Reference Point Indentation of Human Trabecular Bone Treated with Bisphosphonates for Varying Durations

OF THESIS REFERENCE POINT INDENTATION OF HUMAN TRABECULAR BONE TREATED WITH BISPHOSPHONATES FOR VARYING DURATIONS Reference point indentation (RPI), a novel form of micro-indentation, quantifies RPI material parameters which correlate with modulus, yield stress, strength, or toughness. Information linking bisphosphonate treatment length with the material properties of osteoporotic trabecular bone is needed to improve patient treatment. The objectives of this study were to: 1) determine if RPI can be used to successfully evaluate human trabecular bone and if so, determine an optimized test method for using RPI on trabecular bone, and 2) use this method to determine if any RPI parameters are related to the duration of bisphosphonate treatment. Indentation using a 4 N applied force for 5 cycles was determined to be optimal and used to indent trabecular bone samples from 44 post-menopausal, osteoporotic female patients treated with bisphosphonates for varying (0.8 to 14 years) durations. Considering patient age and calcium supplementation use as covariates, six RPI parameters were significantly (p<0.05) related to BP treatment duration. These results show that the duration of BP treatment is associated with declining RPI-parameters in human trabecular bone. Given prior findings linking these RPI parameters with established material parameters, the present findings suggest that increasing duration of BP treatment is associated with declining trabecular bone material properties.