Effect of Innominate and Femoral Varus Derotation Osteotomy on Acetabular Development in Developmental Dysplasia of the Hip

Background: Open reduction for the treatment of hip dislocation due to developmental dysplasia of the hip in children of walking age is frequently combined with either a femoral varus derotation osteotomy or an innominate osteotomy; however, it remains unclear which of these procedures is preferable in terms of subsequent hip development. The purpose of the present study was to compare acetabular development in patients managed for dislocation of the hip with open reduction combined with one of the two osteotomies. Methods: Patients between fifteen months and four years of age with hip dislocations that were treated at two different centers were compared. At one center, open reduction combined with a femoral varus derotation osteotomy was performed (thirty-eight patients), and at the other, open reduction combined with an innominate osteotomy was performed (thirty-three patients). In each group, one surgeon performed all of the operations. A total of 490 postoperative radiographs that were made over a mean follow-up period of 6.2 years were analyzed. We compared the change in acetabular index as well as several other radiographic criteria of acetabular development and hip stability over time. Results: After osteotomy, the acetabular index improved in both groups; however, the acetabular index in patients who underwent a varus derotation osteotomy never improved as much as that in patients who underwent an innominate osteotomy, with a mean difference of 9.5 after four years (p < 0.0001). Similarly, the innominate osteotomy group demonstrated better acetabular architecture and hip stability over time as quantified by the change in the acetabular floor thickness (p = 0.03), lateral centering ratio (p < 0.0001), and superior centering ratio (p < 0.0001). Conclusions: In the present series, acetabular remodeling after open hip reduction and innominate osteotomy was more effective for reversing acetabular dysplasia and maintaining hip stability than open reduction combined with a femoral varus derotation osteotomy was. Long-term follow-up is necessary to determine whether the more favorable hip development following innominate osteotomy is associated with a lower incidence of premature degenerative hip disease.