle, and five patients (10%) using the PS-SI, all increased (posterior rotation of the pelvis). No patients were observed to have a change in PT >10°. The observed PT in our study group is equivalent to that found in the normal population and in patient with symptomatic acetabular retroversion. These findings all suggest that PT is morphological rather than a result of a compensatory mechanism, and even if it was compensatory, it does not appear to reverse significantly following PAO. The target for acetabular reorientation, therefore, remains constant.

Hypermobility, age 40 years or older and BMI >30 kg m−2 increase the risk of complications following peri-acetabular osteotomy

The peri-acetabular osteotomy (PAO) is a powerful surgical procedure for correcting symptomatic acetabular dysplasia, but it carries the potential for significant surgical complications. This study aims to determine the complication profile of PAO in a series performed by an experienced single surgeon. This was as retrospective review of 223 hips in 200 patients (23 bilateral, 22 males and 201 females). Complication data were collected from notes and radiographic review and graded according to a modified Dindo–Clavien classification. Each hip could be recorded as having more than one complication. Mean age at surgery was 28.8 years (range 13-48), mean weight was 70.9 kg (range 45–115 kg). Diagnosis was dysplasia in 185 hips, retroversion in 25 and a combination in 13. Mean follow-up was 26 months. In all, 61.4% of hips (137) had no complications; 74.0% had no complications or a Grade I complication (one that did not change management); 52 hips (23%) required pharmaceutical interventions (Grade II complications). Six hips (2.7%) suffered a major complication (Grade III or IV) as a direct consequence of the PAO. There were no Grade V complications (death). Hypermobility (Beighton’s score of ≥6, Odds ratio (OR) 2.525 P = 0.041), age 40 years or older (OR 3.126 P = 0.012) and BMI >30 (OR 2.506 P = 0.031), but not Tonnis grade (P = 0.193) increased the risk of more severe complications following a PAO. This single surgeon series from a high volume centre demonstrates that age 40 years or older and BMI >30 kg m−2 and hypermobility increase the risk of more severe of complications.

Ottawa classification for symptomatic acetabular dysplasia assessment of interobserver and intraobserver reliability

Aims The aim of the current study was to assess the reliability of the Ottawa classification for symptomatic acetabular dysplasia. Methods In all, 134 consecutive hips that underwent periacetabular osteotomy were categorized using a validated software (Hip2Norm) into four categories of normal, lateral/global, anterior, or posterior. A total of 74 cases were selected for reliability analysis, and these included 44 dysplastic and 30 normal hips. A group of six blinded fellowship-trained raters, provided with the classification system, looked at these radiographs at two separate timepoints to classify the hips using standard radiological measurements. Thereafter, a consensus meeting was held where a modified flow diagram was devised, before a third reading by four raters using a separate set of 74 radiographs took place. Results Intrarater results per surgeon between Time 1 and Time 2 showed substantial to almost perfect agreement among the raters (κappa = 0.416 to 0.873). With respect to inter-rater reliability, at Time 1 and Time 2 there was substantial agreement overall between all surgeons (Time 1 κappa = 0.619; Time 2 κappa = 0.623). Posterior and anterior rating categories had moderate and fair agreement at Time 1 (posterior κappa = 0.557; anterior κappa = 0.438) and Time 2 (posterior κappa = 0.506; anterior κappa = 0.250), respectively. At Time 3, overall reliability (κappa = 0.687) and posterior and anterior reliability (posterior κappa = 0.579; anterior κappa = 0.521) improved from Time 1 and Time 2. Conclusion The Ottawa classification system provides a reliable way to identify three categories of acetabular dysplasia that are well-aligned with surgical management. The term ‘borderline dysplasia’ should no longer be used. Cite this article: Bone Joint Res. 2020;9(5):242–249.

