Early fetal development of the rotator interval region of the shoulder with special reference to topographical relationships among related tendons and ligaments.

PURPOSE: There is a little information on the early fetal development of the rotator interval region of the shoulder, particularly with regard to whether topographical relationships among the ligaments and tendons change during development.
METHODS: We examined the histological sections (transverse or frontal) of right or left shoulder in 20 mid-term human fetuses (7-15 weeks of gestation).
RESULTS: The biceps tendon had an accompanying bursa-like cavity before the joint cavitation. The bursa for the tendon remained open to the joint cavity until 12 weeks. When reaching the glenoid, the biceps tendon involved and carried mesenchymal tissue around the coracoid process (the future coracohumeral ligament) toward the infraspinatus tendon. Until 10 weeks, the primitive glenohumeral ligament was established as simple collateral ligaments on the inner or humeral side of the rotator cuff tendons and the biceps long tendon. However, the subscapularis tendon crossed, attached to, and reformed the upper structure of the superior glenohumeral ligament.
CONCLUSIONS: The early development of the coracohumeral ligament suggests that it is a primitive and basic structure. However, we hypothesize that mechanical demands from the subscapularis tendon and biceps long tendon are likely to change the primitive form of the rotator interval to the adult morphology, including the superior glenohumeral ligament. The significant modification evident during early fetal development suggests that anatomical reconstruction after rotator cuff tears should not be based on the "ideal" anatomy, especially that of the superior glenohumeral ligament, but on individual requirements.