Clark and Harryman described the gross and microscopic structure of the rotator cuff tendons, the ligaments and the capsule.
Cadaver study of 32 grossly intact cuffs from 30 fresh cadavers, ages 17 to 72 at death.
Methods
Specimens
80 shoulders from 78 fresh cadavers collected
48 excluded for cuff tears or thinning found at dissection
32 grossly intact cuffs from 30 cadavers studied, ages 17 to 72 at death
Method
13 fixed and decalcified en bloc for sections through tendon and bone
10 removed and pinned flat before fixation, 3 of them studied by scanning electron microscopy
9 dissected fresh, layer by layer, to trace tendons, ligaments and capsule
Measurements
Layer thickness
Fiber orientation and attachment
Vessel size and signs of degeneration
Key Findings
All four cuff tendons merge into one continuous insertion on the humeral tuberosities rather than inserting separately.
Supraspinatus and infraspinatus join about 15 mm proximal to their humeral insertions, and blunt dissection could not separate them.
The two tendons look fused because their fibers interdigitate in layer 3, where fascicles cross one another at 45°.
The biceps sheath is woven from subscapularis and supraspinatus fibers, and its deep portion lines the bicipital groove as fibrocartilage for about 7 mm.
A cuff tear may be hidden by the coracohumeral ligament on the bursal side or by the capsule on the articular side, which matters when reading MRI, ultrasound or arthroscopy.
About half of the grossly intact cuffs had small foci of calcification or acellular areas, and signs of degeneration were not confined to one age group.
Board pearl
The coracohumeral ligament reinforces the supraspinatus from both sides, with its fibers forming the thin 1 mm superficial layer and also gathering in the plane between the capsule and the tendons.
Authors' conclusion
Therefore, lesions in the area of the supraspinatus tendon may involve one or more of these elements, and the evolution of a tear in this area may be determined by the location of the initial lesion.
Clark and Harryman described the gross and microscopic structure of the rotator cuff tendons, the ligaments and the capsule.
Cadaver study of 32 grossly intact cuffs from 30 fresh cadavers, ages 17 to 72 at death.
Methods
Specimens
80 shoulders from 78 fresh cadavers collected
48 excluded for cuff tears or thinning found at dissection
32 grossly intact cuffs from 30 cadavers studied, ages 17 to 72 at death
Method
13 fixed and decalcified en bloc for sections through tendon and bone
10 removed and pinned flat before fixation, 3 of them studied by scanning electron microscopy
9 dissected fresh, layer by layer, to trace tendons, ligaments and capsule
Measurements
Layer thickness
Fiber orientation and attachment
Vessel size and signs of degeneration
Key Findings
All four cuff tendons merge into one continuous insertion on the humeral tuberosities rather than inserting separately.
Supraspinatus and infraspinatus join about 15 mm proximal to their humeral insertions, and blunt dissection could not separate them.
The two tendons look fused because their fibers interdigitate in layer 3, where fascicles cross one another at 45°.
The biceps sheath is woven from subscapularis and supraspinatus fibers, and its deep portion lines the bicipital groove as fibrocartilage for about 7 mm.
A cuff tear may be hidden by the coracohumeral ligament on the bursal side or by the capsule on the articular side, which matters when reading MRI, ultrasound or arthroscopy.
About half of the grossly intact cuffs had small foci of calcification or acellular areas, and signs of degeneration were not confined to one age group.
Board pearl
The coracohumeral ligament reinforces the supraspinatus from both sides, with its fibers forming the thin 1 mm superficial layer and also gathering in the plane between the capsule and the tendons.
Authors' conclusion
Therefore, lesions in the area of the supraspinatus tendon may involve one or more of these elements, and the evolution of a tear in this area may be determined by the location of the initial lesion.