Ortho Hors D'oeuvres (Answer):
To review, this is a 78 year-old female 4 days status post fractured left humerus with new onset hand weakness.
Questions and Answers:
1) What nerve bundle is at highest risk of injury in this fracture pattern?
Radial nerve palsies can be seen in approximately 8-15% of closed humeral shaft fractures.
As you can see in the above picture, the radial nerve tracks posterior to the humerus and then loops around the lateral aspect of the shaft and therefore is at high risk for injury in midshaft humeral fractures, especially in the distal third where it loops towards the lateral epicondyle. Ulnar nerve palsies are most often related to elbow trauma (for example, elbow dislocations). Median nerve palsies are often seen in distal radius fractures that result in carpal tunnel impingement. The radial nerve ennervates finger and wrist extension as well as the sensation to the dorsum of the hand; all were compromised in this patient.
2) Could this neurologic injury have been prevented with different initial management?
Humeral neck fractures are commonly managed with a simple sling or cuff-and-collar brace. The weight of the distal humerus and forearm pulls the distal fragment of the fracture into alignment with the humeral head and patients generally have good recovery. The humeral shaft, however, generally heals more slowly than the humeral neck and requires closer external fixation. There is a paucity of data regarding appropriate nonoperative splinting for this fracture and reasonable options include the sling and cuff-and-collar brace. However, the generally agreed-upon splint for humeral shaft fractures is known as a coaptation splint (also known as u-slab or u cast).
3) What are the next steps in management and what is the prognosis of this patient's fracture healing and future nerve function?
In regards to the patient's radial nerve injury, the key is expectant management, not operative repair. Approximately 85-90% of radial nerve palsies associated with closed humeral fractures regain full function over the course of 3 months without intervention. Ability to extend the wrist is the first sign of radial nerve recovery. In open humeral shaft injuries, operative management is recommended, but otherwise this palsy typically heals on its own.
In order to appropriately stabilize her fractured humerus, the patient was placed in a coaptation splint in the emergency department. Her fracture has an overall good prognosis for union: Ninety percent of midshaft humerus fractures heal completely without operative management.
References:
Bishop J, Ring D. Management of Radial Nerve Palsy Associated with Humeral Shaft Fracture: A Decision Analysis Model. J Hand Surg AM. 2009;34(6):991-996.
Liu GH, Zhang CY, Wu HW. Comparison of Initial Nonoperative and Operative Management of Radial Nerve Palsy Associated with Acute Humeral Shaft Fractures. Orthopedics 2012;35(8):702-708
Mukerjee A. U-slab, Hanging Cast or Collar and Cuff in Uncomplicated Shaft of Humerus Fractures in the Elderly. Emerg Med J 2008;25:222.
Persad IJ. U Cast or Functional Bracing Following Fractures of the Shaft of Humerus. Emerg Med J 2007;24(5):361
