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BASIC ANATOMY OF HAND

Hand consists of 27 bones

• 14 phalangeal bones

• 5 metacarpal bones

• 8 carpal bones

8 carpal bone (Lateral to medial)

• First row

• Scaphoid

• Lunate

• Triqueteral

• Pisiform

• Second row

  • Trapezium

  • Trapezoid

  • Capitate

  • Hamate

Intrinsic Muscles of Hand

• These are muscles originating from the hand and insertion within the hands.

• They include thenar muscles, hypothenar emineces, adductor pollicis, interossei, lumbricals.

Thenar Muscles

• It includes abductor pollicis brevis, opponens pollicis brevis, flexor pollicis brevis.

• They originate from flexor retinaculum and carpal bone and insert at the base of first metacarpal and first proximal phalanx.

• Supplied by median nerve.

Hypothenar muscle

• They include abductor digiti minimi, oppenens digit minimi, flexor digit minimi.

• They originate from flexor retinaculum and carpal bones & insert at proximal phalanx and metacarpal of the little finger.

Adductor pollicis

• They originate from 2^nd & 3^rd metacarpal & insert in first proximal phalanx.

• Both hypothenar and adductor pollicis is supplied by ulnar nerve.

Interossei

• There are 3 palmar and 4 dorsal interrosei muscles.

• They lie & originate between metacarpal bone.

• The palmar interosseous muscle and palmar portion of dorsal interosseus muscle have an insertion into extensor hood.

• Adduction of index, ring & little finger is done by palmar interossei.

• Abduction of index, ring & little finger by dorsal portion of dorsal interossei.

• Supplied by ulnar nerve.

Lumbricals

• They arise from flexor digitorum profundus tendon in the palm and course radially to metacarpophalangeal joint, reinforcing the interosseous lateral band on the radial side of digit.

• They mainly help in interphalangeal joint extension.

• Median nerve innervates radial two lumbricals whereas ulnar nerve innervates ulnar 2 lumbricals.

TENDONS OF THE FLEXOR COMPARTMENT

 Courtesy : Wikipedia

Flexor Compartment of the Forearm

EXAMINATION OF HAND INJURIES

Attitude and deformity

• Ape thumb deformity

  • Thumb being in the line with other metacarpal due to paralysis of oppenens pollicis (Median nerve palsy).

• Pointing Index

  • On asking the patient to make a fist the index finger remains straight.

  • It is due to paralysis of flexor digitorum superficialis and that of lateral half of flexor digitorum profundus muscle in median nerve palsy at a level proximal to elbow.

• Claw hand

• A deformity in which metacarpophalangeal is extended while proximal and distal interphalangeal joints are flexed. It is due to paralysis of lumbricals.

• In ulnar nerve palsy only the medial two fingers develop clawing while all the four fingers develop clawing in combined median and ulnar nerve palsies.

• Wrist drop

• Lesion of radial nerve injury.

• Policeman's receiving tip

• Characterised by an arm hanging by the side of the body and internally rotated with forearm extended at the elbow and fully pronated.

Tendon Injury

• Tendon has to be checked for full range of movements against resistance.

• It is important to check against resistance upto 90% of a tendon can be lacerated with preserved range of movements without resistance.

• Pain along the tendon during resistance is suggestive of tendon injury.

Sensory

• Two point discrimination test :Normal two point discrimination is <6mm at the finger tips and is often <2mm.

Courtsey : Wikepedia

Sensory supply. Blue : Ulnar Nerve, Rose : Radial Nerve, Brown : Median Nerve

Examination of the Median Nerve (Individual muscles)

• Abductor pollicis brevis : The action of this muscle is to do abduction. To test this muscle the patient is asked to lay his hand flat upon the table with the palm looking upwards and touch with his thumb a pen held in front of it : The pen test.

• Opponens pollicis : The patient is unable to touch the ends of the little finger with tip of the thumb.

• Flexor Pollicis Longus : The patient is unable to bend the terminal phalanx of the thumb while the proximal phalanx is held firmly by the clinician to eliminate this action of the short flexors.

• Flexor Digitorum Superficialis & Profundus : Paralysis of these muscle leads to ' pointing index' which is easily demonstrated by Oschner's clasping test when the patient is asked to clasp the hands the index finger of the affected side fails to flex.

• ANATOMY OF MEDIAN NERVE It is formed by the lateral and medial cords of brachial plexus. In the arm it descends adjacent to brachial artery. Course in the forearm The nerve enters the forearm between the two heads of the pronator teres. In the proximal third of the forearm it passes deep to the tendinous bridge of the origin of the flexor digitorum superficials . In mid forearm it descends between the flexor digitorum superficialis and flexor digitorum profundus. About 5 cm above the wrist, it comes to lie lateral side of the flexor digitorum superficialis. It becomes superficial just above the wrist, where it lies between the tendons of flexor digitorum superficialis and flexor carpi radialis. Course in the hand The nerve passes deep to the flexor retinaculum and enters the palm. Here a short and stout muscular branch from it supplies the muscles of the thenar eminence. The median nerve then divides into 4 or 5 palmar digital branches.

Courtsey : Wikipedia

Examination of Ulnar Nerve

• Flexor carpi ulnaris :

  • The patient is asked to palmar flex the wrist against gravity. By doing so the hand deviates to the radial side.

• Abductor digiti minimi:

  • The patient is asked to abduct the little finger against resistance while keeping the hand flat on the table.

• Interossei :

  • Ask the patient to abduct & adduct the fingers.

  • Give the patient a card or a piece of a paper and ask him to grip it between the fingers : Card test. (Palmar interossei)

  • Egawa's Test : With hand kept flat on a table the patient is asked to move his little finger sideways. (Dorsal Interossei)

• Abductor Pollicis : When the muscle is paralyzed the patient is unable to grip a piece of paper between the thumb and index finger. (Froment's sign)

Examination of radial nerve

• Triceps : The patient is asked to extend his elbow against resistance applied by the examiner, feel for contraction.

• Brachioradilais: The patient is asked to flex the elbow from 90 degrees onwards, keeping the forearm midprone. Feel for contraction of the muscle.

• Wrist extensor : In radial nerve injury the patient will be unable to extend the wrist (WRIST DROP), thumb and MCP joints of the fingers.

• Extensor digitorum : It causes extension of metacarpo-phalageal joints. Patient cannot do this if its paralysed.

• Extensor pollicis longus : This causes extension at inter-phalangeal joint of thumb. It should be examined after stabilizing metcarpo-phalangeal joint.

Simple Sensory and motor function test for nerves when there is injury at the level of elbow

Updated on 15/12/2014

Reference

• Tintinalli

• Essential Orthopedics, By J. Maheshwari