BACKGROUND: The characteristic cavovarus foot deformity associated with Charcot-Marie-Tooth disease (CMT) is highly variable between individuals. Although substantial progress has been made in characterizing foot morphology in CMT, previous investigations have not addressed limb symmetry within individuals. This is relevant to functional assessment scales, which typically measure only the dominant limb, and has implications for surgical treatment planning. This study aimed to use weight-bearing computed tomography (WBCT) to examine similarity in deformity between limbs in individuals with CMT.
METHODS: Bilateral WBCT images of 31 individuals with CMT were analyzed through automatic calculation of 9 radiographic measurements and generation of a statistical shape model (SSM). Morphologic variation in the SSM was described with principal components analysis (PCA). Absolute differences in radiographic measures and PCA scores between paired limbs were analyzed with appropriate statistical tests with Bonferroni correction.
RESULTS: Significant absolute differences between paired limbs were identified in all radiographic measures, ranging from a median difference of 1.2° in calcaneal inclination angle to 5.8° in the axial plane Meary angle. Similarly, significant absolute differences between limbs were identified on all 3 analyzed modes of variation in the SSM, with the greatest difference seen in in hindfoot varus rotation. Significant laterality-dependent morphologic differences could not be identified.
CONCLUSION: Both radiographic measures and SSM demonstrated statistically significant absolute differences between limbs. In both methods, greater magnitude of difference was seen between limbs in hindfoot varus rotation than arch height.
CLINICAL RELEVANCE: These data provide quantitative characterization of the clinically suspected limb-to-limb asymmetry in CMT-related cavovarus deformity. Alignment differences between limbs support the use of limb-specific assessment in functional outcome measures and surgical algorithms. This supports the need for further research quantifying clinically significant differences in foot morphology and consideration of limb asymmetry in research and patient education for CMT.
LEVEL OF EVIDENCE: Level III, retrospective cross-sectional study.
Read the article: PubMed · Publisher (DOI)