Answer to Case 1.6
A 49-year old man fell off a ladder 4 days ago and continues to have pain in his right wrist. He denies pain in other parts of his body. On examination, there is tenderness and swelling at the dorsal medial aspect of his wrist. The patient receives a dose of oral analgesic medication. The following radiograhs are obtained.
1. What is the radiographic diagnosis?
1. Acute triquetral dorsal chip fracture.
2. Volar splint and follow up with an orthopedic or hand surgeon within 7-10 days
The above radiographs show a small dorsal chip on the lateral radiograph. This is pathognomonic for a triquetral fracture. The triquetrum is the second most commonly fractured carpal bone. The mechanism of injury can either be forced hyperextension, hyperflexion or a direct blow. Patients typically have pain and swelling on the dorsal medial aspect of the wrist. Tenderness is often palpated just distal to the distal ulna and ulna styloid. The triquetrum has a very rich vascular supply and non-union is usually not an issue. All patients should be splinted and given orthopedic or hand surgeon follow-up.
Wrist radiographs can be difficult to interpret and missed injuries are common. Radiograph interpretation is aided by knowing which injuries are common, which can be easily missed, and the findings on physical examination. In the wrist, distal radius fractures are by far most common and, although usually obvious, the radiographic findings are occasionally subtle or the radiographs are normal (an occult fracture).
Among carpal injuries, scaphoid fractures account for 60%. The radiographs may have subtle findings or be normal. The second most commonly fractured carpal is the triquetrum – a dorsal chip fracture that is seen on the lateral view. (The triquetrum is the most dorsally projecting carpal bone on the lateral view.) When a patient with a wrist injury presents with pain and swelling on the dorsum of the wrist, a dorsal chip triquetrum fracture should be suspected and the lateral view examined for this injury. In this patient, there is also soft tissue swelling over the dorsal surface of the wrist on the lateral view. Dorsal chip fractures of the triquetrum account for 20% of carpal injuries.
Most of the remaining 20% of carpal injuries are “perilunate injuries,” a spectrum of ligmentous injuries, subluxations, dislocations and fractures in proximity to the lunate. Injuries of other carpals are uncommon, but can also be difficult to detect radiographically. Therefore, any patient with significant wrist pain following an injury should be splinted and referred to an orthopedist or hand surgeon for further evaluation. This may entail repeat radiographs, a bone scan (no longer used), MRI or possibly MDCT.
Schwartz DT: Emergency Radiology: Case Studies, McGraw-Hill, 2008, pp.249-256, 257-266.
radER is a weekly contest, hosted by Dr. Kerin Jones’ “Fracture”, consisting of a radiograph selected from various areas of emergency medicine that are central to the education of medical students and residents in training.
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