10 The Hand and Upper Limb Structure List

THE HAND

Learning Objectives

By the end of the course students will be able to:

1. Describe the position of tendons, nerves, and vessels beneath the flexor retinaculum.
2. Identify the prominent features of carpals, metacarpals, and phalanges associated with the hand (listed in the lab manual).
3. Define the thenar, hypothenar, central, and adductor-interosseous compartments of the hand. Describe the muscles contained within these regions and the functional significance of each.
4. Correlate any fractures or deep cuts of the hand with functional disruptions of associated muscular and neurovascular structures.
5. Describe the movements of the fingers and thumb and the sensory innervation to the hand.

Reference: Moore, Clinically Oriented Anatomy, chapter 6

Particularly Relevant Blue Boxes in Moore:

●Dupuytren Contracture p. 789

● Hand Infections p. 789

●Tenosynovitis p. 789

● Laceration of Palmar Arches, p. 790

●Lesions of Median Nerve, p. 790 

To access the Netter Presenter Database click here

Grant’s Dissector, 15th Edition, pp 46 – 52 click here

To access Gray’s Photographic Dissector section on the Hand click here

To access the Primal Pictures software click here 

Check out the Primal Pictures model of the Hand
THE HAND (Moore 771-792)

The skeleton of the hand consists of  8 CARPAL BONES of the wrist,

5 METACARPALS, and 14 PHALANGES (Netter 439,  443,  444,  445).

Metacarpals. Each metacarpal has a proximal base, a shaft and a distal head. The base of each metacarpal contactes the distal row of carpal bones to forma a carpometacarpal joint. The head of each metacarpal contacts a proximal phalanx at a metacarpophalangeal  (MP) joint.

Phalanges. Three rows of phalanges constitute the skeleton of the second though fifts digits; the first digit (thumb) has only two phalanges. The proximal row articulates with the metacarpals at the MP joints. The middle row articulates with the proximal row of phalanges at the proximal interphalangeal (PIP) joints. The distal row articulates with the middle row of phalanges at the distal interphalangeal (DIP) joints.

Surface Anatomy of the Hand

The DORSUM of the HAND (Netter 457) contains long extensor tendons and the dorsal interosseous muscles. You can observe the extensor tendons on your own hand when your fingers and hand are fully extended.

The skin on the PALM of the HAND is thick because it is required to withstand the wear and tear of work and play. It is richly supplied with sweat glands, but it contains no nair or sebaceous glands.  The skin presents several more or less constant longitudinal and transverse flexion creases, where the skin is firmly bound to the deep fascia.

Fascia of the Palm

The deep fascia of the palm is continuous proximally with the antebrachial fascia (fascia of the forearm) and at the borders of the palm with the fascia on the dorsum of the hand. The fascia is thin over the thenar and hypothenar eminences but it is thick in the palm where it forms the palmar aponeurosis and in the digits where it forms the fibrous digital sheaths.

Palmar Aponeurosis (Netter 446)

This strong, well-defined triangular part of the deep fascia of the hand covers soft tissues and overlies the long flexor tendons of the palm. The proximal end of the palmar aponeurosis is continuous with the flexor retinaculum and the tendon of the flexor palmaris longus muscle. The distal end of the aponeurosis divides at the roots of te digits into four longitudinal bands. Each band is attached to the base of the proximal phalanx and fused with the fibrous digital sheath.

The space within the palm may be roughly divided into a floor, two walls, and a roof.

The intrinsic muscles of the thumb and little finger form the walls of the palm. You will notice that on your palm the first and fifth metacarpals are surrounded by bulky musculature. This musculature is called the THENAR (thumb) and the HYPOTHENAR (little finger) EMINENCES. Each eminence is composed of three muscles: an ABDUCTOR, a FLEXOR, and an OPPONENS. Helpful tip: these muscles are alphabetically arranged from superficial to deep. The three hypothenar muscles are innervated by the ULNAR NERVE and the three thenar muscles by the MEDIAN NERVE.

Dupuytren’s contracture is a progressive fibrosis of the the palmar aponeurosis, resulting in shortening and thickening of the fibrous bands that extend the aponeurosis to the bases of the phalanges. These fibrotic bands pull the digits into such marked flexion at the metacarpophalangeal joints that they cannot be straightened.

