Extensor Tendon Injuries, Part II

This series of posts is meant to expand upon and complement a great article that was just published in ALiEM regarding the evaluation and management of extensor tendon injuries.  Rather than give redundant information, in these posts, using images and videos, I hope to bring to life some of the specific concepts discussed by Dr. Baylis, Dr. Ting, and Dr. Haythornthwaite.

hand zones

Zones of the Hand, used for classification of extensor tendon injuries, as originally described by Verdan.

Examination Tricks of the Trade

As discussed in the ALiEM post, a thorough exam is required to determine if an extensor tendon injury may be present. Here’s a few specific exam points discussed in more detail.

Extending a Wound Margin to Improve Visualization

Sometimes extension of the skin wound will be required to better visualize an underlying injury to a tendon. The following video demonstrates the technique of wound margin extension.

The Hyperextension Test

Isolated extensor tendon injuries can be masked by the intrinsic redundancy and interconnections between extensor tendons, as discussed in Part I.  Therefore it’s important to test not only active extension but also assess for any weakness.  Since maximal extension is accomplished by the extensor tendon of a given finger and augmented  by the tendons of adjacent fingers, a patient with an extensor tendon injury in Zone VI may be unable to hyperextend the finger distal to the injury.  A simple way to test this is to have the patient place the hand flat on a table and ask them to lift the fingers off the table.  Compare the relative hyperextension of the finger to adjacent fingers and the fingers of the contralateral hand.

hyperextension test

The hyper-extension test can help to detect minor tendon injuries masked by tendon redundancy.

Elson’s Test for Injury to the Central Slip

Idiosyncracies in examination and management exist with specific areas of the hand.  One important example of this are injuries which occur in Zone III.

Central Slip lac

A small laceration over the extensor surface of the proximal interphalangeal joint. What is the concern with an injury like this?

A previous post describes a unique complication that can occur with extensor tendon injuries at this level, and the exam maneuvers that can help detect this.

Take Home Points

  • Become facile with non-invasive maneuvers such as the hyper-extension test, Elson’s test, and the modified Elson’s test for diagnoses of extensor tendon injuries in specific hand zones.
  • When in doubt, it’s acceptable to extend the wound margins to get a better look inside and rule out injury.