Spine · 2011
Influence of interpersonal geometrical variation on spinal motion segment stiffness: implications for patient-specific modeling.
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Meijer Gerdine J M, Homminga Jasper, Veldhuizen Albert G, Verkerke Gijsbertus J
Аннотация
STUDY DESIGN: A validated finite element model of an L3-L4 motion segment is used to analyze the effects of interpersonal differences in geometry on spinal stiffness.
OBJECTIVE: The objective of this study is to determine which of the interpersonal variations of the geometry of the spine have a large effect on spinal stiffness. This will improve patient-specific modeling.
SUMMARY OF BACKGROUND DATA: The parameters that define the geometry of a motion segment are vertebral height, disc height, endplate width, endplate depth, spinous process length, transverse process width, nucleus size, lordosis angle, facet area, facet orientation, and the cross-sectional areas of the ligaments. All these parameters differ between patients. The influence of each parameter on spinal stiffness is largely unknown and such knowledge would greatly help in patient-specific modeling of the spine.
METHODS: The range of interpersonal variation of each of the geometric parameters was set at mean±2SD (covering 95% of the population). Subsequently, we determined the effect of each of these ranges on the bending stiffness in flexion, extension, axial rotation, and lateral bending.
RESULTS: Disc height had the largest influence; a maximal disc height reduced the spinal stiffness to 75-86% of the mean motion segment stiffness, and a minimal disc height increased the spinal stiffness to 154-226% of the mean motion segment stiffness. Lordosis angle, transversal and longitudinal facet angle, endplate depth, and area of the capsular ligament also had a substantial influence (>5%) on the stiffness, but considerable less than the influence of the disc height. Ligament areas, nucleus size, spinous process length, and length of processes are of negligible effect (<2%) on the stiffness.
CONCLUSION: The disc height should be accurately determined in patients to estimate the spinal stiffness. Ligament areas, nucleus size, spinous process length, and transverse process width do not need patient-specific modeling.
OBJECTIVE: The objective of this study is to determine which of the interpersonal variations of the geometry of the spine have a large effect on spinal stiffness. This will improve patient-specific modeling.
SUMMARY OF BACKGROUND DATA: The parameters that define the geometry of a motion segment are vertebral height, disc height, endplate width, endplate depth, spinous process length, transverse process width, nucleus size, lordosis angle, facet area, facet orientation, and the cross-sectional areas of the ligaments. All these parameters differ between patients. The influence of each parameter on spinal stiffness is largely unknown and such knowledge would greatly help in patient-specific modeling of the spine.
METHODS: The range of interpersonal variation of each of the geometric parameters was set at mean±2SD (covering 95% of the population). Subsequently, we determined the effect of each of these ranges on the bending stiffness in flexion, extension, axial rotation, and lateral bending.
RESULTS: Disc height had the largest influence; a maximal disc height reduced the spinal stiffness to 75-86% of the mean motion segment stiffness, and a minimal disc height increased the spinal stiffness to 154-226% of the mean motion segment stiffness. Lordosis angle, transversal and longitudinal facet angle, endplate depth, and area of the capsular ligament also had a substantial influence (>5%) on the stiffness, but considerable less than the influence of the disc height. Ligament areas, nucleus size, spinous process length, and length of processes are of negligible effect (<2%) on the stiffness.
CONCLUSION: The disc height should be accurately determined in patients to estimate the spinal stiffness. Ligament areas, nucleus size, spinous process length, and transverse process width do not need patient-specific modeling.