Deformity planning for frontal and sagittal plane corrective osteotomies.

The authors have developed a universal system of geometric deformity planning based on the mechanical or anatomic axes. The place where the axes intersect is the center of rotation angulation (CORA) of a deformity. Osteotomy level and type should be considered relative to the CORA to avoid creating secondary deformities. This type of planning is applicable to both frontal and sagittal plane deformities.