Body of the Scapula: Anatomy, Relations, Function, Imaging

Topic

Body of scapula

The body of the scapula forms the large, flat, triangular portion of the scapular bone, providing the broad central area that supports the shoulder girdle. It lies on the posterolateral thoracic wall, typically spanning the second to seventh ribs. The body provides wide surfaces for muscle attachment, acts as a load-transmitting structure between the upper limb and trunk, and plays a key role in shoulder mobility and stability.

The body is thin and translucent centrally, but thicker near the spine, glenoid cavity, and borders, where muscle and ligament attachments concentrate mechanical stress. The posterior surface is divided by the spine of the scapula into the supraspinous and infraspinous fossae, while the anterior (costal) surface forms the subscapular fossa.

Synonyms

Corpus scapulae
Scapular blade
Scapular body

Location and Structure

Shape: Flat, triangular plate forming the main portion of the scapula.
Surfaces:
- Costal (anterior) surface: Concave, forming the subscapular fossa; origin of the subscapularis muscle.
- Posterior surface: Divided by the spine of the scapula into:
  - Supraspinous fossa: For supraspinatus muscle.
  - Infraspinous fossa: For infraspinatus muscle.
Borders:
- Superior border: Short, with suprascapular notch transmitting the suprascapular nerve.
- Medial (vertebral) border: Parallel to vertebral column; attachment for rhomboids and serratus anterior.
- Lateral (axillary) border: Thick, giving attachment to teres minor and major.
Angles:
- Superior angle: Level of 2nd rib; attachment for levator scapulae.
- Inferior angle: Level of 7th rib; insertion of latissimus dorsi.
- Lateral angle: Bears the glenoid cavity and neck of scapula.

Relations

Anteriorly: Serratus anterior and thoracic cage (ribs and intercostal muscles).
Posteriorly: Trapezius, supraspinatus, infraspinatus, teres minor, teres major, and deltoid muscles.
Laterally: Shoulder joint capsule, axillary vessels, and brachial plexus.
Medially: Rhomboid major, rhomboid minor, and posterior thoracic wall.

Attachments

Subscapularis: Entire anterior (costal) surface.
Supraspinatus: Supraspinous fossa.
Infraspinatus: Infraspinous fossa.
Teres minor and major: Lateral border.
Serratus anterior: Medial border (costal side).
Rhomboids and levator scapulae: Medial border (posterior side).
Deltoid and trapezius: Along spine and acromion.

Nerve Supply

Periosteal sensory branches from:
- Suprascapular nerve (superior region)
- Dorsal scapular nerve (medial border)
- Axillary nerve (lateral border and glenoid region)

Arterial Supply

Suprascapular artery (branch of thyrocervical trunk): supplies supraspinous and infraspinous regions.
Subscapular artery (branch of axillary artery): supplies subscapular fossa and lateral border.
Circumflex scapular artery (branch of subscapular artery): passes through the triangular space to supply the infraspinous fossa and posterior scapular surface.
Dorsal scapular artery (from subclavian artery): supplies the medial border and adjacent muscles.

Venous Drainage

Suprascapular vein drains the supraspinous and infraspinous regions into the external jugular vein.
Subscapular and circumflex scapular veins drain into the axillary vein.
Dorsal scapular vein drains along the medial border into the subclavian vein.

Function

Muscle attachment: Provides origin and insertion points for key shoulder muscles.
Shoulder mechanics: Serves as a stable platform for humeral movement and rotation.
Load transmission: Transfers muscle forces from upper limb to thoracic cage.
Protection: Shields underlying thoracic structures and neurovascular bundles.
Joint contribution: Forms part of the glenoid region for articulation with the humeral head.

Clinical Significance

Fractures: Often result from direct trauma or high-velocity impact; may be associated with rib or clavicle fractures.
Stress injury: Overuse or repetitive motion can cause scapular stress fractures in athletes.
Winged scapula: Results from paralysis of serratus anterior or trapezius due to nerve injury.
Osteolytic lesions or tumors: Can occur from metastasis, osteoid osteoma, or sarcoma.
Imaging relevance: MRI evaluates marrow and soft tissue; CT is essential for fracture characterization and bone pathology.

MRI Appearance

T1-weighted images:
- Cortex: Low signal (dark).
- Marrow: Bright, fatty signal (normal adult marrow).
- Muscles: Intermediate signal.
- Periosteum: Thin low-signal line along cortex.
- Fractures: Linear low-signal lines through cortex; marrow edema appears intermediate-to-bright.
T2-weighted images:
- Cortex: Low signal.
- Marrow: Bright, reflecting fat and/or mild vascular marrow.
- Muscle: Intermediate-to-low; darker than T1.
- Pathology: Edema, contusion, or tumor infiltration appear hyperintense.
STIR:
- Normal marrow: Intermediate-to-dark signal.
- Pathology: Bright hyperintense marrow in edema, infection, or stress fracture.
- Highlights early bone and soft-tissue inflammation.
Proton Density Fat-Saturated (PD FS):
- Normal marrow: Intermediate-to-dark signal.
- Pathology: Bright hyperintensity indicating marrow edema or cortical disruption.
- Excellent for small fractures and periosseous soft-tissue assessment.
T1 Fat-Sat Post-Contrast:
- Normal scapula: Mild uniform enhancement.
- Infection or tumor: Patchy, nodular, or diffuse enhancement.
- Post-traumatic changes: Peripheral rim enhancement with central low-signal hematoma or fibrosis.

CT Appearance

Non-Contrast CT:

Cortex: High attenuation, sharp, well-defined margins.
Trabecular bone: Fine honeycomb pattern with thin septae.
Fossae: Subscapular, supraspinous, and infraspinous fossae clearly delineated.
Pathology: Fractures, cortical erosion, osteolysis, and sclerosis are well visualized.
3D reconstruction: Excellent for preoperative evaluation of fracture geometry.

Post-Contrast CT (standard):

Bone: Minimal enhancement; periosteum or soft tissues may enhance in inflammatory or neoplastic conditions.
Applications:
- Detecting osteomyelitis, metastasis, or tumor extension.
- Assessing healing fractures and peri-scapular soft-tissue abnormalities.