Euler stability of the human ligamentous lumbar spine. Part II: Experiment.

The lateral backing and postbuckling behaviour of the intact and injured whole human lumbar spine was experimentally studied using six fresh cadaveric specimens. The ligamentous lumbar spine was loaded in axial compression and the lateral rotation of each vertebra was recorded. At the point of the load application, the most superior vertebrae, the specimens were constrained to move in the frontal plane since sagittal plane buckling will not occur due to the lumbar lordosis. The average load required to buckle an intact whole lumbar specimen was 88 N, and significantly decreased with injury. Once the spines had buckled, the postbuckling behaviour was recorded. These results were compared to theoretical predictions of a model (see Part I). The model was demonstrated to be in excellent agreement with the experimental results.