Influence of the site of injury on the spontaneous healing response in a rat model of total rupture of the anterior cruciate ligament

ABSTRACT

Aim

The healing ability of the anterior cruciate ligament (ACL) injury is very poor; however, it has recently been shown to undergo self-healing with conservative treatments. In this study, we evaluated the influence of the site of injury on the healing process after complete transverse tear of ACL using a rat model.

Materials and Methods

A total of 58 skeletally mature Wistar rats were randomly assigned to various ACL injury groups: controlled abnormal movement-mid-portion (CAM-MP), controlled abnormal movement-femoral side (CAM-FS), ACL transection-mid-portion (ACLT-MP), or ACL transection-femoral side (ACLT-FS) injury groups. The ACL was completely transected in the mid-portion in the ACLT-MP and CAM-MP groups, and on the femoral side in the ACLT-FS and CAM-FS groups. Both CAM groups underwent extra-articular braking to control for abnormal tibial translation. The animals were allowed full cage activity until sacrifice postoperatively for histological and biomechanical assessment.

Results

Significant differences were found in the ratios of residual ligament lengths between the CAM-MP and CAM-FS groups, demonstrating the validity of each model. Spontaneous healing of the injured ACL was observed in the CAM-MP and CAM-FS groups but not in the ACLT-MP and ACLT-FS groups. The mechanical strength of the healing ACL did not differ between the CAM-MP and CAM-FS groups 8 weeks after injury; however, the former had better mechanical strength than the latter 12 weeks after the injury.

Conclusion

ACL injuries in the mid-portion and on the femoral side may be treated with conservative therapy for spontaneous healing.

KEYWORDS:

• Anterior cruciate ligament
• spontaneous healing
• indication criteria
• injury site

Acknowledgments

We would like to thank the members of the Basic Science Laboratory at the Saitama Prefectural  University for their cooperation.

Disclosure statement

No potential conflict of interest is reported by the authors.

Additional information

Funding

This work was supported by a Saitama Prefectural University Research (SPUR) Grant.