Extensors.txt

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emm64
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105873
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Extensors.txt
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2011-10-03 18:41:02
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UL Extensors
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Upper Limb Extensors
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  1. Dermatomal Hand
    • Dermatomal Pattern – is very different from the cutaneous nerve innervation pattern.
    • Clinical Significance: Knowing these two different patterns allows one to test for peripheral nerve problems (cutaneous nerve innervation pattern) or neurologic (spinal cord or spinal nerve) level problems (dermatomal pattern).

    Note: Be aware that dermatomal maps may differ somewhat depending on the source.
  2. Posterior Compartment Muscles Deep
    • B. The deep layer muscles:
    • 1. supinator
    • 2. abductor pollicis longus
    • 3. extensor pollicis brevis
    • 4. extensor pollicis longus
  3. Posterior Compartment Muscles Superficial
    • A. The superficial layer muscles:
    • lateral group (these muscles all have �radialis� in their names)
    • 1. brachioradialis
    • 2. extensor carpi radialis longus
    • 3. extensor carpi radialis brevis
    • posterior group
    • 4. extensor carpi ulnaris
    • 5. extensor digitorum
    • 6. extensor digiti minimi
    • 7. anconeus � assists the triceps

    • 5. extensor indicis
    • (remember: 3 muscles to the thumb, 1 to the index finger, & supinator)
  4. Anatomical Snuff Box
    • is a triangular space on the dorsum of the hand related to the thumb region.
    • The boundaries are:
    • the extensor pollicis brevis (EPB)
    • the abductor pollicis longus tendon (APL)
    • the extensor pollicis longus tendon (EPL)
    • the extensor retinaculum.
    • Coursing through the floor of this space is the radial artery.
    • Clinical note: A pulse can be taken here. Also, the floor can be palpated if a fracture of the scaphoid is suspected.
  5. Extensor Retinaculum and Extensor Expansions
    • 1. The extensor retinaculum is a band of deep fascia that keeps the extensor tendons in place when the extensor muscles contract.
    • 2. The extensor tendons are protected by snovial tendon sheaths which help reduce the friction when the extensor tendons slide under the extensor retinaculum.
    • 3. Distally, the extensor tendons become flattened to form the extensor expansions
    • 4. Deep to the extensor tendons the dorsal interossei muscles can be seen. These will be studied in more detail when we do the hand.
  6. III. Osteology & Joints of the Hand
    • A. Identify the following structures:
    • 1. carpal bones (region of the carpus)
    • 2. metacarpals 1-5 (and region of the metacarpus)
    • 3. phalanges (proximal, intermediate, distal)
    • 4. scaphoid
    • 5. trapezium
    • 6. trapezoid
    • 7. lunate
    • 8. capitate
    • 9. triquetrium
    • 10. pisiform
    • 11. hamate
    • 12. interphalangeal (IP) joint
    • 13. metacarpophalangeal (MP) joints
    • 14. carpometacarpal joints
    • 15. intercarpal joints
  7. The Wrist Joint
    • radiocarpal joint-articulation between the distal radius, an articular (fibrocartilaginous) disc, and the proximal row of carpal bones.
    • synovial joint innervated by the radial, median, and ulnar nerves.
    • Blood supply to the joint is by way of dorsal & palmar carpal arterial arches.
    • Note: The ulna is not involved in the wrist joint. The distal radioulnar joint is also not part of the wrist joint. The distal radioulnar joint acts along with the proximal radioulnar joint of the elbow to allow pronation & supination of the forearm and hand.
  8. Anterior wrist
    • the structures crossing the wrist (and their relationships) are important in palpation, assessing pathology, administering injections, and in understanding the normal anatomy and function of the wrist and hand regions
    • A. flexor carpi ulnaris tendon
    • B. ulnar nerve
    • C. ulnar artery
    • D. palmaris longus tendon (may be absent in some people)
    • E. median nerve
    • F. flexor carpi radialis tendon
    • G. radial artery
  9. carpal tunnel
    • the area between the flexor retinaculum and the carpal bones.\
    • It contains the tendons of the flexor digitorum superficialis, flexor digitorum profundis, flexor pollicis longus, and the median nerve.
