Impairment magnification during dynamic trunk motions

Study Design. An examination of a group of patients with low back disorder and a group of healthy (asymptomatic) individuals asked to produce trunk mo tions under sincere and insincere experimental conditions. Trunk motion com ponents were examined to determine which combination of motion components c ould best distinguish between sincere and insincere efforts. Objective. To determine whether examination of trunk motion components coul d be used to identify impairment magnification during unresisted repeated b ending tasks. Summary of Background Data. Trunk motion measures can be used to assess and "benchmark" the status of the low back. However, these measures typically are clinically useful only if the individual is producing an effort that do es not magnify the impairment during the functional evaluation. This study addressed the issue of impairment magnification during the production of fr ee dynamic trunk motion. Methods. The trunk motion characteristics of 100 healthy individuals and 10 0 patients with chronic low back disorders were documented. All participant s were asked to produce the trunk motions in two different types of conditi ons. In the one experimental condition, they were asked to produce sincere trunk motions. In the other experimental condition they were asked to prete nd either that they were experiencing low back pain (the asymptomatic group ) or that their pain was worse than it actually was (group with low back pa in). Results. A combination of trunk motion measures was able to distinguish wel l between the conditions. Sensitivity and specificity for the asymptomatic group were 92%, whereas they were 75% for the group with low back pain. Ove rall, sensitivity and specificity were 81.5% for all the participants combi ned. Conclusions. These results indicate that motion measures can be used to hel p assess impairment magnification during functional trunk motion testing. T hese measures can provide a means by which to scrutinize the quality of qua ntitative measures indicating the extent of a low back disorder. These obje ctive motion measures also can be used to complement other subjective obser vational methods for the assessment of impairment.