An ulnar claw, also known as claw hand or spinster's claw, is a deformity or an abnormal attitude of the hand that develops due to

ulnar nerve 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 ...

damage causing paralysis of the lumbricals. A claw hand presents with a hyperextension at the

metacarpophalangeal joint The metacarpophalangeal joints (MCP) are situated between the metacarpal bones and the proximal phalanges of the fingers. These joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cav ...

s and flexion at the proximal and distal interphalangeal joints of the 4th and 5th fingers. The patients with this condition can make a full fist but when they extend their fingers, the hand posture is referred to as claw hand. The ring- and little finger can usually not fully extend at the proximal interphalangeal joint (PIP). This can be commonly confused with the " hand of benediction or pope's blessing", which is caused by proximal (at elbow level) median nerve damage.

Presentation

Patients exhibiting an ulnar claw are also very frequently unable to spread (abduct) or pull together (adduct) their fingers against resistance. This occurs because the ulnar nerve also innervates the palmar and

dorsal interossei of the hand In human anatomy, the dorsal interossei (DI) are four muscles in the back of the hand that act to abduct (spread) the index, middle, and ring fingers away from hand's midline (ray of middle finger) and assist in flexion at the metacarpophalangea ...

. Patients with this deficit will become increasingly easy to identify over time as the paralysed first dorsal interosseous muscle atrophies, leaving a prominent hollowing between the thumb and forefinger.

Ulnar nerve symptoms

The

runs from the shoulder to the hand, and damage to it results in the Ulnar claw. It is linked to palsy, which is a result of

peripheral neuropathy Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or or ...

. There is a range of ways that damage to the nerve can occur. Leaning on the elbow can lead to long-term wear and tear due to the prolonged pressure of the weight of the upper body. Symptoms resulting from leaning on the nerve can include numbness and tingling fingers.

Causes

Common occupations such as

cyclist Cycling, also, when on a two-wheeled bicycle, called bicycling or biking, is the use of cycles for transport, recreation, exercise or sport. People engaged in cycling are referred to as "cyclists", "bicyclists", or "bikers". Apart from two ...

, motorcyclist, and desk jobs prolong movement and elbow leaning. These activities involve

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

to the palms, which leads to cumulative damage to the nerve. When using a pizza cutter or similar hand tools which require downward pressure during use, applying upper

body weight Human body weight is a person's mass or weight. Strictly speaking, body weight is the measurement of weight without items located on the person. Practically though, body weight may be measured with clothes on, but without shoes or heavy accessor ...

to push down on the tool over time can cause damage to the nerve.

Pathogenesis

An ulnar claw may follow an ulnar nerve

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classifi ...

which results in the partial or complete denervation of the ulnar (medial) two

lumbricals of the hand The lumbricals are intrinsic muscles of the hand that flex the metacarpophalangeal joints, and extend the interphalangeal joints. p. 97 The lumbrical muscles of the foot also have a similar action, though they are of less clinical concern. S ...

. Since the ulnar nerve also innervates the 3rd and 4th lumbricals, which flex the MCP joints (aka the knuckles), their denervation causes these joints to become extended by the now unopposed action of the long finger extensors (namely the

extensor digitorum The extensor digitorum muscle (also known as extensor digitorum communis) is a muscle of the posterior forearm present in humans and other animals. It extends the medial four digits of the hand. Extensor digitorum is innervated by the posterior int ...

and the

extensor digiti minimi The extensor digiti minimi (extensor digiti quinti proprius) is a slender muscle of the forearm, placed on the ulnar side of the extensor digitorum communis, with which it is generally connected. It arises from the common extensor tendon by a thi ...

). The lumbricals and interossei also extend the IP (interphalangeal) joints of the fingers by insertion into the extensor hood; their paralysis results in weakened extension. The combination of hyperextension at the MCP and flexion at the IP joints gives the hand its claw like appearance.

Ulnar paradox

The ulnar nerve also innervates the ulnar (medial) half of the

flexor digitorum profundus muscle The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm. Together t ...

(FDP). If the ulnar nerve lesion occurs more proximally (closer to the elbow), the flexor digitorum profundus muscle may also be denervated. As a result, flexion of the IP joints is weakened, which reduces the claw-like appearance of the hand.http://www.orthoteers.org/content/documents/Exam_hand.pdf (Instead, the fourth and fifth fingers are simply paralyzed in their fully extended position.) This is called the "ulnar paradox" because one would normally expect a more proximal and thus debilitating injury to result in a more deformed appearance. Simply put, as reinnervation occurs along the ulnar nerve after a high lesion, the deformity will get worse (FDP reinnervated) as the patient recovers - hence the use of the term "paradox". A simple way to remember this is: 'the closer to the Paw, the worse the Claw'.

