Abstract
PurposeTo investigate (1) effects of endplate removal and bone mineral density (BMD) on biomechanical properties of lumbar vertebrae (2) whether the distributions of mechanical strength and stiffness of endplate are affected by BMD.MethodsA total of thirty-one lumbar spines (L1-L5) collected from fresh cadavers were used in this study. Bone density was measured using lateral DEXA scans and parts of samples were performed with partial or entire endplate removal. All the specimens were divided into three BMD groups. According to endplate integrity of the lumbar vertebrae, each BMD group was then divided into three subgroups: subgroup A: intact endplate; subgroup B: central region of endplate removal; subgroup C: entire endplate removal. The axial compression test was conducted with material testing system at a speed of 2mm/min. The experimental results were statistically analyzed using SPSS 17.0.Results(1) Significant differences of biomechanical properties occurred among normal BMD, osteoporotic and serious osteoporotic group (P<0.05). (2) Spearman analysis showed that BMD was positively correlated with the failure load and stiffness of lumbar vertebrae. (3) For each BMD group, significant differences of biomechanical properties were found between subgroup A and C, and between subgroup B and C (P<0.05). (4) For each BMD group, there was no statistical difference of biomechanical properties between subgroup A and B (P>0.05).ConclusionsEntire endplate removal can significantly decrease the structural properties of lumbar vertebrae with little change in biomechanical properties by preservation of peripheral region of the endplate. BMD is positively correlated to the structural properties of the lumbar vertebrae.
Highlights
During the interbody fusion, structural struts such as prosthetic devices, autografts and allografts are implanted between two adjacent vertebrae to provide structural support following removal of diseased or damaged tissue from the spinal column [1]
For the lumbar vertebrae with intact endplate, the analysis of variance showed that differences of the failure load and stiffness in three bone mineral density (BMD) groups were statistically significant (P
Stiffness was found to be positively correlated to BMD in lumbar vertebrae with partial endplate removal and entire endplate removal, respectively
Summary
Structural struts such as prosthetic devices, autografts and allografts are implanted between two adjacent vertebrae to provide structural support following removal of diseased or damaged tissue from the spinal column [1]. A common feature of all these interbody implants is that they rely on the vertebral bodies for support. Settling or subsidence of these struts into the vertebral body can be a significant complication resulting in deformity, compromise of neural elements, and unfavorable biology leading to nonunion [2,3]. The graft–endplate interface must have sufficient strength, which is determined by bone mineral density (BMD) and contact area, to resist the large in vivo loading [1]. Modifying implants to engage the stronger regions of endplates may significantly reduce subsidence incidence. Our results showed that the peripheral area of lumbar endplate was stronger than the central area and the strongest region was the posterolateral area in front of the pedicles. There was an increasing tendency in compressive strength of lumbar endplate from L1 to L5 and BMD was positively correlated with strength of lumbar endplates
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