[Axial compressive strength of thoraco-lumbar vertebrae--an experimental biomechanical study]

This study analyzed the correlation between the compressive strength of human thoracolumbar vertebrae, bone density and endplate area (measured by SE-QCT).

The compressive strength of 110 human vertebral specimens (D11-L5) was measured. In order to determine standard values for human vertebral specimens from each level and different female and male age groups were examined. Before biomechanical testing the specimens were examined using SE-QCT with 1.5 and 10 mm slice thickness. Three different slice locations (mid-vertebral and adjacent to both endplates) and 6 regions of interest (ROI) were chosen to assess BMD. The area of the vertebral endplates was measured by CT.

Highest correlations between BMD and compressive strength were found for the 10 mm thick midvertebral slices with a small ellipsoid ROI. Cancellous and cortical bone contributed to the compressive strength to the same amount. Compressive strength and endplate area increased in the cranio-caudal direction, bone density was constant throughout thoracolumbar spine. Bone density and compressive strength depended on age and sex. Compressive strength of human thoracolumbar vertebrae increased with bone density as well as the size of the endplates.

Using bone density and endplate area (SE-QCT) of human thoracolumbar vertebrae (D11-L5) a prediction of compressive strength is possible with an error of estimation of 1.17 kN and a correlation factor of 0.85. The prediction of the compressive strength allows an estimation of the risk of vertebral fracture, i.e. in patients with osteoporosis or in individuals with intensive physical activities. The standard values of the human thoracolumbar vertebrae together with biomechanical examinations of vertebral metastases can be used to estimate the compressive strength of osteolytic and osteoplastic spinal metastases.