Analysis of dynamic scapholunate instability with stress views on plain wrist radiographs and stress CT

Different stress radiographs exist to diagnose dynamic scapholunate instability. Using a semi-automated stress CT-based measurement method, we compared the different imaging techniques in unstable wrists and in controls.

Scapholunate distance (SLD) was measured on radiographs with and without stress of both wrists of 22 participants without instability (group A) and 21 patients with one symptomatic unstable wrist (group B). All wrists also underwent a CT scan without and with stress to measure CT-SLD and radioscaphoid distance (CT-RSD).

In both groups, the SLD was greater in the clenched fist plus ulnar deviation views (median 2.2 mm (IQR 1.8 to 2.4) in group A and 2.5 mm (IQR 2.2 to 2.8) in group B) than in clenched fist views alone (median 1.9 mm (IQR 1.7 to 2.2) in group A and 2.2 mm (IQR 2.0 to 2.4) in group B). The SLD was greater in symptomatic unstable wrists than in stable wrists under all stress radiographs. In both groups, no statistically significant differences were measured between both sides during stress radiographs and CTs. The unloaded CT-SLD was greater in symptomatic unstable wrists (median 15 mm (IQR 12 to 17)) than in stable wrists (median 13 mm (IQR 12 to 15)). Under stress, the CT-RSD was greater in symptomatic unstable wrists (median 10 mm (IQR 8 to 13) than in stable wrists (median 6 mm (IQR 5 to 7).

Adding ulnar deviation to clenched-fist views along with stress CT may help to detect dynamic scapholunate instability.

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