Electron microscope study of the advanced tendinopathy process of the long head of the biceps brachii tendon treated arthroscopically.

BACKGROUND: The ultrastructural alterations related to tendinopathy have not been well described. Most studies on this subject have been conducted many years ago and focused on material from the Achilles tendon. It was demonstrated that various comorbidities can affect ultrastructural alterations in the advanced tendinopathy; however, there is very little data on ultrastructural morphology in tendinopathies related to mechanical overload as in case of the long head of the biceps brachii tendon (LHBT). The aim was to determine intermediate ultrastructural alterations in middle to severe grade the LHBT tendinopathy and to establish if they are different than those reported in the literature for other anatomical locations.

MATERIALS AND METHODS: In this study we examined the ultrastructure of a series of the LHBT fragments arthroscopically removed due to tendinopathy and inve-stigated the morphology of tenocytes and collagen fibres in cases of the LHBT tendinopathy.

RESULTS: In pathological samples tenocytes were randomly scattered, their shape was round and the shape of nuclei was also disrupted. The presence of apoptotic--like features in tenocytes' nuclei was noted. All samples showed replacement of collagen fibrils by non-collagen extracellular matrix and diffuse collagen disorganisation.

CONCLUSIONS: It was demonstrated at ultrastructural level that the LHBT tendino-pathy is not simply a wear and tear phenomenon, since chronic degeneration of the extracellular matrix and tenocytes were present, similarly as in tendinopathies, in other anatomical locations. (Folia Morphol 2018; 77, 2: 371-377).