The functional microstructure of tendon collagen revealed by high‐field MRI

Abstract

T2 was used in this study to assess tendon microstructure. Two unloaded digital extensor tendons were bent such that their long axes were imaged throughout 180° with respect to B0. T2-weighted images reveal periodic banding (∼200 μm) when tendons were oriented at ±55° with respect to B0. Five pairs of tendons were used to study the influence of load on T2W MRI: one tendon of each pair was loaded with a 7.8-N mass, and both tendons were fixed in formalin then imaged at 55° to B0. MRI banding was present in the unloaded, but not loaded, tendons. In unloaded tendons, polarized-light microscopy revealed collagen crimp with a periodicity similar to MRI. In loaded tendons, there was a strain-induced extinction of periodicity on both MRI and polarized-light microscopy. These studies confirm that crimp is detectable by high-field MRI and could serve as an in vivo index of physiological strains in collagenous tissues.