Intrinsic Muscles of Hand – Origin, Nerve Supply, Function

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.

Intrinsic Muscles of Hand

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

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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
  • 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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