Article
A Biomechanical Study of Simulated Femoral Neck Fracture Fixation by Cannulated Screws: Effects of Placement Angle and Number of Screws
Am J Orthop. 2007 December;36(12):680-684
Author and Disclosure Information
Earl Walker, MD, Debi P. Mukherjee, ScD, MBA, Alan L. Ogden, BME, Kalia K. Sadasivan, MD, and James A. Albright, MD
Dr. Walker is Chief Resident, Dr. Mukherjee is Associate Professor and Coordinator of Bioengineering, Mr. Ogden is Research Associate, Dr. Sadasivan is Professor, and Dr. Albright is Professor and Chairman, Department of Orthopaedic Surgery, Louisiana State University Health Sciences Center, Shreveport, Louisiana.
The angle of placement of hip screws to fix femoral neck fractures is still a controversial subject, and it must be addressed. In the study reported here, we compared the relative stiffness of fixation of simulated Pauwels type III femoral neck fractures fixed with either 2 or 3 cannulated screws implanted at 135°, 145°, and 150°. Each femur was fixed with 2 or 3 cannulated screws and tested under axial loading and anteroposterior (AP) bending. Then each femur was fatigued to 1000 cycles and tested to failure. Fourteen femurs were tested.
Results showed that axial stiffness values were not statistically different at different angles. AP bending stiffness of the high-angle (150°) construct was significantly higher than that of either of the other 2 constructs (for 2 screws only). Two-screw fixation appears to be adequate; adding a third screw may not be necessary.