What Proportion of Patients Undergoing Bernese Periacetabular Osteotomy Experience Nonunion, and What Factors are Associated with Nonunion?

BACKGROUND: The Bernese periacetabular osteotomy (PAO) is one of the most-used surgical techniques to treat symptomatic acetabular dysplasia. Although good functional and radiographic short-term and long-term outcomes have been reported, several complications after PAO have been described. One complication that may compromise clinical results is nonunion of an osteotomy. However, the exact prevalence and risk factors associated with nonunion are poorly elucidated. QUESTIONS/PURPOSES: (1) What proportion of patients have complete bony healing versus nonunion during the first year after PAO? (2) What is the clinical and functional impact of nonunion at a minimum of 1 year after PAO, as assessed by the modified Harris hip score (mHHS) and the Hip Disability and Osteoarthritis Outcome Score (HOOS)? (3) What patient-specific or surgery-specific factors are associated with nonunion at 6 months and at a minimum of 1 year postoperatively? METHODS: Between January 2012 and December 2015, we retrospectively identified 314 patients who underwent PAO at our institution. During this period, 28 patients with a diagnosis different from symptomatic acetabular dysplasia (reverse PAO for acetabular over-coverage: n = 25; PAO for skeletal chondrodysplasia: n = 3) underwent PAO but were ineligible to participate. Hence, 286 patients underwent PAO to treat symptomatic acetabular dysplasia during the study period and were considered eligible. Inclusion criteria were patients with a complete set of postoperative radiographs (AP, Dunn lateral, and false-profile) at 12 months or more postoperatively. Eighteen percent (51 of 286) of the patients underwent staged, bilateral PAOs, but we only included the first PAO. Finally, 14% (41 of 286) of the patients were excluded because they had an incomplete set of postoperative radiographs at 12 months or more. The study comprised 245 patients. Eighty-five percent (209 of 245) of the patients were female and the mean age at surgery was 24 years ± 9 years. The healing status (complete healing vs. nonunion) was recorded for ischial, superior pubic, supraacetabular, and posterior column osteotomies at each subsequent visit. Nonunion was defined as noncontiguous osseous union with a persistent radiolucent line across any osteotomy site and was recorded at 3 months, approximately 6 months, and approximately 12 months postoperatively. Calculation of Cohen's kappa statistic coefficients showed the classification had perfect interobserver agreement (0.53; 95% confidence interval, 0.12-0.93), but there was moderate intraobserver agreement between those who healed and those with nonunion. The HOOS and mHHS were collected preoperatively and at a minimum of 1 year after PAO. The HOOS contains five separate subscales for pain, symptoms, activity of daily living, sport and recreational function, and hip-related quality of life. The HOOS responses are normalized on a scale of 0 (worst) to 100 (best). The mHHS includes pain and function scales and is overall interpreted on a scale from 0 (worst) to 100 (best). Eighty-six percent (211 of 245) of the patients with a complete set of images at their 12-month visit completed the mHHS and 89% (217 of 245) completed the HOOS. We collected information from the patients' medical records about their symptomatic status and additional treatment for nonunion. A logistic regression analysis was used to investigate factors associated with nonunion at 6 and 12 months postoperatively. RESULTS: Only 45% (96 of 215) of the patients had complete radiographic healing of all osteotomy sites at the 6-month visit and 55% (119 of 215) had not healed completely. However, 92% (225 of 245) demonstrated complete radiographic healing of all osteotomy sites at approximately 1 year postoperatively. The proportion of nonunion at a minimum of 12 months after PAO was 8% (20 of 245 patients). There was no difference in the mHHS after 1 year or more of follow-up between patients with nonunion and patients with complete healing after PAO (nonunion mean mHHS: 73; 95% CI, 62-85 versus healed: 82; 95% CI, 80-85; p = 0.13) and HOOS pain (nonunion mean HOOS pain: 80; 95% CI, 71-90 versus healed: 86; 95% CI, 83-88; p = 0.16). Similarly, no difference was identified for HOOS symptoms (nonunion mean: 72; 95% CI, 63-80 versus healed: 78; 95% CI, 75-81; p = 0.11), HOOS activities of daily living (nonunion mean: 86; 95% CI, 78-94 versus healed: 91; 95% CI, 89-93; p = 0.09), HOOS sports and recreation (nonunion mean: 70; 95% CI, 57-83 versus healed: 78; 95% CI, 75-82; p = 0.18); and HOOS quality of life (nonunion mean: 60; 95% CI, 46-75 versus healed: 69; 95% CI, 65-72; p = 0.28). After controlling for potentially confounding variables such as gender, age, chisel type, and preoperative anterior center-edge angle, we found that higher BMI (per 1 k/m; odds ratio 1.14; 95% CI, 1.06-1.22; p < 0.01), older age (per 1 year; OR 1.05; 95% CI, 1.01-1.08; p < 0.01) and more-severe acetabular dysplasia as assessed by a decreased preoperative lateral center-edge angle (per 1°; OR 1.06; 95% CI, 1.02-1.11; p < 0.01) were independently associated with nonunion of one or more osteotomy sites at 6 months postoperatively. Only age was an independent predictor of nonunion at 12 months postoperatively (per 1 year; OR 1.06; 95% CI, 1.01-1.11; p = 0.02). CONCLUSIONS: Our study helps us to understand radiographic healing during the first year after PAO to treat symptomatic acetabular dysplasia. Fewer than half of the patients had complete healing of their osteotomies at 6 months postoperatively. More than 90% of patients can expect to have completely healed osteotomy sites at 12 months postoperatively. Surgeons should avoid unnecessary interventions if nonunion is observed radiographically at 6 months postoperatively. Although there was no difference in the HOOS and mHHS between patients with nonunion and those with complete healing, further research with a larger cohort is needed to clarify the impact of nonunion on clinical and functional outcomes after PAO. Surgeons should consider using strategies to enhance osteotomy healing in those who undergo PAO, such as optimizing vitamin D levels and using local bone grafts in older patients, those with a high BMI, and patients with severe acetabular dysplasia. LEVEL OF EVIDENCE: Level III, therapeutic study.

