Wireless technologies are incorporated in implantable devices since at least the 1950s. With remote data collection and control of implantable devices, these wireless technologies help researchers and clinicians to better understand diseases and to improve medical treatments. Today, wireless technologies are still more commonly used for research, with limited applications in a number of clinical implantable devices. Recent development and standardization of wireless technologies present a good opportunity for their wider use in other types of implantable devices, which will significantly improve the outcomes of many diseases or injuries. This review briefly describes some common wireless technologies and modern advancements, as well as their strengths and suitability for use in implantable medical devices. The applications of these wireless technologies in treatments of orthopedic and cardiovascular injuries and disorders are described. This review then concludes with a discussion on the technical challenges and potential solutions of implementing wireless technologies in implantable devices.
Implantable wireless sensors have been used for real-time monitoring of chemicals and physical conditions of bones, tendons and muscles to diagnose and study orthopedic diseases and injuries. Due to the importance of these sensors in orthopedic care, a critical review, which not only analyzes the underlying technologies but also their clinical implementations and challenges, will provide a landscape view on their current state and their future clinical role. Areas covered: By conducting an extensive literature search and following the leaders of orthopedic implantable wireless sensors, this review covers the battery-powered and battery-free wireless implantable sensor technologies, and describes their implementation for hips, knees, spine, and shoulder stress/strain monitoring. Their advantages, limitations, and clinical challenges are also described. Expert commentary: Currently, implantable wireless sensors are mostly limited for scientific investigations and demonstrative experiments. Although rapid advancement in sensors and wireless technologies will push the reliability and practicality of these sensors for clinical realization, regulatory constraints and financial viability in medical device industry may curtail their continuous adoption for clinical orthopedic applications. In the next five years, these sensors are expected to gain increased interest from researchers, but wide clinical adoption is still unlikely.
27Mechanical loads exerted on the skeleton during activities such as walking are important regulators 28 of bone repair, but dynamic biomechanical signals are difficult to measure inside the body. The 29 inability to measure the mechanical environment in injured tissues is a significant barrier to 30 developing integrative regenerative and rehabilitative strategies that can accelerate recovery from 31 fracture, segmental bone loss, and spinal fusion. Here we engineered an implantable strain sensor 32 platform and measured strain across a bone defect in real-time throughout rehabilitation. We used 33 the sensor to longitudinally quantify mechanical cues imparted by a load-sharing fixation plate that 34 significantly enhanced bone regeneration in rats. We found that sensor readings correlated with the 35 status of healing, suggesting a potential role for strain sensing as an X-ray-free healing assessment 36 platform. This study demonstrates a promising approach to quantitatively develop and exploit 37 mechanical rehabilitation strategies that enhance bone repair. 38 39
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