Extensor Tendon Rupture Due to Advanced Kienböck's Disease: Two Case Reports and a Review of Literature.

Extensor tendon rupture of the finger is a very rare complication of Kienböck's disease. However, advanced Kienböck's disease can cause an attritional rupture of extensor tendons due to displaced lunate fragment. An extensor tendon of the thumb is frequently damaged in the distal radial fracture, and an extensor tendon of the fifth finger is mainly ruptured in arthritis of distal radio-ulnar joint. On the other hand, the extensor tendons of the 2nd, 3rd and 4th fingers are usually ruptured in advanced Kienböck's disease. We report two elderly patients diagnosed with advanced Kienböck's disease after non-traumatic rupture of extensor tendon of the fingers. Since the extensor tendon rupture in Kienböck's disease present as a loss of active extension of metacarpophalangeal joint in the central fingers, these patients should undergo imaging of the wrist joints to ascertain concomitant Kienböck's disease.