High prevalence of pes planus in children with Fontan circulation.

Background: The musculoskeletal system is important for maintaining Fontan circulation. However, little is known about the foot morphology in this population. This study aimed to evaluate the prevalence of pes planus and its association with the patients' physical characteristics after the Fontan procedure. Methods: This single-center, cross-sectional study evaluated patients who underwent the Fontan procedure. Pes planus was assessed via physical examination. Physical measurements, including height, weight, body mass index, and fat-free mass index (FFMI), were collected and compared between patients with and without pes planus. Multivariable logistic regression analysis adjusted for age and sex, and time since the Fontan procedure was performed. Results: Forty-seven patients (median age: 13 years) were included. Pes planus was observed in 27 (57%) patients and was present in all age groups. The patients with pes planus had a significantly lower height SDS (P = 0.011) and tended to have a lower FFMI (P = 0.066). In the adjusted analysis, a lower FFMI showed a trend toward an association with pes planus, although this did not reach significance (OR 0.648, 95% CI 0.38-1.12, P = 0.118). Conclusions: Pes planus is highly prevalent in patients with Fontan circulation and may represent an under-recognized musculoskeletal phenotype. Further studies are required to clarify the etiology and clinical significance.