The clinical description and video of the patient's physical exam are consistent with an acute scapho-lunate ligament tear. The video shown in the question stem demonstrates the Watson test. When positive, the patient will feel dorsal wrist pain and/or a "clunk" when the wrist is brought from extension/ulnar deviation to radial deviation. If plain radiographs are normal, a PA clenched fist radiograph as seen in Figure A should be performed.
In patients with a acute scapho-lunate ligament tear, initial radiographs may not show the characteristic "Terry Thomas" sign, or widening of the SL gap > 3mm. When making a clenched fist, the capitate is drawn proximally, stressing the SL ligament. This is an easy view to obtain during the initial patient visit and should strongly be considered if this diagnosis is suspected.
Walsh et al review the various aspects of scapholunate ligament injuries. While they agree imaging is helpful in establishing the diagnosis, they emphasize that wrist arthroscopy is the gold standard in the diagnosis of SL injuries.
Illustration A shows demonstrates a clenched fist view with obvious widening of the scapho-lunate gap.
Answer 2: Shows a lateral radiograph in 30 degrees of supination. It is excellent for assessment of pisotriquetral arthrosis.
Answer 3: Shows a PA of the wrist in radial deviation. This view will actually close the SL gap.
Answer 4: Shows a a carpal tunnel view, used for assessment of hook of hamate fractures.
Answer 5: Shows a a stardard PA wrist in neutral aligment.
Walsh JJ, Berger RA, Cooney WP: Current status of scapholunate interosseous ligament injuries. J Am Acad Orthop Surg 2002;10:32-42
PMID:11809049 (Link to Abstract)
Browner BD, Levine AM, Jupiter JB, et al (eds): Skeletal Trauma, ed 2. Philadelphia, PA, WB Saunders, 1998, pp 1366-1367.