Lateral collapse of the tarsal navicular in patients with rheumatoid arthritis: Implications for pes planovarus deformity.

Objectives: In patients with rheumatoid arthritis (RA), the talonavicular joint is commonly involved and midfoot collapse can lead to progressive flattening of the arch. Despite a general awareness of the important structural role of the talonavicular joint in rheumatoid foot disease, details of its destructive pattern have not been elucidated.

Methods: We cross-sectionally investigated 176 RA patients (342 feet) and classified their feet into the following five groups according to radiographic findings: arthritis (RA changes with normal navicular shape), Müller-Weiss Disease (MWD) (collapse of the lateral aspect of the tarsal navicular), flat (flattened navicular), ankylosis (ankylosis of the talonavicular joint), and normal. We compared medical histories and radiographic measurements among all five groups.

Results: The arthritis group comprised 91 feet, 36 in the MWD group, nine in the flat group, 12 in the ankylosis group, and 194 classified as normal. The MWD group demonstrated a trend towards pes planovarus deformity in contrast to pes planovalgus deformity in the arthritis group. Corticosteroid use and the mean daily dosage were the highest in the MWD group.

Conclusions: This report revealed a high prevalence of MWD-like changes to the navicular in RA patients and its association with pes planovarus deformity and corticosteroid usage.