A multidisciplinary study of the healing of an intraarticular anterior cruciate ligament graft in a goat model

We evaluated knee function, tensile properties, and histologic appearance of a healing intraarticular bone-patellar tendon-bone autograft after anterior cruciate ligament reconstruction in a goat model. The patellar tendon graft was fixed such that both bone-to-bone (femoral tunnel) and bone-to-tendon (tibial tunnel) healing could be studied. The total anteroposterior translation significantly increased from 3 to 6 weeks, ranging from increases of 28.8% to 46.7%. In situ forces in the replacement graft decreased as much as 22.2% at 6 weeks. Conversely, tensile properties of the femur-anterior cruciate ligament graft-tibia complex did not change significantly from 3 to 6 weeks. However, the mode of failure changed from the graft pulling out of the tibial tunnel at 3 weeks to a mix of midsubstance failures (N=2) and pullouts (N=5) at 6 weeks. Histologic evaluations revealed progressive and complete incorporation of the bone block in the femoral tunnel, but only partial incorporation of the tendinous part of the graft in the tibial tunnel. The differences demonstrated at 3 and 6 weeks may be a result of the remodeling process of the midsubstance of the graft as the interfaces within the osseous tunnels mature.