Subtrochanteric osteotomy in the management of femoral maltorsion results in anteroposterior malcorrection of the greater trochanter: computed simulations of 3D surface models of 100 cadavers.

Abstract

The purpose of this study was to investigate the greater trochanter's (GT) behaviour in simulated subtrochanteric osteotomy. Measurement of functional and anatomical femoral torsion, and position of the GT and lesser trochanter was performed using 3-dimensional (3D) surface models of 100 cadaveric femora. Femoral torsion between 2° and 22° was defined as normal, femora with <2° and >22° of femoral torsion were assigned to the low- and high-torsion group. Subtrochanteric osteotomy was simulated to normalise torsional deformities to 12°. With subtrochanteric osteotomy, functional torsion was simultaneously corrected while adjusting anatomical torsion (<i>R</i>² = 0.866, <i>p</i> < 0.001). Compared to the normal-torsion group, an anteroposterior (AP) overcorrection of ±0.5 centimetres (range 0.02-1.1 cm) of the GT resulted in the high- and low-torsion group, respectively (<i>p</i> < 0.001): Mean AP GT distance to a standardised coronal plane was 2.1 ± 0.3 cm (range 12-30 cm) in the normal-torsion group compared to 1.61 ± 0.1 cm (range 1.4-1.71 cm) and 2.6 ± 0.6 cm (range 1.8-3.6 cm) for the corrected high and low-torsion groups, respectively. The extent of the GT shift in AP direction correlated strongly with the extent to which anatomical femoral torsion was corrected (<i>R</i>² = 0.946; <i>p</i> < 0.001). Subtrochanteric osteotomy for femoral maltorsion reliably adjusts anatomical and functional torsion, but also results in a ±1 cm AP shift of the GT per 10° of torsional correction. However, this effect of the procedure is most likely not clinically relevant in relation to hip abductor performance.