Impairment magnification during dynamic trunk motions

An examination of a group of patients with low back disorder and a group of healthy (asymptomatic) individuals asked to produce trunk motions under sincere and insincere experimental conditions. Trunk motion components were examined to determine which combination of motion components could best distinguish between sincere and insincere efforts. To determine whether examination of trunk motion components could be used to identify impairment magnification during unresisted repeated bending tasks. 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 does not magnify the impairment during the functional evaluation. This study addressed the issue of impairment magnification during the production of free dynamic trunk motion. The trunk motion characteristics of 100 healthy individuals and 100 patients with chronic low back disorders were documented. All participants were asked to produce the trunk motions in two different types of conditions. In the one experimental condition, they were asked to produce sincere trunk motions. In the other experimental condition they were asked to pretend 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 pain). A combination of trunk motion measures was able to distinguish well between the conditions. Sensitivity and specificity for the asymptomatic group were 92%, whereas they were 75% for the group with low back pain. Overall, sensitivity and specificity were 81.5% for all the participants combined. These results indicate that motion measures can be used to help assess impairment magnification during functional trunk motion testing. These measures can provide a means by which to scrutinize the quality of quantitative measures indicating the extent of a low back disorder. These objective motion measures also can be used to complement other subjective observational methods for the assessment of impairment.