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Extensors of Arm – Muscle Attachment, Function

Extensors of Arm is a group of muscles performs flexion and pronation at the wrist and flexion of the. In general, muscles in the anterior compartment of the forearm perform flexion at the flexor carpi ulnaris, palmaris longus, flexor carpi radialis, and pronator teres the medial epicondyle, and the other from the coronoid process of the ulna.

Muscles of Anterior Compartment of Forearm (Flexors of Forearm)

Superficial layer

Pronator teres

Function: Pronation of radio-ulnar joint
Origin: Coronoid process and medial epicondyle of humerus
Insertion: Lateral surface of the radius
Innervation: Median nerve (C6, C7)

Flexor carpi radialis

Function: Flexion and adduction at the wrist
Origin: Medial epicondyle of humerus
Insertion: Base of second metacarpal
Innervation: Median nerve (C6, C7)

Palmaris longus

Function: Flexion at the wrist, tensing of the palmar aponeurosis
Origin: Medial epicondyle of humerus
Insertion: Flexor retinaculum
Innervation: Median nerve (C7, C8)

Flexor carpi ulnaris

Function: Flexion and adduction at the wrist
Origin: Medial epicondyle of humerus and olecranon
Insertion: Pisiform, hook of hamate and fifth metacarpal
Innervation: Median nerve (C7, C8)

Intermediate Layer

Flexor digitorum superficialis

Function: Flexion of the proximal interphalangeal joint of the second, third, fourth, and fifth finger. Also has a weaker flexion action on the metacarpophalangeal joints of the same fingers
Origin: Medial epicondyle, coronoid process, and anterior radius
Insertion: Second, third, fourth, and fifth middle phalanges
Innervation: Median nerve (C7, C8, T1)

Deep Layer

Flexor digitorum profundus

Function: Flexion of the distal interphalangeal joint of the second, third, fourth, and fifth finger
Origin: Medial and the anterior surface of the proximal ulna and interosseous membrane
Insertion: Second, third, fourth, and fifth distal phalanges
Innervation: Ulnar nerve (C8, T1) for the medial part, anterior interosseous nerve (C8,T1) for the lateral

Flexor pollicis longus

Function: Flexion of the interphalangeal joint of the thumb
Origin: Anterior aspect of radius as well as interosseous membrane
Insertion: Base of distal phalanx of thumb
Innervation: Anterior interosseous nerve (C7, C8)

Pronator quadratus

Function: Pronator of the forearm
Origin: Anterior aspect of distal ulna
Insertion: Anterior aspect of the distal radius
Innervation: Anterior interosseous nerve (C7, C8)

Brachioradialis

Function: Weak flexor of the forearm
Origin: Proximal supracondylar ridge on the humerus
Insertion: Lateral surface of the distal end of radius
Innervation: Radial nerve (C5, C6, C7)

Muscles of Posterior Compartment of Forearm

Superficial

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Extensor carpi radialis longus

Function: Extension and abduction of the wrist
Origin: Proximal supracondylar ridge on the humerus
Insertion: Dorsal base of the second metacarpal
Innervation: Radial nerve (C6, C7)

Extensor carpi radialis brevis

Function: Extension and abduction of the wrist
Origin: Lateral epicondyle of humerus
Insertion: Dorsal base of the third metacarpal
Innervation: Deep branch of the radial nerve (C7, C8)

Extensor digitorum

Function: Extension of the proximal interphalangeal joint of the second, third, fourth, and fifth fingers. Also has a weaker extension action on the metacarpophalangeal joints of the same fingers
Origin: Lateral epicondyle of humerus
Insertion: Extensor expansions on the dorsal aspect of second, third, fourth, and fifth middle and distal phalanges
Innervation: Posterior interosseous nerve (C7, C8)

Extensor digit minimi

Function: Extension of the little finger at the metacarpophalangeal joint and interphalangeal joint
Origin: Lateral epicondyle of humerus
Insertion: Extensor expansion on the dorsal aspect of fifth phalanx
Innervation: Posterior interosseous nerve (C7, C8)

Extensor carpi ulnaris

Function: Extension and adduction of the wrist
Origin: Lateral epicondyle of the humerus and posterior ulna
Insertion: Fifth metacarpal base
Innervation: Posterior interosseous nerve (C7, C8)

Deep Layer

Extensor indices

Function: Extension of the index finger
Origin: Dorsal surface of distal ulna and interosseous membrane
Insertion: Extensor expansion of second finger
Innervation: Posterior interosseous nerve (C7, C8)

Supinator

Function: Supination of the forearm
Origin: Lateral epicondyle and supinator crest of ulna
Insertion: Lateral surface of radius
Innervation: Deep branch of radial nerve (C7, C8)

