Nonunions of the Proximal Femur: Biomechanical Aspects

Stabilization of both intertrochanteric and reversed trochanteric fractures is commonly performed by proximal femoral nailing. However, biomechanics significantly differ between these two fracture types. Patients and methods. In this study we report on the occurrence of delayed union or nonunion after inter- or reversed trochanteric fractures and present an easy treatment concept based on biomechanical considerations. Mean age was 73.3 years (range: 63–82). The interval between initial operation and first intervention ranged between 4.3 months and 15.0 months (mean: 8.4 months). Failure of bone healing may cause permanent strain on the implant leading to nail breakage, which we observed in three of eight cases. Dynamization is part of the general treatment concept for delayed union and nonunion after intramedullary fracture fixation. Normally it is performed by removal of interlocking screws or by occupying a ‘dynamic’ interlocking hole. We can show however that some types of inter- and reversed trochanteric fractures develop a characteristic kind of nonunion at the level of the lesser trochanter. This condition causes pain while walking and includes the risk of implant failure due to material fatigue. In these cases dynamization may be blocked by the cortex of the distal fragment directly contacting the prominent lag screw or its sleeve. We describe a procedure we call “lateral notching”, which is needed in order to make distal conventional dynamization effective and to allow for bone healing.