Executive Editor: Chris Colton

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

Proximal phalanx - MCP joint - collateral ligament avulsion

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Glossary

1 Principles top

Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Avulsion fractures

Avulsion fractures are the result of side-to-side (coronal) forces acting on the finger, putting the collateral ligament under sudden tension. The ligament is usually stronger than the bone, causing the ligament to avulse a fragment of bone at its insertion.
Avulsion fractures result in marked joint instability.
If the fracture is not displaced, nonoperative treatment is usually indicated (buddy taping to the adjacent finger). Displaced fractures, however, must be internally fixed.

Only avulsion fractures with large fragments can be treated with lag screws.


Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Use of lag screw

Be sure to insert the screw as a lag screw, with a gliding hole in the near (cis) cortex, and a thread hole in the far (trans) cortex.
Inserting a screw, across a fracture plane, that is threaded in both cortices (position screw) will hold the fragments apart and apply no interfragmentary compression.

2 Reduction top

Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Indirect reduction

Reduction is achieved by pulling the finger laterally, in the direction opposite to the forces that created the fracture, and into MCP flexion, as necessary, to approximate the fragment. The avulsed fragment is pushed into place by the surgeon’s thumb.Reduction is achieved by lateral pulling of the finger in the opposite direction of the forces that created the fracture, and by MP flexion necessary for the approximation of the fragment. The avulsed fragment is pushed into place by the surgeon’s thumb.


Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Direct reduction

In displaced fractures, open reduction is often necessary after preparation of a gliding hole (see later).
A small pointed reduction forceps will be used gently to reduce the fracture from palmar to dorsal and from proximal to distal. The application of excessive force can result in fragmentation.

Note
Anatomic reduction is important to prevent chronic instability or posttraumatic degenerative joint disease.

3 Fixation top

Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Screw size

The maximal permitted diameter of the screw head is one third of the diameter of the avulsed fragment.
Screw length needs to be adequate for the screw to penetrate and purchase in the opposite cortex.


Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Visualize the joint

Laterally deviate the phalanx in the opposite direction to gain maximal visualization of the joint (open book).
Evaluate the fracture geometry and determine the ideal position of the gliding hole (perpendicular to the fracture plane, and through the center of the fragment).


Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Drilling: Inside-Out hole

Keeping the finger laterally deviated, drill an inside-out gliding hole through the center of the avulsed fragment.
The advantage of this technique is that it allows perfect positioning of the drill hole (perpendicular to the fracture plane and through the center of the fragment).

Note: Preserve vascularization
The risk of this procedure is the additional dissection and potential resulting devascularization, which can jeopardize fracture healing.


Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Reduction of fragment

The avulsed fragment is now reduced anatomically, and held with a pointed reduction forceps, as previously discussed.


Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Drill far fragment

Insert a 1.3 (1.0) mm drill sleeve into the gliding hole.
Now use a 1.0 (0.8) mm drill bit to drill a thread hole into the opposite fragment, penetrating the far (trans) cortex.


Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Alternative drilling

Keeping the fragment reduced with a small reduction forceps, make a gliding hole using a 1.3 mm drill bit for a 1.3 mm screw, or a 1.0 mm drill bit for a 1.0 mm screw, from outside-in.
Insert a 1.3 (1.0) mm drill sleeve into the gliding hole.
Use a 1.0 (0.8) mm drill bit to drill a thread hole in the opposite fragment, just through the far (trans) cortex.


Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Screw insertion

Insert the lag screw and tighten it. The screw should penetrate the opposite cortex.


Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Check under image intensification. Reduction must be anatomical.


Avulsion fracture of proximal phalanx MCP joint – Screw fixation enlarge

Pearl: Wire loop

In cases where the avulsed fragment is so small that the screw length is not sufficient to reach the far cortex, the fixation can be strengthened by adding a figure-of-eight wire loop, passing beneath the ligament insertion into the fragment.
The wire loop is also a good choice if the achieved compression is not sufficient for other reasons.

v1.0 2008-11-08