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In-Depth Information
(a)
Posterior Bony Elements
Vertebral Body
Intervertebral Disc
Spinal Ligaments
(b)
4.5
4
3.5
3
2.5
2
0
500
1000
1500
2000
2500
3000
3500
Time (sec)
FIGURE 35.6
Finite element analysis: (a) three-dimensional FEA model of a L3
L4 motion segment; (b) predicted
/
creep response of sagittal flexion angle during 1 h static moment loading.
The FEA model can simulate prolonged stooping and recovery, and the results (deformation and stress of
passive tissues) can be used to estimate the changes in lumbar spinal stability and micro-damage as a
function of time and posture. In the final assessment model the user would input the duty cycle charac-
teristics of the alternating stooping and upright postures as well as the trunk flexion angles assumed
during the stooping phase and the output would be a measure of the changes in a spinal stability
index and predicted degrees of micro-damage occurring in the passive tissues.
References
Adams, M. and Dolan, P. (1995). Recent advances in lumbar spinal mechanics and their clinical signifi-
cance, Clinical Biomechanics, 10(1):3-19.
Chaffin, D. (1974). Human strength capability and low-back pain, Journal of Occupational Medicine,
16:248-254.
Chaffin, D. and Park, K. (1973). A longitudinal study of low-back pain as associated with occupational
weight lifting factors, American Industrial Hygiene Association Journal, 34:513-524.
Cholewicki, J. and McGill, S. (1996). Mechanical stability of the in vivo lumbar spine: implications for
injury and chronic low back pain, Clinical Biomechanics, 11:1-15.
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