There is a paucity of data on the epidemiology of acromioclavicular (AC) joint dislocation. Some studies cite that it accounts for 9% of all shoulder injuries. The earliest known incidence was reported in 1973 by Nordqvist and Petersson wherein the incidence of AC joint location in an urban setting was 1.5 per 10,000 among males and 0.2 per 10,000 among females. In this study, only 19 cases were identified in one year.
In a more recent study, a retrospective study by Chillemi et al in 2013 reported that the incidence of isolated acromioclavicular joint dislocation was 1.8 per 10,000 per year while the sex ratio (male:female) was 8.5:1. This predominance in males could be explained by the fact that more males engage in high-level activities or contact sports than females. Majority of patients who had AC joint dislocation were aged 20 to 39 years old (mean: 37.5 years).Among females, the mean age was 36.6 years (SD 15.6), while the mean age among males was 37.6 years (SD 13.5). More than half (53.3%) of the injuries occurred on the right side.
Sports injury was the most common cause of AC joint dislocation, specifically cycling, soccer, basketball and rollerblades.5 Among these sports activities, cycling was the most common and this occurs due to direct impact to the joint when the arm is adducted or outstretched, rendering the AC joint more susceptible to tears and strains.6 In addition to sports, other causes identified in the study were the following (in decreasing order of incidence): road accident, accidental fall, work-related injuries and aggression. Among those who had road accidents, the tight seatbelts in vehicles could have aggravated the direct trauma in the shoulder.
Rockwood type III (torn AC ligament, disrupted AC joint capsule, torn CC ligament, intact delta-trapezial fascia) was the most common type of dislocation.
Natural history
The most common mechanism of acromioclavicular joint dislocation is fall, wherein there is direct force to the lateral aspect of the shoulder, which is usually in the abducted position.
Several studies suggest that in most cases, no formal operative treatment in acromioclavicular joint dislocation is necessary for complete recovery.
A prospective study by Schlegel et al documented the natural history of 25 patients who had grade III acromioclavicular joint dislocation and who were treated non-operatively. Patients were given slings for two weeks, analgesics and course for early range of motion (ROM) exercises. Patients who were able to complete the study had no limitation of shoulder motion in the injured extremity after one year. Likewise, there was no difference between both sides in rotational shoulder muscle strength. Follow-up of patients revealed that the average time that the patients needed treatment (sling) was 8 days (range, 2 to 25). In addition, majority of patients (15/20) required analgesics for less than a week. Most patients were able to return back to work around this time (average – 9 days).
At one year, most of the patients had no subjective strength loss. Three patients noted submaximal strength subjectively, noting that there was impairment in their ability to lift heavy objects. One patient had weakness during bench press exercises. On objective evaluation, however, all patients demonstrated recovery of the injured shoulder, reporting that it had full, pain-free and symmetric range of motion.
Among the exercises, only the bench press test had significant difference between the injured and uninjured shoulder (P <0.05). This can be explained by the fact that acromioclavicular joint prevents posterior displacement of the clavicle, which is induced during the bench press. If there is injury to the joint, there is free movement of the distal end of the clavicle posteriorly so there is no resistance to the forces brought about by bench press.
The authors concluded that majority (80%) of patients with acromioclavicular joint dislocation had satisfactory results after one year of follow-up, majority (14 out of 16 patients) had no injury-related pain during physical activity and only three patients had weakness with repetitive bench press exercises. Other isokinetic strength outcome measures did not vary significantly between the injured and non-injured shoulder.
It appears that dislocation of the acromioclavicular joint did not result in significant loss of strength even when no surgical intervention has been instituted.
Walsh et al reported that patients with acromioclavicular joint dislocation who were surgically treated had significant strength deficit in vertical abduction at fast speeds compared to the unaffected shoulder. In addition to this, these patients with Grade III injuries who underwent surgery had lower overall subjective outcome compared to those managed conservatively. However, Grade III injuries treated nonoperatively may not have shown any significant strength deficits but patients reported more pain and stiffness. Paradoxically, Grade II injuries had more significant weakness in horizontal abduction (24.3%) at fast velocity.
Other studies had similar findings that strength was not affected despite the absence of surgical treatment.
