The scapular notch, also known as the suprascapular notch, is a distinctive, deep, and semicircular indentation located on the superior border of the scapula (shoulder blade), specifically positioned at its lateral part. This crucial anatomical landmark is partly formed by the base of the coracoid process.
Anatomy and Significance of the Scapular Notch
The scapular notch plays a vital role in the passage of a significant nerve, making it a key area in shoulder anatomy. Its structure and associated ligaments are critical for the function and potential clinical issues of the shoulder complex.
Location and Formation
- Location: Found on the superior border of the scapula, closer to the lateral angle.
- Formation: It is a concavity that is specifically shaped by the bone itself and is partly defined by the origin point of the coracoid process, which projects anteriorly from the scapula.
Conversion into a Foramen
A key feature of the scapular notch is its transformation into a complete opening or foramen. This occurs due to the presence of the superior transverse scapular ligament (also known as the suprascapular ligament). This ligament stretches across the notch, effectively converting the "U" or "V" shape of the notch into a closed "O" or "D" shaped foramen.
Passage of the Suprascapular Nerve
The primary function of the foramen created by the scapular notch and the superior transverse scapular ligament is to provide a protected pathway for the suprascapular nerve. This nerve is essential for motor innervation to the supraspinatus and infraspinatus muscles (two of the rotator cuff muscles) and sensory innervation to the shoulder joint.
- Nerve Passage: The suprascapular nerve passes through this foramen.
- Vessel Passage: Importantly, the suprascapular artery and vein typically pass over the superior transverse scapular ligament, not through the foramen with the nerve.
Clinical Relevance
Understanding the scapular notch is clinically important due to its association with suprascapular nerve entrapment syndrome.
- Nerve Compression: The suprascapular nerve can be compressed or impinged as it passes through the narrow foramen.
- Causes of Entrapment: This can be caused by:
- Thickening or calcification of the superior transverse scapular ligament.
- Trauma to the shoulder.
- Repetitive overhead activities (e.g., in athletes).
- Cysts (e.g., paralabral cysts) that can put pressure on the nerve.
- Sometimes, the superior transverse scapular ligament itself can ossify (turn into bone), creating a rigid bony tunnel that can further increase the risk of nerve compression.
- Symptoms: Entrapment can lead to pain in the posterior or superolateral shoulder, weakness, and atrophy of the supraspinatus and infraspinatus muscles, potentially limiting shoulder movement and strength.
Key Features of the Scapular Notch
Here's a summary of the essential characteristics of the scapular notch:
| Feature | Description | Clinical Significance |
|---|---|---|
| Location | Lateral part of the superior border of the scapula | Defines pathway for neurovascular structures |
| Shape | Deep, semicircular indentation | Forms a protective groove |
| Formation Contribution | Partially formed by the base of the coracoid process | Anatomical landmark for surrounding structures |
| Ligament Conversion | Converted into a foramen by the superior transverse scapular ligament | Creates a narrow passage for the suprascapular nerve |
| Nerve Passage | Serves as the pathway for the suprascapular nerve | Site of potential nerve entrapment |
| Ossification Risk | Superior transverse scapular ligament can sometimes ossify | Increases risk of nerve compression due to rigid tunnel |
Related Anatomical Structures
The scapular notch is part of a complex anatomical region involving several key structures of the shoulder girdle:
- Scapula: The triangular bone forming the back of the shoulder.
- Coracoid Process: A hook-like bony projection from the scapula, serving as an attachment point for muscles and ligaments.
- Superior Transverse Scapular Ligament: A fibrous band that bridges the scapular notch.
- Suprascapular Nerve: A mixed peripheral nerve originating from the brachial plexus, critical for shoulder function.
- Supraspinatus Muscle: One of the rotator cuff muscles, located above the spine of the scapula.
- Infraspinatus Muscle: Another rotator cuff muscle, located below the spine of the scapula.