Flexor and Extensor Retinaculae

The contents of the palm include the long flexor tendons of the forearm, both superficial and deep, and their associated LUMBRICAL MUSCLES (Netter 448).

Between the palmar aponeurosis and the deep muscles of the palm are two potential spaces that are surgically important (Netter 450) . They lie between the flexor tendons and the fascia covering the deep muscles in the floor of the palm. The spaces are bounded medially andlaterally by fibrous septa passing from the edges of the palmar aponeurosis and the metacarpal bones. A fibrous medial septum extends deeply from the border of the palmar aponeurosis to the fifts metacarpal. Medial to this septum is the hypothenar compartment, containing the three hypothenar muscles and concerned with movements of the little finger. Similarly, a fibrous lateral septum extends deeply from the lateral border of the palmar aponeurosis to the first metavarpal bone. Lateral to this compartment is the thenar compartment containing the thenar muscles concerned with movement of the thumb. Between the thenar and hypothenar compartments is the intermediate or central compartment containing the flexor tendons and their sheaths. From the lateral border of the palmar aponeurosis, another fibrous septum passes obliquely and posteriorly to the third metacarpal bone. This creates potential medial and lateral midpalmar spaces. The adductor compartment is the deepest muscular plane of the palm. It contains the adductor pollicis muscle.

Intrinsic Muscles of the Hand (Netter 452)

The intrinsic muscles of the hand are on the palmar aspect and are innervated by branches of the ulnar or median nerves. They can be divided into three groups:

1) the thumb of thenar muscles in the thenar compartment

2) the little finger or hypothenar muscles in the hypothenar compartment

3) the lumbrical muscles in the central compartment and the interosseous muscles between the metacarpal bones

The three short thenar muscles (abductor pollicis brevis, flexor pollicis brevis and opponens pollicis) produce the thenar eminence and are chiefly responsible for opposition of the thumb. These muscles are all supplied by the recurrent branch of the median nerve.

The abductor pollicis brevis muscle abducts the thumb at the carpometacarpal joint and assists the opponens pollicis muscle during early stages of opposition of the thumb by rotating its proximal phalanx slightly medially.

The flexor pollicis brevis muscle flexes the thumb at the carpometacarpal and metacarpophalangeal joints and aids in opposition of the thumb.

The opponens pollicis muscle lies deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis. It opposes the thumb (by flexing and rotating it medially during grasping). Opposition involves extension initially, then abduction, flexion, medial rotation and usually adduction.

The adductor pollicis muscle is a fan-shaped muscle located in the adductor compartment of the hand. It thas two heads that are separated by a gap through which the radial artery passes. It adducts the thumb and is supplied by the deep branch   fthe ulnar nerve.

Because of the complexity of the movement, opposition of the thumb may be affected by most nerve injuries in the upper limb. If the median nerve is severed in the forearm or affected by carpal tunnel syndrome, the thumb cannot be opposed. However, the intact abductor pollicis longus and adductor pollicis muscles, supplied by the posterior interosseous (from the radial nerve) and the ulnar nerves, respectively, may imitate opposition. The recurrent branch of the median nerve that supplies the thenar muscles lies superficially and may ybe severed by relatively minor lacerations of the palm involving th thenar eminence.

Carpal Tunnel Syndrome. Any lesion that significantly  reduces the size of the carpal tunnel (e.g., inflammation of the flexor retinaculum, arthritic changes or tenosynovitis of the tendon sheaths) may cause compression of the median nerve. Because this nerve has two terminal branches that supply the skin of the hand, there is often tingling (paresthesia), ansence of tactile sensation (anesthesia), or diminished sensation (hypoesthesia) in the digits. Because the mediann nerve sends a palmar cutaneous branch to the flexor retinaculum to supply most o fthe palm, there is often no sensory impairment of this area. Often there is a progressive loss of coordination and strength in the thumb, owing to weakness of the abductor pollicis brevis, flexor pollicis brevis and opponens pollicis, if the cause of the median nerve compression (and its motor branch, the recurrent median nerve) is not alleviated. This results in difficulty in performing fine movements off the thumb. As the thenar and lateral two lumbrical muscles of the other digits are also supplied by the mediann nerve, the usefulness of the first to third digits may be diminished. In severe cases of compression of the median nerve, there may be wasting or atrophy of the thenar muscles.

