T₂ mapping of the meniscus is a biomarker for early osteoarthritis

To evaluate in vivo T₂ mapping as quantitative, imaging-based biomarker for meniscal degeneration in humans, by studying the correlation between T₂ relaxation time and degree of histological degeneration as reference standard.

In this prospective validation study, 13 menisci from seven patients with radiographic knee osteoarthritis (median age 67 years, three males) were included. Menisci were obtained during total knee replacement surgery. All patients underwent pre-operative magnetic resonance imaging using a 3-T MR scanner which included a T₂ mapping pulse sequence with multiple echoes. Histological analysis of the collected menisci was performed using the Pauli score, involving surface integrity, cellularity, matrix organization, and staining intensity. Mean T₂ relaxation times were calculated in meniscal regions of interest corresponding with the areas scored histologically, using a multi-slice multi-echo postprocessing algorithm. Correlation between T₂ mapping and histology was assessed using a generalized least squares model fit by maximum likelihood.

The mean T₂ relaxation time was 22.4 ± 2.7 ms (range 18.5-27). The median histological score was 10, IQR 7-11 (range 4-13). A strong correlation between T₂ relaxation time and histological score was found (r_s = 0.84, CI 95% 0.64-0.93).

In vivo T₂ mapping of the human meniscus correlates strongly with histological degeneration, suggesting that T₂ mapping enables the detection and quantification of early compositional changes of the meniscus in knee OA.

• Prospective histology-based study showed that in vivo T ₂ mapping of the human meniscus correlates strongly with histological degeneration. • Meniscal T ₂ mapping allows detection and quantifying of compositional changes, without need for contrast or special MRI hardware. • Meniscal T ₂ mapping provides a biomarker for early OA, potentially allowing early treatment strategies and prevention of OA progression.