Signal noise quotient predicts graft rupture in anterior cruciate ligament reconstruction

Abstract

Introduction: The cumulative graft rupture rate of anterior cruciate ligament reconstruction (ACLR) is 7.9% at 10 years. There is no scientific method to predict which ACLR will rupture in subsequent follow-up. Increased graft signal (measured by signal-noise quotient, SNQ) in postoperation. Magnetic resonance imaging (MRI) is frequently used to monitor graft maturation in ACLR. However, it is not known whether SNQ helps predict future graft rupture. Methods: To test the hypothesis that increased SNQ was associated with subsequent graft rupture, a prospective MRI study was performed from 2007 to 2019 with postoperation MRI offered to all ACLR patients at or beyond 12 months after surgery. Signal intensity of intact graft was measured with SNQ. The incidence of subsequent graft rupture was documented. Result: In all, 536 ACLRs with intact graft on reassessment MRI (done at an average of 17 months after surgery) were recruited. The mean follow-up was 68 months. 22 graft ruptures occurred at a mean of 45 months (4%). Graft hyperintensity was noted in 43% and was associated with higher chance of subsequent graft rupture (p<0.001, odd ratio=9). SNQ was higher in the graft-rupture group (7.4 ± 6 vs 4.3 ± 4; p=0.004). Age (p<0.001) and longer follow-up (p=0.003) were also associated with graft rupture. Multiple regression showed that higher SNQ and younger age were independent predictors of future graft rupture (SNQ, p=0.011; age, p<0.001). Conclusion: In a prospective cohort of 536 ACLR with mean follow-up of 5.5 years, higher SNQ in reassessment MRI predicts graft rupture in subsequent follow-up.