Medical Mystery of the Week

       You are asked to evaluate a short video of a 24-year-old man's hand. You are given no other information. 
      What is your diagnosis, what test(s) would you order to confirm your suspicions, and what treatment, if any, do you recommend?
      DIAGNOSIS: Pseudotriggering of the middle finger due to extension tendon dislocation. Subluxations of extensor tendons from their central position on the metacarpal heads is rare, especially in non-rheumatoid patients. Four causes have been described: traumatic (due to sagittal band rupture), congenital, spontaneous and degenerative. Patients usually complain of discomfort and snapping with finger flexion. The disorder can be treated surgically with construction or repair of the sagittal band.

One can see the extensor tendon snapping off the metacarpal head (pseudotriggering) (left image). Pseudotriggering on the palmar surface (right image).