first metacarpal fracture

Click image to enlarge view

A 22 year-old male was playing football when he fell, landing on his outstretched left arm with his thumb flexed. He now has pain at the base of his thumb. This AP view of the hand best demonstrates the injury (photo credit).

What is this fracture, what additional imaging is needed, and what should be the management plan?

 

 

Bennett Fracture

This is a partial intra-articular fracture at the base of the 1st metacarpal where it interacts with the trapezium (carpo-metacarpal joint). The single fracture fragment in the xray is displaced in a medial and palmar direction.

A true AP (Robert’s view) and true lateral carpo-metacarpal (CMC) view

  • Place a thumb spica splint with IP joint in extension
  • Counsel the patient of long-term consequences of malunion or post-traumatic arthritis, especially if they do not seek specialty care.
  • Counsel the patient on the risk of thenar atrophy, if in prolonged immobilization.

Bennett fractures will typically require reduction and fixation if there is an articular step-off/displacement > 1 mm. He should follow up with an orthopaedics/hand surgeon as an outpatient within 2-3 days.

First Metacarpal Fractures [1, 2]

Mechanism

  • Fall on hand with thumb in flexion and axial loading of the first metacarpal

Physical Exam

  • Tenderness to palpation of the first metacarpal
  • Swelling over the radial aspect of the hand

Classifications (Figure 1)

  • Extraarticular
  • Intraarticular
    • Bennett Fracture: A partial intra-articular fracture at the base of the 1st metacarpal with a single fracture fragment displaced to the medial and palmar aspect of the bone
    • Rolando Fracture:– A complete and comminuted intraarticular fracture, usually in a T or Y shape

Figure 1. Demonstration of first metacarpal fractures
(Original images used with permission from Dr. Jeffrey Daniels)

Management

  • Thumb spica splint with IP joint in extension (Figure 2)
  • Extraarticular
    • Up to 20-30 degrees of angulation may be tolerated and managed conservatively
    • Outpatient follow-up with hand surgery within 1 week (sooner if severely angulated)
  • Intraarticular
    • Urgent (≤3 days) follow-up with hand surgery clinic for likely operative fixation
  • As always, call an orthopedist emergently, if there is an open fracture or neurovascular compromise

Figure 2. Demonstration of thumb spica splint with interphalangeal joint in extension
(Illustrated by Dr. Tabitha Ford)

For more cases like these, you can subscribe to the Ortho EM Pearls email series hosted by Drs. Will Denq, Tabitha Ford, and Megan French, who have kindly shared some of their content with ALiEM.

References

  1. Mailhot T, Lyn E. Hand. In: Marx J, ed. Rosen’s Emergency Medicine Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier, Saunders; 2014: 534-569.e2
  2. Diaz-Garcia R, Waljee J. Current management of metacarpal fractures. Hand Clin. 2013;29(4): 507-518. doi: 10.1016/j.hcl.2013.09.004.
Tabitha Ford, MD

Tabitha Ford, MD

Chief Resident
Department of Emergency Medicine
University of Utah