Flexor and Extensor Retinacula-Flexor Retinaculum-Extensor Retinaculum-Carpal Tunnel-Absent Palmaris Longus-Contents of the Anterior Fascial Compartment of the Forearm-

Flexor and Extensor Retinacula

The flexor and extensor retinacula are strong bands of deep fascia that hold the long flexor and extensor tendons in position at the wrist.

Flexor Retinaculum

The flexor retinaculum is a thickening of deep fascia that holds the long flexor tendons in position at the wrist. It stretches across the front of the wrist and converts the concave anterior surface of the hand into an osteofascial tunnel, the carpal tunnel, for the passage of the median nerve and the flexor tendons of the thumb and fingers.

It is attached medially to the pisiform bone and the hook of the hamate and laterally to the tubercle of the scaphoid and the trapezium bones. The attachment to the trapezium consists of superficial and deep parts and forms a synoviallined tunnel for passage of the tendon of the flexor carpi radialis.

The upper border of the retinaculum corresponds to the distal transverse skin crease in front of the wrist and is continuous with the deep fascia of the forearm. The lower border is attached to the palmar aponeurosis

Extensor Retinaculum

The extensor retinaculum is a thickening of deep fascia that stretches across the back of the wrist and holds the long extensor tendons in position. It converts the grooves on the posterior surface of the distal ends of the radius and ulna into six separate tunnels for the passage of the long extensor tendons. Each tunnel is lined with a synovial sheath, which extends above and below the retinaculum on the tendons. The tunnels are separated from one another by fibrous septa that pass from the deep surface of the retinaculum to the bones.

The retinaculum is attached medially to the pisiform bone and the hook of the hamate and laterally to the distal end of the radius.



The upper and lower borders of the retinaculum are continuous with the deep fascia of the forearm and hand, respectively.

Carpal Tunnel

The bones of the hand and the flexor retinaculum form the carpal tunnel. The median nerve lies in a restricted space between the tendons of the flexor digitorum superficialis and the flexor carpi radialis muscles.

Absent Palmaris Longus

The palmaris longus muscle may be absent on one or both sides of the forearm in about 10% of persons. Others show variation in form, such as centrally or distally placed muscle belly in the place of a proximal one. Because the muscle is relatively weak, its absence produces no disability.

Contents of the Anterior Fascial Compartment of the Forearm

■■ Muscles: A superficial group, consisting of the pronator teres, the flexor carpi radialis, the palmaris longus, and the flexor carpi ulnaris; an intermediate group consisting of the flexor digitorum superficialis; and a deep group consisting of the flexor pollicis longus, the flexor digitorum profundus, and the pronator quadratus

■■ Blood supply to the muscles: Ulnar and radial arteries

■■ Nerve supply to the muscles: All the muscles are supplied by the median nerve and its branches, except the flexor carpi ulnaris and the medial part of the flexor digitorum profundus, which are supplied by the ulnar nerve.

The Cubital Fossa-Boundaries-Contents-

The Cubital Fossa

The cubital fossa is a triangular depression that lies in front of the elbow.

Boundaries

■■ Laterally: The brachioradialis muscle

■■ Medially: The pronator teres muscle

The base of the triangle is formed by an imaginary line drawn between the two epicondyles of the humerus.

The floor of the fossa is formed by the supinator muscle laterally and the brachialis muscle medially. The roof is formed by skin and fascia and is reinforced by the bicipital aponeurosis.

Contents

The cubital fossa contains the following structures, enumerated from the medial to the lateral side: the median nerve, the bifurcation of the brachial artery into the ulnar and radial arteries, the tendon of the biceps muscle, and the radial nerve and its deep branch.

The supratrochlear lymph node lies in the superficial fascia over the upper part of the fossa, above the trochlea. It receives afferent lymph vessels from the third, fourth, and fifth fingers; the medial part of the hand; and the medial side of the forearm. The efferent lymph vessels pass up to the axilla and enter the lateral axillary group of nodes.

 

Fascial Compartments of the Upper Arm-Contents of the Anterior Fascial Compartment of the Upper Arm-Muscles of the Anterior Fascial Compartment-Lymphangitis-Lymphadenitis-Biceps Brachii and Osteoarthritis of the Shoulder Joint-

Fascial Compartments of the Upper Arm

The upper arm is enclosed in a sheath of deep fascia. Two fascial septa, one on the medial side and one on the lateral side, extend from this sheath and are attached to the medial and lateral supracondylar ridges of the humerus, respectively. By this means, the upper arm is divided into an anterior and a posterior fascial compartment, each having its muscles, nerves, and arteries.

