Pes planus intermetatarsal angle to measure flatfoot deformity on dorsoplantar radiographic imaging

Abstract

Objectives: Pes planus, or “flat foot,” is a common foot condition involving talus misalignment, calcaneus eversion, medial arch collapse, and forefoot abduction. It is a well-recognized cause of foot pain and can lead to disability in patients. Clinical diagnosis is supported by plain radiography. However, in patients presenting with foot pain, traditionally dorsoplantar (DP) and oblique radiographs are undertaken. Pes planus may be difficult to analyze and classify on predominant DP and oblique radiographs and often requires weight-bearing lateral foot radiographs to direct patient management. Our study introduces a novel angle for pes planus diagnosis on DP radiographs of the foot. The purpose of this study was to describe a new radiological pes planus intermetatarsal angle (PPIMA) for assessment of flatfoot DP imaging of the foot. Materials and Methods: We performed a retrospective cohort study on 114 consecutive patients presenting with foot pain referred to our foot and ankle clinic weight-bearing DP, oblique radiographs of the foot and lateral radiographs of the foot and ankle were undertaken. Demographic details and clinical indication were recorded, and radiological parameters of hallux valgus angle, calcaneal pitch and angle between the shaft of the first and fifth metatarsal PPIMA were measured by two consultant radiologists and a radiology trainee. Data were organized using Microsoft Excel, and statistical analysis was performed STATA (StataCorp LLC, College Station, TX, USA) using analysis of variance and post hoc analysis. Results: Thirty patients were excluded due to the presence of hallux valgus deformity. In our study, the cohort with normal foot alignment (n = 30, age 14–18) had an average PPIMA of 20.7°, pes cavus (n = 3, age 14–18) average PPIMA was 24.0, while the pes planus group (n = 51, age 14–18) had an average PPIMA of 20.0°. There was no statistically significant difference in PPIMA between the groups (P = 0.229). Conclusion: Our study introduces a practical diagnostic tool for pes planus on DP foot imaging. The PPIMA is not a reliable indicator for the evaluation of foot alignment.