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Radial Nerve Palsy following Frx of the Humerus

see also (Radial Nerve Discussion; Tendon Transfers for Radial Nerve Palsy)

Discussion

  • up to 18% of humeral shaft frx have an associated radial nerve palsy;
  • it occurs most commonly with middle third humeral fractures & in Holstein Lewis fractures;
  • types of nerve lesions;
    • laceration of nerve, most common in spiral frx of the distal 1/3 of humerus;
    • entrapment of radial nerve at fracture site by bone fragments;
    • most often, palsy is a result of neuropraxia & are incomplete;
      • w/ neuropraxia,  nerve axons will regenerate 1 mm a day;

Palsy Associatted w/ Distal Third Frx

  • radial nerve may be injured by fractures is at junction of mid and distal thirds of humeral shaft, esp if there is lateral displacement of distal fragment;
    • at this location the radial nerve emerges from spiral groove & is tethered as it pierces the intermuscular septum;
    • here, it cannot yeild to lateral displacement of distal fragment and therefore may be subject to neuropraxia;

Prognosis and Treatment

  • w/ closed humeral frx, radial nerve f(x) will return by 3-4 months in 75%-90% of patients;
    • most of these injuries represent a neuropraxia or axonotmensis;
    • if nerve function does not return w/ in 3-4 months, then nerve should be surgically explored;
    • exam should focus on the ECRL which will be among the first muscles to recover (wrist will extend in radial deviation due to weakness of ECU, which is innervated further distally by the PIN);
  • negative prognostic findings:
    • open humeral shaft frxs:
      • incidence of radial nerve laceration is about 60%, hence, radial nerve should be explore primarily;
    • nerve laceration (complete or partial);
    • nerve entrapment in callus;
    • Holstein Lewis fractures;
  • if nerve function disappears w/ fracture reduction, it means that nerve is caught in the fracture;
    • hence, immediate exploration is required, to prevent further nerve damage, and/or entrapment of nerve by fracture callus;

Surgical Treatment

Case Example

  • 13 year old male was casted for a distal humeral fracture but was left in significant varus.  Radial nerve function was present in the ER but was not present one week later in clinic.
  • intraoperatively, it was found that the nerve was tented over the fracture site because of the varus deformity.
      • when the deformity was corrected, traction on the nerve was relieved.

References