Study of bone anisotropy in porous metal lic implants using birefringence and X ray scattering imaging

Sammanfattning

Metallic implants are commonplace in orthopaedic surgery. Recent advances inmanufacturing technology have made it possible to manufacture 3D printed porousimplants. This allows for designs that are mechanically tailored to fit their envi ronment. Bone growth in porous implants has been previously investigated, how ever this thesis studies the anisotropy of bone surrounding porous and non-porousmetallic implants through imaging methods such as birefringence microscopy andsmall-angle X-ray scattering (SAXS).Data from birefringence microscopy is corrected using Mueller calculus and the fastaxis angle and retardance of bone is analysed. As the region of interest is too largefor the microscope field of view, four images are stitched using the scale-invariant fea ture transform and random sample consensus algorithms. The birefringence data isvalidated through correlation with SAXS experiments. Additionally, 3D reconstruc tion of SAXS data is performed using real unrestricted spherical harmonic tensortomography.The validation of birefringence data indicates that the source of birefringence inbone is from collagen fibres. As a result, birefringence microscopy is used to showthat fibres outside the area affected by implantation have a preferred orientationalong the longitudinal axis and fibres inside of the porous implant have a preferredorientation that correlate with the geometry of the implant. Moreover, around theperimeter of the implant, bone growth is disordered as some fibres wrap around theoutside of the implant, and some grow into pores. This shows that the geometry ofthe implant plays an important role in the anisotropy of bone, which can efficientlybe studied using birefringence microscopy and SAXS