Anatomy clinical correlates: Wrist and hand

In everyday life, we rely on our hands for a variety of reasons, from vigorously typing out notes while watching an Osmosis video to playing musical instruments or participating in sports.

Unfortunately, since we use them so much, the hands are quite prone to injury.

Alright, let's start by looking at distal forearm fractures.

There’s two kinds: Colles fracture, which are a direct result of falling on an extended wrist, and Smith fracture, which results from falling on a flexed wrist, or a direct blow to the posterior forearm.

With Colles fractures, the displaced radial fragment moves posteriorly, or dorsally, and the ulnar styloid process can also become fractured.

Clinically, when the distal radial segment moves dorsally this is called a “dinner fork deformity” because when viewed laterally, the hand and wrist are slightly curved anteriorly making it look like a fork.

With Smith fractures, on the other hand, the displaced distal radial fragment moves anteriorly, or ventrally, which clinically translates as a “garden spade” deformity.

Next, let’s look at carpal bone fractures, of which the most common are scaphoid fractures.

Scaphoid fractures occur as a result of falling on the lateral side of an outstretched hand in abduction.

Clinically, this results in pain and tenderness on the lateral side of the wrist and hand, in a location called the anatomical snuffbox, which is where you can palpate the scaphoid bone between the tendons of extensor pollicis longus on the medial side and extensor pollicis brevis and abductor pollicis longus on the lateral side.

The big problem with these fractures is that because the blood vessels supply the distal part of the scaphoid first then come back and supply the proximal part, a fracture in the middle of this bone disrupts the blood supply.

This can cause avascular necrosis and non union of the proximal fragment of the scaphoid, which is basically when the bone dies off because of lack of blood, and degenerative wrist joint disease.

Initial X-rays often miss scaphoid fractures at first, so when there is tenderness on palpation of the anatomical snuffbox in a patient who fell on an outstretched hand, it’s important to still treat it as a fracture to avoid this complication.