• The term mallet finger refers to injury of the extensor tendon of the distal interphalangeal (DIP) joint, resulting in loss of active extension of the DIP joint and a DIP joint that rests at roughly 45° flexion (1,2).
• The injury can range from partial tear to complete rupture of the extensor tendon, which can cause avulsion of the distal phalanx (mallet finger fracture) (1).
• The mechanism of injury commonly involves a traumatic forced flexion of the distal phalanx when in the extended position (3). A mallet finger can also result from a sharp or crushing laceration to the dorsal DIP joint.
• This injury is commonly encountered in sports following forceful flexion of the distal phalanx.

• Diagnosis of mallet finger injuries can be made with physical examination, history, and radiographs (3).
• Patients will typically present with pain in the affected joint, deformity, and an extensor deficit at the DIP joint. There is often a forced flexion or hyperextension injury of the DIP joint (3).

Mallet injuries can be classified according to the Doyle System (4):

Images accessed from Open-i (https://openi.nlm.nih.gov/detailedresult?img=PMC4807168_aps-43-134-g005&query=&req=4&it=xg) CC BY NC 4.0

The goal of treatment is to restore DIP joint extension and prevent a swan neck deformity (1, 3).

Non-surgical treatment:

• Most mallet finger injuries can be treated non-surgically. Commonly reported indications for non-surgical treatment include closed injury and a fracture fragment size that is < ⅓ of the joint surface area (1,3).
• Non-surgical treatment involves applying a splint on the volar or dorsal aspect of the finger to maintain the DIP joint in extension for 6-8 weeks (1,3). There are many different types of splints that can be used – aluminum foam, plastic, or custom-made thermoplastic – and none have been proven to be superior to another (3,5).
• Complications that can occur from splinting include allergic reaction to tape, skin ulceration, and splint-related pain (6).
• The main challenge with splinting is patient compliance.

Surgical treatment:

• Indications include size of fracture (more than one-third of articular surface involvement) and subluxation of the distal phalanx (1,3).
• Surgical techniques include trans-DIP joint K-wire fixation, open reduction internal fixation with K-wire, and open suture repair of the tendon plus trans-DIP joint K-wire fixation (1).
• Complications that can occur include nail deformity, infection, and hardware failures (1,3).

Figure 1. Splinting of dorsal DIP joint. Image accessed from Open-i (https://openi.nlm.nih.gov/gridquery?q=mallet%20finger&m=1&n=100&it=xg) CC BY NC 4.0

• Referral to plastic surgery for outpatient follow-up.

• Patient can be discharged home with splint and follow-up instructions.

1. Lin JS & Samora JB. Surgical and Nonsurgical Management of Mallet Finger: A Systematic Review. J Hand Surg Am. 2018 Feb;43(2):146-163.e2. Epub 2017 Nov 22. https://doi.org/10.1016/j.jhsa.2017.10.004

   
   

2. Lamaris GA & Matthew MK. The Diagnosis and Management of Mallet Finger Injuries. Hand (N Y). 2017 May;12(3):223-228. Epub 2016 Mar 30. DOI: 10.1177/1558944716642763.

   
   

3. Bloom JMP, Khouri JS, Hammert WC. Current concepts in the evaluation and treatment of mallet finger injury. Plast Reconstr Surg. 2013;132(4):560e-566e.

   
   

4. Doyle JR. Extensor tendons: acute injuries. In: Green DP, Pederson CW, Hotchkiss RN, eds. Green’s Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone; 1999:195-198.

   
   

5. Cheung JPY, Fung B, Ip WY. Review on mallet finger treatment. Hand Surg. 2012;17(3):439-447.

   
   

6. Katzman BM, Klein DM, Mesa J, Geller J, Caligiuri DA. Immobilization of the mallet finger: effects on the extensor tendon. J Hand Surg. 1990;24:80-84.