Hand / Fingers
Mallet Finger (Terminal Extensor Rupture)
망치 손가락 (말단 신전건 파열)
Terminal extensor tendon rupture causing DIP to drop into flexion
- How common
- Common in sports/occupational injury
- Typical age
- All ages, peak 30–50
What is it?
Terminal extensor tendon ruptures or avulses bony fragment at distal phalanx base, eliminating active DIP extension.
Commonly affected: Ring, middle, and little fingers most common
How it develops
- Sudden Flexion ForceFlexion force applied to extended fingertip
- Terminal Tendon RuptureTendon substance tear or bony avulsion
- Loss of DIP ExtensionActive DIP extension lost
- Mallet DeformityCharacteristic flexed DIP posture
Symptoms
- Loss of active DIP extensionCannot actively extend DIP
- Flexed DIP postureDIP held in 25–40° flexion
- Dorsal pain/swellingDorsal DIP after acute injury
- Risk of swan neckUntreated may develop PIP hyperextension
- Passive extension preservedPassive extension is full
How it is examined
- DIP extension lagMeasure extension lag (20–40°)
- Dorsal tendernessTenderness over dorsal DIP
- Bony fragment assessmentLateral X-ray for avulsion fragment
- Joint subluxation checkRule out volar subluxation
Imaging
Lateral X-ray essential — avulsion fragment at dorsal base of distal phalanx.
- Dorsal avulsion fragment (present or absent)
- Flexed DIP
- Articular involvement (>30% = surgical)
- Volar subluxation check
MRI helpful for tendinous (non-bony) mallet; rarely needed.
- Terminal tendon rupture
- Tendon gap
- DIP edema
Non-surgical care
- DIP extension splint (6–8 wk)Continuous 24hr extension, no breaks
- Stack or aluminum splintImmobilize DIP only, free PIP
- Weaning protocolGradual weaning over 2–4 weeks
- ROM/strength rehabStaged exercises after splint weaning
Conservative options are generally tried first. Medications listed here can have side effects — discuss them with your prescriber.
When surgery is considered
Articular fragment >30%, volar subluxation, failed conservative
Procedures that may be discussed
- K-wire fixation
- Screw fixation (ORIF)
- Tendon repair (chronic)
Outlook
Early splinting gives >80% good outcomes; neglected cases develop chronic deformity.