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Lower Limb Positioning Impacts Lordosis, Kyphosis

Finite element model simulations show decrease in lordosis, kyphosis with increased hip flexion

MONDAY, April 23 (HealthDay News) -- An individual's lordosis and kyphosis can both be changed by lower limb positioning, according to a study published in the April issue of the Journal of Spinal Disorders & Techniques.

Christopher Driscoll, Ph.D., from the École Polytechnique de Montréal, and colleagues conducted finite element model (FEM) simulations and experimental testing in four volunteers to investigate the association between lower limb positioning for surgeries of the spine and changes in sagittal curves. Personalized FEMs were created and exploited to examine the influence of more extreme and intermediate lower limb positions.

With increased hip flexion, the researchers found that lordosis decreased to an average of 52 percent (35 degrees) and kyphosis to an average of 16 percent (6 degrees). FEM personalization facilitated reproduction of the experimental results within 5 degrees. Subsequent exploitation of the FEMs showed that with increased hip flexion the linear changes in lordosis and kyphosis between extreme positions decreased an average of 84 percent (59 degrees) and 34 percent (13 degrees), respectively. Experimental changes in lordosis were strongly associated with individual hamstring flexibilities. This allowed for the development of a predictive equation for lordosis in terms of hip flexion.

"A FEM has been developed which allows for study of the impact of subject-specific lower limb positioning on lumbar lordosis and thoracic kyphosis both of which can be significantly modulated on the Multi-functional Positioning Frame," the authors write. "The primary factor influencing sagittal curve changes owing to lower limb positioning is hamstring flexibility."

The study was funded by the Natural Sciences and Engineering Research Council of Canada (Industrial Research Chair with Medtronic of Canada).

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