LAUSR

PURPOSE Accuracy in diagnosing osteoarthritis in the midfoot using weightbearing plain radiography (WBPR) remains questionable due to the overlapping osseous architecture present, occluding visualization. Weightbearing computed tomography (WBCT), providing clearer bony landmark identification and joint space visualization, can also be used for evaluation. The aim of this project is to perform a standardized retrospective intra-patient analysis identifying the discrepancy of midfoot osteoarthritis diagnosis and osteoarthritis severity grading between WBPR and WBCT. METHODS AND MATERIALS A cohort of 302 patient feet was acquired from an internal, consecutive patient database using detailed inclusion criteria. The musculoskeletal radiologist interpretation of the WBCT and WBPR of each specimen was then assessed for any direct diagnosis or mention of osteoarthritic signs in specific articulations of 3 midfoot joint groups (Chopart, "central", and tarsometatarsal). WBPR sensitivity and specificity metrics were calculated with WBCT considered the gold standard for comparison. RESULTS From the WBPR radiologist interpretation, we found diagnostic sensitivity of 72.5 % and specificity of 87.9 % for Chopart joints; 61.5 % sensitivity, and 96.1 % specificity for central joints; and 68.4 % sensitivity, and 92.9 % specificity for tarsometatarsal joints. The severity of degenerative changes was also consistently underestimated when interpreted from WBPR relative to WBCT. CONCLUSIONS In this series, midfoot osteoarthritis was often undetected on WBPR. WBCT imaging facilitates an earlier, more reliable diagnosis and grading of midfoot osteoarthritis relative to WBPR.