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

Abstract

Background: An increase has been seen in the number of studies of anterior cruciate ligament reconstruction (ACLR) that use magnetic resonance imaging (MRI) as an outcome measure and proxy for healing and integration of the reconstruction graft. Despite this, the MRI appearance of a steady-state graft and how long it takes to achieve such an appearance have not yet been established. Purpose: To establish whether a hamstring tendon autograft for ACLR changes in appearance on MRI scans between 1 and 2 years and whether this change affects a patient’s ability to return to sports. Study Design: Case series; Level of evidence, 4. Methods: Patients with hamstring tendon autograft ACLR underwent MRI and clinical outcome measures at 1 year and at a final follow-up of at least 2 years. MRI graft signal was measured at multiple regions of interest using oblique reconstructions both parallel and perpendicular to the graft, with lower signal indicative of better healing and expressed as the signal intensity ratio (SIR). Changes in tunnel aperture areas were also measured. Clinical outcomes were side-to-side anterior laxity and patient-reported outcome measures (PROMs). Results: A total of 42 patients were included. At 1 year, the mean SIR for the graft was 2.7 ± 1.2. Graft SIR of the femoral aperture was significantly higher than that of the tibial aperture (3.4 ± 1.3 vs 2.6 ± 1.8, respectively; P = .022). Overall, no significant change was seen on MRI scans after 2 years; a proximal graft SIR of 1.9 provided a sensitivity of 96% to remain unchanged. However, in the 6 patients with the highest proximal graft SIR (>4) at 1 year, a significant reduction in signal was seen at final follow-up ( P = .026), alongside an improvement in sporting level. A significant reduction in aperture area was also seen between 1 and 2 years (tibial, –6.3 mm2, P < .001; femoral, –13.3 mm2, P < .001), which was more marked in the group with proximal graft SIR >4 at 1 year and correlated with a reduction in graft signal. The patients had a high sporting level; the median Tegner activity score was 6 (range, 5-10), and a third of patients scored either 9 or 10. Overall, PROMs and knee laxity were not associated with MRI appearance. Conclusion: In the majority of patients, graft SIR on MRI did not change significantly after 1 year, and a proximal graft SIR <2 was a sensitive indicator for a stable graft signal, implying healing. Monitoring is proposed for patients who have a high signal at 1 year (proximal graft SIR >4), because a significant reduction in signal was seen in the second year, indicative of ongoing healing, alongside an improvement in sporting level. A reduction in tunnel aperture area correlated with a reduction in graft SIR, suggesting this could also be a useful measure of graft integration.

Preserving the Semitendinosus Distal Attachment Is Associated With Improved Graft Remodeling After ACL Reconstruction

“…In an MRI study of 250 patients, a 1-point increase in the SIR was associated with a 40% increase in the risk of graft failure. In an MRI study at 1 and 2 years, Putnis et al 44 found no major change in the SIR. This suggests that the ligamentization process mainly occurs during the first year and that it is directly related to the risk of the graft failing.…”

Morphological Changes in the Tibial Tunnel After ACL Reconstruction With the Outside-In Technique and Adjustable Suspensory Fixation

“…29 Naraoka et al 20 demonstrated that there was no association between tunnel enlargement and graft integration grade. In contrast, Putnis et al 23 showed that tunnel contraction was positively correlated with graft signal intensity, and they reported that this could be a useful indicator of graft integration. In the present study, a similar correlation was found between graft tunnel volume and intratunnel graft SNQ as well as integration grade in the tibial tunnel.…”

LESS score and isometric lower limb strength after ACL reconstruction in female handball players

“…MRI evaluation of the integration of the graft should also be considered [30][31][32]. Although the development of surgical techniques and improved rehabilitation protocols have been remarkable, the repercussions of an ACL injury are still significant.…”