CHAPTER 05 Remote Sensing of Forces in Orthopaedic Implants: An Overview

The direct measurement of forces from within orthopaedic implants is seen as a ‘gold standard’ and is useful for furthering our knowledge of the biomechanics of the musculoskeletal system as well as for implant design and testing, physiotherapy, fracture fixation and for validating mathematical models so that they are empowered to their best advantage. This talk will present these objectives and then focus on the challenges in the design of such implantable devices, and in particular the electrical design of some implants designed and built at UCL Stanmore over the last 30 years, both the implanted and external circuits. Options for calibrating such devices will be presented, together with a selection of measurements recorded from a few instrumented implants, showing broad agreement between measured forces and those determined from even simple mathematical models during human gait. Factors affecting longevity of such implants in vivo will be discussed.