Lumbar spinal strains associated with whiplash injury: a cadaveric study.

OBJECTIVES To study and quantify the effects of rear-end collision on the lumbar spine. DESIGN The lumbar spine of a cadaver was instrumented with rosette strain gauges applied on the lateral and anterior surfaces of T12, L2, and L4. Biaxial accelerometers were mounted on L1, L3, and L5. The cadaver was seated, restrained, and subjected to rear impacts of 5g and 8g. RESULTS The anterior shear strains had a biphasic shape. Spinal strains peaked at the T12 at approximately 120 and 370 msec, whereas in the L4 vertebra, it peaked at 200 and 380 msec. The anterior strain pattern of the L4 and T12 vertebrae were in diametrically opposite directions. In the second set of tests (8g experiment), the acceleration forces and strains pattern were similar to the 5g test but of higher magnitude. The principal anterior strain was 480 microm/m for 5g and 530 microm/m for 8g; the lateral shear strain was 680 microm/m and 1500 microm/m in the 5g and 8g experiments, respectively. CONCLUSIONS Forces generated during simulated whiplash collision induce biphasic lumbar spinal motions (increased-decreased lordosis) of insufficient magnitude to cause bony injuries, but they may be sufficient to cause soft-tissue injuries.