Effects of Viscosupplementation on Tribological Behaviour of Articular Cartilage

Osteoarthritis (OA) is one of the frequent conditions in the orthopaedic practice. The number of OA patients is increasing and the efficacy of the current treatment methods is relatively low in terms of slowing or even preventing of the disease progression. The current research suggests that the lubrication function of the cartilage depends on its articulating surfaces. These surfaces are characterized by extracellular matrices with a three-dimensional porous structure that ensures a proper lubrication regime to protect the surface against the wear. Viscosupplementation is one of the possible treatments to slow the OA progression. This therapeutic intervention is frequently used in the clinical practice for the knee osteoarthritis. Viscosupplementation can, to a certain extent, supplement the lubrication ability of the cartilage by doping the hyaluronic acid (HA) and thus delay the degradation. However, selection of a proper viscosupplement remains a challenge, both in terms of the correct evaluation of the HA properties and their interaction with different stages of the OA. The viscoupplements differ in their HA molecular weight that may influence the CoF development from both the short term and the long-term perspective. The aim of this study is to analyze the coefficient of friction (CoF) between the real surfaces of a bovine cartilage after applying viscosupplements. The experiments were conducted on a pin-on-plate tribometer with a real bovine cartilage to simulate the lubrication regimes of a human joint. The model joint was doped with 4 different commercially available viscosupplements with different molecular weights and cross-linking of the HA. The OA damage was simulated by using a model synovial fluid with a concentration that corresponds to an OA patient. A compression of the cartilage surface was observed during the experiment and the interstitial fluid drained away from the porous cartilage structure. This, in combination with a migrating contact area (MCA), led the synovial fluid (SF) to mix with the viscosupplement. Decrease in the CoF was observed after the application of the viscosupplements with an increasing molecular weight. This was observed under a functional boosted cartilage lubrication regime, what suggests that the viscosupplementation yields the benefits especially for the conditions where the cartilage is not substantially damaged by the OA