Are clinical outcomes of frozen shoulder linked to pain, structural factors or pain-related cognitions? An explorative cohort study

Abstract

Background: In frozen shoulder (FS), inflammatory-fibrotic adaptations in capsuloligamentous structures are typically linked to perceived glenohumeral stiffness, glenohumeral range of motion (ROM) restrictions and decreased arm function. However, ROM restrictions based on muscle guarding are suggested as well. Objectives: To assess differences between pain, perceived stiffness, ROM restrictions and arm function at time of diagnosis and at four months follow-up and to assess whether perceived stiffness, ROM restrictions and arm function relate to pain, structural and/or cognitive factors. Design: observational cohort study. Methods: In persons with idiopathic FS, pain intensity at rest/at night/during activities (Numeric Rating Scale), perceived stiffness (Numeric Rating Scale), abduction/external rotation ROM (goniometry), and function (Dis-abilities of the Arm, Shoulder and Hand Questionnaire) were compared between both time points (Wilcoxon-signed rank tests). Spearman correlation coefficients assessed the relation between perceived stiffness, ROM and function on the one hand and structural factors (coracohumeral ligament (CHL) thickness and inferior gleno-humeral recess (IGR) perimeter-arthroMRI), pain intensity and pain-related cognitions (Pain Catastrophizing Scale, Tampa Scale for Kinesiophobia) on the other hand. Results: Twenty persons participated (14 female; 56±8yrs) and three persons dropped out at 4 months. Pain intensity, perceived stiffness, ROM and arm function improved over time. ROM was related to CHL-thickness and IGR-perimeter; perceived stiffness was related to pain intensity; and arm function was related to pain intensity and pain-related cognitions. Conclusion: Objectively measured ROM is related to structural factors, while patient-reported outcomes are related to pain intensity and/or pain-related cognitions. Perceived stiffness does not relate to structural factors.