Background/Purpose: Disabling distal upper limb pain is common but relatively understudied. Fear avoidance (FA) models of disability have been empirically tested for back and lower limb pain. There is a lack of research investigating their tenability for disabling distal upper limb pain. Given the region’s distinct functional demands, it is important to understand the role of psychosocial and behavioural factors in the pain-disability relationship. The aim of this study was to investigate whether any of five psychosocial or behavioural factors implicated in FA models mediated the distal upper limb pain-disability relationship: kinesiophobia, psychological distress, multiple somatic symptoms, beliefs about prognosis, change in physical activity, and change in leisure time arm use.

Methods: This observational study used data from a UK multi-centre randomized controlled trial to investigate mediators of the relationship between: 1.) Pain and disability at the time of referral; 2.) Baseline pain, and disability 26wks later. Patients referred to physiotherapy with distal upper limb pain/disability completed self-report questionnaires at baseline, 6, 13 and 26wks. Information was collected on pain intensity (11-point Numeric Rating Scale), disability (modified Disabilities of the Arm, Shoulder and Hand questionnaire), kinesiophobia (Tampa Scale for Kinesiophobia), quality of life (EQ-5D), somatic symptoms (Modified Somatic Perception questionnaire), beliefs about prognosis, physical activity and leisure time arm use. Mediation analysis included use of Baron and Kenny criteria, Sobel tests, and, for longitudinal models, analysis of covariance using data collected at three follow-up time points (baseline, 26 weeks and either 6 or 13 weeks). Models were adjusted for age, gender, diagnostic category, pain duration and history, and trial treatment group: (a) immediate physiotherapy; or normally timed physiotherapy, with (b) advice to rest; or (c) advice to remain active during a six-to-seven week waiting period. Sensitivity analyses used multiple imputation by chained equations to assess for bias due to missing data.

Results: 538 participants (54% female; mean age 49yrs, SD 14) provided data. The relationship between pain and disability at time of physiotherapy referral was partially mediated by kinesiophobia, which explained 12.6% of the total effect of pain on disability (95%CI 5.3-16.8%). Longitudinally, there was evidence that development of prognostic pessimism over the initial treatment period partially mediated the relationship between pain at time of referral and disability 26wks later (14.2% of the total effect, 95%CI 0.04%-23.4%). Sensitivity analyses using multiple imputation made only minor differences to the results, and no difference to their interpretation.

Conclusion: We have demonstrated that kinesiophobia and prognostic pessimism partially mediated the distal upper limb pain-disability relationship. While psychological distress and activity avoidance have been found to mediate the relationship in back and lower limb pain, they were not identified in this population. This would suggest that cognitive constructs may be more important treatment targets for distal upper limb pain.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/mediators-of-the-relationship-between-pain-and-disability-in-the-distal-upper-limb/