Yu Bin-Sheng, Yang Zhan-Kun, Li Ze-Min, Zeng Li-Wen, Wang Li-Bing, Lu William Weijia
Department of Spine Surgery and Orthopaedic Research Institution, First Affiliated Hospital, Sun Yat-Sen University, 183 Huangpu East Road, Guangzhou, China.
J Spinal Disord Tech. 2011 Aug;24(6):E49-56. doi: 10.1097/BSD.0b013e318224e55a.
An in vitro biomechanical cadaver study.
To evaluate the pull-out strength after 5000 cyclic loading among 4 revision techniques for the loosened iliac screw using corticocancellous bone, longer screw, traditional cement augmentation, and boring cement augmentation.
Iliac screw loosening is still a clinical problem for lumbo-iliac fusion. Although many revision techniques using corticocancellous bone, larger screw, and polymethylmethacrylate (PMMA) augmentation were applied in repairing pedicle screw loosening, their biomechanical effects on the loosened iliac screw remain undetermined.
Eight fresh human cadaver pelvises with the bone mineral density values ranging from 0.83 to 0.97 g/cm were adopted in this study. After testing the primary screw of 7.5 mm diameter and 70 mm length, 4 revision techniques were sequentially established and tested on the same pelvis as follows: corticocancellous bone, longer screw with 100 mm length, traditional PMMA augmentation, and boring PMMA augmentation. The difference of the boring technique from traditional PMMA augmentation is that PMMA was injected into the screw tract through 3 boring holes of outer cortical shell without removing the screw. On an MTS machine, after 5000 cyclic compressive loading of -200∼-500 N to the screw head, axial maximum pull-out strengths of the 5 screws were measured and analyzed.
The pull-out strengths of the primary screw and 4 revised screws with corticocancellous bone, longer screw and traditional and boring PMMA augmentation were 1167 N, 361 N, 854 N, 1954 N, and 1820 N, respectively. Although longer screw method obtained significantly higher pull-out strength than corticocancellous bone (P<0.05), the revised screws using these 2 techniques exhibited notably lower pull-out strength than the primary screw and 2 PMMA-augmented screws (P<0.05). Either traditional or boring PMMA screw showed obviously higher pull-out strength than the primary screw (P<0.05); however, no significant difference of pull-out strength was detected between the 2 PMMA screws (P>0.05).
Wadding corticocancellous bone and increasing screw length failed to provide sufficient anchoring strength for a loosened iliac screw; however, both traditional and boring PMMA-augmented techniques could effectively increase the fixation strength. On the basis of the viewpoint of minimal invasion, the boring PMMA augmentation may serve as a suitable salvage technique for iliac screw loosening.
一项体外生物力学尸体研究。
评估使用皮质松质骨、更长的螺钉、传统骨水泥增强和钻孔骨水泥增强这4种翻修技术对松动的髂骨螺钉进行5000次循环加载后的拔出强度。
髂骨螺钉松动仍是腰骶髂融合术的一个临床问题。尽管许多使用皮质松质骨、更大的螺钉和聚甲基丙烯酸甲酯（PMMA）增强的翻修技术被应用于修复椎弓根螺钉松动，但其对松动髂骨螺钉的生物力学影响仍未确定。
本研究采用8具新鲜人尸体骨盆，骨密度值在0.83至0.97g/cm之间。在测试直径7.5mm、长度70mm的初次使用的螺钉后，依次在同一骨盆上建立并测试4种翻修技术，如下：皮质松质骨、长度为100mm的更长螺钉、传统PMMA增强和钻孔PMMA增强。钻孔技术与传统PMMA增强的不同之处在于，PMMA通过外侧皮质骨壳的3个钻孔注入螺钉通道，而不取出螺钉。在MTS机器上，对螺钉头部施加-200∼-500N的5000次循环压缩加载后，测量并分析5枚螺钉的轴向最大拔出强度。
初次使用的螺钉以及采用皮质松质骨、更长螺钉、传统和钻孔PMMA增强的4枚翻修螺钉的拔出强度分别为1167N、361N、854N、1954N和1820N。尽管更长螺钉方法获得的拔出强度显著高于皮质松质骨（P<0.05），但使用这两种技术的翻修螺钉的拔出强度明显低于初次使用的螺钉和2枚PMMA增强的螺钉（P<0.05）。传统或钻孔PMMA螺钉的拔出强度均明显高于初次使用的螺钉（P<0.05）；然而，两种PMMA螺钉之间的拔出强度未检测到显著差异（P>0.05）。
填充皮质松质骨和增加螺钉长度未能为松动的髂骨螺钉提供足够的锚固强度；然而，传统和钻孔PMMA增强技术均可有效提高固定强度。基于微创的观点，钻孔PMMA增强可作为髂骨螺钉松动的一种合适的挽救技术。
