Modified triple innominate osteotomy for acetabular dysplasia: for better femoral head medialization and coverage.

UNLABELLED: Steel's triple innominate osteotomy was created for correcting dysplastic acetabulum in adolescents and young adults. We modified Steel's triple innominate osteotomy with two anterior incisions and ramus cuts close to the acetabulum to improve the mobility of the fragment for better coverage of the hip. The purpose of this study was to compare these two techniques with respect to acetabular morphology, femoral head coverage, and medialization. From 1989 to 2007, 22 hips from 19 adolescents and young adults underwent triple innominate osteotomy for symptomatic acetabular dysplasia with Tonnis grades 1 or 2. We divided patients into group A (11 hips from 10 patients), comprising patients who underwent classical Steel's osteotomy, and group B (11 hips from nine patients), comprising patients who underwent modified Steel's osteotomy, with a minimum follow-up of 2 years. Preoperative and postoperative radiographs of pelvis in the standing position were available for comparison. We used Sharp's angle, center-edge angle, femoral head extrusion index, and center-head distance discrepancy to evaluate hip morphology, femoral head coverage, and medialization, respectively. The paired t-test was used for statistical calculation with P-value less than 0.05 considered significant. The postoperative Sharp's angle, center-edge angle, femoral head extrusion index, and center-head distance discrepancy all had better results in group B with statistical significance. Other variants such as age, sex, and operation side did not have any significance. No postoperative complication was encountered. Our modified technique provided a better mobility of the rotated fragment in correcting acetabular dysplasia with a short learning curve. Most importantly, we provided greater coverage and medialization of the femoral head for better long-term results.

LEVEL OF EVIDENCE: level III, retrospective comparative study.