Biocompatibility, Durability, and Stability Assessment of an Unconstrained Metacarpophalangeal Joint Prosthesis With Zirconia (ZrO2) Crowns at Metacarpal and Polyether-Ether-Ketone at Proximal Phalanx.

PURPOSE: Rheumatoid arthritis often affects the metacarpophalangeal (MCP) joints, resulting in pain, deformity, and loss of hand function. In advanced disease, arthroplasty provides superior functional outcomes compared with arthrodesis. The development of small joint prostheses remains a challenge, particularly in terms of long-term durability, biocompatibility, and stability.

METHODS

A novel unconstrained MCP joint prosthesis was designed with zirconia crowns on the metacarpal side and polyether-ether-ketone (PEEK) crowns on the proximal phalanx, each supported by stainless steel stems. Biocompatibility was assessed histologically, whereas durability and stability were evaluated through mechanical testing, including measurements of surface roughness, weight and volume changes, and wear resistance. Functional stability was assessed by measuring in vivo flexion-extension and abduction-adduction ranges of motion and comparing them with those of conventional AISI 316L stainless steel prostheses.

RESULTS

The zirconia-PEEK prosthesis demonstrated superior biocompatibility with reduced macrophage infiltration and greater osteoblast activity. Mechanical testing revealed significantly lower wear and minimal changes in surface roughness, whereas functional testing demonstrated preserved joint mobility.

CONCLUSIONS

The unconstrained zirconia-PEEK MCP prosthesis demonstrated excellent biocompatibility, superior durability, and enhanced functional stability compared with stainless steel implants, supporting its potential as a promising alternative for MCP joint replacement.

CLINICAL RELEVANCE: This study demonstrates the potential of a zirconia-PEEK prosthesis for MCP joint replacement, potentially improving long-term functional outcomes for patients with advanced rheumatoid arthritis. Its superior biocompatibility and reduced wear characteristics may reduce complications, such as implant failure and the need for revision surgery, ultimately enhancing patient quality of life.