Shear-Wave Elastography for Assessing the Histological Characteristics of Torn Rotator Cuff Tendons.

BACKGROUND: Shear wave elastography (SWE) is an imaging modality for assessing torn rotator cuff tendons applicable to both the preoperative and postoperative setting. SWE values increase following surgical repair, and lower values have been associated with factors linked to impaired tendon healing, including increasing age and greater tear size. However, the relationship between SWE and the tendons underlying histological characteristics remains unclear. This study therefore aimed to determine whether SWE values were associated with tendon histological features assessed by the Bonar score in torn rotator cuffs. METHODS: The stiffness (kPa) of the supraspinatus tendon was assessed pre-operatively using SWE. Samples were collected intraoperatively from the torn edge of the supraspinatus tendon in both partial and full thickness tears. Sections were stained with Hematoxylin and Eosin to assess tenocyte morphology, cellularity, vascularisation and collagen organization. Sections were also stained with Alcian blue (pH2.5) for identification of areas rich in glycosaminoglycans. RESULTS: Twenty-two torn supraspinatus tendon samples were analysed. Tendons exhibiting mixed hypercellular and hypocellular regions demonstrated significantly higher SWE values than uniformly hypercellular tendons (Mann-Whitney U = 89.0, Z = 2.04, p = 0.04). A Jonckheere Terpstra test demonstrated a significant monotonic increase in SWE values with increasing collagen disorganisation (Z = 2.67, p = 0.01). A secondary analysis of SWE values demonstrated a moderate positive correlation with cellularity grading (ρ = 0.45, p = 0.04) and collagen grading (ρ = 0.56, p = 0.02). No significant associations were observed between SWE values and tenocyte morphology, ground substance, vascularity, or overall Bonar score. CONCLUSION: Shear wave elastography demonstrated associations with specific histopathological features of torn supraspinatus tendons, with greater measured stiffness observed in tendons exhibiting mixed hyper- and hypocellularity and increased collagen disorganisation. These findings support SWE as a potential non-invasive marker of specific histopathological features in the supraspinatus tendon.