Overview
Mallet Finger
1. Clinical Overview
Summary
Mallet Finger (or "Baseball Finger") is the loss of active extension at the Distal Interphalangeal (DIP) Joint due to disruption of the terminal extensor tendon at its insertion into the distal phalanx. The injury occurs when a sudden forceful flexion is applied to an actively extended DIP joint (e.g., A ball striking the fingertip). This causes either tendon rupture (Soft tissue Mallet) or avulsion fracture of the dorsal base of the distal phalanx (Bony Mallet). The finger rests in a characteristic flexed position at the DIP joint, and the patient is unable to actively extend it. The vast majority of Mallet injuries are treated non-operatively with continuous splinting of the DIP joint in extension (Or slight hyperextension) for 6-8 weeks. Surgery is reserved for specific indications: large bony fragments (>30% articular surface), Volar subluxation, Or failed non-operative management. With appropriate treatment, Outcomes are generally good. [1,2,3]
Clinical Pearls
"Can't Straighten the Tip": The patient has a flexed DIP joint and cannot actively extend it.
"Splint, Splint, Splint – Continuously": The DIP must be held in extension (Or 0-10° hyperextension) for 6-8 weeks. ANY flexion restarts the clock.
"Bony vs Soft Tissue": X-ray differentiates. Bony Mallet has an avulsion fragment. Both treated with splinting unless large fragment or subluxation.
"Don't Hyperextend the PIP": The splint should allow PIP movement. Hyperextending it causes a Swan Neck deformity.
2. Epidemiology
Demographics
| Factor | Notes |
|---|---|
| Incidence | Common finger injury. Often underreported. |
| Age | Any age. Common in young athletes and middle-aged individuals. |
| Sex | Slight male predominance (Sports, Manual work). |
| Digits Affected | Long finger and Ring finger most common. Dominant hand. |
Mechanism
| Mechanism | Notes |
|---|---|
| Forced Flexion of Extended DIP | Most common. Ball striking fingertip (Baseball, Cricket, Basketball, Netball). |
| Direct Blow to Dorsal Fingertip | |
| Low-Energy (Bedsheet Injury) | Tucking in bedcovers. Common in elderly. |
| Crush Injury | May be open. |
3. Anatomy
Extensor Mechanism at DIP
- Terminal Extensor Tendon: The conjoined lateral bands of the extensor mechanism insert onto the Dorsal Base of the Distal Phalanx.
- This tendon extends the DIP joint.
- Disruption = Loss of active DIP extension.
Mallet Finger Types
| Type | Pathology |
|---|---|
| Tendinous (Soft Tissue) Mallet | Rupture of the terminal extensor tendon. No fracture. |
| Bony Mallet | Avulsion fracture of the dorsal base of the distal phalanx (Tendon pulls off a fragment of bone). |
4. Classification
Doyle Classification
| Type | Description |
|---|---|
| Type I | Closed injury. Tendon rupture OR Small avulsion fracture (less than 30% articular surface). Most common. |
| Type II | Open injury (Laceration of tendon). |
| Type III | Open injury with loss of skin/Tendon substance. |
| Type IVA | Bony Mallet in a child (Epiphyseal fracture – Seymour fracture pattern may be associated). |
| Type IVB | Bony Mallet with fracture involving >30% articular surface (Often associated with volar subluxation). |
| Type IVC | Bony Mallet with fracture involving >30% + Volar Subluxation of distal phalanx. |
Key Distinction
| Feature | Splinting Likely Sufficient | Surgery May Be Needed |
|---|---|---|
| Fracture Size | less than 30% articular surface | >30% articular surface |
| Subluxation | No volar subluxation | Volar subluxation of distal phalanx |
| Type | I, II (Tendon repair possible) | IVB, IVC |
5. Clinical Presentation
History
| Feature | Notes |
|---|---|
| Mechanism | Ball striking fingertip. Stubbing finger. Tucking sheets. |
| Immediate | Unable to straighten tip of finger. |
