Intrinsic tendon fibroplasia: documentation by in vitro studies

There has been considerable controversy concerning the capacity of tendons to heal intrinsically without adhesion formation. To help clarify this issue, a tissue culture model was developed to study the potential of tendon fibroblasts to proliferate and migrate. Avian flexor tendons, isolated free of sheath and all synovial components, were maintained in sterile culture plates with Dulbecco's Modified Eagle Medium. After 5 days in culture, the 2 mm tendon biopsies were analyzed for DNA synthesis [( 125I])iododeoxyuridine incorporation) and migration of fibroblasts out of the explant (planimeter analysis). DNA synthesis was maximal on day 5 in culture, and tendon fibroblasts were observed migrating from the biopsy within 48 h. Addition of cells from plasma resulted in a significant increase in fibroblast migration, and the presence of fibrin in the plasma clot was an absolute requirement for the migratory process. These findings further support the hypothesis that injured tendons can heal by an intrinsic healing process in addition to healing by adhesion formation.