Scanning Electron Microscopic Studies of Extensor Tendon Degeneration in Rheumatoid Arthritis

Pathological alterations in human tendons

The present authors analyzed the pathological alterations of 1966 tendons examined in the National Institute of Traumatology, Budapest, during the past 18 years. The majority of cases proved to be tendinopathies (hypoxic-degenerative tendinopathy or calcific tendinitis, tendolipomatosis and mucoid degeneration) leading to tendon rupture. The incidence of tendon tumors, foreign bodies, infectious tendon diseases, and other pathological conditions was clearly lower. The methods of tissue preparation and of examination of tendon specimens were also evaluated. Light microscopy was sufficient for the diagnosis of pyogenic tendinitis, tumors, xanthoma, gout, and gangrene. In degenerative tendinopathies and alterations due to hereditary disease, electron microscopy was necessary. Polarization microscopy had a key role in examination of collagen structure and architecture, and identification of foreign bodies in the tendons. Enzyme histochemical and immunohistochemical examination were reliable but not absolutely necessary in the diagnosis of tendon pathology.

Fine structural alterations of collagen fibers in degenerative tendinopathy

Fine structural alterations of collagen fibers were analyzed in 29 ruptured tendons. The most frequent alterations were longitudinal splitting, disintegration, angulation, and the so-called "Knickdeformation" of the collagen fibers. All these phenomena were considered to be the consequences of stress fatigue and mechanical injuries of fibers.