Abstract
Hallux rigidus is a degenerative condition of the first metatarsophalangeal joint (MTPJ) characterized by progressive cartilage loss, pain, and restricted motion. Conventional surgical treatments such as arthrodesis eliminate joint mobility, while existing metallic, ceramic, and polymeric implants often fail to replicate the compliant, viscoelastic response of native cartilage. This mechanical mismatch increases interfacial stress and accelerates degeneration of the opposing cartilage. Synthetic cartilage implants aim to preserve motion, but their long-term performance remains inconsistent, with complications such as subsidence, migration, and persistent pain. Liquid crystal elastomers (LCEs) are a promising class of soft, tunable polymers that combine elastomeric elasticity with liquid-crystalline order. Their molecular architecture enables cartilage-level stiffness, reversible deformation, and energy dissipation through stress-induced mesogen reorientation. This study investigates an LCE-based hemiarthroplasty implant designed to mimic the mechanical behavior of articular cartilage. An anatomically simplified numerical model of the MTPJ incorporating the implant was developed, and experimentally derived, rate-dependent mechanical parameters were assigned to the LCE cap. Finite element simulations were conducted to evaluate stress distribution within the joint under loading conditions representative of the push-off phase of gait. The performance of the LCE implant was compared with cobalt-chromium and ultra-high-molecular-weight polyethylene materials. Results show that the LCE implant undergoes adaptive deformation under load, increasing effective contact area and reducing localized stress concentrations at the cartilage-implant interface. This promotes more uniform load transfer across the joint and suggests that LCE-based implants may mitigate long-term cartilage degeneration and improve functional outcomes compared with rigid implant materials.