Identifying Risk Factors for Disease Progression in Developmental Dysplasia of the Hip Using a Contralateral Hip Model.

BACKGROUND

Developmental dysplasia of the hip (DDH) can cause pain and premature osteoarthritis. The risk factors and timing for disease progression in adolescents and young adults have not been fully defined. This study aimed to determine the prevalence of and risk factors for contralateral hip pain and surgery after periacetabular osteotomy (PAO) on a dysplastic hip.

METHODS

Patients undergoing unilateral PAO for DDH were followed for at least 2 years and categorized into contralateral pain and no-pain groups and contralateral surgery and no-surgery groups. Pain was defined with the modified Harris hip score. Univariate analysis tested group differences in demographics, radiographic measures, and range of motion. Kaplan-Meier survival analysis was used to assess pain development and surgery in the contralateral hip over time. Multivariable regression identified risk factors for contralateral pain and surgery. Contralateral pain and surgery predictors were secondarily assessed after categorization of the contralateral hips as dysplastic, borderline, and non-dysplastic and in subgroups based on the lateral center-edge angle (LCEA) and acetabular inclination (AI) in 5° increments.

RESULTS

One hundred and eighty-four patients were followed for a mean of 4.6 ± 1.6 years (range, 2.0 to 8.8 years), during which 51% (93) reported contralateral hip pain and 33% (60) underwent contralateral surgery. Kaplan-Meier analysis predicted 5-year survivorship of 49% with contralateral pain development as the end point and 66% with contralateral surgery as the end point. Painful hips exhibited more severe dysplasia compared with no-pain hips (LCEA = 16.5° versus 20.3°, p < 0.001; AI = 13.2° versus 10.0°, p < 0.001). AI was the sole predictor of pain, with every 1° increase in the AI raising the risk by 11%. Surgically treated hips also had more severe dysplasia (LCEA = 14.9° versus 20.0°, p < 0.001; AI = 14.7° versus 10.2°, p < 0.001) and were in younger patients (21.6 versus 24.1 years, p = 0.022). AI and a maximum alpha angle of ≥55° were predictors of contralateral surgery.

CONCLUSIONS

At 5 years after hip PAO, approximately 50% of contralateral hips will have pain and approximately 35% can be expected to need surgery. More severe dysplasia, based on the LCEA and AI, increases the risk of contralateral hip pain and surgery, with AI being a predictor of both outcomes. Knowing these risks can inform patient counseling and treatment planning.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.