Human flexor tendon participation in the in vitro repair process.

This work demonstrates that human flexor tendon segments have the same capabilities to survive culturing and to mobilize an intrinsic healing response as previously described animal models. Segments of human flexor profundus tendons from the flexor tendon sheath were cultured in vitro and analyzed at 1, 2, and 4 weeks by scanning and transmission electron microscopy. The epitenon area thickened during the first week of culture. Fibroblasts migrated over the cut surface of the collagen bundles until they encapsulated the cut end by the second week when new collagen fibrils were seen in the extracellular spaces. By the fourth week, cells in multiple layers covered the cut end of the tendon, both collagen fibrils and new mature collagen bundles were seen. End encapsulation was accomplished by fibroblasts migrating from the outer surface and the interstices of the tendon. The encapsulating cells were active in phagocytosis and collagen synthesis during the entire incubation period.