Background: It is well accepted that femoral shortening osteotomy can reduce the risk of complications after open reduction of developmental dislocation of the hip (DDH), especially in older children and "high" dislocations. It remains unclear, however, at what age a child needs a femoral shortening osteotomy and what exactly constitutes a "high" dislocation. The purpose of our study was to evaluate age and femoral displacement as predictors of the need for a femoral shortening osteotomy during the open treatment of DDH. Methods: A retrospective study was performed on all hips that underwent open treatment for DDH between 2005 and 2008. In our algorithm, femoral shortening osteotomy was performed only if it was necessary to ease femoral head reduction (independent of patient age and radiographic displacement). Preoperative anteroposterior radiographs of the pelvis were used to measure the normalized superior and lateral displacement of the proximal femoral metaphysis relative to Hilgenreiner's line and the lateral edge of the triradiate cartilage, respectively. Operative reports were reviewed to determine age at the time of surgery and whether or not a femoral shortening osteotomy was performed. Results: Our series consisted of 72 consecutive hips; mean patient age was 35.6 months (range: 16.4 to 76.0 mo). Overall, 25 of 72 hips (35%) underwent a femoral shortening osteotomy. When the proximal femur was vertically displaced greater than 30% of the pelvic width, the child was significantly more likely to need a femoral shortening osteotomy (P < 0.0001, relative risk 3.6). Children older than 36 months of age were also more likely to require a shortening compared with younger children (P = 0.001, relative risk 3.2). When both factors were present, the relative risk of needing a femoral shortening was 3.8 (P < 0.00002). Conclusions: As expected, older patients (> 36mo of age) and high dislocations (superior displacement of the proximal femur > 30% of pelvic width) were more likely to require a femoral shortening osteotomy. Our results may help frame expectations for both the family and the surgeon when anticipating surgical treatment for DDH.
