Far Cortical Locking Enables Flexible Fixation While Maintaining Construct Strength

INTRODUCTION: The stiffness of a fixation construct affects the mechanism and progression by which a fracture heals. Locked plating constructs have improved fixation strength in weak bone, but their relatively high stiffness may suppress interfragmentary motion (IFM) to a level insufficient for optimal promotion of secondary bone healing.[1] This is especially of concern when locked plates are used as bridge plating constructs in absence of interfragmentary compression, whereby fracture healing relies on secondary bone healing by callus formation. Recent case studies on locked plating have supported this concern by describing deficient callus formation and delayed unions or non-unions.[2-3] To address this concern, Far Cortical Locking (FCL) screws have recently been introduced, which have a reduced mid-shaft diameter to provide unicortical fixation in the far cortex without being rigidly fixed in the near cortex underlying the plate.[4] FCL screws have been shown to reduce the axial stiffness of a locked bridge plating construct by 88% without reducing construct strength, while inducing nearly parallel IFM in a synthetic bone model.[4] To document FCL performance in human bone, the present study evaluated FCL screws in conjunction with locked bridge plating constructs applied to distal femur fractures in human cadaveric specimens. We hypothesized that FCL screws can decrease construct stiffness while retaining construct strength as compared to standard locked plating constructs.