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


Anterior Compartment :Anterior Compartment Brachial a coracobrachialis brachialis Musculocutaneous n. Biceps brachii Long head – supraglenoid tubercle Short head- corocoid process Common 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 :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


Thin Man :Thin Man What are the following bony structures: 3,17,21,25,33? What are the following muscles: 1,2,4,5,24,20,19,31,30?


Elbow Joint- A “Hinge” Joint :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 :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 Medial Lateral


Bones of the Elbow :Bones of the Elbow Attachment of the brachialis Attachment of the biceps flexors extensors 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 Lateral lateral Medial Medial capitulum trochlea


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


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


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 :Radioulnar Joint Motion supination pronation


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


Vertical Axis :Vertical Axis Humeroradial and radioulnar joints Forearm supination and pronation


Muscles of Supination/Pronation :Muscles of Supination/Pronation Supinator & biceps brachii Pronator teres & pronator quadratus


Superficial Muscles of the Anterior Forearm :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 no function at that joint


Surface Anatomy - Anterior Forearm :Surface Anatomy - Anterior Forearm medial lateral 5th digit (tucked under) = flexor digitorum superficialis Thumb = pronator teres 2nd digit = flexor carpi radialis 3rd digit = palmaris longus 4th digit = flexor carpi ulnaris


Deep Muscles of the Anterior Forearm :3 Deep Muscles Deep Muscles of the Anterior Forearm Arise from the ulna (pronator quadratus, flexor digitorum profundus) and radius (flexor pollicis longus) Thumb Fingers Wrist


Median Nerve :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 :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 :Brachial Artery Anastomoses


Radial & Ulnar Arteries :Radial & Ulnar Arteries medial lateral Ulnar artery Common interosseous Anterior Posterior Dorsal and palmer carpal branches Radial artery superficial (deep)palmar arches Deep (superficial) palmar arches Dorsal and palmer carpal branches


Injuries :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 :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