Presentation
Incidental finding.
Patient Data
Posterior anterior wrist X-ray demonstrating the widened gap (6 mm) between the scaphoid and the lunate bone ‘Terry Thomas’ sign. There is in addition foreshortening of the scaphoid with a ‘ring sign’. Underlying osteodegenerative changes are noted; these and the radio carpal joints are due to longstanding scapholunate instability (SLI). There's also decomposed thumb fracture.
The Terry Thomas sign refers to an increase in the scapholunate space on an AP radiograph of the wrist. The increased distance indicates scapholunate dissociation (often with rotary subluxation of the scaphoid) due to ligamentous injury. There is no consensus as to what measurement constitutes widening, but a cut-off of 3 or 4 mm is reasonable in most cases.
Case Discussion
Scapholunate dissociation is also called rotatory subluxation of the scaphoid and is sometimes referred to by the Terry Thomas sign. It is a disruption of the scapholunate ligament with resultant instability. The cause is usually trauma and the complication is degenerative arthritis of the joint. The x-ray of the wrist will demonstrate a widened scapholunate space, usually greater than 4 mm.
Radiographer: TSRM Fabio Imola
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