Mechanical analyses of trabecular bone and its interaction with implants

  • Date:
  • Location: Ångström 8001, Lägerhyddsvägen 1, Uppsala
  • Doctoral student: Wu, Dan
  • About the dissertation
  • Organiser: Tillämpad materialvetenskap
  • Contact person: Wu, Dan
  • Disputation

In order to improve fracture treatment where the interior, porous trabecular bone is involved, it is important to better understand the mechanical properties of this bone and how it interacts with the substitutes/implants, and this was the aim of this thesis.

Bone substitute materials or implants are commonly used in the surgical treatment of bone fractures. However, severe complications are sometimes reported. In order to improve fracture treatment where the interior, porous trabecular bone is involved, it is important to better understand the mechanical properties of this bone and how it interacts with the substitutes/implants, and this was the aim of this thesis.

Since one of the key mechanical properties of trabecular bone, i.e. the elastic moduli at the tissue level, was not consistently reported in the literature, the results from four widely applied methods were first summarized and presented in a review paper.

Furthermore, to improve the analysis of the mechanical behavior of bone and its interaction with implants, a new digital volume correlation (DVC) technique was proposed based on higher-order finite elements.

We further proposed a method to estimate the elastic modulus at the tissue level by compression of single trabeculae within a synchrotron radiation micro-computed tomograph (SRµCT). Full-field displacements were estimated by DVC, which also provided boundary conditions for a finite element model. The proposed method shows potential to estimate trabecular mechanical properties at the tissue level.

Further, strains and cracks of a trabecular structure under compression till fracture were characterized at the single trabecular level, with DVC applied on high-resolution images from SRµCT.

The effect of augmentation materials on the engagement of screws inserted into trabecular bone was evaluated in human femoral bone, with and without real-time SRµCT. A newly developed tissue adhesive indicated a potential benefit of this material to the primary implant stability compared to a cement and no augmentation.

Finally, a trabecular structure of PLA/HA composite material was printed using a fused deposition modelling method as a preliminary step towards better synthetic models of trabecular bone. The synthetic trabecular structure was evaluated using micro-CT, compression and screw pull-out testing.

In conclusion, methods to estimate strains and mechanical properties of trabecular bone were proposed, insights into interactions between trabecular bone and augmentation/implants were gained, as well as a first step towards a synthetic trabecular model, which may contribute to further mechanical analyses and/or improved clinical treatments of trabecular bone.