Instability of the Hip in Patients with Down Syndrome

BACKGROUND: The treatment of hip instability in patients with Down syndrome is challenging, and the literature provides little data to guide treatment. The purpose of the present study was to evaluate our results with complete redirectional acetabular osteotomy and to compare these results with our experience with other procedures. METHODS: We retrospectively evaluated all patients with Down syndrome who underwent surgery for the treatment of gross hip instability or symptomatic acetabular dysplasia with or without subluxation. Medical records were reviewed for symptoms and demographic information. On the basis of the primary procedure, the patients were separated into Group A (periacetabular or triple osteotomy) or Group B (varus femoral osteotomy with or without incomplete acetabuloplasty e.g., Dega osteotomy or shelf acetabuloplasty). Preoperative and latest postoperative radiographs were used to compare the extrusion index, the lateral center-edge angle, the Tönnis angle, and the continuity of the Shenton line. Preoperative computed tomography (CT) scans were measured for acetabular version. RESULTS: We identified thirty-five hips (twenty-three patients), including twenty-five hips in Group A and ten in Group B. The mean age was 11.8 years, and the mean duration of follow-up was 5.3 years. Preoperatively, the acetabula were retroverted in both groups. Patients in Group A had worse initial hip pathology than those in Group B, as indicated by a higher mean extrusion index (50% compared with 33%; p = 0.06), a smaller center-edge angle (1° compared with 15°; p = 0.003), a larger Tönnis angle (21° compared with 10°; p = 0.001), and a smaller percentage of patients with an intact Shenton line (20% compared with 40%; p = 0.39). Most recent radiographs, however, showed superior results for Group A, including a lower mean extrusion index (10% compared with 29%; p < 0.0001), a larger center-edge angle (33° compared with 14°; p < 0.001), a smaller Tönnis angle (-1° compared with 10°; p < 0.001), and a larger percentage of patients with an intact Shenton line (88% compared with 70%; p = 0.32). Preoperatively, eighteen hips demonstrated gross instability: twelve were treated with either periacetabular osteotomy or triple innominate osteotomy, and all but one (92%) remained stable at the time of the latest follow-up. In contrast, six hips were treated with femoral osteotomy with or without incomplete acetabuloplasty, with only three (50%) remaining stable. CONCLUSIONS: Complete redirectional acetabular osteotomies are successful for stabilizing the hip and for correcting acetabular dysplasia in patients with Down syndrome.