Research of innervation and function of shoulder joint stabilizer muscles and parts of deltoid muscles in patients with old fractures of proximal humerus

Neurophysiological study of rotator cuff functions (m. biceps brachii, m. triceps, m. deltoideus dex. et sin.) and its innervation in patients with monolateral old fractures and fracture-dislocations of the proximal humerus are presented. Period after trauma was an average of one year. Significant neuritis of n. axillars and n. musculocutaneus were revealed on the traumatic side. Lowering of M-answers in comparison with individual norm was at 48,5% for n. axillaris, 59% - for n. musculocutaneus, 68% - for n. radialis. Strong degree of n. axillaris damage (M-answer 30% below normal) was observed in 39% of patients, that is more often than neuritis of other plexus nerves: similar effect on n. musculocutaneus was two times more often (18% of cases) and 8 times more often than еffect on n.radialis (5% of cases). An in-depth study of the functions of the anterior, middle and posterior parts of the deltoid muscle was carried out in these patients on both sides. Interferencial electromyography demonstrated significant irregularity of bioelectrical activity of different deltoid parts. Stimulating electromyography of m. deltoideus parts innervation recorded reduced activity of the front part of the muscle, caused by weak innervations of its n. axillaris branch in comparison with the norm. Reliable distinctions in function and innervation of deltoid parts were found between each other as well as between intact and damaged sides. The recommendation to carry out electromyography of each part of deltoid was substantiated for patients with complex old fractures of proximal humerus before reconstruction surgeries or shoulder arthroplasty.