Summary

A higher graft signal, identified at the 12-month MRI assessment, indicating a poorer graft healing is a risk factor for ACL re-tear within the first three years postoperatively. MRI after ACLR should be recommended and used to guide the follow-up management.

Abstract

Background

Anterior Cruciate Ligament (ACL) injuries are amongst the most common knee injuries in young adults. Re-tear after ACL reconstruction has been reported between 6% and 31%, resulting in worse outcomes and increased risk of post-traumatic osteoarthritis. Research has focused on managing surgical variables such as graft choice and fixation to reduce re-tear risk. However, there is still a lack of evidence on the value of post-operative parameters as predictors for graft re-tear.
This study aimed to investigate if post-operative magnetic resonance imaging (MRI) assessment, clinical outcomes, and the return to sport (RTS) test are risk factors for early graft re-ruptures and, if so, how they could influence the RTS decision.

Study Design

Cohort study; Level of evidence 3

Methods

The study is a retrospective analysis of prospectively collected patients who underwent primary ACLR using hamstring autograft between 2019 and 2022, with a minimum follow-up of 12 months. Baseline characteristics and intraoperative and postoperative information were collected, including ACL re-tear, 9-month RTS scores, 12-month GNRB arthrometer laxity, clinical outcomes, and MRI assessment. Tunnel widening and positioning were assessed and analyzed. Patients who experienced re-tear of the graft within the first three years were selected and compared with a matched cohort with a ratio of 1:4 to reduce statistical noise. Continuous variables were compared. Preoperative and intraoperative parameters were analyzed through logistic regression and analysis of variance to identify significant association with re-tear. P values <0.05 were considered significant.

Results

Overall, 13 patients were included in the re-tear group and compared with 50 patients matched for baseline characteristics who underwent the same ACLR. The mean follow-up was 23.6±4.2 months (range, 16 to 36 months).
The 12-month MRI showed a greater graft signal in case of re-tear compared to the remaining patients (2.93 vs 2.02; p=0.029), indicating worse healing. The Analysis of variance showed a positive interaction between graft signal and re-tear (ANOVA, p=0.028). Tunnel positioning was comparable between the groups, and not associated with re-tear. Similarly, tibial and femoral tunnel widening were comparable between the two groups and not associated with graft re-tear (p=0.733 and p=0.190).
A greater proportion of patients reported an anterior knee laxity >2mm in the re-tear group (83.3% vs 38.8%, p=0.058). However, the mean laxity at 1-year was comparable in the re-tear and control groups at 2.55 mm and 1.35 mm (p=0.189), respectively. When analyzing the clinical scores, no differences were noted at the 12-month follow-up between the two groups. Similarly, no differences were noted in 9-month RTS scores.

Conclusion

A higher graft signal, identified at the 12-month MRI assessment, indicating a poorer graft healing is a risk factor for ACL re-tear within the first three years postoperatively. MRI after ACLR should be recommended and used to guide the follow-up management. Further research is required to confirm these preliminary findings.

Keywords

ACL; ACL reconstruction; graft failure; hamstring tendon autograft; MRI; graft healing; tunnel positioning; tunnel widening; laxity; IKDC subjective form; Lysholm; Tegner activity level; return to sport; ACL-RSI