Abstract
Hyaluronic acid (HA) injections represent one of the most common methods for the treatment of osteoarthritis. However, the clinical results of this method are unambiguous mainly because the mechanism of action has not been clearly clarified yet. Viscosupplementation consists, inter alia, of the improvement of synovial fluid rheological properties by injected solution. The present paper deals with the effect of HA molecular weight on the rheological properties of its solutions and also on friction in the articular cartilage model. Viscosity and viscoelastic properties of HA solutions were analyzed with a rotational rheometer in a cone–plate and plate–plate configuration. In total, four HA solutions with molecular weights between 77 kDa and 2010 kDa were tested. The frictional measurements were realized on a commercial tribometer Bruker UMT TriboLab, while the coefficient of friction (CoF) dependency on time was measured. The contact couple consisted of the articular cartilage pin and the plate made from optical glass. The contact was fully flooded with tested HA solutions. Results showed a strong dependency between HA molecular weight and its rheological properties. However, no clear dependence between HA molecular weight and CoF was revealed from the frictional measurements. This study presents new insight into the dependence between rheological and frictional behavior of the articular cartilage, while such an extensive investigation has not been presented before.
Highlights
An articular cartilage is a kind of hyaline cartilage which covers sliding surfaces in large synovial joints
The results showed a strong dependency between the viscosity and molecular weight of Hyaluronic acid (HA)
The highest viscosity was measured for HA with a molecular weight of 2010 kDa and the lowest for 77 kDa HA over the whole range of shear rate
Summary
An articular cartilage is a kind of hyaline cartilage which covers sliding surfaces in large synovial joints (e.g., the hip or knee). The articular cartilage creates sliding surfaces with extremely low friction and minimal wear. It can absorb impact loads quite well. A solid phase is composed of an extracellular matrix from collagen fibrils and proteoglycans. According to the orientation of collagen fibrils, the cartilage structure can be divided into several layers: superficial, middle, deep and calcified zones [2]. Collagen fibrils are oriented tangentially to the cartilage surface in the superficial zone whereas they are mostly perpendicular to the surface in the deep zone. The collagen content is the highest in the superficial zone and decreases towards the deep zone. The proteoglycan content is the lowest in the superficial zone.
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