Types of Finger Dislocation
Finger dislocations are classified primarily by anatomic location (joint involved) and direction of displacement, with the proximal interphalangeal (PIP) joint being most commonly affected, followed by metacarpophalangeal (MCP) and distal interphalangeal (DIP) joints.
Classification by Joint Location
Proximal Interphalangeal (PIP) Joint Dislocations
The PIP joint is the most frequently dislocated joint in the hand 1. These injuries represent a spectrum from simple dislocations to complex fracture-dislocations that can result in permanent deformity if mismanaged 2.
Metacarpophalangeal (MCP) Joint Dislocations
Standard 3-view radiographic examination shows most dislocations of the metacarpals and phalanges 1.
Distal Interphalangeal (DIP) Joint Dislocations
Less common than PIP dislocations but require similar systematic evaluation 1.
Classification by Direction of Displacement
Dorsal Dislocations
- Most common type of finger dislocation 3
- Usually easily reduced with simple traction
- The middle phalanx displaces dorsally relative to the proximal phalanx
- Can occasionally be irreducible due to volar soft tissue interposition, creating a "volar capsular boutonnière" where the condyles of the proximal phalanx buttonhole through volar structures 4
Volar Dislocations
- Less common but more problematic 3
- Often difficult to reduce
- Higher risk of resulting in finger deformity
- May require open reduction if closed methods fail
Lateral Dislocations
- Displacement in the coronal plane (ulnar or radial direction)
- The ulnar two fingers (ring and little) show higher tendency toward ulnar displacement 5
The SCARF Classification System
A comprehensive modern classification system uses five factors to describe any PIP joint dislocation 5:
- Sagittal plane: Dorsal (D), Volar (V), or Neutral (N)
- Coronal plane: Ulnar (U), Radial (R), or Neutral (N)
- Axial force: Compression (C), Traction (T), or None (N)
- Rotational displacement: Supine (S), Prone (P), or Neutral (N)
- Fracture concomitance: Present (+) or Absent (-)
The most common type identified was DUNN (dorsal-ulnar-neutral-neutral without fracture), accounting for 35% of cases 5.
Fracture-Dislocations
These represent a more severe injury pattern requiring specialized management:
- Ring finger shows higher fracture concomitance compared to middle or little fingers 5
- Unstable PIP fracture-dislocations may require reconstruction or fusion if diagnosis is delayed 2
- Involvement of more than one-third of the articular surface typically requires operative fixation 1
Simple vs. Complex Dislocations
Simple Dislocations
- Frequently amenable to early return to play with protection
- Can usually be reduced by closed methods
Complex/Irreducible Dislocations
- May require specialized splinting or surgery 2
- Compound irreducible dorsal dislocations require open reduction combined with debridement 4
- Chronic unreduced dislocations (neglected dislocations) rarely respond to closed reduction due to soft tissue contractures and require extensile surgical approaches 6
Critical Clinical Pitfalls
Failure to recognize certain dislocations or fracture-dislocations may result in permanent deformity and loss of motion 2. Although often dismissed as simple "sprains" by athletes, these injuries represent a spectrum that includes potentially disabling fracture-dislocations requiring prompt recognition and appropriate treatment 2, 3.
Immediate referral to an orthopedic hand specialist is required if:
- The dislocation cannot be reduced
- The finger joint remains unstable following reduction attempts 3
- There is evidence of fracture-dislocation involving significant articular surface