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   Hand

Hand Injuries

Carpal tunnel syndrome - compression of a nerve as it goes through the wrist, often making your fingers feel numb

Injuries that result in fractures, ruptured ligaments and dislocations

Osteoarthritis - wear-and-tear arthritis, which can also cause deformity

Tendinitis - irritation of the tendons

Dupuytren's contracture - a hereditary thickening of the tough tissue that lies just below the skin of your palm

Trigger finger - an irritation of the sheath that surrounds the flexor tendons, sometimes causing the tenMinor arm injuries are common. Symptoms often develop from everyday wear and tear, overuse, or an injury. Arm injuries are often caused by:

Hand injuries are common and account for 5-10% of emergency  visits nationwide. The complexity of the hand and the similarities in clinical presentation of different injuries make understanding of hand anatomy and function, good physical examination skills, and knowledge of indications for treatment indispensable for the emergency physician.

Terminology

Thorough knowledge of the anatomy and functions of the hand is required for proper diagnosis and treatment. Use of proper terminology prevents confusion that may compromise the care of patients with hand injuries. The following is a brief review of standard terminology and key anatomic structures.

The hand and digits have palmar (volar) and dorsal surfaces and radial and ulnar borders.

The digits are best described using their standard names rather than numbers.

The proper names of the 5 digits beginning radially are thumb, index finger, long or middle finger, ring finger, and little finger.

Motion and position: Standard terminology also applies to motions and positions of the hand and digits.

Supination of the forearm positions the hand with the palmar surface superior. Pronation places the palmar surface inferior.

Lateral motion of the hand, relative to the forearm, is described as radial deviation when the palm is supinated or ulnar deviation when the palm is pronated.

Anterior and posterior motions of the hand, relative to the forearm, in its anatomic position are described as flexion and extension, respectively.

Abduction of the digits refers to motion away from the middle finger and adduction to motions toward the middle finger.

The fingers are in extension when held in the anatomic position. Movement of the digits dorsally is hyperextension, while movement toward the palm is flexion. In addition to flexion and extension, the thumb may move in toward the other digits (opposition) or away from them (retroposition).

Anatomy

Surface anatomy: Three creases are present on the palmar surface of the digits. The distal and middle palmar creases correspond to the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints, respectively. The proximal digital palmar crease does not overlie a joint as the MCP is more proximal. The long thenar crease partially encircles the thenar eminence and overlies the metacarpophalangeal (MCP) joint.

Bony anatomy: The wrist is composed of 8 carpal bones arranged in 2 rows of 4. The flexor retinaculum together with the carpal bones forms the carpal tunnel. The median nerve passes through the carpal tunnel with the tendons of the flexor digitorum profundus and superficialis. The ulnar nerve enters the hand passing between the hook of the hamate bone and the pisiform bone in the Guyon canal.

The metacarpal bones articulate with the wrist at the carpometacarpal (CMC) joints. The metacarpophalangeal (MCP) joints are formed by the articulation of the metacarpal bones with the proximal phalanges (see Media file 1). The heads of the metacarpals form the knuckles, which are seen dorsally with the closed fist. The thumb has only 1 interphalangeal (IP) joint, while the rest of the digits have proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints


Metacarpophalangeal joints of the digits

Metacarpophalangeal joints of the digits

Each of the MCP, PIP, and DIP joints has collateral ligaments, which provide lateral stability, and a volar plate, which prevents hyperextension. The volar plate is damaged frequently in subluxation and dislocation injuries.

Blood supply: The blood supply to the hand is derived from the ulnar and radial arteries, which form the superficial and deep palmar arterial arches by anastomosis. In the absence of vascular disease, either artery alone is sufficient to perfuse the entire hand in most of the population.

Extrinsic and intrinsic muscles: The muscles of the hand are designated intrinsic or extrinsic. Extrinsic muscle bellies are in the forearm and their tendons insert into the hand, while intrinsic muscles both arise in and insert in the hand. The muscles of the hand and digits also are named according to their function as either flexors or extensors.

