应力松弛接骨板对骨几何形态和力学性能影响的实验观察

The influence of stress-relaxation plate on bone geo-metrics and mechanical property: an experunentalstudy

作者采用粘弹性材料制成垫圈置于接骨板螺孔与螺丝钉之间，构成应力松弛接骨板系统。实验证实，有垫与无垫接骨板在固定早期对模拟骨的应力遮挡作用相同，固定８周后垫圈出现明显变形和破坏，使有垫接骨板的应力遮挡率从第１０周起明显低于无垫接骨板。有垫接骨板固定的胫骨骨质疏松明显轻于无垫组，固定２０周后，有垫组的胫骨髓腔径明显小于无垫组，骨皮质厚度和胫骨抗弯强度均明显大于无垫组（Ｐ＜０．０５～０．０１）。说明应力松弛接骨板系统早期具有与坚强接骨板相同的固定作用，后期其应力遮挡效应可逐渐减小，避免严重的骨质疏松和骨力学性能下降。

n order to maintain the effective fixation effect ofrigid bone plate in the early stage of fracture and to pre-vent osteoporosis induced by stress shielding effect ofrigid plate in later stage of fixation, a washer made ofviscoelastic material was placed between the screw andthe screw hole of plate to form a stressrelaxation platesystem. Both in vitro and in vivo experiments demonstrated that there was no statistical difference betweenthe stress shielding effect of padded and unpadded plategroups. The washer showed significant deformation anddamaged & weeks after implantation, and 10 weeks afterimplantation the stress shielding rate of the padded plategroup was significantly lower than that of the unpadedgroup (P<0- 05i. As a consequence, the degree of os-teoporosis of the tibia in the padded group was significantly milder than the unpaded group , and 20 weeks af-ter implantation, the diameter of the tibia medullarycavity of the padded group was significantly smaller thanthat of the unpadded group- The thickness of corticalbone and the bending strength of the tibia of peddedgroup were significantly larger than those of the un-padded group (P<0.05-0. 01).These results showedthat the stress-relaxation plate system can effectivelymaintain the stability of fracture fixation at the similarlevel of rigid plate during the early stage of fracture andcan gradually lower down the stress shielding rate so asto prevent severe osteoporosis and reduction of bone mechanical property in the later stage of fixation.