The hardness variations and characteristics of human lower lumbar vertebra by Vickers microindentation

English Keywords:Lumbar vertebrae  Micro-hardness  Microindentation technique  Biomechanics

English Abstract:

  【Abstract】 Objectives: To explore the variations and characteristics of micro-hardness of human lower lumbar vertebra. Methods: L3-L5 vertebrae were harvested from three fresh cadaver donors. The soft tissues were removed. According to the two-column theory of spine, each vertebra was divided into the vertebral body area and the attachment area. 4 specimens perpendicular to the upper and lower endplates were cut in the vertebral body area, meanwhile, 1 specimen parallel to the long axis of the vertebral pedicle and 1 specimen perpendicular to the superior and inferior articular process was cut in the attachment area by using a high-precision slow-speed saw. All specimens were sanded(Unit: HV). A total of 54 bone specimens was produced from 9 vertebrae(36 specimens in the vertebral body area and 18 specimens in the attachment area). The Vickers method was used to measure the micro-hardness of cortical bone and cancellous bone in different areas. The standard operation method of loading 50g for 50s and maintaining for 12s was choosen. Five effective hardness values were selected for each region, and the average value was taken as the hardness of the region. 11 regions were selected for each vertebra, and 495 effective indentations were performed. Results: The hardness range of the lower lumbar vertebra was 20.7-48.8 HV, with the average hardness of the cortical bone as 32.86±5.35 HV and the average hardness of the cancellous bone as 31.25±3.55 HV; the average hardness of the cortical bone in the vertebral body area as 32.11±5.17 HV, the average hardness of cortical bone in the attachment area as 33.46±5.43 HV; the average hardness of cancellous bone in the vertebral body area as 30.41±3.07 HV. The average hardness of cancellous bone in the attachment area as 32.10±3.83 HV. The hardness of cortical bone/cancellous bone in the attachment area was higher than that in the vertebral body area, and the difference was statistically significant(P＜0.05). L3-L5 different subjects had different bone hardness in the same region of the lumbar vertebra, but the changes among the regions were consistent with the whole. Conclusions: There are significant differences in the hardness from different regions of the lumbar vertebra. The hardness of the cortical bone and cancellous bone in the attachment area is higher than that of the cortical bone and cancellous bone in the vertebral body area.