Forearm flexors: The forearm flexors are extrinsic muscles of the hand. These muscles arise from the medial epicondyle of the humerus and include the following:

Flexor carpi radialis

Palmaris longus

Flexor carpi ulnaris

Flexor digitorum profundus

Flexor digitorum superficialis

The tendons of flexor carpi radialis (FCR), palmaris longus, and flexor carpi ulnaris (FCU) are visible in the forearm (see Media file 2). The palmaris longus is absent in about 14% of the population. The median nerve lies between the palmaris longus and the flexor carpi radialis (to the ulnar side of the FCR). The flexor carpi ulnaris is a good landmark to locate the ulnar nerve and artery, which lie to the radial side of the FCU.

Volar tendons at the wrist. These can be used as landmarks for injections.

Flexion of the fingers is controlled by the flexor digitorum profundus and superficialis muscles. Both of the finger flexors lie on the ulnar side of the wrist with the median and ulnar nerves and the ulnar artery. The flexor carpi ulnaris and radialis flex the wrist when acting together and cause deviation to their respective active sides when contracting separately.

Intrinsic muscles of the hand: Branches of the median and ulnar nerves innervate all the intrinsic muscles of the hand. They can be divided into 3 groups as follows: thenar (thumb), hypothenar (little finger), and lumbricals.

The thenar eminence is formed by the extensor pollicis brevis and the 3 short thenar muscles: the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. These muscles have short tendons that insert onto the proximal phalanx of the thumb. They are innervated by the recurrent branch of the median nerve. The superficial location of this branch renders it vulnerable to seemingly trivial trauma to the thenar eminence.

The adductor pollicis adducts the thumb and by doing so, provides grip. It is innervated by the ulnar nerve.

The lumbricals flex the digits at the MCP joints and extend the IP joints. They place the fingers in the writing position.

Seven interosseous muscles are located between the metacarpal bones; 3 are palmar and 4 are dorsal. The palmar interossei adduct, while the dorsal interossei abduct.

Forearm extensors: Eleven muscles extend the wrist, hand, and digits (see Media file 3). The forearm extensors pass into the hand in 6 compartments. All forearm extensors arise from the lateral epicondyle of the humerus. They are innervated by the radial nerve.


Sagittal section of extensor compartment

Sagittal section of extensor compartments
Innervation: The median, ulnar, and radial nerves supply all of the sensory and motor innervation to the hand. The superficial volar and dorsal distributions of the sensory nerves are shown in Media files 4-5. The median nerve enters the hand via the carpal tunnel and often is involved in carpal tunnel syndrome. The median nerve sends motor fibers to the 3 short thenar muscles and the first and second lumbricals. The ulnar nerve sends motor fibers to the hypothenar muscles, the ulnar 2 lumbricals, the adductor pollicis, and all of the interosseous muscles. The radial nerve sends no motor branches to the intrinsic muscles of the hand.

Pathophysiology

The pathophysiology of soft tissue injuries of the hand is diverse. The most common mechanisms of injury are blunt trauma (eg, crush injury, contusions, abrasions), laceration, avulsion, ring avulsion, and burns. Besides skin and superficial tissues, the many muscles, ligaments, and tendons of the hand are vulnerable to injury, as are the nerves and blood vessels that supply these structures. Damage to these structures may create permanent functional and/or sensory deficits specific to the site of injury.

Nerve injuries

Blunt, penetrating, and crush injuries to the hand result in nerve damage. Nerve injury is divided into 3 types, as follows:

Neurapraxial injury occurs when a nerve is bruised or stunned but remains essentially intact.

Axonotmesis describes a partial injury in which the axonal core of a nerve is damaged but the myelin sheath remains intact. These injuries usually regenerate at a rate of 1-3 mm per day.

Neurotmesis is complete disruption of both axons and myelin sheath. It requires re-approximation of the nerve endings for healing to occur.

