Summary

The mean lateral anterior tibial subluxation (ATS) was 5.5 mm before surgery, while it was 4.7 mm after surgery (p<0.05). The mean medial ATS was 1.4 mm before surgery, while it was 1.7 mm after surgery (p>0.05) .The preoperative lateral ATS was positive correlated with the AMB signal intensity ratio (SIR). The preoperative medial ATS was positive correlated with the AMB SIR and PLB SIR.

Abstract

Introduction

Static anterior tibial subluxation (ATS) after an anterior cruciate ligament (ACL) injury highlights the abnormal relationship between the tibia and femur in patients with ACL insufficiency. Several studies indicated that an abnormal tibiofemoral relationship remained after ACL reconstruction.
Several studies have investigated maturation of the ACL graft using MRI in clinical studies, MRI graft signal intensity (SI) after ACL reconstruction is considered a marker of graft healing and maturation.
The purpose of this study was to determine the relationship between preoperative static tibial subluxation and graft maturity on MRI after double-bundle anterior cruciate ligament reconstruction.

Methods

Sixty patients who underwent double-bundle ACL reconstruction between January 1 and December 31, 2017 were included in this retrospective study. All participants underwent magnetic resonance imaging (MRI) preoperative and postoperative at 12 months. All patients provided their informed consent to participate in this study, which was approved by our institutional review board.
Examinations were performed in the supine position with a pillow under the knee, supporting it in neutral rotation. Anterior tibial subluxation (ATS) of the lateral and medial compartments relative to the femoral condyles were measured on MRI. On sagittal proton density images, we drew a best fit-circle over the posterior femoral condyle at the subchondral bone. Along the posterior margin of the circle, a line perpendicular to the tibial plateau was drawn at the posterior aspect of the tibia. The distance between these lines determined the amount of anterior tibial subluxation.
Proton density-weighted images in an oblique sagittal plane were used for measurement for signal intensity. Regions of interest (10-mm2) were set at the anteromedial (AM) bundle and the posterolateral (PL) bundle of the ACL grafts and at the posterior cruciate ligament. Signal intensity ratio was calculated as the ratio of signal intensity of the graft to signal intensity of the posterior cruciate ligament. The SI ratio (SIR) of the 2 grafts was calculated as follows: SIR =SI of ACL graft ÷ SI of PCL.

Results

In lateral compartment, the mean ATS was 5.5 mm before surgery, while it was 4.7 mm at 12months after surgery which was statistically significant (p=0.038). In medial compartment, the mean ATS was 1.4 mm before surgery, while it was 1.7 mm at 12months after surgery which was not statistically significant (p=0.37).
The preoperative lateral ATS was weak positive correlated with the AM SIR. (r=0.257, p =0.046). The preoperative medial ATS was moderate positive correlated with the AM SIR and weak positive correlated with PL SIR. (r= 0.324, p=0.01, r=0.220 p=0.09 respectively).

Conclusion

The finding of this study was that the ATS in lateral compartment was significant different between before and after surgery. On the other hand, the ATS in medial compartment was not significant different between before and after surgery. The preoperative lateral ATS demonstrated a significant positive correlation with the AM SIR. The preoperative medial ATS demonstrated a significant positive correlation with the AM SIR and PL SIR.