Reliability of the American Medical Association Guides' model for measuring spinal range of motion - Its implication for whole-person impairment rating

Study Design. Repeated measures design for intra- and interrater reliabilit y. Objectives. To determine the intra- and interrater reliability of the lumba r spine range of motion measured with a dual inclinometer, and the thoracol umbar spine range of motion measured with a long-arm goniometer, as recomme nded in the American Medical Association Guides. Summary of Background Data. The American Medical Association Guides (2nd an d 4th editions) recommend using measurements of thoracolumbar and lumbar ra nge of movement, respectively, to estimate the percentage of permanent Impa irment in patients with chronic low back pain. However, the reliability of this method of estimating impairment has not been determined. Methods. In all, 34 subjects participated in the study, 21 women with a mea n age of 40.1 years (SD, +/- 11.1) and 13 men with a mean age of 47.7 years (SD, +/- 12.1). Measures of thoracolumbar flexion, extension, lateral flex ion, and rotation were obtained with a long-arm goniometer. Lumbar flexion, extension, and lateral flexion were measured with a dual inclinometer. Mea surements were taken by two examiners on one occasion and by one examiner o n two occasions approximately 1 week apart. Results. The results showed poor intra- and interrater reliability for all measurements taken with both instruments. Measurement error expressed in de grees showed that measurements taken by different raters exhibited systemat ic as well as random differences. As a result, subjects measured by two dif ferent examiners on the same day, with either instrument, could give impair ment ratings ranging between 0% and 18% of the whole person (excluding rota tion), in which percentage impairment is calculated using the average range of motion and the average systematic and random error in degrees for the 1 group-for each movement (flexion, extension, and lateral flexion). Conclusions. The poor reliability of the American Medical Association Guide s' spinal range of motion model can result in marked variation in the perce ntage of whole-body impairment. These findings have implications for compen sation bodies in Australia and other countries that use the American Medica l Association Guides' procedure to estimate impairment in chronic low back pain patients.