State of ACjoint space and SCjoint space according to De Palma [31

Of significance was the observation that the lateral one third of the clavicles exhibits varying degrees of anterior torsion. This is readily noted if the clavicle is observed with the sternoclavicular and the acromioclavicular joints intact and if the sternum is placed in a vertical position (Fig. 33a). Sixty-six such specimens obtained from cadavers were studies; the clavicles fell into one of three types, each of which exhibited specific features (Fig. 33b):

■ Type 1: in this group the clavicles show the greatest amount of anterior torsion of their lateral thirds. The acromial end is flat and thin and possesses a small articular surface. The plane of the acromiocla-vicular joint is directed downward and inward; the angle ranges from 10 to 22°, with the average angle being 16°. At the sternal end of the clavicle the plane of the sternoclavicular joint is not far from the vertical and is directed downward and outward. The angle ranges from 0 to 10°, with the average angle being 7.5°.

■ Type 2: the anterior torsion of the lateral one third of the clavicles of this category is less than that noted in Type 1. Also, the acromial end is stouter and slightly more rounded. The plane of the acromioclavi-cular joint forms a greater angle with the vertical than that noted in Type 1; the average angle is 26.1°. Of interest is the configuration of the lateral curve of the clavicle, which describes an arc of a circle smaller than the circle of the arc of the lateral curve in Type 1. The angle of the plane of the sternoclavicular joint is slightly greater, with the average angle measuring 10.9°.

■ Type 3: in this group the outer third of the clavicle has the least amount of anterior torsion. Its acromial end is stout and rounded, presenting almost a complete circular articular surface. The arc of

Outer Third ClavicleThree Types Clavicles

Fig. 33. a Degrees of anterior torsion of the outer third of the clavicle in the three types, b The degree of the anterior torsion of the clavicle determines the inclination of the articular surfaces of the sternal and acromial ends of the clavicles, permitting the joints to be grouped into one of three categories or types the lateral curve is of a circle that is smaller than the circles of the arcs noted in Types 1 and 2. The plane of the acromioclavicular joint is not for from the horizontal, the average angle being 36.1°; on the other hand, the plane of the sternoclavicular joint forms an average angle of 13.9° with the vertical.

It is clear that from type 1 to type 3 the angles of the planes of both the acromioclavicular and the sternoclavicular joints increase progressively, whereas the size of the circles of the arcs of the lateral curves diminishes. Of the 66 specimens studied 27 (41%) were type 1, 32 (48%) were type 2, and 7 (11%) were type 3. That these observations have significant clinical application was shown in a clinical study of the relationship between painful acromioclavicular joints due to degenerative changes and the three aforementioned types of clavicles; it was found that the great majority of the patients possessed clavicles classified as type 1. If appears that in type 1 the plane of the joint is such that during motion more shearing forces act on the articular surfaces of the other two types of clavicles. Moreover, the articular surfaces of the joints in type 1 are smaller than those of the other two types, which may be another factor that predisposes the articular cartilage to degenerative alterations.

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Responses

  • david
    What is the lateral end of the clavicle?
    7 years ago
  • lalli
    What is acjointy disorder in females?
    2 years ago

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