Page 59 - Imaging of Osteoarthritis and Rheumatoid Arthritis in Hand Joints
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 Fig. 3 Examples of Eaton stages on CT. Stage I: There is no joint space narrowing or subluxation, only a small osteophyte is visible (circle). Stage II: Focal joint space narrowing is present. Stage III: There are erosions (circle), osteophytes larger than 2 mm (arrows), and (limited) JSN. Note that the STT joint space is normal. Stage IV: There is evident JSN between trapezium and metacarpal bone (circle) and between the trapezium and scaphoid (square)
The reliability of the radiographical Eaton stage in our study is in agreement with those of previous studies,15-17 but our reliability of CT Eaton stage was higher than that reported in a recent study (κ=0.02-0.038).18 In that CT study, the authors report that their reliability was low because the complicated Eaton and Glickel system was scored by their readers without prior training or experience. Our reliability was probably higher because we defined and scored each separate feature of the scoring system, defined which features should lead to which score, and organized a training session.
We found that CT detected more patients with CMC1 and STT OA than radiography, and consequently higher Eaton stages were scored with CT. While reader 1 detected twelve additional STT OA patients with CT, reader 2 only detected five additional patients. The high reliability results from CT, however, suggests that there was no real difference in OA detection with CT, but that the readers missed these patients with radiography.
CT for detection of thumb base OA

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