CHAPTER 10
Acromioclavicular Injuries
Definition
The acromioclavicular joint is a diarthrodial joint found between the lateral end of the clavicle and the medial side of the acromion [1]. The joint is surrounded by a fibrous capsule and stabilized by ligaments. The acromioclavicular ligaments cross the joint. Three ligaments begin at the coracoid process on the scapula and attach to the clavicle (trapezoid and conoid ligaments) or the acromion (coracoacromial ligament) (Fig. 10.1). This complex provides passive support and suspension of the scapula from the clavicle while allowing rotation of the clavicle to be transmitted to the scapula [1,2].
Injuries to the acromioclavicular complex are graded I to VI (Table 10.1). Injuries to the acromioclavicular joint were originally classified as grades 1, 2, and 3 by Tossy [3]. This classification was extended to include more complicated injuries, and grades 4, 5, and 6 were described. The extended grading system uses roman numerals [4].
The coracoacromial (lateral) ligament is not disrupted in injuries to the acromioclavicular joint. Therefore the fibrous connection persists between structures of the scapula emanating anteriorly and posteriorly [5]. In rare instances, there is an intra-articular fracture of the distal clavicle in addition to the ligamentous injuries [6].
There are few demographic data on differences of the disorder based on gender. Problems with the acromioclavicular joint can be associated with trauma and with overhead and throwing activities. Higher grade injuries are more likely to be due to trauma, such as auto accidents, falls, or sports injuries [7]. Concomitant injuries can vary on the basis of age; 86% of individuals older than 50 years have rotator cuff tears [8].
Most patients with grade I or grade II injuries respond to conservative measures and become asymptomatic within 3 weeks [9].
Symptoms
Patients often provide a history of trauma to the shoulder or in the vicinity of the acromioclavicular joint. Participants in contact or collision sports (e.g., football, downhill skiing) are particularly susceptible. Patients seek care because of pain in the anterior and superior aspect of the shoulder [2]. This radiates into the base of the neck and the trapezius or deltoid muscles or down the arm in a radicular pattern [2,5,10].
Patients may describe pain brought on by activities of daily living that bring the arm across the chest (e.g., reaching into a jacket pocket) or behind the back (e.g., tucking in a shirt). Pain can also occur with shoulder flexion (reaching overhead) or with adduction of the arm across the chest. Patients may not have pain at rest and may be able to complete many activities without discomfort.
Physical Examination
Appropriate examination for suspected acromioclavicular injuries includes an examination of the neck and shoulder joint and girdle to eliminate the possibility of a radiculopathy or referred pain. Patients should have normal neck and neurologic examination findings. The presence of neurologic or vascular injury suggests that a greater degree of trauma has been sustained [5].
On inspection, there may be a raised area at the acromioclavicular joint. This is caused by depression of the scapula relative to the clavicle or swelling of the joint itself. This area is commonly tender to touch. On active range of motion, the patient may complain of pain or wince near the extreme of shoulder flexion.
Shoulder range of motion is typically within normal limits. Supporting the arm at the elbow and gently directing the arm superiorly may decrease the pain and allow more complete assessment of the patient’s shoulder range of motion. The pain may become worse as the shoulder is further flexed, whether it is done actively or passively. This is in distinction to impingement syndromes, which often hurt at a particular point in the arc of motion but are painless as the motion proceeds. Pain is typically absent with static manual muscle testing of the rotator cuff. Rotator cuff injuries will be painful with activation of the muscles of the rotator cuff. These problems are best identified with the shoulder in a neutral position (i.e., elbow next to the body) because the rotator cuff muscles are in a lengthened position and are easily made symptomatic.
Special tests to identify acromioclavicular joint disease attempt to compress the joint. The most common test is the cross-body adduction test (Fig. 10.2). The shoulder is abducted to 90 degrees and the elbow is flexed to the same degree. The clinician then brings the arm across the patient’s body until the elbow approaches the midline (or the patient reports pain) [2].
Other tests help differentiate between impingement syndrome and acromioclavicular joint pain. If the shoulder is passively flexed while it is internally rotated, the greater tuberosity can pinch (impinge) the supraspinatus tendon and subacromial bursa. The same test performed with the shoulder externally rotated will compress the acromioclavicular joint without impinging the subacromial space [11]. In the active compression test, the shoulder is flexed to 90 degrees and then adducted to 10 degrees (Fig. 10.3). The patient first maximally internally rotates the arm and then tries to flex the shoulder against the clinician’s resistance. This puts pressure on the acromioclavicular joint and may reproduce pain if disease is present. The test is repeated with the shoulder in full external rotation. This will put stress on the biceps tendon and its labral attachment while excluding the acromioclavicular joint [12].
In the acromioclavicular resisted extension test, the shoulder is abducted to 90 degrees and adducted across the body to 90 degrees (Fig. 10.4). The examiner resists active shoulder extension. A positive test result reproduces pain in the acromioclavicular joint. A combination of these tests will improve the diagnostic accuracy over isolated tests [13].
The Paxinos sign, along with bone scan, has a high degree of diagnostic accuracy in acromioclavicular joint disease [14]. The examiner stands behind the patient and, using the hand contralateral to the affected shoulder, stabilizes the clavicle and pushes the acromion into the clavicle with the thumb. The test response is considered positive if pain occurs or increases in the region of the acromioclavicular joint; the test response is considered negative if there is no change in the pain level (Fig. 10.5).
Functional Limitations
Reaching up, reaching across the body, and carrying heavy weights are limited because of pain. Patients may have no pain at rest and little or no pain with many activities. Patients may complain of difficulty with putting on a shirt, combing the hair, and carrying a briefcase or grocery bag. Most recreational activities, especially those that incorporate throwing, will be limited as well. Sleep may be affected because of pain, especially when rolling over on the affected side.
