Smart Implants: Science Meets Technology

Background: Radiology is the gold standard to show bone wound healing and osseointegration of implants despite bone growth and regeneration in a dynamic process. Even histology provides only a glimpse on the activity or inactivity of osteoblasts, osteoclasts and osteocytes in bone.

Objective: The goal of this study was to test a novel sensing technology which is based on bioimpedance which in due course may allow the monitoring of the osseous healing processes in an uninterrupted manner.

Methods: In a rabbit calvaria, a full thickness sub-critical size defect was created large enough to locate the biosensor which was mounted to a titanium mesh into the defect. The mesh was then fixed to the adjacent bone with micro-screws. Measurements were performed every 3 or 4 days during a period of 6 weeks and spectroscopic analysis of the sensor signals were archived for later analyses. After 6 weeks the bone defects together with the biosensor was explanted and examined by means of micro-CT and histology. Serial analysis of the impedance spectroscopic examinations was performed by firstly fitting the data gathered during defect healing to a Cole-Cole equation. Thereafter the results were compiled, and the hereby converted spectra revealed gross changes in material densities during healing.

Findings: Terminal analyses by means of micro-CT as well as histology demonstrated incomplete yet ongoing osseous healing as the defect was filled with both connective tissue as well as newly formed bone. Furthermore no obvious signs for inflammation were observed indicating that the implanted biosensor is biocompatible.

Conclusions: Our results on dielectric spectroscopy may serve as a potential method for close continuous monitoring of bone wound healing in craniomaxillofacial and oral surgery in the future

Funding: Translational Research Project ‘Smart Implants - Monitoring of osseous healing and bone remodelling in vivo’.