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Frequency and Characteristics of the Scaphoid Cortical Ring Sign
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ABSTRACT
The scaphoid cortical ring sign has been identified as a radiographic indicator of ligamentous wrist injury. It has been associated with some pathokinomatic states. The cortical ring sign may be normal in a range of wrist positions. This study defined the range of motion when the cortical ring sign can be normally observed on a standard posteroanterior (PA) radiograph, and in turn, defined the range when the cortical ring sign is not expected to be present.
One hundred nine PA radiographs of normal wrists were evaluated for the presence, partial presence, and absence of the scaphoid cortical ring sign. The results were correlated with the radiometacarpal angle in neutral palmar-dorsiflexion of the wrist. The range of wrist deviation for the wrists studied was 210 (radial deviation) to 23 (ulnar deviation).
The normal (and abnormal) range was defined as two standard deviations from the mean. The cortical ring sign was present in 25% of the radiographs evaluated. Moreover, the cortical ring sign was found at 2.7º±7.7º of radial deviation with an expected range of 18.1º of radial deviation to 12.7º of ulnar deviation. The ring sign was absent at 12.4º±11.7º of ulnar deviation.
Cortical ring sign observed at values <13º of ulnar deviation may be abnormal. If the cortical ring sign is observed at a radiometacarpal angle of >13º of ulnar deviation, it should be considered pathologic. The cortical ring sign, however, should be used in conjunction with other clinical and radiographic findings of carpal instability.