Compliant Joint Reconstruction

Compliant Wrist Endoprosthesis

Advanced pan-carpal pathologies (e.g., giant cell tumors, post-traumatic osteoarthritis) and high-energy fractures cause devastating pain, driving many patients annually toward total wrist fusion (arthrodesis). Conventional wrist replacements lack durability and stability, making them unsuitable for younger, active patients. Total wrist fusion (WF), although common, severely restricts wrist mobility, leading to compensatory movements that can trigger secondary disabilities such as shoulder arthritis. Our objective is to bridge this gap by developing a novel wrist implant offering fusion-like stability while restoring mobility without the risks associated with conventional implants.

The novel endoprosthesis employs compliant mechanisms that move by bending and flexing rather than rolling, rubbing, or sliding. These frictionless, stable mechanisms eliminate critical failures, including subluxation, particle wear, and stress concentration. The core mechanism, a cross-axis flexural pivot (x-pivot), ensures inherent stability, completely preventing subluxation. Flexible elements distribute axial shocks and off-axis loads throughout the compliant structure, thereby avoiding stress concentration at bone-implant interfaces.

• Project Lead: Leonardo Ruffini
• Surgical Collaborator: Drs. Lauren E. Wessel and Nelson F. SooHoo (Orthopaedic Surgery, UCLA)
• Project Team: Brandon Peterson, Emilie Liao, Prof. Jonathan B. Hopkins