During pelvic surgery, upper extremity neuropathies result from stretch or compression injury to the brachial plexus or its nerve branches. Although complete resolution of neuropathic symptoms is seen in most patients, perioperative neuropathies may lead to prolonged or permanent impairment and can have a significant negative impact on a patient's quality of life. The objectives of this video are to review proposed mechanisms of nerve injury, demonstrate the anatomy of the brachial plexus, illustrate patient positions that may increase the risk of nerve injury, describe common presenting symptoms, and discuss strategies to minimize nerve injury. Most nerve injury classification systems attempt to correlate the degree of injury with symptoms, pathology, and prognosis. Set-in classification of injury includes from least to most severe, neuropraxia, axonotmesis, and neurotmesis. With neuropraxia, compression of a nerve can lead to ischemia and demyelination. With this type of injury, the axon and connective tissue are intact and recovery takes place within days to weeks. Prolonged compression or nerve stretching beyond a certain point leads to axonal disruption. In this type of injury, termed axonotmesis, the connective tissue remains intact. Recovery takes months to years as axonal regrowth occurs at one to two millimeters per day. In the most severe type of injury, termed neurotmesis, both the axon and connective tissue are affected. The nerves that supply the upper extremity arise from the brachial plexus. This plexus is formed by the union of the ventral rami of the lower four cervical nerves and the greater part of the first thoracic ventral ramus. These ventral rami form the roots of the plexus. Although variations are common, the most common arrangement of the brachial plexus is as follows. The five roots of the plexus merge to form three trunks, superior, middle, and inferior, which lie in the posterior triangle of the neck in the angle between the clavicle and lower posterior border of the sternocleidomastoid muscles. Each trunk then divides into an anterior and a posterior division just above or behind the clavicle. The cords, named according to their relationship to the axillary artery, include the lateral, medial, and posterior cords. The ulnar, radial, and median nerves are the main terminal branches of the brachial plexus that supply the upper extremity. The most common upper extremity nerve injury associated with surgical positioning is ulnar neuropathy. The ulnar nerve is the main terminal branch of the medial cord formed primarily by C8 and T1 spinal nerve root fibers. In the arm, the nerve descends in a superficial position along the medial head of the triceps and then traverses a cubital tunnel to enter the forearm. In the forearm, it passes between the two heads of the flexor carpe ulnaris muscle. The ulnar nerve provides no innervation in the arm. It provides motor innervation to some flexor muscles in the forearm and to muscles in the hand controlling flexion, abduction, and adduction of the fingers. The ulnar nerve is especially vulnerable to compression injury within the ulnar groove, which is found between the medial epicondyle of the humerus and the olecranon at the elbow. In the ulnar groove, the nerve is only covered by skin and fascia, and injury may occur with prolonged compression of the nerve against a fixed surface. With the arm abducted and pronated, the nerve is positioned inferiorly within the ulnar groove and is potentially exposed to external pressure or compression against the arm board. When the arm is abducted and supinated, the weight of the upper extremity rests primarily on the olecranon process. With the arm supinated, the ulnar nerve is positioned medially and may be protected from compression against the arm board. When the arms are tucked or positioned adjacent to the body, the ulnar nerve may be compressed against the rails of the table or the hard surfaces of the arm board if the upper extremities accidentally slip off their proper position. Clinical manifestations of ulnar nerve injury include difficulty making a fist, weakened abduction and adduction of the fingers, a claw hand, and or sensory deficits on the medial half of the hand and medial two fingers. The median nerve is formed by the lateral medial cords of the brachial plexus and thus receives contributions from C6 to C8 and T1 spinal nerve fibers. The median nerve courses down the arm adjacent the brachial artery and enters the forearm through the cubital fossa. Similar to the ulnar nerve, the median nerve provides no innervation in the arm. The nerve innervates most of the muscles of the anterior forearm and the intrinsic muscles of the hand acting on the thumb and lateral two fingers. The median nerve may be stretched with prolonged hyperextension of the elbow beyond what was comfortable during the preoperative exam. Intraoperatively, this may happen if the arm slips off the bed or arm board. The median nerve may also be injured while obtaining intravenous access in the cubital fossa. Clinical manifestations of median nerve injury include weak inflection of the wrist and fingers, weakness in all actions of the thumb, inability to make a standard O with the thumb and forefinger, and or sensory deficits over the thumb and lateral two and a half fingers and across the lateral half of the palm of the hand. The radial nerve is the largest branch of the posterior cord formed by C5 to T1 fibers. The radial nerve passes laterally from the start of the brachial artery, winds around the medial side of the humerus, and enters the substance of the triceps muscle. It then spirals around the lateral aspect of the humerus at the midarm in the groove separating the origins of the medial and lateral heads of the triceps. The radial nerve supplies the muscles in the posterior compartment of the arm and forearm, which are mostly extensors, as well as the skin overlying these regions. The nerve is susceptible to compression injury as it spirals around the lateral aspect of the humerus at the midarm. Intraoperatively, injury to this nerve may occur with prolonged compression from a blood pressure cuff or a tourniquet. Clinical manifestations of radial nerve injury include weakness when abducting the thumb, inability to straighten out the fingers, wrist drop, and or sensory deficits along the dorsolateral aspect of the hand. Intraoperatively, brachial plexus injury may occur with prolonged abduction of the arm beyond 90 degrees from the body. This may lead to overstretching of the angle of the humeral head and compression of the axillary neurovascular bundle. The use of shoulder support devices may also lead to plexus injury when a patient is positioned in steep Trendelenburg for prolonged periods of time. In this position, downward migration of the body may occur and depression of the shoulder under general anesthesia may lead to stretching of the brachial plexus. Shoulder braces should be placed over the acromioclavicular joint and not too close to the neck as the latter position may lead to direct compression of the brachial plexus. Lateral flexion of the neck may also lead to stretch injury. Clinical manifestations of brachial plexus injury are variable and range from sensory impairment, such as numbness and tingling, to motor involvement with difficulty or inability to move portions of the upper extremity. Strategies to reduce upper extremity neuropathies during surgery include limiting the degree of arm abduction to 90 degrees or less in the supine patient, placing shoulder braces over the acromioclavicular joint and not too close to the neck when these devices are used. To minimize the risk of ulnar neuropathy with a supine patient with arms on an armboard, the arm should preferably be supinated or neutral to decrease pressure on the ulnar groove. Alternatively, the armboard should be padded. With a supine patient with arms tucked at the side, the arm should preferably be supinated with forearms and hands in the neutral position. To minimize the risk of median and radial neuropathy, one should avoid extension of the elbow beyond the range that is comfortable during preoperative assessment and prolong pressure on the radial nerve at the spiral groove of the humerus. In addition, periodic assessment of patient position should be done to ensure maintenance of desired position. In conclusion, although upper extremity neuropathies can occur despite careful positioning and padding, understanding the brachial plexus anatomy and patient positions that may increase the risk for neuropathy should assist the entire surgical team in supporting safety measures.

upper extremity neuropathies

pelvic surgery

brachial plexus

perioperative neuropathies

nerve injury