The purpose of this study was to determine the reliability of plain axillary radiographs as compared to CT in defining the Walch classification for shoulders with primary osteoarthritis. Three experienced shoulder arthroplasty surgeons blindly and independently evaluated the axillary radiographs and CT scans of 75 consecutive shoulders (71 patients) with primary glenohumeral osteoarthritis. Each observer classified all shoulders according to the Walch classification (four separate sessions, six weeks apart, twice using only radiographs and twice using only CT scans). The order of shoulders was randomized for each reading session.
The first reading by the most senior observer based on CT was arbitrarily used as the gold standard, and revealed the following distribution: A1 21, A2 13, B1 12, B2 28, C 1.
The average intraobserver agreement for radiographs was 0.66 (substantial; 0.66, 0.59 and 0.74 for each observer).
The average intraobserver agreement for CT scans was 0.60 (moderate; 0.53, 0.61 and 0.65 for each observer).
Pairwise comparisons between independent observers showed higher agreement for radiographs than CT scans (0.48 vs. 0.39).
The average agreement for observations on radiographs and CT scans was 0.48 (moderate; 0.40, 0.37, 0.50).
The authors concluded that agreement among observers when using the Walch classification based on axillary radiographs was substantial, and compared well with agreement based on CT scans. Observations based on radiographs and CT scan did not always agree, even when performed by the same observer.
Comment: We have previously pointed out that a standardized axillary view provides the necessary and sufficient information for planning and evaluating shoulder arthroplasty. This is an important paper in that it suggests that routine CT scans - with their attendant increase in cost and radiation exposure - are not needed to classify the glenohumeral pathoanatomy in primary osteoarthritis. While additional information may be obtained from CT scans and from 3D reconstructions, it has yet to be demonstrated that this additional information leads to better surgical outcomes.
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