Is rotation the mode of failure in pertrochanteric fractures fixed with nails? Theoretical approach and illustrative cases.

PURPOSE: The present article reviews data from biomechanical and clinical studies which indicate that rotational instability can cause failure of fixation due to the particular characteristics of the fracture, the mechanical properties of the chosen implant or flaws in surgical technique. METHODS: Although radiographs give a similar impression in failure of fractures fixed with cephalomedullary nails, different mechanisms involving rotation of the femoral head may play a key role. RESULTS: The incidence of failure in pertrochanteric fracture fixation is decreasing as implants continue to evolve. It is possible that currently reported low failure rates do not apply equally to all subtypes of this diverse group of fractures. Since the introduction of sliding hip screws, "cut-out" due to varus collapse of the proximal fracture fragment has been the only reported mode of failure. CONCLUSION: Excessive rotation leading to eventual "cut-out" has not been adequately studied, and thus, available evidence is not sufficient to definitely prove this theoretical approach. As nailing is gradually overtaking extramedullary fixation as the treatment of choice, especially for comminuted pertrochanteric fractures which can be rotationally unstable, further research is warranted to improve our understanding of the pathogenetic mechanisms of failure.