非融合棘突间固定器不同棘突间撑开高度与植入节段关节突关节的压力分布

背景：棘突-棘突间固定可分担椎间盘及关节突关节的压力并保留生理活动，但其具体的生物力学机制有待进一步研究。 目的：测量棘突间不同的撑开程度情况下节段关节突关节负荷分担及应力分布情况。 方法：取6具新鲜成人无病变无破坏腰椎标本(L2~5)，将各标本棘突间高度锉至12 mm，在L3~4棘突间分别植入支撑高度为10，12，14，16，18，20 mm的非融合棘突间固定器，采用ZWICK-Z010/BIXI电子万能实验机施加700 N•m模拟腰椎前屈、中立、后伸运动负荷。 结果与结论：支撑高度为10 mm的非融合棘突间固定器对植入节段关节突关节的压力分布无显著影响；支撑高度为12 mm的非融合棘突间固定器在过伸时可分担关节突关节压力；支撑高度为14 mm的非融合棘突间固定器可显著降低关节突关节负荷；而支撑高度为16~20 mm的非融合棘突间固定器可使关节突关节负荷基本消除。说明支撑高度等于或略大于中立位棘突间高度的非融合棘突间固定器可合理分担关节突关节的负荷。

In vitro effects of a new shape-memory alloy interspinous process device on zygapophyseal joints pressures distribution

BACKGROUND:Spinous process and interspinous internal fixation can share the pressure between the disc and zygapophyseal joints and retain physical activity, but the specific biomechanical mechanism need further research. OBJECTIVE:To measure load sharing and stress distribution of zygapophyseal joints with different distractions. METHODS:Six cadaver intact lumbar specimens (L2–5) were loaded in flexion, neutral, and extension using ZWICK-Z010/BIXI electronic universal testing machine to exert 700 N•m. Pressure measuring films measured the zygapophyseal joints load during each of the three positions. Inter-spinous process stabilization device (IPD) with different spacer heights (10, 12, 14, 16, 18, 20 mm) was placed. RESULTS AND CONCLUSION:The IPD with 10 mm spacer height could not share the zygapophyseal joints load significantly. The 12 mm implant could share zygapophyseal joints load only in extension. The 14 mm implant could significant decrease the zygapophyseal joints load. The 16 mm and 20 mm implants could basically eliminate the zygapophyseal joints load. Spacer height of IPD is equal to or slightly greater than the neutral position of interspinous height can share the load of zygapophyseal joints reasonable.