Letter to the Editor: Cannulated versus non-cannulated cancellous screw fixation for femoral neck fractures: a synthetic bone biomechanical study.

PURPOSE To compare the compressive strength of cannulated versus non-cannulated cancellous screws for undisplaced femoral neck fractures in synthetic bones. METHODS 18 synthetic proximal femurs simulating an AO B1 valgus impacted femoral neck fracture in osteoporotic bone were used. The fracture angles were between 55º and 63º (Pauwels grade 2). Fixation was made using 6.5-mm non-cannulated screws (n=6), 6.5-mm cannulated screws (n=6), or 7.3-mm cannulated screws (n=6). A custom-built jig was designed to guide the insertion of the screws in an identical triangular configuration. Screws were tightened by a single operator using a torque-measuring screwdriver. The femoral head was subjected to progressive axial loading at 5 mm/min. The load to failure and displacement were recorded. RESULTS The 3 groups did not differ significantly except that the load to failure was higher in the construct with 6.5-mm non-cannulated screws than that with 6.5-mm cannulated screws (1222 N vs 1008 N, p=0.003). CONCLUSION The compressive strength of a synthetic bone hip fracture model fixed with non-cannulated screws was higher than that of cannulated screws of the same diameter.