目的 通过生物力学实验的方法研究当延长颈椎前路融合节段数时对邻近节段的活动度、小关节应力的影响,探讨导致融合术后邻近节段退变的原因.方法 利用6具成人新鲜尸体颈椎标本(C2～T1),模拟颈椎前路椎间盘切除、钢板螺钉内固定、椎间融合术.每具标本依次进行C4～s单节段融合、C4～6双节段融合、C4～7三节段融合,利用特制颈椎三维运动测试系统模拟人体前屈、后伸、左右侧屈和左右旋转运动,使用混合测试方法,测量并记录此时标本整体活动度、上位邻近节段活动度及小关节内压力、下位邻近节段活动度变化.结果 当依次进行单节段融合、双节段融合、三节段融合后,标本整体活动度呈递减趋势,差异有统计学意义(P＜0.05).上位邻近节段C3～4随融合节段的延长活动度逐渐升高,呈递增趋势,在前屈、后伸、侧屈运动中有显著统计学差异(P＜0.05).C3～4小关节内平均压力和峰值压力的测量发现单节段组、双节段组、三节段组于后伸和侧屈运动中较完整组升高,比较有显著统计学差异(P＜0.05).结论 当颈椎前路融合的节段数延长,会导致上位邻近节段活动度以及小关节内压力逐渐增加,可能因此而加速邻近节段退变.%Objective To study the effect of length of cervical anterior fusion on adjacent levels by Biomechanical test.Methods Six fresh-frozen human cervical specimens were used in this study.The specimens were tested in flexion,extension,bending and rotation on a spine 3D test system.The specimens were tested intact and then underwent a single-level anterior cervical discectomy and fusion (ACDF) at the C4-5 first,a double-level fusion at the C4-5,and finally extended to triple-level at the C4-7,Based on a hybrid test method.Changes in overall range of motion (ROM),segmental motion and facet joints pressure during flexion,extension,bending and rotation were measured and statistically analyzed.Results The overall ROM of the entire spinal construct decreased progressively as the single-level fixation extending to 2-level and 3-level (P ＜ 0.05).A progressive increase in ROM above (C3-4) the fused motion segment units (MSUs) was found during flexion,extension and bending (P ＜ 0.05).In bending and extension,a same result was recorded on the average pressure and max pressure of Cs-4 facet joints (P ＜ 0.05).Conclusions This study has demonstrated that the biomechanics at adjacent levels to a cervical spine fusion are altered and that there was progressively increased adjacent segment motion and stress as a single-level ACDF extended to a 3-level fusion,which might lead to the acceleration of adjacent segment degeneration.
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