脊柱单节段前中柱切除后不同节段椎弓根螺钉内固定的稳定性测试

目的:比较脊柱单节段前中柱切除后不同节段椎弓根螺钉内固定的稳定性,探讨单节段固定在前中柱病变手术中的可行性。方法:10具小牛新鲜脊柱标本(T10～L5),先测试完整状态下的运动范围(ROM),再模拟L1～L2前中柱病变切除手术:切除L1/2椎间盘和邻近终板共2cm高,行自体髂骨支撑植骨,后路依次用单节段短钉、单节段长钉、短节段和长节段椎弓根内固定系统进行固定,在不同固定方式下测试模型在轴向压缩、侧弯、屈伸和扭转方向上的ROM,计算相对运动范围(RROM)。结果:不同加载方向长节段固定组、短节段固定组的RROM均小于单节段短钉固定组和单节段长钉固定组(P0.05);单节段短钉固定组和单节段长钉固定组的RROM比较无显著性差异(P0.05);单节段短钉固定组和单节段长钉固定组的ROM均小于完整组(P0.05)。结论:小牛新鲜脊柱标本前中柱切除后植骨单节段椎弓根螺钉固定的稳定性低于短节段和长节段固定,但是高于完整状态;脊柱前中柱支撑植骨后,单节段短钉固定与单节段长钉固定的即刻稳定性相近。

Biomechanical test of varied segment pedicle screw instrumentation following a single segment of anterior and mid column spine corpectomy

Objective:To test the biomechanical stability of varied segment pedicle screw instrumentation following a single segment of anterior and mid column spine corpectomy and to explore the feasibility of a single segment fixation for spinal anterior and mid column lesions.Method:10 fresh calf spines(T10～L5) were used.The range of motion(ROM) of intact spines was tested as control.After simulating the modal of anterior and mid column resection along with resection of L1/2 intervertebral discs and adjacent end plates(total 2cm high),autogeneous iliac bony graft struting in situ,the models were subjected to posterior instrumentation of long segment pedicle instrumentation(LSPI),short segment pedicle instrumentation(SSPI),a single segment instrumentation by long pedicle screw(MILPS) and a single segment instrument by short pedicle screw(SISPS) respectively.The ROM of different instrumentations in axial compression,lateral bending,flexion-extension and rotation were tested.The relative range of movement(RROM) was tested either.Result:The RROM in LSPI and SSPI was significantly smaller than that in MILPS and SISPS in all loading directions(P<0.05).However,no statistical difference of the RROM was found between MISPS and SILPS(P>0.05).The ROM in MILPS and SISPS was smaller than that in control group(P<0.05).Conclusion:The stability provided by single segment instrumentation is significantly inferior to that by LSPI and SSPI,but superior to intact spine,after iliac struting in the anterior and mid column,SISPS can provide equal instant stability to MILPS.