Hand Nerves and Blood Supply

The hand has a complicated web of vessels and nerves. The hand nerves come from the radial, ulnar and median nerves that originate from the brachial plexus. While the hand blood vessels come from the radial and ulnar arteries branch of the brachial artery.

Hand Nerves Supply

The three peripheral nerves that supply the skin and muscles of the wrist and hand include the median, ulnar, and radial nerves.

Median Nerve

The median nerve enters the forearm by coursing anteriorly through the medial aspect of the cubital fossa and passing deep to the lacertus fibrosis, between the heads of the pronator teres muscle. Below the elbow, muscular branches leave the nerve and innervate the FCR, palmaris longus, and pronator teres muscles. The anterior interosseous branch innervates the pronator quadratus, FPL, and the FDP to the index finger and middle fingers and sometimes the ring finger.

Approximately 8 cm proximal to the wrist, the median nerve gives off a sensory branch, the anterior (palmar) cutaneous nerve that passes superficial to the flexor retinaculum and remains outside the carpal tunnel. This nerve innervates the skin in the central aspect of the palm, over the thenar eminence. The rest of the median nerve passes distally to the wrist, where it enters the carpal tunnel, which passes deep to the flexor retinaculum.

See Also: Hand Anatomy

The nerve enters the hand through the carpal tunnel, deep to the tendon of the palmaris longus and in between the tendons of the FPL and FDS (the more radial of the two). From this point, the nerve divides into two branches: a motor branch which passes posterior (dorsal) to the flexor retinaculum and a sensory branch.

Motor Branch: This short branch enters the thenar eminence, where it usually supplies the APB and OP muscles, the FPB (occasionally), and the first and second lumbrical muscles.

Sensory Branch: The sensory anterior (palmar) digital branch innervates the anterior (palmar) surface and posterior (dorsal) aspect of the distal phalanges of the thumb, second and third fingers, and the radial half of the forefinger.

A number of median nerve entrapment syndromes exist (Peripheral Nerve Entrapment), each with their own clinical features and functional implications. For example, entrapment of the median nerve in the carpal tunnel (the so called carpal tunnel syndrome) may result in numbness, pain, or paresthesia of the fingers and thumb and may severely hinder a patient’s ability to perform precision maneuvers due to loss of critical sensory and motor function in the thumb, index, and middle fingers.

See Also: Carpal tunnel syndrome

Ulnar Nerve

The ulnar nerve has been referred to as the nerve of fine movements of the hand. The ulnar nerve originates from the inferior roots of the brachial plexus (C 8–T 1).

Two branches of the ulnar nerve arise in the mid-forearm:

1. The anterior (palmar) cutaneous branch: The anterior (palmar) cutaneous branch supplies a portion of the skin over the hypothenar eminence.
2. The posterior (dorsal) cutaneous branch: About 8–10 cm proximal to the ulnar styloid process, the posterior (dorsal) cutaneous branch of the ulnar nerve splits from the main trunk. The posterior (dorsal) cutaneous branch terminates into two posterior (dorsal) digital branches that supply sensation to the posterior (dorsal) and ulnar aspect of the middle phalanx of the ring and little fingers.

Before reaching the wrist, the ulnar nerve branches to innervate the FDP and the FCU. At the wrist, the ulnar nerve emerges just lateral to the tendon of the FCU as it passes superficial to the flexor retinaculum. The ulnar nerve passes into the hand via the tunnel of Guyon, where it divides into its superficial and deep terminal branches.

The deep (motor) branch supplies the FDM, ADM, ODM, AP, palmaris brevis, third and fourth lumbricals, deep head of the FPB, and the interossei.

The superficial branch, which is primarily sensory with the exception of its innervation to the palmaris brevis, divides into three branches:

1. The first of these three branches is a sensory branch to the ulnar aspect of the little finger,
2. the second is a sensory branch to the central ulnar anterior (palmar) area.
3. The third branch, often referred to as the common digital nerve, innervates the fourth intermetacarpal space.

The common digital nerve further divides into two proper digital nerves supplying the ulnar portion of the ring finger and the radial portion of the little finger.

A number of ulnar nerve entrapment syndromes exist each with their own clinical features and functional implications.

See Also: Cubital Tunnel Syndrome

Radial Nerve

As the radial nerve enters the cubital fossa, it typically splits into a superficial and deep branch.

The superficial branch typically courses distally along the lateral border of the forearm under cover of the brachioradialis muscle and tendon. At the wrist this branch divides into four to five digital branches, which provide cutaneous and articular innervation. The cutaneous innervation includes the lateral two thirds of the dorsum of the hand and the posterior (dorsal) lateral 21/2 fingers to the proximal phalanx. All of the motor branches of the radial nerve are located in the forearm.

The deep branch (posterior interosseous nerve) typically penetrates the anterior (ventral) surface of, and passes through, the supinator muscle. It reaches the deep region of the posterior forearm by passing through the arcade of Frohse.

