Management of DIP Joint Subluxation of the Index Finger
For subluxation of the distal interphalangeal joint of the 2nd digit, attempt closed reduction first; if unsuccessful or if there is associated fracture involving >1/3 of the articular surface, palmar displacement of the distal phalanx, or interfragmentary gap >3mm, proceed to open reduction with internal fixation.
Initial Assessment and Imaging
Begin with 3-view radiographs (PA, lateral, and oblique projections) of the affected finger 1. This is critical to:
- Identify associated fracture fragments
- Assess articular surface involvement
- Detect volar subluxation or displacement patterns
- Rule out mallet finger with bony avulsion
The oblique view is particularly important as it increases diagnostic yield for phalangeal fractures 1.
Treatment Algorithm
Simple Subluxation Without Fracture
Attempt closed reduction immediately:
- Apply longitudinal traction to the distal phalanx
- Flex the PIP joint to 90° while extending the DIP joint—this relaxes the oblique retinacular ligament and facilitates reduction 2
- If reducing multiple joint dislocations, start at the DIP level first to relax the flexor digitorum profundus tendon 3
If closed reduction is successful:
- Immobilize for 3 weeks
- Begin rehabilitation exercises thereafter
- Monitor for joint stability 3
Irreducible Subluxation
Proceed to open reduction via volar approach 4, 5. This approach offers:
- Better wound healing
- Easier release of entrapped structures
- Ability to repair volar plate, collateral ligaments, and flexor tendons
Common causes of irreducibility include:
- Volar plate interposition 5
- Flexor digitorum profundus tendon entrapment behind the middle phalanx head 5, 6
- Ulnar condyle entrapment between partially torn extensor tendon and volarly displaced oblique retinacular ligament 2
- Buttonholing of middle phalanx head through volar plate or flexor tendon 4, 5
Fracture-Subluxation
Operative indications 1:
- Articular surface involvement >1/3 (typically averaging 55-60% in fracture-dislocations) 7
- Palmar displacement of the distal phalanx
- Interfragmentary gap >3mm
- Persistent joint instability after closed reduction
Surgical technique for fracture-dislocations:
- Use volar mini-plate fixation for rigid stabilization 7
- Place extension block pin into middle phalangeal head for dorsal stability
- This allows early postoperative joint motion (critical for preventing stiffness)
- Expected outcomes: DIP flexion averaging 71°, excellent Strickland scores, and 98% total active motion 7
Critical Pitfalls to Avoid
Do not accept residual articular step-off >2mm—this leads to post-traumatic osteoarthritis 1. While the evidence for mallet fractures shows insufficient support for operative over nonoperative treatment 8, fracture-dislocations with significant articular involvement require anatomic reduction to preserve long-term function.
Do not delay diagnosis—functional impairment increases with delayed treatment 1. If initial radiographs are equivocal but clinical suspicion remains high, obtain CT without contrast to exclude occult fractures 1.
Assess for concomitant injuries:
- Flexor digitorum profundus avulsion (requires urgent surgical repair) 6
- Collateral ligament rupture (may require mini-anchor repair if causing instability) 9
- Extensor tendon injuries (check for bone involvement on radiographs) 1