Wrist drop

Wrist drop
Wrist drop
Other names	Radial nerve palsy, musculospiral nerve palsy, crutch paralysis, Saturday night palsy, honeymoon palsy
	The suprascapular, axillary, and radial nerves.
Specialty	Neurology

Last updated June 20, 2022

Wrist drop is a medical condition in which the wrist and the fingers cannot extend at the metacarpophalangeal joints. The wrist remains partially flexed due to an opposing action of flexor muscles of the forearm. As a result, the extensor muscles in the posterior compartment remain paralyzed.

Forearm anatomy

The forearm is the part of the body that extends from the elbow to the wrist and is not to be confused with the arm, which extends from the shoulder to the elbow. The extensor muscles in the forearm are the extensor carpi ulnaris, extensor digiti minimi, extensor digitorum, extensor indicis, extensor carpi radialis brevis, and extensor carpi radialis longus. These extensor muscles are supplied by the posterior interosseous nerve, a branch of the radial nerve. Other muscles in the forearm that are innervated by this nerve are the supinator, extensor pollicis brevis, extensor pollicis longus and abductor pollicis longus. All of these muscles are situated in the posterior half of the forearm (posterior is when it is in its standard anatomical position). Also, the brachioradialis, anconeus, triceps brachii and extensor carpi radialis longus are all innervated by muscular branches of the radial nerve in the arm.

Causes

Wrist extension is achieved by muscles in the forearm contracting, pulling on tendons that attach distal to (beyond) the wrist. If the tendons, muscles, or nerves supplying these muscles are damaged or otherwise not working as they should be, wrist drop may occur.

The following situations may result in wrist drop:

Stab wounds to the chest at or below the clavicle–The radial nerve is the terminal branch of the posterior cord of the brachial plexus. A stab wound may damage the posterior cord and result in neurological deficits, including an inability to abduct the shoulder beyond the first 15 degrees, an inability to extend the forearm, reduced ability to supinate the hand, reduced ability to abduct the thumb and sensory loss to the posterior surface of the arm and hand.
Broken humerus–The radial nerve can be damaged if the humerus (the bone of the arm) is broken because it runs through the radial groove on the lateral border of this bone along with the deep brachial artery.
Lead poisoning–Wrist drop is associated with lead poisoning due to the effect of lead on the radial nerve.^[1]
Persistent injury–Persistent injury to the nerve is a common cause through either repetitive motion or by applying pressure externally along the route of the radial nerve as in the prolonged use of crutches, extended leaning on the elbows, or regular upper body rope suspension. The colloquial terms for radial nerve palsy are derived from this cause.
Correcting dislocated shoulders–Radial nerve palsy can result from the now discredited practice of correcting a dislocated shoulder by putting a foot in the person's armpit and pulling on the arm in attempts to slide the humerus back into the glenoid cavity of the scapula.^[2]
Neuropathy in the hands and/or arms in patients with rheumatoid arthritis may in rare cases cause wrist drop. "When a joint swells, it can pinch the nerves of sensation that pass next to it. If the swelling irritates the nerve, either because of the inflammation or simply because of pressure, the nerve can send sensations of pain, numbness, and/or tingling to the brain. This is called nerve entrapment. Nerve entrapment most frequently occurs at the wrist (carpal tunnel syndrome) and elbow (ulnar nerve entrapment). A rare form of nerve disease in patients with rheumatoid arthritis that causes numbness and/or tingling is neuropathy. Neuropathy is nerve damage that in people with rheumatoid arthritis can result from inflammation of blood vessels (vasculitis)."^[3]

Types

Types of wrist drop are distinguished by the nerves affected:

Weakness of brachioradialis, wrist extension and finger flexion = radial nerve lesion
Weakness of finger extension and radial deviation of the wrist on extension = posterior interosseous nerve lesion
Weakness of triceps, finger extensors and flexors = c7,8 lesion
General weakness of upper limb marked in deltoid, triceps, wrist extension and finger extension = corticospinal lesion

Diagnosis

The workup for wrist drop frequently includes nerve conduction velocity studies to isolate and confirm the radial nerve as the source of the problem. Other screening tests include the inability to extend the thumb into a "hitchhiker's sign".^[4] Plain films can help identify bone spurs and fractures that may have injured the nerve. Sometimes MRI imaging is required to differentiate subtle causes.

