Halvorson T L, Kelley L A, Thomas K A, Whitecloud T S, Cook S D
Department of Orthopaedics, Tulane University School of Medicine, New Orleans, Louisiana.
Spine (Phila Pa 1976). 1994 Nov 1;19(21):2415-20. doi: 10.1097/00007632-199411000-00008.
In an attempt to evaluate the effects of bone mineral density on the quality of fixation of pedicle screws in the lumbar spine, the axial pullout force was determined and compared in normal and osteoporotic human lumbar spines.
Four techniques of screw hole preparation were evaluated. Two pedicle screw/offset laminar hook constructs also were evaluated to determine whether the adjunct fixation of the laminar hooks would improve quality of fixation to a level sufficient to allow their use in the osteoporotic lumbar spine.
Pedicle screws were inserted by one of the listed techniques into fresh frozen cadaveric human spines. The fixation strength then was evaluated by pullout on a uniaxial testing frame.
Bone mineral density was a strong influence on axial pullout force. In normal bone, the method of screw hole preparation did not significantly affect the quality of fixation. However, in the osteoporotic spine, either an untapped screw hole or the tapping of a screw hole with a 5.5 mm tap improved the pullout force a statistically significant amount (P < 0.003). Also, a pedicle screw with offset hooks at two adjacent levels improved the fixation significantly, increasing the pullout force to twice the expected value.
Pedicle screw pullout strength was highly correlated with bone mineral density. A 5.5 mm tap or preparation with a ganglion knife improved pullout strength. Use of pedicle screws in conjunction with laminar hooks at two levels improved pullout strength.
为了评估骨密度对腰椎椎弓根螺钉固定质量的影响，测定并比较了正常和骨质疏松的人体腰椎的轴向拔出力。
评估四种螺钉孔制备技术。还评估了两种椎弓根螺钉/偏置椎板钩结构，以确定椎板钩的辅助固定是否能将固定质量提高到足以使其用于骨质疏松性腰椎的水平。
采用所列技术之一将椎弓根螺钉插入新鲜冷冻的人体尸体脊柱中。然后在单轴测试框架上通过拔出试验评估固定强度。
骨密度对轴向拔出力有很大影响。在正常骨质中，螺钉孔制备方法对固定质量没有显著影响。然而，在骨质疏松性脊柱中，未攻丝的螺钉孔或用5.5毫米丝锥攻丝的螺钉孔可使拔出力有统计学意义的提高（P < 0.003）。此外，在两个相邻节段带有偏置钩的椎弓根螺钉可显著改善固定效果，将拔出力提高到预期值的两倍。
椎弓根螺钉拔出强度与骨密度高度相关。使用5.5毫米丝锥或神经节刀制备可提高拔出强度。在两个节段将椎弓根螺钉与椎板钩联合使用可提高拔出强度。
