Acromioclavicular joint arthritis

DR ZUBAIR RINGSHAWL
POST GRADUATE SCHOLAR

1. ACROMIOCLAVICULAR JOINT ARTHRITIS

2. DEFINITION Acromioclavicular joint arthritis  (AC joint arthritis) is a progressively degenerative disease in which there is degeneration of joint cartilage and the underlying bone which causes pain and stiffness.

3. ETIOLOGY The combination of three factors underlies the frequency of problems of the AC joint. First , because it is a diarthrodial joint, it is vulnerable to the same processes affecting other joints in the body, such as degenerative osteoarthritis, infections and inflammatory and crystalline arthritis.

4. Second, its superficial location and its relationship to the shoulder girdle predispose it to traumatic injury. Third , the biomechanics of the shoulder girdle require the AC joint to transmit large loads across a very small surface area , which can result in failure with repetitive activity or overuse.

5. RISK FACTORS 1.Age (>45 yrs ) 2.History of previous injury to AC joint (specially previous trauma and sports injury) 3.Weight lifting activities particularly those transmitting huge loads across shoulder joint like bench press and military press.

6. CAUSES There are three common causes of acromioclavicular joint arthritis: 1. Primary Osteoarthritis. 2. Post Traumatic Osteoarthritis. 3. Distal Clavicle Osteolysis .

7. Primary Osteoarthritis In comparison to the rate of occurrence in the knee and hip, primary osteoarthritis in the shoulder is relatively rare. However , primary involvement of the AC joint is much more common than primary involvement of the glenohumeral joint and is, in fact, the most common cause of pain in the AC joint . Degenerative changes by the fourth decade in the majority of AC joint.

8. In one study, 54% to 57%of elderly patients demonstrated radiographic evidence of degenerative arthritis . In another study, magnetic resonance (MR) imaging demonstrated evidence of arthritic changes in 48% of the AC joints in over 300 older asymptomatic patients . Despite its seeming prevalence by radiologic criteria, symptomatic primary osteoarthritis is a relatively uncommon clinical entity.

9. Posttraumatic Arthritis Acromioclavicular arthritis following trauma is even more common than primary osteoarthritis, due to the frequency of injury to this vulnerable joint . The incidence of posttraumatic arthritis symptoms after injury or surgery is highly variable and depends on the degree of injury and the type of operative procedure .

10. Arthritis also occurs, although less commonly, after distal clavicle fractures, particularly those with intra-articular extension . Operative procedures for AC joint dislocations in which the AC joint is preserved or transfixed have been associated with a higher incidence of arthritis than those in which the joint is sacrificed(i.e., Weaver-Dunn procedure).

11. Distal Clavicle Osteolysis An increasingly recognized but still infrequent entity that causes AC joint symptoms is distal clavicle osteolysis . Osteolysis related to repetitive microtrauma has recently been receiving more attention, particularly among weight-lifting athletes. This condition is thought to be growing in frequency due to the popularity of weight-training and its incorporation into fitness programs and training regimens for other sports.

12. The proposed mechanism of this form of osteolysis is that repetitive stresses to the subchondral bone of the distal clavicle lead to fatigue failure, which initiates resorption .

13. GRADING OF OSTEOARTHRITIS

14. Evaluation and Diagnosis Presentation Isolated AC joint arthritis presents with discomfort or aching over the anterior and/or superior aspect of the shoulder. Pain is often brought on by activities of daily living, such as washing the opposite axilla, reaching back to retrieve a wallet. Symptoms are often exacerbated by more demanding activities, such as pushing or overhead work in the case of laborers and weight lifting, golfing , swimming, or throwing in athletes .

15. Patients may note pain at night, with nocturnal awakening when rolling onto the affected shoulder. There may be associated symptoms of popping, catching, or grinding .

16. Physical Examination Careful examination of the entire shoulder girdle combined with cervical spine examination is essential to rule out any contribution from cervical lesions. Inspection of the affected extremity may reveal swelling, deformity, joint prominence or asymmetry which may indicate AC joint instability. P alpation over the AC joint may elicit tenderness, which is anecdotally sensitive but non specific.

17. Dynamic stability of the AC joint can be assessed by placing the patient supine and affected extremity in 90 degrees of flexion. With one hand on the affected joint , examiner assesses for the movement of the clavicle with respect to acromion while applying a downward force on the patient’s flexed arm.

18. SPECIFIC TESTS 1. Provocative maneuvers , such as reaching across to touch the opposite shoulder or placing the hand behind the back, may elicit discomfort. Provocative tests include: a) Cross body adduction test The most reliable provocative physical examination is the cross body adduction test, in which the arm on the affected side is elevated 90 degrees of forward flexion and the examiner then grasps the elbow and adducts the arm across the body.

19. Reproduction of pain over the AC joint is suggestive of an AC joint lesion. This test may also be positive in patients with subacromial impingement and may cause discomfort posteriorly in patients with posterior capsular tightness. Sensitivity is 77% and specificity is 79%.

20. b) AC resisted extension test : The patient is seated with the examiner standing behind him/her. The patient's shoulder is positioned into 90 flexion and internal rotation, with the elbow placed into 90 flexion. The examiner places his/her hand on the patient's elbow and asks him/her to horizontally abduct the arm against isometric resistance A positive test is pain at the AC joint. S ensitivity is 72% and specificity is 85%.

