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.

Development of the supraspinatus tendon-to-bone insertion: localized expression of extracellular matrix and growth factor genes.

The adult healing response of the rotator cuff tendon-to-bone insertion site differs from the ordered process of insertion site development. Healing is characterized by disorganized scar and a lack of fibrocartilage formation, in contrast to the well organized fibrocartilaginous transition which forms during the normal development of the tendon-to-bone insertion. The purpose of this study was to localize the expression of a number of extracellular matrix and growth factor genes during insertion site development in order to guide future strategies for augmenting adult rotator cuff healing. The rotator cuff was morphologically distinct at 13.5 dpc (days postconception). Neo-tendon was evident as a condensation of cells adjacent to bone. The interface between tendon and bone did not form into a mature fibrocartilaginous insertion until 21-days postnatally, based upon the appearance of four distinct zones with a mineralized humeral head. Fibroblasts of the supraspinatus tendon expressed type I collagen at all timepoints. Type II collagen was first expressed by chondrocytes in the fibrocartilage and mineralized fibrocartilage at 7 days and persisted in the mineralized fibrocartilage at 56 days. Type X collagen was first expressed by the chondrocytes in the mineralized fibrocartilage at 14 days and persisted in the mineralized fibrocartilage at 56 days. A shift from TGF-beta3 to TGF-beta1 expression occurred at 15.5 dpc.

Arthroscopic study of the shoulder joint in fetuses.

PURPOSE: The purpose of this study was to macroscopically examine the fetal shoulder joint using arthroscopy. We attempted to identify and describe the specific characteristics of the fetal shoulder joint, how it evolves during the last few weeks of intrauterine development, and any possible variations with regard to the adult shoulder. TYPE OF STUDY: Observational anatomic case series. METHODS: We used 20 frozen fetuses with a gestational age of 24 to 40 +/- 2 weeks, obtained from spontaneous abortions. Examination was performed with standard arthroscopic surgical equipment, using a 2.7-mm optical lens. Whenever possible, we tried to use the standard arthroscopic portals. Images were obtained for comparison with the adult shoulder. RESULTS: The arthroscopic images of the fetal glenohumeral joint are similar to those of an adult shoulder, with the only differences being those related to the stage of development. In this study we observed no so-called bare spot in the glenoid cavity such as has been described in treatises on the adult shoulder joint. The arthroscopic images of the anterosuperior region of the fetal joint show more highly defined structures than in the adult shoulder, especially the coracohumeral and glenohumeral ligaments. CONCLUSIONS: To our knowledge, this is the first arthroscopic study to target the fetal shoulder joint. The results indicate minimal differences when compared with the adult shoulder joint; for some structures, particularly in the anterosuperior region, the anatomy observed was easier to discern than what is observed in adult shoulder arthroscopy. CLINICAL RELEVANCE: Our study obtained clear images of virgin shoulder joints that had never been subjected to deterioration from wear or other distorting forces. The clarity of these images is useful for locating and identifying structures in the adult shoulder.

The developmental anatomy of the neonatal glenohumeral joint.

The embryologic development of the capsular ligaments, synovial lining, rotator cuff, and bony structures of the shoulder is incompletely understood. The purpose of this study is to report the gross and microscopic anatomy of the developing glenohumeral joint on the basis of dissections of fetal shoulder specimens. After Institutional Review Board approval from our hospital, 51 shoulders in 37 fetal specimens were obtained from cases of fetal demise. The gestation time of these specimens ranged from 9 to 40 weeks. The morphology of the capsule, labrum, and associated ligaments were studied by dissection under a dissecting microscope. High-resolution radiographs were made, and sections were processed for routine histology. There was noted to be minimal variation in the shape and slope of the acromion. The coracoid was much larger in relation to the shoulder than in the mature shoulder. The coracoacromial ligament was grossly evident at this stage of development, with distinct anterolateral and posteromedial bands in this ligament. The inferior glenohumeral ligament was seen as a prominent thickening in the capsule, whereas the middle and superior glenohumeral ligaments were thinner and more difficult to identify as distinct structures. Upon histologic examination, the inferior glenohumeral ligament was seen to consist of several layers of organized collagen fibers. The inferior glenohumeral ligament inserted into the labrum and margin of the glenoid. The capsule was much thinner in the region superior to the inferior glenohumeral ligament. A rotator interval capsular defect was often present, and the coracohumeral ligament was seen as a distinct structure as early as 15 weeks. A bare spot in the glenoid was not observed. This study indicates that some of the important functional elements of the structure of the mature human shoulder are present early in development, including the glenohumeral and coracohumeral ligaments. The coracoacromial ligament plays a significant role in the formation of the coracoacromial arch in the neonatal shoulder. The presence of a capsular rotator interval indicates that this aspect of capsular anatomy is congenital.

Injuries to the glenoid labrum, including slap lesions.

The glenoid labrum of the shoulder has extensive anatomic variation but appears to be important for contributing to shoulder stability and for increasing the depth of contact between the glenoid labrum and the humeral head. Tears of the labrum are commonly seen in association with other pathologic entities, such as instability and rotator cuff tears, and treatment of the labral pathology may be incidental to treatment of the other more significant pathology. However, conditions isolated to the labrum do occur and can be a significant source of shoulder problems. Effective treatment of these lesions may result in significant improvement in the patient's symptoms. Labral lesions are difficult to diagnose, and special diagnostic studies and, frequently, arthroscopy are required. The recently described SLAP lesion is an uncommon but significant cause of shoulder disability that generally requires arthroscopic diagnosis. The arthroscopic treatment of this lesion depends on the type of SLAP lesion present. Recent techniques have permitted arthroscopic stabilization of the biceps labral detachment and type II SLAP lesions.