Elbow and Forearm


Chapter 3

Elbow and Forearm



A. Bobby Chhabra, Aaron M. Freilich



Regional Anatomy and Surgical Intervals



Regional Anatomy


Osteology (Figs. 3-1 and 3-2)


Distal Humerus








Arthrology (Fig. 3-3)


Elbow Joint











Muscles (Figs. 3-4 and 3-5)






Table 3-1


Compartments and Muscles of the Elbow





































































































































































COMPARTMENT MUSCLE ORIGIN INSERTION INNERVATION FUNCTION
Anterior arm Biceps brachii Long head—supraglenoid tubercle Radial tuberosity Musculocutaneous nerve Supination of forearm; flexion of elbow


Short head—coracoid process


Brachialis Distal half of anterior humerus Ulnar tuberosity Musculocutaneous nerve Flexion of elbow in pronation
Posterior arm Triceps brachii Long head—infraglenoid tubercle Olecranon process Radial nerve Extension of elbow


Lateral head—proximal lateral half of humerus



Medial head—posterior humerus

Superficial forearm flexors Pronator teres Medial epicondyle and ulna coronoid process Lateral middle surface of radius Median nerve Forearm pronation

Flexor carpi radialis Medial epicondyle Base of second and third MC Median nerve Flexion of wrist

Palmaris longus Medial epicondyle Palmar fascia Median nerve Weak flexion of wrist

Flexor carpi ulnaris Medial epicondyle and proximal posterior shaft and olecranon process of ulna Fifth MC, pisiform, and hamate Ulnar nerve Wrist flexion and ulnar deviation

Flexor digitorum superficialis Medial epicondyle, ulna coronoid process, and anterior oblique line of radius Splits at level of proximal phalanx and inserts onto volar middle phalanx Median nerve Finger flexion at PIP joints
Deep forearm flexors Flexor digitorum profundus Proximal interosseous membrane and anterior ulna Volar aspect of distal phalanges Lateral half—AINMedial half—ulnar nerve Finger flexion at DIP joints

Flexor pollicis longus Anterior shaft of radius and interosseous membrane Volar aspect of thumb distal phalanx AIN Flexion of thumb IP joint

Pronator quadratus Distal anterior ulna Distal anterior radius AIN Forearm pronation
Superficial forearm extensors Brachioradialis Lateral supracondylar ridge Radial styloid process Radial nerve Flexion of elbow
Extensor carpi radialis longus Lateral supracondylar ridge of humerus and lateral epicondyle Dorsal base of second MC Radial nerve Wrist extension and some radial deviation

Extensor carpi radialis brevis Lateral epicondyle Dorsal base of third MC PIN/radial nerve Wrist extension and some radial deviation

Extensor digitorum Lateral epicondyle Extensor hood of digits 2-5 PIN Finger extension

Extensor digiti minimi Lateral epicondyle Extensor hood of fifth digit PIN Fifth finger extension

Extensor carpi ulnaris Lateral epicondyle Dorsal fifth MC PIN Wrist extension and ulnar deviation; stabilizes wrist in grip

Anconeus Posterior lateral epicondyle Lateral olecranon process and posterior ulna shaft Radial nerve Weakly extends elbow
Deep forearm extensors Supinator Lateral epicondyle and proximal ulna Proximal lateral radius PIN Forearm supination

Abductor pollicis longus Posterior ulna shaft and interosseous membrane Dorsal base of first MC and trapezium PIN Thumb abduction

Extensor pollicis brevis Posterior radial shaft and interosseous membrane Dorsal proximal phalanx of thumb PIN Extends thumb at MC joint

Extensor pollicis longus Posterior ulnar shaft and interosseous membrane Dorsal distal phalanx of thumb PIN Extends thumb at IP joint

Extensor indicis Posterior ulnar shaft and interosseous membrane Ulnar side of extensor digitorum communis tendon to second digit at level of MCP joint PIN Assists in extension of second digit


image


AIN, Anterior interosseous nerve; DIP, distal interphalangeal; IP, interphalangeal; MC, metacarpal; MCP, metacarpophalangeal; PIN, posterior interosseous nerve; PIP, proximal interphalangeal.



Nerves (Figs. 3-6 and 3-7)


Musculocutaneous Nerve C5, C6, C7






Radial Nerve C5, C6, C7, C8 (T1)



Travels in the radial groove on the posterior middle third of the humerus, then enters the lateral intramuscular septum between the medial and lateral heads of the triceps


Emerges from the intramuscular septum between the brachialis and brachioradialis muscles and approaches the elbow anterolaterally between the brachialis and ECRL


Anterior to the lateral epicondyle it branches into


• The superficial sensory branch


• In the proximal forearm, the nerve lies superficial to the supinator muscle and continues into the lateral middle forearm deep to the brachioradialis


• Approximately 9 cm proximal to the wrist, the nerve emerges through the antebrachial fascia between the brachioradialis tendon and ECRL tendons and superficially crosses the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) muscles as it descends to the hand


• Provides sensation to the posterior aspect of the thumb, index finger, and middle finger


• Deep motor branch or posterior interosseous nerve (PIN)


• Provides motor innervation to the forearm extensor muscles


• After bifurcating from the radial nerve, the PIN turns toward the posterior forearm and gives off three short branches to the ECRL, extensor carpi radialis brevis (ECRB), and extensor carpi ulnaris (ECU) muscles, then pierces the proximal supinator muscle


• After traveling within supinator fibers, the PIN exits the distal end of the supinator and continues distally in the forearm deep to the extensor digitorum communis (EDC) and extensor digiti minimi muscle bellies; the nerve continues to give off multiple branches to the APL, EPB, extensor pollicis longus, and extensor indicis proprius


• The terminal portion of the nerve dives between the extensor pollicis longus and the EPB to the interosseous membrane, where it descends to the wrist and provides innervation to the wrist capsule





Surgical Intervals




Vascular (Fig. 3-12)


Brachial Artery



Approaches the anterior elbow on the medial side of the biceps brachii muscle; the median nerve lies medial to the artery


The artery branches at approximately the level of the radial neck


• Radial artery


• Passes under the bicipital aponeurosis


• Gives off the radial recurrent artery as the first branch


• Continues into the forearm under the brachioradialis muscle belly and emerges between the brachioradialis and FCR tendons before entering the wrist and hand


• Ulnar artery


• Larger of the two branches


• Gives off the ulnar anterior or posterior recurrent artery, or both, as the first branch


• Continues into the forearm with the ulnar nerve between the FDS and FDP muscle bellies and emerges in the distal forearm between the FDS and FCU tendons before entering the wrist and hand


• The common interosseous artery branches at a level just distal to the radial tuberosity, then divides into


• The anterior interosseous artery: lies anterior to the interosseous membrane between the FDP and FPL in the forearm; travels with the anterior interosseous nerve


• The posterior interosseous artery: passes to the posterior arm between the oblique cord and the proximal border of the interosseous membrane and emerges from under the inferior border of the supinator and continues down the posterior forearm, supplying the superficial extensor muscles; travels with the PIN


• The anterior and posterior interosseous arteries reanastomose at the distal end of the interosseous membrane






Palpable Anatomic Landmarks for Surgical Incisions and Approaches (Fig. 3-14)


Hazards


Nerves


Radial Nerve









Surgical Approaches to the Elbow



Anterior Approach to the Elbow (Antecubital Fossa)


Indications





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Jun 7, 2016 | Posted by in ORTHOPEDIC | Comments Off on Elbow and Forearm

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