Question

A 17-year-old boy came to the emergency room after a road traffic accident with multiple
injuries. Upon initial check-up, he has multiple lacerations on his chest, head and right
forearm. On examination, he is unable to extend his right arm as well as forearm. The X-ray of
right arm shows fracture of mid shaft of humerus.
A. Which nerve is mostly likely damaged due to fracture of humerus? (2)
B. Enumerate the muscles in forearm supplied by the involved nerve. (4)
C. Write down the origin, course and termination along with branches of the involved nerve. (4)

Answer 1

A) Radial nerve is mostly likely damaged due to fracture of humerus. Nerve injury occurs in approximately 18% of closed mid-shaft or distal shaft humerus fractures. In closed fractures, radial nerve injury is most commonly an incomplete neuropraxia rather than a complete laceration of the nerve. In open humerus fractures, the incidence of radial nerve laceration is much higher at 60%.

B) The radial nerve originates in the brachial plexus and has nerve roots from C5 to T1. It crosses through the spiral groove on the posterior side of the humerus shaft. The spiral groove is located about 14 cm proximal to the lateral epicondyle and 20 cm proximal to the medial epicondyle. The radial nerve is most likely to be damaged in humerus fractures that have a lateral displacement of the distal fracture segment, as the nerve is tethered to the bone and cannot withstand the forces applied to it as a result of the displacement. On physical exam, patients with a radial nerve injury may have wrist drop (loss or weakness of wrist extensors), loss or weakness of finger extension, and decreased or absent sensation to the posterior forearm, digits 1 to 3, and the radial half of the fourth digit. Up to 90% of patients with a closed humeral fracture with radial nerve injury will have a resolution of neuropraxia within three to four months following the injury.Of note, radial nerve paralysis is rare in children with humeral fractures, though neuropraxia can still occur, also with a resolution of symptoms in three to four months.

C) Radial nerve injury occurs in approximately 18% of closed mid-shaft or distal shaft humerus fractures. In closed fractures, radial nerve injury is most commonly an incomplete neuropraxia rather than a complete laceration of the nerve. In open humerus fractures, the incidence of radial nerve laceration is much higher at 60%. It crosses through the spiral groove on the posterior side of the humerus shaft. The spiral groove is located about 14 cm proximal to the lateral epicondyle and 20 cm proximal to the medial epicondyle. The radial nerve is most likely to be damaged in humerus fractures that have a lateral displacement of the distal fracture segment, as the nerve is tethered to the bone and cannot withstand the forces applied to it as a result of the displacement.