Characteristics of medial gutter arthritis on weightbearing CT and plain radiograph

Objective An ankle arthritis with medial gutter obliteration is known to have good results after joint preservation surgery. However, the diagnosis is often missed on radiographs. The aims of this study were to investigate sensitivity of radiographs in the identification of medial gutter arthritis, incidence and direction of the talar tilt on weightbearing CT (WBCT), and to assess radiographic alignment of the medial gutter arthritis. Materials and methods Radiographic data was retrospectively evaluated in 102 ankles which were diagnosed medial gutter arthritis by using the WBCT at our clinic between January 2017 and June 2019. Among the 102 ankles, proportion of ankles which showed medial gutter arthritis on plain radiograph was obtained. The presence and direction of talar tilt were assessed on three coronal WBCT images at the anterior, middle, and posterior aspect of the ankle. Plain radiographic parameters were compared between the 102 ankles and control group. Results Plain radiograph showed medial gutter arthritis only in 63 ankles (62%) among the 102 ankles. Most of the ankles with medial gutter arthritis showed talar tilt on WBCT, and about half of all ankles showed valgus talar tilt at the anterior aspect of ankle on WBCT. In ankles with medial gutter arthritis, the mechanical axis of the lower extremity and the tibial plafond were varus angulated and the talus was medially translated compared to the control group. Conclusion Radiographs were less sensitive than WBCT in demonstrating medial gutter arthritis. Anterior aspect of ankles with medial gutter arthritis often showed valgus direction of talar tilt. Varus mechanical axis deviation and varus tibial plafond are commonly associated with the medial gutter arthritis.