Does Salter innominate osteotomy predispose the patient to acetabular retroversion in adulthood?

BACKGROUND

Salter innominate osteotomy has been identified as an effective additional surgery for the dysplastic hip. However, because in this procedure, the distal segment of the pelvis is displaced laterally and anteriorly, it may predispose the patient to acetabular retroversion. The degree to which this may be the case, however, remains incompletely characterized.

QUESTIONS/PURPOSES: We asked, in a group of pediatric patients with acetabular dysplasia who underwent Salter osteotomy, whether the operated hip developed (1) acetabular retroversion compared with contralateral unaffected hips; (2) radiographic evidence of osteoarthritis; or (3) worse functional scores. (4) In addition, we asked whether femoral head deformity resulting from aseptic necrosis was a risk factor for acetabular retroversion.

METHODS

Between 1971 and 2001, we performed 213 Salter innominate osteotomies for unilateral pediatric dysplasia, of which 99 hips (47%) in 99 patients were available for review at a mean of 16 years after surgery (range, 12-25 years). Average patient age at surgery was 4 years (range, 2-9 years) and the average age at the most recent followup was 21 years (range, 18-29 years). Acetabular retroversion was diagnosed based on the presence of a positive crossover sign and prominence of the ischial spine sign at the final visit. The center-edge angle, acetabular angle of Sharp, and acetabular index were measured at preoperative and final visits. Contralateral unaffected hips were used as controls, and statistical comparison was made in each patient. Clinical findings, including Harris hip score (HHS) and the anterior impingement sign, were recorded at the final visit.

RESULTS

Patients were no more likely to have a positive crossover sign in the surgically treated hips (20 of 99 hips [20%]) than in the contralateral control hips (17 of 99 hips [17%]; p = 0584). In addition, the percentage of positive prominence of the ischial spine sign was not different between treated hips (22 of 99 hips [22%]) and contralateral hips (18 of 99 hips [18%]; p = 0.256). Hips that had a positive crossover or prominence of the ischial spine sign in the operated hips were likely also to have a positive crossover sign or prominence of the ischial spine sign in the unaffected hips (16 of 20 hips [80%] crossover sign, 17 of 22 hips [77%] prominence of the ischial spine sign). At the final visit, five hips (5%) showed osteoarthritic change; one of the five hips (20%) showed positive crossover and prominence of the ischial spine signs, and the remaining four hips showed negative crossover and prominence of the ischial spine signs. There was no significant difference in HHS between the crossover-positive and crossover-negative patient groups nor in the prominence of the ischial spine-positive and prominence of the ischial spine-negative patient groups (crossover sign, p = 0.68; prominence of the ischial spine sign, p = 0.54). Hips with femoral head deformity (25 of 99 hips [25%]) were more likely to have acetabular retroversion compared with hips without femoral-head deformity (crossover sign, p = 0.029, prominence of the ischial spine sign, p = 0.013).

CONCLUSIONS

Our results suggest that Salter innominate osteotomy does not consistently cause acetabular retroversion in adulthood. We propose that retroversion of the acetabulum is a result of intrinsic development of the pelvis in each patient. A longer-term followup study is needed to determine whether retroverted acetabulum after Slater innominate osteotomy is a true risk factor for early osteoarthritis. Femoral head deformity is a risk factor for subsequent acetabular retroversion.

LEVEL OF EVIDENCE

Level III, therapeutic study.