Rotator Cuff Tear-induced Changes in Tendon Structure and Mechanics Measured by Quantitative Magnetic Resonance Imaging.

Introduction: Rotator cuff (RC) tears are prevalent degenerative injuries associated with progressive loss of shoulder function. Although MRI is routinely used for diagnosing RC tears, the relationship between imaging biomarkers and tendon mechanical function remains poorly understood. This study investigates whether quantitative MRI (qMRI), particularly T2 relaxation time, reflects structural and mechanical changes in supraspinatus tendons with RC tears.

Methods: Twenty-four human cadaveric supraspinatus tendons (10 intact, 14 torn) were analyzed. Mechanical testing was performed to assess structural and material properties. T2 mapping using a 9.4T MRI scanner was employed to determine relaxation times. Raman spectroscopy and multiphoton imaging were used to assess biochemical composition and collagen organization.

Results: Torn tendons showed significantly reduced stiffness (p = 0.035) and failure force (p = 0.015) compared to intact tendons. T2 relaxation times were significantly elevated in the torn group (23.7 ± 3.5 ms vs. 20.6 ± 3.3 ms; p = 0.035), with higher heterogeneity and 90th percentile values. T2 metrics correlated strongly with mechanical properties (stiffness: r_s = - 0.84, p = 0.002; failure force: r_s = - 0.86, p = 0.002) and tear area (r_s = - 0.79, p = 0.004). Raman spectroscopy showed reduced proline and hydroxyproline spectral biomarkers in torn tendons (p < 0.02), which correlated with mechanical weakening. Multiphoton imaging revealed significant collagen disorganization and damage in torn tendons.

Discussion: This study demonstrates that T2 relaxation time is a sensitive non-invasive biomarker of tendon mechanical health and collagen structure in RC tears. These findings support the clinical utility of qMRI in assessing tendon pathology and guiding treatment strategies.