radER Case 13.3 (#20)





Case 20 Questions


1. Which is true for metacarpal fractures?


2. Which is true of carpal fractures?


3. The most likely complication of the above injury includes…



1. Correct Answer D. ≤ 10° angulation is tolerated in 2nd and 3rd metacarpal shaft fractures. ≤ 20° angulation as tolerated and third and fourth metacarpal shaft fractures. The 10, 20, 30, 40 rule is used for angulation of metacarpal neck fractures with 10° angulation tolerated in second metacarpal neck fracture, 20° angulation and third metacarpal neck fracture, 30° angulation in fourth metacarpal neck fracture, and 40° angulation in the fifth metacarpal neck fracture. Closed reduction of metacarpal shaft fractures is performed by longitudinal traction with dorsal pressure applied to the fracture site.  The 90-90 closed reduction method is used for metacarpal neck fractures. Metacarpal shaft fractures of the most common fractures of the hand accounting for up to 50% of all hand fractures.  Metacarpal base and neck fractures individually account for up to 30% of fractures involving the hand.

2. Correct Answer C. Up to 30% of scaphoid fractures develop avascular necrosis involving the proximal pole. First row fractures or more, and then second row fractures amongst the carpal group.  Scaphoid fracture is the most common amongst the carpal group at up to 70% of fractures.  The triquetral bone is the second most common fracture at up to 14%.  Isolated fractures of the remaining carpal bones accompany 0.2% to 5% individually. Avascular necrosis becomes more common with more proximal fractures of the scaphoid bone rather than distal.

3. Correct Answer B. Ulnar nerve compression. Fracture of the body or hook of Hamate can cause compression of the ulnar nerve as well as the ulnar artery.  Fracture of the capitate can cause compression of the deep motor branch of the ulnar nerve.  A Smith fracture is known to cause median nerve compression mimicking carpal tunnel syndrome.  Radial nerve compression is most likely due to mid humeral shaft fracture, not carpal bone fractures.

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