The start of the school year is a fun time – new school supplies, new clothes and new practice schedules for fall sports! The beginning of the school year and sports also tend to correlate with finger injuries. Hitting or “jamming” a finger on a ball, on an opponent or when falling can result in damage in the terminal portion of the extensor digitorum communis muscle (EDC), which extends or straightens the fingers at the metacarpophalangeal joint (MCP) as well as assists in straightening the proximal and distal interphalangeal joints (PIP and DIP).
The EDC begins at the lateral epicondyle of the humerus, at the elbow and travels the back of the forearm, into the hand where it splits into four individual tendons for the index, middle, ring and small fingers where it reaches it’s “terminal” or end on the distal phalanx of each finger.
Injury to the terminal tendon can be immediately identified due to the inability to actively straighten the tip of the finger (DIP). This lack of digit extension is known as a mallet finger. If this is observed, seek medical attention or a hand specialist quickly.
If a mallet finger injury is not properly addressed shortly following the initial injury the tendon is at risk for healing incorrectly or poorly, causing a “swan neck” deformity of the finger. This will cause difficulty with fine motor coordination and strength over time.
Swan neck deformity
The swan neck position occurs due to the structures and strength of the finger flexors relative to the damaged EDC and positioning of supporting ligament structures called lateral bands. Lateral bands maintain PIP joint alignment during finger flexion and extension as well as prevent any hyperextension of the PIP joint. When a mallet finger occurs, the finger flexors overpower the lateral bands and central extensor tendon, causing prolonged hyperextension of the PIP joint – also called “swan neck” deformity.
Mallet finger injuries are most often treated conservatively with splinting for DIP extension or hyperextension for 6-10 weeks depending upon the severity of the injury, patient’s age and medical history and compliance with wearing the splint. Immobilization allows the terminal EDC tendon to scar and heal.
Chronic or delayed healing of a mallet finger injury may require surgical intervention with follow up splinting.
A certified hand therapist will provide excellent splinting and subsequent hand therapy to regain motion and strength as well as decrease pain.