J Manipulative Physiol Ther. 1994 Oct; 17(8): 530-8.

Optoelectric measurement of changes in leg length inequality resulting from isolation tests.

De Witt JK, Osterbauer PJ, Stelmach GE, Fuhr AW.

Exercise and Sport Research Institute, Arizona State University, Tempe 85287-0404.

OBJECTIVE: a) Establish a precise, standardized method to assess prone leg alignment changes (functional "leg length inequality"), which have, until now, been reported clinically to occur as a result putative chiropractic subluxation isolation tests [neck flexion (C5) and extension (C1)]; and b) describe differences in leg alignment changes in a group of healthy subjects and patients with chronic spinal complaints. DESIGN: Two group, two isolation tests, descriptive, repeated measure analysis of variance. SETTING: Exercise and Sport Research Institute, Arizona State University. PARTICIPANTS: Eight healthy controls, eight patients with a history of chronic spinal complaints and observable leg alignment reactivity. INTERVENTIONS: Active cervical flexion/extension maneuvers. OUTCOME MEASURES: Optoelectric markers affixed to heels and occiput, as subjects lay prone. Marker locations sampled at 100 Hz for 10 sec during: a) three no movement trials, b) three cervical extension and c) three flexion trials. Data transformed to local reference frame approximately each subject's longitudinal axis prior to analysis. RESULTS: Heel position movement occurred during trials and were highly individualistic. Patients exhibited more asymmetrical movements than the controls during the head-up trials. No differences existed between controls and patients for range of heel displacement or net displacement. CONCLUSIONS: The results of this study allow the following to be concluded: 1) small leg displacements (< 1 mm) were recorded by the optoelectric measurement system; 2) heel position changes during isolation tests were identifiable; 3) as a result of head-up maneuvers, patients exhibited more asymmetrical heel movement than controls (t = 8.743, p < .01); 4) The heel range of motion was not different between the groups; and 5) The net change in heel position was not different between the groups. Patients exhibited more asymmetrical heel motion during head-up isolation tests, suggesting that some phenomena may separate these two groups, warranting future study.