PROMIS Versus Legacy Patient-Reported Outcome Measures in Patients Undergoing Surgical Treatment for Symptomatic Acetabular Dysplasia

Background: No previous study has investigated how the Patient-Reported Outcomes Measurement Information System (PROMIS) performs compared with legacy patient-reported outcome measures in patients with symptomatic acetabular dysplasia treated with periacetabular osteotomy (PAO). Purpose: To (1) measure the strength of correlation between the PROMIS and legacy outcome measures and (2) assess floor and ceiling effects of the PROMIS and legacy outcome measures in patients treated with PAO for symptomatic acetabular dysplasia. Study Design: Cohort study (Diagnosis); Level of evidence, 2. Methods: This study included 220 patients who underwent PAO for the treatment of symptomatic acetabular dysplasia. Outcome measures included the Hip disability and Osteoarthritis Outcome Score (HOOS) pain, HOOS activities of daily living (ADL), modified Harris Hip Score (mHHS), PROMIS pain, and PROMIS physical function subsets, with scores collected preoperatively and/or postoperatively at a minimum 12-month follow-up. The change in mean scores from preoperatively to postoperatively was calculated only in a subgroup of 57 patients with scores at both time points. Distributions of the PROMIS and legacy scores were compared to evaluate floor and ceiling effects, and Pearson correlation coefficients were calculated to evaluate agreement. Results: The mean age at the time of surgery was 27.7 years, and 83.6% were female. The mean follow-up time was 1.5 years. Preoperatively, neither the PROMIS nor the legacy measures showed significant floor or ceiling effects. Postoperatively, all legacy measures showed significant ceiling effects, with 15% of patients with a maximum HOOS pain score of 100, 29% with a HOOS ADL score of 100, and 21% with an mHHS score of 100. The PROMIS and legacy instruments showed good agreement preoperatively and postoperatively. The PROMIS pain had a moderate to strong negative correlation with the HOOS pain ( r = −0.66; P < .0001) and mHHS ( r = −0.60; P < .0001) preoperatively and the HOOS pain ( r = −0.64; P < .0001) and mHHS ( r = −0.64; P < .0001) postoperatively. The PROMIS physical function had a moderate positive correlation with the HOOS ADL ( r = 0.51; P < .0001) and mHHS ( r = 0.49; P < .0001) preoperatively and a stronger correlation postoperatively with the HOOS ADL ( r = 0.56; P < .0001) and mHHS ( r = 0.56; P < .0001). Conclusion: We found good agreement between PROMIS and legacy scores preoperatively and postoperatively. PROMIS scores were largely normally distributed, demonstrating an expanded ability to capture variability in patients with improved outcomes after treatment.

Activity Level Maintenance at Midterm Follow-up Among Active Patients Undergoing Periacetabular Osteotomy

Background: For active patients undergoing periacetabular osteotomy (PAO), returning to and maintaining a high level of activity postoperatively is a priority. Purpose: To evaluate the maintenance of activity levels at midterm follow-up in active patients treated with PAO for symptomatic acetabular dysplasia. Study Design: Case series; Level of evidence, 4. Methods: Patients who underwent PAO for symptomatic acetabular dysplasia between June 2006 and August 2013 were identified by a retrospective review of our prospective longitudinal institutional Hip Preservation Database. All patients with a preoperative University of California, Los Angeles (UCLA) score of ≥7 and a potential minimum 5 years of follow-up were included in the study. Functional outcome measures were the UCLA score, modified Harris Hip Score (mHHS), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The maintenance of high activity levels was defined as a UCLA score of ≥7 at final follow-up. Radiographic parameters were measured. Statistical significance was defined as a P value <.05. Results: A total of 66 hips (58 patients) were included. The mean age was 25.3 years (range, 14-47 years), the mean body mass index was 23.9 kg/m2 (range, 19-32 kg/m2), and 72% were female. The mean follow-up was 6.8 years (range, 5-11 years). There were 67% of patients who maintained a UCLA score of ≥7. Patient-reported outcomes improved postoperatively from preoperatively for the mHHS (88 ± 14 vs 67 ± 17, respectively; P < .001) and WOMAC (89 ± 15 vs 73 ± 20, respectively; P < .001). The lateral center-edge angle, anterior center-edge angle, and acetabular inclination were significantly improved at final follow-up ( P < .001). Only 4 patients (7%) cited postoperative activity limitations as being caused by hip pain. There were no conversions to total hip arthroplasty. Conclusion: The majority (67%) of active patients returned to preoperative or higher activity levels after PAO at midterm follow-up.