    • Note: the tendon for flexor carpi radialis is not in the carpal tunnel, but is in its own space. Also the ulnar nerve and artery are not in the carpal tunnel.
    • Clinical significance - inflammation in the carpal tunnel (e.g., of the synovial sheath tendons surrounding the flexor tendons in the tunnel) can cause compression of the median nerve. This can produce both sensory and motor symptoms which are characteristic of �carpal tunnel syndrome.� If the median nerve is compressed, atrophy of the thenar compartment muscles of the hand may result (see section V A below).
  10. Thenar compartment (hand)
    • contains 3 muscles relating to the thumb (pollicis)
    • 1. abductor pollicis brevis
    • 2. flexor pollicis brevis
    • 3. opponens pollicis
    • motor nerve: median nerve (recurrent branch)
    • Clinical Significance: compression of the median nerve in the carpal tunnel may
    • cause atrophy of these thenar compartment muscles.
  11. Hypothenar compartment (hand)
    • contains 3 muscles relating to the little digit (digiti minimi).
    • Think of the hypothenar and thenar compartments as being �mirror-images� of one another: each compartment has an �abductor, flexor, and opponens� muscle.
    • 1. abductor digiti minimi
    • 2. flexor digiti minimi
    • 3. opponens digiti minimi
    • motor nerve: ulnar nerve (deep branch)
  12. Central compartment (hand)
    • contains flexor tendons & 4 lumbricals
    • 1. flexor tendons (flexor digitorum profundis, flexor digitorum superficialis)
    • 2. lumbricals (attaching to the flexor digitorum profundis tendons)
    • a. flex at the MP joints, extend at the IP joints
    • b. lateral 2 innervated by median nerve, medial 2 by ulnar nerve � note how the lumbricals retain the same innervation pattern as the flexor digitorum profundis whose tendons the lumbricals attach to.
    • motor nerves: median and ulnar nerves (see D2b above)
  13. Deep compartment (hand)
    • also known as adductor/interossei compartment contains:
    • 1. adductor pollicis
    • 2. interossei muscles (both dorsal and palmar)
    • a. palmar interossei - adduct the digits (PAD)
    • b. dorsal interossei � abduct the digits (DAB)
    • motor nerve: ulnar nerve (deep branch)
  14. Hand Cross section
  15. Motor Innervation Pattern of Hand
    • In the forearm, we said that almost all the muscles of the anterior compartment were innervated by the median nerve except for 1 � muscles � which are innervated by the ulnar nerve.
    • In the hand, this �pattern� is reversed. So our rule and exception is the following.
    • �All the intrinsic muscles of the hand are innervated by the ulnar nerve, except for the muscles of 1 � compartments: the thenar compartment muscles and the lateral two lumbricals (half of the muscle bellies in the central compartment) - which are innervated by the median nerve.� Remember that in the central compartment you just have flexor tendons (whose muscles are in the anterior compartment of the forearm, not in the hand) and the 4 muscle bellies of the lumbricals. It should be noted that the 3 muscles of the thenar compartment are innervated by a branch of the median nerve called the �recurrent branch of the median nerve.� It is fairly superficial. If this nerve is severed, then all 3 muscles of the thenar compartment will be paralyzed.
  16. Blood Supply to the Upper Limb (Big Picture)
    • hould be understood from the subclavian artery which changes names at the inferior margin of the 1st rib and becomes the axillary artery.
    • Both of these arteries and branches are involved in the anastomoses around the scapula.
    • At the inferior margin of teres major, the axillary artery changes names and becomes the brachial artery.
    • It runs in a neurovascular bundle which comes down the medial aspect of the arm.
    • After traversing the cubital fossa, it divides into the radial and ulnar arteries in the forearm.
    • The ulnar artery gives rise to the common interosseus artery which divides immediately into an anterior interosseus which runs in the anterior compartment and a posterior interosseus which runs in the posterior compartment of the forearm).
  17. Blood Supply to the Hand
    • The radial and ulnar arteries continue distally in the anterior compartment and then cross the wrist to form the superficial and deep palmar arches of the hand The deep palmar arch is primarily formed by the radial artery.