Prevention

Preventive therapy is recommended to preserve the function of the fingers. This may include physical exercise, stretching, proper bodily function and myofascial release (massage, foam roller). Exercises are focused on the forearm muscles, such as the extensor carpi ulnaris; extensor digitorum to antagonize the flexion of the fingers. Massaging the forearm muscles also alleviates the tightness that occurs with muscles

exertion Exertion is the physical or perceived use of energy.Newton's Third Law, Elert, Glenn. “Forces.” ''Viscosity – The Physics Hypertextbook'', physics.info/newton-first/. Exertion traditionally connotes a strenuous or costly ''effort'', resulting ...

Stretching Stretching is a form of physical exercise in which a specific muscle or tendon (or muscle group) is deliberately flexed or stretched in order to improve the muscle's felt elasticity and achieve comfortable muscle tone. The result is a feeling ...

allows the muscles more

flexibility Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a bo ...

, decreasing interference with the innervations of the

to the fingers. The so-called "Hand of Benediction" is caused by median nerve lesions. The hand will show hyperextension of the

s (MCP) from the unopposed

as well as weakened extension and flexion of the Interphalangeal (IP) joints of the 2nd and 3rd digits (index and middle) due to deficits in the radial lumbricals and lateral half of the

flexor digitorum profundus The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm. Together t ...

. The pathogenesis is similar to that of ulnar clawing (loss of the relevant lumbricals and the flexor digitorum profundus along with unopposed action of forearm extensors), and a median claw hand will appear similar to an ulnar claw when the patient with a median claw is asked to make a fist. The following signs may be used to clinically distinguish median nerve clawing from ulnar nerve clawing.

Dupuytren's contracture

Dupuytren's contracture Dupuytren's contracture (also called Dupuytren's disease, Morbus Dupuytren, Viking disease, palmar fibromatosis and Celtic hand) is a condition in which one or more fingers become progressively bent in a flexed position. It is named after Guilla ...

is a deformity of the hand due to thickening and fibrosis of the palmar aponeurosis and eventual contracture of the 4th and 5th digits. Presenting as a small hard nodule in the base of the ring finger, it tends to affect the ring and little finger as puckering and adherence of the palmar aponeurosis to the skin. Eventually the MCP and IP joints of the 4th and 5th digits become permanently flexed. This claw appearance can be distinguished from an ulnar claw in that the MCP is flexed in Dupuytren's but hyperextended in ulnar nerve injuries.

Klumpke paralysis

A claw hand can result of injuries to the inferior

brachial plexus The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in th ...

(C8–T1). The condition may arise from the limb being suddenly pulled upward. For example,

Klumpke paralysis Klumpke's paralysis is a variety of partial palsy of the lower roots of the brachial plexus. p.1046 The brachial plexus is a network of spinal nerves that originates in the back of the neck, extends through the axilla (armpit), and gives rise to ne ...

can occur from excessive pulling of the infant's forelimb during parturition.

Treatment

Treatments excluding

surgery Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pat ...

can include

physical therapy Physical therapy (PT), also known as physiotherapy, is one of the allied health professions. It is provided by physical therapists who promote, maintain, or restore health through physical examination, diagnosis, management, prognosis, patient ...

and

occupational therapy Occupational therapy (OT) is a global healthcare profession. It involves the use of assessment and intervention to develop, recover, or maintain the meaningful activities, or ''occupations'', of individuals, groups, or communities. The field of ...

rehabilitation. Range of motion can be regained by using hand splints to stretch the impaired hand and to prevent overstretching. Using splints will initiate flexion in the

metacarpophalangeal joints The metacarpophalangeal joints (MCP) are situated between the metacarpal bones and the proximal phalanges of the fingers. These joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavi ...

while also allowing

extensions Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * Ex ...

and

flexion Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

in the interphalangeal joints, thus increasing range of motion. Beneficial exercise will be any that strengthens the interosseous muscles and lumbricals. By exercising individual fingers and thumb in adduction and abduction motion in

pronation Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

position, interosseous muscles will gain strength. Exercises to strengthen lumbricals, strengthen flexion in the metacarpophalangeal joint, and extension in the interphalangeal joints are beneficial. Repetitive motion of pronation and supination are also effective exercises for rehabilitation. Exercising

and

supination Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

with a handle or screwdriver attachment will help stimulate the nerves. A lateral pinch and recurring grip can also be applied for supination and pronation.

Incidence

Older males are more likely to have ulnar mononeuropathy than females without regard to BMI. 95% of females with a BMI less than a 22.0 have a higher risk of ulnar nerve damage from a lack of adipose “cushion”, and external compression at the elbow is a more important cause of ulnar mononeuropathy among females than males. Both males and females with high

grip strength Grip strength is the force applied by the hand to pull on or suspend from objects and is a specific part of hand strength. Optimum-sized objects permit the hand to wrap around a cylindrical shape with a diameter from one to three inches. Stair rai ...

, such as string musicians, are more susceptible to ulnar mononeuropathy, as are those who experience severe or sustained compression of the ulnar nerve.

References

External links

{{PNS diseases of the nervous system Medical signs