Femoral Varus Derotation Osteotomy for the Treatment of Habitual Subluxation and Dislocation of the Pediatric Hip in Trisomy 21: A 10-Year Experience

Background: Habitual hip subluxation and dislocation are potentially disabling features of the trisomy 21 syndrome. We describe outcomes after a femoral varus derotation osteotomy to achieve and maintain hip stability and community ambulation. Methods: All individuals with trisomy 21, who underwent hip surgery at our institution between 1998 and 2008, were searched using the hospital databases. The clinical notes and radiographs were reviewed from presentation to final follow-up. Nine children (16 hips) aged below 10 years, were identified. All had a femoral varus derotation osteotomy with a target femoral neck-shaft angle (NSA) of 105 degrees and external rotation of < 20 degrees of the distal fragment. All were performed by the senior author. Results: Mean age at first known hip dislocation was 4.6 years (range, 4 to 5.2 y), mean age at surgery was 6.1 years (range, 5.2 to 7.0 y), and mean follow-up was 5.4 years (range, 3.8 to 7.1 y). Mean NSA fell postoperatively to 106.0 degrees (range, 103.1 to 110.2 degrees) from 166.7 degrees (range, 162.2 to 171.1 degrees). In 2 hips, intraoperative instability remained, requiring immediate periacetabular osteotomy and capsulorraphy. Post-operatively, all patients demonstrated an asymptomatic waddling gait, which persisted in 1 individual. Fourteen hips developed peritrochanteric varus deformities with a mean center of rotation and angulation of 21 degrees (range, 16 to 25 degrees). Two hips (12.5%) sustained implant-related fractures 4 and 8 years postoperatively. One hip (6.3%) developed arthritis and none had redislocated at latest follow-up. Conclusions: Sequelae from recurrent subluxation or dislocation of hips in trisomy 21 may require surgery to prevent eventual disability. We recommend a varus producing proximal femoral osteotomy correcting the NSA to approximately 105 degrees. This should be performed before the age of 7 years or a widened or V-shape teardrop develops. After 2 implant-related fractures, we recommend implant removal once the osteotomy has healed and the hip stabilized. In our experience, this approach is effective in maintaining hip stability. Level of Evidence: A level 4 study, looking at a specific patient population undergoing a particular procedure.