Dorsal view left hand

Volar view left hand

Mallet finger is a common sports injury and occurs when the distal end of the extensor tendon (Extensor digitorum or Extensor pollicis longus of thumb) is torn, thereby causing an inability to straighten the distal end of finger.

Injury Mechanism:

• Direct force to finger with forceful flexion to an extended finger

Causes:

• Impaction to finger
• Laceration to extensor side of finger

Presentation:

• Pain
• Deformity with distal phalanx in flexion position with inability to extend distal finger

Clinically:

• Flexion of distal interphalangeal (DIP) joint
• Inability to extend DIP joint

Mallet finger

Type Ⅰ: Closed injury ± small dorsal avulsion fragment
Type Ⅱ: Open injury
Type Ⅲ: Open injury with loss of skin and tendon
Type Ⅳ: Mallet fracture
A: distal phalanx physis injury (Paediatric injury)
B: Fracture fragment with 20-50% articular surface involved
C: Fracture fragment > 50 % articular involved

Investigation:

X-rays:

• Assess proximal bone fragment fracture of the distal phalanx and the articular size (> 40% significant) and if > 2 mm displaced
• CT: Useful for evaluation of fragment

Management:

Nonoperative:

• Keep distal DIP joint in extension using an extension splint (Mallet splint) for 6-8 weeks

Surgery:

• > 40 % articular surface, displaced (>2mm) fragment and volar subluxation of distal phalanx or incongruent joint with subluxation

Surgery options:

• Acute tendon repair
• Acute bone fragment ORIF with pin or screw fixation
• Chronic tear: Swan neck correction with lateral band/FDS tenodesis, Fowler central slip tenotomy
• DIP joint arthrodesis

Mallet splint

Mallet finger screw fixation

Mallet finger K-wire fixation

Small dorsal insertion at entry point of K-wire using X-rays

Insert K-wire at 45° angle and engage distal cortex

Reduce fracture by extension of distal phalanx

Maintain position with additional K-wire or splint

X-ray guidance

Make small dorsal incision at entry point of dorsal K-wire

Use second K-wire parallel to distal phalanx and use as joystick to reduce fracture

Advance dorsal K-wire

Approach: Dorsal

Reduction and fixation with 1-1.3 mm screw fixation

Active wrist ROM after 2 weeks

Finger adduction strengthening

Finger abduction strengthening

Hand grip strengthening