Assessment of Lumbar Spine Height Following Sustained Lumbar Extension Posture: Comparison Between Musculoskeletal Ultrasonography and Stadiometry.

OBJECTIVES: The purpose of this study was to correlate sitting height measured by stadiometry with lumbar spine height (LSH) modifications measured by musculoskeletal ultrasonography (MSU). METHODS: Eighteen healthy young adults were recruited for this study (mean age: 21.5 ± 1.5 years). All subjects were tested in the following sequence: (1) lying supine for 10 minutes, (2) sitting under loaded (9.5 kg) and unloaded conditions for 5 minutes each, (3) lying supine for 15 minutes with passive lumbar extension, and (4) sitting unloaded for 5 minutes. Both stadiometry and MSU measurements were taken after each step of the testing sequence. RESULTS: Following the loaded sitting step, sitting height (measured by stadiometry) decreased by 3.4 ± 1.6 mm, whereas following sustained lumbar extension, sitting height increased by 5.4 ± 3.5 mm (P < .05). Following loaded sitting and sustained lumbar extension, LSH decreased by 3.8 ± 1.7 mm and increased by 6.2 ± 4.1 mm, respectively (P < .05). On the basis of the mean differences (between the different steps of the testing sequence), the mean correlation coefficient and the mean coefficient of determination between stadiometry and MSU measurements were calculated at 0.93 ± 0.07 and 0.88 ± 0.13, respectively, and no statistical differences were observed (P > .05). CONCLUSIONS: In vivo measurements of sitting height changes, measured using stadiometry, were strongly correlated with LSH changes, measured using ultrasonography.

Performance and reliability of a variable rate, force/displacement application system.

OBJECTIVE: Spinal manipulation therapy (SMT), an intervention used to treat low back pain, has been demonstrated to affect the stiffness of the spine. To adequately quantify the effects of SMT on stiffness, a device capable of applying specific parameters of manipulation in addition to measuring force-displacement values has been developed previously. Previously developed indentation techniques that quantify stiffness have been modified for novel use in evaluating SMT parameters. The reliability of stiffness measurements performed by the newly adapted device was assessed in this study. METHODS: Seven springs of varying stiffness were each indented 10 times by a variable rate force/displacement (VRFD) device. Indentations were performed at a rate of 0.5 mm/s to a maximal displacement of 4 mm. The stiffness coefficients for a middle portion of the resulting force-displacement graph and the terminal instantaneous stiffness (stiffness at end displacement) were calculated. The intraclass correlation and confidence interval were calculated for these stiffness measurements to assess device reliability. RESULTS: Repeated spring stiffness measures yielded an intraclass correlation coefficient value of 1.0. The mean stiffness values had narrow 95% confidence intervals ranging from 0.01 N/mm to 0.06 N/mm and small coefficients of variation. CONCLUSION: This VRFD device provides highly reliable stiffness measurements in controlled conditions. Although in vivo reliability remains to be established, the results of this study support the use of the VRFD device in future trials investigating the impact of various SMT parameters on spinal stiffness.

The reliability of a posterior-to-anterior spinal stiffness measuring system in a population of patients with low back pain.

OBJECTIVE: A system for measuring posterior-to-anterior spinal stiffness (PAS) was developed for use in clinical trials of manipulation for low back pain. The reliability of this device is under investigation in this study. METHODS: The PAS system uses electronic sensors to record displacement and force while a human operator provides the force of indentation. A test-retest design was used with measures repeated by the same operator within 5 minutes. Posterior-to-anterior loads were applied to each lumbar spinous process of patients lying prone on a hard flat bench. Force and displacement were recorded and used to calculate PAS. RESULTS: The subjects consisted of 22 males and 14 females; average age was 49.1 years (SD, 14.2). All subjects had low back pain of at least 4 weeks duration, with mean Roland-Morris scores of 7.6 (SD, 3.3). Spinal stiffness ranged from 4 to 26 N/mm (average, 11.2; SD, 3.5). Stiffness in the first and second tests varied on the average by 0.31 N/mm (P = .03). Standard error of the measurement was 1.62 N/mm. The single measures intraclass correlation coefficient (3,1) was 0.790 (95% confidence interval, 0.739-0.832). CONCLUSIONS: The equipment and method produced repeatable results over the short-term. The system may be sensitive enough to detect changes in spinal stiffness that occur with care.