Results of mechanomyographic study of long radial hand extensor in 32 patients with radial nerve neuropathy were analyzed. The novel way of secure early diagnostics of reinnervation was presented. The method uses the quality characteristics of muscular contractility. The small sized device with the body mount were worked out. The main mechanomyographic changes of de- and reinnervation process were registered and explained. The contractility index, allowing assess the treatment efficacy, was defined.