Anatomy and function of the bursa subacromialis

Area of Science:

• Orthopedic Surgery
• Human Anatomy
• Biomechanics

Background:

• The precise anatomical attachments and dynamic behavior of the subacromial bursa and associated structures are critical for shoulder function.
• Previous descriptions of the ligamentum coracohumerale origin and the subacromial bursa's sliding mechanism lack detailed anatomical accuracy.

Purpose of the Study:

• To accurately describe the origin of the ligamentum coracohumerale.
• To elucidate the detailed sliding mechanism of the parietal layer of the subacromial bursa during shoulder abduction.
• To investigate the anatomical course and functional implications of the caput breve of the biceps brachii muscle.

Main Methods:

• Detailed anatomical dissection and observation of the shoulder joint structures.
• Analysis of the subacromial bursa's positional changes during simulated shoulder abduction (0-100 degrees).
• Histological examination of muscle fiber attachments for the biceps brachii caput breve.

Main Results:

• The ligamentum coracohumerale originates medially from the base of the coracoid process, not frontally.
• The subacromial bursa's parietal layer exhibits a complex sliding mechanism between 50 and 100 degrees of abduction, with specific positional changes.
• The caput breve of the biceps brachii has muscle fibers that radiate into the coracoacromial ligament and shoulder joint capsule, forming an 'aponeurosis tendinis brachii'.

Conclusions:

• The corrected understanding of the ligamentum coracohumerale and subacromial bursa mechanics provides new insights into shoulder joint kinematics.
• The 'aponeurosis tendinis brachii' contributes to shoulder joint capsule tension, potentially preventing impingement symptoms.
• These findings enhance the anatomical basis for understanding and treating shoulder impingement and instability.