DeSeze and Robinson et al. investigated the specific configuration of the subacromial joint and the trajectory of the greater tuberosity and proposed the nomenclature of the second shoulder joint. It is also referred to as the subacromial joint. It is a clinical syndrome in which a series of symptoms and signs occur due to the impingement of the subacromial tissues during shoulder supination and abduction due to anatomical or kinetic reasons.
English name: impingement syndrome
Department: Orthopedics
Prevalent group: 10 years old to elderly
Common site: Bursa, tendon
Common causes: Abnormal morphology of the anterolateral end of the acromion, osteophyte formation, osteophyte formation of the greater tuberosity of the humerus, hypertrophy of the acromioclavicular joint, etc., resulting in a decrease in the acromion-humeral head spacing
Common symptoms: chronic dull pain in the front of the shoulder, pain or aggravation of symptoms in the range of 60° to 120° of arm elevation, etc.
1. Etiology
The abnormal shape of the anterolateral end of the acromion, the formation of bony redundancy, the formation of bony redundancy in the greater tuberosity of the humerus, the hypertrophy of the acromioclavicular joint, and other causes that may lead to a decrease in the distance between the acromion and the humeral head can cause extrusion and impingement of the subacromial structures. The majority of this impingement occurs in the anterior 1/3 of the acromion and below the acromioclavicular joint. Repeated impingement can lead to injury, degeneration, and even tendon rupture of the bursa and tendon.
2. Clinical manifestations
The impingement sign can occur from the age of 10 to the elderly. Some patients have a history of shoulder trauma, and a significant number of patients are associated with long-term overuse of the shoulder joint. The symptoms are caused by repeated injury to the rotator cuff and bursa, tissue edema, hemorrhage, degeneration and even tendon rupture. Early rotator cuff hemorrhage and edema are similar to the clinical manifestations of rotator cuff rupture, making the diagnosis easily confused. It is important to differentiate the impingement signs from other causes of shoulder pain and to distinguish which stage the impingement signs belong to, as this is very important for the diagnosis and treatment of the disease.
The common symptoms of each stage of impingement are
1. Chronic dull pain in front of the shoulder
The symptoms are aggravated during supination or abduction activities.
2. Pain arc sign
The pain or symptoms are aggravated when the affected arm is lifted in the range of 60° to 120°. The pain arc sign is only present in some patients and is sometimes not directly related to the impingement sign.
3.Graveling sound
The examiner holds the anterior and posterior edges of the shoulder crest of the affected arm with the hand, and can find gravelly sounds when the upper arm is rotated internally and externally, and when it is flexed and extended forward and backward. The conspicuous gravelly sound is usually seen in stage 2 impingement sign, especially in those with complete rotator cuff rupture.
4.Weakness of muscle strength
Significant muscle weakness is closely associated with the late impingement sign of extensive rotator cuff tears. In early rotator cuff tears, the abduction and external rotation of the shoulder is reduced, sometimes due to pain.
5.Impaction test
Neer II believes that this test is of great clinical significance in identifying impingement signs.
6.Impact injection test
Inject 10 ml of 1% lidocaine into the subacromial bursa along the underside of the acromion. If there is no shoulder joint movement disorder before and after the injection, and the shoulder pain disappears temporarily and completely after the injection, then the impingement sign can be established. If the pain is only partially relieved after the injection, and there is still joint dysfunction, then “frozen shoulder” is more likely. This method can be used to differentiate shoulder pain caused by non-impingement signs.
Examination
1.X-ray examination
X-rays should routinely include anteroposterior and axial views of the upper arm in neutral, internal and external rotation to show the acromion, humeral head, glenoid and acromioclavicular joint, and can identify subacromial calcium deposits, glenohumeral arthritis, acromioclavicular arthritis, abnormal development of the acromion epiphysis and other bone disorders.
X-rays of the supraspinatus tendon exit (Y-images) are important for understanding structural narrowing of the exit and for measuring the acromion-humeral head spacing.
X-rays are not specific for the diagnosis of stage 1, 2 and 3 impingement, but are useful for the diagnosis of subacromial impingement when the following radiographic signs are present.
(1) Large nodule wart formation. This is due to repeated impingement of the greater tuberosity with the acromion and usually occurs at the crest of the supraspinatus stop.
(2) Hyperechogenic and hooked acromion.
(3) Dense, irregular or osteophytic formation below the acromion. The rostral shoulder ligament is impressed or repeatedly stretched, resulting in the formation of osteophytes underneath the anterior shoulder crest.
(4) Degeneration and hyperplasia of the acromioclavicular joint, resulting in the formation of a downwardly protruding bony superfluity, resulting in narrowing of the supraspinatus outlet.
(5) The distance between the acromion and the humeral head (A-H distance) is reduced. The normal range is 1.2 to 1.5 cm, <1.0 cm should be stenosis, and ≤0.5 cm suggests the presence of an extensive rotator cuff tear. Complete rupture of the long head of the biceps tendon, loss of downward compression of the humeral head, or other causes of dynamic imbalance may also result in a narrowing of the a-h spacing.
