Summary

Although outside-in technique in ACL reconstruction resulted in acute graft bending angle, the graft healing at the femoral tunnel showed superior results than transportal techniques

Abstract

Introduction

In the anterior cruciate ligament (ACL) reconstruction, the independent drilling technique using anteromedial portal or outside-in approach has some advantages in placing anatomical femoral tunnel than transtibial technique. Independent drilling technique, especially outside-in technique can make more acute graft bending angle at the femoral tunnel entry in spite of enough femoral tunnel length. However, no studies whether acute graft bending angle of outside-in technique might result in poor graft healing or rupture. The purpose of this study is to compare femoral tunnel location, graft bending angle, and graft healing at femoral tunnel between transportal technique and outside in technique after ACL reconstruction using MRI.

Methods

Ninety-three patients with anatomical single-bundle ACL reconstruction performed with use of either the transportal technique (45 patients) or the outside in technique (48 patients) were included for this study. Each group underwent MRI scans at least 1 year (range, 1-2 years) after the ACL reconstruction. We confirmed all patients showed intact ACL graft on MRI images. The femoral tunnel location, length, and graft bending angle at femoral tunnel were analyzed on the 3D knee models using MRI images. On the oblique axial image taken after ACL reconstruction, the graft signal intensity ratio of was calculated based on the signal intensity (SI) of the PCL using the region-of-interest (ROI) function on Marosis software to determine graft healing at the femoral and tibial tunnels. We also evaluated and compared IKDC and Tegner activity scores, and stabilities at the final follow-up between two groups.

Results

Mean interval from surgery to MRI scan was 17.9 months in transtibial group and 16.8 months in outside-in group. While the location of femoral tunnel were similar in both groups, the femoral tunnel length was a little bit longer in outside-in technique(37 vs 32 mm, p=0.07). However, the outside-in technique showed significant acute graft tunnel angle than transportal technique(100 degree vs 113 degree, p=0.04). Signal intensity ratio of the graft compared with SI of PCL was 2.3±2.2 in transportal group and 2.0±1.8 in outside-in group(p=0.07). The SI ratio of graft at the femoral tendon-bone interface area was significantly higher in transportal than in outside-in groups(3.9±2.7 vs 2.6±3.0, p=0.02). However, SI ratio at tibial tendon-bone interface area was similar in both groups(2.6±2.9 in transportal group and 2.0±1.9 in outside-in group, p=0.06). There were no significant statistical differences between the two group in terms of Tegner activity score(6.51 vs 6.80, p=0.79) and IKDC score(86.1 vs 91.0, p=0.32). We also could not find any significant differences in the results of Lachman and Pivot shift tests.

Conclusions

Although outside-in technique in ACL reconstruction resulted in acute graft bending angle, the graft healing at the femoral tunnel showed superior results than transportal techniques. However, there was no significant difference in clinical outcomes between outside-in and transportal techniques in ACL reconstruction. These findings indicate that the acute graft bending angle at the femoral tunnel in ACL reconstruction using outside-in technique did not give adverse effect on graft healing in the clinical study.