The Muscular Layer

Beneath the deep fascia lies the muscular layer, which is interspersed with the major neurovascular structures. An understanding of the various intermuscular intervals is critical to safely performing elbow surgery. A few muscles are of particular surgical importance to the elbow and are described in detail (Table 1.1). Hilton's law states that the motor nerve to a muscle that crosses a joint gives a branch to that joint and the skin over the joint.8

Triceps Brachii Muscle

The triceps brachii constitutes the entire musculature of the posterior compartment of the arm (Fig. 1.5). The long head of this muscle originates at the infraglenoid tuberos-ity of the scapula. The lateral head has a linear origin proximal and lateral to the spiral groove that separates it from the medial head. The medial head (or the deep head) is deep to the other two heads; it originates below and medial to the spiral groove and widens to include the adjacent intermuscular septa.8 Thus, each head takes origin distal to the other, with progressively larger areas of origin.

The long and lateral heads are superficial and blend in the midline to form a common superficial tendon that inserts into the posterior surface of the proximal olecranon and the adjacent deep fascia9 (Fig. 1.6). The deep medial head is fleshy and inserts mainly into the deep surface of the common tendon, with the remainder inserting into the olecranon and joint capsule.10 Insertion into the capsule prevents impingement of the capsule in the olecranon fossa. The triceps muscle does not insert into the proximal tip of the olecranon, but is separated by the sub-tendinous olecranon bursa.

Proximal to the spiral groove, the radial nerve provides muscular branches to the long and medial heads. Within the spiral groove, muscular branches supply the lateral and medial heads. This second branch to the medial head traverses it to supply the anconeus and is at risk of injury during some surgical approaches.11-13

The medial head is active in all phases of extension, while the long and lateral heads are minimally active except in resisted extension.13 An anomalous musculo-tendinous slip of the triceps can run through the groove behind the medial epicondyle in extension and snap forward in flexion to produce a "snapping triceps tendon."10 This condition can be confused with a snapping ulnar nerve.

Cephalic vein

Cephalic vein

Medial cutaneous nerve of the forearm

Median nerve-

Medial cutaneous nerve of the forearm

Lateral cutaneous nerve of „the arm

Median nerve-

Lateral cutaneous nerve of „the arm

Lateral cutaneous nerve of .the forearm

Superficial branch of the radial nerve

Lateral cutaneous nerve of .the forearm

Superficial branch of the radial nerve

Posterior cutaneous nerve of the forearm

Ulnar nerve

FIGURE 1.2. (A) Subcutaneous nerves and veins around the elbow. Anterior view. (B) Sensory nerve distribution pattern. Anterior view. (C) Sensory nerve distribution pattern. Posterior view.

Superior ulnar collateral artery

Medial ¡nterm uscular septum

Inferior ulnar collateral artery

Profunda brach ii artery

Radial nerve

Lateral intermuscular septum

Superior ulnar collateral artery

Inferior ulnar collateral artery

Profunda brach ii artery

Radial nerve

Lateral intermuscular septum

Recurrent posterior Interosseous artery

Recurrent posterior Interosseous artery

Posterior interosseous artery

FIGURE 1.3. Nerves and arteries of the elbow and forearm and their relationship to the medial and lateral intermuscular septa of the arm. (A) Anterior aspect. (B) Posterior aspect.

Anconeus Muscle

The anconeus (Fig. 1.7) is the small triangular muscle that covers the lateral aspect of the radiocapitellar joint and is a key landmark for surgical approaches to the elbow. It originates from a small depression on the posterior aspect of the lateral epicondyle8 and inserts into the lateral dorsal surface of the olecranon and proximal ulna. The second motor branch to the medial head of the triceps (C7, C8) enters the anconeus at its proximal border and innervates the muscle. The anconeus is active in elbow extension, ulnar abduction during pronation, and joint stabilization. This muscle has been used as a local flap for skin coverage over the elbow. We have also used this muscle as a muscular interposition for proximal ra-dioulnar synostosis.

Supinator Muscle

The supinator muscle lies deep to the anconeus muscle and the extensor muscle mass. This muscle is important surgically because of its close proximity to the posterior interosseous nerve.

The deep ulnar head of the supinator originates at the supinator crest and fossa of the ulna and wraps horizon-

FIGURE 1.4. Relationship of the muscles of the anterior aspect of the elbow to the biceps tendon, deep fascia, and bicipital aponeurosis.

