Biomechanical analysis of spinal reconstruction after total en bloc spondylectomy for lower lumbar spine / 中华骨科杂志

ABSTRACT

Objective To evaluate the mechanical stability of alternative reconstruction methods after total en bloc spon?dylectomy in the lower lumbar spine. Methods Eight adult fresh cadaveric lumbosacral spines (L1-S1) were adopted. Total en bloc spondylecotmy of the L4 vertebra was performed after intact testing. Four designed reconstruction samples were tested for the range of motion (ROM) of the spine1) expandable artificial vertebral body and short posterior instrumentation at L3-L5 (SP), 2) ex?pandable artificial vertebral body and short posterior instrumentation with additional anterolateral fixation at L 3-L5 (ASP), 3) ex?pandable artificial vertebral body and multilevel posterior instrumentation at L2-S1 (MP), 4) expandable artificial vertebral body and multilevel posterior instrumentation with additional anterolateral fixation at L2-S1 (AMP). Nondestructive biomechanical test?ing was performed on each construct under loading control. The ROM for each construct was obtained by applying pure moments in flexion, extension, lateral bending, and axial rotation. Results In flexion, extension and lateral bending, the ROM of all the re?constructed constructs significantly decreased compared to the intact. The ROM of specimens with anterolateral fixation was less when compared to the ones without additional fixation. In lateral bending, MP (L1.87° ± 0.32° , R1.97° ± 0.33° ), ASP (L1.89° ± 0.37°, R2.08°±0.36°) and AMP (L1.32°±0.29°, R1.61°±0.33°) provided significantly less ROM than the SP (L3.14°±0.35°, R3.44°±0.34°). In axial rotation, the ROM of ASP (L4.21°±0.58°, R4.02°±0.59°) and AMP (L3.56°±0.55°, R3.52°±0.48°) was significant decreased when compared to the intact state (L 7.47° ± 1.00° , R7.57° ± 0.84° ). MP (L6.33° ± 0.71° , R5.88° ± 0.62°), ASP and AMP showed significantly less ROM than the short posterior fixation (L9.28°±1.01°, R9.48°±0.98°). AMP sig?nificantly decreased the ROM compared to MP. Conclusion After total en bloc spondylectomy of lower lumbar, long segmental fixation provided more stability to the construct than the short one. Compared to posterior fixation, circumferential fixations showed a higher stability. In contrast, multilevel segmental instrumentation with circumferential fixation did not provided more stability than the short constructs.