Injury to the ulnar nerve may be caused by a fracture of the medial epicondyle and results in a claw hand in which the ring and little fingers are hyperextended at the metacarpophalangeal joints and flexed at the proximal interphalangeal joint. It results in loss of abduction and adduction of thedigits and flexion at the metacarpophalangeal joints because of paralysis of the palmar and dorsal interossei muscles and medial two lumbricals.  It also produces a wasted hypothenar eminence and leads to a loss of adduction of the thumb because of paralysis of the adductor pollicis muscle.

The three short hypothenar muscles are concerned with movements of the little finger. They produce the hypothenar eminence and are all supplied by the deep branchh of the ulnar nerve. They are:

Abductor digiti minimi – abducts the 5th digit and helps to flex its proximal phalanx

Flexor digiti minimi -lies lateral to the abductor digiti minimi and  flexes the proximal phalynx of the 5th digit at the metacarpophalangeal joint

Opponens digiti minimi – lies deep to the abductor and flexor muscles othe the 5th digit. It draws the 5th metacarpal bone anteriorly and rotates it laterally, thereby deepening the hollow of the palm and bringing the 5th diigit in opposition with the thumb

The palmaris brevis muscle is a small quadrilateral muscle lying deep to the skin of the hypothenar eminence. It is a relatively unimportant muscle, except that it covers and protects the ulnar nerve and artery. It is supplied by the superficial branch of the ulnar nerve.

The lumbrical muscles (Netter 448) are four slender muscles, one for each digit. They originate on the tendons of the flexor digiorum profundus muscles and insert along the lateral sides of the extensor expansions of digits 2 – 5. They flex the digits at the metacarpophalangeal joints and extend the interphalangeal joints. Lumbricals 1 and 2, to the index and middle fingers, are supplied by the median nerve; lumbricals 3 and 4, to the ring and little fingers, are supplied by the deep branch o fthe ulnar nerve.

The interosseous muscles(Netter 452)  are arranged in two layers: three palmar and four dorsal muscles. They are located between the metacarpal bones and are all supplied by the deep branch of the ulnar nerve. The dorsal interossei abduct the digits (DAB – Dorsal ABduct), and the palmar interossei adduct the digits (PAD Palmar ADduct).

The Extrinsic Muscles of the Hand

The long flexor tendons of he extrinsic muscles of the hand – the flexor digitorum superficialis and profundus, enter a common synovial sheath deep to the flexor retinaculum.(Netter 450, 448) They then pass deep to the flexor retinaculum and enter osseofibrous digital tunnels. There are two tendons in each tunnel. To enable these tendons to slide freely over each other during movements of the digits, each of them is covered by a synovial membrane. Near the base of the proximal phalanx, the tendon of the flexor digitorum superficialis splits and surrounds the tendon of the flexor digitorum profundus. The halves of the tendon of the FDS are attached to the margins of the middle phalanx. The tendon of the FDP, after passing through the split in the tendon of the FDS, passes distally to attach to the base of the distal phalanxv ia an extensor expansion hood (Netter 451) . This structure provides the insertion of the lumbrical and interosseous muscles and the extensor indicis and extensor digit iminimi muscles.

The synovial sheaths of the flexor tendons of the hand may become infected, e.g., by entry of a foreign object into a digit. When tenosynovitis (inflammation of the tendon and digital synovial sheath) occurs, the digitt swells and movement becomes painful. Because the tendons of the second, third and fourth digits nearly always have separate digital synovial sheaths, the infection is usually confined to the digit concerned. In neglected infections, however, the proximal ends of these sheaths may rupture and infection may spread to the midpalmar fascial spaces.

Because the synovial sheaths of the thumb and little finger are often continuous with the common flexor synovial sheath, tenosynovitis in these digits may spread to the common synovial sheath. As there are variations in the connections between the common synovial sheath and the digital sheaths, the degree of spreading of infections from the digits depends on whether or not there are connections between them. Infections of the second, third and fourth digits are likely to remain localized because their digital synovial sheaths are connected with the common flexor synovial sheath in only about 10% of cases.(Blue Box p. 789 – Hand Infections).

