Abstract
Dear Sir,
A 49 year-old right-handed man fell backward on his outstretched left hand. He supported his entire body on his palm with the left shoulder in 40° of extension, the elbow in maximal extension, the forearm in 90° of supination and the wrist in maximal extension. Immediately after the injury, he felt pain, swelling and limitation of motion in the left wrist. When we examined him 2 hours after the injury, he complained of pain on the dorsoulnar side of the wrist with limitation of movement. Examination of the wrist showed no joint effusion or tenderness of the distal radius, the anatomical snuffbox or the scaphoid tubercle to suggest a fracture. There was some swelling and discrete tenderness on the dorsoulnar side of the wrist, exactly at “the triquetral point” (Letts and Esser, 1993), the first bony prominence on the dorsum of the wrist, immediately distal to the ulnar styloid. Plain X-ray showed an undisplaced fracture of the body and a minimally displaced fracture of the dorsal cortex of the triquetrum. (Figs 1 and 2). The patient was immobilised initially in a short arm cast. The cast was removed after 5 weeks and the patient started mobilisation exercises. At this time, X-rays showed fracture union and the range of motion of the wrist was normal and painless by 6 weeks.
Triquetral fractures are commonly associated with other carpal injuries (Amadio and Moran, 2005) and isolated fractures of the triquetrum are seen rarely. The true incidence of these fractures is unknown because they are often undiagnosed, or misdiagnosed, as “wrist sprain”(Letts and Esser, 1993; Schubert, 2000). Garcia-Elias (1987) suggested that these injuries are not avulsions but are the product of a chisel action of the ulnar styloid process on the dorsum of the triquetrum during strong dorsiflexion and ulnar deviation. He also suggested that persons with a long styloid process have an increased chance of this injury. His view is now generally accepted (Levy et al., 1979).
Reviewing the literature, we were unable to recognise any cases in which both the main body and the dorsal cortex of the triquetrum fractured at the same time. We suggest a possible mechanism of this double fracture: as a result of the fall onto the dorsiflexed hand, taking the full body weight, the “chisel” action of the ulnar styloid caused the fracture of the body of the triquetrum. Then, ulnar deviation of the hand resulted in a dorsal cortical fracture of the triquetrum by striking the hamate.