Healing of Tendon Defects Implanted with a Porous Collagen-GAG Matrix: Histological Evaluation

There is currently no method to restore normal function in tendon injuries that result in a gap. The objective of this study was to evaluate the early healing of tendon defects implanted with a porous collagen-glycosaminoglycan (CG) matrix, previously shown to facilitate the regeneration of dermis and peripheral nerve. A novel animal model that isolates the tendon defect site from surrounding tissue during healing was employed. This model used a silicone tube to entubulate the surgically produced tendon gap of 10 mm, allowing for the evaluation of the effects of the analog of extracellular matrix on healing of tendon, absent the influences of the external environment. The results showed that tendon stumps induced synthesis of a tissue cable inside the silicone tube in both the presence and absence of CG matrix. The presence of the CG matrix, however, altered the process of tendon healing. Tubes filled with CG matrix contained a significantly greater volume of tissue at the time periods of evaluation: 3, 6, and 12 weeks. Granulation tissue persisted for a longer period of time in the lesion site of CG-filled defects, and the amount of dense fibrous tissue increased continuously during the period of study in defects filled with CG matrix. In contrast, the amount of dense fibrous tissue decreased after 6 weeks in originally empty tubes. In tubes that did not contain the CG matrix, the new tissue consisted of dense aggregates of crimped fibers with a wavelength and fiber bundle thickness that were significantly shorter than those in normal tendon, and consistent with the type of scar that is the end result of repair of many connective tissues. Although, CG-filled tubes contained dense fibrous tissue by 12 weeks, the tissue had no crimp. The CG matrix may have prolonged the synthesis of granulation tissue and delayed or prevented the formation of scar. Departments of 'Materials Science and Engineering, and Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139. Rehabilitation Engineering R&D Laboratory, Brockton/West Roxbury VA Medical Center, West Roxbury, MA 02132. department of Orthopedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115. Current Address: Department of Materials Science and Engineering University of Michigan Ann Arbor, MI 48109. Presented at the Inaugural Meeting of the Tissue Engineering Society, Orlando, Florida, December 13-15, 1996.