Biomechanical analysis of the Gamma nail and sliding hip screw.

Nine pairs of human cadaveric femora were used to study the biomechanical characteristics of the Gamma nail and a standard telescoping screw plate implant (Ambi) to determine whether there were any mechanical advantages of one system over the other. Parameters studied included structural stiffness, strain distribution, and failure modes for intertrochanteric and subtrochanteric fractures. There was no significant difference in structural stiffness for stable intertrochanteric and subtrochanteric fractures. The Gamma Nail composites, however, were stiffer than the Ambi for unstable subtrochanteric fractures. Both implants effectively unloaded the proximal medial cortex. In each instance, failure of the Gamma nail composite occurred through the distal locking screws. The Gamma nail does not appear to offer any distinct biomechanical advantage over the sliding hip screw system in the treatment of stable and unstable intertrochanteric fractures, but it may play a role in the treatment of unstable subtrochanteric fractures.