IDENTIFICATION OF PREDICTORS FOR THE DEVELOPMENT OF FEMORAL NERVE PALSY IN BRACE TREATMENT FOR DEVELOPMENTAL DYSPLASIA OF THE HIP

Femoral nerve palsy (FNP) is a potential complication of brace treatment for developmental dysplasia of the hip (DDH). Little is known about the causes of this complication, and previous studies have been limited by small sample size, retrospective design and/or single-centre series The purpose of this study was to to examine potential risk factors for FNP in the largest, prospective cohort of infants with DDH to date treated by orthosis. A global multi-centre, prospective database of infants diagnosed with DDH was analyzed for patients that developed FNP during orthosis treatment. Patients treated by closed or open reduction prior to orthosis treatment were excluded. Mixed-effects logistic regression was used to identify potential risk factors for development of FNP. Risk factors analyzed included sex, age at diagnosis and orthosis application, orthosis applied, femoral head location, percent coverage of the femoral head, and alpha angle. Both univariate and multivariate analyses were conducted. In total, 3008 patients (5012 affected hips) were included; 99 (2.0%) hips in 94 patients (3.1%) developed FNP. Median (Q1, Q3) time to development of FNP was 7 (6,21) days after brace application. Pavlik was most commonly used orthosis (62.6%), followed by Denis Browne (23.9%), with the Pavlik used more frequently in those that developed FNP (84.0% vs. 61.9%; P < 0 .001). Univariate analyses (odds ratio [95% CI]) identified lower percent coverage of the femoral head (0.87 [0.84,0.91];P < 0 .001), and lower alpha angle (0.82 [0.76,0.89];P < 0 .001) to be significantly associated with a higher risk of femoral nerve palsy. These risk factors remained significant in the multivariate model, with odds ratios of 0.93 [0.88,0.99] and 0.90 [0.83,0.98] respectively. Incidence of FNP in this prospective cohort was 3.1%. Severity of dislocation/dysplasia was the most significant potential risk factor identified for development of FNP, with both decreased percent coverage of the femoral head and lower alpha angle associated. Pavlik harness use also resulted in development of FNP more frequently than Denis Browne or other orthosis use. This is the largest study to date evaluating the incidence and risk factors for FNP in a muli-national population. Understanding factors affecting development of this complication will be important to optimize treatment outcomes for patients and avoid potentially unnecessary surgical procedures.