Latimer, J, Holland, M, Lee, M & Adams, R 1997, 'Plinth padding and measures of posteroanterior lumbar stiffness.', J Manipulative Physiol Ther, vol. 20, no. 5, pp. 315-319.
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OBJECTIVE: To investigate whether measurement of posteroanterior (PA) lumbar stiffness is affected by the presence of padding on the testing plinth. DESIGN: Within a repeated-measures design, measurements were made of lumbar PA stiffness in subjects without low back pain on both a rigid and a padded plinth surface. SUBJECTS: Nineteen subjects with no history of any low back pain requiring treatment over the preceding 12 months participated in this study. METHODS: PA stiffness was measured at L3 on two occasions under two different conditions. The first condition involved measurement of lumbar stiffness on a rigid plinth surface; the second involved measurement on a padded plinth surface. A reliable mechanical device was used to obtain the PA stiffness measures. RESULTS: Mean lumbar PA stiffness values obtained when testing on a padded plinth were 2.86 N/mm less than those values obtained when testing the same lumbar spines on a rigid plinth. A paired t test showed a significant difference between the PA stiffness measures at L3 obtained on the padded plinth and those obtained on the rigid plinth (t = 6.66, df = 18, p < or = .0001). CONCLUSIONS: These findings suggest that to improve the reliability of lumbar PA stiffness assessment, testing should be performed under the same plinth surface conditions.
Lee, M, Latimer, J & Maher, C 1997, 'Normal response to large posteroanterior lumbar loads--a case study approach.', J Manipulative Physiol Ther, vol. 20, no. 6, pp. 369-371.
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OBJECTIVE: Characterization of the responses to spinal posteroanterior loading has involved measuring the gradient of the linear region of the force-displacement relationship between 30 N and 100 N of applied force. However, forces applied during manual assessment of stiffness may reach 300 N. This study investigated whether the force-displacement relation remains linear above 100 N. DESIGN: A single-case-study design with replication was used. SUBJECTS: Two male subjects, with no history of low back pain requiring treatment over the preceding twelve months, participated in this study. METHODS: Posteroanterior loads of 275 N were applied to the 1.3 vertebra of both subjects using a mechanical device. The force-displacement responses in these subjects were measured and analyzed to examine the linearity of the data. RESULTS: The responses from the two subjects were similar. In both cases, the responses were approximately linear at all levels of load up to 275 N. Because of the small degree of nonlinearity, there was a tendency for the stiffness to show moderate increases as the load increased. Stiffness was approximately 25% greater when calculated between 30 N and 275 N than when calculated between 30 N and 100 N. CONCLUSION: In these two subjects, the force-displacement relation was approximately linear for all three force intervals considered, although there was some increasing stiffness with increasing force.
Viner, A, Lee, M & Adams, R 1997, 'Posteroanterior Stiffness in the Lumbosacral Spine', Spine, vol. 22, no. 23, pp. 2724-2729.
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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).
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