Department of Neurosurgery, University of Wisconsin, Madison, WI, USA
9.1 Case Presentation
A 19-year-old male suffered a gunshot wound to the right arm a month ago. He comes with a wrist drop . Examination of the right arm: brachioradialis 0, supination 4 and weaker with elbow extension, wrist extension 0, MPJ extension 0, IPJ extension of digits 2–5 is normal, thumb extension 0. The remaining muscles are normal. There is sensory loss over the dorsum of the first web space on the right.
What is the diagnosis?
What tests are needed?
What is the plan of treatment?
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Right radial n injury distal to the triceps . Supination with elbow flexion is mostly achieved by the biceps brachii ; this contribution can be minimized by elbow extension. In Fig. 9.1, the bullet entry (A) and exit (B) points are shown by the arrows and the radial n projection is shown in yellow. Note the right wrist drop with triceps sparing (C). Most of triceps branches arise in the axilla and are usually spared with this level of injury. The sensory loss (hatch marks in D) corresponds to the radial n. Figure 9.2. Shows that in the setting of a wrist drop, it is hard to abduct the fingers (A), the wrist and fingers have to be passively extended to neutral in order to test the IO (by examining the hand on a flat surface) (B), otherwise this can be mistaken for combined radial and ulnar n injuries.