Several surgical and non-surgical techniques, depending on the classification of the dislocation, are currently available to address the anticipated sequelae of acromioclavicular joint dislocation.
Signs and symptoms of Acromioclavicular Joint Dislocation
Symptoms of acromioclavicular (AC) joint dislocation range from minor discomfort with minimal activity to complete disability of the injured shoulder. In acute presentation, patients may have pain, decrease in range of motion or decrease in or loss of strength in the affected shoulder. Pain is elicited when the patient performs overhead movements or lie on the affected side. At first, pain is diffuse and difficult to localize but at a latter stage, patient is able to pinpoint the location of the pain. When pressed, the collarbone may move.
On physical examination, the patient may be seen as reflexively supporting his elbow or clipping his arm close to the sides of his body. There may be swelling, deformity and ecchymosis on the injured lesion and joint restrictions in rotation with marked tenderness of the paraspinals in the surrounding cervicothoracic region. A popping sound on the elbow may also be heard. Furthermore, there may be local tenderness in the acromial insertion of the deltoid, pectoralis insertion at the humerus, the superior fibers of the trapezius, from the proximal insertion site at the occiput to the superior angle of the scapula to the insertion at the distal clavicle, posterior scalene, levator scapulae proximal insertion at the upper cervical transverse processes, and the insertion of the infraspinatus and supraspinatus muscles at the greater trochanter.
Gross deformity and tenting of trapezius and deltoid muscles can be seen in type IV and V dislocation injury.3 Displacement of skin can also be seen.
To elicit AC joint pain, several orthopedic tests may be performed, such as: drop arm (while patient’s is arm at 90° of abduction, patient slowly lowers the arm), Neer test (patient’s arm is passively forced into full vertical abduction while in scaption with glenohumeral internal rotation), spring test (clinician places a direct inferior force over the distal clavicle reducing the separation followed by release of this contact), crossover test (patient’s arm is placed into full horizontal adduction from 90° of vertical abduction or ballottement of the lateral end of clavicle), the sulcus test (with patient’s arm at his side, the clinician grasps the forearm distal to the elbow joint and induces a distal distraction to the glenohumeral joint), compression test (with the patient sitting upright, the clinician places one hand on the anterior, middle one third of the clavicle and the other hand on the spine of the scapula—opposing forces (anterior and posterior) are applied to induce a shearing force through the AC joint) and the Kemp test of the cervical spine (passive lateral flexion and extension of the cervical spine with overpressure at the forehead), which produces pain at the cervicothoracic junction.
If the acromioclavicular joint dislocation is bilateral, even the sternoclavicicular joint can be dislocated. Some patients can have stiff shoulder due to concomitant injury to the rotator cuff or other muscles.
In the chronic presentation, nagging medial scapular pain is the most common complaint. Radiating pain and brachialgia can also occur. This is because of disruption of the scapula-thoracic rhythm. If there is AJ joint synovitis, the cross adduction test is positive.
Differentials
Concomitant shoulder injuries associated with acromioclavicular should be ruled out.
In one study by Tischer et al,1 intra-articular injuries were present in 18.2% of patients (14/77). In addition, there were superior labral anterior posterior (SLAP) lesions in 14.3% patients (11/77, SLAP I- II- III and IV). One patient demonstrated complete supraspinatus tear and two patients had partial articular-sided supraspinatus tears. In four patients, an accompanying fracture on top of the acromioclavicular joint separation was detected.
In another study, hemarthrosis or presence of blood in the shoulder joint was detected in all patients with acute acromioclavicular joint dislocation. Chondral or osteochondral Hill-Sachs lesion was also noted in majority of patients (88.1%). Other lesions noted on top of AC joint dislocation were: Bankart lesion (83.46%), anterior labroligamentous periosteal sleeve avulsion (ALPSA) lesion, (10.23%), SLAP lesion (20.47%), humeral avulsion of the glenohumeral ligament (HAGL) lesion (1.57%), and capsular laxity (25.98%). Only patients with chronic instability had ALPSA lesions (P = .044) while only patients with acute dislocations had HAGL lesions (P = .002). Another concomitant lesion found in 14 patients was partial-thickness articular rotator cuff tear (chronic cases- 11.53%, acute cases- 8.69%, P = 0.694).
