Zindrick M R, Wiltse L L, Widell E H, Thomas J C, Holland W R, Field B T, Spencer C W
Clin Orthop Relat Res. 1986 Feb(203):99-112.
This laboratory experiment was undertaken to identify factors contributing to intrapeduncular screw fixation in the vertebra. Testing was performed in axial pull-out and cyclic loading modes using multiple screw designs inserted to various depths into fresh human lumbosacral vertebra. The degree of osteoporosis played a major role in pull-out strength. Larger diameter, full-threaded screws inserted deep enough to engage the anterior vertebral cortex resulted in the most secure fixation. In the sacrum, the second sacral pedicle was the weakest location of insertion. Screws aimed laterally into the ala at 45 degrees or medially into the first sacral pedicle resisted larger axial pull-out loads than those inserted straight anteriorly into the ala. Methyl methacrylate was found to restore secure fixation in previously-loosened screws and pressurization of cement doubled the pull-out force. In cyclic load tests, deeper-inserted screws were found to withstand a greater number of cycles before loosening. Measurements of pedicle outer cortical diameters were found in many specimens to be smaller than both the 4.5-mm and 6.5-mm diameter screws.
本实验室实验旨在确定影响椎体内椎弓根螺钉固定的因素。使用多种螺钉设计，以不同深度插入新鲜人腰骶椎，进行轴向拔出和循环加载模式测试。骨质疏松程度对拔出强度起主要作用。直径较大、全螺纹且插入深度足以穿透椎体前皮质的螺钉固定最为牢固。在骶骨中，第二骶椎椎弓根是最薄弱的置入部位。与直接向前插入骶骨翼相比，以45度角向外侧插入骶骨翼或向内侧插入第一骶椎椎弓根的螺钉能承受更大的轴向拔出载荷。发现甲基丙烯酸甲酯可恢复先前松动螺钉的牢固固定，且骨水泥加压可使拔出力加倍。在循环载荷测试中，发现插入较深的螺钉在松动前能承受更多的循环次数。在许多标本中发现椎弓根外侧皮质直径小于4.5毫米和6.5毫米直径的螺钉。
