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Osteoarthritis (OA) is the most common chronic joint disease, which causes the cartilage between the bone joints to
wear away, leading to pain and stiffness. Currently, progression of OA is monitored by measuring joint space width
using x-ray or cartilage volume using MRI. However, OA affects all periarticular tissues, including cartilage and bone.
It has been shown previously that in animal models of OA, trabecular bone (TB) architecture is particularly affected.
Furthermore, relative changes in architecture are dependent on the depth of the TB region with respect to the bone
surface and main direction of load on the bone. The purpose of this study was to develop a new method for accurately
evaluating 3D architectural changes induced by OA in TB. Determining the TB test domain that represents the same
anatomic region across different animals is crucial for studying disease etiology, progression and response to therapy. It
also represents a major technical challenge in analyzing architectural changes. Here, we solve this problem using a new
active shape model (ASM)-based approach. A new and effective semi-automatic landmark selection approach has been
developed for rabbit distal femur surface that can easily be adopted for many other anatomical regions. It has been
observed that, on average, a trained operator can complete the user interaction part of landmark specification process in
less than 15 minutes for each bone data set. Digital topological analysis and fuzzy distance transform derived
parameters are used for quantifying TB architecture. The method has been applied on micro-CT data of excised rabbit
femur joints from anterior cruciate ligament transected (ACLT) (n = 6) and sham (n = 9) operated groups collected at
two and two-to-eight week post-surgery, respectively. An ASM of the rabbit right distal femur has been generated from
the sham group micro-CT data. The results suggest that, in conjunction with ASM, digital topological parameters are
suitable for analyzing architectural changes induced by OA.
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