Open Reduction of Hip Dislocation Is Associated with Higher Rates of Proximal Femoral Growth Disturbance in Patients with Arthrogryposis Multiplex Congenita Than Idiopathic DDH

Background: The sequelae of open reduction of developmental and/or syndromic hip dislocations include osteonecrosis/proximal femoral growth disturbance and residual dysplasia. There is limited information comparing the rates of these sequelae in patients with developmental dysplasia of the hip (DDH) and arthrogryposis multiplex congenita (AMC). We performed a dual-center retrospective cohort study to compare rates of proximal femoral growth disturbance and residual dysplasia between patients with DDH and AMC who had undergone open hip reduction for the treatment of non-traumatic hip dislocations. Methods: We identified patients <18 years of age who had undergone open reduction for the treatment of hip dislocation between 1981 and 2020 at 2 tertiary pediatric hospitals. Patients with AMC were matched by age against patients with DDH in a 1:2 ratio. Preoperative data included demographic characteristics, the severity of dislocation according to the International Hip Dysplasia Institute (IHDI) classification system, and the acetabular index. Outcomes included the acetabular index at 2 years postoperatively, the IHDI classification at the time of final follow-up, and the presence and grade of proximal femoral growth disturbance according to the Salter criteria at 2 years postoperatively and according to the Kalamchi and MacEwen (KM) classification system at the time of final follow-up. Results: Eighty-two patients (98 hips) with DDH were matched against 39 patients (49 hips) with AMC. The mean follow-up was 107 months (range, 24 to 443 months). There was no difference in the mean age at surgery (1.5 ± 0.7 versus 1.4 ± 1.3 years; p = 0.86), preoperative IHDI classification, acetabular index, or spica cast duration (p > 0.05 for all), but the DDH cohort had more females (83% versus 56%; p = 0.003). Postoperatively, the prevalence of proximal femoral growth disturbance was higher in the AMC group than in the DDH group according to the Salter criteria at 2 years (57% versus 21%; p < 0.001) and according to the KM criteria at the time of final follow-up (59% versus 16%; p < 0.001). At 2 years postoperatively, there was no difference between the DDH and AMC groups in terms of the acetabular index (31° ± 6.2° versus 29° ± 6.9°; p = 0.3) or reoperation rate (24% versus 20%; p = 0.68), but the AMC cohort had more IHDI grade II-IV hips than the DDH cohort (24% versus 9%; p = 0.02), reflecting re-subluxation/dislocation. Conclusions: Open reduction for hip dislocation in patients with AMC was associated with a significantly higher rate of proximal femoral growth disturbance and re-subluxation/dislocation compared with that in patients with DDH, despite similar preoperative characteristics. This information may guide perioperative counseling for families of patients with AMC. Level of Evidence: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.