Abstract
In osteoarthrosis, pathological features of articular cartilage are associated with degeneration and nanomechanical changes. The aim of this paper is to show that indentation-atomic force microscopy can monitor wear-related biomechanical changes in the hip joint of patients with osteoarthritis. Fifty patients (N = 50), aged 40 to 65, were included in the study. The mechanical properties and the submicron surface morphology of hyaline cartilage were investigated using atomic force microscopy. Measurements of the roughness parameters of cartilage surfaces were performed, including the arithmetic average of absolute values (Ra), the maximum peak height (Rp), and the mean spacing between local peaks (S). The arithmetic mean of the absolute values of the height of healthy cartilage was 86 nm, while wear began at Ra = 73 nm. The maximum changes of values of the roughness parameters differed from the healthy ones by 71%, 80%, and 51% for Ra, Rp, and S, respectively. Young’s modulus for healthy cartilage surfaces ranged from 1.7 to 0.5 MPa. For the three stages of cartilage wear, Young’s modulus increased, and then it approached the maximum value and decreased. AFM seems to be a powerful tool for surface analysis of biological samples as it enables indentation measurements in addition to imaging.
Highlights
Articular cartilage is the connective tissue of diarthrodial joints and plays specific biomechanical functions, i.e., lubrication, load-bearing, and energy dissipation [1,2]
The aim of this paper is to show that indentation-atomic force microscopy can monitor wear-related biomechanical changes in the hip joint of patients with osteoarthritis
Morphology of the areas of human cartilage not affected by osteoarthritis were investigated
Summary
Articular cartilage is the connective tissue of diarthrodial joints and plays specific biomechanical functions, i.e., lubrication, load-bearing, and energy dissipation [1,2]. Healthy articular cartilage consists of a small number of cells (chondrocytes), water (within a range from 66% to 80%), solid components (20%–34%) including 5%–6% of hydroxyapatite, type-II collagen (48%–62%), and proteoglycan (22%–38%) [3,4,5,6]. Pathological features of articular cartilage are associated with its degeneration, surface morphology, and biomechanical changes in its nanoscale structure, and may result in osteoarthritis. Increased synthesis of collagen, non-collagen proteins, proteoglycans, hyaluronate, and desoxyribonucleic acid can be detected in its deeper layers [7]. The prevalence of OA increases with age; the highest incidence is observed among women over 45 years old [8]. According to the general classification of the American Society of Rheumatology, osteoarthritis ranks 4th among all the rheumatic diseases, affecting 80% of the European population aged 75 years and older [9]; among adults 60 years of age or older, over 10% of Materials 2020, 13, 2302; doi:10.3390/ma13102302 www.mdpi.com/journal/materials
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