Perception of verticality is altered in people with severe chronic low back pain compared to healthy controls: A cross-sectional study.

Background: People with chronic low back pain (CLBP) have abnormal lumbar proprioception, which increases their reliance on visual input to maintain body verticality. Maintaining verticality is important for spatial orientation, balance and movement coordination. It is unknown if these patients also have altered perception of verticality.

Objective: To compare whether the perception of verticality is different between people with and without CLBP.

Design: Cross-sectional.

Methods: Two comparisons of perception of verticality were done between a group of people with CLBP (n = 25) and healthy people (n = 25); and between a subgroup of people with severe CLBP (n = 14) and healthy people (n = 25). In a dark room, the subjective visual vertical test was performed under 3 conditions: rod, rod-and-frame, and rod-and-disc. In each condition, the rod was tilted 40° clockwise and counterclockwise, and the participants were asked to bring it back to vertical 0° position. The rod deviation from verticality was recorded in degrees.

Results: When considering the CLBP group, analysis of variance showed that deviation from verticality had no significant group interaction with condition (p = 0.2), or group main effect (p = 0.2). However, deviation from verticality was significantly different between the conditions (p < 0.001). When considering the severe CLBP subgroup, the interaction effect was significant (p = 0.046). Simple main effects showed that the severe CLBP subgroup had larger deviations from verticality (7.5 ± 0.9 deg) compared to the healthy group (4.2 ± 0.7 deg) specifically on the rod-and-frame condition (p = 0.007).

Conclusion: People with severe CLBP appear to have larger deviations in judging verticality compared to the healthy group.