BIOMECHANICAL COMPARISON OF INTERNAL-FIXATION TECHNIQUES FOR THE TREATMENT OF UNSTABLE BASICERVICAL FEMORAL-NECK FRACTURES

Objectives: The optimal method of internal fixation of basicervical fe moral neck fractures is controversial. This area represents a transiti on zone between the intracapsular femoral neck fracture, usually fixed with multiple cancellous screws, and the extracapsular intertrochante ric fracture, fixed with a sliding screw device [sliding hip screw (SH S)] and derotation screw (DRS) device. The authors' specific aim was t o biomechanically compare these two methods of fixation in a cadaveric model of a basicervical femoral neck fracture with posteromedial comm inution. Design: The authors compared the average peak force during cy clic loading and the maximum axial force sustained by matched pairs of specimens stabilized with either fixation and subjected to axial and torsional loading while flexing and extending the hip. The average pea k force was defined as the mean of the peak force values measured in e ach loading cycle with the maximum displacement of the materials teste r actuator the same for each cycle (displacement control) as opposed t o the maximum force being held constant (load control). Results: The c ancellous screw group maintained a significantly lower average peak fo rce, 470 Newtons (SD = 145 Newtons), compared with 868 Newtons (SD = 1 86 Newtons) for the SHS and DRS composite group (p < 0.01). Similarly, the cancellous screw group demonstrated a lower ultimate load to fail ure, 1,863 Newtons (SD = 475 Newtons) compared with 3,557 Newtons (SD = 215 Newtons) for the SHS and DRS composite group (p < 0.01). Conclus ion: The results support the use of an SHS and DHS composite compared with three cancellous screws in the treatment of unstable basicervical femoral neck fractures.