The role of spinal tissues in resisting posteroanterior forces applied to the lumbar spine

Abstract

Objective: To determine the effects of the dissection of spinal tissues on the mechanical behavior of motion segments under the application of posteroanterior forces.

Design: A cadaveric motion segment study.

Setting: A tissue mechanics research laboratory.

Procedure: Anterior shear and extension moment were applied to 10 motion segments to simulate the clinical situation when posteroanterior forces were applied to the spine. The movements of the specimens in the sagittal plane were studied by a camera. Spinal tissues were dissected sequentially, and the mechanical testing was repeated after the dissection of each tissue.

Results: The most significant movements produced were extension and superior translation of the anteroinferior corner of the superior vertebral body. Translational movements in the other directions were small. The dissection of the posterior ligaments and zygapophyseal joints did not lead to significant changes in the movements.

Conclusions: Injuries of the posterior ligaments are unlikely to alter the mechanical response of the spine to posteroanterior forces. However, these posterior tissues are pain sensitive and may be subjected to large strains and elicit symptoms.