后凸成形和传统钉道骨水泥强化对骶骨钉松动的生物力学作用

背景：后凸成形骨水泥强化可应用于骨质疏松患者的腰椎椎弓根钉固定。目的：评价松动的骶骨钉经后凸成形和传统钉道骨水泥强化后的固定强度。方法：纳入9具骨质疏松症患者的新鲜尸体标本。在同一骶骨标本上，分别测试单皮质和双皮质骶骨椎弓根钉最大拔出力后，分别建立传统钉道骨水泥强化与后凸成形骨水泥强化椎弓根钉固定模型。在MTS材料试验机上，对螺钉尾部施加2 000次周期性压力载荷后，进行螺钉最大拔出力测试。 结果与结论：9个标本的骨密度均值为  0.71 g/cm²(0.61~0.77 g/cm²)。4种骶骨钉固定技术单皮质、双皮质、传统钉道骨水泥强化和后凸成形骨水泥强化骶骨钉的平均最大拔出力分别为203，325，437及565 N。双皮质骶骨钉的拔出力显著高于单皮质钉(P < 0.05)；但此2固定均显著低于骨水泥强化组(P < 0.05)。后凸成形骨水泥强化组的拔出力显著高于传统钉道骨水泥强化组(P < 0.05)。此外，4种骶骨钉固定技术的最大拔出力与骨密度值均呈现显著的正相关(P < 0.05)。结果证实，传统钉道骨水泥强化技术和后凸成形骨水泥强化技术均可做为骶骨椎弓根钉松动的补救手段，但后凸成形骨水泥强化可获得更为坚强的锚定。

Biomechanical effects of kyphoplasty-assisted versus traditional bone cement augmentation on the loosened sacral screws

BACKGROUND: Kyphoplasty-assisted bone cement augmentation can be used in lumbar pedicle screw fixation of osteoporotic patients.OBJECTIVE:To assess the fixation strengths of loosened sacral screws augmented with kyphoplasty-assisted and traditional bone cement techniques.METHODS:Fresh sacra were harvested from nine osteoporotic cadavers. After testing bilaterally placed unicortical and bicortical pedicle screws, two unicortical pedicle screws with the traditional and kyphoplasty-assisted cement augmentations were established on the same sacrum. Following 2000 cyclic compression loading to screw head on a MTS machine, their maximum pull-out forces were recorded and compared. RESULTS AND CONCLUSION:The bone mineral densities of nine specimens were ranged from 0.61 to 0.77 g/cm2 (0.71 g/cm² in average). The mean maximum pull-out forces of unicortical and bicortical screws, and traditional and kyphoplasty-assisted cement screws were 203, 325, 437, and 565 N, respectively. The pull-out force was significantly higher in bicortical screw compared with unicortical (P < 0.05); however, these two fixations exhibited markedly lower pull-out strength compared with two cement augmentation techniques (P < 0.05). The pull-out strength was significantly higher in kyphoplasty-assisted cement augmentation group compared with traditional bone cement technique (P < 0.05). In addition, a significant positive correlation was exhibited between bone mineral density and pull-out force for the four fixations (P < 0.05). Results demonstrated that traditional and kyphoplasty-assisted cement augmentations can serve as the salvage technique for loosening sacral screw. However, kyphoplasty-assisted augmentation can provide higher stability.