Influence of Age on Signal Intensity of Magnetic Resonance Imaging and Clinical Outcomes in Double-Bundle Anterior Cruciate Ligament Reconstruction: Comparisons Among Different Age Groups.

BACKGROUND: Thus far, the clinical results of anterior cruciate ligament (ACL) reconstruction have been observed to be comparable between young and older patients. In contrast, age-related changes in the structural and mechanical properties of tendons used for autografts have been described. However, age-related changes associated with graft maturation remain poorly understood. HYPOTHESES: The hypotheses of this study were that (1) clinical outcomes after ACL reconstruction would be comparable between younger and relatively older patients and (2) younger patients would show lower signal intensity changes on magnetic resonance imaging scans indicative of graft maturation that would be better than that in relatively older patients. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: We retrospectively evaluated 236 patients who underwent double-bundle ACL reconstruction via the outside-in technique using hamstring autograft between January 2012 and December 2015. The patients were categorized by age into 3 groups: <20 years old, 20 to 39 years old, and ≥40 years old. Clinical outcomes were evaluated using the subjective International Knee Documentation Committee (IKDC) score, Tegner activity scale, Lysholm score, and objective assessment of joint laxity 24 months after surgery. In addition, graft maturation was evaluated using magnetic resonance imaging-derived measures of the signal intensity ratio (SIR) at 3, 6, 12, and 24 months postoperatively. Clinical outcomes and graft maturation were compared among the 3 groups. RESULTS: The SIR of both bundles increased from 3 months to 12 months and decreased by 24 months, showing the same tendency in all groups. No significant difference was found in the SIR among the 3 groups at any time point (P > .05). The IKDC score was significantly lower in the ≥40-year group than in the <20-year group (P < .01). In contrast, no significant differences were noted in other clinical outcomes. CONCLUSION: Patients aged ≥40 years exhibited lower IKDC scores compared with younger patients, although the results of graft maturation were comparable.