Contents of the Anterior Fascial Compartment of the Upper Arm

■■ Muscles: Biceps brachii, coracobrachialis, and brachialis

■■ Blood supply: Brachial artery

■■ Nerve supply to the muscles: Musculocutaneous nerve

■■ Structures passing through the compartment: Musculocutaneous, median, and ulnar nerves; brachial artery and basilic vein. The radial nerve is present in the lower part of the compartment.

Muscles of the Anterior Fascial Compartment

The muscles of the anterior fascial compartment ,Note that the biceps brachii is a powerful supinator, and this action is made use of in twisting the corkscrew into the cork or driving the screw into wood with a screwdriver. The biceps also is a powerful flexor of the elbow joint and a weak flexor of the shoulder joint.

 

Lymphangitis

Infection of the lymph vessels (lymphangitis) of the arm is common. Red streaks along the course of the lymph vessels are characteristic of the condition. The lymph vessels from the thumb and index finger and the lateral part of the hand follow the cephalic vein to the infraclavicular group of axillary nodes; those from the middle, ring, and little fingers and from the medial part of the hand follow the basilic vein to the supratrochlear node, which lies in the superficial fascia just above the medial epicondyle of the humerus, and thence to the lateral group of axillary nodes.

Lymphadenitis

Once the infection reaches the lymph nodes, they become enlarged and tender, a condition known as lymphadenitis.

Most of the lymph vessels from the fingers and palm pass to the dorsum of the hand before passing up into the forearm. This explains the frequency of inflammatory edema, or even abscess formation, which may occur on the dorsum of the hand after infection of the fingers or palm.

Biceps Brachii and Osteoarthritis of the Shoulder Joint

The tendon of the long head of biceps is attached to the supraglenoid tubercle within the shoulder joint. Advanced osteoarthritic changes in the joint can lead to erosion and fraying of the tendon by osteophytic outgrowths, and rupture of the tendon can occur.

The Axilla-Walls of the Axilla-Contents of the Axilla-Key Muscles in the Axilla-Pectoralis Minor-Clavipectoral Fascia-Absent Pectoralis Major-

The Axilla

The axilla, or armpit, is a pyramid-shaped space between the upper part of the arm and the side of the chest. It forms an important passage for nerves, blood, and lymph vessels as they travel from the root of the neck to the upper limb. The upper end of the axilla, or apex, is directed into the root of the neck and is bounded in front by the clavicle, behind by the upper border of the scapula, and medially by the outer border of the first rib. The lower end, or base, is bounded in front by the anterior axillary fold (formed by the lower border of the pectoralis major muscle), behind by the posterior axillary fold (formed by the tendon of latissimus dorsi and the teres major muscle), and medially by the chest wall

Walls of the Axilla

The walls of the axilla are made up as follows:

■■ Anterior wall: By the pectoralis major, subclavius, and pectoralis minor muscles
■■ Posterior wall: By the subscapularis, latissimus dorsi, and teres major muscles from above down

■■ Medial wall: By the upper four or five ribs and the intercostal spaces covered by the serratus anterior muscle

■■ Lateral wall: By the coracobrachialis and biceps muscles in the bicipital groove of the humerus
The base is formed by the skin stretching between the anterior and posterior walls.

Contents of the Axilla

The axilla contains the axillary artery and its branches, which supply blood to the upper limb; the axillary vein and its tributaries, which drain blood from the upper limb; and lymph vessels and lymph nodes, which drain lymph from the upper limb and the breast and from the skin of the trunk, down as far as the level of the umbilicus. Lying among these structures in the axilla is an important nerve plexus, the brachial plexus, which innervates the upper limb. These structures are embedded in fat.

Key Muscles in the Axilla

Pectoralis Minor

The pectoralis minor is a thin triangular muscle that lies beneath the pectoralis major. It arises from the3rd, 4th, and 5th ribs and runs upward and laterally to be inserted by its apex into the coracoid process of the scapula. It crosses the axillary artery and the brachial plexus of nerves. It is used when describing the axillary artery to divide it into three parts
.

Clavipectoral Fascia

The clavipectoral fascia is a strong sheet of connective tissue that is attached above to the clavicle. Below, it splits to enclose the pectoralis minor muscle and then continues downward as the suspensory ligament of the axilla and joins the fascial floor of the armpit.

Absent Pectoralis Major

Occasionally, parts of the pectoralis major muscle may be absent. The sternocostal origin is the most commonly missing part, and this causes weakness in adduction and medial rotation of the shoulder joint.