Executive Editor: Joseph Schatzker

Authors: Richard Buckley, Andrew Sands

Talus - Lateral process

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Glossary

1 Diagnosis top

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Mechanism of the injury

This fracture is often confused with an ankle sprain. The mechanism of injury is forced eversion with a loaded hindfoot. This is often called the “snowboarder’s fracture”.


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Imaging

A plain x-ray may be diagnostic, but coronal CT scans are often necessary for a complete definition of the injury.

Case by courtesy of Dr. Steven Steinlauf, Florida, USA.

2 Surgical indications top

Fractures of the lateral process of the talus always involve the subtalar joint and depending on the size of the fragment may also involve the articulation between the lateral surface of the talus and the lateral malleolus. Because this is an intraarticular fracture, if displaced, anatomic reduction and stable fixation has to be restored to prevent the development of posttraumatic arthritis. If the fracture is comminuted and reduction and fixation is not possible, then one should consider resection. Similarly, if a symptomatic nonunion develops, the fragment should be resected.
If the fracture is completely undisplaced, then immobilization and non-weightbearing is indicated.

3 Reduction top

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Reduction

The direct lateral approach allows visualization of this fragment. Because this fragment is frequently very small, a K-wire may be used as a joystick to help with the reduction which is carried out with the help of an image intensifier.
Because the fragment will not accept more than a single screw, it is best to use a threaded K-wire guide of a corresponding cannulated screw for provisional fixation. This threaded K-wire is then introduced into the middle of the fragment, once reduced, and advanced into the body of the talus. A cannulated lag screw can then be used for fixation.


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Pitfall: non-anatomical reduction

Arthrosis of the subtalar joint may occur if this injury is not accurately reduced and treated.

Case by courtesy of Dr. Steven Steinlauf, Florida, USA.


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Preliminary fixation with eccentric K-wire

A second K-wire should be placed eccentrically, if possible, to provide rotational control of this small fragment of cortical bone. It will be removed when fixation is complete.
If possible, two screws would be optimal, but often not possible.

4 Screw fixation top

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Pearl: rule of thirds

This fracture is often quite small, or multifragmented.
If the piece is one large fragment, then screw fixation is preferred. If the piece is very small then resection may be a better option. K-wires alone may be used but present difficulty (migration) if used alone.

A nice rule to remember is the rule of thirds. If the size of the screw head is more than one third of the size of the fragment, then this small piece may comminute into many pieces. If the size of the screw head is less than a third of the fragment, then successful fixation may be achieved.


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Drilling

With the central K-wire in place, drill the gliding hole with the corresponding drill bit, drilling only the fragment. Then drill the thread hole in the body of the talus.


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Screw insertion

Measure the depth for screw length.
A cannulated partially threaded screw will be used for fixation. Thus depending on the size of the fragment, one would use either the 2.4 mm, or the 3.5 mm screw and the corresponding drill bits.
Careful technique will ensure that the small lateral process does not fragment.


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Second screw for rotational stability

In order to secure rotational stability, it is necessary to insert a second screw, or if not possible, then a K-wire. Screws are preferable to a K-wire. Therefore try to insert a smaller screw to achieve rotational stability.

Use image intensification to make certain that reduction is anatomic and that the fixation has been appropriately inserted to maintain stability and articular congruity.

Case by courtesy of Dr. Steven Steinlauf, Florida, USA.

v1.0 2010-10-14