Preoperative Planning of Oblique Femoral Trochanteric Osteotomy by Geometric Analysis

Choi, In Ho; Cho, Tae Joon

Abstract

Oblique single-plane trochanteric osteotomy, in which an oblique cut is made through the femoral trochanteric area and the bony fragments are rotated at the face of the cut in direct contact with each other, allows simulatenous correction of the femoral neck-shaft angle, femoral anteversion as well as flexion/extension effect. Only approximate methods of calculating the correction effects of this procedure have been introduced. Considering unique spatial orientation of femoral neck, we developed a rigorous method to calculate preoperatively the obliquity of the single-plane osteotomy and the amount of rotation required to achieve the target femoral conformation, through geometric analysis. The correction effect by oblique trochanteric osteotomy on the geometry of proximal femur was dependent not only on the amount of change of the neck-shaft angle and femoral anteversion but also on the preoperative neck-shaft angle and femoral anteversion themselves. The flexion/extesion effect was determined by the direction of the correction and the preoperative neck orientation. Computer graphic simulation study confirmed the validity of this method. A program written in QBASIC was introduced to make this complex calculation method more useful in the clinical practice.