Radiological study of joint destruction patterns in rheumatoid flatfoot.

The purpose of this study was to clarify variations in patterns of flattening in rheumatoid hindfoot. Out of 232 outpatients with rheumatoid arthritis treated at our hospital from 2001 to 2003, we studied lateral radiographs of feet of 216 patients (423 weight-bearing views). We measured the medial arch angle (MAA) and talar angle (TA) and compared the alignment of the talonavicular joint-sagittal plane of each foot. We also evaluated the relationship between the severity of flattening and inclination of the talus and performed cluster analysis. Three groups were clustered by MAA and TA. In group I, joints were normal or close to normal. In group II, both talonavicular and subtalar joints were affected. In group III, talonavicular joints were minimally affected, and the subtalar joints were primarily affected. Groups II and III were thought to be a different pattern of flattening. The present results suggest that there are at least two patterns of flattening in rheumatoid hindfoot.