Background: Orientation of the acetabular component with the transverse acetabular ligament (TAL) to provide optimal anteversion has been reported to reduce dislocation rates. The usefulness of TAL as a landmark is controversial because there are large variations in TAL orientation. We examined anteversion of TAL preoperatively to improve its usefulness.
Methods: Three-dimensional computed tomography (3DCT) and successive roentgenography were used to analyze 42 hips that suffered idiopathic necrosis of the femoral head.
Findings: The mean operative TAL anteversion in the supine position was 14.9° ± 8.4° (range -6.5 to 30.5). There are large individual variations of TAL orientation in supine position. When the acetabular component was placed in accordance with the operative anteversion of the TAL angle in the supine position and at 40° inclination, the radiographic acetabular component anteversion was 11.3° ± 6.5° (range -5.0° to 22.9°). Six of 42 (14.3%) acetabular component was outside the safe zones of Lewinnek. The mean operative TAL anteversion in the standing position was 18.0° ± 10.8° (range-15.8 to 35.8). There was statistical difference between operative TAL anteversion in the supine and standing positions. In addition, the individual variations of TAL orientation were greater in standing position.
Conclusions: When acetabular component was placed in accordance with the operative anteversion of the TAL, more than 10% of component was outside the safe zone. Although anteversion of TAL have substantial variation, preoperative evaluation of TAL using 3D-CT increases the intraoperative reference and the accuracy of determining acetabular component orientation.
Setoguchi T, Yahiro Y2, Ishidou Y, Nagano S, Kakoi H and Komiya S