Intrinsic Muscles of Hand – Origin, Nerve Supply, Function

Intrinsic Muscles of Hand/ The thenar muscles are three short muscles located at the base of the thumb. The muscle bellies produce a bulge, known as the thenar eminence. They are responsible for the fine movements of the thumb. The median nerve innervates all the thenar muscles.

Thenar Muscles of Hand

Opponents policies 

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

Abductor policies Brevis

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

Flexor policies Brevis 

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

Adductor Compartment

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)

References

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