Relationship Between Obesity and Medial Longitudinal Arch Bowing

Background: There have been reports about the association between obesity and the medial longitudinal arch (MLA) of foot. The purpose of this study is to investigate the change of various parameters related to the MLA according to obesity classification severity by the World Health Organization using weightbearing computed tomography (WBCT). Methods: WBCT data of the noninvolved side of patients presenting with unilateral foot and ankle problems or healthy candidates from September 2014 to October 2022 were extracted from a single referral hospital. Forty-four cases in each of 5 obesity classes were selected sequentially. Two orthopaedic surgeons measured foot and ankle offset, forefoot arch angle (FAA), hindfoot moment arm, percentage of uncoverage of the middle facet of the subtalar joint, talonavicular angle (TNA), navicular–medial cuneiform angle, medial cuneiform–first metatarsal angle, talus–first metatarsal angle (TMT1A), first tarsometatarsal subluxation (TMT1S), talonavicular coverage angle, navicular floor distance (NFD), and NFD per height. Positive values indicate plantar collapse. Intra- and interobserver reliabilities were assessed using intraclass correlation coefficients. One-way analysis of variance tests were performed for parametric data with equal variances, and Welch’s test for unequal variances. Kruskal-Wallis test was performed for nonparametric data. Post hoc analysis was performed for statistically significant parameters. Correlation analysis between body mass index (BMI) and 12 parameters were performed using Pearson test. Results: Intraobserver and interobserver reliability were excellent, except for TMT1S. The TNA and TMT1A showed a statistically significant difference. FAA ( r = −0.2), TNA ( r = 0.182), TMT1A ( r = 0.296), and NFD ( r = −0.173) showed a statistically significant correlation with BMI Conclusion: In nonsymptomatic feet, we found that the talonavicular joint, as measured by the TNA, to be influenced by obesity classification. Obesity and increased BMI was associated with a negative influence on the MLA. Level of Evidence: Level III, retrospective cohort study.