Identification of Radiographic Foot Osteoarthritis: Sensitivity of Views and Features Using the La Trobe Radiographic Atlas

Objective: To compare the sensitivity of alternative case finding approaches for the identification of foot osteoarthritis (OA) based on the La Trobe radiographic atlas. Methods: This was a cross-sectional study of 533 adults age ≥50 years with foot pain in the past year. Weightbearing dorsoplantar (DP) and lateral radiographs were taken of both feet. The La Trobe radiographic atlas was used to document the presence of osteophytes (OPs) and joint space narrowing (JSN). The prevalence of OA in each joint was documented using both views and features in combination (as recommended in the original atlas), and by using a single view (DP or lateral only) and a single feature (OP or JSN only). Results: Compared to the recommended case definition based on OPs and JSN using both views, a DP-only view identified between 15% and 77% of OA cases, while a lateral-only view identified between 28% and 97% of OA cases. Compared to the recommended case definition of using both features, using only OPs identified between 46% and 94% of OA cases, while using only JSN identified between 19% and 76% of OA cases. Conclusion: Applying the La Trobe radiographic atlas but using only 1 radiograph view (DP or lateral) or 1 feature (OP or JSN) in isolation misses a substantial number of OA cases, and the sensitivity of these approaches varies considerably between different foot joints. These findings indicate that, where possible, the atlas should be administered according to the original description to avoid under-ascertainment of radiographic foot OA.