不安定性骨盤骨折に対する各種 iliosacral screw の三点曲げ強度試験

Abstract

It is generally accepted that internal fixation using iliosacral screws for unstable pelvic fractures is effective. However, the placement of iliosacral screws is technically demanding and it has been reported that screws can be damaged by the load from the early part of the postoperative stage. We have reported that the dull insertion method of placement of iliosacral screws and combination of motor-evoked potential monitoring can reduce complications, whereas the strength of the iliosacral screws is unknown. The aims of this study were to measure the strength of screws that we have used clinically and are being used currently, and to evaluate whether these screws are proper for use as iliosacral screws. The strength of screws was measured by the three-point bending test. Screws were divided into four types as follows : a solid screw made of titanium (8.0 mm in diameter) (Screw-A), a cannulated screw made of titanium (8.0 mm in diameter) (Screw-B), a cannulated screw made of titanium (6.5 mm in diameter) (Screw-C) and a cannulated screw screw made of stainless steel (7.0 mm in diameter) (Screw-D). Screw -A is the screw that we have used clinically and the others are screws that are used currently. Five screws were measured one-by-one per each type and five pairs of Screw- C were measured. Screw-A samples were not broken; moreover, they withstood loads exceeding 1000 kgW. Screw-B samples were broken by a load of 320±48.7kgW. Shrew -C samples were broken by a load of 150±0.0 kgW. Screw-D samples were not broken, but lost rigidity by a load of 132±8.4 kgW or more. Pairs of Screw-C were broken by a load of 484±35.1 kgW. In conclusion, Screw-A, which we have used clinically, and pairs of Screw-C, may be proper material for use as iliosacral screws.