MALLET FINGER

Description:

Mallet Finger is an avulsion of the extensor tendon at it’s attachment to the base of the distal phalanx of the digit.  There is a visible deformity at rest with the patient being unable to hold the affected dorsal interphalangeal (DIP) joint in extension.  This will persist if left untreated.  There are two types:  i) Tendinous form – where the extensor tendon has ruptured and ii) Bony form – where the extensor tendon at its attachment to the base of the distal phalanx has avulsed. (1)

Injury Mechanism:

This injury usually results as the name implies via an axial loaded force to an extended proximal interphalangeal (PIP) that results in forced flexion of the distal phalanx.

Exam:

Inspection – Swelling over DIP joint.  There may not be a visible deformity in acute cases.

Palpation – Tender to palpation over DIP joint

AROM – Unable to extend DIP joint in complete tears, may be slow to extend in partial tears.

AROM v. Resistance – Unable to extend DIP joint versus resistance in complete tears.  Reduced power in extension in partial tears.

PROM – Extension of DIP may be limited due to effusion in the joint.

Investigations:

Xray – Lateral image of affected digit to assess for avulsion fracture.

US – if xray is normal, US can demonstrate a rupture of the extensor tendon.

Management: 

Stack Splint or dorsal extension splint (see Figure 1) that holds DIP in extension for 6-12 weeks (1-4)

**** It is very important to instruct the patient that when changing splint or cleaning finger to maintain and hold DIP in extension. ****

Figure 1 – Splints for Mallet Finger – Dorsal extension splint (top) and Stack splint (bottom)

Compliance can be poor due to duration of splinting, regiment required for removing splint and cleaning finger, and thus frequent follow up is recommended.

Chronic injuries lasting greater than 12 weeks usually require surgical repair. (2)

Dr. Neil Dilworth CCFP Dip Sport Med (April 30, 2014  PR KA)

References:

(1) Bridgeforth GM. Lippincott’s primary care musculoskeletal radiology. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins Health; 2011.

(2) Review of orthopaedics. 5th ed. ed. Philadelphia: Saunders / Elsevier; 2008.

(3) The 5-minute sports medicine consult. 2nd ed. ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2011.

(4) Eiff MP. Fracture management for primary care. 2nd ed. ed. Philadelphia: Saunders; 2003.