BioImplantable Bone Stress Sensor

The clinical management of skeletal trauma and disease relies on radiographic imaging to infer bone quality. However, bone strength does not necessarily correlate well with image intensity. There is a need for a safe and convenient way to measure bone strength in situ. This paper presents a new technique to directly measure bone strength in situ at a micro-level scale through a MicroElectroMechanical System (MEMS) sensor. The proposed MEMS stress sensor comprises an array of piezoresistive sensor "pixels" to detect stress across the interfacial area between the MEMS chip and bone with resolution to 100 Pa, in 1 sec averaging. The sensors are located within a textured surface to accommodate sensor integration into bone. From initial research, surface topography with 30-60 μm features was found to be conducive to guiding new cell growth. Finite element analysis has led to a sensor design for normal and shear stress detection.