Fig 6.

Biplane osteotomy (left knee). (A) The first K-wire for the distal oblique osteotomy is inserted 4 cm from the medial epicondyle in the direction of a tangent of the lateral condyle (yellow dashed line). The tip of the K-wire is emplaced between the lateral condyle (yellow dashed line) and the lateral cortex of the femoral shaft (yellow line). (B) A second K-wire is inserted proximally at the planned distance using a width gauge. (C) The tips of the K-wires do not meet, allowing a chisel or a saw blade to be inserted into the hinge point. (D) The osteotomy lines are drawn with an electrosurgical knife. (E) The rough cut of the ascending osteotomy, leaving the lateral cortex intact to prevent lateral hinge fracture, is performed previous to the oblique osteotomies. (F) The distal and the proximal oblique osteotomies are performed between the 2 K-wires. (G) Owing to the rough cut of the ascending osteotomy, the wedge can be easily removed (yellow arrow) when the proximal and distal oblique osteotomy lines meet together. (H) The posterior cortices are trimmed using a reciprocating saw. (I) To prevent an unstable lateral hinge fracture, it is crucial to cut the lateral portion of the ascending osteotomy line (yellow shaded area) completely. (SP, suprapatellar pouch; VM, vastus medialis muscle.)