Another study revealed similar findings. Intraarticular lesions were found in 15% of patients (6/40), mostly glenohumeral pathologies resulting from trauma to the shoulder girdle. Other lesions noted were isolated partial tear of the subscapularis tendon, combined tear of the subscapularis and supraspinatus tendon (PASTA type lesion), type II SLAP-lesion, type VI SLAP-lesion.
A recent study among 125 patients with acromioclavicular joint dislocation showed that the prevalence of concomitant glenohumeral pathologies is 30.4%. These pathologies are acute intraarticular lesions that are related to the trauma (7.2%), degenerative lesions that are unrelated to trauma (14.4%) and lesions that are considered unclear traumatic correlation or intermediate (8.8%). Most commonly affected structures in the acute and degenerative group were predominantly partial, articular-sided tears of the anterosuperior rotator cuff, pathologies of the long head of the biceps and superior labrum anteroposterior lesions. On the other hand, the intermediate group were usually articular-sided partial tears of the subscapularis tendon.
Other differential diagnoses are: acromioclavicular sprain, distal clavicular fracture, osteolysis of the distal clavicle. Acromioclavicular joint sprain occurs with different degrees of ligamentous damage and siplacement. Distal clavicular fracture disturbs the stabilizing ligaments of the acromioclavicular joint. Osteolysis of the distal clavicle is an atraumatic condition associated with weight training.
Another study documents other types of shoulder injuries that can mimic acromioclavicular joint dislocation. Clavicle fracture is the most common type of shoulder injury, majority of which are conservatively-treated. Humeral head fracture can also occur, mostly in the elderly. Acute soft tissue injuries can be present in the setting of shoulder dislocation, rotator cuff tears and acromioclavicular sprains.
Acromioclavicular Joint Dislocation Treatment (Nonoperative and operative)
Upon diagnosis of acromioclavicular joint dislocation, first aid through application of ice should be instituted. The shoulder should be immobilized using arm sling. A doctor, specifically an orthopaedic surgeon, should be consulted promptly for grading of the injury and to rule out other problems. (Please see Differentials Section)
The approach to treatment for acromioclavicular dislocation depends on the degree of injury or the grade of dislocation.
Grade I and grade II injuries are best treated conservatively, meaning no surgery is required for full recovery. RJ bandage or Kenny Brace are usually used in grades I and II injuries.6 Immobilization for a period of three to six weeks followed by rehabilitation exercises can bring back baseline function two-three months post-injury. Most often, there is no residual cosmetic deformity in grades I and II injuries.
In milder acromioclavicular joint dislocation, the most common cause of discomfort is scapular dyskinesia leading to medial scapular or posterior midthoracic pain or discomfort. Scapular stabilization program can be initiated if this is the case.
The optimal treatment for grade III AC dislocation remains inconclusive. There is a multitude of treatment options available at present but the final decision depends on surgeon’s preference. Some authors report that nonoperative management does not differ from operative management in terms of clinical outcomes such as decrease in pain, improvement of strength and range of motion.
Wotjys and Nelson reported that strength in the injured shoulder is equivocal to the uninjured shoulder among patients who did not undergo surgery after follow-up. However, the authors reported that discomfort is greater in the affected area.
Galpin et al had similar findings. Range of motion and strength were similar between the injured and uninjured shoulder despite absence of surgical intervention. This was also reported in several studies.
For grades IV, V and VI, which are considered high-grade, treatment is generally surgical.
The specific surgical technique in acromioclavicular joint dislocation varies, ranging from primary repair of the coracoclavicular ligaments, augmentation with autogenous tissue, augmentation with absorbable and nonabsorbable sutures and other prosthetic materials and coracoclavicular stabilization with metallic screws.10 The most popular surgical procedure is the Weaver-Dunn technique, which was initially described in 1972. It involves the use of the coracoacromial ligament to substitute the torn coracoclavicular ligament and the release of the coracoacromial ligament from the acromial ligament, distal clavicular,resection and transfer of the coracoclavicular ligament to the lateral end of the clavicle.
Several modifications of Weaver-Dunn techniques have been invented.
The Hook Plate is another surgical method for AC joint dislocation. Complications include acromial fractures, plate bending, arthritis, and hook plate eroding.
