Lumbar spine range of motion as a measure of physical and functional impairment: an investigation of validity.

OBJECTIVE: To investigate the validity of the spinal range of motion models outlined in the second and fourth editions of the American Medical Association Guides to the evaluation of permanent impairment (AMA Guides), for assessing the percentage impairment in chronic low back pain patients.

DESIGN: Cross-sectional validation study.

SETTING: Outpatient department in the Rehabilitation Medicine Unit.

SUBJECTS: A volunteer sample of 34 subjects participated in the study, 21 females and 13 males, with a mean age of 47.7 years (1 SD = 12.1) and 40.1 years (1 SD = 11.1), respectively. Subjects had chronic low back with or without leg pain of at least six months' duration. Subjects were recruited by medical practitioners and physiotherapists through the Rehabilitation Unit at the Essendon Campus of Royal Melbourne Hospital.

MAIN OUTCOME MEASURES: Lower back range of motion measured with a long arm goniometer and a dual inclinometer, Waddell Physical Impairment Scale, Waddell Disability Index, Oswestry Disability Index.

RESULTS: Both range of motion measurement methods demonstrated poor validity and do not bear any consistent relationship to the level of physical or functional impairment in subjects with chronic low back pain.

CONCLUSIONS: There was no evidence for a relationship between low back range of motion and impairment, and thus it would appear illogical to evaluate impairment in chronic low back pain patients using a spinal range of motion model when aiming to measure or compensate disability.