Traction radiography for the diagnosis of scapholunate ligament tears

The diagnosis of scapholunate ligament injury by traction radiography was investigated within a consecutive study. The right wrists of 25 healthy volunteers and 22 wrists with arthroscopically proven complete scapholunate ligament tears were examined. Traction radiography was performed under fluoroscopy with a force of 5 kg applied to the thumb. In the normal wrists, this led to selective widening of the scapholunate joint space whereas the lunotriquetral distance remained unchanged. In 25 healthy right wrists, the median scapholunate distance measured 2.1 (range 1.3-2.6) mm on resting radiographs and 2.2 (range 1.7-3.5) mm on the stress radiographs. For the 22 wrists with complete scapholunate ligament tears, the median scapholunate distance was increased from 2.0 (range 1.0-3.0) mm to 3.8 (range 3.0-5.5) mm by traction (median difference of 1.8 (range 1.0-3.0) mm). In conclusion, a scapholunate distance of 3.0 mm or more in unloaded wrists or widening of the scapholunate interval by 1.0 mm or more under thumb traction should both be considered as pathological findings. We recommend traction radiography as a simple and valuable diagnostic procedure for suspected scapholunate ligament injury.