Science News: Effectiveness of Pulse Electromagnetic Field Therapy in Patients With Subacromial Impingement Syndrome: A Double-Blind Randomized Sham-Controlled Study

Submitted by: Joshua M. Wilson, MD
Edited by: Rebecca O'Bryan, MD

Summary: Pulse electromagnetic fields (PEMF) has been shown to promote tenocyte and myoblast proliferation in vitro. It has been further found to be associated with short-term improvements in pain and function in individuals with knee osteoarthritis. The authors of this study investigated PEMF application in subacromial impingement syndrome (SIS) in conjunction with physical therapy.

In a double-blinded control study, 80 individuals with SIS symptoms or radiographic evidence of SIS were recruited from outpatient clinics. Study participants were randomized to the PEMF 5 days a week for 4 weeks or sham PEMF. All participants underwent standardized physical therapy for 4 weeks in the hospital under supervision. Visual analogue scale (VAS) pain scores, active joint range of motion (ROM), and muscle strength were recorded before and after 4 weeks and again at a 12 week follow up appointment. During evaluations functional capacity was assessed using the Constant Murley Score (CMS) and the Shoulder Pain and Disability Index (SPADI).

At baseline, the groups were similar in age, sex, and symptom duration. There were noticeable differences in favor of sham group having more shoulder flexion and internal rotation at baseline. While both groups had linear reductions in pain, the PEMF group had lower VAS scores at rest (0.17±0.50 vs 1.6±1.49, p<0.001) and with movement (0.90±1.46 vs 3.85±1.99, p<0.001). Despite the sham PEMF arm having greater ROM at baseline, the PEMF group achieved significantly more ROM gains and overall degree of ROM in shoulder flexion (139° to 177.92°±9.77 vs 152.97° to 175.72°±7.82; p=0.002) and resolution of differences in internal rotation (67.97°±16.88 to86.1°±7.19 vs 79.22°±11/57 to 86.90°±5.49; p=0.876). PEMF was associated improved function with lower total SPADI scores (5.48±9.72 vs 18.65±15.99; p<0.001) and higher CMS scores (90.42±6.94 vs 78.07±12.86; p<0.001).

Comments: Being a large double blinded randomized controlled trial it provides compelling evidence for PEMF as adjunct to physical therapy for SIS. The outcome is clouded using weighted randomization for sex and age resulting in group differences at baseline. In addition, it would have been interesting to have a PEMF only group, to see if benefit was additive or synergistic with physical rehabilitation. It would also be valuable to have more long term follow up to see chance of reoccurrence and durability of response. SIS/rotator cuff pathology and their referred pain pattern are common mimics for cervical radiculopathy and axillary nerve injury. These are frequent reasons that patients are referred for electrodiagnostic evaluation. Patients and clinicians are often left disappointed when a very symptomatic individual is found to have a normal study and no diagnostic clarity. Knowledge of nerve injury mimics and available treatments are essential to producing well-round EDX physicians.

- Liu M, Lee C, Laron D, et al. Role of pulsed electromagnetic fields (PEMF) on tenocytes and myoblasts-potential application for treating rotator cuff tears. J Orthop Res. 2017;35(5):956-964. doi:10.1002/jor.23278

-Tong J, Chen Z, Sun G, et al. The Efficacy of Pulsed Electromagnetic Fields on Pain, Stiffness, and Physical Function in Osteoarthritis: A Systematic Review and Meta-Analysis. Pain Res Manag. 2022;2022:9939891. Published 2022 May 9. doi:10.1155/2022/9939891

-Sorrell RG, Muhlenfeld J, Moffett J, Stevens G, Kesten S. Evaluation of pulsed electromagnetic field therapy for the treatment of chronic postoperative pain following lumbar surgery: a pilot, double-blind, randomized, sham-controlled clinical trial. J Pain Res. 2018;11:1209-1222. Published 2018 Jun 22. doi:10.2147/JPR.S164303