Oral Presentation ANZBMS-MEPSA-ANZORS 2022

Strain Distributions Within the Proximal Tibia Calculated Using Digital Volume Correlation of Micro-CT Images (#13)

Kieran J Bennett 1 2 , Lauren Wearne 1 , Sophie Rapagna 1 , Saulo Martelli 3 , Bogdan Solomon 4 , Egon Perilli 1 , Dominic Thewlis 2 4
  1. Medical Devices Research Institute, Flinders University, Tonsley
  2. Centre for Orthopaedic and Trauma Research, The University of Adelaide, Adelaide
  3. Queensland University of Technology, Brisbane
  4. Department of Orthopaedics and Trauma, Royal Adelaide Hospital, Adelaide

The internal mechanical response of the proximal tibia to load has been limited to those implied from finite element models. Digital volume correlation (DVC), applied on micro-CT images, has been previously used to estimate the internal strains within virtual cores of the proximal tibia due to external load. However, whole organ strains have not been investigated. In this study, we aimed to quantify the internal 3D strains within the proximal tibia due to joint loading using DVC.

Two cadaveric knees were obtained, and all soft tissues except for the articular cartilage and menisci were removed. The femur and tibia were mounted within a loading stage, positioned within a large-volume micro-CT scanner (Nikon XT H 225, Nikon Metrology, UK). Scans were performed at 46 µm isotropic pixel size in unloaded and then loaded conditions. Axial loads corresponding to three bodyweights were applied. DVC analysis was undertaken to calculate von-Mises equivalent strains across the proximal tibia (DaVis software). The final DVC subvolume size was a 34 voxel (1.564 mm) subvolume length, required 100GB of memory and 20 core-hours to compute for each scan pair. Trabecular bone subvolumes more than 68 voxels from the cortical bone.

The median internal strains within the proximal tibia (Fig. 1) were 1890μϵ (interquartile range 1190μϵ) and 1962μϵ (interquartile range 1328μϵ) for specimens 1 and 2 respectively, with the distribution showing heterogeneity across the plateau.

Whole organ internal strains within the proximal tibia under load were quantified using DVC from large-volume micro-CT images. These data will enable relationships between the internal mechanical response and trabecular bone microarchitecture to be further explored.

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Figure 1. Micro-CT cross section of a human proximal tibia with strains due to external load calculated using DVC overlaid.