Master of Engineering Science
Musculoskeletal Health Research
Four-dimensional computed tomography (4DCT) is a novel imaging modality initially used in cardiac imaging but recently applied to the musculoskeletal system; although its methodology has been developed, it is still in its infancy as a powerful clinical tool. Currently, scapholunate interosseous ligament (SLIL) tears, whose early symptoms are elucidated through dynamic movement, are diagnosed with static techniques that cannot visualize dynamic motion; hence, a tool is needed that is responsive and dynamic to visualize subtle abnormal carpal movements indicative of SLIL tears. It is hypothesized that 4DCT can visualize subtle dynamic carpal movements to define uninjured motion as well as differentiate between that and motion from those with SLIL tears. Understanding uninjured wrist motion was done by calculating scaphoid centroid translation and joint surface area (JSA) from kinematic 4DCT scans. The findings agreed with previously reported outcomes. The 4DCT tool was validated against a gold standard (micro-CT). Lastly, the 4DCT tool was provocatively tested to determine kinematic differences between uninjured and SLIL tear cohorts, as well as between types of SLIL tears. The helical axes of the scaphoid and lunate were calculated from 4DCT bone models using custom MATLAB code. Findings suggest that 4DCT shows promise as a diagnostic tool for dynamic injuries and that volar SLIL tears may negatively impact carpal motion.
Summary for Lay Audience
Currently, there is no universally-agreed-upon theory for how the wrist moves; the wrist is made of nine bones and two forearm bones, and so its motion is complex. One reason for why there is no such theory is a lack of data; it is difficult to image wrist motion because a lot of methods for imaging the wrist are static. Static imaging methods, such as the common x-ray, are methods that can only visualize how the bones are positioned when the wrist is stationary. This presents a large problem when diagnosing injuries. Certain injuries, such as ligament tears, wherein a ligament connects bone to bone, have symptoms that are only apparent when the wrist is in motion. Ligament tears are painful, and it is important to medically intervene early for the best results. A tool is needed to visualize wrist motion for two reasons: to measure uninjured wrist motion and to determine the differences between that and wrist motion in individuals with ligament tears. This thesis proposes the use of four-dimensional computed tomography (4DCT) to address both needs because 4DCT scans can create a movie of moving 3D bone models.
The 4DCT tool was used to measure uninjured wrist movement, specifically the translation of a wrist bone and the amount of contact between neighbouring bones. Once it was determined that 4DCT could successfully take such measurements, it was validated against a gold standard method, micro-CT. Micro-CT creates high-quality 3D models of the wrist bones, but it is a static imaging method. The comparison confirmed that 4DCT was valid, and so it was applied to a more challenging situation: detecting differences between uninjured wrist motion and that of individuals with ligament tears. It was hypothesized that the type of tear would determine how wrist motion differed from uninjured motion. The 4DCT scans were used to measure wrist bone rotation and contact between neighbouring bones. The results showed that 4DCT could detect a difference in these measurements. All types of ligament tears may impact wrist motion and may need to be repaired, as only some types are currently surgically repaired.
Robinson, Sydney M., "4DCT to Examine Carpal Motion" (2021). Electronic Thesis and Dissertation Repository. 7801.