Abstract
Medial closed wedge distal femoral osteotomy (MCWDFO) has been widely performed for lateral-compartment osteoarthritis since the development of a biplanar osteotomy technique using existing MCWDFO-specific plates. To further improve this system and the technique, we have developed a newly designed MCWDFO plate (TriS-MDFO; Olympus Terumo Biomaterials). The improved shape of the plate consists of a larger head-shaft angle to fit the distal femur after MCWDFO, more distally oriented distal screws to enable longer screw insertion, and a diamond-shaped plate head to avoid interference with the medial patellofemoral ligament. Technically, to overcome the difficulty in inserting proximal screws through the vastus medialis muscle, a cannulated screw system was employed. This system can prevent difficulties in removing the screw due to cross-threading when plate removal is required. Furthermore, we designed a novel compression hook device with a bulb-shaped head to hook on a screw hole to apply a compressive force to the osteotomized site. On the plate side, a characteristic 1.5 mm-thickness stopper is installed to prevent slippage of the hook device. This optimal compression system can minimize the risk of lateral hinge fracture during the compression procedure. These improvements in the TriS-MDFO may increase the ease and safety of MCWDFO.