Axial compressive strength of human thoracolumbar vertebrae - an experimental biomechanical study

Purpose: This study analyzed the correlation between the compressive streng th of human thoracolumbar vertebrae, bone density and endplate area (measur ed by SE-QCT). Method: The compressive strength of 110 human vertebral spec imens (D11-L5) was measured. In order to determine standard values for huma n vertebral specimens from each level and different female and male age gro ups were examined. Before biomechanical testing the specimens were examined using SE-QCT with 1.5 and 10 mm slice thickness. Three different slice loc ations (midvertebral and adjacent to both endplates) and 6 regions of inter est (ROI) were chosen to assess BMD. The area of the vertebral endplates wa s measured by CT. Results: Highest correlations between BMD and compressive strength were found for the 10 mm thick midvertebral slices with a small e llipsoid ROI. Cancellous and cortical bone contributed to the compressive s trength to the same amount. Compressive strength and endplate area increase d in the cranio-caudal direction, bone density was constant throughout thor acolumbar spine. Bone density and compressive strength depended on age and sex. Compressive strength of human thoracolumbar vertebrae increased with b one density as well as the size of the endplates. Conclusions: Using bone d ensity and endplate area (SE-QCT) of human thoracolumbar vertebrae (D11-L5) a prediction of compressive strength is possible with an error of estimati on of 1,17 kN and a correlation factor brf 0,85. The prediction of the comp ressive 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 togeth er with biomechanical examinations of vertebral metastases can be used to e stimate the compressive strength of osteolytic and osteoplastic spinal meta stases.