A comparative study of collagen morphology and joint strength in anterior cruciate ligament repair and reconstruction models in rabbits.

BACKGROUND AND AIM

Anterior cruciate ligament (ACL) repair offers several theoretical advantages over reconstruction, including preservation of native proprioception and reduced donor-site morbidity. However, the current experimental models are predominantly limited to ACL reconstruction, leaving a critical gap in ACL repair research. This study introduces a novel rabbit model to evaluate osteointegration and mechanical strength at the tendon/ligament-bone interface following ACL repair and reconstruction.

MATERIALS AND METHODS

Six male New Zealand White rabbits (), aged 90 ± 0 days and weighing 2.50 ± 0.20 kg, were randomly assigned to two groups: ACL reconstruction (n = 3) using the extensor digitorum longus tendon graft and ACL repair (n = 3) using the Krackow suture technique at the femoral attachment. Specimens were collected 6 weeks postoperatively for histological evaluation of Sharpey's-like fibers, immunohistochemical analysis of types I and III collagen, and biomechanical tensile testing.

RESULTS

All surgical procedures were completed without complications. Histological analysis showed greater numbers of Sharpey's-like fibers in the reconstruction group (6.33 ± 0.58%) compared to the repair group (5.67 ± 1.6%), though not statistically significant (p > 0.05). Type I collagen fibers were significantly longer in the reconstruction group in both longitudinal (3.10 ± 0.05 μm vs. 2.97 ± 0.04 μm) and transverse (1.94 ± 0.09 μm vs. 1.81 ± 0.05 μm) dimensions (p < 0.05). Type III collagen dimensions did not differ significantly. The mean tensile failure load was higher in the reconstruction group (105.96 ± 63.37 N) than in the repair group (62.56 ± 20.11 N), though this difference was not statistically significant (p > 0.05).

CONCLUSION

This study establishes a reproducible and cost-effective ACL repair model in rabbits and confirms that tendon-bone osteointegration occurs in both ACL repair and reconstruction. Superior biomechanical strength and enhanced type I collagen integration in the reconstruction group underscore current clinical outcomes favoring reconstruction. This model offers a valuable platform for exploring biological augmentation strategies to enhance ACL repair efficacy.