Abstract
PurposeAlteration of the postoperative frontal mechanical leg axis is a known problem in femoral rotational osteotomies. However, the maintenance of the sagittal mechanical leg axis seems also important. Goal of this study was to investigate the impact of femoral rotational osteotomies on the sagittal mechanical leg axis and to identify the degree of mal-angulation of the osteotomy planes that alter the postoperative sagittal alignment relevantly.MethodsUsing 3D bone models of two patients with a pathologic femoral torsion (42° antetorsion and 6° retrotorsion), subtrochanteric and supracondylar rotational osteotomies were simulated first with an osteotomy plane perpendicular to the mechanical femoral axis (baseline osteotomy plane), second with predefined mal-angulated osteotomy planes. Subsequently, five different degrees of rotation were applied and the postoperative deviations of the sagittal mechanical leg axes were analyzed.ResultsUsing the baseline osteotomy plane, the sagittal mechanical leg axis changed by 0.4° ± 0.5° over both models. Using the mal-angulated osteotomy planes, maximum deviation of the sagittal mechanical leg axis of 4.0° ± 1.2° and 11.0° ± 2.0° was observed for subtrochanteric and for supracondylar procedures, respectively. Relevant changes of more than 2° were already observed with mal-angulation of 10° in the frontal plane and 15° of rotation in supracondylar procedures.ConclusionRelevant changes of the postoperative sagittal mechanical leg axis could be observed with just slight mal-angulation of the osteotomy planes, in particular in supracondylar procedures and in cases with higher degrees of rotation. However, osteotomies perpendicular to the femoral mechanical axis showed no relevant alterations.
Highlights
Subtrochanteric or supracondylar femoral rotational osteotomies are established surgical treatment options in symptomatic patients with pathological increased femoral antetorsion or retrotorsion [1, 2]
This seems important, as changes of the sagittal femoral bowing are known to affect later surgical procedures such as total knee arthroplasty (TKA) [7, 8] or intramedullary nailing in proximal femoral fractures [9, 10]
The axes of the standardized coordinate system were oriented in accordance to the International Society of Biomechanics (ISB) recommendation on definitions of joint coordinate systems [14] and the z-axes of the respective coordinate systems were further oriented in accordance to [4] (Fig. 2)
Summary
Subtrochanteric or supracondylar femoral rotational osteotomies are established surgical treatment options in symptomatic patients with pathological increased femoral antetorsion or retrotorsion [1, 2]. Lee et al [6] showed in a computer model an extension of the femur in the sagittal plane by performing an intertrochanteric femoral rotational osteotomy with the osteotomy plane perpendicular to the anatomical axis of the proximal femur This seems important, as changes of the sagittal femoral bowing are known to affect later surgical procedures such as total knee arthroplasty (TKA) [7, 8] or intramedullary nailing in proximal femoral fractures [9, 10]. That reconstructive procedures should not be performed by accepting secondary problems and hamper later required surgical procedures in life It was the objective of this study to investigate postoperative sagittal mechanical leg axis deviations in subtrochanteric and supracondylar femoral rotational osteotomies. The hypothesis is, that in femoral rotational osteotomies, an osteotomy perpendicular to the femoral mechanical axis should not alter the postoperative sagittal mechanical leg axis relevantly, but a mal-angulation of the osteotomy plane can result in relevant sagittal mechanical leg axis deviations
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