Comparisons of intraosseous graft healing between the doubled flexor tendon graft and the bone-patellar tendon-bone graft in anterior cruciate ligament reconstruction

Purpose: The purpose of this study was to compare intraosseous graft healin g between the doubled flexor tendon (FT) graft and the bone-patellar tendon -bone (BPTB) graft in anterior cruciate ligament (ACL) reconstruction. Type of Study: Randomized trial. Methods: A biomechanical and histologic study was conducted with 24 adult beagle dogs. Bilateral ACL reconstructions were performed in each animal. Autogenous doubled FT and BPTB grafts were used for the left and right knees, respectively. Each end of the 2 grafts was te thered with a polyester suture to a screw post with a washer. The animals w ere then allowed unrestricted activities in their cages. Eight animals were killed at 3, 6, and 12 weeks, respectively. Results: Histologically, the F T graft was anchored to the tunnel wall with newly formed collagen fibers r esembling Sharpey's fibers by 12 weeks. These fibers were more abundant in the anterior (ventral) gap than in the posterior (dorsal) gap. In the BPTB graft. the bone plug was anchored with newly formed bone at 3 weeks, althou gh osteocytes in the plug trabeculae were necrotic for 12 weeks. Degenerati on of the tendon-bone junction in the plug progressed at 6 weeks. Tensile t esting showed that the weakest site was different not only between the 2 gr afts but also between the observation periods. In the FT graft, the weakest site was the graft-wall interface at 3 weeks and the intraosseously grafte d tendon at 6 weeks. In the BPTB graft, the weakest site was the graft-wall interface at 3 weeks and the proximal site in the bone plug at 6 weeks. Th e ultimate failure load of the FT graft was significantly inferior (45.8%) to that of the BPTB graft at 3 weeks (P = .021). At 6 weeks, the load of th e FT graft was 85% that of the BPTB graft without a significant difference (P = .395). Conclusions: As to the clinical relevance, the fixation device chosen for soft-tissue fixation appears to be more important than comparing it to the BPTB graft, although this has yet to be conclusively proven.