21. c) O’Brien active compression test : In this test, the affected arm is brought into 90 degrees of forward flexion and 10 degrees of adduction. The patient then performs resisted shoulder flexion with the arm in maximum internal rotaion and then in maximum supination. Pain with the former maneuver is consistent with a SLAP lesion and pain with the latter maneuver indicates AC joint abnormality .

22. Sensitivity is 41% and specificity is 95%. The overall accuracy of these provocative tests in diagnosing AC joint arthritis is 93%.

23. 2. Painful arc sign: In this test, the affected shoulder is abducted and if the patient experiences pain during the last 30 degrees of abduction, it is consistent with AC joint arthritis. Sensitivity is 50% and specificity is 47%.

24. 3. Paxinos Sign: With the patient sitting and the symptomatic arm by the side, the examiner's thumb is placed under the posterolateral aspect of the acromion and the index and middle fingers of the same (or contralateral) hand are placed superior to the mid-clavicle. If we are examining left shoulder right hand is to be used for eliciting this sign and vice versa. The examiner provides pressure to the acromion in an anterosuperior direction with the thumb, while also applying pressure an inferior direction to the mid-clavicle with the index and middle fingers

25. If pain is elicited or increased in the region of the acromioclavicular joint, the test is considered positive

26. RADIOLOGICAL EVALAUATION X - RAYS 1. Shoulder AP view: The AP projection is usually obtained with the patient in the upright or supine position and with the coronal plane of the body parallel to the cassette . The beam is directed in a true AP direction relative to the body.This results in slight overlap of the glenoid rim and the humeral head as the glenohumeral joint is tilted anteriorly approximately 40 °.

27. The beam is oriented in true AP view to the patient with the arm positioned in either neutral, internal, or external rotation. The beam is centered on the coracoid process with the blade of the scapula parallel to the film.

28. 2. Zanca View: Zanca described a modified technique that provides a clear, unobstructed view of the distal clavicle and AC joint. This projection is obtained by angling the x-ray beam 10 to 15 degrees superiorly and decreasing the kilovoltage to about 50 % of that used for a standard glenohumeral exposure.

29. AP view of the shoulder demonstrates the glenohumeral joint anatomy but is overpenetrated and fails to demonstrate the AC joint well. Zanca view better depicts the soft-tissue and joint detail of the AC joint; however, the glenohumeral joint is no longer well visualized

30. Findings: Patients with primary or posttraumatic degenerative arthritis will have findings of arthritic changes which include sclerosis , osteophyte formation, subchondral cysts , and joint space narrowing.

31. 3. SUPRASPINATUS OUTLET VIEW The supraspinatus outlet view is useful for evaluating the acromion process and subacromial abnormalities such as osteophytes that may cause impingement . It is similar to the Y-view but with caudal tube angulation. This view is taken with the patient turned as for the Y projection and the cassette perpendicular to the body of the scapula and parallel to glenoid fossa. The X-ray is taken from a mediolateral projection along the axis of the scapular spine , with X-ray beam angled 10–15° craniocaudally and centred on the acromioclavicular joint.

32. This view is taken with the patient turned as for the Y projection and the cassette perpendicular to the body of the scapula and parallel to glenoid fossa, with X-ray beam angled 10–15° craniocaudally and centred on the acromioclavicular joint.

33. The subacromial space (arrows) and contour of the acromion (A) are well seen. The water density of the supraspinatus muscle is shown (S).

34. ULTRASONOGRAPHY Ultrasonography can be used to assess joint space detect osteophytes or other bony erosions, although the usefulness of this technique is dependent on the skill of the technician and is limited to superficial soft tissue.

35. MRI Magnetic resonance imaging is very sensitive in identifying abnormalities of the AC joint, but these changes often do not correlate with physical findings. In one study of asymptomatic volunteers, findings indicative of AC joint arthritis were present in 75% of shoulders. The nonspecificity of MR imaging precludes it from being useful in the evaluation of patients with AC joint symptoms . But MRI can be helpful in ruling out other causes of shoulder joint pain which can be concomitantly present with AC joint arthritis.

36. JOINT INJECTION: Joint injection can be used both diagnostically and therapeutically. A combination of local anaesthetic and corticosteroid is used. Technique: Palpate the bony landmarks and mark the site of injection. Prepare the skin using sterile technique. A 23-gauge needle is directed into the joint from a superior approach. The needle is then slowly advanced perpendicular to the articulation while palpating for a tactile pop through the capsule. The mixture can then be easily injected and noted to flow freely into the joint

37. Direct injection into the AC joint through a superior approach.

38. The joint can be injected under sonographic guidance using this view

39. Despite the subcutaneous nature of the joint, intraarticular injections can sometimes be difficult where the accuracy can be improved with the use of ultrasound guidance. Elimination of pain within a few minutes of the injection confirms the AC joint as the source of the patients symptoms and is considered by many authors to be the most valuable diagnostic tool. Relief after an injection is also considered the most accurate prognostic indicator of success with distal clavicle resection.

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