Ion-Selective Sensors for Orthopaedic Applications: A Systematic Review

Sensors are an established driver of diagnostics and prevention in the medical field, including orthopaedics. Today, the subclass of ion-selective sensors (ISSs) is on the leading edge due to its advantages, enabled by technological advancements in manufacturing, such as miniaturization, precision, accuracy, specificity, a wide measuring scale, ease of use, flexible operating conditions, and measuring speed. While ISSs' impact on environmental and health fields is already the subject of investigation, it still needs to be analysed specifically in orthopaedics, which is the aim of this Review. A PubMed and Scopus search was performed using the keywords "ion", "sensor", "electrodes", "selective", "musculoskeletal", "implant", "joint replacement", and "orthopaedic"; after systematic screening, 44 studies were included in the synthesis. First, studies were classified based on the target ion. Only a few papers treated applications specifically in orthopaedics, confirming that ISSs are still largely an unexplored frontier here. However, all of the studies targeted ions with a role also in musculoskeletal pathophysiology, thus relative ISSs could have a potential impact on orthopaedic diagnosis and treatment. Then, when described by the papers, ISSs' technological solutions were systematically evaluated. Finally, the main ISSs development targets for reaching orthopaedic clinical application were highlighted, including biocompatibility (e.g., implantability), long-term stability, calibration, and validation. Overcoming these challenges will enable ISSs to progress from laboratory prototypes to clinically viable tools, supporting the advancement of next-generation sensorised prostheses, fixation devices, and surgical instruments, and paving the way for predictive and personalised orthopaedic medicine.