Wang J L, Panjabi M M, Isomi T
Biomechanics Laboratory, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticut, USA.
Spine (Phila Pa 1976). 2000 Jul 1;25(13):1649-54. doi: 10.1097/00007632-200007010-00008.
The role of bone graft force in stabilizing an instrumented cervical spine was evaluated for one-level and three-level corpectomy models using in vitro experiments.
To investigate the role of bone graft force in enhancing stability of anterior cervical plate, and to study effects of fatigue loading.
The anterior cervical plate system is used widely in stabilizing the cervical spine after spinal corpectomy and grafting. Many factors such as applied screw torque, screw pullout force, plate strength, plate geometry, and type of bone graft have been studied. However, the role of bone graft in stabilizing the anterior plate system has not been explored.
Two models (one-level and three-level) incorporating corpectomy, strut graft, and anterior plate were constructed from eight human spine specimens (C2-T1). The flexibility of an intact specimen and two constructs with graft forces of 0 N and 100 N was determined. A flexibility test, simulating physiologic loads, consisted of pure moments of flexion, extension, lateral bending, and axial torques up to 1 Nm. For each moment, range of motion and neutral zone were determined. The stability potential index was defined as the decrease in motion caused by instrumentation, as compared with intact motion. A larger stability potential index indicates a more stable spinal construct. Repeated measures analysis of variance was used to determine the significant changes.
In both models, bone graft force increased during extension, decreased during flexion, and showed minor changes during axial torsion and lateral bending. Higher bone graft force increased stability potential index-neutral zone and stability potential index-range of motion in the three-level model in all directions, but only in flexion-extension in the one-level model. Fatigue loading decreased bone graft force to a greater extent in the three-level model.
In the corpectomy-graft-anterior-plate model, graft force decreased in flexion and increased in extension. Higher graft force increased and fatigue decreased stability of the spinal construct in the three-level model.
采用体外实验，针对单节段和三节段椎体次全切除模型，评估植骨力量在稳定颈椎前路内固定中的作用。
探讨植骨力量在增强颈椎前路钢板稳定性中的作用，并研究疲劳载荷的影响。
颈椎前路钢板系统广泛应用于椎体次全切除及植骨术后的颈椎稳定。已对许多因素进行了研究，如施加的螺钉扭矩、螺钉拔出力、钢板强度、钢板几何形状及植骨类型等。然而，植骨在稳定颈椎前路钢板系统中的作用尚未得到探讨。
从8具人体脊柱标本（C2 - T1）构建包含椎体次全切除、支撑植骨及前路钢板的两种模型（单节段和三节段）。测定完整标本以及植骨力量分别为0 N和100 N的两种构建物的柔韧性。模拟生理载荷的柔韧性测试包括高达1 Nm的屈伸、侧弯及轴向扭矩的纯力矩。对于每个力矩，测定活动范围和中立区。稳定性潜能指数定义为与完整运动相比，内固定导致的运动减少量。稳定性潜能指数越大表明脊柱构建物越稳定。采用重复测量方差分析确定显著变化。
在两种模型中，植骨力量在伸展时增加，屈曲时减小，在轴向扭转和侧弯时变化较小。更高的植骨力量增加了三节段模型各方向的稳定性潜能指数 - 中立区及稳定性潜能指数 - 活动范围，但仅增加了单节段模型屈伸方向的上述指标。疲劳载荷在三节段模型中使植骨力量下降幅度更大。
在椎体次全切除 - 植骨 - 前路钢板模型中，植骨力量在屈曲时减小，伸展时增加。更高的植骨力量增加了三节段模型脊柱构建物的稳定性，而疲劳则降低了其稳定性。
