Upper Limb Arm & Forearm

Arm Cross Section The 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 Triceps brachii Lateral head Posterior surface of humerus – superior to radial grove Long head Infraglenoid tubercle Radial nerve Deep brachial a. All three heads have a common distal attachment on the olecranon Medial head Posterior surface of humerus – inferior to radial grove

Muscles of the Arm - Posterior Long head: Power assist for elbow extension Medial head : primary extensor Active throughout elbow extension Triceps Brachii Primary elbow extensor

Anterior Compartment coracobrachialis Biceps brachii brachialis Corocoid process to mid way along the medial humerus Long head – supraglenoid tubercle Short head- corocoid process brachialis Common insertion: tuberosity of the radius Anterior surface of humerus to coronoid process and tuberosity of the ulna Brachial a Musculocutaneous n.

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

Distal Humerus (right) In full flexion, the rim of the radial head slides in the capitulotrochlear groove and enters the radial fossa Medial Lateral The trochlear ridge of the olecrenon rides in the trochlear groove (right) Lenangie 8-1

Bones of the Elbow Anterior view Posterior view 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. Lateral lateral Medial Medial extensors flexors capitulum trochlea Attachment of the biceps Attachment of the brachialis Anterior view Posterior view

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 Formed by the vertical axis of the humerus and the vertical axis of the forearm The angulation is due to the configuration of the bony articulating surfaces Males = 5o Females = 10o - 15o

Transverse Axis Includes the humeroulnar and humeroradial joints Flexion and extension Flexors: Biceps, brachialis, brachioradialis Extensors: Triceps, anconeus

Elbow Flexors In 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

Collateral Ligaments medial Increase stability and joint apposition Annular ligament Ulnar collateral “MCL” medial Fibers of the radial collateral ligament attach to the annular ligament Capitulum Radial head lateral Radial collateral “LCL” Annular ligament

Annular Ligament Annular 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/ pronation Radial collateral Synovial fold

Radioulnar Joint Motion supination pronation

Radioulnar Joint Complex joint with 2 articulations connected by the interosseous membrane Superior (annular ligament) Inferior – with capsule and disc

Vertical Axis Humeroradial and radioulnar joints Forearm 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 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 lateral medial Thumb = pronator teres 5th digit (tucked under) = flexor digitorum superficialis 2nd digit = flexor carpi radialis 3rd digit = palmaris longus 4th digit = flexor carpi ulnaris

Deep Muscles of the Anterior Forearm Thumb Fingers Wrist Arise from the ulna (pronator quadratus, flexor digitorum profundus) and radius (flexor pollicis longus)

Superficial muscles of the posterior forearm extensor carpi radialis longus E superficial extensor carpi radialis brevis extensor carpi ulnaris Extensor carpi ulnaris Extensor carpi radialis brevis Extensor carpi radialis longus 3 Superficial Muscles

Intermediate muscles of the posterior forearm 2 Int Muscles Extensor digiti minimi muscle Extensor digitorum

Deep muscles of the posterior forearm Abductor pollicis longus Extensor pollicis brevis Extensor pollicis longus Supinator Extensor indices

Median Nerve All forearm muscles are innervated by the MEDIAN nerve EXCEPT: 1 ½ muscles flexor 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 lateral medial Radial artery Ulnar artery Common interosseous Anterior Posterior Dorsal and palmer carpal branches Dorsal and palmer carpal branches Deep (superficial) palmar arches superficial (deep)palmar arches

Injuries Cubital tunnel syndrome – contraction of the flexor carpi ulnaris causes nerve compression Stretch of the MCL during throwing 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