Effects of spondylolysis on mechanical stability of upper lumbar vertebrae / 医用生物力学

ABSTRACT

Objective To study the stability of upper lumbar vertebra in spondylolysis by measuring the upper vertebra pressure on lumbar spondylolysis models. Method Nine fresh frozen human lumbar spinal specimens were used as experimental models. The pressure on upper vertebral discs of lumbar vertebrae was measured by the material testing machine (MTS 858 Bionix test system)with extension, flexion and axial, bilateral compression being applied on two groups of specimens 1) intact spine; 2) lumbar spondylolysis. Results Compared with the intact specimens, the pressure of upper lumbar vertebra in spondylolysis was increased by 1.3％，1.5％，1.7％ in axial compression with 600, 800, 1 000 N (the differences were not significant (P＞0.05)), by 20.97％，24.45％，28.79％ in 15°of extension with 300, 500, 700N (the differences were significant (P < 0.01)), by 14.15％，17.86％，24.92％ in 15°of flexion with 300, 500, 700N (the differences were significant (P < 0.01)), by 3.54％，2.12％，1.14％ in 15°of bilateral compression with 300, 500, 700N (the differences were not significant (P＞0.05)). Conclusions Lumbar spondylolysis has a significant mechanical influence on lumbar spine not only at the involved level but also at the upper adjacent level, which can affect the stability of lumbar spine correspondingly.