What Is Shoulder Impingement?

The shoulder joint is the joint with the largest range of body movements. The shoulder movement occurs not only between the shoulder and humerus joints, but also between the acromion and the humeral head. Kessel calls it the 2nd shoulder or subacromial joint. Under the acromion, there is a gap of 1 ~ 1.5cm in width, with a narrow front and a wide back, with rotator cuffs and long biceps tendon passing. The bottom of the gap is the humeral head, and the top is the coracoid, which is composed of the coracoid process, acromion, and the coracoid ligament connecting the two (Figure 1). It protects the rotator cuff and humeral head from direct damage from the back, upper, and anterior sides. However, it is precisely because of this anatomical structure that when the shoulder joint is abducted, the tissue sandwiched between the coracoid shoulder and the humeral head is susceptible to wear and impact. Under normal circumstances, a humeral sac is separated between the rotator cuff, the long biceps brachii tendon, and the rostral fornix, which functions as a lubricating and cushioning impact. However, under pathological conditions, such as excessive shoulder abduction or long-term cumulative damage, the interstitial tissue is subject to wear. Repeated wear and tear will inevitably exacerbate the inflammatory response of the tissue, increase the pressure in the gap, increase the impact, and eventually cause shoulder impaction. Because the gap below the acromion is narrow and wide at the front, and in normal life and work, most of the upper limb functions are completed by the hand in front of the shoulder joint, not the outside. When the upper arm is abducted, the superior ganglia muscle passes through the front of the acromion, not the lateral side (Figure 2). The shoulder impact is located anterior 1/3 of the acromion, the anterior lower part of the acromioclavicular ligament and the acromioclavicular joint. Neer's anatomical studies and surgical observations revealed that the impact mainly occurred in the anterior 1/3 of the acromion, the anterior inferior part of the acromioclavicular ligament, and the acromioclavicular joint, but not outside the acromion. Lauman divides the subacromial space into front, middle, and back sections (Figure 3). The anterior portion is located below the anterior 2/3 of the coracoid process and the coracoid ligament, including the biceps brachiocephalic long joint tendon, the coracoid ligament, the subscapular muscle, and the coracoid descending sac. The middle part is located in the front half of the acromion, below the 1/3 of the acromioclavicular joint and the coracoid ligament. The posterior portion is located below the posterior half of the acromion, containing the superior subscapularis muscle and a part of the acromion descending sac. Because the subacromial space is narrow and wide before, the lesions mainly occur in the front and middle.

Shoulder impingement

Shoulder impaction syndrome, also known as subacromial pain arc syndrome, is a chronic shoulder pain syndrome caused by repeated friction and impact between the structure under the acromion and the beak and shoulder fornix during shoulder abduction. It is a common disease of people over middle age. The disease includes acromioclavicular bursitis, supraspinatitis, calcification of the supraspinas tendon, rotator cuff rupture, biceps brachialis tendon sheath inflammation, and rupture of the biceps brachii long head (pictured). The common clinical feature is that there is a pain arc during active abduction of the shoulder joint, while the pain of passive movement is significantly reduced or even completely painless.

Shoulder impingement pathophysiology

The shoulder joint is the joint with the largest range of body movements. The shoulder movement occurs not only between the shoulder and humerus joints, but also between the acromion and the humeral head. Kessel calls it the 2nd shoulder or subacromial joint. Under the acromion, there is a gap of 1 ~ 1.5cm in width, with a narrow front and a wide back, with rotator cuffs and long biceps tendon passing. The bottom of the gap is the humeral head, and the top is the coracoid, which is composed of the coracoid process, acromion, and the coracoid ligament connecting the two (Figure 1). It protects the rotator cuff and humeral head from direct damage from the back, upper, and anterior sides. However, it is precisely because of this anatomical structure that when the shoulder joint is abducted, the tissue sandwiched between the coracoid shoulder and the humeral head is susceptible to wear and impact. Under normal circumstances, a humeral sac is separated between the rotator cuff, the long biceps brachii tendon, and the rostral fornix, which functions as a lubricating and cushioning impact. However, under pathological conditions, such as excessive shoulder abduction or long-term cumulative damage, the interstitial tissue is subject to wear. Repeated wear and tear will inevitably exacerbate the inflammatory response of the tissue, increase the pressure in the gap, increase the impact, and eventually cause shoulder impaction. Because the gap below the acromion is narrow and wide at the front, and in normal life and work, most of the upper limb functions are completed by the hand in front of the shoulder joint, not the outside. When the upper arm is abducted, the superior ganglion muscle passes through the front of the acromion, not the lateral side (Figure 2). The shoulder impact is located anterior 1/3 of the acromion, the anterior lower part of the acromioclavicular ligament and acromioclavicular joint). Neer's anatomical studies and surgical observations revealed that the impact mainly occurred in the anterior 1/3 of the acromion, the anterior inferior part of the acromioclavicular ligament, and the acromioclavicular joint, but not outside the acromion. Lauman divides the subacromial space into front, middle, and back sections (Figure 3). The anterior portion is located below the anterior 2/3 of the coracoid process and the coracoid ligament, including the biceps brachiocephalic long joint tendon, the coracoid ligament, the subscapular muscle, and the coracoid descending sac. The middle part is located in the front half of the acromion, below the 1/3 of the acromioclavicular joint and the coracoid ligament. The posterior portion is located below the posterior half of the acromion, containing the superior subscapularis muscle and a part of the acromion descending sac. Because the subacromial space is narrow and wide before, the lesions mainly occur in the front and middle.

