Upper Limb

Arm & Forearm

Arm Cross SectionThe intermuscular septum and the humerus divide

the arm into anterior and posterior compartments

Anterior Compartment: Flexor’s “3” muscles Musculocutaneous nerve Brachial artery

Posterior Compartment: Extensor’s “3” muscles Radial nerve Deep brachial artery

Posterior Compartment

Medial head

Lateral head

Long head

Triceps brachii

Radial nerve Deep brachial a.

Infraglenoid tubercle

Posterior surface of humerus – superior to radial grove

All three heads have a common distal attachment on the olecranon

Posterior surface of humerus – inferior to radial grove

Muscles of the Arm - Posterior

Triceps BrachiiPrimary elbow

extensor

Medial head : primary extensor

Active throughout elbow extension

Long head: Power assist for elbow extension

Anterior Compartment

Brachial a

coracobrachialis

brachialis

Musculocutaneous n.

Biceps brachii

Long head – supraglenoid tubercle

Short head- corocoid processCommon insertion: tuberosity of the radius

Corocoid process to mid way along the medial humerus

Anterior surface of humerus to coronoid process and tuberosity of the ulna

Muscles of the Arm - Anterior

Biceps Brachii Primary

forearm supinator

Power assist for elbow flexion

Brachialis Primary elbow

flexor Active

throughout elbow flexion

Coracobrachialis

Action at the GH joint for flexion & adduction

Elbow Joint- A “Hinge” Joint

Humero-ulnar joint

Humero-radialjoint

Enclosed in a single joint capsule (along with the superior radioulnar joint)

Distal Humerus

(right)The trochlear ridge of the olecrenon rides in the trochlear groove

In full flexion, the rim of the radial head slides in the capitulotrochlear groove and enters the radial fossa

Lenangie 8-1

MedialLateral

Bones of the Elbow

Attachment of the brachialis

Attachment of the biceps

flexorsextensors

The lower end of the humerus flairs out as epicondyles. These provide a mechanical advantage to the forearm muscle groups that attach at these sites.

Anterior view Posterior view

LaterallateralMedial Medial

capitulum trochlea

Elbow Xray

• O = olecranon• T = trochlea of the

humerus• CP = coronoid

process of the ulna• HR = head of the

radius• C = capitulum

Carrying Angle of the Elbow

The angulation is due to the configuration of the bony articulating surfaces

Males = 5o

Females = 10o - 15o

Formed by the vertical axis of the humerus and the vertical axis of the forearm

Transverse Axis Includes the humeroulnar

and humeroradial joints

Flexion and extension

Flexors:Biceps, brachialis, brachioradialis

Extensors:Triceps,anconeus

Elbow FlexorsIn addition to the biceps and brachialis, the brachioradialis also functions as a flexor of the elbow

Each functions at differing degrees of supination and pronation of the forearm

medial

lateral

Annular ligamentRadial collateral“LCL”

Annular ligament

Ulnar collateral“MCL”

CapitulumRadial head

Fibers of the radial collateral ligament attach to the annular ligament

Collateral LigamentsIncrease stability and joint apposition

Annular LigamentAnnular

ligament acts like a sling holding the radial head close to the ulna bone

Annular ligament offers support but allows rotation (spin) as well as glide of the radial head during supination/ pronationRadial

collateral

Synovial fold

Radioulnar Joint Motion

supination pronation

Radioulnar JointComplex joint with 2 articulations connected by the interosseous membrane Superior (annular ligament)

Inferior – with capsule and disc

Vertical AxisHumeroradial and radioulnar jointsForearm supination and pronation

Muscles of Supination/Pronation

Supinator &biceps brachii

Pronator teres &pronator quadratus

Forearm Cross Section

The interosseus membrane and radius and ulna divide the forearm in to anterior and posterior compartments

Innervation rule

• All muscles of the anterior compartment are supplied by the median nerve Or Ulnar nerve

• All muscles of the posterior compartment are supplied by the radial nerve.

Superficial Muscles of the Anterior Forearm

5 superficial muscles

From the common flexor tendon arising from the medial condyle of the humerus

Cross the elbow but have minimum function at that joint

Surface Anatomy - Anterior Forearm

mediallateral

5th digit (tucked under) = flexor digitorum superficialis

Thumb = pronator teres

2nd digit = flexor carpi radialis

3rd digit = palmaris longus

4th digit = flexor carpi ulnaris

3 Deep Muscles

Deep Muscles of the Anterior Forearm

Arise from the ulna (pronator quadratus, flexor digitorum profundus) and radius (flexor pollicis longus)

ThumbFingersWrist

Superficial muscles of the posterior forearm

extensor carpi radialis longus

Esuperficial extensor carpi radia

lis brevisE

superficial extensor carpi ulnaris

3 Superficial Muscles

Extensor carpi ulnaris

Extensor carpi radialis brevis

Extensor carpi radialis longus

Intermediate muscles of the posterior forearm

2 Int Muscles

Extensor digiti minimi muscle

Extensor digitorum

Deep muscles of the posterior forearm

5 musclesAbductor pollicis

longusExtensor pollicis

brevisExtensor pollicis

longusSupinatorExtensor indices

Median Nerve

All forearm muscles are innervated by the MEDIAN nerve EXCEPT:

1 ½ musclesflexor carpi ulnaris ulnar side of the flexor digitorum profundus Plus: All thenar

mm except adductor pollicis

Brachial Artery in Situ

Posterior circumflex humeral a. runs with the axillary nerve

Deep brachial a. runs with radial nerve

Superior ulnar collateral a. runs with the ulnar nerve

Brachial Artery Anastomoses

Radial & Ulnar Arteries

mediallateral

Ulnar artery

Common interosseous Anterior PosteriorDorsal and palmer carpal branches

Radial artery

superficial (deep)palmar arches

Deep (superficial) palmar arches

Dorsal and palmer carpal branches

Injuries

Stretch of the MCL during throwing

Cubital tunnel syndrome – contraction of the flexor carpi ulnaris causes nerve compression

Loss of IR & ER rotation of the shoulder may lead to excessive pronation of supination of the forearm and subsequent muscle strain

Injuries

Nursemaid’s elbow – radial head subluxed from the annular ligament in an unexpected pull

Fall on the outstretched hand may lead to fracture of the elbow