Summary

Proximal graft size <8.5mm represents a strong risk factor for ACL re-tear in the first three years postoperatively, especially in male patients. Medial meniscal suture during index reconstruction increases the risk of subsequent surgery on the same knee

Abstract

Background

ACL injuries are amongst the most common knee injuries in young adults. The annual incidence in the general population is 0.03%, reaching 0.21-3.67% in professional athletes. As many as 90% of patients elect to undergo ACL reconstruction (ACLR). Re-tear after ACLR has been reported between 6% and 31%. This study aims to determine the incidence of second ACL injuries and identify risk factors for a re-tear of the graft.

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, intraoperative and postoperative information were collected, including a 9-month return to sports scores (RTS), GNRB arthrometer laxity, clinical outcomes, ACL re-tear, and reoperation rate. Preoperative and intraoperative parameters were analysed through logistic regression and analysis of variance to identify significant association with re-tear and reoperation. P values <0.05 were considered significant.

Results

Overall, 310 patients were included for analysis. The mean age at the time of surgery was 30.510.7 years. A hamstring graft was used in every case. The mean distal graft size in females and males was 8.50.5 mm and 9.00.5 mm, while the proximal was 8.30.5 mm and 8.80.6 mm (p<0.001). The re-tear rate was 6% (18 of 310 knees) at a mean 38-month follow-up. Re-injury occurred at a mean of 26 months after index surgery (range, 12 to 36 months). The logistic regression analysis showed that the size of the proximal graft <8.5mm was significantly associated with ACL re-tear (OR 5.81, 95%CI 1.50 to 22.51, p=0.020). The size of the proximal graft was 8.30.5mm in cases of ACL re-tear compared with 8.60.6mm in the rest of the patients (Mann-Whitney U, p=0.034). The same model showed that older age was a protective factor with a yearly 10% reduced risk of re-tear (OR 0.89, 95%CI 0.80 to 0.99, p=0.028). The Receiver Operator Characteristic (ROC) curve showed an Area Under the Curve (AUC) of 0.84 with an accuracy of 95%, supporting the quality of the model. The Analysis of variance showed a positive interaction between gender, re-tear, and proximal graft size (ANOVA p=0.020) with a post-hoc comparison showing significantly greater proximal graft in males compared to females (MD 0.42, ptuckey <0.001) and in males without a re-tear compared to males with a re-tear (MD 0.54, ptuckey=0.015). Medial meniscal tear treatment was a strong risk factor for reoperation (OR 20.1; p=0.007). Patients with medial and lateral meniscal tears that required treatment had a higher incidence of re-operation (25%, 6 of 24 knees) than those with isolated medial tears (17%, 9 of 54 knees) and those with lateral tears (2%, 1 of 62 knees; χ2 p=0.003). No significant differences were noted for RTS scores and clinical outcomes.

Conclusion

Proximal graft size <8.5mm represents a strong risk factor for ACL re-tear in the first three years postoperatively, especially in male patients. Medial meniscal suture during index reconstruction increases the risk of subsequent surgery on the same knee.