Electrical Stimulation and Its Role in Offsetting the Detrimental Effects of Immobilization After Rotator Cuff Repair in a Rat Model

Background: After rotator cuff repair, immobilization (IM) is routinely employed to limit mechanical loading at the repaired enthesis and reduce the risk of reinjury. However, prolonged IM can lead to stiffness, muscle atrophy, and impaired healing, including fatty degeneration and abnormal matrix remodeling. Hypothesis/Purpose: The purpose of this study was to determine whether adjunctive electrical stimulation (ES) during postoperative IM mitigates disuse-related impairments and promotes tendon-to-bone healing and functional recovery after rotator cuff repair in a rat model. ES applied during IM would mitigate IM-related impairments, enhance tendon-bone healing, and accelerate functional recovery. Study Design: Controlled laboratory study. Methods: A total of 45 adult male Sprague-Dawley rats underwent unilateral supraspinatus repair and were randomized to the control, IM, or IM with ES (IM/ES) groups. IM was achieved by forelimb fixation, and the IM/ES group received daily transcutaneous ES. Outcomes at 2 and 4 weeks included histology, magnetic resonance imaging mapping, biomechanical testing, and gait analysis. Results: Rats that underwent IM/ES exhibited a more mature tendon-bone interface with increased proteoglycan deposition and collagen organization compared with the control and IM groups (P < .001). Chondrogenic marker expression was upregulated, whereas fatty infiltration (FABP4) was suppressed. At 4 weeks, the IM/ES group demonstrated lower T2 relaxation times (140.2 ± 24.4 ms) and higher ultimate failure load (27.7 ± 2.1 N) versus the IM (16.6 ± 1.7 N) and control groups (13.9 ± 1.3 N) (P < .0001). Gait analysis confirmed superior functional recovery. Conclusion: ES administered during IM improved tendon-bone healing by reducing FABP4 and enhancing fibrocartilaginous remodeling, resulting in superior structural, biomechanical, and functional outcomes. Clinical Relevance: These findings suggest that adjunctive ES during the IM after rotator cuff repair may offset the detrimental effects of disuse and promote earlier and stronger tendon-bone healing, supporting its potential translation to postoperative rehabilitation strategies.