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Difficulty: Very hardOrthopedic Surgery

Match each specific orthopedic injury with the most likely corresponding acute neurovascular physical exam finding.

  • Extension-type supracondylar humerus fracture with posteromedial displacement of the distal fragmentWeakness in wrist extension and sensory loss over the dorsal first web space
  • Extension-type supracondylar humerus fracture with posterolateral displacement of the distal fragmentInability to flex the distal interphalangeal joint of the index finger and interphalangeal joint of the thumb
  • Fracture of the medial epicondyle of the humerusWeakness in finger abduction and sensory loss over the volar hypothenar eminence
  • Traumatic posterior dislocation of the hip jointWeakness in ankle dorsiflexion and foot eversion with intact foot inversion

Answer

Posteromedial supracondylar displacement matches with radial nerve injury; posterolateral supracondylar displacement matches with median (anterior interosseous) nerve injury; medial epicondyle fracture matches with ulnar nerve injury; and posterior hip dislocation matches with sciatic (peroneal division) nerve injury.
Each specific orthopedic injury places a unique neurovascular structure at risk due to adjacent anatomy. Posteromedial distal displacement in supracondylar fractures drives the proximal fragment anterolaterally into the radial nerve. Posterolateral distal displacement drives the proximal fragment anteromedially into the median nerve. Medial epicondyle fractures directly impact the ulnar nerve. Posterior hip dislocations commonly stretch the sciatic nerve, with the tethered peroneal division suffering the brunt of the injury, causing foot drop but sparing tibial nerve functions.

Step-by-Step Solution

1
Analyze the direction of displacement in extension-type supracondylar humerus fractures.
Posteromedial displacement of the distal fragment forces the proximal fragment anterolaterally (affecting the radial nerve). Posterolateral displacement forces the proximal fragment anteromedially (affecting the median nerve and brachial artery).
Understanding the precise anatomical relationship of the displaced proximal fracture fragment to surrounding neurovascular structures is crucial for predicting specific nerve injuries.
2
Identify the nerve at risk in medial epicondyle fractures.
The ulnar nerve is identified as the structure at risk due to its location in the cubital tunnel.
Direct trauma or fracture displacement at the medial epicondyle directly impacts the ulnar nerve, causing weakness in intrinsic hand muscles and sensory loss over the hypothenar eminence.
3
Determine the neurologic consequence of a posterior hip dislocation.
The sciatic nerve is at risk, particularly its common peroneal division, leading to weakness in dorsiflexion and eversion while foot inversion remains intact.
The common peroneal division of the sciatic nerve is anatomically more fixed, making it disproportionately vulnerable to traction in posterior hip dislocations compared to the tibial division.

Key Concept

Neurovascular complications of specific orthopedic fractures and dislocations based on precise anatomical relationships and displacement directions.
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Orthopedic Surgery

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