Effects of Each Phase of Anterior Cruciate Ligament Reconstruction Surgery on Joint Contracture in Rats

Background Although anterior cruciate ligament reconstruction surgery is known to cause joint contracture, the mechanisms of this process are unknown. We aimed to assess the effects of transection of this ligament and each phase of reconstruction surgery on contracture formation. Materials and methods Rats were divided into groups according to treatment received: sham (arthrotomy), ligament transection, ligament transection plus bone drilling, and ligament reconstruction. Surgery was performed on the right knee. Untreated left knees in the sham group were used as controls. Results At 7 and 28 d post-surgery, range of motion before myotomy, mainly representing myogenic contracture, was restricted in the sham and ligament transection groups, and more so in the bone drilling and reconstruction groups. Restricted range of motion after myotomy, representing arthrogenic contracture, was detected at both timepoints in the bone drilling and reconstruction groups, but not in the sham or ligament transection groups. At 3 d post-surgery, although a large blood clot was observed in all three treatment groups, only the bone drilling and reconstruction groups showed significant joint swelling. At 7 d post-surgery, inflammatory-cell infiltration into the joint capsule was most apparent in the bone drilling and reconstruction groups, and joint capsule fibrosis was also most apparent in these groups at 7 and 28 d post-surgery. Conclusions Our results suggest that (1) myogenic contracture after anterior cruciate ligament reconstruction is caused by arthrotomy and aggravated by bone drilling, and (2) arthrogenic contracture is mostly due to bone drilling, which triggers an inflammation–fibrosis cascade

The effects of the amount of weight bearing on articular cartilage early after ACL reconstruction in rats

Osteoarthritis that develops after anterior cruciate ligament (ACL) reconstruction is a critical issue. We examined the effects of the amount of weight bearing early after ACL reconstruction on articular cartilage. Rats were divided into groups according to the treatment received: untreated control, ACL reconstruction (ACLR), ACL reconstruction plus hindlimb unloading (ACLR + HU), and ACL reconstruction plus morphine administration (ACLR + M). ACL reconstruction was performed on the right knee throughout the groups. To assess the amount of weight bearing, one-hindlimb standing time ratio (STR; operated side/contralateral side) during treadmill locomotion was evaluated during the experimental period. At day 7 or 14 post-surgery, cartilage degeneration of the medial tibial plateau was histologically assessed. In the ACLR group, reduction in weight bearing characterized by significantly reduced STR was observed between day 1 and 7. Reduction in weight bearing was partially attenuated by morphine administration. Compared with the control group, the ACLR group exhibited an increased Mankin score that was accompanied by increased cyclooxygenase-2 expression in the anterior region. In the ACLR + HU group, Mankin scores were significantly higher in the middle and posterior regions, and cartilage thickness in these regions was significantly thinner than those in the ACLR group. In the ACLR + M group, although chondrocyte density in the anterior region was increased, all other parameters were not significantly different from those in the ACLR group. Our results suggest that early weight bearing after ACL reconstruction is important to reduce cartilage degeneration.</p