Magnetic Resonance Imaging 1 Year After Hamstring Autograft Anterior Cruciate Ligament Reconstruction Can Identify Those at Higher Risk of Graft Failure: An Analysis of 250 Cases

Abstract

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.

Regional Differences in Anterior Cruciate Ligament Signal Intensity After Surgical Treatment

“…Among studies investigating ACL graft structure and remodeling using MR imaging, some have reported signal measurements from different locations of the ACL graft. [14][15][16]18,21 Li et al [14][15][16] utilized the signal-to-noise quotient (SNQ), another method to normalize graft signal intensity, at the femoral, middle, and tibial regions from a single midsagittal slice. While their results showed regional differences in SNQ, [14][15][16] none of the studies conducted statistical comparisons of average SNQ among the 3 regions.…”

“…Their results suggested differences in average T 2 * measurements between the proximal half and distal half of the grafts, which were not statistically compared. Most recently, Putnis et al 21 used discrete 2-dimensional measurements to investigate regional differences in relative ACL graft to posterior cruciate ligament signal intensity ratio (SIR) in reconstructed knees 1 year after surgery. They showed significant differences in graft SIR, with the highest signal in the middle region and the lowest in the femoral aperture.…”

“…Previous studies often used 2-dimensional ROIs to measure ACL signal in a single slice or across several slices. [14][15][16][17]21 Other studies have used the ACL signal intensity (ie, median or mean) across the 3dimensional geometry of the ACL. 4,13,20,26 However, little is known about signal variations across the ACL and how they may influence MR-based assessments of ACL healing.…”

Magnetic Resonance Imaging Assessment of Hamstring Graft Healing and Integration 1 and Minimum 2 Years after ACL Reconstruction

“…35 In the present study, 1 patient was excluded for graft rupture, the 1-year MRI scan demonstrated a high proximal graft signal, which has previously been shown to correlate with risk of rupture. 26 In this series, KT-1000 arthrometer measurements were not correlated with graft MRI signal at 1 year or signal change thereafter and had no correlation with PROMs at any time point. Currently, KT-1000 arthrometry is still being used to demonstrate a difference between laxity of healthy and operated legs, with \3 mm difference historically described as an indicator for a stable knee.…”

Randomized controlled trial of all-inside and standard single-bundle anterior cruciate ligament reconstruction with functional, MRI-based graft maturity and patient-reported outcome measures

“…According to our study, all-inside and standard ACLR exhibited the worst maturity in the middle graft region, followed by the graft near the femoral tunnel; the tibial side showed the best maturity. Putnis et al [ 26 ] determined that the graft signal near the tibial tunnel was significantly lower than that of the femoral side. As the middle region of the graft is the primary area subjected to distraction forces and is far from the tunnel, graft hematologic reconstruction may be slower than the two ends.…”