Dynamization of locked plating on distal femur fracture.

Most of the clinical studies on the results of MIPO (minimally invasive plate osteosynthesis) with the use of anatomically preshaped locking plates for the complex distal femoral fractures have shown favorable results. In the application of bridge plating, placement of lag screws to the butterfly fragments is usually not recommended because it may make the whole construct too stiff. Recently, problems of nonunion related to excessive stiffness after MIPO using a locked plate were reported but the only solution suggested was reoperation with a bone graft. We herein report a case of nonunion after MIPO of the distal femoral fracture where we applied a concept of "dynamization of the plate-bone construct" to make it less stiff and in turn to get fracture healing with bridging callus formation. A 58-year-old woman sustained a simple oblique fracture of the distal femur (AO-OTA 33A1). We performed MIPO procedure using a locking compression plate-distal femur. To get the alignment, we have placed a conventional screw across the fracture line through the dynamic compression unit (DCU) of the combination hole. Postoperative radiographs revealed 7-8 mm gap across the entire fracture surface which was not obvious on the intra-operative C-arm images. Radiographs taken 6 months after operation showed almost no callus formation with shuttle marginal resorption. We interpreted the situation that the construct was too stiff to allow motion across the fracture site due to the lag screw. We thought we have used it as a reduction screw but it acted as a lag screw, preventing motion at the fracture site. Given this analysis, we have only taken the lag screw out to make the construct less stable. It caused the situation of absolute stability with a significant gap to turn into the one of relative stability with acceptable gap. Fracture has solidly healed with bridging callus formation 6 months after lag screw removal under local anesthesia. We would like to call this strategy as "dynamization" of the locked plating.