Three-dimensional computed tomography analysis and anteversion study after periacetabular osteotomy of pelvis in children

Abstract

Purpose Three-dimensional computed tomography (CT) is the method of choice in understanding the morphological changes after periacetabular osteotomy in children. We studied different parameters and compared aspects of operated hip (OH) with non-operated hip (NOH) to define the maneuver that promotes normalization of the hip during repositioning of the acetabulum. Methods A total of 22 patients with 25 OHs underwent CT control scans an average of 4 years after surgery. The patients, with a mean age of 6.8 years, had either Legg-Calvé-Perthes disease (12 cases) or dysplasia (10 cases).The measurements included the anterior and posterior coverage angles of the hip and version of the acetabulum on axial CT views. The 3D reconstructed images measured the inclination of the antero– and postero–lateral lips, the external rotation and the anterior inclination of the acetabulum. Results The mean anterior coverage angle was 27° for OHs, 31° for NOHs, and 12° versus 10.3° for the posterior coverage angle. Acetabular anteversion was 2° for OHs (6.3° in the dysplastic OHs) and 6° for NOHs. The mean angle of inclination of the antero–lateral lip was 37° for OHs, 47° for NOHs, and the postero–lateral lip inclination was 56° for OHs and 67° for NOHs. Inferior 3D views showed a mean internal acetabular rotation of 1.5° (4.8° in the dysplastic OH), 3° for NOH. The anterior acetabular inclination angle measured with lateral 3D views was 6° for OHs, 11° for NOHs. Conclusion Our analysis demonstrated a mean anteversion of the acetabulum despite normalization of the anterior coverage of the hip, particularly in the dysplastic group, in which the osteotomized fragments had anteversion superior to NOH. The unexpected external rotation used to improve anterior coverage of a coax magna in Legg-Calvé-Perthes disease was responsible for the retroversion and the decrease of the posterior coverage.