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Background: The combined influence of anatomic and operative factors affecting graft healing after anterior cruciate ligament (ACL) reconstruction within the femoral notch is not well understood. Purpose: To determine the influence of graft size and orientation in relation to femoral notch anatomy, with the signal/noise quotient (SNQ) of the graft used as a measure of graft healing after primary single-bundle ACL reconstruction. Study Design: Case series; Level of evidence, 4. Methods: A total of 98 patients with a minimum 2-year follow-up after primary single-bundle ACL reconstruction with hamstring tendon autografts were included. Graft healing was evaluated at 1 year on magnetic resonance imaging (MRI) scan as the mean SNQ measured from 3 regions situated at sites at the proximal, middle, and distal graft. Patient characteristics, chondropenia severity score, tunnel sizes, tunnel locations, graft bending angle (GBA), graft sagittal angle, posterior tibial slope (PTS), graft length, graft volume, femoral notch volume, and graft-notch volume ratio (measured using postoperative 3-T high-resolution MRI) were evaluated to determine any association with 1-year graft healing. The correlation between 1-year graft healing and clinical outcome at minimum 2 years was also assessed. Results: There was no significant difference in mean SNQ between male and female patients ( P > .05). Univariate regression analysis showed that a low femoral tunnel ( P = .005), lateral tibial tunnel ( P = .009), large femoral tunnel ( P = .011), large tibial tunnel ( P < .001), steep lateral PTS ( P = .010), steep medial PTS ( P = .004), acute graft sagittal angle ( P < .001), acute GBA ( P < .001), large graft volume ( P = .003), and high graft-notch volume ratio ( P < .001) were all associated with higher graft SNQ values. A multivariate regression analysis showed 2 significant factors: a large graft-notch volume ratio ( P = .001) and an acute GBA ( P = .004). The 1-year SNQ had a weak correlation with 2-year Tegner Activity Scale score ( r = 0.227; P = .026) but no other clinical findings, such as International Knee Documentation Committee subjective and Lysholm scores and anterior tibial translation side-to-side difference. Conclusion: The 1-year SNQ value had a significant positive association with graft-notch volume ratio and GBA. Both graft size and graft orientation appeared to have a significant influence on graft healing as assessed on 1-year high-resolution MRI scan.

Background: There is currently no analysis of 1-year postoperative magnetic resonance imaging (MRI) that reproducibly evaluates the graft of a hamstring autograft anterior cruciate ligament reconstruction (ACLR) and helps to identify who is at a higher risk of graft rupture upon return to pivoting sports. Purpose: To ascertain whether a novel MRI analysis of ACLR at 1 year postoperatively can be used to predict graft rupture, sporting level, and clinical outcome at a 1-year and minimum 2-year follow-up. Study Design: Case-control study; Level of evidence, 3. Methods: Graft healing and integration after hamstring autograft ACLR were evaluated using the MRI signal intensity ratio at multiple areas using oblique reconstructions both parallel and perpendicular to the graft and tunnel apertures. Clinical outcomes were assessment of side-to-side laxity and International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, Lysholm, and Tegner activity level scores at 1 year. Repeat outcome measures and detection of graft rupture were evaluated at a minimum of 2 years. Results: A total of 250 patients (42.4% female) underwent MRI analysis at 1 year, and assessment of 211 patients between 1 year and the final follow-up (range, 24-36 months) detected 9 graft ruptures (4.3%; 5 in female patients). A significant predictor for graft rupture was a high signal parallel to the proximal intra-articular graft and perpendicular to the femoral tunnel aperture ( P = .032 and P = .049, respectively), with each proximal graft signal intensity ratio (SIR) increase by 1 corresponding to a 40% increased risk of graft rupture. A cutoff SIR of 4 had a sensitivity and specificity of 66% and 77%, respectively, in the proximal graft and 88% and 60% in the femoral aperture. In all patients, graft signal adjacent to and within the tibial tunnel aperture, and in the mid intra-articular portion, was significantly lower than that for the femoral aperture ( P < .001). A significant correlation was seen between the appearance of higher graft signal on MRI and those patients achieving top sporting levels by 1 year. Conclusion: ACLR graft rupture after 1 year is associated with MRI appearances of high graft signal adjacent to and within the femoral tunnel aperture. Patients with aspirations of quickly returning to a high sporting level may benefit from MRI analysis of graft signal. Graft signal was highest at the femoral tunnel aperture, adding further radiographic evidence that the rate-limiting step to graft healing occurs proximally.