Smart orthopaedic implants: A targeted approach for continuous postoperative evaluation in the spine

Real-time health monitoring systems are emerging in diverse medical fields, tracking biological and physiological signals for direct feedback to the user. Orthopaedics is yet to adapt to innovative trends in health monitoring. Despite an evident entry point during orthopaedic surgeries, clinicians remain unable to objectively examine the structural integrity and biomechanics in the operated region through implantable sensors. As such, postoperative advice can be non-specific and poorly guided. This perspective discusses the clinical need for load-sensing implants that address biomechanical postoperative monitoring, taking the example of spinal interbody cages. Research has attempted to establish sensing approaches in different orthopaedic settings; however, they fail to meet mechanical sensing requirements or lack in vivo translatability, especially in the spine. Polymeric flexible sensors and Microelectromechanical Systems (MEMS) have favourable attributes aligned to the required features for in vivo load-sensing, although these approaches are yet to be tested extensively in orthopaedics. While inductive powering is promising, wireless energy transfer and telemetry are areas of ongoing research. This perspective proposes a thorough understanding of the relevant biomechanics to identify the pertinent sensing parameters, concurrent treatment of sensing and powering aspects, and utilisation of energy harvesting for sensing and data transmission. While sensing advancements have contributed to the rise of real-time health monitoring in other fields of medicine, orthopaedics has so far been overlooked. It is the application of these innovations that will lead to the development of a new generation of ‘smart’ implants for continuous postoperative evaluation.