Continuous Hyaluronic Acid Supply by a UHMWPE/PEEK Interlocking Scaffold for Metatarsophalangeal Joint Prosthesis Lubricating Applications

Wear is one of the main causes of prothesis failure in hemiarthroplasty of small joints such as the metatarsophalangeal joint, to which lubrication improvement is a promising solution. Inspired by the natural joint structure and lubrication mechanisms, we developed a novel composite strategy for metatarsophalangeal joint hemiarthroplasty. An ultrahigh-molecular-weight polyethylene (UHMWPE) lubrication layer is interlocked within a 3D-printed poly(ether ether ketone) (PEEK) scaffold, and hyaluronic acid (HA) is introduced for hydrophilic modification of the UHMWPE matrix. HA encapsulated in the matrix can consistently emerge to the friction interface and firmly form a boundary lubrication layer, consequently enhancing the lubrication of the UHMWPE component. The friction coefficient of the scaffolds could be as low as 0.041 under a joint-equivalent load and a low friction velocity. Besides, the tested samples demonstrate good <i>in vitro</i> and <i>in vivo</i> biocompatibility. The bone tissues around the implantation site can heal normally and achieve implant fixation within 6 weeks. Summarily, in this work, inspired by the natural "cartilage-and-subchondral bone" structure, a continuous HA supply was attained in a UHMWPE/PEEK interlocking scaffold. Such a composite shall provide an excellent combination of tribological properties and biocompatibility, thus hopefully being a candidate material for the next-generation hemi-implants for metatarsophalangeal arthroplasty.