Assessment of scapholunate instability with dynamic computed tomography.

We performed a prospective study to evaluate the values of dynamic four-dimensional computed tomography in assessing suspected chronic scapholunate instability. Forty patients were evaluated with radiographs, arthrography, and four-dimensional computed tomography. On plain radiographs and computed tomography, we found 16 patients with definite scapholunate instability, five with questionable scapholunate instability, and 19 with absence of scapholunate instability. We used four-dimensional computed tomography to evaluate the size of the scapholunate gap during radioulnar deviation. The mean and maximal values of the gap size were lowest in the patients with absence of scapholunate instability and highest in those with definite scapholunate instability. When comparing the scapholunate gap sizes of the patients with absent and questionable scapholunate instability, the range of the gap sizes was significantly higher in the patients with questionable scapholunate instability. We conclude that four-dimensional computed tomography aids assessment of chronic scapholunate instability, which allows the differentiation between patients without and those with definite or questionable scapholunate instability. Level of evidence: II.