The most challenging aspect in rotational deformity correction is translating the pre-operative plan to an accurate intra-operative correction. Landmarks away from the osteotomy site are typically employed at pre-operative planning and this can render inadequate correction. Our proposed technique of pre-operative planning using CT scan and leg length radiographs can translate to accurate intra-operative correction. A circle was superimposed at osteotomy site with its centre serving as the centre of correction of rotation. Medio-lateral distance at osteotomy site measured and used as diameter of the circle. Circumference of the circle was calculated by multiplying diameter with Pi and used in the below formula to obtain accurate de-rotation distance; Derotation distance = (Circumference/360) × correction value for desired ante-version The exact site of osteotomy was measured in theatre under C-arm and exposed. Derotation distance was marked on the surface of bone as point A and point B with a flexible ruler. Osteotomy performed with saw and derotation was done till point A and point B were co-linear. Derotation distance obtained using this technique is specific for the site of chosen osteotomy and implies a specific degree of correction for every millimeter derotated. Distal femur was the chosen site of osteotomy if there was associated patellar instability and proximal femur if there was no patellar instabilityIntroduction
Materials and Methods
