Abstract
INTRODUCTION: Posterior shiny corner lesions (PSCLs) have been reported to be useful for the early diagnosis of medial meniscus posterior root tears (MMPRTs) in surgical patients. However, the usefulness of PSCLs in outpatients, particularly regarding the optimal timing of magnetic resonance imaging (MRI) examinations after injury, remains unknown. We hypothesized that PSCLs would normally be observed in patients with MMPRTs within one month of injury. MATERIALS AND METHODS: This study included 144 patients with knee pain who visited our hospital between January 2021 and May 2023. MRI findings within and after one month were examined. Fisher's exact test was performed for PSCLs, cleft signs, ghost signs, radial tear signs, bone cysts, and medial meniscus extrusion (MME), which are findings used for the diagnosis of MMPRTs. Time-dependent receiver operating characteristic (ROC) curve analysis was performed for each MRI finding. A binomial logistic regression analysis was performed for age, sex, PSCL, ghost sign, and MME. RESULTS: PSCLs were observed on 82.6% of the MRI scans within one month, but the positivity rate decreased after one month. After one month, a high percentage of patients had cleft signs and ghost signs. The results of a time-dependent ROC curve analysis showed that the PSCL had better diagnostic ability than the cleft sign, ghost sign, radial tear sign, and MME at a relatively early stage. Additionally, the area under the curve (AUC) of PSCL peaks around 35 days and then declines, reaching 0.8 or less around 40 days. On the other hand, the AUC of the cleft sign and ghost sign began to increase around 30 days after injury, and it exceeded 0.8 after approximately 100 days. The results of the binomial logistic regression analysis revealed significant PSCLs and ghost signs. Independent associations between the PSCL, or ghost sign, and the MMPRT were demonstrated. CONCLUSION: This study suggests that PSCLs have a superior diagnostic capability for MMPRT during the early stages of injury compared with other MRI findings in outpatients. In particular, PSCLs have a high positivity rate within one month after injury and a high diagnostic capacity up to 40 days after injury.