TY - JOUR
T1 - A Comparison of the Torsional Stiffness of the Lumbar Spine in Flexion and Extension
AU - Garges, Kim J.
AU - Nourbakhsh, Ali
AU - Morris, Randall
AU - Yang, Jinping
AU - Mody, Milan
AU - Patterson, Rita
PY - 2008/10/1
Y1 - 2008/10/1
N2 - Objective: The main mechanism of injury to the spine is torsion especially when coupled with compression. In this study, the in vitro torsional stiffness of the lumbar spine segments is compared in flexion and extension positions by cyclic and failure testing. Methods: Fifteen lumbar spines were sectioned from fresh cadavers into 15 L2/3 and 15 L45 motion segments. Each vertebral segment was then potted superiorly and inferiorly in polymethylmethacrylate, effectively creating a bone-disk-bone construct. The potted spinal segments were mounted in a mechanical testing system, preloaded in compression to 300 N, and axially rotated to 3° in both directions at a load rate of 1°/s. This was done over 3 cycles for each motion segment in the flexion and extension positions. Each specimen was then tested to torsional failure in either flexion or extension. Stiffness, torque, and energy were determined from cyclic and failure testing. Results: The results showed that in all cases of cyclic testing, the higher segment extension resulted in higher torsional stiffness. In relative extension, the lumbar specimens were stiffer, generated higher torque values, and generally absorbed more energy than the relative flexion condition. There were no differences found in loading direction or failure testing. Conclusions: Increasing the effective torsional stiffness of the lumbar spine in extension could provide a protective mechanism against interverbral disk injury. Restoration of segmental extension through increasing the lumbar lordosis may decrease the strain and reinjury of the joints, which can help reduce the extent of pain in the lumbar spine.
AB - Objective: The main mechanism of injury to the spine is torsion especially when coupled with compression. In this study, the in vitro torsional stiffness of the lumbar spine segments is compared in flexion and extension positions by cyclic and failure testing. Methods: Fifteen lumbar spines were sectioned from fresh cadavers into 15 L2/3 and 15 L45 motion segments. Each vertebral segment was then potted superiorly and inferiorly in polymethylmethacrylate, effectively creating a bone-disk-bone construct. The potted spinal segments were mounted in a mechanical testing system, preloaded in compression to 300 N, and axially rotated to 3° in both directions at a load rate of 1°/s. This was done over 3 cycles for each motion segment in the flexion and extension positions. Each specimen was then tested to torsional failure in either flexion or extension. Stiffness, torque, and energy were determined from cyclic and failure testing. Results: The results showed that in all cases of cyclic testing, the higher segment extension resulted in higher torsional stiffness. In relative extension, the lumbar specimens were stiffer, generated higher torque values, and generally absorbed more energy than the relative flexion condition. There were no differences found in loading direction or failure testing. Conclusions: Increasing the effective torsional stiffness of the lumbar spine in extension could provide a protective mechanism against interverbral disk injury. Restoration of segmental extension through increasing the lumbar lordosis may decrease the strain and reinjury of the joints, which can help reduce the extent of pain in the lumbar spine.
KW - Lordosis
KW - Lumbar Region
KW - Torsion, Mechanical
UR - http://www.scopus.com/inward/record.url?scp=54549088874&partnerID=8YFLogxK
U2 - 10.1016/j.jmpt.2008.09.002
DO - 10.1016/j.jmpt.2008.09.002
M3 - Article
C2 - 18984238
AN - SCOPUS:54549088874
SN - 0161-4754
VL - 31
SP - 563
EP - 569
JO - Journal of Manipulative and Physiological Therapeutics
JF - Journal of Manipulative and Physiological Therapeutics
IS - 8
ER -