Superior Transverse Scapular Ligament: Anatomy, Function, Imaging

Topic

Superior transverse scapular ligament

The superior transverse scapular ligament (STSL) is a strong fibrous band spanning the suprascapular notch of the scapula, converting the notch into a foramen through which the suprascapular nerve passes. This ligament plays a crucial role in stabilizing neurovascular structures around the superior border of the scapula and serves as a landmark in both orthopedic and radiological anatomy of the shoulder region.

The ligament’s morphology is variable—it may be thin, thick, ossified, or bifid—and such variations are clinically relevant, particularly in suprascapular nerve entrapment syndrome. Ossification of the ligament can transform the notch into a bony foramen, compressing the suprascapular nerve and leading to shoulder weakness or atrophy.

Synonyms

Suprascapular ligament
Transverse scapular ligament

Location and Attachments

Location: Situated on the superior border of the scapula at the suprascapular notch, near the base of the coracoid process.
Attachments:
- Medially: Attached to the medial margin of the suprascapular notch.
- Laterally: Attached to the lateral border of the notch, near the root of the coracoid process.
The ligament converts the suprascapular notch into a foramen, transmitting the suprascapular nerve beneath it, while the suprascapular vessels usually pass above it.

Morphological Variations

Thin or membranous (most common, flexible band)
Thickened or cord-like (may predispose to nerve compression)
Partial ossification: Forms a semi-osseous arch
Complete ossification: Converts notch into a bony foramen
Bifid ligament: Two distinct bands creating dual foramina

Relations

Superiorly: Suprascapular artery and vein (typically above the ligament)
Inferiorly: Suprascapular nerve (passing below the ligament through the foramen)
Medially: Superior angle of scapula
Laterally: Coracoid process and root of supraspinatus fascia
Posteriorly: Trapezius and supraspinatus muscles
Anteriorly: Clavicle and subclavius muscle (at higher level)

Function

Stabilization: Converts the suprascapular notch into a fibro-osseous foramen that protects and stabilizes the suprascapular nerve.
Protection: Shields neurovascular structures from mechanical friction during shoulder motion.
Anatomic landmark: Serves as a key guide in surgical and arthroscopic approaches to the suprascapular region.
Clinical significance: Variations or ossification can compress the suprascapular nerve, leading to neuropathy.

Clinical Significance

Suprascapular nerve entrapment: Caused by thickened, ossified, or bifid ligament compressing the nerve beneath it.
Symptoms: Shoulder pain, weakness in abduction and external rotation, and atrophy of supraspinatus and infraspinatus muscles.
Ossification: May appear as a bony bridge over the suprascapular notch on imaging.
Iatrogenic injury: Risk during arthroscopic shoulder decompression or surgery.
Imaging relevance: MRI and CT are key for identifying ligament morphology, ossification, and associated nerve impingement.

MRI Appearance

T1-weighted images:
- Ligament appears as a thin, low-signal (dark) linear band spanning the suprascapular notch.
- Surrounding fat: bright, delineating ligament margins clearly.
- Ossified portions: very low signal due to cortical bone.
- Adjacent suprascapular nerve: small intermediate-signal tubular structure beneath the ligament.
T2-weighted images:
- Ligament: dark low-signal line contrasting with surrounding bright soft tissues.
- Ossification: low to no signal (signal void).
- Entrapment signs: Nerve edema shows focal hyperintense signal distal to compression.
- Adjacent muscle changes: Early denervation of supraspinatus/infraspinatus shows mild hyperintensity.
STIR:
- Normal ligament: dark, low-signal band.
- Pathologic findings: bright hyperintensity in periligamentous tissue indicating inflammation or nerve irritation.
- Denervated muscle: bright signal intensity from edema or atrophy.
Proton Density Fat-Saturated (PD FS):
- Ligament: thin, dark band across suprascapular notch.
- Edematous or fibrotic changes: focal bright signal adjacent to ligament.
- Useful for evaluating nerve compression and periligamentous inflammation.
T1 Fat-Sat Post-Contrast:
- Normal ligament: no enhancement.
- Inflamed or thickened ligament: mild peripheral enhancement.
- Surrounding soft-tissue enhancement may indicate bursitis, neuritis, or postoperative scar tissue.

CT Appearance

Non-Contrast CT:

Ligament (non-ossified): may appear as a thin soft-tissue density across the suprascapular notch.
Ossified ligament: clearly visible as a bony bridge converting the notch into a foramen.
Provides excellent delineation of osseous morphology and notch variations.
Entrapment correlation: narrowing of the foramen and adjacent bony ridges suggest potential nerve compression.

Post-Contrast CT (standard):

Ligament itself does not enhance.
Surrounding soft-tissue enhancement: may indicate inflammation or post-traumatic change.
Excellent for evaluating ossified ligament morphology and relationship to suprascapular notch and coracoid process.

MRI image

Topics