The rapid advancement of materials science has revolutionized total hip arthroplasty (THA), a critical orthopedic procedure aimed at restoring mobility and improving patient quality of life. This review investigates the evolution of biomaterials used in THA, analyzing their mechanical, biological, and chemical properties. The study outlines the transition from early natural materials to modern metals, polymers, and ceramics, highlighting their benefits and limitations in clinical applications. Particular emphasis is placed on the development of advanced materials such as highly cross-linked polyethylene (HXLPE), zirconia-toughened alumina (ZTA), and tantalum alloys (Ta), which demonstrate enhanced biocompatibility, wear resistance, and longevity. By examining emerging trends, including bioactive coatings and nanotechnology, this paper aims to provide a comprehensive understanding of current challenges and future directions in material selection for hip prostheses, ultimately aiming to minimize annual revision rates and improve long-term outcomes.

Total Hip Arthroplasty (THA) is a widely used surgical procedure to restore mobility and reduce pain in patients with hip joint disorders. Implant success and longevity are influenced by the selection of appropriate materials. This study presents a comprehensive literature review based on structured searches in Scopus and Web of Science, focusing on material selection criteria and methods in THA. The inclusion criteria targeted original studies and reviews addressing material properties, selection techniques, and clinical performance. A bibliometric analysis and keyword co-occurrence network were used to highlight major research themes. The review examines traditional materials such as Metal-on-Polyethylene (MoP), as well as advanced options like ceramics, composites, and Functionally Graded Materials (FGMs). Key challenges discussed include aseptic loosening, wear resistance, and stress shielding. Selection methodologies such as Multi-Criteria Decision-Making (MCDM), Weighted Properties Methods (WPM), and computational tools like Ashby charts and CES Selector are analyzed. The findings from international arthroplasty registries show that more than half of implant failures are linked to material-related factors. This study therefore aims to guide material selection processes in THA by aligning clinical performance with biomechanical and biological requirements, supporting improved implant outcomes and long-term surgical success. Future developments should focus on patient-specific solutions and continuous innovation.

This work presents a comprehensive experimental and analytical study of twisted and coiled artificial muscles (TCAMs) fabricated from three types of silver‐coated nylon 6,6 precursor fibers. The coupled thermo‐electromechanical response of these actuators is investigated through systematic characterization and a physics‐based analytical model. Built upon Castigliano's theorem, the model captures nonlinear contraction behavior with high accuracy while remaining computationally efficient compared to more complex formulations. Experimental validation demonstrates maximum contractions up to 19.3%, strongly influenced by precursor type and the applied prestrain. Beyond displacement, actuator performance is quantified through additional metrics. The specific mechanical work per cycle reaches values as high as 8 kJ kg ⁻¹ , highlighting the excellent work density achievable with minimal actuator mass. Conversely, electromechanical efficiency is found to be limited (0.15 ± 0.2% under optimized conditions), primarily due to thermal losses resulting from convection, radiation, and conduction. Time‐constant analysis reveals fiber‐dependent trends: Thinner fibers exhibit faster overall dynamics but slower heating than cooling, while thicker fibers display longer relaxation times due to their larger thermal mass. The combined experimental and analytical approach provides both a detailed understanding and a predictive tool for TCAMs, offering insights into their strengths and limitations for future integration into wearable and soft robotic systems.

High-strength polymer fibers such as nylon 6, nylon 6,6, and polyethylene are utilized to produce Twisted and Coiled Artificial Muscles (TCAMs) through the twisting of low-cost fibers. These artificial muscles exhibit high displacement and specific power, particularly under electrothermal actuation, which requires conductive elements. An experimental setup was developed to produce, thermally treat, and characterize commercially available nylon 6,6 fibers coated with silver. The results demonstrate that TCAMs can contract by over 15% and generate forces up to 2.5 N with minimal energy input. Key factors such as motor speed, applied load, and fiber geometry affect the overall performance.

Wearable robotic devices for rehabilitation and assistive applications face a critical challenge: discomfort induced by prolonged pressure at the human–robot interface. Conventional attachment systems with static straps or rigid cuffs frequently exceed pain tolerance thresholds, limiting clinical acceptance and patient adherence. This study presents a novel dynamic pressure modulation system using thermally activated Twisted and Coiled Artificial Muscles (TCAMs). The system integrates a lightweight lattice structure (0.1 kg) with biocompatible silicone coating incorporating two TCAMs fabricated from silver-coated nylon 6,6 fibers (Shieldex 235/36 × 4 HCB). Electrothermal activation via 2 A constant current induces axial contraction, dynamically regulating circumferential pressure from 0.05 kgf/cm² to 0.50 kgf/cm² within physiological comfort ranges. Experimental validation on a wrist-worn prototype demonstrates precise pressure control, rapid response (5–10 s), and thermal safety through 8 mm Ecoflex insulation. The system enables on-demand interface stiffening during robotic actuation and controlled pressure release during rest periods, significantly enhancing comfort and device tolerability. This approach represents a promising solution for clinically viable wearable robotic devices supporting upper limb rehabilitation and activities of daily living.