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Posteroanterior stiffness in the lumbosacral spine. The correlation between adjacent vertebral levels
1School of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, Australia.
Study Design:
A descriptive design of posteroanterior stiffness in the lumbosacral spine.
Objectives:
To measure posteroanterior stiffness between L1 and S1 to establish the pattern of stiffness in individuals with no history of low back pain.
Summary Of Background Data:
In clinical examination for low back pain, manual assessment of abnormal stiffness is used to determine the site of the pain-producing lesion. However, there is little objective evidence of the variation in stiffness between levels in normal spines or of the factors that determine posteroanterior stiffness.
Method:
Posteroanterior stiffness was measured with a specially developed measuring device at each of the six vertebral levels between L1 and S1. Force-displacement relations were computed for each vertebral level. The gradient of the linear part of the force-displacement relation was used as a coefficient of stiffness, and the amount of displacement between 5 N and 30 N of applied force (D5-30) was used as a measure of the length of the toe region.
Results:
Overall there was a significant linear trend of increasing stiffness from L1 to S1. Ninety percent of the difference scores for adjacent level comparisons were less than 3.6 N/mm. There was considerable variation in the patterns of stiffness found in different individuals. The stiffness coefficient and D5-30 correlated significantly with skinfold thickness measurements and body mass index.
Conclusion:
A linear trend of increasing stiffness was found between L1 and S1, but this pattern was influenced by variables related to body type (adiposity).