Statistical shape model of the talus bone morphology: A comparison between impinged and nonimpinged ankles

Diagnosis of ankle impingement is performed primarily by clinical examination,
whereas medical imaging is used for severity staging and treatment guidance.
The association of impingement symptoms with regional three‐dimensional (3D)
bone shape variaties visible in medical images has not been systematically explored,
nor do we know the type and magnitude of this relation. In this cross‐sectional
case‐control study, we hypothesized that 3D talus bone shape could be used to
quantitatively formulate the discriminating shape variations between ankles with
impingement from ankles without impingement, and we aimed to characterize and
quantify these variations. We used statistical shape modeling (SSM) methods to
determine the most prevalent modes of shape variations that discriminate between
the impinged and nonimpinged ankles. Results of the compactness and parallel
analysis test on the statistical shape model identify 8 prominent shape modes of
variations (MoVs) representing approximately 78% of the total 3D variations in the
population of shapes, among which two modes captured discriminating features
between impinged and nonimpinged ankles (p value of 0.023 and 0.042). Visual
inspection confirms that these two shape modes, capturing abnormalities in the
anterior and posterior parts of talus, represent the two main bony risk factors in
anterior and posterior ankle impingement. In conclusion, in this research using SSM
we have identified shape MoVs that were found to correlate significantly with bony
ankle impingement. We also illustrated potential guidance from SSMs for surgical
planning