BORDERLINE ACETABULAR DYSPLASIA: INDEPENDENT PREDICTORS OF HIP INSTABILITY VERSUS IMPINGEMENT

Background: Hips with borderline acetabular dysplasia (lateral center-edge angle, LCEA, between 20° and 25°) are challenging in terms of diagnostic and treatment decision-making. It is accepted that a portion of this population has primarily hip instability-based symptoms consistent with symptomatic acetabular dysplasia, while others have primarily hip impingement-based symptoms consistent with femoroacetabular impingement (FAI). Nevertheless, the diagnostic characteristics that differentiate hip instability and FAI have not been identified. The purpose of this study was to examine a cohort of patients with minor acetabular dysplasia features in order to identify the preoperative clinical characteristics and imaging findings that differentiate patients with hip instability from patients with FAI. Methods: A retrospective cohort study of patients with borderline acetabular dysplasia was performed. Utilizing our institution’s hip preservation database, we identified 143 consecutive hips in 134 patients undergoing hip preservation surgery in the setting of borderline acetabular dysplasia. All patients were identified by prospective radiographic evaluation with an LCEA between 20° and 25°. Inclusion criteria included age 14-40 years and primary surgical treatment. Medical records were reviewed to determine patient demographics, details of clinical presentation, baseline patient-reported outcome scores, physical exam findings, plain radiographic findings, and the operative procedures performed. Statistical analyses were used to compare the clinical features and imaging parameters of the symptomatic acetabular dysplasia and FAI subgroups. Results: Of the 143 hips in the cohort, 39.2% (n = 56) had the diagnosis of symptomatic instability, while 60.8% (n = 87) had the diagnosis of FAI. The cohort included 109 females (76.2%) and 34 males (23.8%). Hips with instability (compared to FAI) had a significantly lower LCEA (21.8° vs. 22.8°; p < 0.001), lower ACEA (23.3° vs. 26.6°; p = 0.002), a higher AI (11.8° vs. 8.5°; p < 0.001), and a lower maximum alpha angle (54.4° vs. 61.1°; p = 0.001). The odds of instability increased 1.7 times for each one-degree decrease in LCEA, 1.4 times for each one-degree decrease in ACEA, and 1.1 times for each one-degree increase in acetabular inclination (all p < 0.003). Sex was strongly associated with the clinical diagnosis, with instability present in 48.6% of females compared to only 8.8% of males (p < 0.001). Patients with instability presented with significantly greater disability, as indicated by the modified Harris hip score, UCLA activity, SF-12 physical function, and HOOS (pain, activities of daily living, sports and recreation, and quality of life) scores (all p = 0.05). The symptomatic acetabular dysplasia subgroup had significantly greater range of motion in terms of internal rotation in flexion (IRF, 22.7° vs. 12.4°, p < 0.001) and total arc of rotational motion (IRF+ERF, 61.2° vs. 47.4°, p < 0.001). Lateral hip pain was present in 42.9% (24/56) of hips in the instability group compared to 25.3% (22/87) of hips in the impingement group (p = 0.03). Conclusions: We found significant differences in the clinical characteristics and radiographic features of the symptomatic acetabular dysplasia and FAI subgroups within the borderline dysplasia cohort. Patients with symptomatic instability tend to have lateral hip pain, greater functional limitations, higher range of motion, and a greater AI, while patients with impingement symptoms tend to have more limited range of motion (especially IRF), a greater ACEA, and a greater alpha angle.

Periacetabular osteotomy to treat residual dysplasia in adolescents and young adults: indications, complications, results

Purpose Discuss current indications, techniques, complications and results of periacetabular osteotomy (PAO) to treat the adolescent and young adult with symptomatic acetabular dysplasia or the rare minimally symptomatic patient with dysplasia with a guarded prognosis without PAO surgery. Methods Review of clinical experience with PAO at our and other high-volume centres. Results At a mean follow-up of 18 years after PAO, more than 75% of hips are preserved. At 30-year follow-up, longest term reported series notes survival of one-third of hips. Conclusion Both middle- and long-term results suggest efficacy of PAO in improving function and prognosis in most symptomatic adolescent and young adult patients with spherically congruous pre-arthritic dysplastic hips.