Muscle Attachments

• Medially: the pectoralis major muscle originates from the clavicular shaft anteroinferiorly, and the sternocleidomastoid originates superiorly.

• Laterally: the pectoralis origin merges with the origin of the anterior deltoid, while the trapezius insertion blends superiorly with the deltoid origin at the lateral margin.

• The medial clavicular fragment is elevated by the unopposed pull of the sternocleidomastoid muscle, while the distal fragment is held inferiorly by the deltoid and medially by the pectoralis major.

• The platysma or “shaving muscle” is variable in terms of thickness and extent, but usually envelopes the anterior and superior aspects of the clavicle and runs in the subcutaneous tissues, extending superiorly to the mandible and the deeper facial muscles. It is divided during the surgical approach, and is typically included in the closure of the superficial, or skin/subcutaneous layer.