Scapholunate dissociation, also called rotatory subluxation of the scaphoid and sometimes also known as the Terry Thomas sign. It involves a disruption of the scapholunate ligament resulting in instability. The scapholunate ligament is U shaped and divided into three compartments. A complete fear of the dorsal part, results in dissociation.
The cause is usually trauma, with patients presenting following a fall onto the wrist, or hand. The future complication is degenerative arthritis of the joint.
Sometimes patients will not recall any injury. In this particular case, the patient, a 62 yo woman presented with pain in the wrist. She recalled no trauma. There was mild tenderness over the wrist. The x-ray findings were unexpected.
An x-ray of the wrist will demonstrate a widened scapholunate space, usually greater than 4mm. This is best seen on a clenched fist view.
This is known as the Terry Thomas Sign reflecting the gap in the teeth that this entertainer had.
Treatment is by surgical repair. If this isn’t repaired there Is a migration of the capitate between scaphoid and lunate which results in longer term degenerative disease.