Introduction: Tunnel enlargement following anterior cruciate ligament (ACL) reconstruction has been frequently reported since the nineties, yet its etiologies remain unclear.
Aim: To elucidate the factors favoring this phenomenon and to investigate its clinical and anatomical consequences.
Methods: This was a descriptive retrospective study conducted on 37 patients who underwent ACL reconstruction surgery using single-bundle hamstring tendons with fixation using absorbable interference screws at the Traumatology Department of the Kassab National Institute of Orthopedics. The patients were collected between January 2014 and September 2016. Tunnel enlargement, footprint, and tunnel orientation were assessed using standard knee radiographs. At follow-up, patients were evaluated using functional scores (Lysholm, Tegner, and IKDC), clinical examination, and Telos radiographs.
Results: The average global Tunnel enlargement was 51.7% in the femur and 48.88% in the tibia. Femoral tunnel enlargement values were higher than tibial tunnel enlargement at all measurement levels, and it appeared to be a time-evolving phenomenon. Factors favoring tunnel enlargement seemed to include advanced age, male gender, delayed surgery, accelerated rehabilitation protocols, non-compliant placement of transplant footprints, and tunnel horizontalization. Tunnel enlargement did not influence functional scores (Lysholm, Tegner, and IKDC). However, based on the differential study of Telos radiographs, femoral and tibial tunnel enlargement in the lax knees group (38% of cases) was higher than in the stable knees group (62%). Nonetheless, our results were statistically non-significant with respective p-values of 0.584 and 0.53.
Conclusion: Several modifiable factors such as delayed surgery, accelerated rehabilitation protocols, incorrect footprint placement, and tunnel orientation appeared to influence the tunnel enlargement phenomenon. However, prospective studies with a larger sample would be necessary to confirm these findings.