Trigger finger results from stenosing tenosynovitis or occurs when the flexor tendon develops a nodule or swelling that interferes with its gliding through the pulley, causing an audible clicking or snapping.

Mallet finger (baseball finger) is a finger with permanent flexion of the distal phalanx due to avulsion on the medial and lateral bands of the extensor tendon to the distal phalynx. Boutonniere deformity is a finger with abnormal flexion of the middle phalanx and hyperextension of the distal phalanx due to an avulsion of the central band of the extensor tendon to the middle phalanx or rheumatoid arthritis.

Nerves in the Hand (Netter 452; 459)

The median nerve (Netter 452; 463) enters the hand through the carpal tunnel, deep to the flexor retinaculum, between the tendons of the flexor digitorum superficialis and flexor carpi radialis. The median nerve supplies motor fibers to the three thenar muscles and the first and second lumbricals. It also sends cutaneous sensory fibers to the lateral palmar surface, the sides of the first three digits, the lateral half of the fourth digit and the dorsum of the distal halves of these digits.

The ulnar nerve (Netter 464) leaves the forearm by emerging from deep to the tendon of the flexor carpi ulnaris. It passes distally on the flexor retinaculum alongside the lateral border of the pisiform bone; the ulnar artery is on its lateral side. The ulnar nerve and artery are bridged over by a slender band of connective tissue which forms a small tunnel (Guyon’s canal). Just proximal to the wrist, the ulnar nerve gives off a palmar cutaneous branch which passes superficial to the flexor retinaculum, and to the palmar aponeurosis and supplies the skin of the medial side of the palm. It also gives off a dorsal cutaneous branch which supplies the medial half of the dorsum of the hand, the 5th digit and the medial half of teh 4th digit. At the distal border of the flexor retinaculum, the ulnar nerve ends by dividing into a superficial and a deep branch.

The superficial branch of the ulnar nerve supplies cutaneous fibers to the anterior surfaces of the medial one and one-half digits. The deep branch of the ulnar nerve supplies motor fibers to the hypothenar muscles, the medial two lumbrical muscles, the adductor pollicis and all the interosseous muecles.

The radial nerve (Netter 466) supplies no hand muscles. Its terminal branches, superficial and deep, arise in the cubital fossa. The deep branch of the radial is motor to muscles on the dorsumm of the forearm, including the extensor policis longus and brevis and teh abductor pollicis longus. The superficial branch of the radial nerve is entirely sensory. It pierces the deep fascia of the dorsum of the wrist and supplies skin and fascia over the lateral two-thirds of the dorsum of the hand, the dorsum of the thumb, and proximal parts of the lateral one and one-half digits (Netter 456).

Blood Supply to the Hand

The arterial supply (Netter 453; Moore 779-781)) of the hand is formed by two arterial ARCHES in the hand: a SUPERFICIAL and a DEEP. The superficial arch of the palm is formed primarily from the ulnar artery and lies between the palmar aponeurosis and the flexor tendons. The deep arch of the palm is formed primarily from the radial artery as it reenters the palm between the 1st and 2nd metacarpals. The deep arch runs in the floor of the palm deep to the long flexor tendons and adductor pollicis muscle.

The PALMAR DIGITAL ARTERIES branch from the superficial arch and travel along with a nerve to the base of each digit. There are two arteries in each digit that pass on the medial and lateral sides of the phalanges; in this location the nerves and vessels are protected from pressure or trauma.

The muscles of the forearm and hand are very finely balanced. If any muscle group is damaged, this balance can be lost and various clinical deformities or disabilities may result.  For example, the wrist extensors are necessary to balance the pull of the finger flexors in producing a strong grip. Another example of the importance of balance is seen in the intrinsic hand muscles and the  extrinsic forearm muscles. The interossei and the lumbricals in the hand insert dorsally onto the extensor expansion, but effectively distal to the metacarpophalangeal (MP) joint. These muscles flex the MP joint, but also pull on the extensor expansion to extend the fingers at the interphalangeal joints (IP).