Anatomy of the Clavicle

Study Notes

Trapezoid line: Attachment point for the lateral part of the coracoclavicular ligament.
Subclavian groove: Located on the medial third of the clavicle; serves as the attachment for the subclavius muscle.
Impression for costoclavicular ligament: A rough, oval area providing attachment for the ligament connecting the first rib to the clavicle, which limits shoulder elevation.

Shape: Triangular, flat bone covering the 2nd to 7th ribs on the posterolateral thorax.
Surfaces:
- Posterior: Convex, divided into supraspinous fossa (smaller) and infraspinous fossa (larger) by the spine of scapula.
- Costal: Concave, forming the large subscapular fossa for muscle attachment.

Body of scapula: Thin and translucent above and below the spine, with thicker borders, especially laterally.
Acromion: Flat expansion of the scapular spine, articulates with the clavicle, serving as the shoulder's subcutaneous point.
Deltoid tubercle: Medial attachment site for the deltoid muscle located on the scapular spine.
Spine of scapula: Acts as a lever for trapezius muscle alongside the acromion.
Glenohumeral joint: Positioned inferior to the ac joint; allows for shoulder movement and balance in conjunction with the CC ligament.
Glenoid cavity: Oval fossa on the scapula that articulates with the head of the humerus, providing a shallow socket.
Coracoid process: Beak-like projection above the glenoid cavity that supports the CC ligament and resembles a bent finger.
Borders: The scapula has three borders (medial, lateral, superior) with distinct characteristics,
- Medial border runs parallel to thoracic spine.
- Lateral border is thicker, preventing buckling under stress, and terminates in a robust head.
- Superior border is thin and short, marked by the suprascapular notch.

Facilitates considerable movement on the thoracic wall at the scapulothoracic joint, enabling upper limb mobility.

Sternoclavicular joint: A saddle-type synovial joint functioning like a ball and socket; features an articular disc dividing it into compartments.
Disc attachments: Strengthened by anterior, posterior sternoclavicular, and interclavicular ligaments.
Shock absorption: The joint absorbs forces from the upper limb; dislocations are rare, but fractures occur more frequently.
Articular surfaces: The sternal end of the clavicle articulates with the manubrium of the sternum and the first costal cartilage, both covered with fibrocartilage.

Shape: S-shaped with convex medial and concave lateral curvatures, enhancing resilience.
Ends of the clavicle:
- Sternal end: Enlarged and triangular, articulates with the sternum at the SC joint.
- Acromial end: Flat, articulates with the acromion of the scapula at the AC joint.
Functions:
- Acts as a movable strut supporting the scapula and limb for maximum range of motion.
- Forms a boundary of the cervico-axillary canal, safeguarding neurovascular bundles.
- Transmits shocks from the upper limb to the axial skeleton.
Composition: Long bone without a medullary cavity; trabecular bone encased in compact bone.
Surface characteristics:
- Superior surface: Smooth and located beneath skin and platysma muscle.
- Inferior surface: Rough due to ligaments securing it to the first rib and suspending the scapula.

Conoid tubercle: Near the acromial end; attaches to the conoid ligament, allowing passive suspension of the upper limb from the clavicle.

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