Morphological Modifications in Osteoarthritis: A Scanning Electron Microscopy Study

Abstract

The chondrocyte, the only cellular component of adult articular cartilage, plays a key role in the pathogenesis of osteoarthritis (OA). The evolution of this process is very slow: the first changes involve the cell-matrix morphofunctional unit known as chondron. In this study we analyzed the cartilage of 10 patients with primary osteoarthritis. The cartilage was retrieved during total knee replacement (TKR) and maxillofacial surgery procedures. All patients presented an osteoarthritis of at least grade III. The preparation of the specimens was made by taking cartilage from both well-preserved and macroscopically degenerated areas. Specimens underwent histological evaluation with conventional staining and ultrastructural analysis. Age appeared to be a high risk factor in the development of articular cartilage damages. Depth of injury was also found to be age-related as more extensive lesions were found in the elderly, either in the knee or in the mandibular condyle. Whatever the cause of possible damage, Scanning Electron Microscopy (SEM) observations showed that at the beginning most degenerative changes in articular cartilage involved the chondron unit, a concept first introduced by Benninghoff. These changes generally go through three phases. During OA progression all degenerative changes begin from the chondron, which is why it is extremely important to understand the molecular anatomy and physiology of this pericellular microenvironment and its form, function and failure in adult articular cartilage. It is also fundamental to understand the mechanism of adaptation of the cartilage and bone disruptions, given the physiological relationship between these tissues, essential to maintain normal joint structure and function.