Treatment

Initial treatment includes splinting of the wrist for support, along with osteopathic medicine, physiotherapy and occupational therapy. In some cases, surgical removal of bone spurs or other anatomical defects that may be impinging on the nerve might be warranted. If the injury was the result of pressure from prolonged use of improperly fitted crutches or other similar mechanisms of injury, then the symptoms of wrist drop will most likely resolve spontaneously within 8–12 weeks.^[5]

Related Research Articles

The ulna is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. It runs parallel to the radius, the other long bone in the forearm. The ulna is usually slightly longer than the radius, but the radius is thicker. Therefore, the radius is considered to be the larger of the two.

The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way of the brachioradialis tendon, and to the lateral supracondylar ridge of the humerus.

The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.

The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus.

In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; (2) the wrist joint or radiocarpal joint, the joint between the radius and the carpus and; (3) the anatomical region surrounding the carpus including the distal parts of the bones of the forearm and the proximal parts of the metacarpus or five metacarpal bones and the series of joints between these bones, thus referred to as wrist joints. This region also includes the carpal tunnel, the anatomical snuff box, bracelet lines, the flexor retinaculum, and the extensor retinaculum.

The extensor carpi radialis longus is one of the five main muscles that control movements at the wrist. This muscle is quite long, starting on the lateral side of the humerus, and attaching to the base of the second metacarpal bone.

In human anatomy, extensor carpi radialis brevis is a muscle in the forearm that acts to extend and abduct the wrist. It is shorter and thicker than its namesake extensor carpi radialis longus which can be found above the proximal end of the extensor carpi radialis brevis.

In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is common. This nerve is directly connected to the little finger, and the adjacent half of the ring finger, innervating the palmar aspect of these fingers, including both front and back of the tips, perhaps as far back as the fingernail beds.

The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the arm, forearm and hand, and is primarily used for climbing, lifting and manipulating objects.

In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together with this muscle.

The posterior interosseous nerve is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared to the deep branch of the radial nerve. The nerve fibers originate from cervical segments C7 and C8 in the spinal column.

The fascial compartments of arm refers to the specific anatomical term of the compartments within the upper segment of the upper limb of the body. The upper limb is divided into two segments, the arm and the forearm. Each of these segments is further divided into two compartments which are formed by deep fascia – tough connective tissue septa (walls). Each compartment encloses specific muscles and nerves.

The posterior compartment of the forearm contains twelve muscles which are chiefly responsible for Flexion of the wrist and digits, and supination of the forearm. It is separated from the anterior compartment by the interosseous membrane between the radius and ulna.

The cervical spinal nerve 8 (C8) is a spinal nerve of the cervical segment.

The elbow is the region between the arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa, and the lateral and the medial epicondyles of the humerus. The elbow joint is a hinge joint between the arm and the forearm; more specifically between the humerus in the upper arm and the radius and ulna in the forearm which allows the forearm and hand to be moved towards and away from the body. The term elbow is specifically used for humans and other primates, and in other vertebrates forelimb plus joint is used.

Injuries to the arm, forearm or wrist area can lead to various nerve disorders. One such disorder is median nerve palsy. The median nerve controls the majority of the muscles in the forearm. It controls abduction of the thumb, flexion of hand at wrist, flexion of digital phalanx of the fingers, is the sensory nerve for the first three fingers, etc. Because of this major role of the median nerve, it is also called the eye of the hand. If the median nerve is damaged, the ability to abduct and oppose the thumb may be lost due to paralysis of the thenar muscles. Various other symptoms can occur which may be repaired through surgery and tendon transfers. Tendon transfers have been very successful in restoring motor function and improving functional outcomes in patients with median nerve palsy.

