Anatomical observations of the human acromioclavicular joint

Abstract

The condition of the acromioclavicular joint (ACJ) is considered to be one factor in the etiology of shoulder impingement syndrome, but there are few supporting morphological data. Fifty-two sides of 35 cadavers were investigated macroscopically and histologically using Safranin O, Fast green, and Weigert's iron hematoxylin staining. The ACJs were classified into three major types depending on the presence or absence of the articular disk. In type 1, the articular disk divided the articular cavity completely (n = 2; 3.8%). In type 2, the articular disk was incomplete and divided the joint cavity incompletely (n = 13; 25%). Type 2 was further divided into subtypes 2a and 2b depending on the configurations of the articular facets. In type 3, no articular disk was found in the joint cavity (n = 37; 71.2%). Type 3 was further divided into subtypes 3a, 3b, and 3c depending on the configurations of the articular surfaces. Fewer than half of the ACJ specimens (22/52 or 42.3%) demonstrated an ellipsoid character in which axial rotation was limited. Histological observation revealed that the upper part of the articular disk of the ACJ comprised fibrocartilage while the lower part comprised dense connective tissue. In cases where the ACJ appears to be an ellipsoid joint, its limited axial rotation restricts posterior tilting of the scapula during arm elevation, which could contribute to shoulder impingement syndrome.

Injury patterns of the acromioclavicular ligament complex in acute acromioclavicular joint dislocations: a cross-sectional, fundamental study

“…A proportion of 37 % showed no articular disc or only remnants of an articular disc. Histological studies have confirmed that the articular disc is confluent with the superior capsular-ligamentous structures forming an anatomical-biomechanical unit [6, 27]. Hereby, the articular disc seems to function as a biomechanical reinforcement of the superior ACLC.…”

“…If present, the articular disc may vary in size and appearance [6, 27]. The deltoid-trapezoidal (DT) fascia inserts on the superior lateral clavicle and superior ACLC providing additional biomechanical reinforcement [31].…”

Shoulder Joint

“…In a cadaveric study, Emura et al (2014) classified the acromioclavicular joint into three major types according to the presence or absence of the articular disc.…”

Arthroskopisch gestützte Techniken zur Versorgung der akuten und chronischen AC-Gelenk-Verletzung

“…Vermeintlich nicht ausreichende Repositionen können bei Vergleich mit der (unverletzten) Gegenseite in einigen Fällen als Normalbefund eingestuft werden. Die Reposition selbst kann aber auch durch die Konfiguration des ACG selbst erschwert sein, da es verschiedene Varianten des Diskus und der Formschlüssigkeit der lateralen Klavikula zur Gelenkfläche am Akromion gibt [12].…”

“…Die knöchernen Gelenkpartner sind mit hyalinem Knorpel über-zogen. Im Gelenkspalt befindet sich ein fibrokartilaginärer Diskus unterschiedlicher Größe und Form [7,12]. Die Stabilität des Gelenks wird durch die ACGKapsel und durch die korakoklavikulä-ren(CC)-Bänder gewährleistet.…”