Anatomy clinical correlates: Wrist and hand

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A 42-year-old man is brought to the emergency department after sustaining a hand injury. The patient was jogging when he tripped and fell onto an area of concrete with scattered glass shards. He sustained lacerations to the left hand. He is otherwise healthy and does not take medications. Temperature is 37.0°C (98.6°F), blood pressure is 115/78 mmHg, and pulse is 103/min. Visual inspection of the left hand demonstrates a 4 cm laceration extending from the base of the hypothenar eminence to the thenar eminence. Which of the following should be evaluated to assess for underlying nerve injury?  

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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.

Sources

  1. "Raj's Practical Management of Pain" Elsevier Health Sciences (2008)
  2. "Synergy" Oxford University Press (2008)
  3. "Human Anatomy and Physiology" Pearson Education (2003)
  4. "Human Anatomy and Physiology" Pearson Education (2003)
  5. "Stabilization and treatment of Colles’ fractures in elderly patients" Clinical Interventions in Aging (2010)
  6. "Scaphoid Fracture - Overview and Conservative Treatment" Hand Surgery (2015)
  7. "The Wrist: Clinical Anatomy and Physical Examination—an Update" Primary Care: Clinics in Office Practice (2005)
  8. "Diagnosing and managing carpal tunnel syndrome in primary care" British Journal of General Practice (2014)
  9. "Clinical associations of Dupuytren's disease" Postgraduate Medical Journal (2005)
  10. "Stabilization and treatment of Colles’ fractures in elderly patients" Clin Interv Aging (2010)
  11. "Carpal tunnel syndrome in pregnancy" Orthop Clin North Am (2012)
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