Effect of Adding Interferential Current in an Exercise and Manual Therapy Program for Patients With Unilateral Shoulder Impingement Syndrome: A Randomized Clinical Trial

The purpose of this study was to measure the additional effect of adding interferential current (IFC) to an exercise and manual therapy program for patients with unilateral shoulder impingement syndrome. Forty-five participants were randomly assigned to group 1 (exercise and manual therapy), group 2 (exercise and manual therapy + IFC), or group 3 (exercise and manual therapy + placebo ultrasound). Individuals participated in 16 treatment sessions, twice a week for 8 weeks. The primary outcome of the study was total score of the Shoulder Pain and Disability Index (SPADI). The secondary outcomes were the pain and disability subscales of SPADI, Numeric Rating Scale, and Pain-Related Self-Statement Scale. Adjusted between-group mean differences (MDs) and 95% confidence intervals (CIs) were calculated using linear mixed models. After 16 treatment sessions, statistically significant but not clinically important differences were identified in favor of the exercise and manual therapy program alone in the SPADI-total (group 1 vs group 2, MD 11.12 points, 95% CI 5.90-16.35; group 1 vs group 3, MD 13.43 points, 95% CI 8.21-18.65). Similar results were identified for secondary outcomes. The addition of IFC does not generate greater clinical effects in an exercise and manual therapy program for individuals with unilateral shoulder impingement syndrome.