Dislocations

DIP: The DIP joint is stabilized not only by collateral ligaments but by adjacent flexor and extensor tendons, making dislocations of this joint uncommon. If dislocation does occur, it usually is directed dorsally and often is associated with an open wound. DIP joint dislocations are detected easily by physical examination.

PIP: The ligaments of the PIP joints are the most commonly injured in the hand. Dorsal dislocations are the most common and usually are the result of a blow to the extended digit, causing a combination of axial loading and dorsal deviation. Volar dislocations are uncommon because the joint does not resist motion in this direction. Lateral dislocation is the result of a tangential load applied to the extended digit that ruptures a collateral ligament and disrupts the volar plate. Ulnar deviation, with rupture of the radial collateral ligament, is more common than radial deviation.

MCP: Dislocation of the MCP joint is uncommon, but when it occurs deviation is usually dorsal. The common mechanism of injury is the application of a dorsally directed force that is sufficient to rupture the volar plate. Dorsal dislocations in 60-90° of hyperextension and without intervening soft tissue are simple dislocations. Complex dislocations have the volar plate entrapped between the metacarpal and the proximal phalanx. Complex dislocations are less striking in their clinical presentation but are more serious injuries.

Thumb: The IP joint of the thumb is very stable and seldom injured. Dislocations usually are dorsal and often open. The MCP joint of the thumb is one of the most frequently injured joints. Injury most commonly is caused by hyperextension force sufficient to rupture the volar plate and cause dorsal dislocation. As in MCP joints of the other digits, dorsal dislocation of the MCP joint may be a simple subluxation or complex dislocation. The complex dislocation is complicated by entrapment of the proximal phalanx.

Ligament injuries/sprains

Joints of the digits are stabilized by the combination of collateral ligaments and the volar plate. Stretching or partial tearing of the ligaments results in a sprain. The volar plate may be injured alone or in combination with the collateral ligaments. The common mechanism for an isolated volar plate injury is hyperextension during an axial load. Pain location is a good indicator of the site of injury. For example, lateral pain suggests collateral ligament injury, whereas pain on the palmar surface of the joint suggests volar plate injury. Loss of stability more commonly is associated with joint dislocation.

Sprains of the PIP and MCP joints produce pain and swelling but may lead to little or no instability. They are classified as first, second, or third degree. If the joint does not open at all but has pain with stressing of a ligament, the injury is first degree. A joint that is opened slightly in the ulnar or radial direction is defined as having a second-degree injury. This finding suggests a unilateral collateral ligament tear. A joint that is opened by at least 3-5 mm must have damage to at least 2 of the 3 structures stabilizing the joint (ie, volar plate, 2 collateral ligaments). This is referred to as a third-degree sprain or an unstable joint. Serious ligamentous injuries occur frequently and often are misdiagnosed because a mild sprain may have a similar presentation. Sequelae from missed ligamentous injuries range from chronically painful to chronically unstable or deformed joints.

Sprains of the MCP joint are rare because of the anatomy of the joint, the laxity of the collateral ligaments, and the protection afforded the joints by surrounding structures. Hyperextension of the extended digit is the most common mechanism causing sprains. Diagnosis is indicated by a stable but painful edematous joint.

The ability to hold objects between the thumb and 4 fingers is an essential function of the hand and depends upon an intact ulnar collateral ligament (UCL). Injury to the UCL is known as the gamekeeper's thumb or skier's thumb. This is because Scottish gamekeepers frequently damaged their UCLs killing game. The head of a small animal was placed between the thumb and index finger and a hyperextension/longitudinal traction force applied to the animal's cervical spinal cord by abruptly yanking the lower extremities. In a certain percentage of these procedures, the UCL of the gamekeeper was disrupted.

In modern times, skiing is the activity that most often causes UCL injury. However, a history of a missed punch, a fall onto the thumb, or the forceful removal of an object from the flexed hand also should be considered suggestive of UCL injury.

The common mechanism of injury is the forceful abduction of the thumb. Any patient with pain in the distribution of the UCL or inability to forcefully oppose the thumb has an injury of the UCL until proven otherwise.

