Summary

Our study examined the characteristic findings to assess the meniscal healing status after meniscal repair on MRI T2 mapping and demonstrated that more than 5.2 msec decrease of objective T2 value and the existence of high T2 signal linear line on color mapping were the significantly characteristic findings between complete and incomplete healed meniscus by arthroscopic examination.

Abstract

Background

Conventional magnetic resonance imaging (MRI) has been shown to be valuable in diagnosing the primary meniscal injuries. However, the accuracy for evaluation in repaired menisci is low because high signal intensity can persist for many years following successful meniscal repair. To improve the accuracy of diagnosis of postoperative meniscal healing, MRI-T2 mapping recently have been developed as a qualitative MRI reflecting the increased water content, decreased concentration of proteoglycans, and the loss of collagen content and network integrity.

Purpose

The purpose of our study was to examine the effectiveness of MRI T2 mapping for assessing meniscal healing status that was confirmed by arthroscopic examination, comparing with conventional MRI.

Methods

Between 2012 and 2016, we enrolled 26 menisci of 24 knees that underwent meniscal repair concomitant with anterior cruciate ligament reconstruction, and later hardware removal, and could take MRI-T2 mapping at the primary and second surgery. The patients included 9 males and 15 females and mean age was 23.3 years old (range, 14-43 years). Conventional MRI was performed with a proton density fat saturation sequence. The signal change was diagnosed with Stoller and Crues 3-stage classification. T2 mapping was also taken with following setting; TR = 2100 msec, TE = 10, 20, 30, 40, 50, 60 msec, field of view = 16 cm, slice thickness = 3 mm, matrix = 352 × 352. Healing status of repaired meniscus was assessed using second-look arthroscopy at mean 13.8 months after primary surgery, based on criteria by Cannon. Between complete healed group (16 menisci) and incomplete/unhealed group (10 menisci), Crues classification in conventional MRI and the amount of T2 value change in the repaired meniscus from preoperatively to postoperatively were assessed. The receiver operator characteristic (ROC) curve of the amount of T2 value change was examined as a factor related to meniscal healing to set the cutoff value of the T2 change value as the objective variable. Finally, the red-colored linear line showing the higher T2 value at the repaired meniscus was assessed between two groups.

Results

In conventional MRI, all menisci showed Grade 3 preoperatively, and 5 of 16 complete group and 2 of 10 incomplete/unhealed group improved to grade 2 postoperatively. There was not a significant difference between two groups (p = 0.67). MRI-T2 mapping showed the amount of T2 value change was -7.5 msec in complete group and -2.7 msec in incomplete/unhealed group, there was a significant difference between two groups (p = 0.05). ROC curve analysis showed a cutoff T2 change of -5.2 msec was deemed best to separate meniscal healing, having a sensitivity of 81.2 %, a specificity of 80 % and odds ratio of 17.3. Moreover, red-colored linear line significantly more remained in incomplete/unhealed group (9 of 10) compared to complete group (5 of 16). (p = 0.005)

Conclusion

Conventional MRI couldn’t show characteristic finding between complete healed and incomplete/unhealed meniscus, however MRI-T2 mapping could diagnose the meniscal healing after repair accurately. Especially, -5.2 msec of T2 value change was the cutoff value for arthroscopic meniscal healing.