Accelerated bone bonding to calcium phosphate ceramic coated strain gauges: An experimental and computational study

Abstract

Calcium phosphate ceramic (CPC) coated strain gauges have been used for long term in vivo bone strain measurements but require 6 to 9 weeks for sufficient bonding. PepTite2000™, OP-1, TGF-β1, Ca₂SO₄·2H₂O, and an endothelial cell layer with and without TGF-β1 were examined as enhancements to accelerate bone to CPC bonding. Young male Sprague-Dawley rats were implanted with gauges for three weeks and calcein labeled. Following euthanasia, their femurs were explanted and mechanically tested. Histology was completed. Optical Coherence Tomography (OCT) was studied as an alternative to histology. A finite element analysis (FEA) examined bone to gauge strain transfer. Mechanical testing indicated increased sensing accuracy with TGF-β1 and OP-1 enhancements versus unenhanced gauges. PepTite2000™ and endothelial enhanced gauges displayed lower sensing accuracy and contained vasculature near CPC. TGF-β1 increased bonding with endothelial cells. Ca₂SO₄·2H₂O inhibited bone bonding. OCT unsuccessfully imaged bone to CPC contact. FEA identified geometric and material parameters for improved gauge design.