Biomechanical comparison of lumbar spine with or without spina bifida occulta. A finite element analysis.
METHODS
Biomechanical study using finite element model (FEM) of lumbar spine.


OBJECTIVE
Very high coincidence of spina bifida occulta (SBO) has been reported more than in 60% of lumbar spondylolysis. The altered biomechanics due to SBO is one considerable factor for this coincidence. Thus, in this study, the biomechanical changes in the lumbar spine due to the presence of SBO were evaluated.


METHODS
United States of America (USA).


METHODS
An experimentally validated three-dimensional nonlinear FEM of the intact ligamentous L3-S1 segment was used and modified to simulate two kinds of SBO at L5. One model had SBO with no change in the length of the spinous process and the other had a small dysplastic spinous process. Von Mises stresses at pars interarticularis were analyzed in the six degrees of lumbar motion with 400 N axial compression, which simulates the standing position. The range of motion at L4/5 and L5/S1 were also calculated.


RESULTS
It was observed that the stresses in all the models were similar, and there was no change in the highest stress value when compared to the intact model. The range of motion was also similar in all the models. The lumbar kinematics of SBO was thus shown to be similar to the intact model.


CONCLUSIONS
SBO does not alter lumbar biomechanics with respect to stress and range of motion. The high coincidence of spondylolysis in spines with SBO may not be due to the mechanical factors.
Sairyo
K
K
Department of Bioengineering, Spine Research Center, University of Toledo, Toledo, OH 43606, USA.
Goel
V K
VK
Vadapalli
S
S
Vishnubhotla
S L
SL
Biyani
A
A
Ebraheim
N
N
Terai
T
T
Sakai
T
T
D001696:Biomechanical Phenomena / Q000379:methods; D019245:Compressive Strength; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D008159:Lumbar Vertebrae / Q000002:abnormalities* / Q000503:physiopathology*; D008954:Models, Biological; D012447:Sacrum / Q000503:physiopathology*; D016136:Spina Bifida Occulta / Q000503:physiopathology*; D013169:Spondylolysis / Q000503:physiopathology*; D013314:Stress, Mechanical; D013718:Tensile Strength; D016474:Weight-Bearing