Abstract
OBJECTIVE: For midfoot injuries requiring surgical intervention, radiographs of the contralateral, non-injured foot are often used as a guide to restore patient anatomy. We seek to validate this approach by examining the intra-subject variability in midfoot anatomy among the uninjured population. METHODS: A retrospective review of 440 patients with bilateral foot radiographs was performed. A total of 246 patients met the inclusion criteria. The first to second intermetatarsal angle (IMA), talo-first-metatarsal angle (T1MA), Meary's angle (MA), and calcaneal inclination (CI) were measured. The side-to-side difference and inter-subject variability were analyzed using the mean absolute percentage side-to-side difference (MAPSSD) and the coefficient of variation (COV) to yield the ratio of variation (ROV). An ROV greater than 1 indicates greater inter-subject variability than intra-subject differences. Standard linear model analysis was performed to study each parameter against sex, race, and age. Results: There were no significant differences in IMA, T1MA, or CI in side-by-side measurements, but there was a significant difference in MA between the left and the right side. The ROV for IMA, T1MA, MA, and CI were all greater than 1, indicating greater inter-subject variability than intra-subject variability between the left and the right sides. Male sex was associated with a smaller IMA. Hispanic heritage was associated with smaller T1MA. Older age and Black people were associated with smaller MA angles. Caucasian people had larger CI values. All correlations were statistically significant with a p-value < 0.05. CONCLUSIONS: Intra-subject variability in midfoot anatomy is less than inter-subject variability, therefore validating the use of the contralateral limb as a guide in the surgical repair of midfoot injuries.