Abstract
PurposeThe purpose of this study was to assess the effect on femoral torsion by rotational osteotomies at three different levels as measured in 3D using both the mechanical and the anatomic axes.MethodsTen cadaveric lower extremities underwent femoral osteotomies perpendicular to the anatomic axis (AA) at three levels: subtrochanteric, mid-diaphyseal and supracondylar. Parallel pins were placed, one in each femur segment. Computed tomography (CT) was acquired in post-osteotomies neutral position, then post-external rotation of the femur at each osteotomy level. Femurs were returned to neutral rotation between imaging exams. Using 3D CT reconstructions, custom software calculated femoral torsion (angle between the femoral neck axis and the posterior condylar axis in the transverse plane) and pin angle between segments, reoriented to both the mechanical axis (MA) and the AA. Pin angle and torsion change were compared for the three osteotomy locations (regression analysis and ANOVA performed).ResultsTwo specimens were omitted (inadequate imaging); the remaining eight donors were 55–90 years old (mean: 64 ± 15 years), CT confirmed no bony defects. All three levels of osteotomy demonstrated significant correlations between the amount of rotation at the osteotomy (pin angle change) and the resulting change in femoral torsion (R square range 0.658–0.847). No significant differences were found between osteotomy level in torsion (MA:p = 0.285, AA:p = 0.156) or in pin angle (MA:p = 0.756, AA:p = 0.753).ConclusionsPerforming a corrective rotational osteotomy orthogonal to the AA achieves the desired effect on MA regardless of location. This suggests that a surgeon’s osteotomy level choice may be based on other risks/benefits of the various techniques.
Highlights
Derotational osteotomies to correct pathologic femoral antetorsion in children with neuromuscular disease continue to be commonplace, with a growing body of literature to support utilization in adolescent or adult patients with patellofemoral issues or extra-articular femoroacetabular impingement [1,2,3,4]
All locations of osteotomy appear to potentially affect the frontal plane with proximal osteotomies resulting in potential varus deformation and distal osteotomies resulting in potential valgus
Femoral osteotomies were performed perpendicular to the anatomic axis at all three levels: proximal, midshaft and distal
Summary
Derotational osteotomies to correct pathologic femoral antetorsion in children with neuromuscular disease continue to be commonplace, with a growing body of literature to support utilization in adolescent or adult patients with patellofemoral issues or extra-articular femoroacetabular impingement [1,2,3,4]. Pathologic femoral torsion can be treated surgically with derotational osteotomies at the subtrochanteric level (proximal), in the mid-diaphysis (midshaft), or just above the diaphyseal-metaphyseal junction (distal). The appropriate location for the osteotomies, with their various associated risks and benefits, is debated in the literature [5,6,7,8,9,10]. There is some concern that the osteotomies can affect more than just the desired rotation [7]; understanding the effect on measurable rotation is important for each of these locations. All locations of osteotomy appear to potentially affect the frontal plane with proximal osteotomies resulting in potential varus deformation and distal osteotomies resulting in potential valgus
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