FPT Disorders of the AC joint (separations and arthropathy)

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x Disorders of the

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Acromioclavicular joint JB (3).docx

 

Disorders of the Acromioclavicular Joint

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Figure 1: An AP view of the shoulder, showing the acromion (Acr), Clavicle and the AC joint. Also labeled are the humeral head (HH), the glenoid, the coracoid process (Cor) and the spine of the scapula (SS). (from https://radiopaedia.org/cases/normal-acromioclavicular-joint)

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The joint is stabilized by the acromioclavicular ligament (also known as the “A-C” ligament), which provides horizontal stability, and the coracoclavicular ligaments (also known as the “C-C” ligaments), namely the trapezoid and conoid, which provide vertical stability. The trapezoid is the more lateral, inserting about 3 cm from the end of the lateral (so-called “distal”) clavicle, and the conoid inserts about 1.5 cm medial to that (Figure 2).

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Figure 2: The ligaments of the shoulder: in gold, the coracoclavicular ligaments (trapezoid lateral, conoid medial); in purple, the coraco-acromial ligament; in pink, the coraco-humeral ligament; and in red, the acromio-clavicular ligament. The gleno-humeral ligaments are not shown. (modified from https://radiopaedia.org/cases/normal-acromioclavicular-joint)

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The coracoacromial ligament (also known as the “C-A” ligament), which runs from the coracoid process to the acromion, forms an arch that helps constrain the humeral head.

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A patient will present with pain over the AC joint that limits shoulder range of motion, both passively and actively. Possible swelling or ecchymosis can occur over the AC joint with displacement of the arm and shoulder downward and forward causing the appearance of a prominent clavicle (Figure 3).

 

Figure 3:

 

AC joint osteoarthritis presents with chronic discomfort localized to the joint. Patients may report difficulty using the arm or sleeping on the affected shoulder. At times there is a sense of clicking or snapping during use. On physical examination, there is tenderness to palpation of the AC joint (Figure 3), a prominence of the distal clavicle (due to osteophytes) can be seen, and there is focal AC pain with cross body adduction of the arm (Figure 4).

 

Figure 3: Palpation of the AC joint

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Figure 4: Cross body adduction of the arm is typically painful at the AC joint if that joint is arthritic

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Objective Evidence  

AC joint separations are diagnosed by clinical examination and x-ray (Figure 5).

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Figure 5: A downward force on the acromion (yellow) will tear the coracoclavicular ligaments (red). The distal clavicle will accordingly appear to be “high riding” but in fact the clavicle is close to normal in its position; it is the acromion that is lower than normal. (modified from https://www.ncbi.nlm.nih.gov/books/NBK493188/figure/article-17117.image.f1/)

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They are classified according to the amount and direction the physical separation seen between the acromion and the clavicle (Figure 6).

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Figure 6: A schematic drawing showing three of the grades of AC separation. A grade I sprain has no displacement; a grade III has complete tears of the ligaments but only slight displacement; and a grade V has wide displacement. (See text for description of the even numbered grades). (modified from https://upload.wikimedia.org/wikipedia/commons/thumb/0/0f/ACJ_injuries_classification.svg/2000px-ACJ_injuries_classification.svg.png)

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Radiographic assessment of the AC joint is best performed with bilateral anteroposterior (AP) views. This allows for side to side comparison of coracoid-clavicle distance.

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Figure 7: A screw inserted from the superior surface of the clavicle into the coracoid can hold the clavicle at the appropriate distance. (from http://eoj.eg.net/viewimage.asp?img=EgyptOrthopJ_2014_49_4_320_154094_f8.jpg)

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Post-operatively, patients typically use a sling for immobilization for two to four weeks, active range of motion by six weeks, and resistance rehabilitation by 12 weeks followed by return to activity.

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Although the clavicle appears to be elevated in the case of an AC joint separation, most of the deformity is from downward migration of the acromion (due to the way to the arm[MF1] ).

 

Key Terms

Acromioclavicular joint, coracoclavicular joint, synovial joint, Rockwood classification

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Interpret classic history and physical exam findings to confirm diagnosis. Apply the classification of AC injury to formulate a treatment plan.

 


 [MF1]??doesn't make sense