[The effect of bending and rotation on the lumbar facet joints under load-bearing conditions].
OBJECTIVE
To evaluate the effect of bending and rotation on the lumbar facet joints under load-bearing conditions.


METHODS
Eight lumbar-sacral spines (L1-S1) taken from fresh young adult cadavers were placed on the MTS system. The forces of the two facet joints of the L4-5 motion segments were measured using pressure sensitive films. The specimens were measured in erection, bending and rotation postures.


RESULTS
In erection posture the L4-5 facet joints could support 31.16+/-7.15 N of 400 N which was axial compressing load. In bending 15 degree posture the forces of each side of the L4-5 facet joints were equal, and were found to have no marked effect on the force in erection. Yeat only opposite facet joints could endure force in rotation, but the force was 7 times that in erection.


CONCLUSIONS
Both sides of lumbar facet joints could support load in bending position but only the opposite could endure load in rotation.
Xiao
Jin
J
Department of Orthepaedics, 157 Central Hospital of PLA, Guangzhou 510510, China. xiaojinhn@yahoo.com.cn
Yuan
Lin
L
Zhao
Wei-dong
WD
Fan
Ji-hong
JH
Qiu
Jie
J
Zhong
Shi-zhen
SZ
D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D008159:Lumbar Vertebrae; D012399:Rotation; D016474:Weight-Bearing; D021801:Zygapophyseal Joint