Comparison of acetabular anterior coverage after Salter osteotomy and Pemberton acetabuloplasty: a long-term followup.

BACKGROUND: The Salter osteotomy and Pemberton acetabuloplasty are common procedures for a deficient acetabulum in patients with developmental dysplasia of the hip. However, the degree of increasing retroversion and anterior acetabular coverage of these two procedures remains unanswered.

QUESTIONS/PURPOSES: The purpose of this study is to show the change in anterior coverage and relevant parameters in measuring pain and function among patients who have undergone either a Salter osteotomy or Pemberton acetabuloplasty.

METHODS: Forty-two patients who underwent either a Salter or Pemberton procedure at one institution between January 1981 and December 2000 and were available for followup at least 10 years later (mean, 18 years; range, 12-28 years) were evaluated retrospectively. This represented 12% of the Salter and Pemberton procedures performed in patients between 12 and 36 months old at our institution during the study period. We measured vertical-center-anterior margin angle, anterior acetabular head index, and weightbearing zone acetabular index, and we made comparisons using the radiographic parameter ratio (the division of each radiographic measurement of the operative side by that of the nonoperated side). All patients completed SF-36 and Harris hip score questionnaires at followup.

RESULTS: In the Salter group, there were no differences in vertical-center-anterior margin angle, anterior acetabular head index, or weightbearing zone acetabular index. In the Pemberton group, there was no difference in vertical-center-anterior margin angle or anterior acetabular head index, but the weightbearing zone acetabular index decreased, suggesting increased anterior acetabular coverage (surgically treated side, 6 [95% CI, 4.84, 7.16]; nonoperated side, 12 [95% CI, 10.07, 13.39]; p < 0.001). Compared with that in the Salter group, the weightbearing zone acetabular index ratio was smaller in the Pemberton group, which means more acquired anterior coverage after a Pemberton acetabuloplasty (Salter procedure, 0.94 [95% CI, 0.70, 1.17], Pemberton procedure, 0.53 [95% CI, 0.40, 0.65]; p < 0.001). Three patients in the Pemberton group had an anterior impingement sign at followup, whereas none in the Salter group did. The SF-36 and Harris hip scores were good and showed no differences between the two groups.

CONCLUSIONS: Our study suggests the weightbearing zone acetabular index on false profile radiographs of the hip, a parameter focusing on morphologic features of the anterior acetabulum, decreased after Pemberton acetabuloplasty compared with the nonoperated side and after the Salter acetabuloplasty. This suggests that by modifying the shape of the acetabulum with a hinge in the triradiate cartilage, a Pemberton acetabuloplasty may result in increasing acetabular anterior coverage and the risk of hip impingement. However, the functional results with at least 10 years followup were good and similar for both procedures.

LEVEL OF EVIDENCE: Level III, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.