Forearm Anatomy

Forearm Anatomy

 

distal to the tip

• Biceps brachii inserts at ulnar margin radial tuberosity (long head proximal, short head distal); powerful supinator of forearm

• Primary elbow extensor (triceps) inserts on olecranon process.

• Mobile wad: brachioradialis, extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB)

• Flexor-pronator mass: pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS)

   

  • Osteology

    • Ulna

       

    • Radius

 

• Proximally: two curved processes, the olecranon and the coronoid processes, with an intervening trochlear notch

• Distally, the ulna tapers and ends in a lateral head and a medial styloid process.

   

• Proximally: head with a central fovea, neck, and proximal medial radial tuberosity (for insertion of biceps tendon)

• Gradual bend (convex laterally) and increase in size distally

  • Restoration of the radial bow (and length) is critical in the fixation of radial shaft fractures to maintain arc of pronation and supination.

• Distally, the radius is composed of the carpal articular surface, an ulnar notch, a dorsal tubercle (Lister tubercle, which is at the level of the scapholunate joint), and a lateral styloid process.

• Arthrology: proximally includes the elbow joint and distally includes the wrist joint

  • Radius and ulna connected by oblique interosseous membrane/ligament (disrupted in Essex-Lopresti injury), which transmits axial load from radius at wrist to ulna at elbow

• Muscles ( Fig. 2.6, Table 2.6): arranged according to both location and function

  • Volar flexors (superficial and deep) (Fig. 2.7)

  • Dorsal extensors (superficial and deep) (see Fig. 2.7)

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    FIG. 2.6 Muscle attachments of the forearm (anterior and posterior views). From Drake RL et al, editors: Gray’s atlas of anatomy, ed 2, Philadelphia, 2015, Churchill Livingstone.

     

     

     

     

     

    FIG. 2.7 Volar flexors (superficial and deep).

    From Drake RL et al, editors: Gray’s atlas of anatomy, ed 2, Philadelphia, 2015, Churchill Livingstone.

     

    Muscles of Forearm

     

     

    Muscle	Origin	Insertion	Action	Innervation
    Superficial Flexors
    Pronator teres	Medial epicondyle and coronoid	Midlateral radius	Pronating, flexing forearm	Median nerve
    Flexor carpi radialis	Medial epicondyle	Second and third metacarpal bases	Flexing wrist	Median nerve
    Palmaris longus	Medial epicondyle	Palmar aponeurosis	Flexing wrist	Median nerve
    Flexor carpi ulnaris	Medial epicondyle and posterior ulna	Pisiform	Flexing wrist	Ulnar nerve
    Flexor digitorum superficialis	Medial epicondyle, proximal anterior ulna,	Base of middle phalanges	Flexing PIP joint	Median nerve

    	and anterior radius
    Deep Flexors
    Flexor digitorum profundus	Anterior and medial ulna	Base of distal phalanges	Flexing DIP joint	Median–anterior interosseous/ulnar nerves
    Flexor pollicis longus	Anterior and lateral radius	Base of distal phalanges	Flexing IP joint, thumb	Median–anterior interosseous nerve
    Pronator quadratus	Distal ulna	Volar radius	Pronating hand	Median–anterior interosseous nerve
    Superficial Extensors
    Brachioradialis	Lateral supracondylar humerus	Lateral distal radius	Flexing forearm	Radial nerve
    Extensor carpi radialis longus	Lateral supracondylar humerus	Second metacarpal base	Extending wrist	Radial nerve
    Extensor carpi radialis brevis	Lateral epicondyle of humerus	Third metacarpal base	Extending wrist	Radial nerve
    Anconeus	Lateral epicondyle of humerus	Proximal dorsal ulna	Extending forearm	Radial nerve
    Extensor digitorum	Lateral epicondyle of humerus	Extensor aponeurosis	Extending digits	Radial–posterior interosseous nerve
    Extensor digiti minimi	Common extensor tendon	Small finger extensor expansion over proximal phalanx	Extending small finger	Radial–posterior interosseous nerve
    Extensor carpi ulnaris	Lateral epicondyle of humerus	Fifth metacarpal base	Extending/adducting hand	Radial–posterior interosseous nerve
    Deep Extensors
    Supinator	Lateral epicondyle of humerus, ulna	Dorsolateral radius	Supinating forearm	Radial–posterior interosseous nerve
    Abductor	Dorsal	First	Abducting/extending	Radial–posterior

    pollicis longus	ulna/radius	metacarpal base	thumb	interosseous nerve
    Extensor pollicis brevis	Dorsal radius	Thumb proximal phalanx base	Extending thumb MCP joint	Radial–posterior interosseous nerve
    Extensor pollicis longus	Dorsolateral ulna	Thumb dorsal phalanx base	Extending thumb IP joint	Radial–posterior interosseous nerve
    Extensor indicis proprius	Dorsolateral ulna	Index finger extensor apparatus (ulnarly)	Extending index finger	Radial–posterior interosseous nerve

  • Table 2.6