An experimental study of the failure modes of the gamma locking nail and AO dynamic hip screw under static loading: a cadaveric study

The sliding compression screw is widely regarded as the optimum treatment for intertrochanteric fractures of the femur; allowing bone fragments to impact until a bony support has been established across the fracture site. This study carried out biomechanical, cadaveric tests to establish the influence of direct static loading situations on the modes of failure of the Gamma Nail compared with the Dynamic Hip Screw (DHS). Clinical studies report DHS failures of lag screws cutting-out, bending of the lag screws and cortical screws pulling out causing plate loosening. Gamma Gamma Nail failures include lag screw cut-out or fractures of the femoral shaft around the the distal locking screws or nail tip. In this study each failure mode has been isolated, to establish the loads to failure under various fracture configurations. The biomechanical results indicated that the intramedullary Gamma Locking Nail can be recommended over a standard DHS in over a standard DHS in cases of subtrochanteric fracture or conditions of very poor bone quality. (C) 1997 IPEM. Published by Elsevier Science Ltd.