| Pain | Usually mild. At DIP joint. |
| Swelling | Dorsal DIP. |
Examination Findings
| Finding | Notes |
|---|---|
| Flexed DIP Joint | At rest, DIP is flexed ~30-40°. |
| Active Extension Lag | Cannot actively extend DIP to neutral. (May achieve some extension but not full). |
| Passive Extension | Full passive extension is possible (Tendon is ruptured, Not joint pathology). |
| Tenderness | Dorsal DIP. |
| Swelling | Dorsal. May be subtle or significant (If bony). |
Complications to Look For
| Finding | Indicates |
|---|---|
| Volar Subluxation of Distal Phalanx | Large bony fragment (IVB/C). The joint is unstable. X-ray essential. |
| Open Wound | Open Mallet (Type II/III). |
| Swan Neck Deformity (Late) | If untreated. Hyperextension of PIP, Flexion of DIP. |
6. Investigations
Imaging
| Modality | Notes |
|---|---|
| X-Ray (Lateral of Finger) | Essential. Differentiates tendinous from bony Mallet. Assesses fracture size (% articular surface). Look for Volar Subluxation of distal phalanx. |
X-Ray Interpretation
| Finding | Significance |
|---|---|
| No Fracture | Tendinous Mallet. Splint. |
| Small Avulsion (less than 30%) | Small bony Mallet. Splint. |
| Large Avulsion (>30%) | May cause joint instability. Consider surgery. |
| Volar Subluxation | Distal phalanx subluxed volarly (Palmarly). Unstable. Surgery likely needed. |
7. Management
Management Algorithm
MALLET FINGER
(Flexed DIP, Cannot actively extend tip)
↓
X-RAY (Lateral of Finger)
┌────────────────┴────────────────┐
TENDINOUS / SMALL BONY LARGE BONY (>30%)
MALLET (less than 30% articular) +/- VOLAR SUBLUXATION
↓ ↓
**SPLINTING** **CONSIDER SURGERY**
(Hand Surgery referral)
↓
NON-OPERATIVE MANAGEMENT
┌──────────────────────────────────────────────────────────┐
│ **DIP SPLINT IN EXTENSION** │
│ │
│ - Splint Type: Stack splint, Mallet splint, Alumafoam, │
│ Custom thermoplastic splint │
│ - Position: DIP in 0° (Neutral) to 10° Hyperextension │
│ (Do NOT over-hyperextend – Skin necrosis risk) │
│ - Duration: **6 weeks full-time** (Then 2 weeks nigh- │
│ time only) │
│ - PIP MUST be free (Allow full PIP movement) │
│ - Bony Mallet: May need 8 weeks │
│ │
│ **CRITICAL**: │
│ - DIP must NOT flex AT ALL during splinting period. │
│ - To clean/Change splint: Keep finger supported in extension│
│ on a flat surface. Never let DIP flex. Any flexion = Restart.│
│ - Skin checks for maceration/Pressure sores. │
└──────────────────────────────────────────────────────────┘
↓
SURGICAL OPTIONS (For Large Bony Mallet / Subluxation)
┌──────────────────────────────────────────────────────────┐
│ - **Extension Block Pinning (Ishiguro Technique)** │
│ - **ORIF with Screw/K-Wire** │
│ - **Transfixion K-Wire through DIP in Extension** │
│ - Late/Chronic: May need Tendon reconstruction or │
│ Arthrodesis (DIP fusion) │
└──────────────────────────────────────────────────────────┘
Splinting Technique
| Aspect | Details |
|---|---|
| Position | DIP in 0° (Neutral) or up to 10° hyperextension. Check skin perfusion. |
| Duration | 6 weeks continuous (8 weeks for bony). Then 2 weeks night-time. |
| PIP | Must be FREE. Only the DIP is splinted. |
| Compliance | Critical. DIP must NOT flex during entire splinting period. If flexion occurs → Restart the 6-8 weeks. |
| Skin Care | Check for maceration. Change splint carefully (Keep DIP extended on flat surface). |
Splint Types
| Splint | Notes |
|---|---|
| Stack Splint | Pre-formed plastic. Sizes available. Common. |
| Alumafoam Splint | Malleable foam-covered aluminium. Custom fit. |
| Thermoplastic | Custom moulded by hand therapist. |
| Dorsal Splint | Alternative. May be preferred for hygiene. |
8. Complications
| Complication | Notes |
|---|---|
| Residual Extensor Lag | Some degree common (~5-10° lag). Usually functionally acceptable. |
