Anatomical structure of the coracohumeral ligament and its effect on shoulder joint stability

Background: In this study, coracohumeral ligament (CHL) specimens were carefully dissected to observe its length, width, thickness and tension at different positions of the shoulder joint, thereby elucidating its effects on shoulder joint stability.

Materials and methods: Fresh frozen shoulder joints from 40 normal adult cadaveric specimens were dissected to reveal the CHL. With the shoulder joints placed at different positions, the length of the CHL and the width and thickness of the middle part of the ligament were measured. The changes in tension of the CHL were also observed. When the shoulder joint maintained the neutral position, the length of the CHL was 52.23 ± 1.02 mm and the width and thickness of the middle part of the ligament were 15.95 ± 0.59 mm and 1.46 ± 0.06 mm, respectively.

Results: When the shoulder joint moved from the neutral position to 90° external rotation, from the neutral position to 30° adduction or from the neutral position to 30° flexion/extension or when the shoulder joint is pulled down with a 5 kg weight, the CHL was elongated and thinned, maintaining a strained state. When the shoulder joint moved from the neutral position to 90° internal rotation, from the neutral position to 90° abduction or from the neutral position to 30° flexion/ extension, the CHL was shortened and thickened, maintaining a relaxed state.

Conclusions: The CHL may limit the external rotation, adduction and downward movement of the shoulder joint and the process from the neutral position to the 30° flexion/extension, maintaining shoulder joint stability.    

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