Upper Limb Anatomy: Clavicle

• This video is the first part of a YouTube series on the anatomy of the upper limb for students preparing for FMGE, NEET PG, NEXT, or USMLE Step 1 exams.
• The series aims to provide a comprehensive understanding of the upper limb's structures, including bones, joints, muscles, nerves, and blood vessels.
• Understanding upper limb anatomy is important for clinical practice, surgical procedures, and diagnostic interpretation.

Clavicle

• The clavicle is an elongated bone.
• Acts as a strut, positioning the upper limb away from the thorax allowing it to move freely.
• The clavicle transmits forces from the upper limb to the axial skeleton.
• The clavicle is more commonly fractured than the head of the humerus.
• The clavicle is the first bone to start ossifying, around the 5th or 6th week in utero.
• It is the last bone to complete ossification, around 21-25 years of age.
• The clavicle articulates medially with the manubrium of the sternum at the sternoclavicular joint.
• It articulates laterally with the acromion of the scapula at the acromioclavicular joint.
• The medial 2/3 of the clavicle is convex forward.
• The lateral 1/3 of the clavicle is concave forward.

Joints

• The sternoclavicular joint is a synovial joint.
• A synovial joint is a connection between two bones consisting of a cartilage lined cavity filled with fluid.
• The sternoclavicular joint contains an articular disc, similar to the knee joint, making it more stable.
• The sternoclavicular joint allows for elevation, depression, protraction, retraction and some rotation.
• The acromioclavicular joint is a plane synovial joint.
• The acromioclavicular joint allows for gliding and rotation movements.

Scapula

• The scapula is a flat, triangular bone located on the posterior aspect of the thorax.
• It overlies ribs 2-7.
• The spine of the scapula divides the posterior surface into the supraspinous fossa and infraspinous fossa.
• The supraspinous fossa is smaller and located superior to the spine, while the infraspinous fossa is larger and located inferior to the spine.
• The scapula has three borders: superior, medial, and lateral.
• The superior border is the shortest and thinnest.
• The medial border runs parallel to the vertebral column.
• The lateral border extends from the glenoid cavity to the inferior angle.
• The scapula has three angles: superior, inferior, and lateral.
• The lateral angle is the thickest part of the scapula and includes the glenoid cavity, which articulates with the head of the humerus to form the shoulder joint.
• The anatomical neck of the humerus is directly below the head.
• The surgical neck is the region where the humerus is most prone to fractures.
• The axillary nerve and posterior circumflex humeral artery run through the quadrangular space near the surgical neck.
• Fractures in the surgical neck can damage these structures.

Medial Lip

• The intertubercular groove has a medial lip and a lateral lip.
• The medial lip is the insertion point for the teres major muscle.
• The lateral lip is the insertion point for the pectoralis major muscle.
• The floor of the intertubercular groove is the insertion of the latissimus dorsi muscle.
• Teres major, pectoralis major, and latissimus dorsi insert on the humerus.

Nerve Injuries

• Damage to the axillary nerve (C5-C6) can occur due to fractures of the surgical neck of the humerus, shoulder dislocations, or improper use of crutches.
• Axillary nerve damage results in paralysis of the deltoid and teres minor muscles, impairing abduction of the arm.
• Suprascapular nerve injury impacts the supraspinatus and infraspinatus muscles, affecting the initiation of abduction and external rotation of the arm.
• Injury to the long thoracic nerve results in a winged scapula due to paralysis of the serratus anterior muscle.
• The inability to abduct the arm beyond 90 degrees is indicative of a serratus anterior injury.

Volkmann's Contracture

• Volkmann's contracture is a flexion deformity of the wrist and fingers, resulting from ischemia and necrosis of forearm muscles.
• It is typically caused by compartment syndrome, often due to a fracture in the elbow region.
• The median nerve is affected, leading to sensory loss and motor weakness in the hand.

Radius and Ulna

• The radius and ulna are two bones in the forearm.
• The radius is located laterally, while the ulna is located medially.
• The radius is the main bone involved in wrist joint formation, while the ulna is primarily involved in elbow joint formation.
• The proximal end of the ulna includes the olecranon and coronoid processes.
• The olecranon process fits into the olecranon fossa of the humerus during arm extension.
• The coronoid process articulates with the trochlea of the humerus.
• The radial notch on the ulna articulates with the head of the radius, forming the proximal radioulnar joint.
• The distal end of the radius articulates with the carpal bones to form the wrist joint.
• The distal end of the ulna forms the head, which articulates with the ulnar notch of the radius.

Fractures

• Colles' fracture is a fracture of the distal radius, commonly caused by a fall on an outstretched hand.
• It results in a "dinner fork" deformity due to dorsal displacement of the distal fragment.
• Smith's fracture is a fracture of the distal radius with volar (palmar) displacement of the distal fragment.
• Greenstick fractures are incomplete fractures that occur in children due to their more flexible bones.