Rupture of the radial collateral ligament of the thumb is much less common than UCL rupture. The mechanism of injury is forceful adduction of the thumb in any position.

Tendon injuries

The extensor tendons' superficial location predisposes them to injury from seemingly trivial lacerations as well as avulsions, crushes, and burns. Flexor tendon injuries can be caused by lacerations. Tendon injuries also may be sustained as the result of forced hyperextension or forced flexion of an extended digit. Injuries may include complete or partial transection, avulsion, or maceration. Whenever a tendon is damaged, particularly with an open injury, the vessels and nerves that are in close proximity may be injured.

Understanding that a tendon may be 70-90% lacerated and still functional is critical. Damage to these tendons may result in such findings as boutonnière deformity (see Media files 6-7) and mallet finger (see Media file 8).


Boutonnière deformity due to closed central tendon rupture


Mallet finger due to loss of central extensor tendon to the distal phalanx

Mortality/Morbidity

Soft tissue injuries of the hand rarely are life threatening..

Hand injuries are assessed:

Clinical

History

General

Age

Hand dominance

Occupation/hobbies

History of previous hand problems

Other past medical history, especially diabetes, vascular problems

Smoking history

When and where did this injury take place? In cases involving trauma, ascertain when and where the injury occurred to determine the likelihood of severe injury and probability of contamination with foreign matter.

How was the trauma sustained? This gives clues to the most likely injury. For example, the water skier who injured a hand when the towing line was removed forcefully from that hand is likely to have an injury to the flexor tendon mechanism.

What was the posture of the hand at the time of the injury? Structures in the hand slide with movement. The tissue under a bruise or laceration may not be the same tissue that was present when the injury was sustained because of movement of structures in the hand (eg, extensor tendons injured with the digits in flexion may not be visible in the wound when digits are extended).

Past history of treatment or surgery in the hand

Physical

The entire upper extremity should be exposed. Note any of the following findings:

Muscle wasting

Color change

Surgical or nonsurgical scars

Asymmetry

Deformities that suggest dislocation

Differences in flexion/extension in the relaxed hand: The relaxed hand is in moderate flexion. The digits on both sides should be in about the same amount of flexion. The little finger usually is in more flexion than the other fingers. If a digit has a marked difference in flexion, the examiner should be suspicious for tendon injury. This finding may be useful in identifying the injury of the patient who is a poor historian.

Dry patches of skin may indicate loss of innervation.

Dimpling over the thenar eminence suggests complex dislocation of the MCP joint of the thumb.

Check range of motion in every joint in the hand, shoulder, and elbow. Ability to pronate and supinate the forearm should be tested actively and passively.

Test grip and pinch strength.

The best way to diagnose a tendon injury in an open wound is by direct visualization during a thorough exploration of the wound.

Examination of extrinsic flexors

Each of these tests is performed with and without resistance.

Flexor pollicis longus: Instruct the patient to bend the tip of the thumb against resistance.

Flexor digitorum profundus: While holding the PIP joint in extension, instruct the patient to bend the tip of the finger.

Flexor digitorum superficialis: While stabilizing the rest of the fingers to block the action of flexor digitorum profundus, instruct the patient to bend the middle joint of the finger.

Palpate the tendons of flexor carpi ulnaris, flexor carpi radialis, and palmaris longus (which is not present in about 15% of individuals) while the patient holds the wrist and fingers in hyperflexion.

Extrinsic extensors arise from the forearm and insert into the hand. The extrinsic extensors pass from the wrist to the hand in 6 tendon compartments.

The first compartment contains the abductor pollicis longus and extensor pollicis brevis. Evaluate by instructing the patient to move the thumb away from the other fingers.

The second compartment contains the extensor carpi radialis longus and extensor carpi radialis brevis. Examine by asking the patient to make a fist and extend the hand at the wrist.

The third compartment contains the extensor pollicis longus. Ask the patient to place the hand palmar side down  on a table and raise the thumb off the surface.

