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The infraspinatus muscle: a proposed classification system
Krzysztof Koptas1, Łukasz Olewnik2, Bartłomiej Szewczyk3
1Department of Anatomical Dissection and Donation, Medical University of Lodz, Łódź, Poland.
Folia Morphologica
|July 29, 2025
Summary
The infraspinatus muscle, part of the rotator cuff, shows significant morphological variability. Our study identified two common types, highlighting differences in its belly structure for anatomical and surgical reference.
Area of Science:
- Anatomy
- Orthopedics
- Surgical Anatomy
Background:
- The infraspinatus muscle is a key component of the rotator cuff, crucial for shoulder joint stability and function.
- It originates from the infraspinous fossa and typically inserts onto the greater tubercle of the humerus.
- Understanding its anatomical variations is essential for effective clinical practice.
Purpose of the Study:
- To investigate the morphological variability of the infraspinatus muscle, specifically focusing on its belly structure.
- To classify the identified variations for improved anatomical understanding and surgical planning.
Main Methods:
- Dissection and examination of 91 upper limbs (46 left, 45 right) preserved in formalin.
- Systematic analysis of the infraspinatus muscle's origin, insertion, and belly configuration.
Main Results:
- Two distinct morphological types of the infraspinatus muscle were identified.
- Type I (76.92%) presented with a single muscle belly inserting onto the greater tubercle.
- Type II (23.08%) exhibited two separate bellies originating from different parts of the infraspinous fossa and inserting onto the greater tubercle.
Conclusions:
- The infraspinatus muscle demonstrates significant morphological variability in the number of its bellies.
- This anatomical classification provides valuable insights for surgeons operating on the rotator cuff and for anatomists.
- Recognizing these variations can enhance surgical precision and reduce potential complications.
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