Interphalangeal joint dislocations can be closed or open or closed
Distal Interphalangeal Joint Dislocations
Distal interphalangeal joint of the hand have complex motion patterns that are different for each finger and designed to ensure conformity when the hand surrounds an object.
Most of the dislocations are reducible by closed methods.Irreducible dislocations of the DIP joint occur due to
- Volar plate entrapment
- Flexor digitorum profundus is trapped behind a single condyle of middle phalanx
- Middle phalanx is buttonholed through the volar plate
- Middle phalanx is buttonholed through a rent in the FDP
- The extensor tendon is displaced around the head of middle phalanx
The diagnosis may be evident clinically or on routine xrays.
Treatment of Interphalangeal Joint Dislocations
Treatment options available are
- Closed reduction and internal fixation
- Open reduction and internal fixation
Reducible stable dislocations are allowed to begin immediate active range of motion.
Reducible but unstable dorsal dislocation are immobilized in 20 degrees of flexion for up to 3-4 weeks followed by mobilization.
In unstable cases which cannot be managed by splinting, Kwire fixation is done.
Open dislocations, delayed presentations, failed splinting with subluxated joints require open reduction and internal fixation.
Proximal Interphalangeal Joint Dislocations
The head of the proximal phalanx is bicondylar and the collateral ligaments arise from the center axis of joint rotation. Collateral ligaments are the primary stabilizers to lateral stress and dislocations are associated with disruption in lateral collateral ligament
The proximal interphalnageal joint receives static stability from the proper and accessory collateral ligaments and the volar plate. It is further supplemented by the dynamic stability of the dorsal plate and balanced tendon forces acting across the joint.
Some of the dislocation may be subtle and missed. These should be diagnosed on stress views.
Other patterns of dislocation are
- Dorsal dislocation
- Pure volar dislocation
- Rotatory volar dislocation
Dorsal dislocations are the one where the distal fragment moves towards dorsal side. It also causes volar plate injury.
Pure volar dislocations are said to occur when the distal fragment has moved to volar side and there is no associated rotation of the fragment. Associated volar plate, collateral ligament, and the central slip of extensor tendon may occur.
Rotatory volar dislocation occurs as the head of proximal phalanx passes between the central slip and the lateral bands. This can prevent reduction.
Routine AP, lateral and oblique views would diagnose most of the dislcoations but the subtle ones which require stress views.
For collateral ligament injury with dislocation on stress views, splinting alone would suffice.
For clear cut dislocations, closed reduction and splinting for stable dislocations and closed reduction and internal fixation [kwire] for unstable ones.
Open injury and irreducible dislocation would require open reduction and internal fixation.
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