Recombined bone xenografts enhance tendon graft osteointegration of anterior cruciate ligament reconstruction

The objective of the study was to discover whether recombined bone xenograft (RBX), a porous solid material, could augment healing of the tendon-to-bone interface after anterior cruciate ligament (ACL) reconstruction. ACL reconstruction was performed bilaterally in 25 skeletally mature rabbits using long digital extensor tendon grafts. RBX was implanted into the treated knee, with the contralateral knee serving as control. Three rabbits were killed at postoperative weeks two, six and 12 for routine histology. The remaining 16 rabbits were killed at weeks six and 12, and their femur-graft-tibia complexes were harvested for mechanical testing. The treatment and control groups produced different histological findings at the interface between the tendon and bone. In the treatment group, large areas of chondrocyte-like cells were noted around the tendon-bone interface two weeks after the operation. At six weeks, more abundant bone formation was observed around the tendon. At 12 weeks, an immature neoenthesis structure was seen. In biomechanical evaluation six and 12 weeks after the operation, the ultimate strength of tendon in the bone tunnel was significantly higher in the treatment group than in the control group. RBX can augment the osteointegration of tendon to bone after ACL reconstruction.