40 experimental rats had 80 silicon prostheses implanted in the hind legs for the purpose of studying the peculiarities of a capsule developing round the implant over one to twelve weeks. The silicon implant was found to help develop a smooth-walled inter-tissue capsule with a concentric pattern of collagen fibres and fibroblasts without the development of any epithelium-like lining on the inner surface of the wall. The thickness of the capsular wall becomes stabilized after six to eight weeks, never exceeding the 350 microns to 400 microns mark. The capsular wall is supplied from a concentrically growing capillary groove. The clinical material summarizes experience of 15 cases (24 fingers) of inveterate flexor tendon damage in digits II-V in the "critical" zone (II). The authors used a new method of rotated pedicled tenotransplant fixation to the distal phalanx. This permitted to dispense with plast-of-Paris immobilization, to start rehabilitation earlier, and to score excellent and good results in twelve patients (80%) (21 fingers) within five to six weeks of the second stage of tenoplasty.