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Acromioclavicular Joint - Wheeless' Textbook of Orthopaedics
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Wheeless' Textbook of Orthopaedics

Acromioclavicular Joint

- Discussion: 
   - AC joint is situated between the clavicle and acromion; 
   - acromion has two ossification centers which fuse at age 22 yrs; 
   - it permits motion in three planes:
           - AP gliding of acromion during protraction & retraction of scapula;
           - tilting of acromion during abduction & adduction of arm;
           - rotation of the clavicle;
           - rotation occurs during abduction & adduction of shoulder.

- Anatomy: 
    - innervation: provided by the suprascapular and lateral pectoral nerves
    - ref: The suprascapular nerve and its articular branch to the acromioclavicular joint: an anatomic study
    - joint is reinforced by two sets of ligaments:
         - AC ligament
                - directed horizontally, and functionally the AC joints control horizontal stability;
                - palpable shallow depression between end of clavicle & acromion;
                - superior AC lig is most important ligament in stabilizing AC joint for normal daily activities;
         - coracoclavicular ligaments:
                - stronger, vertically directed contains conoid and trapezoid ligaments help to control vertical stability;
                - coracoclavicular lig are suspensory ligaments of upper limb;
                - conoid:
                        - is the most important ligament for support of the joint against significant injuries and superior displacement;
                        - cone shaped which extends between the conoid tubercle on the posterior clavicle and the base of the coracoid;
                - trapezoid:
                        - resists AC joint compression;
                        - begins anteriorly and laterally to the conoid ligament on the clavicle and inserts on the coracoid process; 
         - reference: Biomechanical study of the ligamentous system of the acromioclavicular joint

    - Sternoclavicular joint:
         - see S.C. joint injury in the adolescent;
         - inherently more stable than AC joint; because of this stability & its more protected medial location; 
         - it is injured less frequently than the acromioclavicular joint.

- Management of Specific Injuries:
    - AC joint arthrosis / distal clavicle excision 
          - The influence of distal clavicle resection and rotator cuff repair on the effectiveness of anterior acromioplasty
    - AC joint septic arthritis:
         - Septic arthritis of the acromioclavicular joint - a report of four cases
         - Septic arthritis of the acromioclavicular joint.
         - Sonographic detection, evaluation and aspiration of infected acromioclavicular joints.
         - Primary septic arthritis of the acromio-clavicular joint: case report and review of literature  
    - AC Joint Separation

- Exam:
 
    - palpate the AC joint during flexion and extension of shoulder; 
    - distract the arm as it is placed in adduction
    - significant prominence of the distal clavicle indicates unstable AC injury; 
    - BvR test for DJD: resisted shoulder upward flexion with arm hyperadducted; 
    - ref: Clinical evaluation of acromioclavicular joint pathology: sensitivity of a new test

- Radiology:
    - classification of AC separation 
    - acromioclavicular joint stresses views 
           - grade I injuries remain nondisplaced; 
           - type I and type II injuries can be differentiated on stress radiographs;
           - w/ pt standing, 10 lb weight is secured to affected upper limb;
           - w/ grade II injury, suspended  wt displaces AC joint articulation, which increases distance between clavicle & acromion; 
    - zanca view
    - scapular outlet view
    - reference: Radiological evaluation of the acromioclavicular joint


The acromioclavicular joint in rheumatoid arthritis.

Osteolysis of the distal part of the clavicle in male athletes.




Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Tuesday, January 15, 2013 10:00 am