BPK 241 Lecture 10

Upper Arm Bones

• Humerus

  • Shaft (with bicipital groove)

  • Head, neck & tubercles

  • Condyles & epicondyles

• Coranoid fossa (anterior)

• Olecranon fossa (posterior)

Muscles of the anterior compartment

• Biceps brachii

  • O = supraglenoid tubercle, coracoid

  • I = radial tuberosity, forearm fascia

  • F = forearm flexion at elbow, supination (supinator magnus), assists shoulder flexion

• Brachialis (starts at ½ of shaft)

  • O = anterior surface of humerus

  • I = coracoid of ulna

  • F = flexion of forearm at elbow

• Coracobrachialis

  • F = assists flexion of arm at shoulder

• All three innervated by muscolocataneus nerve

How many attachments of bicep brachii to humerus?

None

Movements

• Forearm pronation & supination

  • Ulna is locked, doesn’t move

  • Radius rotate around ulna allowing pronation

Posterior Compartment muscles

• Triceps brachii

  • O = infraglenoid tubercle, upper lateral & lower medial halves of the posterior shaft of humerus

  • I = olecranon of ulna

  • F = extension of forearm at elbow

• Anconeus

  • O = lateral epicondyle

  • I = olecranon of ulna

  • F = assists triceps brachii

Arteries

• Brachial artery

  • Anteromedial in upper arm

  • Moves laterally and anteriorly at elbow to form ulnar and radial artery

• Profunda artery

  • Stops to exist beyond the elbow

Nerves

• Muscocutaneous

• Median

• Ulnar

• Radial

Elbow Bones

• Radius (lateral forearm bone)

  • Head

    • Articulates with capitulum

    • Articulates with radial notch of ulna

  • Distal articulation with ulna

  • Interosseous membrane between shafts of radius and ulna

• Ulna (medial forearm bone)

  • Trochlear notch (ulna) articulates with trochlea (humerus)

  • Olecranon process (posterior)

  • Coronoid process (anterior)

Joint type

Synovial and Hinge

Ligaments

• Capsular

• Medial (ulnar) collateral - prevent valgus movement

• Lateral (radial) collateral - prevent varus movement

  • Annular ligament

    • wraps head of radius, allows radius to rotate, supinate + pronate

• Moves across sagittal plane

Elbow Movements

• Flexion & extension

• Note: pronation & supination occur at radioulnar joints

Cubital fossa

• Anteriorly; inverted triangle

• Contains median and radial nerve, brachial artery and its derivatives, and tendon of biceps brachii

Radioulnar Joints

• Joint type

  • Synovial, pivot

• Articulations

  • Proximal

    • Radial head and radial notch of ulna

    • Annular ligament

  • Distal

    • Ulnar styloid & ulnar notch of radius

    • Fibrocartilage disc, capsule, capsular ligaments

  • Notes: interosseous membrane

Radioulnar Joint Movements

• Forearm pronation & supination

Radioulnar Joints: Active Muscles

• Supination

  • Bicep brachii (“supinator magnus”)

  • Supinator

  • Pulls elbow

• Pronation

  • Pronator teres (proximal)

  • Pronator quadratus (distal)

  • Pulls forearm

• From pronated or supinated to mid-range =

  • Brachioradialis - helps with mid-range supinate + pronate

Forearm Anterior Compartment

• Superficial

  • Pronator Teres

  • Flexor Carpi Radialis (FCR)

  • Palmaris Longus

  • Flexor carpi ulnaris (FCU)

• Intermediate

  • Flexor digitorum superficialis (FDS)

• Deep

  • Flexor digitorum profundus (FDP)

  • Flexor pollicis longus (FPL)

  • Pronator quadratus

Pronator Teres

• Rotate palm + pronate forearm

• Innervated by median nerve

FCR

• Metacarpals - attached to 2nd metacarpal

• Innervated by median nerve

Palmaris Longus

• Small muscle, 20% doesn’t have this

• Innervated by median nerve

FCU

• Attached to 5th metacarpal

• Innervated by ulnar nerve

FDS

• Send tendon to each finger, attaches to middle phalanges - flex wrist

• Innervated by median nerve

FDP

• Distal Phalanges

• Half innervated by median nerve

• Half innervated by ulnar nerve

FPL

• Thumb

• Innervated by median nerve

Pronator Quadratus

• Distal forearm into pronation

• Innervated by median nerve

Forearm Posterior Compartment

• Superficial

  • Brachioradialis

  • Extensor carpi radialis longus (ECRL)