    • The superficial palmar arch is primarily from the ulnar artery. From these arches, arise common palmar digital arteries (which are related to the metacarpal bones) which then give rise to proper palmar digital arteries which run on each side of the digits.
  18. Cutaneous Innervation Pattern of the Upper Limb
    • One pattern is formed by the regions of skin innervated by specifically named cutaneous nerves. This is called the �cutaneous nerve innervation pattern.�
    • The other pattern is the �dermatomal innervation pattern.�
    • They are different because the dermatomal pattern reflects strips of skin that are innervated (by definition) by fibers coming from a single spinal nerve or spinal cord segment.
    • The cutaneous nerve innervation pattern, on the other hand, is produced by named cutaneous nerves. These named cutaneous nerves may be formed from fibers from several different spinal nerves or spinal cord segments.
  19. Cutaneous nerve innervation pattern
    • know which major nerve is responsible for innervating the different cutaneous regions of the upper limb.
    • Clinical Significance: Knowing these two different patterns allows one to test for peripheral nerve problems (cutaneous nerve innervation pattern) or neurologic (spinal cord or spinal nerve) level problems (dermatomal pattern). Note: Be aware that dermatomal maps may differ somewhat depending on the source.
  20. Dermatomal pattern
    • you should also be familiar with the dermatomal pattern of the upper limb. This is very useful to know clinically.
    • For example, in addition to any motor functional loss, a lesion of the upper trunk of the brachial plexus would be reflected in a sensory deficit in which dermatomes? Which dermatomes would experience a sensory deficit in a lesion of the lower trunk of the brachial plexus?
  21. Cutaneous Nerve Innervation Pattern
    • As the median and ulnar nerves enter the hand they give rise to the common plantar digital nerves (which are related to the metacarpal bones) which then give rise to the palmar digital nerves that travel along the sides of each digit. These nerves along with cutaneous branches of the superficial radial nerve form the cutaneous nerve innervation pattern of the hand.
  22. triceps
    • attach:medial head - humerus (posterior inferior aspect)
    • lateral head - humerus (posterior superior aspect)
    • long head - infraglenoid tubercle of scapula
    • olecranon process of ulna
    • nerve:radial nerve
    • action:extends forearm at elbow (all heads), extends arm at shoulder (long he
  23. brachioradialis
    • attach:lateral supracondylar ridge of humerus
    • distal radius
    • nerve: radial n.
    • action: flexes forearm
    • Lateral Superficial Extensor (posterior) Forearm
  24. extensor carpi radialis longus
    • attach: lateral supracondylar ridge of humerus
    • 2nd metacarpal (base of)
    • nerve:radial n.
    • action: extension and abduction (radial deviation) of hand at wrist joint
    • Lateral Superficial Extensor (posterior) Forearm
  25. extensor carpi radialis brevis
    • attach: lat. epicondyle of humerus (via common extensor tendon)
    • 3rd metacarpal (base of)
    • nerve:posterior interosseus n. (of radial n.)
    • action: extension of hand at wrist joint
    • Lateral Superficial Extensor (posterior) Forearm
  26. extensor digitorum
    • attach: lat. epicondyle of humerus (via common extensor tendon)
    • extensor expansions of medial four digits
    • nerve: posterior interosseus n. (of radial n.)
    • action: extends medial 4 digits, extends hand
    • Posterior Superficial Extensor (posterior) Forearm Group
  27. extensor digiti minimi
    • attach:lat. epicondyle of humerus (via common extensor tendon)
    • extensor expansion of 5th digit
    • nerve:posterior interosseus n. (of radial n.)
    • action:extends 5th digit
    • Posterior Superficial Extensor (posterior) Forearm Group
  28. extensor carpi ulnaris
    • attach: lat. epicondyle of humerus (via common extensor tendon), posterior ulna
    • base of 5th metacarpal bone
    • nerve: posterior interosseus n. (of radial n.)
    • action: extends & adducts (ulnar deviation) hand at wrist joint
    • Posterior Superficial Extensor (posterior) Forearm Group
  29. anconeus
    • attach: lat. epicondyle of humerus
    • posterior ulna & olecranon
    • nerve: radial n.
