The Wrist and Hand-Important Structures Lying in Front of the Wrist-Radial Artery-Tendon of Flexor Carpi Radialis-Tendon of Palmaris Longus (If Present)-Tendons of Flexor Digitorum Superficialis-Tendon of Flexor Carpi Ulnaris-Ulnar Artery-Ulnar Nerve-Important Structures Lying on the Lateral Side of the Wrist-Anatomic Snuffbox-Important Structures Lying on the Back of the Wrist-Lunate-Important Structures Lying in the Palm-Recurrent Branch of the Median Nerve-Superficial Palmar Arterial Arch-Important Structures Lying on the Dorsum of the Hand

The Wrist and Hand

At the wrist, the styloid processes of the radius and ulna can be palpated. The styloid process of the radius lies about 0.75 in. (1.9 cm) distal to that of the ulna.

The dorsal tubercle of the radius is palpable on the posterior surface of the distal end of the radius.

The head of the ulna is most easily felt with the forearm pronated; the head then stands out prominently on the lateral side of the wrist. The rounded head can be distinguished from the more distal pointed styloid process.

The pisiform bone can be felt on the medial side of the anterior aspect of the wrist between the two transverse creases. The hook of the hamate bone can be felt on deep palpation of the hypothenar eminence, a fingerbreadth distal and lateral to the pisiform bone.

The transverse creases seen in front of the wrist are important landmarks. The proximal transverse crease lies at the level of the wrist joint. The distal transverse crease corresponds to the proximal border of the flexor retinaculum.

Important Structures Lying in Front of the Wrist

Radial Artery

The pulsations of the radial artery can easily be felt anterior to the distal third of the radius. Here, it lies just beneath the skin and fascia lateral to the tendon of flexor carpi radialis muscle

Tendon of Flexor Carpi Radialis
The tendon of the flexor carpi radialis lies medial to the pulsating radial artery
.

Tendon of Palmaris Longus (If Present)

The tendon of the palmaris longus lies medial to the tendon of flexor carpi radialis and overlies the median nerve

Tendons of Flexor Digitorum Superficialis

The tendons of the flexor digitorum superficialis are a group of four that lie medial to the tendon of palmaris longus and can be seen moving beneath the skin when the fingers are flexed and extended.

 

Tendon of Flexor Carpi Ulnaris

The tendon of the flexor carpi ulnaris is the most medially placed tendon on the front of the wrist and can be followed distally to its insertion on the pisiform bone. The tendon can be made prominent by asking the patient to clench the fist (the muscle contracts to assist in fixing and stabilizing the wrist joint)
.

Ulnar Artery

The pulsations of the ulnar artery can be felt lateral to the tendon of flexor carpi ulnaris

Ulnar Nerve

The ulnar nerve lies immediately medial to the ulnar artery

Important Structures Lying on the Lateral Side of the Wrist

Anatomic Snuffbox

The “anatomic snuffbox” is an important area. It is a skin depression that lies distal to the styloid process of the radius. It is bounded medially by the tendon of extensor pollicis longus and laterally by the tendons of abductor pollicis longus and extensor pollicis brevis. In its floor can be palpated the styloid process of the radius (proximally) and the base of the first metacarpal bone of the thumb (distally); between these bones beneath the floor lie the scaphoid and the trapezium (felt but not identifiable).

The radial artery can be palpated within the snuffbox as the artery winds around the lateral margin of the wrist to reach the dorsum of the hand. The cephalic vein can also sometimes be recognized crossing the snuffbox as it ascends the forearm.

Important Structures Lying on the Back of the Wrist

Lunate

The lunate lies in the proximal row of carpal bones. It can be palpated just distal to the dorsal tubercle of the radius when the wrist joint is flexed.

Important Structures Lying in the Palm

Recurrent Branch of the Median Nerve

The recurrent branch to the muscles of the thenar eminence curves around the lower border of the flexor retinaculum and lies about one fingerbreadth distal to the tubercle of the scaphoid

Superficial Palmar Arterial Arch

The superficial palmar arterial arch is located in the central part of the palm and lies on a line drawn across the palm at the level of the distal border of the fully extended thumb

Deep Palmar Arterial Arch

The deep palmar arterial arch is also located in the central part of the palm and lies on a line drawn across the palm at the level of the proximal border of the fully extended thumb

Metacarpophalangeal Joints

The metacarpophalangeal joints lie approximately at the level of the distal transverse palmar crease. The interphalangeal joints lie at the level of the middle and distal finger creases.

Important Structures Lying on the Dorsum of the Hand

The tendons of extensor digitorum, the extensor indicis, and the extensor digiti minimi can be seen and felt as they pass distally to the bases of the fingers.

Synovial Flexor Sheaths-Tenosynovitis of the Synovial Sheaths of the Flexor Tendons-Trigger Finger-

Synovial Flexor Sheaths

In the hand, the tendons of the flexor digitorum superficialis and profundus muscles invaginate a common synovial sheath from the lateral side. The medial part of this common sheath extends distally without interruption on the tendons of the little finger. The lateral part of the sheath stops abruptly on the middle of the palm, and the distal ends of the long flexor tendons of the index, the middle, and the ring fingers acquire digital synovial sheaths as they enter the fingers. The flexor pollicis longus tendon has its own synovial sheath that passes into the thumb. These sheaths allow the long tendons to move smoothly, with a minimum of friction, beneath the flexor retinaculum and the fibrous flexor sheaths.

The synovial sheath of the flexor pollicis longus(sometimes referred to as the radial bursa) communicates with the common synovial sheath of the superficialis and profundus tendons (sometimes referred to as the ulnar bursa) at the level of the wrist in about 50% of subjects.

The vincula longa and brevia are small vascular folds of synovial membrane that connect the tendons to the anterior surface of the phalanges. They resemble a mesentery and convey blood vessels to the tendons.

Tenosynovitis of the Synovial Sheaths of the Flexor Tendons

Tenosynovitis is an infection of a synovial sheath. It most commonly results from the introduction of bacteria into a sheath through a small penetrating wound, such as that made by the point of a needle or thorn. Rarely, the sheath may become infected by extension of a pulp-space infection. Infection of a digital sheath results in distention of the sheath with pus; the finger is held semiflexed and is swollen. Any attempt to extend the finger is accompanied by extreme pain because the distended sheath is stretched. As the inflammatory process continues, the pressure within the sheath rises and may compress the blood supply to the tendons that travel in the vincula longa and brevia. Rupture or later severe scarring of the tendons may follow.

A further increase in pressure can cause the sheath to rupture at its proximal end. Anatomically, the digital sheath of the index finger is related to the thenar space, whereas that of the ring finger is related to the midpalmar space. The sheath for the middle finger is related to both the thenar and midpalmar spaces.

These relationships explain how infection can extend from the digital synovial sheaths and involve the palmar fascial spaces.

In the case of infection of the digital sheaths of the little finger and thumb, the ulnar and radial bursae are quickly involved.

Should such an infection be neglected, pus may burst through the proximal ends of these bursae and enter the fascial space of the forearm between the flexor digitorum profundus anteriorly and the pronator quadratus and the interosseous membrane posteriorly. This fascial space in the forearm is commonly referred to clinically as the space of Parona.

Trigger Finger

In trigger finger, there is a palpable and even audible snapping when a patient is asked to flex and extend the fingers.

It is caused by the presence of a localized swelling of one of the long flexor tendons that catches on a narrowing of the fibrous flexor sheath anterior to the metacarpophalangeal joint. It may take place either in flexion or in extension. A similar condition occurring in the thumb is called trigger thumb.

The situation can be relieved surgically by incising the fibrous flexor sheath.