Understanding the relationship between features associated with pain-related disability in people with painful temporomandibular disorder: an exploratory structural equation modeling approach

Pain-related disability is a multifaceted construct that refers to the impact of pain on an individual's capacity to fulfill their self-defined and social roles. This research examined the relationship between clinical, psychological, and pain sensitivity factors and pain-related disability among adults with chronic temporomandibular disorder (TMD). We analyzed data from a cross-sectional community-based sample of 1088 men and women with chronic TMD. We first constructed and tested a measure of pain-related disability (ie, pain impact), including a variable assessing presenteeism, created measurement models of jaw limitation, psychological unease (negative affect, somatic symptoms, and catastrophizing), and experimental pain sensitivity (eg, pressure pain threshold, thermal tolerance, and mechanical pressure pain threshold). Subsequently, latent variables were combined in a structural equation model. Participants (n = 1088) were 18 to 44 years old (mean 29.2, SD +/- 7.8) whose chronic TMD had persisted, on average, for 6.9 years (SD +/- 6.4). A model of pain-related disability, jaw limitation, and psychological unease was created and refined with exploratory model revisions to account for correlation among variables. Estimation of the final model indicated excellent fit with the data (root-mean-square error of approximation = 0.048, root-mean-square error of approximation 90% confidence interval [CI] 0.043-0.053, comparative fit index = 0.956, standardized root-mean-square residual = 0.040). Jaw functional limitation and psychological unease was strongly related to pain-related disability. Experimental pain sensitivity was removed from our model because of weak direct effect and the burden of performing experimental pain sensitivity testing in a clinical setting. The final model explained 78% of the variance in pain-related disability.