Background: Hallux valgus (HV) is a complex, multiplanar deformity. In this study, we examined the interrelationships
between various components of this deformity using weightbearing computed tomography (WBCT). We hypothesized
that the severity of traditional axial plane deformities would correlate with malpositioning of the metatarsosesamoid
complex, first-ray coronal rotational deformity, and malalignment of the hindfoot and midfoot. The findings may offer
valuable insights for guiding the correction of HV deformities.

Methods: Patients with an HV angle greater than 15 degrees who underwent WBCT were included. Traditional
2-dimensional parameters were semiautomatically assessed. Manual measurements included hindfoot and midfoot WBCT
parameters, for example, foot and ankle offset, talar posterior and middle facet morphology, and forefoot arch angle.
First-ray parameters, including first metatarsal rotation, sesamoid rotation angle, hallucal pronation angle, and sesamoid
position, were measured using established methods. Patients were categorized by hindfoot moment arm values to evaluate
hindfoot-forefoot relationships.

Results: Sixty-eight feet (53 patients) were included. Manual measurements exhibited excellent interobserver reliability,
with ICCs of 0.845 to 0.987 and a kappa coefficient of 0.899 for the sesamoid position. The mean HV angle was 27.4 ± 7.8
degrees, whereas the mean IM angle was 15.8 ± 3.5 degrees. Significant correlations were observed between the HV
and intermetatarsal (IM) angles, with all metatarsosesamoid complex parameters and first-ray coronal plane rotational
parameters distal to the metatarsal head. The axial and sagittal talar–first metatarsal angles correlated with the HV angle
but not with the IM angle. Significant differences in the HV angle, sagittal first tarsal–metatarsal joint angle, and first
metatarsal head rotation were observed between the hindfoot moment arm groups, as confirmed by post hoc analysis.

Conclusion: The findings support our hypothesis, identifying significant correlations between metatarsosesamoid complex
malposition, distal first-ray coronal pronation, and traditional axial plane deformities in HV. Some hindfoot–midfoot
alignments correlated with the HV angle but not with the IM angle.

Level of Evidence: Level IV: case series.