Shoulder impingement diagram (11 photos)

Shoulder impingement is a chronic damage process, and its pathological changes can be divided into three stages:

1. Edema and hemorrhage: This is the earliest period of damage to shoulder impingement, which is more common in patients under 25 years of age. Due to excessive abduction of the shoulder joint, the tissue under the acromion is subjected to continuous impact and wear. The scapulohumeral sac and rotator cuff tissue are edema and hemorrhage, and there is usually no obvious tear of the rotator cuff. Conservative treatment is effective, and it is expected to fully restore shoulder function.

2. Fibrosis and tendon synovitis: After early lesions, due to the accumulation of impingement damage, fibrosis and thickening of the acromion, descending sac and rotator cuff tissues occurred. At this time, the symptoms of the patient became more and more obvious, and the patient's age Mostly between 25 and 40 years old. If conservative treatment fails, surgical treatment should be considered. Surgical removal of the hypertrophic acromion bursa, partial removal or cutting of the coracoid shoulder ligament, and resection of the proliferative osteoprosthesis. Because patients are mostly under 40 years old, anterior acromioplasty is generally not performed.

3. Period of rupture of biceps brachialis long tendon and bony change: With further impact wear, the degeneration of rotator cuff and biceps brachii tendon becomes worse, resulting in partial or major tear of the rotator cuff, in severe cases Pathological rupture of the supine tendon or biceps long head tendon can occur. The supraganglar tendon rupture usually occurs before the biceps long head tendon rupture, and the ratio is 7: 1. Due to the damage of the rotator cuff tissue, the stabilizing effect of the rotator cuff on the humeral head is weakened. When the shoulder joint is abducted, the humeral head can be moved up to reduce the gap under the acromion, and the impact between the humeral head and acromion becomes more serious. Changes in bone structure. Sclerosis, hyperplasia, or cystic changes in the anterior lower acromion and large humerus nodules, and notches may appear on the humerus neck. Patients in this period are mostly over 40 years old, and the conservative treatment is not effective. Surgical treatment is often required. Anterior acromioplasty is performed to expand the subacromial space and eliminate impact factors. ^[1]

Clinical manifestations of shoulder impingement

1. Symptoms:

Shoulder pain, mainly around the acromion, sometimes involves the entire deltoid muscle. The pain is worse at night. The patient is afraid of the lateral position. In severe cases, long-term analgesics are needed. Followed by weakness of the affected limb and limited movement. When the upper arm is abducted to 60 ° ~ 80 °, there is obvious pain. Sometimes you can feel that the shoulder joint is stuck by the "object" and cannot continue to lift. At this time, the upper limbs need to be taken in and out, so that the large nodule can pass through the back of the acromion to continue to lift.

2. Signs:

(1) The tenderness is mainly in the area before the acromion and down to the nodule of the humerus.

(2) When the shoulder joint is passively moved, obvious cracking sounds or twisting sounds can be heard.

(3) There is a pain arc of 60 ° ~ 120 ° during active abduction of the shoulder joint, that is, there is no pain at the beginning of abduction, the pain starts at 60 °, and the pain disappears beyond 120 °; the pain is significantly reduced during passive movement It doesn't even hurt at all.

(4) Elderly patients with limited shoulder motion are mainly manifested as restricted abduction, external rotation, and extension.

