Feasibility of restoring shoulder and elbow function in high tetraplegia by functional neuromuscular stimulation

Individuals with high tetraplegia (functional levels of C1-C4) resulting from spinal cord injury typically retain voluntary control only over shoulder shrug and head-neck motions, and are thus highly disabled. Restoration of even rudimentary movements would significantly increase the independence and quality of living for these individuals. We have therefore begun an effort to use functional neuromuscular stimulation (FNS) and/or reconstructive surgeries in these individuals to restore shoulder and elbow function. One individual with complete C3 tetraplegia has had percutaneous stimulating electrodes implanted into the biceps, triceps, anterior deltoid, posterior deltoid, pectoralis major, latissimus dorsi, and infraspinatus muscles. The shoulder forces and moments produced by stimulated contractions of individual muscles and by various combinations of muscles varied with arm position as expected. FNS produced a maximum shoulder flexion moment of 12.9 Nm, a maximum adduction moment of 5.9 Nm, and a maximum abduction moment of 7.5 Nm. Although voluntary actions produced very little shoulder abduction moment when used alone, stimulated contractions of the deltoid and infraspinatus muscles used together with voluntary shoulder girdle motions more than doubled the maximum moment produced by FNS alone.