Five Histologic Layers of the Supraspinatus and Infraspinatus Tendons
1. Layer 1: Superficial Layer
- Thickness: ~1 mm
- Composed of fibers from the coracohumeral ligament.
2. Dense Parallel Tendon Fibers
- Thickness: 3–5 mm
- Densely packed parallel collagen fibers.
- Stronger than layer 3 by twofold.
- Prone to intrasubstance tears between this layer and layer 3.
3. Deep Layer with Non-Uniform Collagen Orientation
- Thickness: ~3 mm
- Smaller collagen bundles arranged at 45° angles.
- Forms the common site for delamination tears.
4. Loose Connective Tissue
- Contains thick collagen bands.
- Merges with the coracohumeral ligament along the anterior edge of the supraspinatus tendon.
5. Joint Capsule
- Thickness: 1.5–2 mm
- Formed by the joint capsule, attaching to the greater tuberosity through Sharpey fibers.
Key Imaging and Observations
- Intrasubstance Tears: Often occur along the shear plane between layers 2 and 3.
- MRI Appearance:
- Rotator Cable: Seen on MRI as a low-signal band close to the articular surface, running perpendicular to the supraspinatus and infraspinatus tendons.
Hashtags
#Supraspinatus, #Infraspinatus, #RotatorCuff, #HistologicLayers, #ShoulderAnatomy, #MRIFindings, #RotatorCable, #CollagenTears, #MSKRadiology, #ShoulderMRI
References
- Magn Reson Imaging Clin N Am. 2012 May; 20(2):163-72, ix.
- Magn Reson Imaging Clin N Am. 2012 May; 20(2):187-200.