(6) Encroachment and resorption of bone beneath the anterior acromion or acromioclavicular joint; decalcification, encroachment and resorption of the greater tuberosity of the humerus or dense changes of bone.
(7) Rounding and blunting of the greater tuberosity of the humerus, loss of the boundary between the articular surface of the humeral head and the greater tuberosity, and deformation of the humeral head.
The presence of impingement sign should be considered in combination with clinical anterior shoulder pain symptoms and positive impingement test in points 1 to 3 above. Point 4 to 7 X-ray signs belong to the late manifestation of impingement sign.
In addition to static radiographs and measurements in different positions, dynamic observation under X-ray surveillance should be done. In the direction and angle of the impingement sign, the affected arm is made to do repeated forward and abduction movements to observe the relative anatomical relationship between the greater humeral tuberosity and the rostral arch of the acromion. The dynamic observation method is particularly important for the diagnosis of dynamic impingement.
2.Shoulder arthrography
For the late stage of impingement sign complicated by rotator cuff rupture, imaging is still the most specific diagnostic method for complete rotator cuff rupture.
Complete rotator cuff rupture can be diagnosed if contrast contrast agent is found to spill from the glenohumeral joint into the subacromial bursa or subdeltoid bursa during shoulder arthrography. The morphology of the long head of the biceps tendon and the filling of the tendon sheath can be observed to determine whether the long head of the biceps tendon has ruptured. Small rotator cuff ruptures and incomplete rotator cuff ruptures are difficult to visualize on imaging. Subacromial bursa imaging is also useful in the diagnosis of complete rotator cuff tears, but its usefulness is limited by the variability of the subacromial bursa morphology and the overlapping nature of the visualization.
3.MRI examination
With the accumulation of experience, the specificity of MRI examination for the diagnosis of rotator cuff injury has been increasing, and it has gradually become one of the routine diagnostic methods.
4.Arthroscopy
Arthroscopy is an intuitive diagnostic method that can detect the extent, size, and shape of tendon rupture, and has diagnostic value for partial rupture of the articular surface of supraspinatus tendon and biceps longus tendon lesions, and can observe bursal lesions and rupture of the bursal surface of supraspinatus tendon from within the subacromial bursa. In addition, treatment can be performed along with the diagnosis, such as planar decompression of the subacromial space, lesion removal and resection of the anterior acromion bursa, and anterior acromioplasty can be performed. Arthroscopy is an invasive examination method and needs to be performed under anesthesia.
Diagnosis
Diagnosis can be established based on medical history, clinical symptoms and signs and tests, X-ray, MRI, ultrasonography, and arthrography.
Treatment
1.Subacromial impingement sign treatment method selection
The choice of treatment method depends on the cause and stage of impingement.
(1) Non-surgical treatment for impingement stage 1. In the early stage, corticosteroid and lidocaine injection in the subacromial space can achieve obvious pain relief effect. Oral non-steroidal anti-inflammatory and analgesic agents can promote the edema to subside and relieve the pain, while physical therapy can be applied.
(2) Impingement sign stage 2 The stage of chronic supraspinatus tendonitis and chronic bursitis is still based on non-surgical treatment. Physiotherapy and sports therapy should be used to promote the rehabilitation of joint function and change the labor posture and operating habits to avoid the recurrence of subacromial impingement.
(3) Stage 3 impingement is associated with pathological changes such as supraspinatus tendon rupture and biceps longus tendon rupture, which are indications for surgical treatment. For extensive rotator cuff tears, subscapularis transposition or supraspinatus nudge repair can be used to reconstruct the function of rotator cuff, while anterior acromioplasty should be done routinely to remove the anterolateral part of the acromion and cut the rostral shoulder ligament so that the repaired tendon can avoid further impingement. After surgery, the affected limb should be fixed with zero degree traction or shoulder herringbone cast, and after 3 weeks, the fixation should be removed for rehabilitation training.
2.Non-surgical treatment of subacromial impingement
The duration of non-surgical treatment varies from 12 to 18 months. The use of arthroscopy in subacromial decompression has reduced the complications of surgical operation, so the duration of non-surgical treatment may be shortened appropriately. The duration of non-operative treatment depends on the patient’s specific situation, but most reports suggest that the duration of non-operative treatment should not be less than 6 months.
3.Surgical treatment of subacromial impingement
Surgical treatment is indicated for patients with stage 2 and 3 subacromial impingement who have failed non-surgical treatment. The surgery consists of subacromial decompression and rotator cuff repair. Subacromial decompression is the first choice, which includes cleaning the inflamed subacromial bursa, removing the rostral shoulder ligament, the anterior and inferior portion of the acromion, and the osteochondral tuberosity of the acromioclavicular joint or even the entire joint. Resection of the acromioclavicular joint is not routinely performed and is indicated only when there is pressure pain in the acromioclavicular joint and the acromioclavicular tuberosity is determined to be part of the cause of the impingement sign. Today, decompression of the subacromial space can be accomplished by either the traditional open technique or Ellman’s arthroscopic technique.
Prognosis
Subacromial impingement usually has a satisfactory outcome when the diagnosis is made in a timely manner, the cause and pathological changes are identified, and the patient is treated properly.