Pathological changes in the subsynovial connective tissue increase with self-reported carpal tunnel syndrome symptoms

- We examined subsynovial connective tissue and carpal tunnel syndrome symptoms.
- Symptoms were self-reported from established questionnaires.
- Ultrasound measured the thickness and gliding of subsynovial connective tissue.
- Participants with symptoms had greater thickness ratio and greater shear strain index.
- This study provided new insights in carpal tunnel syndrome pathophysiology.

BackgroundFibrosis and thickening of the subysnovial connective tissue are the most common pathological findings in carpal tunnel syndrome. The relationship between subsynovial connective tissue characteristics and self-reported carpal tunnel syndrome symptoms was assessed.MethodsSymptoms were characterized using the Boston Carpal Tunnel Questionnaire and Katz hand diagram in twenty-two participants (11 with symptoms, 11 with no symptoms). Using ultrasound, the thickness of the subsynovial connective tissue was measured using a thickness ratio (subsynovial thickness/tendon thickness) and gliding function was assessed using a shear strain index ((Displacementtendon − Displacementsubsynovial) / Displacementtendonx 100). For gliding function, participants performed 10 repeated flexion-extension cycles of the middle finger at a rate of one cycle per second.FindingsParticipants with symptoms had a 38.5% greater thickness ratio and 39.2% greater shear strain index compared to participants without symptoms (p < 0.05).InterpretationUltrasound detected differences the SSCT in symptomatic group that was characterized by low self-reported symptom severity scores. This study found ultrasound useful for measuring structural and functional changes in the SSCT that could provide insight in the early pathophysiology associated with carpal tunnel syndrome symptoms.