Radial Nerve Palsy. The radial nerve is the most commonly damaged nerve after fractures of the distal shaft of the humerus. Normally protected in the spiral groove of the humeral shaft, the nerve is susceptible to stretch, direct injury by a fracture fragment, or entrapment in the fracture site itself. Aggressive manipulation of the fracture during closed reduction may also result in nerve entrapment. Although wrist drop is the consequence of radial nerve injury, this is most often a neurapraxia, with nearly 100% recovery in low-energy trauma patients and over 33% recovery in high-energy trauma patients despite the method of treatment. Recovery of motor strength may take multiple months to occur, but radial nerve palsy in itself is usually not an indication for surgery.
Sciatic Nerve Palsy. Nerves and vessels at or near joints are particularly vulnerable to injury. The neurovascular structures are more securely tethered to the soft tissues around joints than elsewhere and are less likely to escape injury when significant joint displacement occurs. For example, the sciatic nerve is at risk in posterior dislocation of the hip, with injury occurring at a rate of approximately 13% in simple dislocations. Generally, the nerve is simply stretched or contused by direct impingement of the femoral head. The peroneal branch is most commonly affected, the sequela of which is foot drop. Immediate reduction of the dislocation relieves pressure on the nerve, and about two thirds of patients are likely to recover partial to full motor and sensory deficits. A possible indication for surgical exploration might be a patient in whom no neurologic deficits were present until after manipulation and reduction of the joint.
Neurovascular Injury About the Elbow. A musculoskeletal injury that is frequently associated with neurovascular injury is the supracondylar fracture of the humerus. It is most common in children between 3 and 10 years of age and usually results from a fall on the outstretched hand. In the most common type of fracture, hyperextension injury, the distal fracture fragment is displaced posteriorly, which can result in the critical neurovascular structures anterior to the elbow becoming tethered on the anterior edge of the fractured humeral shaft. The median nerve and the brachial artery are both particularly susceptible to direct injury from the displaced fracture fragment and can be lacerated or entrapped in the fracture site at the time of injury or during the closed reduction. A common neurologic sequela is damage to a branch of the median nerve, the anterior interosseous nerve, which results in the inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. The anterior interosseous nerve is readily assessed by asking the patient to make an “OK sign” with the thumb and index finger. Distal neurovascular function must be assessed critically both before and after any treatment, and manipulative reduction must be careful and gentle.
Compartment Syndrome. Direct damage to an artery or severe swelling in a muscle compartment can lead to development of compartment syndrome. This serious outcome is common after any fracture in which bleeding and swelling are extreme. Compartment syndromes can occur with open as well as with closed fractures and may also be caused by a circular cast. Failure to identify compartment syndrome early may lead to permanent loss of limb function.
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