Figure. Anteroposterior radiograph shows an isolated ulnar styloid fracture.
A 22-year-old woman presents with right wrist pain after being involved in an altercation the day before. She reports being struck on the wrist and immediately had pain and difficulty lifting the right hand. On physical examination, the patient has mild swelling and pain over the ulnar side of the right wrist; the pain is made worse with ulnar deviation of the wrist. Radiograph of the wrist shows an isolated ulnar styloid fracture.
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The ulnar styloid is a bony projection of the distal ulnar that serves as an attachment site for distal radial and ulnar joint ligaments (DRUJ) and the triangular fibrocartilage complex (TFCC).1-3 Isolated ulnar styloid fractures are rare as they usually occur in association with distal radius fractures. Although the nonunion rate for ulnar styloid fractures can be as high as 63%, they rarely cause DRUJ instability or require surgical fixation.3
Treatment of minimally displaced fractures includes a short arm cast for 6 weeks.3 The size and amount of displacement of the ulnar styloid fracture is the best predictor of resulting DRUJ instability. Fractures can occur (from smallest to largest) at the tip, base, or the larger fovea.1 Fractures occurring at the tip are the most common and least likely to cause instability. Fractures with >2 mm of displacement are more likely to cause DRUJ instability.3 Displaced ulnar styloid fractures can increase the likelihood of symptomatic abutment to the carpus. Evidence of DRUJ instability includes a positive Ballottement test, widening of the DRUJ on anteroposterior radiograph, and radioulnar distance of more than 6 mm on lateral view radiograph.1-3
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants.
1. Maniglio M, Park IJ, Zumstein M, Kuenzler M, McGarry MH, Lee TQ. The critical size of ulnar styloid fragment for the DRUJ stability. J Wrist Surg. 2021;10(5):385-391. doi:10.1055/s-0041-1726309
2. Mirghasemi AR, Lee DJ, Rahimi N, Rashidinia S, Elfar JC. Distal radioulnar joint instability. Geriatr Orthop Surg Rehabil. 2015;6(3):225-229. doi:10.1177/2151458515584050
3. Logan AJ, Lindau TR. The management of distal ulnar fractures in adults: a review of the literature and recommendations for treatment. Strategies Trauma Limb Reconstr. 2008;3(2):49-56. doi:10.1007/s11751-008-0040-1