Summary

This study shows that primary ACL repair in a carefully selected patient population results in low failure rates, significant functional improvements, and high rates of return to pre-injury sports levels, with satisfactory ligament healing over a mean follow-up of 35 months

Abstract

Introduction

Primary anterior cruciate ligament (ACL) repair is a novel surgical technique with very specific indications, reserved for a highly selected group of patients. Although this approach remains controversial due to the inherently low healing potential of the ACL, recent studies have reported failure rates ranging from 3.5% to 20%.

Objective

The objective of this study was to evaluate the failure rate of a series of patients who underwent primary ACL repair with a minimum follow-up of 2 years. Secondary objectives included analyzing the type of injury, return to sports, subjective and objective outcomes, and postoperative evaluation using magnetic resonance imaging (MRI).

Methods

We conducted a retrospective cohort study including patients with Sherman type I ACL injuries who underwent primary ACL repair combined with an internal brace between 2018 and 2023. Patients with a minimum follow-up of 2 years were included in the analysis. Surgical data, return to sports, objective evaluation using the KT1000 arthrometer, failure rate, and subjective assessment with the Lysholm and IKDC scales pre- and postoperatively were analyzed. Postoperative MRI scans were used to assess the degree of homogeneity (healing) of the ACL.

Results

Thirteen surgeries were performed during the study period, with a median patient age of 36 years (IQR 31-42). Two patients did not meet the 2-year follow-up requirement, leaving 11 for analysis. The mean follow-up was 35 months (SD 5.6 months). The mean time from injury to surgery was 51.9 months (SD 9.2 months). Regarding sports activity, 6 patients had a preoperative Tegner score of 5, and 7 had a score of 7. Notably, 100% (95% CI 0-30%) of the patients returned to their pre-injury level of sports within the first postoperative year. Objective assessment with the KT1000 arthrometer showed an improvement from a preoperative side-to-side difference of 6 mm (IQR 4-7) to a difference of 1 mm (IQR 1-1) at the final follow-up. We observed that 81% (95% CI 43-94%) of patients did not experience graft failure. The two failures occurred at 16 and 20 months postoperatively, both in patients who had returned to sports, and were due to traumatic events. The Lysholm score improved significantly from a preoperative median of 65 (IQR 63-70) to 90 (IQR 87-95) postoperatively (p<0.001), and the IKDC score improved from 45 (IQR 40-51) to 90 (IQR 85-93) (p<0.001). Postoperative MRI, performed in 80% of patients at 1 year, revealed homogeneous fiber healing in 78% (95% CI 40-97%) of cases. No patients exhibited a complete absence of ACL fibers.

Conclusion

Our preliminary results suggest that primary ACL repair, though rarely indicated and performed in a highly select group of patients, yields promising outcomes with a low failure rate over a substantial follow-up period. All patients returned to sports activity, with significant improvements in both objective and subjective outcomes. MRI findings showed satisfactory ligament healing in most cases. The two failures observed were associated with traumatic events and were successfully managed with standard ACL reconstruction.