Abstract
Mechanical tests on two types of short femoral nail (SFN), namely, currently used "Lag Screw (LS)" and newly developed "Grasping Pin" with a "Lag Pin (LP)" for osteosynthesis have been performed so as to make a comparison between their initial stability. Both LS and LP were implanted in human femoral heads taken from the patients who were suffered from femoral neck fracture, and then tested under cyclic compressive and quasi-static torsional loading. No "Cut-out" was observed in both LS and LP under cyclic compression and LS clearly showed less amount of subsidence than LP. An almost constant resistance to torsional loading was found in LS independently of rotation, while LP demonstrated the linear or monotonic increase of torsional resistance with an increase of rotation. These results were remarkably different from the results of the previous study where the polyurethane foams were used as simulated materials of cancellous and cortical bone.