(5) Positive shoulder impact test. During the examination, the patient takes a seated position. The examiner is at the back, holding the shoulder with one hand to stabilize the scapula; holding the elbow of the affected limb with the other hand, quickly pushing the patient's upper limb forward and upward to make the large humerus nodule and acromion hit Produce pain (Figure 4). Then, 1ml procaine 10ml was used to close the subacromial space, and the above examination was repeated. Those who disappeared were positive for the impact test. This disease is unique to this disease and helps distinguish it from other shoulder conditions. ^[1]

Shoulder impact examination

1. X-ray examination: The X-ray examination of most patients is normal, and the X-ray examination of a few severe patients shows scleroderma sclerosis, cystic degeneration or osteophyte formation (Figure 5A) (Figure 5B), anterior acromion hardening, Bony spurs formed on the lower surface of the acromion, calcified shadows on the supraclavicular muscle, traumatic arthritis of the acromioclavicular joint, and the humeral head moved up to narrow the subacromial space (<0.7cm).

2. Shoulder joint angiography: Shoulder joint angiography is not used as a routine examination method for this disease. It is mainly used to identify that the rotator cuff is partially exacerbated and changes the bone structure over time. Sclerosis, hyperplasia, or cystic changes in the anterior lower acromion and large humerus nodules, and notches may appear on the humerus neck. ^[1]

Shoulder impingement diagnosis

According to clinical manifestations, combined with the results of auxiliary examinations, comprehensive analysis and judgment. ^[1]

Shoulder Impact Treatment Standard

Non-surgical treatment of shoulder impingement

Physical therapy or hot compress of shoulder at early stage of the lesion, oral anti-inflammatory and analgesic drugs. Triangular towel can be used to suspend the affected limb in acute disease, but pay attention to move the shoulder joint under painless conditions to prevent inflammatory tissue adhesion. Avoid movements that can cause shoulder impact, such as lifting heavy objects. Cortisone local injection results are satisfactory. A 7 or 8-gauge injection needle is used. The needle is inserted from the front or the outside of the acromion, and it is placed close to the acromion and backward or inward into the subacromial space (Figure 6). Inject 1% procaine 10ml and 25mg hydrocortisone acetate once a week. Usually 2 or 3 times. For those who have limited range of shoulder joint movement, attention should be paid to functional exercises of the shoulder joint (see Frozen Shoulder) to prevent secondary contracture of the colic-humeral ligament, resulting in frozen shoulder. ^[1]

Shoulder Impact Treatment

The principle of surgical treatment of shoulder impingement is to decompress the space under the acromion in two directions, up and down, to eliminate the impact factor (Figure 7). The following methods are commonly used.

1. Beak and shoulder ligament cut or resection: Make a 6-8cm long longitudinal incision from the acromioclavicular joint, split the deltoid muscle fibers longitudinally, expose the beak and shoulder ligament, cut it, or close it near the acromion resection. The operation is simple, and it is suitable for stage II lesions in which conservative treatment fails. Due to insufficient decompression, it is usually performed simultaneously with other operations.

2. Acromionectomy: All acromion can be decompressed by three gaps at the same time, and the decompression is sufficient. However, the acromioclavicular joint was damaged by surgery, and the attachment points of the deltoid and trapezius acromion were lost, which weakened the biceps muscles. Due to the loss of the beaked shoulder dome, if the rotator cuff is weak, the subluxation of the humeral head can occur, and the shoulder appearance defect caused by the loss of the acromion after surgery is now rarely used.

3, lateral acromioplasty: remove 2/3 of the lateral acromion, and remove the coracoid shoulder ligament to make the anterior part of the subacromial space fully decompressed. If the left acromion and the anterior and inferior part of the acromioclavicular joint are also removed, the middle part can also be fully decompressed (Figure 8). This method has the advantage of retaining the acromioclavicular joint, but it will still lose some dead point of the deltoid muscle after surgery, and cause the appearance defect of the shoulder.

4. Anterior acromioplasty: In view of the pathological anatomic characteristics of the shoulder impaction lesions mainly in the front 1/3 of the acromion and the anterior lower part of the acromioclavicular joint, Neer proposed the anterior acromioplasty with partial removal of the anterior acromion. The impact factor is eliminated, and the deltoid acromion attachment portion is retained, thereby avoiding the appearance defect of the shoulder and damage to the deltoid muscle strength caused by the acromion resection or full acromectomy. The surgical trauma is small, and the function recovery is fast, which is an ideal treatment method.

(1) Indications:

First, patients with impingement of shoulder over 40 years of age who have been undergoing conservative treatment for more than half a year and their symptoms are getting worse.

The second is that the rotator cuff is completely torn with rotator cuff radiography. Anterior acromioplasty is performed at the same time as rotator cuff repair.

Third, those with pathological rupture of the long head tendon of the biceps due to shoulder impingement, while performing anterior acromioplasty while fixing the ruptured tendon in the internodal groove.

Fourthly, patients with stage II shoulder impulse who are under 40 years of age. When the acromion bursa is removed, it is found that there is a significant hyperplasia in the front edge of the acromion and the front of the lower surface.