Abductor policies longus

Function: Abduction of the thumb by acting on the carpometacarpal joint and the metacarpophalangeal joint
Origin: Dorsal aspects of the proximal radius, ulna, and interosseous membrane
Insertion: Base of the first metacarpal
Innervation: Posterior interosseous nerve (C7, C8)

Extensor pollicus longus

Function: Extension of the thumb by acting on the carpometacarpal joint, the metacarpophalangeal joint, and the interphalangeal joint.
Origin: Dorsal aspects of the middle ulna and interosseous membrane
Insertion: Distal phalanx of 1st finger
Innervation: Posterior interosseous nerve (C7, C8)

Extensor pollicus brevis

Function: Extension of the thumb by acting on the carpometacarpal joint and the metacarpophalangeal joint
Origin: Dorsal aspects of middle radius and interosseous membrane
Insertion: Distal phalanx of 1st finger
innervation: Posterior interosseous nerve (C7, C8)

Intrinsic Muscles of Hand

Thenar muscles

Opponents policies

Function: Opposition of the thumb
Origin: Flexor retinaculum and tubercle of trapezium
Insertion: Lateral aspect of first metacarpal
Innervation: Recurrent branch of median nerve (C8, T1)

Abductor policies Brevis

Function: Abduction of the thumb at the metacarpophalangeal joint
Origin: Flexor retinaculum and tubercle of scaphoid
Insertion: Lateral aspect of proximal phalanx of first finger
Innervation: Recurrent branch of median nerve (C8, T1)

Flexor pollicus brevis

Function: Flexion of the thumb at the metacarpophalangeal joint
Origin: Flexor retinaculum and tubercle of trapezium
Insertion: Lateral aspect of proximal phalanx of first finger
Innervation: Recurrent branch of median nerve (C8, T1)

Adductor Compartment

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Adductor pollicus

Function: Adduction of the thumb
Origin: Second, third metacarpal, and capitate
Insertion: Proximal phalanx and extensor expansion of 1st finger
Innervation: Deep branch of ulnar nerve (C8, T1)

Hypothenar Muscles

Abductor digiti minimi

Function: Abduction of the little finger at the metacarpophalangeal joint
Origin: Pisiform
Insertion: Medial aspect of proximal phalanx of fifth finger
Innervation: Deep branch of ulnar nerve (C8, T1)

Flexor digiti minimi brevis

Function: Flexion of the little finger at the metacarpophalangeal joint
Origin: Flexor retinaculum and hook of hamate
Insertion: Medial aspect of proximal phalanx of fifth finger
Innervation: Deep branch of ulnar nerve (C8, T1)

Opponens digiti minimi

Function: Opposition of the little finger
Origin: Flexor retinaculum and hook of hamate
Insertion: Medial aspect of fifth metacarpal
Innervation: Deep branch of ulnar nerve (C8, T1)

Short Muscles

Lubricants

Function: Flexion of the metacarpophalangeal joints with extension of the interphalangeal joints
Origin: Arise from tendons of flexor digitorum profundus. First 2 are unipennate, and the third and fourth are bipennate
Insertion: Extensor expansions of second, third, fourth, and fifth finger
Innervation: Median nerve (C8, T1) for the lateral 2 lumbricals, deep branch of ulnar nerve (C8, T1) for the medial 2 lumbricals

Dorsal interossei

Function: Abduction of the second, third, and fourth finger away from the axial line
Origin: Adjacent metacarpals
Insertion: Extensor expansions and proximal phalanges of the second, third, and fourth fingers
Innervation: Deep branch of ulnar nerve (C8, T1)

Palmar interossei

Function: Adduction of the second, third, and fourth finger towards the axial line
Origin: Palmar surfaces of second, fourth, and fifth metacarpals
Insertion: Extensor expansions and proximal phalanges of the second, fourth, and fifth fingers
Innervation: Deep branch of ulnar nerve (C8, T1)

Surgical Considerations

The deltoid is a significant factor when considering the anterior surgical approach to gain access to the shoulder joint. Some of these technical procedures include, but are not limited to the following:

Open Bankart repair/capsular reconstructions – indicated in the setting of recurrent anterior (or other directional) instability of the shoulder
Shoulder arthroplasty – indicated for cases of post-traumatic deformity, advanced degenerative arthritis, and/or avascular necrosis includes hemiarthroplasty, total shoulder arthroplasty (TSA), reverse total shoulder arthroplasty (TSA)
The long head of the biceps tendon (LHBT) – repair versus tenotomy versus tenodesis procedures indicated in the setting of either LHBT/bicipital groove instability or advanced/end-stage LHBT tendinopathy and degeneration[rx][rx]
Rotator cuff repair contemporary – indications remain somewhat controversial although most of these procedures are now being performed arthroscopically popular approaches (as opposed to the deltopectoral approach) include the mini-open approach (lateral deltoid-splitting approach)