High-resolution CT imaging of the ankle

The ankle is a clinically important weight-bearing joint, and damage at this site is relevant to osteoarthritis, post-traumatic joint disease, and haemophilic arthropathy. In our earlier work, a 2-stack, with scanning length of region of interest 2.04 cm, tibiotalar protocol was piloted and shown to be feasible for joint space analysis. However, that protocol had practical limitations, as the joint space exists at the boundary between stacks, movement during the interval between image acquisitions could produce stack misalignment and thus compromise consistency of reconstruction of images. In addition, the full distal tibia, medial malleolus and medial gutter were not always captured in the 2-stack scanning. High-resolution peripheral quantitative computed tomography (HR-pQCT) is a low radiation imaging modality that provides three-dimensional assessment of bone microarchitecture and joint morphology. While HR-pQCT protocols are well established for many peripheral skeletal sites and have been utilized for joint space analysis, there is still limited evidence to guide the imaging of the tibiotalar joint. A refined 3-stack protocol was subsequently developed to increase scan coverage and place the tibiotalar joint space within the middle stack rather than at the stack interface. Preliminary testing has showed that this revised approach improved capture of the full distal tibia and medial gutter of the joint space and reduced the impact of stack artefacts, all while joint space width measurements remained similar to the previous method and joint space volume illustrated comprehensively as expected with improved whole joint capture. The next step is validation of 3-stack vs 2-stack in a larger sample of adults scanned with both protocols on the same ankle. The primary aim of this study is to validate a refined 3-stack tibiotalar HR-pQCT imaging protocol against the existing 2-stack protocol in a within person design. We will recruit 32 adults aged 18 to 80 years from existing Bone and Muscle Research Group registries, current healthy research cohorts, Monash networks and word of mouth. We will aim to include both women and men and to achieve broad representation across the adult age span, although strict age or sex-based recruitment quotas will not be imposed.