Executive Editor: Chris Colton

Authors: Fiesky Nuñez, Renato Fricker, Matej Kastelec, Terry Axelrod

Proximal phalanx - MCP joint - multifragmentary

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Glossary

1 Principles top

Multifragmentary proximal phalanx MCP joint fracture – plate fixation enlarge

Fracture description

When vertical compression forces, created by axial load, are applied to the finger, comminuted, intraarticular, compression fractures may result. These fractures are very unstable.
Typically, they occur in two configurations:

  • as centrally impacted, comminuted fractures, or
  • with a T- or Y-type fracture geometry.

It is desirable to obtain stable fixation to allow early motion and to minimize the risk of degenerative joint disease.

2 Reduction top

Multifragmentary proximal phalanx MCP joint fracture – plate fixation enlarge

Direct reduction

Compression fractures are not reducible by ligamentotaxis, as the centrally impacted fragments are devoid of soft-tissue attachments.
Direct reduction is therefore necessary.
The key to fixing compression fractures is restoring the joint surface to as close as normal as possible, and supporting the reduction with bone graft and internal fixation.


Multifragmentary proximal phalanx MCP joint fracture – plate fixation enlarge

Disimpact the fragments

Using a K-wire, or dental pick, the fragments are disimpacted and pushed towards the head of the metacarpal, which is used as a template to ensure congruity of the articular surface of the phalanx.
If a cartilage step-off greater than 1 mm remains, degenerative joint disease may follow.

Since the metaphyseal cancellous bone is impacted, a void may be created by its disimpaction.
This jeopardizes the fracture in two ways:

  • this is a very unstable situation in which the fragments may easily redisplace (collapse)
  • the healing process is delayed.

 

3 Bending and contouring the plate top

Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Bending and contouring the plate

T- and Y-shaped fractures
If the plate is not sufficiently contoured to follow the geometry of the concavity of the base of the phalanx, tightening the screws will result in fracture distraction, creating a gap in the opposite cortex.

By overbending the plate, compression can be exerted on the opposite cortex. This may only be applied in fractures with large fragments, never in small-fragment comminution fractures, as the reduction may be compromised (collapse).


Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Comminuted fractures
In comminuted fractures it is important to contour the plate to perfectly fit the bone. Neither compression nor distraction forces should occur through screw tightening, as the reduction would be compromised (collapse).

Pitfall
If compression is exerted on the comminuted zone in the sagittal plane by overbending the plate, angulation of the finger will result.

4 Fixation top

Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Plate application

The plate is placed dorsally on the phalanx, as proximally as possible, without interfering with the joint.
Ensure that the plate is centered on the long axis of the diaphysis.


Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Drilling

Using a drill guide, carefully drill a first hole for a screw through the transverse part of the plate with a 1.0 mm drill bit.
Repeat for the second hole in the transverse part.

Pitfall
Be sure not to injure the flexor tendons and digital artery and nerve.


Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Measurement

Use a depth gauge to determine screw length.


Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Screw insertion (proximal)

Insert the first screw. Ensure that it engages the far cortex but does not protrude into the fibro-osseous flexor digital channel, where the flexor tendons run. The digital nerve and artery are also at risk of injury.
Insert a second screw into the opposite end of the transverse plate section, in the same fashion, alternately tightening both screws.


Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Pitfall: bad plate adaptation

Check for perfect adaptation of the plate to the diaphysis and metaphysis. If it is not perfectly adapted, take out the screws and recontour the plate to avoid fracture displacement, or malrotation.


Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Pitfall: Interfering screws

Conflict of tips of the screws in the transverse part of the plate and joint penetration must be avoided.


Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Drill for distal screw

Use a drill guide and 1.0 mm drill bit to prepare an eccentric hole for the distal plate screw.


Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Measure screw length

Use a depth gauge to determine screw length.


Multifragmentary proximal phalanx MCP joint fracture – T-plate fixation enlarge

Screw insertion

Insert the distal, self-tapping screw and tighten it.
Prepare and insert another, more proximal diaphyseal screw, in the same fashion.

v1.0 2008-11-08