Sensory processing and central pain modulation in patients with chronic shoulder pain

Chronicity and recurrence in musculoskeletal shoulder pain are highly prevalent and can possibly be attributed to the concept of central sensitization. Available studies suggest a role for central sensitization in explaining chronic shoulder pain, but so far a comprehensive quantitative sensory testing (QST) protocol has not been used. The aim of this study was to gain knowledge on sensory processing and central pain modulatory mechanisms in patients suffering from chronic shoulder pain using such a QST protocol. Fifty study participants, including chronic shoulder pain patients and healthy controls, underwent a standardized, comprehensive psychophysical testing procedure. A static adapted QST protocol (including pressure algometry, vibration and mechanical detection) was applied. Thereafter, all subjects underwent dynamic measures of temporal summation and conditioned pain modulation. Questionnaires assessing psychosocial factors were completed by each subject. No significant differences (P >= .05) were found between patients and controls based on pressure algometry, vibration detection, mechanical detection, temporal summation, and conditioned pain modulation. Moderate positive correlations (r = .5) were found between pressure pain thresholds (PPTs) and the amount of sports participation. Weak-to-moderate negative correlations (r = -.3 à -.5) were found between PPTs and psychosocial factors such as pain catastrophizing. Based on these findings, we can conclude that central sensitization is no characteristic feature in chronic musculo-skeletal shoulder pain but can be present in individual cases.