Axial loading studies of unstable intertrochanteric fractures of the femur.

An experimental four-part unstable intertrochanteric (IT) femoral fracture was created with either a large or small posteromedial fragment (PMF). Sixty-eight adult embalmed femoral anatomic specimens were fractured and subjected to axial loading after fixation. The maximum load prior to failure for femora from the same anatomic specimen was compared to differentiate between different methods of fixation. In the presence of the large PMF variation, anatomic reduction and fixation allowed the femur to resist an average maximum load 57% greater than identical fractures with the fragment excluded. Fixation of the small PMF increased construct strength by an average of 17% over no fixation. The PMF is the keystone to mechanical stability for IT fractures of the femur. When anatomic reduction is possible, its fixation becomes progressively more critical as its size increases.