Caractérisation multimodale de l’ostéointégration et du remodelage osseux en fonction de l’environnement

Abstract

Bone tissue development, particularly in the vicinity of an implant (osseointegration), is a multi-factorial phenomenon depending on the patient, the surgery and the properties of the implant. For a better understanding of osseointegration in order to optimize it, several approaches were used, both in vitro and in vivo. The objective of this study is to characterize osseointegration phenomena. To do so, two complementary approaches were adopted to study bone and its interface with an implant, while controlling the environment of bone tissue. First, an ex vivo methodology was adopted to study bone tissue. A perfusion bioreactor was conceived to characterize the development of large-sized bone samples (about 1 cm3) during a 10-week period. A bone culture was carried out and analyzed with X-ray microtomography (μCT). An analysis through registration of volume images from the beginning and the end of the culture allowed to point out the importance of environmental factors to initiate bone remodeling. Second, an in vivo implant model consisted of using a coin-shaped implant in titanium alloy to study osseointegration. Dressed with a PTFE crown, creating an empty bone chamber in contact with the implant, this model allows the differentiation of newly formed bone from mature bone situated outside the chamber. Neutron tomography was adopted to characterize bone tissue around the implant, and allowed to avoid artifacts obtained with metallic implants while using X rays. First, this technique was compared to histology, a reference technique in studying the bone implant interface. To do so, an image registration procedure was used to find the 2D neutron images corresponding to the histologic slices. Bone quantities in the bone chamber and in contact with the implant (BIC) were evaluated in the 2D images for both techniques. Following the comparative analysis, the implant bone chamber, imaged with neutron tomography, was analyzed in 3D to highlight a specific bone repartition in the vicinity of the implant. The comparative study with histology allowed to confirm the ability of neutron tomography to discriminate bone tissue, with a significant correlation between both modalities for bone quantity and BIC. Moreover, this technique was shown as sensitive to soft tissues, which can be differentiated from bone tissue in volume images. Tridimensional analysis of the bone volume delimited by the PTFE crown and the implant highlighted a bone repartition corresponding to contact osseointegration, meaning a bone growth from synthetic surfaces (here the implant and the PTFE crown). Combination of in vivo and ex vivo approaches with analysis techniques (histology, neutron tomography, X-ray μCT) have brought new keys in the understanding of bone tissue and its models adopted in research. Although complex to set up, ex vivo study allows to effectively isolate the effect of the studied factors. Moreover, new technologies to characterize bone, as neutron tomography, bring new perspectives to study the tissue, particularly in a context of osseointegration of implants.

Date	30 Mar 2021
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Yvan Petit (Supervisor) & Guillaume Haiat (Co-supervisor)