Femoral nerve palsy in brace treatment for developmental dysplasia of the hip: incidence and outcomes in a prospective international cohort

Aims: Femoral nerve palsy is a potential complication of brace treatment for children with developmental dysplasia of the hip (DDH). Little is known about its causes, and previous studies have been limited by their small sample size, retrospective design, and/or being single-centre series. The aim of this study was to examine the risk factors for femoral nerve palsy in the largest prospective cohort of children to date with DDH treated using an orthosis. Methods: A global multicentre prospective database of children with DDH was analyzed. Those treated primarily using an orthosis were included. Mixed-effects logistic regression was used to identify risk factors for the development of femoral nerve palsy, including sex, age at the time of diagnosis and application of an orthosis, the type of orthosis, the location of the femoral head, femoral head cover, and α angle. Both univariate and multivariate analyses were conducted. Results: The study included 3,008 children (5,012 affected hips) who were enrolled from 21 centres in seven countries; 99 hips (2.0%) in 94 children (3.1%) developed a femoral nerve palsy, which occurred at a median of seven days (IQR 6 to 21) after the application of a brace. A significantly increased proportion of children who developed a femoral nerve palsy were treated in a Pavlik harness compared with those who did not develop a femoral nerve palsy (84.0% (n = 79) vs 61.9% (n = 1,804); p < 0.001). Univariate analyses identified a lower percent cover of the femoral head (odds ratio (OR) 0.87 (95% CI 0.84 to 0.91); p < 0.001) and lower α angle (OR 0.82 (95% CI 0.76 to 0.89); p < 0.001) to be significantly associated with the development of femoral nerve palsy. These risk factors remained significant in the multivariate model. Conclusion: This is the largest multinational study to date evaluating the incidence and risk factors for the development of a femoral nerve palsy in these children. The incidence of femoral nerve palsy was 3.1%. The severity of DDH was identified as a significant risk factor for its development. The use of a Pavlik harness was significantly associated with the development of a femoral nerve palsy. Understanding the factors which influence its development will be important to optimize outcomes of treatment in children with DDH.