The fourth compartment contains the MCP joint extensors, extensor digitorum communis, and extensor indices proprius (EIP) tendons. Evaluate by asking the patient to extend the fingers. The EIP can be evaluated alone by instructing the patient to make a fist, then extend the index finger.

The fifth compartment contains the extensor digit minimi. Evaluate by asking the patient to make a fist and then to extend the little finger.

The sixth compartment contains the extensor carpi ulnaris. Evaluate by instructing patient to deviate the hand in ulnar direction.

Extrinsic extensors may form adhesions secondary to old trauma. This phenomenon is referred to as extensor tightness.

Extensor tightness is evaluated by passive extension of the MCP joint and flexion of the PIP joint with the wrist in anatomical position. The PIP joint should flex.

Repeat the test with the MCP joint in passive flexion.

If the PIP joint will flex when the MCP joint is extended but not when it is flexed, adhesions are present in the extensors, stopping the simultaneous flexion of the finger MCP and PIP joints.

Intrinsic muscles have their origins and insertions in the hand. They include thenar muscles, lumbricals, interosseous muscles, and hypothenar muscles.

Thenar muscles: The thenar muscles include the abductor pollicis brevis, opponens pollicis, and flexor pollicis brevis. These muscles oppose the thumb. Test by asking patient to place the back of the hand on the table and raise thumb until it rests perpendicular to the hand or to touch the thumb to each finger. Palpate the muscles of the thumb and compare findings to the other side.

Adductor pollicis: Test separately by asking the patient to grasp 2 ends of a piece of cloth and hold them tightly between the thumb and index finger. Flexion of the thumb at the IP joint is called Froment sign and indicates damage to the adductor pollicis or the ulnar nerve.

Interosseous and lumbrical muscles: These muscles flex the MCP joints and extend the IP joints. The interosseous muscles are innervated by the ulnar nerve. Evaluate by asking the patient to spread the fingers and checking the resistance to ulnar and lateral deviation of each digit in abduction. The extrinsic extensors can be used to abduct-adduct the digits if the interossei are deranged. To block their action, ask the patient to place the palm on the table and to hyperextend the digits at the MCP joints.

Hypothenar muscles: The hypothenar muscles include the abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi. Evaluate by asking the patient to deviate the small fingers in an ulnar direction. Palpate the hypothenar eminence while the digit is in abduction.

Joints

The stability of a joint is assessed by active and passive motion.

Pain causes some patients to consciously or unconsciously limit the range of motion of an injured joint. Therefore, administering a digital block may be necessary prior to assessing joint stability.

Evaluate stability by applying anterior, posterior, radial, and ulnar stress to each IP and MCP joint in the extended and flexed positions. Evaluation in the flexed and extended positions is necessary as the volar plate may stabilize a dislocated or subluxated joint in certain positions.

Sensory examination

Thoroughly inspect the skin. Denervated areas are often dry because of loss of sympathetic innervation. This may be useful in children or other patients who cannot give a history.

The immersion test also may be useful in patients who cannot give a history. Denervated skin does not wrinkle  after being exposed to water for 5-10 min.

Two-point discrimination is the best overall test of sensory function. The distance between 2 prongs, beginning at 6 mm, is increased and decreased during the course of the exam. Abnormal discrimination values are less than 6 mm static and less than 3 mm moving. An abnormal discrimination examination implies axonal loss and sensory deficit that may be due to laceration, compression, or contusion of the nerve. If exam findings are abnormal, repeat the test on the unaffected side because the sensitivity and specificity vary from patient to patient.

Circulation

Look for color changes in the nails and skin of the hand.

The Allen test has variable sensitivity, but it may be used to help assess perfusion to the hand.

Compress radial and ulnar arteries at the wrist.

Instruct the patient to open and close the fist to exsanguinate the hand.

Have the patient open the hand.

Release the radial artery.

If the hand fills with blood within 5 seconds, the radial artery is patent. Repeat the test for the ulnar artery.

Causes

Trauma accounts for the majority of these injuries. However, patients also present with complaints that are secondary to infection, burns, or overuse.

        
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