Abstract:

BACKGROUND: At present, most clinicians believed that shoulder diseases such as acromioclavicular joint dislocation and subacromial impact syndrome, have a great relationship with the anatomic shape of the acromioclavicular joint. However, there are few morphological data on acromioclavicular joints in and outside China, especially for the anatomical study of acromioclavicular joint disc. Simultaneously, the acromioclavicular joint belongs to the micro-movement joint and participates in the joint movement of the shoulder joint. There are many clinical methods of acromioclavicular dislocation surgery, the most popular surgical methods are rigid fixation, and do not retain their micro-movement characteristics and the motion characteristics of the clavicle and scapula. Among them, the choice of joint discs is not a large multicenter controlled study in and outside China.

OBJECTIVE: To study the anatomy of the acromioclavicular joint and joint discs in order to diagnose and treat shoulder diseases.

METHODS: The morphology and tissue structure of 58 acromioclavicular joint corpses (provided by the Department of Anatomy, Tongji University) were studied. A total of 58 acromion, 58 clavicles and 36 joint discs (including complete and incomplete) were obtained. BIGLIANI acromicular morphology typing, DEPALMA clavicle morphological typing, and EMURA acromioclavicular joint disc typing were used to obtain the frequency of joint discs under each acromion and clavicle combination and hematoxylin-eosin staining (provided by Shanghai Putuo District People’s Hospital).

RESULTS AND CONCLUSION: (1) Among 58 corpses of acromioclavicular joints, there were 15 cases of type 1 acromioclavicular joints, with the highest proportion being 25.9%, and 4 cases of type 3a, with the lowest proportion being 6.9%. (2) There was 32 type I acromion, with the highest proportion of 55.2%, 3 type III acromion, with the lowest proportion of 5.2%. (3) There were 27 type I clavicle, with the highest proportion of 46.6%, 9 type III clavicle, with the lowest proportion of 15.5 %. (4) Type I and type II acromion combined with type I clavicle accounted for a large proportion, which were 24.1% and 22.4%, respectively, and type III acromion had a minimum proportion of type I clavicle of 0%. (5) Type 1 and type 2b joint discs accounted for the largest proportion under the combination of type I acromion and type I clavicle, which were 35.7% and 28.6% respectively. Type 2a and type 1 joint discs under the combination of type II acromion and type I clavicle presented the largest proportions 38.5% and 23.1%. (6) Hematoxylin-eosin staining could be found in tissue sections. The extracellular matrix in the articular disc was clearly discernible. The cells were full in morphology, and rich in cytoplasm, suggesting chondrocytes, which were the main components of fibrocartilage formation. In addition, part of the periosteum fiber layer can be seen from the top and bottom of the joint capsule to the inside of the joint disc. It is considered to form a joint disc structure, that is, the joint disc is composed of chondrocytes near the bone surface and a fiber layer away from the bone surface.

Key words: bone, joint, acromioclavicular joint, articular disc, acromion, clavicle, joint dislocation, anatomy