Upper-limb surgery in tetraplegia includes a number of surgical interventions that can help improve the quality of life of a patient with tetraplegia.

The extrinsic extensor muscles of the hand are located in the back of the forearm and have long tendons connecting them to bones in the hand, where they exert their action. Extrinsic denotes their location outside the hand. Extensor denotes their action which is to extend, or open flat, joints in the hand. They include the extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor digitorum (ED), extensor digiti minimi (EDM), extensor carpi ulnaris (ECU), abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor pollicis longus (EPL), and extensor indicis (EI).

Radial nerve dysfunction Medical condition

Radial nerve dysfunction is a problem associated with the radial nerve resulting from injury consisting of acute trauma to the radial nerve. The damage has sensory consequences, as it interferes with the radial nerve's innervation of the skin of the posterior forearm, lateral three digits, and the dorsal surface of the lateral side of the palm. The damage also has motor consequences, as it interferes with the radial nerve's innervation of the muscles associated with the extension at the elbow, wrist, and fingers, as well the supination of the forearm. This type of injury can be difficult to localize, but relatively common, as many ordinary occurrences can lead to the injury and resulting mononeuropathy. One out of every ten patients with radial nerve dysfunction do so because of a fractured humerus.

References

↑ Dedeken P, Louw V, Vandooren AK, Verstegen G, Goossens W, Dubois B (June 2006). "Plumbism or lead intoxication mimicking an abdominal tumor". J Gen Intern Med. 21 (6): C1–3. doi:10.1111/j.1525-1497.2006.00328.x. PMC 1924641 . PMID 16808730.
↑ Saladin, Kenneth (2012). Anatomy and Physiology: The Unity of Form and Function (6th ed.). New York: McGraw-Hill. p. 497. ISBN 9780073378251.
↑ Klippel JH, Crofford LJ, Stone JH, White PH (2008). Primer on the Rheumatic Diseases. New York: Springer. ISBN 9780387685663.
↑ Ebnezar, John (2010). Textbook of Orthopedics: With Clinical Examination Methods in Orthopedics. Jaypee Brothers Medical Publishers (P) Ltd. p. 343. ISBN 9351521222.
↑ Raikin S, Froimson MI (1997). "Bilateral brachial plexus compressive neuropathy (crutch palsy)". J Orthop Trauma. 11 (2): 136–38. PMID 9057152.

External links

clinicalconsiderations at The Anatomy Lesson by Wesley Norman (Georgetown University)
William C. Shiel Jr., MD, FACP, FACR. "Rheumatoid Arthritis: 17 Warning Signs of Serious Complications".{{cite web}}: CS1 maint: multiple names: authors list (link)

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[pmid16808730-1] Dedeken P, Louw V, Vandooren AK, Verstegen G, Goossens W, Dubois B (June 2006). "Plumbism or lead intoxication mimicking an abdominal tumor". J Gen Intern Med. 21 (6): C1–3. doi:10.1111/j.1525-1497.2006.00328.x. PMC 1924641 . PMID 16808730.

[2] Saladin, Kenneth (2012). Anatomy and Physiology: The Unity of Form and Function (6th ed.). New York: McGraw-Hill. p. 497. ISBN 9780073378251.

[3] Klippel JH, Crofford LJ, Stone JH, White PH (2008). Primer on the Rheumatic Diseases. New York: Springer. ISBN 9780387685663.

[4] Ebnezar, John (2010). Textbook of Orthopedics: With Clinical Examination Methods in Orthopedics. Jaypee Brothers Medical Publishers (P) Ltd. p. 343. ISBN 9351521222.

[pmid9057152-5] Raikin S, Froimson MI (1997). "Bilateral brachial plexus compressive neuropathy (crutch palsy)". J Orthop Trauma. 11 (2): 136–38. PMID 9057152.

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