The free synovial graft as a shield for collagen ingrowth in cruciate ligament repair.

The anterior cruciate ligament (ACL) was excised bilaterally in the knee joint of three dogs and was replaced in a conventional manner with a composite polyglycolic acid (PGA) and Dacron braided ligament prosthesis. In one knee of each dog, the ligaments were wrapped with a free synovial graft taken from the suprapatellar pouch in an attempt to keep the prosthesis extrasynovial, while the ligaments in the opposite three knees were left uncovered and thus directly exposed to synovial fluid. The dogs were killed at approximately one year postoperation, and microscopic sections of all ligaments were taken. The three knees with the synovial sheath showed a significantly greater bulk of fibrous tissue along the ligament scaffold grossly and a greater abundance of collagen producing cells microscopically, compared to the unwrapped ligaments. The gross and microscopic findings were identical in each of the three knees with the covered ligaments and were equally consistent in the three that had been left unprotected from the synovial fluid. These findings suggest that a free synovial graft may simulate the normal protective role of the synovial membrane and allow and/or induce collagen ingrowth in synthetic or autogeneic tissue stints for the repair of acute cruciate ligament tears.