Viability of pHEMA Hydrogels as Coating in Human Synovial Joint Prosthesis

Abstract

In artificial joints, the bone part is usually substituted by a metallic component with high corrosion and strength resistance while the articular cartilage is replaced by a polymer. Use of thin layer of a compliant material acting as a bearing surface in human replacement joints has recently generated considerable interest. This work analyses the coating of a solid porous substrate of Ultra High Molecular Weight Polyethylene (UHMWPE) with a poly (2-hydroxyethyl methacr- ylate) (pHEMA) and two sIPN-type blends: pHEMA-cellulose acetate butyrate (CAB) and pHEMA-poly (ethyl methacrylate) (PEM) using 5.0% (w/w) of the crosslinking agent and 11.0% (w/w) of the linear reinforcing polymer. The wear resistance of the coating materials was evalu- ated in a TRI PIN ON DISK type equipment and the damage extension was characterized by Scanning Electron Microscopy (SEM). Preliminary qualitative tests were performed with the goal to identifying the hydrogels show the minimal required properties concerning wear strength. The pHEMA coating was completely destroyed during the first wear cycles, characterizing its low shear strength. By the other hand, after the complete experiment, both pHEMA-CAB and pHEMA- PEM blends showed a slightly improvement of abrasive and adhesive wear. This result indicates that the studied blends are promising materials to be used as compliant surfaces in joint prosthesis.