Subsynovial Connective Tissue Thickness Is Associated With Disease Status and Severity in Carpal Tunnel Syndrome

ABSTRACT Purpose Noninflammatory thickening of the subsynovial connective tissue (SSCT) is commonly observed early in carpal tunnel syndrome (CTS). However, previous research on which subject characteristics influence SSCT thickness remains limited. This study aimed to investigate the effect of disease status and severity on SSCT thickness in subjects with and without CTS while considering subject characteristics. Methods A total of 170 wrists from 91 subjects were assessed for the absence/presence of CTS, determined through clinical symptoms and electrodiagnostic testing. Participants completed the Katz hand diagram, Boston Carpal Tunnel Questionnaire (BCTQ), Disability of Arm, Shoulder and Hand (DASH), and Visual Analog Scale (VAS). SSCT thickness and median nerve cross‐sectional area (CSA) were measured via ultrasound. Results Linear mixed‐effects models indicated significant associations between SSCT thickness and CTS presence, as indicated by both clinical symptoms and electrodiagnostic testing ( β = 0.127, p = 0.0007), and the Katz hand diagram ( p = 0.002). Moreover, SSCT thickness was associated with CTS severity, as evidenced by VAS ( β = 0.001; p = 0.001), BCTQ (symptom severity score: β = 0.038, p = 0.005; Functional Status Scale: β = 0.039, p = 0.02), DASH ( β = 0.003, p = 0.002), and CSA ( β = 0.011; p = 0.0001). Conclusion The SSCT thickness was larger in wrists with CTS and increased with increasing CTS severity. Consequently, SSCT thickness emerges as a potential biomarker for both the presence and severity of CTS, offering valuable insights for clinical assessment and management. Trial Registration ClinicalTrials.gov identifier: NCT04491058