Introduction

A meniscal tear is a very common injury caused by a traumatic event and /or as a result of degeneration. Pain and dysfunction of the knee are the main symptoms. Surgical and non-surgical treatment options are available; the optimal treatment is currently debated. To improve treatment selection, a sensitive non-invasive imaging technique is needed. T2-mapping is a promising quantitative MRI technique that is suggested to detect early meniscal degeneration by measuring proton mobility expressed in relaxation time. However, no research has been done to validate meniscal T2-mapping compared to histopathology as the gold standard. Our aim is to study the correlation between T2-mapping relaxation time and the degree of histopathological degeneration in meniscal tissue.

Methods

In this prospective observational study 10 patients were included, both with degenerative and non-degenerative menisci. Traumatically torn meniscal tissue from five patients was collected during arthroscopic partial meniscectomies. Degenerative menisci from five patients were obtained during total knee replacement surgery. Histopathological analysis was performed using the Pauli score, a validated grading system involving the following subdomains: surface integrity, cellularity, matrix and collagen organisation, and proteoglycan staining intensity. All patients preoperatively underwent an MRI scan, including a T2-mapping sequence. MRI slices of meniscal regions, corresponding with the histopathology scored area, were analysed using an in-house developed post-processing software. Mean T2 relaxation times were calculated. The correlation between T2-mapping and histopathological degeneration was assessed using Spearman correlation tests. Our hypothesis was, that degenerative meniscal tissue has higher T2 relaxation times compared to meniscal tissue without degeneration.

Results

SECTION: T2-mapping relaxation time was found to correlate with the degree of histopathological degeneration in meniscal tissue (rs = 0.64, P = 0.001). Meniscal tissue with mild to moderate degeneration was found to have statistically significant higher T2 relaxation times compared to meniscal tissue without degeneration, 22.7 ± 3.0 ms and 18.2 ± 5.1 ms (P = 0.02) respectively.

Discussion

T2-mapping relaxation time correlates well with histopathological degeneration in meniscal tissue and is a promising quantitative imaging biomarker to estimate meniscal degeneration. A few limitations warrant consideration. The relatively small sample size: our results are exploratory and need to be confirmed by a larger cohort. Secondly of all, the time interval between the T2-mapping scan and collection of traumatically torn meniscal tissue was different between patients (mean 30 days, range 4-48 days), potentially influencing the correlation. Nevertheless, we observed a highly significant correlation between T2-mapping and the degree of histopathological degeneration.

Significance

This project addresses an important clinical problem, namely the need for a sensitive non-invasive imaging technique to detect meniscal degeneration, which is associated with knee OA, in an early stage. T2-mapping is such an imaging technique, and we found a promising correlation with histopathological findings as the gold standard to assess meniscal degeneration.