Introduction

The etiology of tunnel enlargement after anterior cruciate ligament (ACL) reconstruction is unknown. In this study, we eliminated mechanical factor by immobilizing the stifle after ACL reconstruction and tried to reveal the biological factors on tunnel enlargement.

Materials and methods

Seven mature mongrel dogs (average age 1.9 years; 4 males and 3 females) were included in our study. After cutting the ACL, an open reconstruction was performed by using a fascia latae autograft. Femoral and tibial tunnels were made by using a 6-mm drill and the graft was fixed onto the both ends of tunnels with non-absorbable sutures and stifle motion was eliminated with an above-stifle cast. The tunnels were evaluated at the post-operative 1^st day, 3^rd and 6^th weeks with computed tomography (CT). Reformatted CT images on appropriate planes were obtained and the cross-sectional area of tibial and femoral tunnels were measured from reformatted transverse sections.

Results

All tunnels were found enlarged over time in the comparison of the 1st day with 3rd week, and 1st day with 6th week (F; 37.237, P<0.005). However, there was no statistically difference between 3rd and 6th weeks (P>0.005). Although both tunnels seemed to have more prominently enlarged close to the stifle joint, this could not be statistically proven, probably due to the limited number of subjects.

Conclusion

The fact that even when the stifle motion is eliminated both tunnels (tibial and femoral) enlarge very early after ACL surgery suggests that mechanical factor is probably not responsible in tunnel enlargement.