Trunk Compliance Index a marker for chronic low back pain in young adults

The Trunk Compliance Index (TCI) in young individuals with chronic low back pain (cLBP) can detect consistent changes in trunk mechanics that may go unnoticed in classic clinic examinations, a recent study has found.

Researchers conducted a cross-sectional analysis of 49 young adults (mean age 23.0±5.4 years, 57 percent women) with cLBP. TCI was calculated from kinematic data obtained after perturbations applied to the trunk via actuator motors. Perturbations were applied over the six major axes of motion: extension, flexion, left- and right-side lateral flexion, and clockwise and anticlockwise rotation.

A parallel group of 49 healthy controls (mean age 22.8±5.7 years, 57 percent women) was also included.

Receiver operating characteristic (ROC) curve analysis showed that TCI, averaged across all perturbation conditions, showed excellent discriminatory capacity for chronic back pain (area under the curve [AUC], 0.898, 95 percent confidence interval [CI], 0.837–0.960). Sensitivity was high at 93.88 percent, while specificity was good at 73.47 percent.

The researchers also saw that lower TCI in five of the six perturbation directions drove a significant three-way interaction among the Direction of Perturbation, Sex, and Pain Condition variables in patients with cLBP (p=0.003).

Men and women with cLBP showed significantly lower TCI in the extension, flexion, leftward lateral flexion, and anticlockwise rotation perturbation directions.

“Lower levels in TCI were evident and preserved across perturbation movement directions in young individuals with mild to moderate chronic low back pain as compared to matched controls,” the researchers said.

“This signifies a potential global marker of trunk behaviour that is present despite limited influences of pain and disability on function,” they added.