TABLE 1.1. Muscles of the elbow

Muscle

Origin

Insertion

Nerve supply

Action

Posterior Triceps brachii Long head

Lateral head Medial head

Anconeus

Extensor carpi ulnaris

Extensor digitorum communis

Lateral

Extensor carpi radialis brevis Extensor carpi radialis longus Brachioradialis

Supinator

Medial

Flexor digitorum superficialis

Flexor digitorum profundus

Anterior Biceps brachii Long head

Short head

Pronator teres Humeral head Ulnar head Flexor carpi radialis Palmaris longus

Flexor carpi ulnaris Humeral head Ulnar head

Infraglenoid tuberosity of scapula Humerus above spiral groove Humerus below spiral groove Posterior lateral epicondyle

Lateral epicondyle and aponeurosis from subcutaneous border of ulna Anterolateral epicondyle

Inferolateral lateral epicondyle

Lateral supracondylar ridge

Lateral supracondylar ridge

Anterolateral lateral epicondyle, lateral collateral ligament, supinator crest of ulna

Medial epicondyle, ulnar collateral ligament, medial coronoid and proximal two-thirds of radius

Medial olecranon and proximal three-fourths of ulna

Supraglenoid tubercle of scapula

Coracoid process of scapula Anterosuperior medial epicondyle, coronoid process of ulna Anteroinferior aspect of medial epicondyle Medial epicondyle

Medial epicondyle Medial olecranon, proximal two-thirds of ulna and aponeurosis from subcutaneous border of ulna

Aponeurosis from long and lateral heads blend and insert into olecranon Aponeurosis and olecranon Dorsolateral proximal ulna

Fifth metacarpal

Extensor mechanism of each finger

Third metacarpal Second metacarpal Radial styloid

Proximal and middle third of radius

Middle phalanges of fingers

Distal phalanges of fingers

Tendon into bicipital tuberosity of radius Eponeurosis into forearm fascia and ulna Pronator tuberosity of radius

Second and third metacarpals Palmar aponeurosis Pisiform and fifth metacarpal

Radial nerve, C7-C8

Elbow extension

Motor branch to medial head of triceps, C7-C8 PIN, C6-C7

PIN, C7-C8

PIN, C6-C7

Radial nerve,

C6-C7 Radial nerve, C5-C6

PIN, C5-C6

Median nerve, C7-C8

Media nerve (index and middle fingers), ulnar nerve (ring and little fingers), C8-T1

Musculocutaneous nerve, C5-C6

Median nerve, C6-C7

Median nerve,

C6-C7 Median nerve, C7,

Elbow extension, abduction, and stabilization Wrist extension and ulnar deviation

Metacarpal phalangeal joint extension

Wrist extension

Wrist extension

Elbow flexion with forearm in neutral rotation Forearm supination

Flexion of PIP joints

Flexion of DIP joints

Elbow flexion, supination of flexed

Forearm pronation, weak elbow flexion

Wrist flexion and weak forearm pronation

Wrist flexion

Wrist flexion and ulnar deviation

PIN, posterior interosseous nerve.

FIGURE 1.5. Origins of the triceps muscle. Note that the medial head also originates from the medial and lateral intermuscular septum.

tally around the radius.8 The superficial humeral head originates from the distal border of the lateral epicondyle just anterior to the anconeus, the radial collateral ligament, and the proximal ulna just posterior to the supina-tor crest. The fibers slope downward and overlie the horizontal deep fibers. The arcade of Frohse is the proximal fibrous arch of the superficial head of the supinator muscle.14 It will be described in more detail when we describe the radial nerve. The muscle is rhomboid in shape. It proceeds distally, obliquely, and radially to wrap around and insert into the proximal and middle thirds of the radius between the anterior and posterior oblique lines.

The posterior interosseous nerve (C5, C6) innervates both heads of the supinator muscle and passes between them into the forearm to supply the extensor muscles of the wrist and digits. Retraction of this nerve when exposing the proximal radius is a common cause of iatro-genic nerve injury.

The supinator muscle assists the biceps muscle with supination of the forearm. The surgeon must be aware of the posterior interosseous nerve's presence in the muscle's substance while dissecting in its vicinity. When exposing the proximal radius, he or she should protect the posterior interosseous nerve by either stripping the supinator muscle subperiosteally from the radius (nerve within the muscle) or by dividing the superficial humeral head (nerve exposed). With pronation of the forearm, the proximal posterior interosseous nerve is translated approximately 1 cm anteromedially. This concept is important to remember when using lateral approaches to the elbow because pronation increases the zone of safety for the posterior interosseous nerve.15

Pronator Teres Muscle

The pronator teres muscle is the most proximal of the pronator flexor group and forms the medial border of the cubital fossa. The large humeral head arises from the medial supracondylar ridge and the anterosuperior aspect of the medial epicondyle. The small ulnar head arises from the coronoid process of the ulna and can be absent in 6% of individuals.16 Before it passes between them into the forearm, the median nerve (C6, C7) supplies a branch to each head. A fibrous arch connects the two heads and may entrap the median nerve that passes beneath it. The common muscle belly proceeds radially and distally under the brachioradialis and inserts into the middle third of the radius.

The pronator teres muscle is the primary pronator of the forearm and is a weak flexor of the elbow. It is an important surgical landmark and is the cause of entrapment of the proximal median nerve.

Cure Tennis Elbow Without Surgery

Cure Tennis Elbow Without Surgery

Everything you wanted to know about. How To Cure Tennis Elbow. Are you an athlete who suffers from tennis elbow? Contrary to popular opinion, most people who suffer from tennis elbow do not even play tennis. They get this condition, which is a torn tendon in the elbow, from the strain of using the same motions with the arm, repeatedly. If you have tennis elbow, you understand how the pain can disrupt your day.

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