Normal Supraspinatus and Infraspinatus Insertions
1. Overlapping Anatomy
- The anterior infraspinatus partially covers the posterolateral supraspinatus.
- This overlap suggests biomechanical significance in shoulder abduction, especially in cases of isolated supraspinatus tears.
2. Supraspinatus and Infraspinatus Footprints
- Supraspinatus: Inserts into the anteromedial area of the highest impression of the greater tuberosity and, occasionally, into the lesser tuberosity (21% of shoulders).
- Infraspinatus: Inserts into the anteriormost region of the greater tuberosity, nearly reaching the anterior margin of the highest impression.
3. Rotator Cuff Footprint Dimensions
- Supraspinatus: Triangular footprint measuring 6.9 mm × 12.6 mm, located within 1 mm of the articular margin.
- Infraspinatus: Trapezoidal footprint measuring 10.2 mm × 32.7 mm, with a more lateral insertion relative to the articular surface.
4. Shared Tendon Insertions
- Mochizuki et al. identified that the supraspinatus occupies only the anterior 1.3 mm of the rotator cuff footprint, while the following 11.3 mm consists of overlapping supraspinatus and infraspinatus regions.
5. Joint Capsule Contributions
- The joint capsule attaches beneath the supraspinatus, infraspinatus, and superior teres minor tendons at the greater tuberosity.
- The capsule attachment is thick near the anterior supraspinatus and posterior infraspinatus but thinner near the middle supraspinatus region.
#Supraspinatus, #Infraspinatus, #RotatorCuff, #ShoulderAnatomy, #Biomechanics, #TendonInsertions, #JointCapsule, #OrthopedicRadiology, #ShoulderAbduction, #SportsMedicine
References
- Mochizuki et al., J Bone Joint Surg Am. 2008 May; 90(5):962-9.
- J Bone Joint Surg Am. 2010 May; 92(5):1088-96.
- Magn Reson Imaging Clin N Am. 2012 May; 20(2):163-72, ix.
- JBJS Rev. 2024 Aug 26; 12(8).
- Nimura et al., J Shoulder Elbow Surg. 2012 Jul; 21(7):867-72.
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