Proximal femoral fractures: a biomechanical study to compare intramedullary and extramedullary fixation

This study assesses the rigidity and strength of fixation provided by intramedullary and extramedullary devices for proximal femoral fractures. Stable and unstable intertrochanteric fractures were studied in paired femora after internal fixation with the Gamma nail and Richards 135 degrees classic hip-screw implants; in subtrochanteric fractures, the 95 degrees Richards condylar screw was studied in addition. Subsidence of the sliding screw within the plate and nail constructs was measured. Fixation of subtrochanteric fractures with the intramedullary Gamma nail was significantly stronger and more rigid than that with the extramedullary screw plate devices. Under conditions of simulated protected weight bearing, the 95 degrees condylar screw plate provided more rigid fixation than did the 135 degrees hip screw. There was no significant difference in the strength of fixation of stable and unstable intertrochanteric fractures between the Gamma nail and the hip screw, although the Gamma nail provided more rigid fixation.