The Effect of Peripheral Nerve Stimulation on Shoulder Biomechanics: A Randomized Controlled Trial in Comparison to Physical Therapy.
Richard D Wilson, Jayme S Knutson, Maria E Bennett and 1 others
PMID 28099193WHAT IT FOUND
Both peripheral nerve stimulation and physical therapy improved shoulder strength and range of motion in stroke patients, but neither treatment was superior to the other for these biomechanical changes.
Since PNS previously reduced pain more than PT, the pain relief likely stems from mechanisms other than improved shoulder mechanics.
Key findings
01There were no significant differences between the PNS and PT groups in isometric shoulder abduction strength, pain-free external rotation range of motion, or Fugl-Meyer scores, despite both groups showing improvements over time.
02Peripheral nerve stimulation and physical therapy did not significantly change the delay in initiation or termination of deltoid EMG activity.
03The study was powered for pain reduction, not biomechanical outcomes, and the authors suggest that pain relief from PNS may be caused by mechanisms other than altering shoulder biomechanics.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The study was a secondary analysis and was not powered to detect differences in the biomechanical outcomes; it was powered for the primary pain outcome. The sample size was small (25 participants), with dropouts reducing the final analyzed numbers, which may have limited the ability to detect subtle differences between groups. The reliability and responsiveness of the isometric shoulder abduction strength and EMG measurements were not established. Shoulder subluxation was not included as an outcome measure, despite being a common factor in hemiplegic shoulder pain. The minimum clinically important difference (MCID) for the strength ratio outcome had not been established, making it difficult to interpret the clinical significance of the observed changes.
Declared interests
The work was sponsored by grants from the National Institutes of Health (NICHD and NCATS). One author, Richard D. Chae, is a consultant for SPR Therapeutics, the company that manufactures the PNS device used in the study. The sponsor did not participate in the study design, data collection, analysis, or manuscript preparation.
The easy way to misread this
Do not conclude that peripheral nerve stimulation is ineffective for pain because it did not outperform physical therapy in this analysis. This paper reports secondary biomechanical outcomes, not the primary pain outcome. The authors explicitly state that PNS reduced pain significantly more than PT in the primary analysis, suggesting that pain relief occurs through mechanisms other than the improved strength and range of motion measured here.