Successful Arthroscopic Fixation of a Posterior Wall Acetabular Fracture Nonunion on a Patient With Femoroacetabular Impingement: A Case Report.

CASE: This report presents the results of a hip arthroscopic technique that was used to treat an unusual posterior wall acetabular fracture nonunion. A 30-year-old man presented with 1 year of persistent left-sided buttock and groin pain with associated feeling of instability when climbing stairs. Magnetic resonance imaging demonstrated a small left acetabular posterior wall fracture nonunion. We describe outpatient treatment with reduction and cannulated screw fixation using arthroscopic techniques that permitted immediate partial weight bearing and achieved excellent outcomes at 1 year. CONCLUSION: Arthroscopic fixation of an acetabular posterior wall fracture nonunion may be a feasible treatment option in select cases.

Reliability of and Correlation Between Measurements of Acetabular Morphology.

The authors sought to determine the intra- and interrater reliability of contemporary measures of acetabular morphology among a group of hip surgeons and to determine the correlations between measures of acetabular morphology. On 2 separate occasions, 3 hip surgeons independently performed blinded evaluations of anteroposterior pelvic radiographs of 40 patients. The lateral center-edge angle, medial center-edge angle, acetabular arc, extrusion index, acetabular index, Sharp's angle, posterior wall sign, crossover sign, femoro-epiphyseal acetabular roof index, acetabular wall indexes, and delta angle were assessed. A linear mixed model was used for variance estimation, and kappa and intra-class correlation coefficients were assessed for reliability. Pearson correlation coefficients were calculated for all possible pairs of radiographic measures. The acetabular index had the greatest interrater agreement (0.90; 95% confidence interval [CI], 0.84-0.93), whereas the lateral center-edge angle had the higher intrarater agreement (0.96; 95% CI, 0.92-0.98). The acetabular arc angle had the lowest interrater agreement (0.44; 95% CI, 0.29-0.57), and the Sharp's angle had the lowest intrarater agreement (0.66; 95% CI, 0.41-0.84). The posterior wall sign had an interrater agreement of 0.35 (95% CI, 0.11-0.54) and an intrarater agreement of 0.68 (95% CI, 0.49-0.86). The crossover sign had an interrater agreement of 0.66 (95% CI, 0.43-0.84) and an intrarater agreement of 0.85 (95% CI, 0.52-0.89). The acetabular index, lateral center-edge angle, and extrusion index presented with high coefficients of correlation. In addition, acetabular anteversion correlated with severity of dysplasia. Commonly used parameters such as the acetabular index, lateral center-edge angle, and extrusion index are reliable radiographic parameters to assess acetabular morphology. However, correlation between measures suggests that they may be redundant in quantifying acetabular morphology. [Orthopedics. 2018; 41(5):e629-e635.].