    • action: assists triceps in extending forearm at the elbow
    • Posterior Superficial Extensor (posterior) Forearm Group
  30. supinator
    • attach: lat. epicondyle of humerus, superior ulna
    • proximal 1/3 radius
    • nerve: deep radial n.
    • action: supinates forearm
    • Deep Extensor (posterior) Forearm Group
  31. extensor indicis
    • attach: posterior ulna, interosseus membrane
    • extensor expansion of 2nd digit
    • nerve: posterior interosseus n. (of radial n.)
    • action: extends 2nd digit, helps to extend hand
    • Deep Extensor (posterior) Forearm Group
  32. extensor pollicis longus
    • attach: posterior ulna & radius, interosseus membrane
    • base of distal phalanx of thumb
    • nerve: posterior interosseus n. (of radial n.)
    • action: extends distal phalanx of thumb
    • Deep Extensor (posterior) Forearm Group
  33. extensor pollicis brevis
    • attach: posterior radius, interosseus membrane
    • base of proximal phalanx of thumb
    • nerve: posterior interosseus n. (of radial n.)
    • action: extends proximal phalanx of thumb
    • Deep Extensor (posterior) Forearm Group
  34. abductor pollicis longus
    • attach: posterior ulna & radius, interosseus membrane
    • base of 1st metacarpal bone
    • nerve: posterior interosseus n. (of radial n.)
    • action: abducts & extends thumb
    • Deep Extensor (posterior) Forearm Group
  35. Superficial Neurovascular Plane (Deep to Palmar Aponeurosis, Superficial to All Compartments)
    • nerves: cutaneous branches of median and ulnar nerves
    • artery: superficial palmar arch
  36. Abductor pollicis brevis
    • attach: flexor retinaculum, scaphoid & trapezium
    • proximal phalanx of thumb
    • innerv: median n. - recurrent branch
    • action: abducts thumb & helps oppose it
    • Thenar Compartment
  37. Flexor pollicis brevis
    • attach: flexor retinaculum, trapezium
    • proximal phalanx of thumb
    • innerv: median n. (recurrent branch)
    • action: flexes thumb
    • Thenar Compartment
  38. Opponens pollicis
    • attach: flexor retinaculum, trapezium
    • 1st metacarpal bone
    • innerv: median n. (recurrent branch)
    • action: opposes thumb to other digits
    • Thenar Compartment
  39. Abductor digiti minimi
    • attach: pisiform
    • proximal phalanx of 5th digit
    • innerv: ulnar n. (deep branch)
    • action: abducts 5th digit
    • Hypothenar Compartment
  40. Flexor digiti minimi
    • attach: hook of the hamate, flexor retinaculum
    • proximal phalanx of 5th digit
    • innerv: ulnar n. (deep branch)
    • action: flexes prox. phalanx of 5th digit
    • Hypothenar Compartment
  41. Opponens digiti minimi
    • attach: hook of hamate, flexor retinaculum
    • 5th metacarpal bone
    • innerv: ulnar n. (deep branch)
    • action: brings 5th digit into opposition with thumb
    • Hypothenar Compartment
  42. Lumbricals
    • attach: tendons of flexor digitorum profundis
    • extensor expansions of digits 2-5
    • innerv: lateral 2 � median n., medial 2 � ulnar n.
    • action: flexes at MP joints and extends at IP joints
    • Central Compartment
  43. Neurovascular Plane (between Central and Deep Compartments)
    • nerve: deep branch of ulnar nerve
    • artery: deep palmar arch
  44. Adductor pollicis
    • attach: 2nd & 3rd metacarpals, capitate
    • base of prox. phalanx of thumb
    • innerv: ulnar n. (deep branch)
    • action: adducts thumb
    • Deep Compartment
  45. Palmar interossei
    • attach: sides of 2nd, 4th, and 5th metacarpal bones
    • prox. phalanges of digits 2, 4, and 5.
    • innerv: ulnar n. (deep branch)
    • action: adducts digits (PAD)
    • Deep Compartment
  46. Dorsal interossei
    • attach:adjacent metacarpal bones
    • proximal phalanges of digits 2-4
    • innerv: ulnar n. (deep branch)
    • action: abducts digits (DAB)
    • Deep Compartment

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