Sustained Clinical and Functional Outcomes After Primary Anterior Cruciate Ligament Repair: A Minimum 5-Year Follow-up Study.

BACKGROUND

Primary anterior cruciate ligament (ACL) repair (ACLPR) demonstrates promising short-term clinical outcomes in select patients; however, it remains poorly understood as to whether previously reported short-term outcomes are maintained at midterm follow-up.

PURPOSE

To determine whether short-term (2-year) outcomes are maintained at 5 years after ACLPR, evaluate age-stratified failure and reoperation rates, and identify preoperative risk factors for failure.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This prospective study included the first 113 consecutive patients with proximal (type I/II) ACL tears who underwent ACLPR between 2008 and 2017 with a minimum 5-year follow-up. Failure rates were recorded based on instrumented laxity (>3-mm anterior tibial translation side-to-side difference), pivot-shift grade (grade ≥2), and subjective instability. Patient Acceptable Symptom State thresholds were established based on collected patient-reported outcome measure scores. Logistic regression models were constructed to determine associations with independent risk factors for failure.

RESULTS

A total of 107 patients (median age, 35.5 years [interquartile range, 22.4-43.1 years]) were available at final follow-up (median, 6.0 years [interquartile range, 5.3-7.0 years]). No significant differences were reported in failure rates between 2- and 5-year follow-up: overall non-age-differentiated: 11.5% versus 15.9%, respectively ( = .34); ≤21 years: 37.0% versus 38.5%, respectively ( = .92); and >21 years: 3.5% versus 8.6%, respectively ( = .16). No failures occurred in patients aged ≤21 years, while 4 failures occurred in patients aged >21 years. Additionally, no significant differences were observed in overall non-age-differentiated reoperation rates (6.2% vs 7.5%, respectively; = .71) and contralateral ACL injury rates (3.5% vs 4.7%, respectively; = .67). Clinical outcomes and patient-reported outcome measure scores did not significantly differ between time points, and most patients met Patient Acceptable Symptom State thresholds (88% for International Knee Documentation Committee form, 91% for Lysholm scale, 93% for Forgotten Joint Score-12, and 84% for ACL-Return to Sport after Injury scale; all < .001). Preoperative risk factor analysis only revealed younger age as negatively impacting ipsilateral ACL failure, as the odds decreased by 12.5% for each year of increasing age ( = .002).

CONCLUSION

Sustained clinical and functional outcomes for ACLPR were observed between short-term and midterm follow-up, with failure rates of 11.5% and 15.9%, respectively. Although younger age was an important risk factor for ipsilateral ACL failure, with a high failure rate of 37.0% in patients aged ≤21 years at short-term follow-up, no additional failures were observed at midterm follow-up. In contrast, patients aged >21 years experienced modest failure rates, increasing from 3.5% at short-term follow-up to 8.6% at midterm follow-up, with no significant change.