Summary

MRI evaluation of graft healing after ACL reconstruction with all inside graft link technique

Abstract

Background

The all-inside graft-link ACL reconstruction technique is based upon the use of a quadrupled semitendinosus graft fixed with adjustable loop suspensory devices (ALD) on both femoral and tibial sides. This technique is gaining popularity due to potential benefits that may include faster recovery, reduced invasiveness, and reduced donor site morbidity, when compared to standard techniques. However, the main concerns with this technique are related to the magnitude of the overall cyclic displacement that may occur with two ALDs. In turn this leads to additional concerns, including the potential increased risk of inferior graft maturation/incorporation and tunnel widening (TW).

Objective

The primary objective of this study was to prospectively evaluate graft maturation and incorporation, and tunnel widening in a group of patients who underwent all-inside graft link ACL reconstruction using sequential 1.5 T MRI at 3, 6 and 12 months post-operatively.

Methods

20 patients were prospectively enrolled in the study. Inclusion criteria were: age between 16 and 50 years, chronic ACL tear (injury-surgery interval more than 2 weeks) confirmed by physical examination and preoperative MRI, a healthy contralateral side, and no prior injures to the affected knee.
1.5 T MRI was performed at 3, 6 and 12 months post-operatively to evaluate graft maturation and integration and tibial tunnel widening. The following parameters were considered at each follow-up: signal-to-noise quotient (SNQ), bone-graft integration scale (signal intensity at the bone-graft interface), ligament signal by Howell scale, and tibial tunnel widening. Radiological parameters were evaluated by an expert radiologist and an orthopedic surgeon. The final clinical evaluation was performed at a minimum follow-up of 2-years. This included physical examination, patient-reported outcomes (PROs) and KT-1000 arthrometer. The Mann-Whitney U test was used to analyze differences in imaging findings between different time points

Results

The mean signal-to-noise quotient (SNQ) was 4.4 ± 2.6 at 3 months post-op, 1.6 ± 0.7 at 6 months post-op and 1.9 ± 1.4 at 12 months post-op. There was a statistical difference between 3 and 6 months (p=0,028) and between 3 and 12 months (p=0.05) with no differences between 6 and 12 months. The mean tibial tunnel widening was 41.2% ± 36.7% at 3 months, 52.4% ± 18.7% at 6 months and 45.5% ± 46.6% at 12 months. Tunnel widening reduced significantly at 12 months post-operatively when compared to 6 months post-operatively (p=0.5). The Howell scale show statistically significance between 3 and 12 months, with patients identified as Grade 1 going from 30% to 70% (p=0.05). The bone-graft integration scale show statistically significance between 3 and 12 months, with patients identified as Grade 1 go from 45% to 65%, comparing 3 and 12 months (p=0.01).

Conclusion

Significant maturation and incorporation of all-inside graft-link ACL grafts occurs by 6 months post-operatively, with no further maturation apparent between 6 and 12 months. These promising results suggest that even if cyclic displacement occurs it does not compromise maturation and incorporation. These findings are supported by a significant reduction in tibial tunnel diameter and MRI evidence of graft healing occurring within the tibial socket by 12 months post operatively.