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Pectoralis minor muscle

The pectoralis minor muscle is a thin, triangular muscle of the anterior thoracic wall. It lies deep to the pectoralis major muscle, extending from the ribs to the scapula. It originates from the anterior surfaces of the 3rd to 5th ribs near their costal cartilages, and inserts onto the coracoid process of the scapula.

This muscle is covered by the clavipectoral fascia and plays an important role in scapular movement and stabilization. It pulls the scapula anteriorly and inferiorly against the thoracic wall, assisting in movements such as protraction and depression of the scapula.

The pectoralis minor also acts as an accessory muscle of inspiration by elevating the ribs when the scapula is fixed. It is closely related to the neurovascular bundle of the axilla, and hypertrophy or spasm can contribute to thoracic outlet syndrome by compressing the brachial plexus or axillary vessels.

Synonyms

  • Musculus pectoralis minor

  • Lesser pectoral muscle

Function

  • Stabilizes the scapula by drawing it anteriorly and inferiorly against the thoracic wall

  • Assists in scapular protraction and depression

  • Functions as an accessory respiratory muscle, elevating the ribs when scapula is fixed

  • Important in thoracic outlet syndrome pathology due to its anatomical relations

MRI Appearance

T1-weighted images:

  • Muscle belly shows intermediate signal intensity

  • Cortical bone of ribs and coracoid appears hypointense; surrounding fat is hyperintense

T2-weighted images:

  • Normal muscle: intermediate signal

  • Pathology: edema, inflammation, or tear appears hyperintense relative to normal fibers

STIR:

  • Suppresses fat signal, highlighting muscle edema, strain, or myositis as hyperintense regions

  • Excellent for evaluating thoracic outlet compression

T1 Post-Gadolinium (Gd-enhanced MRI):

  • Enhances in myositis, tumors, or vascular compression

  • Useful for detecting soft tissue mass or neoplastic infiltration

  • Enhances clavipectoral fascia when inflamed

MRI Non-Contrast 3D Imaging:

  • Demonstrates course of the muscle from ribs to coracoid process

  • Useful in preoperative mapping for thoracic outlet decompression

CT Appearance

Non-contrast CT:

  • Shows pectoralis minor as a soft-tissue density deep to pectoralis major

  • Useful for identifying calcifications, trauma, or atrophy

CT Post-Contrast:

  • Muscle enhances moderately and homogeneously

  • Surrounding neurovascular compression or masses become more conspicuous

  • Multiplanar reformats delineate its relation to axillary vessels and brachial plexus

MRI image

Pectoralis minor muscle anatomy MRI coronal image -img-00000-00000

CT image

Pectoralis minor muscle anatomy CT axial image -img-00000-00000

MRI image

Pectoralis minor muscle axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Pectoralis minor muscle sag cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Pectoralis minor muscle axial shoulder ct