| Swan Neck Deformity | If untreated/Chronic. Hyperextension at PIP, Flexion at DIP. Due to imbalance. May need surgery. |
| Skin Maceration | Under splint. Keep dry. Air periodically (With DIP extended). |
| Skin Necrosis | If over-hyperextended. Check perfusion. |
| Non-Compliance | Any flexion resets healing. Poor outcomes. |
| Stiffness | Usually minor. PIP must be exercised during splinting. |
| Infection (Open Injury) |
9. Prognosis and Outcomes
| Factor | Notes |
|---|---|
| Tendinous Mallet | Good outcomes with compliant splinting. ~70-90% achieve full or near-full extension. |
| Bony Mallet (Small) | Good outcomes. Fracture heals. |
| Large Bony / Subluxation | Variable. May need surgery. Depends on joint congruity. |
| Delayed Presentation | Can still be splinted (Even up to 3 months). Outcomes less predictable. |
| Chronic Untreated | Swan Neck deformity. May need tendon reconstruction or DIP fusion. |
10. Evidence and Guidelines
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Mallet Finger | BSSH / BOA | Splinting is first-line. Surgery for large bony fragments (>30%) with subluxation. |
Evidence Points
- Splinting vs Surgery (For Most Mallet Fingers): No difference in outcomes for Type I Mallet. Splinting preferred.
- Chronic Mallet: Splinting can still be tried. Lower success rate.
11. Patient and Layperson Explanation
What is Mallet Finger?
Mallet finger happens when the tendon that straightens the tip of your finger is injured. This can be from a ball hitting your fingertip, Or catching your finger on something. The tip of your finger drops down and you can't straighten it yourself.
Is it serious?
It's a common injury and usually heals well with the right treatment. If not treated, It can lead to a permanent bent finger (Swan neck deformity).
What is the treatment?
- Splinting: Your finger tip needs to be held straight in a splint for 6-8 weeks, 24 hours a day, 7 days a week.
- You cannot let it bend at all during this time. If it bends, Even once, The healing starts again.
- The middle joint of your finger should still move during this time.
- Surgery: Only needed if there is a large piece of bone broken off or if the joint is unstable.
What can I do?
- Keep the splint on at all times.
- When you need to clean your finger or change the splint, Keep it resting flat on a table so it doesn't bend.
- Move the other joints of your finger to stop them getting stiff.
- Check the skin for any soreness.
12. References
Primary Sources
- Doyle JR. Extensor tendons – Acute injuries. In: Green's Operative Hand Surgery. 6th ed. 2011.
- Handoll HH, Vaghela MV. Interventions for treating mallet finger injuries. Cochrane Database Syst Rev. 2004;(3):CD004574. PMID: 15266538.
- Pike J, et al. Extension splinting for acute mallet finger: A systematic review. J Hand Surg Am. 2010;35(11):1857-1863. PMID: 21050650.
13. Examination Focus
Common Exam Questions
- Anatomy: "What structure is injured in Mallet Finger?"
- Answer: Terminal Extensor Tendon (Insertion at dorsal base of distal phalanx).
- Treatment: "What is the standard treatment for most Mallet Fingers?"
- Answer: Continuous DIP Extension Splinting for 6-8 weeks.
- Surgery Indication: "When is surgery indicated?"
- Answer: Bony Mallet with >30% articular surface involvement or Volar subluxation of the distal phalanx.
- Late Complication: "What deformity can develop if Mallet Finger is untreated?"
- Answer: Swan Neck Deformity (PIP hyperextension + DIP flexion).
Viva Points
- 6-8 Weeks Continuous: No flexion allowed. Any flexion = Restart clock.
- PIP Must Be Free: Only DIP is splinted. PIP should move.
- Check X-Ray: Size of fracture fragment, Subluxation.
- Doyle Classification: Type I (Closed, Small/Tendinous), Type IV (Bony – A/B/C).
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.