上胸椎椎板螺钉的生物力学研究

 目的比较上胸椎椎板螺钉(translaminar screw.TLS)、椎板关节突螺钉(translaminar facet screw.TLFS)和椎弓根螺钉(transpedicle screw.TPS)固定的拔出强度。方法取 9具新鲜尸体上胸段(T1~T3)完整脊柱标本.双能 X线骨密度仪测量后.游离成 3个独立完整节段(T1、T2、T3).在椎体两侧随机进行 TPS、标准 TLS和 TLFS置入.螺钉直径均为 4.0 mm。分别进行旋入扭距和拔出试验.比较三种固定方式的最大轴向扭矩和拔出力。结果上胸椎 TPS的平均最大扭矩为(0.40±0.01) N.m.TLS的平均最大扭矩为(0.35±0.01) N.m.TLFS的平均最大扭矩为(0.43±0.01) N.m;TPS与 TLS间差异无统计学意义(t=1.94,P >0.05).TPS与 TLFS间差异无统计学意义(t=-1.28, P>0.05).TLFS与 TLS间差异有统计学意义(t=-13.86, P0.05). TPS与 TLFS间差异无统计学意义(t=0.924, P >0.05).TLFS与 TLS差异有统计学意义(t=9.907, P约 0.05)。螺钉的旋入最大扭矩与螺钉的拔出力呈正相关性。结论上胸椎椎板螺钉、椎板关节突螺钉与椎弓根螺钉固定拔出强度差异并不明显。椎板关节突螺钉固定的拔出强度明显大于椎板螺钉。椎板螺钉和椎板关节突螺钉固定可以作为椎弓根螺钉固定的一种补充方法。

A biomechanical study of upper thoracic vertebras translaminar screws fixation

Objective To compare the biomechanical pull-out strength (POS) of three different fixations in upper thoracic vertebras using translaminar screws (TLS), translaminar facet screws (TLFS), and transpedicle screws (TPS), respectively. Methods Nine fresh human cadaveric cervicothoracic junction spines specimens which including T1-T3 vertebras were harvested. The vertebras specimens were scanned using dual-energy radiograph absorptiometry for bone mineral density. Both of screw insertion techniques at each vertebrae was randomized. All the screw insertions were based on direct observation and the CT scan on the pedicles. The peak of insertional torque (IT) was recorded and axial pull-out testing was performed to simulate intraoperative failure of fixation. Results The mean peak IT of the TFLS, TPS and TLS were (0.43±0.01), (0.40±0.01), (0.35±).01) N·m, respectively. There was no statistically significant difference between the TFLS and TPS, and between the TPS and TLS was same. But the TFLS generated statistically greater peak 1T in comparison with the TLS(t=-13.86, P＜0.05). The mean POS of TLFS was (771±106) N,which had no statistically significant difference in comparison with the TPS(733±65) N. And the TLS (663±86) N was same. But the TFLS generated statistically greater POS in comparison with the TLS (t=9.907, P＜0.05). The peak IT showed a strong positive correlation with POS in three screw techniques. Bone mineral density correlation with POS in all methods of fixation. Conclusion It was not a significant difference to compare POS of TLS and TLFS to that of TPS respectively. TLS and TLFS appear to be a biomechanically sound alternative in the upper thoracic spine, and appear to be a safe and effective technique for instrumenting the upper thoracic spine.