NMES for Shoulder Stability: External Rotators Are Superior
Evidence-Based Rationale
- The American Heart Association/American Stroke Association guidelines recommend electrical stimulation to improve shoulder lateral (external) rotation for preventing shoulder pain in the involved upper extremity after stroke 1
- Price and Pandyan's Level I evidence demonstrated that patients receiving electrical stimulation had a significant treatment effect in favor of pain-free lateral rotation, even though pain intensity itself did not change compared to controls 1
- Bohannon et al. identified that range of lateral rotation was the factor that related most significantly to the onset/occurrence of shoulder pain 1
- Improving external rotation and abduction range of motion through stretching and mobilization is specifically recommended as a means of preventing frozen shoulder and shoulder-hand pain syndrome 1
- The 2016 AHA/ASA guidelines reiterate that gentle mobilization and stretching exercises should focus on increasing external rotation and abduction 2
- Loss of external rotation is a primary contributor to adhesive capsulitis and complex regional pain syndrome in the hemiplegic shoulder 1
- Internal rotators (subscapularis, pectoralis major) are more commonly associated with spasticity-related pain rather than instability 2, 3
- Botulinum toxin injections into the subscapularis and pectoralis major are used to treat spasticity-related shoulder pain, not to improve stability 2, 3
- Excessive internal rotation contributes to shoulder protraction and poor posture, which decreases vital capacity and increases work of breathing 4
Clinical Implementation
- Target the infraspinatus and teres minor muscles (primary external rotators) with surface or intramuscular electrodes 1, 2
- Use tetanic frequencies (20-75 Hz) to produce fused contractions that maximize muscle tension and strength gains 5, 6, 7
- Apply high duty cycles (1:1 or 1:2 on:off ratio) with on-times of at least 2 seconds to evoke high muscle tension 5, 6
- Position the shoulder in slight external rotation (not maximal) during initial sessions to avoid delayed onset muscle soreness, then progressively increase the lengthened position over weeks 5, 8
- Implement 2-3 sessions per week for strength gains, allowing adequate recovery between sessions 6, 8, 9
Common Pitfalls to Avoid
- Do not use overhead pulleys, which encourage uncontrolled abduction and have the highest incidence of developing hemiplegic shoulder pain 1
- Avoid aggressive passive range of motion if done improperly, as it could cause more harm than good to the complex shoulder joint 3
- Do not neglect staff education to prevent trauma to the hemiplegic shoulder during transfers and positioning 1
- Start with lower stimulation intensity during first sessions to prevent muscle damage and gradually increase to maximum tolerable levels 10