OTA 1997 Posters - Hip Fractures

*The Fixation of Ipsilateral Femoral Neck and Shaft Fractures: A Biomechanical Comparison of the Miss-a-Nail Technique versus Second Generation Nails in Cadaver Femora

Michael A. Dube, MD, Timothy Foster, MD, Michael Graffe, David Cicercia, MD

Lahey Hitchcock Clinic, Burlington, MA; Boston University, Boston, MA, USA

Ipsilateral femoral neck and shaft fractures are commonly treated with intramedullary nailing utilizing a second generation femoral nail, or a first generation femoral nail with screws placed around the nail into the femoral neck and head (miss-a-nail technique). An anatomic reduction with rigid internal fixation of both fractures is required to ensure healing of the fractures with minimal morbidity to the patient. An anatomical reduction of the femoral neck fracture with rigid internal fixation is integral to the treatment of these injuries. This study analyzes the biomechanical properties of these 2 fixation methods.

Nine matched pairs of cadaver femora were harvested and fixed in formalin for preservation. Radiographs of the matched femora were obtained to determine the Singh index of each pair. A fracture was then created at the base of the femoral neck and in the diaphysis of each femur. The fractures were then anatomically reduced, and treated with rigid internal fixation utilizing a second generation nail (Alta nail) for 1 matched femur, and a first generation nail (Grosse-Kemfe nail) with two 7.0 mm screws placed anterior to the nail (miss-a-nail technique) into the femoral neck and head of the second matched femur.

The constructs were tested on an Instron servo-hydraulic mechanical testing platform. The biomechanical properties of each construct were evaluated including: ultimate displacement and load, displacement and load to the initial failure event, initial linear stiffness, displacement to initial failure event and load to initial failure event.

There were no statistically significant differences with the properties of initial linear stiffness, displacement to initial failure event and load to initial failure event between two constructs. The ultimate load to failure was significantly less for the miss-a-nail construct compared to the second generation nail (p <0.0007). The second generation nail (reconstruction nail) withstood loads 2.17 times as great as the Grosse-Kemfe nail/screw construct. Thus, the second generation nail construct appears to have superior biomechanical properties compared to the miss-a-nail technique. This study suggests that the second generation nail construct may be superior to the miss-a-nail construct when treating ipsilateral femoral neck and shaft fractures.