Locking strategies of the sliding screw in gamma nailing (G3) were tested in an experimental biomechanical study. Twelve Composite Femoral Bone models were used. An intertrochanteric osteotomy was performed and a gamma nail was implanted in each specimen. The specimens were divided in 3 groups:
compressed and locked, locked at distance and unlocked. Each specimen was subjected to 4 cycles of static vertical loading of up to 1100 Newtons (N) at a rate of 10 mm/minute. Subsequently, the specimens were investigated for cut-out patterns using digital photography and management. All failures occurred under supraphysiological loads. During their first loading cycles, no statistical differences for stiffness and yield load were noted. Nevertheless, there was a non–significant tendency for higher failure loads for the unlocked group. Under maximum load (1100 N) and already established deformations, all Gamma Nails behaved similarly in terms of neck-screw displacement, with no statistical differences. Unlocked screws exhibited the most moderate failure modes followed by the compressed and locked group. The third group showed the most severe failures. In conclusion, there is evidence that sliding is biomechanically superior in gamma nailing. Despite adverse mechanical circumstances all specimens behaved satisfactorily under physiological loading
