CASE 9720 Published on 19.12.2011

Isolated capitate fracture

Section

Musculoskeletal system

Case Type

Clinical Cases

Authors

Marchinkow A, Murphy DT, Chang DR, Korzan JR, Ouellette HA, Munk PL

Vancouver General Hospital,
University of British Columbia,
Radiology;
899 west 12th avenue
v5z1m9 Vancouver, Canada;
Email:peter.munk@vch.ca
Patient

24 years, male

Categories
Area of Interest Musculoskeletal bone ; Imaging Technique Conventional radiography, CT
Clinical History
A 24-year-old man presented with acute onset of left wrist pain following trauma.
Imaging Findings
Initial AP and lateral radiographs failed to show an acute osseous abnormality (Fig. 1a and b). A fracture was suspected clinically, and a subsequent non contrast CT was performed. This showed a minimally displaced oblique fracture through the capitate, best seen on coronal and sagittal reconstructions (Fig. 2a and b).
Discussion
With displaced capitate fractures, plain radiographs for diagnosing and evaluating the trauma to the capitate are often sufficient. Typical plain film findings include a transverse lucency through the capitate on the AP view and a transverse or obliquely orientated lucency on the lateral view. A step-off may be evident.
Due to the complex anatomy of carpal bones, however, plain radiographs could potentially miss non-displaced fractures. MR imaging may also detect undisplaced fracture lines as well as evaluating for AVN.
Several types of capitate fractures have been described including transverse body, transverse proximal pole (waist), coronal oblique and parasagittal fractures.
The capitate is the largest carpal bone and is well protected in the centre of the hand by adjacent carpal and metacarpal bones. Principally, the capitate articulates with the hamate, scaphoid, trapezoid, and lunate as well as the second, third and fourth metacarpals.

Fractures of the capitate bone are rare and comprise 1% to 2% of all carpal fractures [1, 2]. Typically these fractures are transversely oriented, however, rarely occur in isolation. Isolated capitate fracture is usually due to a direct or indirect axial load to the third metacarpal with a dorsiflexion of the wrist. This results in impaction of the base of the third metacarpal upon the capitate causing fracture of the capitate neck. Typically, a fracture of the capitate is associated with fractures of the scaphoid (‘scaphocapitate syndrome’) or perilunate dislocations. Transscaphoid, transcapitate perilunate fracture/dislocation is believed to occur as a result of the radial styloid impacting upon the scaphoid due to radial deviation and hyperextension at the wrist joint.

Capitate fractures are usually minimally displaced when occurring as an isolated injury. When part of a more complex injury, the fracture can often be displaced leading to delayed or malunion. Bone grafting is often required for treatment of capitate non-union with collapse [3].

Immobilisation is the only required treatment for a non displaced capitate fracture, with a short arm thumb spica cast for a duration of 6-8 weeks. Displaced capitate fractures will require either a Kirschner wire (k-wire) or screw fixation, with possible bone grafting should non-union develop.

Arterial blood supply to the capitate is predominantly via dorsal branches originating from the distal pole. As the capitate lack significant internal anastamoses, the proximal pole is prone to avascular necrosis [4, 5] following fracture. As such, early diagnosis of fractures should be emphasised to avoid AVN, nonunion, and post-traumatic arthritis.
Differential Diagnosis List
Isolated capitate fracture
Capitate fracture
Normal
Vascular channel
Final Diagnosis
Isolated capitate fracture
Case information
URL: https://www.eurorad.org/case/9720
DOI: 10.1594/EURORAD/CASE.9720
ISSN: 1563-4086