Evaluation of Graft Ligamentization by MRI After Anterior Cruciate Ligament Reconstruction

Abstract

Background: The tendon graft used in anterior cruciate ligament reconstruction (ACLR) undergoes “ligamentization” after implantation, and the reported length of this process varies from 6 to 48 months. Some grafts have ruptured at subsequent follow-up evaluations. Although the progress of graft ligamentization can be followed with postoperative magnetic resonance imaging (MRI) for reassessment, it is not known whether a delay in ligamentization (as reflected by a higher signal of the graft) is associated with an increased chance of subsequent graft rupture. Hypothesis: Signal intensity of the graft on reassessment MRI (signal-noise quotient [SNQ]) would be associated with the incidence of future graft rupture at subsequent follow-up. Study Design: Case-control study; Level of evidence, 3. Methods: A total of 565 ACLRs with intact graft on first-time reassessment MRI after surgery were followed for a mean period of 67 months. The rates of 1-year and 2-year follow-up were 99.5% and 84.5%, respectively. The signal intensity of the intact graft on the first-time reassessment MRI was evaluated (1) quantitatively by the SNQ and (2) qualitatively with the modified Ahn classification. Among the 565 ACLRs, 23 additional graft ruptures developed during a time interval of 7 months to 9 years after the surgery. Results: Higher SNQ was associated with increased chance of subsequent graft rupture (SNQ 7.3 ± 6 for subsequent graft rupture vs 4.4 ± 4 for grafts without subsequent rupture; P = .004, Mann-Whitney U test). The other important confounders that were associated with increased chance of graft rupture were younger age at the time of ACLR ( P < .001) and longer follow-up time ( P = .002). Multiple linear regression showed that all 3 factors (higher SNQ, younger age, and longer follow-up) were independent predictors of graft rupture (SNQ, P = .03; age, P < .001; follow-up, P = .012). When the reassessment MRI was performed in the second year after ACLR, the odds ratio of future graft rupture of a heterogeneous hyperintense graft when compared with a homogeneous hypointense graft was 12.1 (95% CI = 2.8 to 52.6) P < .001, Fisher exact test). Conclusion: Higher signal intensity of the intact graft on reassessment MRI (higher SNQ and heterogeneous hyperintense graft) was associated with increased chance of subsequent graft rupture.

Evaluation of Graft Maturation by MRI in Anterior Cruciate Ligament Reconstruction With and Without Concomitant Anterolateral Ligament Reconstruction

“…One of the most commonly utilized noninvasive methods of examining the maturity of the ACLR graft is the SNQ, 17 , 20 , 22 , 26 , 29 and it is considered suitable for comparing data within the same cohort. 29 However, no study has confirmed that the SNQ is a reliable research tool for comparing results among different studies.…”

“…One of the most commonly utilized noninvasive methods of examining the maturity of the ACLR graft is the SNQ, 17 , 20 , 22 , 26 , 29 and it is considered suitable for comparing data within the same cohort. 29 However, no study has confirmed that the SNQ is a reliable research tool for comparing results among different studies. Hence, the discussion arising from the comparison of the SNQ of the ACL graft in SB-ACLR/ALLR between the present study and the reported data in the literature 5 , 26 needs to be interpreted with caution.…”

“…The degree of ligamentization in the primary ACLR graft can be influenced by various factors, such as the duration since index surgery, 20 the presence of graft impingement, 29 the activity level of the patient, 17 the orientation of the implanted graft, 22 and concomitant ALLR. 5 , 26 The differences in the reported SNQs of the ACL graft in SB-ACLR/ALLR among the present study and those of Rojas et al 26 and Cavaignac et al 5 suggest that concomitant ALLR might not be the most important factor affecting the SNQ of the ACL graft.…”

“… 5 , 26 The differences in the reported SNQs of the ACL graft in SB-ACLR/ALLR among the present study and those of Rojas et al 26 and Cavaignac et al 5 suggest that concomitant ALLR might not be the most important factor affecting the SNQ of the ACL graft. Other confounders 17 , 20 , 22 , 29 may be more important in determining the degree of ligamentization and healing of the graft after SB-ACLR. These include time from surgery, 20 , 29 graft size, 22 graft bending angle, 22 and the activity level of the patient.…”

Graft impingement increases anterior cruciate ligament graft signal more than acute graft bending angle: magnetic resonance imaging‐based study in outside‐in anterior cruciate ligament reconstruction

“…The success or failure of ACLR depends on the biological process of graft healing; however, graft impingement at the intercondylar notch interferes with graft healing and is a major concern in ACLR failure [30]. It is clear that graft impingement may lead to marked increases in signal intensity, graft degeneration, and, eventually, re‐rupture [30, 40].…”