Acromioclavicular Joint - Wheeless' Textbook of Orthopaedics

- 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:
- 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;
         - references: 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.

- Radiology:
- classification of AC separation:
- acromioclavicular joint stresses views
- 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;
- grade I injuries remain nondisplaced;
- zanca view
- scapular outlet view
- references: Radiological evaluation of the acromioclavicular joint.

- 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 type V injury;

- 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.

    - AC joint separation:
- non operative treatment:
- in the report by TF Schlegel MD et al, the authors prospectively studied natural history of untreated acute grade III AC separations;
- 25 patients were treated nonoperatively with a sling for comfort through progressive early range of motion as tolerated;
- 10 additional uninjured subjects underwent strength testing to evaluate difference between dominant and nondominant sides;
             - one patient underwent a surgical procedure at 2 weeks after injury because of cosmetic concerns;
- 20 of the 25 patients completed the 1-year evaluation and strength-testing protocol;
- 4 of the 20 patients (20%) thought that their long-term outcome was suboptimal, although for 3 of them it was not enough to warrant surgery;
- testing of the 20 patients revealed no limitation of shoulder motion in injured extremity and no diff between sides in rotational shoulder muscle strength;
- bench press was the only strength test that showed a significant short-term difference, with the injured extremity being an average of 17% weaker;
- ref: A Prospective Evaluation of Untreated Acute Grade III AC Separations. TF Schlegel MD. Am Jour of Sports Med 29:699-703 (2001)

          - operative treatment:
                 - Reconstruction of the Coracoclavicular Ligaments with Tendon Grafts. A Comparative Biomechanical Study.
                 - A Modified Technique of Reconstruction for Complete Acromioclavicular Dislocation. A Prospective Study.
                 - Surgery about the coracoid: neurovascular structures at risk.
                 - AC joint dislocation: A comparative study of palmaris-longus tendon graft reconstruction with other augmentative methods in cadaveric models.
                 - Stability of acromioclavicular joint reconstruction: biomechanical testing of various surgical techniques in a cadaveric model.
                 - Anatomical acromioclavicular ligament reconstruction: a biomechanical comparison of reconstructive techniques of the acromioclavicular joint.
                 - Clinical outcomes of coracoclavicular ligament reconstructions using tendon grafts.
                 - Acromioclavicular joint reconstruction using peroneus brevis tendon allograft.
                 - A cadaveric study examining acromioclavicular joint congruity after different methods of coracoclavicular loop repair.

- modified weaver dunn procedure: (for chronic injuries)

The acromioclavicular joint in rheumatoid arthritis.

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

Arroscopic distal clavicle excision. Technique and early results.