ePoster #1101 - ISHA Annual Scientific Meeting 2016

Identifying Parameters for the Optimal Acetabular Reduction of the Periacetabular Osteotomy for Acetabular Dysplasia: Evaluation via Postoperative Low-Dose Ct

Jeffrey J. Nepple, MD, St. Louis, MO UNITED STATES
James R. Ross, MD, Deerfield Beach, FL UNITED STATES
Asheesh Bedi, MD, Ann Arbor, MI UNITED STATES
John Clohisy, MD, St. Louis, MO UNITED STATES

Washington University School of Medicine, St. Louis, MO, UNITED STATES

FDA Status Cleared

Summary: PAO successfully normalized acetabular coverage with perfect or excellent results in 70% of our study patients.

Abstract:
Background: The periacetabular osteotomy (PAO) has become a well-accepted treatment of acetabular dysplasia, yet the radiographic criteria for optimal acetabular reduction are not known. While lateral coverage is simply assessed by measurement of the lateral center edge angle and Tonnis angle on an AP pelvic radiograph, optimal versional reduction is commonly based on the presence/absence of a crossover sign and posterior wall sign. The purpose of the current study was to (1) demonstrate whether PAO can normalize acetabular coverage and (2) determine if the crossover sign and posterior wall sign are predictive of the quality of acetabular reduction. Methods: Using our hip preservation database, we identified patients that underwent low dose pelvic CT scan as part of the preoperative planning for PAO who had previously undergone PAO of their contralateral hip. The study cohort was comprised of ten hips (7 females and 3 males). Preoperative plain radiographs were analyzed. Three-dimensional CT was analyzed including radiographic simulations and quantification of acetabular coverage relative to established normative data (+ 1 SD) from 9:00 (posterior) to 3:00 (anterior). Acetabular reduction was graded as perfect (normal anterior, lateral, and superior coverage), excellent (normal coverage in 2 regions; near normal coverage in 3rd), good (normal lateral coverage; with version malreduction resulting in mild overcoverage in one region and compensatory undercoverage in another region), or poor (all other reductions). Results: On preoperative radiographs, six patients had mild-moderate acetabular dysplasia (LCEA -5 to 20), while 4 had borderline acetabular dysplasia (LCEA 20-25). PAO was able normalize acetabular coverage with perfect or excellent reduction in 70% of cases. The mean postoperative LCEA was 28.5 degrees. Good reduction was present in the remaining 30% of cases, including 2 hips with excessive acetabular anteversion and 1 hip with excessive retroversion. Persistent anterior undercoverage remained in 3 hips, while overcoverage occurred in 2 hips. Posterior overcoverage occurred in 3 hips and undercoverage in 1 hip. Crossover signs were present in 3 hips (30%), including 3/7 hips with excellent reduction and 0/3 hips with good reduction. A positive posterior wall sign was present in 4 hips, (40%), including 3/7 hips with excellent reduction and 1/3 hips with good reduction. Conclusions: PAO successfully normalized acetabular coverage with perfect or excellent results in 70% of our study patients. The use of the crossover sign and posterior wall sign to guide version acetabular reduction appears inaccurate.