Stabilization of the AC joint through the application of Bosworth screw between the clavicle and coracoid.6 Other surgical techniques include fixation technique, using various types of materials such as heavy suture, surgical tape, allograft or autograft, and CC ligament reconstruction.
Generally, the indications for surgery are:. Cosmetic . Type III with medial scapular pain, stiffness and difficulty in overhead actions. Functional in overhead athletes . Type IV, V, and VI surgery of necessity. Type III. Late non-unions of lateral end clavicle fractures.
Rehabilitation
Rehabilitation plays a very important role in acromioclavicular joint dislocation.
In Grade I AC dislocation, a sling may be used if there is excruciating pain and discomfort to reduce stress on the affected joint and to decrease inflammation. Sling can only be removed if pain has decreased when the arm is clipped at the side or the pain has subsided during self-care activities. Mobility exercises are started within the first week of injury with the goal of restoring mobility by progressing shoulder range of motion. After the initial week of rehabilitation, restrictions in motions are rare. Exercises to improve the strength are promptly initiated and progressed depending on the patient’s limit. Closed-chain scapular exercises are recommended as initial exercise to assist scapular movement. Isotonic and open-chain exercises can be started once the patient is able to perform forward elevation without symptoms.
In Grade II AC dislocation, immobilization through arm sling is recommended only in the acute stage, to decrease inflammation. After improvement of pain at rest with the arm clipped at the side and pain-free self-care activities, immobilization is stopped. Scapular exercises are immediately started in Grade II AC dislocation. Horizontal abduction with external rotation and prone horizontal extension with the arm at 100 degrees is ideal for middle and lower trapezius movement. However, some authors prefer closed-chain scapular activities to unload the weight of the affected arm, so that the patient can focus on the scapular exercises. Rowing exercises with resistance can also be initiated to combine different movements of the arm. As patients are able to perform these exercises without symptoms, weight can be added to increase resistance.
A systematic review shows that nonoperative management is better among patients with Grade III AC dislocation. Higher complication rates, longer return to function and increased absenteeism from work or sport were noted in patients who were operated on. Minimal immobilization and immediate initiation of rehabilitation to decrease pain and inflammation are recommended. Patients are encouraged to use sling only if they can tolerate it. At present, the recommendation for grade III AC dislocation is a 6- to 12- week trial of rehabilitation to ensure return to baseline function. Patients whose symptoms resolve within six weeks can resume their activities pre-injury and are encouraged to extend rehabilitation up to 12 weeks. Similar to grade II AC dislocations, closed-chain exercises are initiated to improve strength and range of motion. This can be progressed according to patient’s tolerance. Applying braces is another option in order to assist in controlling excessive scapular protraction. A newer version is the S3 brace, which is shirtlike compression device with neoprene and Velcro.
For grades IV, V and VI AC dislocation, surgery is usually indicated.
Prognosis
Post-operative complications include loss of reduction, which was 40% in one study,1 infection rate, which was noted to be 15% in a study, redislocation or implant failure, brachial plexus injury, neuroma, superior migration of the clavicle.
Grades I and AC dislocation theoretically results in little injury to the joint, portending good prognosis. Patients with this type of dislocation usually recovers after a few weeks of rehabilitation and nonoperative techniques but in patients with persistent symptoms and failure to return to baseline function, surgery can be offered. placement of a tendon graft in a bone tunnel. Adequate healing was noted after 12 weeks.4
In patients with brace application to maintain immobilization, rehabilitation is still recommended for active assistive range of motion. This is to address the effects of prolonged immobilization. After the application of a brace, patients are expected to be stiff so devices and exercises can be instituted accordingly.
Return to sport or work depends on the demonstration of symptom-free activities. It can occur as early as two weeks.
Among patients who underwent surgery, patients typically return to their full range of motion (except the ability to perform IR behind the back) after 10 weeks.3 Isotonic exercises or activities are typically withheld for 12 weeks. At eight weeks, closed-chain scapular exercises are encouraged. From 12 to 18 weeks, isotonic strength exercises are allowed (i.e. low row, multilevel rowing exercises). Advanced strengthening exercises can only be done after scapular control has already been achieved.