Fifth, frozen shoulder patients with colic-humeral ligament contracture, who have not improved their function after more than half a year of exercise, should undergo anterior acromioplasty while cutting the colic-humeral ligament.

(2) Surgery method:

Use high brachial plexus anesthesia or general anesthesia. The patient took a supine position with a high shoulder pad. The affected upper limb was disinfected and wrapped in a sterile towel to prepare the upper limb during the operation. The skin incision circumvented the acromion from the back of the acromion to the coracoid process and was S-shaped, about 10 cm long. Cut the subcutaneous tissue and deep fascia to see the deltoid muscle. In the front of the deltoid muscle, the deltoid muscle is separated longitudinally between the acromion and the coracoid process, that is, the coracoid process and coracoid shoulder ligament are exposed. Move the upper limbs to observe the impact of the large humerus nodules and the coracoid humerus. Pull the upper extremity downwards, and check whether the acromion bursa and supraganglia tendon are diseased. Use your fingers to explore the osteophyte or protrusion at the lower edge of the acromion, and estimate the thickness of the acromion to determine the extent of resection. First cut the coracoid shoulder ligament near the coracoid process, and then use a thin bone knife to cut the anterior and inferior protrusion of the acromion along with the attached coracoid ligament from front to back (Figure 9 A. Incision; B. Surgery revealed; C. Front acromion formation). When cutting the bone, the surgeon supported the bone knife in one hand and the acromion in one hand, and the assistant struck the bone knife to prevent injury to the upper acromion. The lower anterior 1/3 of the acromion is usually excised to preserve the deltoid acromion attachment. The bone-cutting surface should be smooth and flat, and the cut bone fragments should be cleaned up, so as to avoid the re-formation of bone spurs, which will affect the surgical effect. Further examination of the tissue in the space below the acromion. With chronic acromion bursitis, the enlarged and thickened bursa is removed. For rotator cuff tear, repair accordingly. For those who have biceps brachialis tendon sphingomyelitis or pathological rupture, the long head tendon is fixed in the humeral nodular groove or moved to the coracoid process. The humerus nodules with osteophyte protrusions or other irregularities should be excised or trimmed. Those who have calcium deposits on the psoas muscle should be removed. When exploring the acromioclavicular joint, you should consider acromioclavicular resection if:

First, preoperative X-ray films confirmed that the acromioclavicular joint was significantly degenerative and had clinical symptoms.

The second is that during the operation, bone spurs were found on the lower surface of the acromioclavicular joint and the superior tendon was worn.

The third is the need to expose the superior tendon on a larger scale to repair extensive torn rotator cuffs.

Generally, the outer end of the clavicle is resected, and the resection range from the outer end to the attachment of the coracoid ligament, which is about 2.5 cm long. When the second case occurs, only the lower part of the acromioclavicular joint is excised from the bone spurs or obliquely to expand the subacromial space and facilitate the supramastral muscles to slide. After surgery, move the upper limbs again to check whether the impact on the shoulder is completely relieved. For patients with limited shoulder movement before surgery, gently move the shoulder joint gently to loosen adhesions and increase the range of shoulder movement. Finally, the deltoid muscle was sutured, and a negative pressure drainage was placed in the incision. The upper extremity was suspended with a triangle towel after surgery, and the shoulder joint was passively moved 1 to 2 times a day. After 3 weeks, active shoulder exercise was started, supplemented with physical therapy.

5. Acromion bursa resection: The acromion bursa is located between the rotator cuff and the rostral fornix, adjacent to the three areas below the acromion. When the synovial sac develops inflammation and enlarges and thickens, it will obviously increase the pressure in the space under the acromion and cause shoulder impingement. Surgical removal of the diseased synovial sac can reduce the contents of the acromion space and relatively increase the acromion space to avoid impacts under the acromion. This method is mainly used for shoulder impingement caused by acromion bursitis.

6. Scapulo-pelvic margin osteotomy: Slamm advocates scapulo-pelvic margin osteotomy, which moves the glenohumeral joint downward to increase the subscapular space (Figure 10). Surgical method: Make a posterior incision along the scapula, pull down the inferior ganglia muscles to expose the back of the shoulder joint, determine the margin of the glenoid-upper and lower boundaries, identify the scapular glenoid joint surface, and obliquely move the scapula neck 1 cm away from the margin of the glenoid Cut off, pull the upper limb to move it forward, inward, and downward, and insert a bone screw above it to prevent it from shifting upwards. This operation can move the shoulder joint down by 1.5cm, no external fixation is required after surgery, early exercise can be exercised, and functional recovery is satisfactory. ^[1]