Leg-length discrepancy (LLD) occurs commonly in patients with osteoarthritis (OA) of the hip. Although some investigators argue that LLD in a weight-bearing position may influence lateral acetabular coverage, there have been no reports on the influence of LLD on anterior acetabular coverage and the relationship between LLD and vertical center anterior margin (VCA) angle before and after LLD correction. Anterior acetabular coverage is an important index for diagnosis, treatment, and surgery for OA of the hip. Therefore, we investigated the influence of LLD in a weight-bearing position on VCA angle.
There were 154 patients with LLD in OA of the hip and 146 healthy individuals without LLD. The sole of the short-leg side in patients was adjusted with an acrylic plate, and the LLD revision value was calculated in the anteroposterior (AP) view in a weight-bearing position. Calculated revision value was applied to individuals and VCA angles in false profile images before and after correction was measured. For healthy individuals, we corrected the sole of the nonexamined side with an acrylic plate to artificially increase LLD and then measured VCA angles in false profile images before and after correction.
Significant difference was found in VCA angles between before and after LLD correction in patients and healthy individuals (p < 0.05). Difference in VCA angles before and after LLD correction in both patients and health individuals highly correlated with LLD level in both short- and long-leg sides.
This study clarified that LLD in a weight-bearing position influenced VCA angle. Results suggested that comparison of images before and after correction increases diagnostic accuracy. Assessing anterior acetabular coverage before and after LLD correction is valuable in evaluating the need for surgery, suitable correction of osteotomized acetabular fragments in periacetabular osteotomy, and determining acetabular cup angle in artificial joint replacement.