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SplintER Series: A Rare Cause of Traumatic Thumb Pain

Posted by Victor Huang, MD on

A 45 year-old male presents with right thumb pain and deformity after falling off his bicycle. You obtain hand x-rays and see the following images. What is the most likely diagnosis, differential diagnosis, and management plan?

Figure 1. AP and oblique views of the hand. Author’s own images.

1. What is your diagnosis? Bonus - What is the additional radiographic diagnosis?

  • Dislocation of the first carpometacarpal (CMC) joint.
  • Pearl: CMC dislocations account for less than 1% of all hand injuries [1,2]. Isolated dislocations are even more uncommon, and are usually associated with Bennett, Rolando, and carpal fractures [1-4]. The majority of dislocations are dorsal [2,4]. Misdiagnosis or delayed treatment may result in joint instability, early degeneration of the articular cartilage, and decreased grip strength [1-5].
  • Bonus: There are two other interesting findings on this radiograph. First, there is a well corticated osseous fragment at the base of the second proximal phalanx that is likely a chronic fracture deformity. Second, there is a metallic foreign body between the third and fourth metacarpal heads that is possibly a BB gun pellet.

2. What is the mechanism of injury?

  • Thumb CMC dislocations are often caused by axial loading of the thumb in a flexed position, and less commonly, direct force into the webspace between the first and second digits [1-4].

3. What physical exam findings are expected?

  • Exam findings include painful and limited range of motion of the thumb and often subtle deformity and swelling over the dorsoradial side of the hand [1,4].

4. Which imaging modalities can be used?

  • Plain radiographs should be taken of the hand with AP, lateral, and oblique views [1-3]. Stress views and CT scan may also be helpful to identify other injuries, as thumb CMC dislocations are rarely isolated [1,2].

5. What is your management plan?

  • The CMC dislocation should be anesthetized with an intra-articular injection, and then closed reduction should be performed with traction [1,4].
  • Immobilize the joint with a thumb spica splint with the first metacarpal held in abduction and extension with the wrist in pronation. Closed reduction is often unstable [1-6].
  • The patient should have follow-up arranged with a Hand Specialist within 3-4 days [1,7].

Figure 2. Post-reduction XR that showed interval reduction of the first CMC joint with normal alignment. Author’s own images.

6. When would you consult orthopedics in the ED?

  • Orthopedics should be immediately consulted for a thumb CMC dislocation if there is an open fracture-dislocation, neurovascular compromise, or irreducible dislocation.

7. What is the definitive management of this injury?

  • There is debate over the optimal treatment strategy, and several studies have compared nonoperative and operative treatment [4].
  • Nonoperative management: immobilization in a short arm thumb spica cast for 4-6 weeks [2].
  • Operative treatment: closed reduction and percutaneous fixation with Kirschner wires for 5-6 weeks [3-7].
  • Patients who experience persistent instability may require ligamentous reconstruction [3-5].

For more cases like these, check out the SplintER archives.

References

  1. Kraus CK, Weaver KR. Traumatic Dislocation of the First Carpometacarpal Joint. Am J Emerg Med. 2014;32(12):1561. PMID: 24993682
  2. Lahiji F, Zandi R, Maleki A. First Carpometacarpal Joint Dislocation and Review of Literatures. The Archives of Bone and Joint Surgery. 2015;3(4):300-303. PMID: 26550598
  3. Atkinson R. Hand. DeLee & Drez’s Orthopaedic Sports Medicine: Principles and Practice. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2009: 1386-1398.
  4. Fotiadis E, Svarnas T, Lyrtzis C, Papadopoulos A, Akritopoulos P, Chalidis B. Isolated Thumb Carpometacarpal Joint Dislocation: A Case Report and Review of the Literature. J Orthop Surg Res. 2010;5(16):1-5. PMID: 20219137
  5. Mailhot T, Lyn ET. Hand. Rosen’s Emergency Medicine Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier Saunders; 2014: 555-556.
  6. Horn AE, Ufberg JW. Management of Common Dislocations. Roberts & Hedges’ Clinical Procedures in Emergency Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2014: 981-984.
  7. Raukar NP, Raukar GJ, Savitt DL. Extremity Trauma. The Atlas of Emergency Medicine. 4th ed. New York, NY: McGraw-Hill; 2016: 298-300.

Author information

Victor Huang, MD

Department of Emergency Medicine
New York-Presbyterian Queens
Weill Cornell Medical College

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