What to do for inability to extend the DIP (Distal Interphalangeal) joint of the 4th finger?

Mallet Finger: Immediate Splinting and Radiographic Evaluation Required

You are dealing with a mallet finger—inability to extend the DIP joint of the 4th finger—and the immediate priority is continuous splinting in extension and obtaining a 3-view radiograph to determine if surgical intervention is needed. 1

Immediate Management (First Steps)

• Apply ice-water mixture for 10-20 minutes with a thin towel barrier to reduce swelling and pain, but never attempt to manually straighten the finger before proper splinting 1, 2
• Splint the DIP joint in the position found (or slight hyperextension if tolerated) immediately and maintain this until definitive evaluation 1
• Avoid heat application entirely—only cold therapy is recommended for initial management 1

Critical Diagnostic Step: Radiographs

Obtain a 3-view radiograph of the injured finger immediately to differentiate between tendinous mallet finger (extensor tendon rupture) and bony mallet finger (avulsion fracture), as this determines your entire treatment pathway 1, 2

Surgical Indications on X-ray (Requires Immediate Orthopedic Referral):

• Avulsion fracture involving ≥1/3 of the articular surface 1, 2
• Palmar (volar) subluxation of the distal phalanx—this is an absolute surgical indication even with small fracture fragments 1, 2
• Interfragmentary gap >3mm 1, 2
• Displacement >3mm 2
• Open injuries 1

Delaying radiographs can lead to missing fractures that require surgery, making conservative treatment ineffective 1

Non-Surgical Management (If No Surgical Indications)

Continuous uninterrupted splinting for 6-8 weeks is the cornerstone of treatment for tendinous mallet finger or small non-displaced avulsion fractures 1

Critical Splinting Rules:

• Even brief removal of the splint (even for seconds) restarts the entire healing timeline—this is the most common cause of treatment failure 1
• The DIP joint must remain in extension or slight hyperextension continuously 1
• Begin active finger motion exercises of the PIP and MCP joints immediately while keeping the DIP splinted to prevent stiffness in adjacent joints 1

Common Pitfall to Avoid:

Patients often remove splints to "check" the finger or clean it—educate the patient that any interruption in immobilization requires restarting the 6-8 week clock 1

Follow-Up and Red Flags

• Re-evaluate immediately if unremitting pain develops during immobilization, as this may indicate inadequate fixation, skin breakdown, or other complications 1, 2
• Obtain repeat radiographs at 10-14 days to ensure fracture position is maintained (if bony injury present) 3
• After the immobilization period, aggressive early motion exercises are mandatory to restore function 2

Expected Outcomes

• Most tendinous mallet fingers heal successfully with continuous splinting 1
• Some residual extensor lag (5-10 degrees) is common but typically does not affect function 2
• Surgical cases have variable outcomes depending on fracture pattern and joint stability 2