Anatomy of the Clavicle and Upper Limb

The clavicle, or collar bone, is a long bone with a slight S-shaped curve. It's located horizontally on the anterior aspect of the body, where the neck meets the trunk.

The clavicle plays a crucial role in holding the upper limb away from the trunk, allowing for free movement and various gripping actions.

The clavicle transmits forces from the upper limb to the axial skeleton, particularly the sternum, helping to distribute weight and impact.

The clavicle provides a surface for attachment of various muscles that control movement in the shoulder and neck.

As the clavicle lies horizontally across the body, it distinguishes itself as the only long bone with this orientation.

The clavicle is exceptional in that it lacks a medullary cavity, which is typically present in long bones.

The clavicle is easily felt, or palpated, along its entire length as it lies just beneath the skin, making it easy to locate.

The clavicle is the first bone of the human body to start ossification (forming bone) during fetal development and the last to complete the process.

The medial two-thirds of the clavicle shaft is curved and convex forward, while the lateral one-third is flattened and concave forward.

The inferior surface of the clavicle shaft has a longitudinal groove in its middle third.

The lateral end of the clavicle is flattened, with an oval facet that articulates with the acromion to form the acromioclavicular joint.

The medial end of the clavicle is enlarged and saddle-shaped. It articulates with the clavicular notch of the manubrium sterni to form the sternoclavicular joint.

The lateral one-third of the clavicle shaft is flattened from above and has two surfaces (superior and inferior) and two borders (anterior and posterior).

The superior surface of the lateral one-third of the clavicle shaft is subcutaneous, meaning it's located just beneath the skin, between the attachments of the deltoid and trapezius muscles.

The inferior surface of the lateral one-third of the clavicle shaft features the conoid tubercle and trapezoid ridge, which provide attachments for the coracoclavicular ligament.

The anterior border of the lateral one-third of the clavicle shaft is concave forward and gives origin to the deltoid muscle. A small tubercle called the deltoid tubercle may be present on this border.

The medial two-thirds of the clavicle is cylindrical and has four surfaces: anterior, posterior, superior, and inferior.

The clavicular head of the pectoralis major muscle originates from the anterior surface of the medial two-thirds of the clavicle.

The sternohyoid muscle attaches to the posterior surface of the medial two-thirds of the clavicle, near its medial end.

The clavicular head of the sternocleidomastoid muscle originates from the medial half of the superior surface of the medial two-thirds of the clavicle.

The costoclavicular ligament attaches to an oval impression on the medial end of the inferior surface of the medial two-thirds of the clavicle.

The subclavius muscle inserts into the subclavian groove on the inferior surface of the medial two-thirds of the clavicle.

The clavicle is the most commonly fractured bone in the body. It is prone to fracture at the junction of its lateral one-third and medial two-thirds.

The clavicle is the most commonly fractured bone in the body, often due to blows to the shoulder or forces transmitted from the hand or shoulder.

The suprascapular notch is transformed into an opening called the suprascapular foramen by the superior transverse ligament, also known as the suprascapular ligament.

The suprascapular artery travels above this ligament, while the suprascapular nerve passes underneath it, through the suprascapular foramen.

The inferior belly of the omohyoid muscle originates from the superior border of the scapula, close to the suprascapular notch.

The lateral border of the scapula is the thickest and acts like a pivot during scapular rotation, stretching from the inferior angle to the glenoid cavity.

The infraglenoid tubercle, a bump located just below the glenoid cavity on the lateral border, serves as the origin for the long head of the triceps muscle.

The medial border, also known as the vertebral border, stretches from the superior angle to the inferior angle. It's thinner and angled at the base of the scapular spine.

The serratus anterior muscle attaches to the costal (rib) side of the medial border and the inferior angle.

The levator scapulae muscle attaches to the back of the medial border, from the superior angle to the base of the spine.

The head of the radius is a disc-shaped structure covered in articular cartilage, allowing it to connect with the capitulum of the humerus to form the humero-radial joint.

The radial neck is a narrow section below the head, surrounded by the annular ligament and the quadrate ligament.

The radial tuberosity is a rough projection on the radius where the biceps tendon attaches. It has a smooth anterior part covered by a bursa.

The radial shaft is the main body of the radius, with three borders (anterior, posterior, and medial) and three surfaces (anterior, posterior, and lateral).

The anterior border starts below the radial tuberosity and extends downwards, forming the anterior oblique line and the sharp lateral border of the anterior surface.

The posterior border is well-defined in the middle part of the shaft, running upwards and medially to form the posterior oblique line.

The interosseous border of the radius is the sharpest border. It extends from the radial tuberosity to the lower end, forming the posterior margin of a triangular area on the medial side.

The anterior surface of the radius is concave and located between the anterior and interosseous borders. It is the origin for some flexor muscles and receives the pronator quadratus muscle.

The middle one-third of the radial shaft's posterior surface provides attachment for the abductor pollicis longus (APL) muscle, which helps with thumb abduction.

The lower part of the radial shaft's posterior surface serves as the origin for the extensor pollicis brevis (EPB) muscle, which helps with thumb extension.

The supinator muscle, which rotates the forearm outward, inserts on the widened upper one-third of the radial shaft's lateral surface.

The pronator teres muscle, responsible for rotating the forearm inward, inserts on the rough area in the middle part of the radial shaft's lateral surface.

The lower end of the radius, the widest part of the bone, has five surfaces, including the anterior surface, which presents a thick ridge providing attachment for the palmar radio-carpal ligament of the wrist joint.

The posterior surface of the radius' lower end possesses the dorsal tubercle of Lister, a bony prominence lateral to the groove for the extensor pollicis longus tendon, and features grooves for other extensor tendons.

The medial surface of the radius' lower end presents the ulnar notch, articulating with the head of the ulna, and serves as the attachment point for the articular disc of the inferior radio-ulnar joint.

The lateral surface of the radius' lower end extends downwards as the styloid process, serving as the attachment site for tendons involved in thumb movement and providing attachment for the brachioradialis muscle and the radial collateral ligament of the wrist joint.