应力松弛接骨板对骨应力遮挡率影响的实验研究

将螺孔部衬有不同数量、不同厚度聚乙烯垫圈的３１６Ｌ不锈钢接骨板置于２０根聚甲基丙烯酸甲酯模拟骨中段。分别在固定后不同时期测定不同载荷下接骨板内二螺孔间的外表面及接骨板对侧模拟骨中段的应变值，从而计算出应力遮挡率。结果发现，有垫与无垫接骨板组在术后１０周内的应力遮挡率无统计学差异，１０周以后两组间出现显著性差异，无垫组保持不变，有垫组的应力遮挡率逐渐下降。在垫圈厚度相同时，衬垫数量越多（本实验最多采用４孔４垫），后期应力遮挡率下降越明显。表明应力遮挡率的变化与垫圈数量关系密切。

AN EXPERIMENTAL STUDY ON EFFECT OF STRESS SHIELDING RATE OF STRESS RELAXATION PLATE ON BONE

Twenty simulant bones (polymethacrylate cylinders) were used in this experiment.The mid-shaft of each simulant bone was fixed with 316L stainless steel plate.Four of the 20 were served as control(no washer group) and the other 16 as experimental group(washer group).In the latter,different numbers and thickness of UHMWPE washers were inserted in between the screw-hole walls and the screws.The longitudinal loading test was performed immediately,and at 4,8,12and16 weeks after plate fixation,respectively.The strain of the surface between 2 screw holes in the plate and on the mid-shaft of the simulant bones apposite the plate was measured so as to calculate the stress shielding rate of plate on bone.The results demonstrate that the stress shielding rate of plate on bone would gradually decrease in the washer group and keep constant in no washer group after fixation.Ten weeks later,there was significant difference of the stress shielding rate between the two groups.The resutls also show that if the thickness of the washers remain unchanged,the greater the number,the more obvious the reduction of the stress shielding rate at the later stage.It is suggested that the stress shielding rate of the plate on bone in the washer group is closely related to the number of washers.