Study of bone anisotropy in porous metal lic implants using birefringence and X ray scattering imaging
Examensarbete för masterexamen
Biomedical engineering (MPBME), MSc
Metallic implants are commonplace in orthopaedic surgery. Recent advances in manufacturing technology have made it possible to manufacture 3D printed porous implants. 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-porous metallic implants through imaging methods such as birefringence microscopy and small-angle X-ray scattering (SAXS). Data from birefringence microscopy is corrected using Mueller calculus and the fast axis angle and retardance of bone is analysed. As the region of interest is too large for the microscope field of view, four images are stitched using the scale-invariant fea ture transform and random sample consensus algorithms. The birefringence data is validated through correlation with SAXS experiments. Additionally, 3D reconstruc tion of SAXS data is performed using real unrestricted spherical harmonic tensor tomography. The validation of birefringence data indicates that the source of birefringence in bone is from collagen fibres. As a result, birefringence microscopy is used to show that fibres outside the area affected by implantation have a preferred orientation along the longitudinal axis and fibres inside of the porous implant have a preferred orientation that correlate with the geometry of the implant. Moreover, around the perimeter of the implant, bone growth is disordered as some fibres wrap around the outside of the implant, and some grow into pores. This shows that the geometry of the implant plays an important role in the anisotropy of bone, which can efficiently be studied using birefringence microscopy and SAXS
Porous implants, birefringence, collagen, SAXS.