Harryman and colleagues examined how the rotator interval capsule, which spans the gap between supraspinatus and subscapularis, contributes to glenohumeral motion, translation and stability.
Cadaver study of 8 shoulders, each tested intact, after sectioning and after imbrication.
Methods
Model
8 cadaver shoulders
Constructs
Intact rotator interval capsule
Sectioned capsule
Imbricated capsule
Loading
Applied loads tracked with a 6‑degrees‑of‑freedom position sensor and force‑torque transducer
Anterior, posterior and inferior stress tests
Outcome measures
Glenohumeral range of motion
Obligate translation during flexion
Translation and stability on stress testing
Key Findings
After sectioning, a posterior force with the arm in 60° abduction and 60° external rotation dislocated the joint posteroinferiorly in 4 of 8 specimens, and allowed posterior translation rose by 6.1 mm (p < 0.05).
Imbrication cut posterior drawer translation by 7.3 to 8.3 mm across the three tested arm positions and inferior sulcus translation by 7.7 mm (all p < 0.05).
Sectioning reduced the obligate anterior translation on flexion by 4.2 mm, while imbrication increased it by 4.9 mm and added 3.5 mm of superior translation (all p < 0.05).
After sectioning, inferior translation on the sulcus test rose from 10.1 to 18.2 mm (+8.2 mm, p < 0.05).
Board pearl
The authors concluded that the rotator interval capsule checks flexion, extension, adduction and external rotation, resists inferior translation of the adducted arm, and stabilizes against posterior dislocation in flexion or abduction‑external rotation.
Authors' conclusion
Stretching or release of the interval capsule may be a necessary adjunct to treatment when the range of flexion and external rotation is limited, as in patients who have adhesive capsulitis or degenerative joint disease.
Harryman and colleagues examined how the rotator interval capsule, which spans the gap between supraspinatus and subscapularis, contributes to glenohumeral motion, translation and stability.
Cadaver study of 8 shoulders, each tested intact, after sectioning and after imbrication.
Methods
Model
8 cadaver shoulders
Constructs
Intact rotator interval capsule
Sectioned capsule
Imbricated capsule
Loading
Applied loads tracked with a 6‑degrees‑of‑freedom position sensor and force‑torque transducer
Anterior, posterior and inferior stress tests
Outcome measures
Glenohumeral range of motion
Obligate translation during flexion
Translation and stability on stress testing
Key Findings
After sectioning, a posterior force with the arm in 60° abduction and 60° external rotation dislocated the joint posteroinferiorly in 4 of 8 specimens, and allowed posterior translation rose by 6.1 mm (p < 0.05).
Imbrication cut posterior drawer translation by 7.3 to 8.3 mm across the three tested arm positions and inferior sulcus translation by 7.7 mm (all p < 0.05).
Sectioning reduced the obligate anterior translation on flexion by 4.2 mm, while imbrication increased it by 4.9 mm and added 3.5 mm of superior translation (all p < 0.05).
After sectioning, inferior translation on the sulcus test rose from 10.1 to 18.2 mm (+8.2 mm, p < 0.05).
Board pearl
The authors concluded that the rotator interval capsule checks flexion, extension, adduction and external rotation, resists inferior translation of the adducted arm, and stabilizes against posterior dislocation in flexion or abduction‑external rotation.
Authors' conclusion
Stretching or release of the interval capsule may be a necessary adjunct to treatment when the range of flexion and external rotation is limited, as in patients who have adhesive capsulitis or degenerative joint disease.