The nerve courses subcutaneously from the midportion of the forearm to an area adjacent to the styloid process of the radius and terminates on the posterior aspect of the wrist.

Radial nerve entrapment may result in a loss of extension at the wrist and MCP joints of the fingers, and thumb extension and abduction. Since the wrist extensor muscles are synergists and stabilizers for the finger flexor muscles during gripping, this loss can significantly hamper hand function.

Hand Blood Vessels

The brachial artery bifurcates at the elbow into radial and ulnar branches, which are the main hand blood vessels.

Radial Artery

The radial artery is formed from the lateral branch of the bifurcation of the brachial artery. The artery gives off branches in the proximal portion of the forearm that form an anastomosis around the elbow joint. It runs distally under the cover of the brachioradialis muscle.

Just proximal to the wrist, it is located between the brachioradialis and the FCR tendons. A small branch called the superficial anterior (palmar) artery leaves the radial artery 5–8 mm proximal to the tip of the radial styloid, passes between the FCR and the brachioradialis, and continues distally to contribute to the superficial anterior (palmar) arch, which supplies the thenar mass.

The radial artery has seven major carpal branches: three posterior (dorsal), three anterior (palmar), and a final branch that continues distally.

See Also: Forearm Muscles Anatomy

Ulnar Artery

The ulnar artery originates as the medial branch from the bifurcation of the brachial artery. It too gives off branches in the proximal portion of the forearm that form an anastomosis around the elbow joint. The artery passes posterior (dorsal) to the ulnar head of the pronator teres and courses distally deep to the FDS, at which point it passes in the groove between the FCU and FDP, in the company of the ulnar nerve.

In the proximal portion of the forearm, the artery gives off a common interosseous branch. The artery bifurcates, giving rise to the anterior and posterior interosseous arteries, which provide blood to structures in the deep anterior and posterior compartments of the forearm. The artery emerges at the wrist, just lateral to the tendon of the FCU. It then passes through the tunnel of Guyon and enters the superficial compartment of the hand.

At the level of the carpus, the ulnar artery gives off a latticework of fine vessels that span the posterior (dorsal) and anterior (palmar) aspects of the medial carpals.

Proximal to the end of the ulna, there are three branches:

1. a branch to the posterior (dorsal) radiocarpal arch,
2. one to the anterior(palmar) radiocarpal arch,
3. and one to the proximal pole of the pisiform and to the anterior (palmar) aspect of the triquetrum.

Vascular Arches of the Hand

Posterior (dorsal) Arches:

The posterior (dorsal) arches are connected longitudinally at their medial and lateral aspects by the ulnar and radial arteries. They are connected centrally by the posterior (dorsal) branch of the anterior interosseous artery.

There are three posterior (dorsal) transverse arches: the radiocarpal, the intercarpal, and the basal metacarpal:

1. Posterior (dorsal) radiocarpal: The radiocarpal arch is supplied by branches of the radial and ulnar arteries and the posterior (dorsal) branch of the anterior interosseous artery.
2. Posterior (dorsal) intercarpal: The posterior (dorsal) intercarpal arch has a variable supply, which can include the radial, ulnar, and anterior interosseous arteries.
3. Basal metacarpal: The basal metacarpal arch is supplied by perforating arteries from the second, third, and fourth interosseous spaces. It contributes to the vascularity of the distal carpal row through anastomoses with the intercarpal arch.

Anterior (palmar) Arches:

Similar to the posterior (dorsal) vascularity, the anterior (palmar) vascularity is composed of three transverse arches: the anterior (palmar) radiocarpal, the anterior (palmar) intercarpal, and the deep anterior (palmar) arch:

1. Anterior (palmar) radiocarpal: This arch supplies the anterior (palmar) surface of the lunate and triquetrum.
2. Anterior (palmar) intercarpal: This arch is small and is not a major contributor of nutrient vessels to the carpals.
3. Deep anterior (palmar): This arch contributes to the radial and ulnar recurrent arteries and sends perforating branches to the posterior (dorsal) basal metacarpal arch and to the anterior (palmar) metacarpal arteries.

References

1. Bowers WH, Tribuzi SM: Functional Anatomy. In: Stanley BG, Tribuzi SM, eds. Concepts in Hand Rehabilitation. Philadelphia, PA: FA Davis, 1992:3–34.
2. Freedman DM, Botte MJ, Gelberman RH. Vascularity of the carpus. Clin Orthop Relat Res. 2001 Feb;(383):47-59. doi: 10.1097/00003086-200102000-00008. PMID: 11210969.
3. Nguyen JD, Duong H. Anatomy, Shoulder and Upper Limb, Hand Arteries. [Updated 2021 Sep 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK546583/
4. Dutton’s Orthopaedic Examination, Evaluation, And Intervention 3rd Edition.
5. Morton DA, Foreman KB, Albertine KH: The Big Picture: Gross Anatomy,McGraw-Hill, 2011.
6. Millers Review of Orthopaedics -7th Edition Book.