Paul McMenamin; Week 1 MED1022; Anatomy
Clavicle is the first bone to begin ossification and the last to finish, with its lateral end being intramembranous in ossification and its medial end endochondral. The upper part of the clavicle is smooth. It usually fractures between its medial 1/3 and lateral 2/3. It attaches to the sternum by the sternoclavicular joint and the acromion with the acromioclavicular joint.
The scapula has 9 centres of ossification and is a flat bone.
The fibrous capsule is composed of interlaced collagen bundles in a cuff-like formation, prevents unwanted movements. Parallel fibres have intracapsular thickenings. Tendons may blend with the capsule, and the whole formation is strengthened by extracapsular ligaments. The shoulder flexes, extends, abducts, adducts, medially and laterally rotates as well as circumducts. Full abduction is possible by laterally rotating the humerus. Beer can tests for subacromial bursitis.
Cervicoaxillary canal is passage made by the clavicle and the first rib. This is where the brachial plexus passes through. The shoulder is generally innervated by C5 and 6 (some C7) but also spinal part of accessory nerve (roots C1-5, SCM, trapezius).
Injury to long thoracic nerve causes winging of scapula, common after axillary surgery such as in lymph node clearance after breast cancer surgery.