FACTS & HINTS

HIGH-YIELD FACTS

Clinical Points

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Fracture of the Humerus

Fractures of the humerus most common at the surgical neck

Especiallycommon in elderlyindividuals with osteoporotic bone, falling on an outstretched arm

The axillarynerve vulnerable to damage here

Direct blow to the arm may

Fracture humerus through its midshaft, with risk of injuryto the radial nerve

Fracture humerus at distal end, risking damage to the median nerve

Biceps Tendonitis

Is inflammation of the tendon of the long head of the biceps

Tendon is susceptible to wear and tear as it moves back and forth within the intertubercular groove

Degenerative wear a common cause of shoulder pain

Inflammation also caused byrepetitive microtrauma, seen in certain sports such as tennis

Rupture of the Biceps Brachii

This produces "Popeye deformity" with muscle forming a ball in distal part of the anterior arm

Tendon of long head has the highest rate of spontaneous rupture of anytendon in the body

Rupture of the tendon on background of chronic tendonitis usuallyaffects those older than 40

Traumatic rupture mayoccur in younger individuals, but is rare

MNEMONICS

Memory Aids

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46 Elbow and Forearm

STUDYAIMS

At the end of your study, you should be able to:

Identifythe different parts and surface markings of the radius and ulna

Describe the articulations of the elbow joint, its movements, and supporting ligaments

Describe the distal radioulnar joint, its movements, and supporting ligaments

Describe the organization of the deep fascia and compartments of the arm

Know the origins, insertions, and actions of the major muscles of the forearm

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GUIDE

Upper Limb: Elbow and Forearm

[Plate 437, Forearm: Serial Cross Sections]

Bones

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Ulna

Stabilizing bone of the forearm

Medial to and longer than radius

Osteological features

Olecranon-projection of proximal posterior end

Coronoid process-projection from proximal anterior end

Trochlear notch-anterior surface of olecranon, articulates with trochlea of humerus

Radial notch-rounded concavityon lateral side of coronoid process for radial head

Ulnar tuberosity-inferior to coronoid process for attachment of brachialis muscle

Supinator crest-crest inferior to radial notch for attachment of supinator muscle

Supinator fossa-concavitybetween supinator crest and coronoid process, for attachment of supinator muscle

Body-thicker proximally, tapering distally

Head-at distal end

Styloid process-conical process from the head

Radius

Lateral and shorter bone of the forearm

Osteologic features

Head-at proximal end, concave for articulation with capitulum of humerus

Neck-constricted region between head and tuberosity

Radial tuberosity-oval protuberance below head and neck for attachment of biceps brachii

Body-convexlaterallyand enlarging distally

Styloid process-projection from lateral aspect of distal end of radius

Dorsal tubercle-dorsal projection at distal end between groves for tendon of extensor carpi radialis longus and brevis and tendon of extensor pollicis longus

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Ulnar notch-concavityon medial side of distal end for head of ulna

Radius and ulna connected by

Interosseous membrane

Separates forearm into anterior and posterior compartments

Provides attachment for deep muscles of forearm

Fibers slope downward from radius to ulna

Is most tense when hand is in mid-prone position

Has a gap distal to neck of radius for posterior interosseus vessels

Oblique cord

Crosses gap in interosseus membrane

Attaches neck of radius to ulnar tuberosity

Radioulnar joints-proximal and distal (see below)

Elbow Joint

[Plate 425, Elbow: Radiographs]

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[Plate 426, Ligaments of Elbow]

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Compound synovial joint in which radius and ulna articulate with humerus Joint cavitycontinuous with radioulnar joint

Fibrous capsule encloses all three articulations Humeroulnar joint

Uniaxial, synovial hinge joint

Between trochlea of humerus and trochlear notch of ulna Humeroradial joint

Uniaxial, synovial hinge joint

Between capitulum of humerus and head of radius

Blood supplyto humeroulnar and humeroradial joints: anastomoses around elbow from brachial, radial, and ulnar arteries Nerve supplyto these joints: musculocutaneous, radial, and ulnar nerves

Proximal radioulnar joint

Uniaxial, synovial pivot joint

Between head of the radius and radial notch of the ulna

Blood supply: anterior and posterior interosseous arteries

Nerve supply: musculocutaneous, median and ulnar nerves Ligaments reinforcing elbow joint

Ulnar collateral ligament: medial epicondyle to coronoid process and olecranon

Radial collateral ligament: lateral epicondyle to annular ligament

Annular ligament

Strong fibrous circle

From margins of radial notch of ulna

Encircles head of radius

Maintains position of the radial head during pronation and supination Movements at the elbow joint

Flexion ( 180 degrees) and extension at humeroulnar and humeroradial joints

Pronation and supination with rotation of the head of the radius within annular ligament at proximal radioulnar joint Distal radioulnar joint

Synovial pivot joint

Articulation between ulnar notch and articular facet of radius at its distal end

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Afibrocartilaginous articular disc binds the ends of the radius and ulna and is strengthened byanterior and posterior ligaments

Disc separates cavityof joint from cavityof wrist joint

Pronation and supination: distal end of radius moves anteriorlyand mediallyacross the ulna

Blood supply: anterior and posterior interosseous arteries

Nerve supply: posterior interosseous nerve Carrying angle

The angle between the long axis of the humerus and the long axis of the ulna with forearm fullyextended and supinated in the anatomical position

Ten to 15 degrees in males, more than 15 degrees in females (figures are for deviations from 180 degrees)

Bursae (important ones)

Subcutaneous olecranon bursa: Overlies olecranon in subcutaneous tissue

Subtendinous olecranon bursa: Between the olecranon and triceps tendon Bicipitoradial bursa: Between biceps tendon and anterior part of radial tuberosity

Fascial Compartments of Forearm

Forearm divided into anterior and posterior compartments byinterosseous membrane Antebrachial fascia is thickened at distal end of radius

Posteriorlyforms extensor retinaculum

Anteriorlyforms palmar carpal ligament

Also forms flexor retinaculum (transverse carpal ligament) distal and deeper to palmar carpal ligament

Carpal tunnel formed between flexor retinaculum, running between tubercles of scaphion and trapezium radiallyto pisiform and hook of hamate on ulnar side, and anterior concavityof the carpus

Muscles of the Forearm (listed from lateral to medial)

[Plate 429, Individual Muscles of Forearm: Extensors of Wrist and Digits]

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[Plate 432, Muscles of Forearm (Superficial Layer): Posterior View]

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[Plate 433, Muscles of Forarm (Deep Layer): Posterior View]

Extensor pollicis brevis and longus (extend thumb)

Extensor indicis (extend indexfinger)

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