Lumbar Range of Motion: Reliability and Validity of the Inclinometer Technique in the Clinical Measurement of Trunk Flexibility

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Abstract
This study examines the reliability and validity of measuring lumbar range of motion with an inclinometer. To find out whether a manual determination of the reference points for measuring lumbar range of motion is as reliable as radiologic determination for positioning the inclinometers, lumbar range of motion was determined in degrees by evaluating radiographs and by using the inclinometer technique of Loebl. Reliability and validity of the inclinometer technique as a clinical measurement of trunk flexibility were investigated. Fifty-four patients participated in the study. Lumbar range of motion measurements were taken with and without radiologic control of the T12 and S1 vertebrae as reference points for positioning of the inclinometers. An interrater correlation was done of the inclinometer techniques of a physician and a physiotherapist. Functional radiographs were investigated in a standing position. Lumbar range of motion measurements based on radiographs and those taken using the inclinometer alone were correlated to validate the inclinometer technique. Lumbar range of motion measurements taken with and without radiologic determination showed a very close correlation (r = 0.93; P < 0.001). Flexion alone also demonstrated a close correlation (r = 0.95; P < 0.001), whereas extension showed a somewhat smaller correlation (r = 0.82; P < 0.001). Total lumbar range of motion (r = 0.94; P < 0.001) and flexion (r = 0.88; P < 0.001) were closely related, as indicated by the interrater correlation, whereas extension (r = 0.42; P < 0.05) showed a lesser correlation. Correlation of the measurements taken radiographically and by inclinometer demonstrated an almost linear correlation for measurements of the total lumbar range of motion (r = 0.97; P < 0.001) and flexion (r = 0.98; P < 0.001), whereas extension (r = 0.75; P < 0.001) did not correlate as well. The noninvasive inclinometer technique proved to be highly reliable and valid, but the measurement technique for extension needs further refinement.