  • Extensor carpi radialis brevis (ECRB)

  • Extensor digitorum (ED)

  • Extensor digiti minimi (EDM)

  • Extensor carpi ulnaris (ECU)

• Deep

  • Anconeus

  • Supinator

  • Abductor pollicis longus (APL)

  • Extensor pollicis brevis (EPB)

  • Extensor pollicis longus (EPL)

  • Extensor indicis (EI)

Brachioradialis

• Helps with elbow flexion, supination, pronation to mid range

• Innervated by radial nerve

ECRL

• 2nd metacarpal - radial deviation

• Innervated by radial nerve

ECRB

• 3rd Metacarpal

• Innervated by radial nerve

ED

• Distal phalanges - extends fingers

• Innervated by radial nerve

EDM

• Pinky extension

• Innervated by radial nerve

ECU

• 5th metacarpal, ulnar deviation, wrist extension

• Innervated by radial nerve

Anconeus

• Supinator, tricep extension

• Innervated by radial nerve

Supinator

• Supinates forearm

• Innervated by radial nerve

Snuffbox muscles

• APL, EPB, EPL

• Innervated by radial nerve

EI

• index finger

• Innervated by radial nerve

Flexion of hand at the wrist

• FCR, FCU, FDS, FDP, FPL

Extension of hand at wrist

• ECRL, ERB, ECU, ED, EDM, EI, APL, EPB, EPL

Adduction (ulnar deviation) of hand at wrist

• FCU, ECU

Abduction (radial deviation) of hand at wrist

• FCR, ECRL, ECRB

Circumduction of the hand

Requires flexion, extension, abduction, adduction plus pronation & supination

Wrist bones

• Radiocarpal joint

  • Distal radius

  • Proximal carpal bones

    • Scaphoid, lunate, triquetal, pisiform

  • Distal carpal bones

    • Trapezium, trapezoid, capitate, hamate

Wrist Ligaments

• Capsular (anterior & posterior)

• Collateral (medial & lateral)

• Intercarpal

Retinacula

• Hold tendon tight, posterior wrist gives support

• Extensor

• Flexor (N.B., roof of carpal tunnel)

“Anatomical Snuffbox” of the wrist

• Anatomy

  • Medially = Extensor pollicis longus (EPL) tendon

  • Laterally = Extensor pollicis brevis (EPB, Abductor pollicis longus (APL) tendons

  • Floor = scaphoid

“Anatomical Snuffbox” of the wrist - Significance

• Scaphoid bone

  • Narrow waist (fracture site)

  • Retrograde blood supply (not great blood supply)

  • Ischaemic (avascular) necrosis is common complication of untreated scaphoid fracture - degeneration of bone

  • Scaphoid necessary for full, pain-free wrist function

• X-Rays do not show scaphoid fracture at first

  • Hence, tenderness in snuffbox? Assume fracture?

Hand Bones

• Metacarpals I (thumb-side)

• V (pinky side)

• Phalanges (as in toes)

Hand Joints

• Carpometacarpal

• Metacarpophalangeal (MCP)

• Interphalangeal (IP)

Carpometacarpal

• Metacarpal II-V = gliding, minimal movement

• 1st Metacarpal with trapezium = synovial, saddle joint, flexion/extension, abduction/adduction & circumduction (opposition)

MCP

• Primarily flexion/extension

• Strong collateral ligaments

• Strong flexor & extensor tendons

• Some adduction & abduction

IP

• Synovial joints

• Flex & extend

• Collateral ligaments

Intrinsic muscles of the hand

• Thenar (thumb) eminence

• Hypothenar (pinky finger) eminence

• Dorsal & Palmar interosseous muscles (DABS & PADS)

• Lumbricals

Thenar (thumb) eminence

• Opponens pollicis

• Abductor pollicis brevis (APB)

• Flexor pollicis brevis (FPB)

• Innervated by median nerve

Hypothenar (pinky finger) eminence

• Opponens digiti minimi

• Abductor digiti minimi

• Flexor digiti minimi

• Innervated by ulnar nerve

DABS & PADS

• Innervated by ulnar nerve

Lumbricals

• Innervated by median nerve

• Innervated by ulnar nerve

• Puppet muscle

Innervation of Hand

• All muscles in hand innervated by ULNAR nerve EXCEPT: ½ LOAF by median nerve

• Thumb ½ of Lumbricals

• Thenar eminence muscles (Opponens pollicis, Abductor pollicis, Flexor pollicis brevis)