后路及单侧椎间孔和前路腰椎椎体间融合并置入椎弓根螺钉后相邻节段的生物力学变化

目的：比较经后路、单侧椎间孔、前路腰椎椎体间融合及附加椎弓根螺钉后相邻节段的力学性能。方法：新鲜的雄性小牛L1~L5节段脊柱标本15具。随机取5只标本作为正常对照组，在非破坏状况下测试其力学指标后，再将15只标本随机分为3组，按要求制作L4/5前路椭圆形碳纤维Cage 1枚融合（前路腰椎椎体间融合组）、后路长方体碳纤维椎间Cage 2枚融合（后路腰椎椎体间融合组）和侧方椎间钛合金Cage 1枚融合（单侧椎间孔腰椎椎体间融合组）模型。测试完成后，每个标本附加L4/5节段双侧Moss-miamiTM椎弓根螺钉测试。结果：3种融合方法在附加内固定前后应变和位移都高于正常对照组，强度低于正常对照组（P<0.01），3组间以单侧椎间孔腰椎椎体间融合组变化最大，后路腰椎椎体间融合组最小（P<0.05）；在内固定前后配对比较，附加内固定后各组应变、位移增加，强度降低（P<0.05）。 结论：3种融合方法在附加内固定前后都有加速上位相邻节段退变的趋势，附加内固定比单纯融合更易导致相邻节段退变，单侧椎间孔腰椎椎体间融合退变趋势更加明显，后路腰椎椎体间融合的趋势相对较小。

Biomechanical changes of adjacent segments following posterior, anterior and unilateral transforaminal lumbar interbody fusion with pedicle screw fixation

OBJECTIVE: To compare the instant effect on the mechanical performance of adjacent segment following posterior lumbar interbody fusion (PLIF), anterior lumbar interbody fusion (ALIF) and unilateral transforaminal lumbar interbody fusion (TLIF) with or without pedicle screw fixation. METHODS: Fifteen fresh bovine lumbar specimens, L1-L5, were used, and 5 were randomly selected as normal control to test the biomechanics. Afterward, the 15 specimens were randomly divided into 3 groups and separately made models of L4/5 ALIF using 1 oval carbon fiber cage, PLIF using 2 rectangular carbon fiber cages and TLIF using 1 Ti-alloy cage. Following the biomechanical tests, each specimen was subjected to bilateral Moss-miamiTM pedicle screw fixation at L4/5. RESULTS: Compared with normal spine specimen, the mean strain and displacement of the adjacent segment of PLIF, ALIF and TLIF with and without bilateral pedicle screw significantly increased, but the intensity was decreased (P< 0.01). The increase and decrease of the adjacent segment of TLIF was greater than ALIF and PLIF, and ALIF was greater than PLIF (P < 0.05). Compared without bilateral pedicle screw, the mean strain and displacement of PLIF, ALIF and TLIF with bilateral pedicle screw significantly increased, while the intensity was decreased (P < 0.05). CONCLUSION: PLIF, ALIF and TLIF with and without bilateral pedicle screw may lead to degeneration in the superior adjacent segment potentially. Pedicle screw fixation more easily induces this degeneration than without fixation. The probability of TLIF is the greatest, and PLIF is the minimal.