BASICERVICAL FRACTURES OF THE PROXIMAL FEMUR - A BIOMECHANICAL STUDY OF 3 INTERNAL-FIXATION TECHNIQUES

A biomechanical cadaver study was performed to compare the stability a nd ultimate strength of 3 standard fixation techniques used for treatm ent of basicervical hip fractures. Twenty one pairs of mildly osteopor otic femurs were selected, based on a computed tomography bone density reading of 40-50 Hounsfeld units and a Singh index of III. After init ial mechanical characterization of intact femurs, basicervical femoral neck fractures were created, reduced, and then instrumented with rand om assignment to 1 of 3 methods of fixation: (1) 3 parallel 6.5-mm can nulated cancellous screws; (2) a 135 degrees sliding hip screw with a 4 hole side plate; and (3) a 135 degrees sliding hip screw with a 4 ho le side plate and a 6.5-mm cannulated cancellous screw placed proximal and parallel to the sliding screw. Nine pairs were tested to failure in axial loading, 6 pairs in lateral bending, and 6 pairs in torsion. The group instrumented with the multiple cancellous screws had a signi ficantly (p < 0.01) lower ultimate axial load to failure than either s liding hip screw group. However, the multiple screws demonstrated sign ificantly (p < 0.01) less fracture displacement. There were no statist ically significant differences in lateral bending or torsional testing behavior between the 3 fixation methods. Use of the sliding hip screw is recommended rather than use of multiple cancellous screws for trea tment of basicervical femoral neck fractures. Although a superiorly lo cated cancellous screw may provide rotational control during sliding h ip screw insertion, it provides no incremental fixation after the slid ing hip screw is placed.