Fear of movement interacts with trunk mobility, and pain intensity to predict disability in patients with chronic low back pain: a classification and regression tree (CART) analysis

Background: Low back pain significantly impacts global health, particularly in low-income areas where primary care challenges are prevalent. Assessing both biophysical and psychological factors associated with low back pain-related disability is crucial for developing effective screening and management strategies. ObjectivesThis study aimed to examine the association between fear of movement, trunk mobility, pain intensity, physical activity, and low back pain-related disability, and to identify key factors contributing to higher disability levels in patients with chronic low back pain. Methods: This cross-sectional study analyzed data from 381 chronic low back pain patients aged over 18, collected at a primary care ambulatory between 2015 and 2019. Variables measured included pain intensity, fear of movement, physical activity, trunk mobility, and disability. A Classification and Regression Tree approach was used to model disability predictors. Results: Fear of movement was the main driver of high disability (OR = 17.3, 95%CI 8.9-33.7). Two profiles were particularly prone to higher disability: patients with high fear of movement (>47.5) and pain intensity > 1.5; and those with lower fear of movement but poor trunk mobility (>36.5 cm). Patients with better trunk mobility and low pain intensity (<= 3.5) showed significantly less disability (OR = 0.06, 95%CI 0.02-0.17). Conclusions: The findings highlight the need for integrating better psychological and biophysical assessments in managing chronic low back pain. Understanding how fear of movement, trunk mobility, and pain interaction can improve screening accuracy and optimize care in resource-limited settings, using valid and feasible tools for these scenarios.