Abstract:

BACKGROUND: Lumbar fusion has been widely used in treating lumbar diseases. However, the influence on adjacent segments is on debate, and the stability of fused segment and biomechanical effects on adjacent segments have not been well document.
OBJECTIVE: To study the biomechanical properties of fused segments and adjacent segments.
METHODS: New Zealand White rabbits were randomly assigned into anterior lumbar interbody fusion (ALIF) group (L5-6 discectomy, decortication of the vertebral end plates, autogeneuous iliac bone graft were performed), posterolateral fusion (PLF) group (autogeneuous iliac crest bone graft was placed over the bilateral decorticated L5-6 transverse processes), 360° fusion group (underwent ALIF firstly, and PLF L5-6 were performed after 1 week), or control group (treated without any operation). The spinal fusion was analyzed by radiography, manual palpation and mechanical testing at 12 weeks after operation. Each successful fusion specimen was tested in six pure moments (flexion and extension, left and right lateral bending, left and right axial rotation) to determine the stability of fused segments and the range of motion (ROM) of adjacent segments.
RESULTS AND CONCLUSION: Compared with the control group, the ROM of flexion at L5-6 segment decreased significantly 86.24% (P < 0.05), 88.74% (P < 0.05), 73.10% (P < 0.05) for the ALIF group, 360° fusion group and PLF group, respectively. Accordingly, the ROM of flexion at L4-5 increased 52.22% (P < 0.05), 55.89% (P < 0.05), and 27.11% (P < 0.05). Three lumbar fusion methods can enhance the stability of fused segment significantly. The stability of 360° fusion is the highest, and that of PLF is the least. The ROM of flexion at proximal adjacent segment in ALIF and 360° fusion is no statistical difference, and that of the PLF is the least.