Shoulder impingement syndrome (SIS) is a condition characterized by compression and a subsequent inflammation of any structure in the shoulder. Patients typically experience shoulder pain which is worsened by activity.
The commonest symptom of shoulder impingement syndrome is pain in all surfaces of the shoulder . The pain may radiate to the arm up to the elbow down the lateral aspect of the biceps muscle. However, patients with mild shoulder impingement may present with no symptoms at all, while some may experience pain at the start of aggravating movements and resolves as the patient continues. Often times, these patients may only experience shoulder pain while resting from such activities.
The symptoms of shoulder impingement syndrome are aggravated by activities which compress the subacromial bursa or rotator cuff tendons. These activities include lifting, pushing, pulling, lying on the affected side, carrying heavy objects, swimming, ball serving in racket sports, and painting.
Overtime, the patient may experience reduced range of motion of the shoulder affecting performance in sports and work when work-related activities are the aggravating factors. There is tenderness of the shoulder on palpation of its superior and outer aspects. Weakness of the shoulder is noticed with those activities which aggravate the impingement.
Imaging studies are the initial diagnostic tests to be ordered in the diagnosis of shoulder impingement syndrome. Required imaging studies include plain radiographs and MRI arthography .
The plain radiographs are taken in the axillary, anteroposterior, and Y-views and they reveal minimal changes , which may also include changes in the greater tuberosity, acromial variations, and remodelling of the glenoid rim.
MRI is the diagnostic modality of choice in making a diagnosis of shoulder impingement syndrome. An MR arthrography clearly reveals tears of the supraspinatus and infraspinatus with lesions of the posterior and inferior glenoid labrum .
Special orthopedic tests for shoulder impingement syndrome include hawkins-kennedy, Neer's, and impingement sign. If pain is present in any of these tests, it suggests shoulder impingement syndrome. Neer's test is performed with the patient in a sitting or standing position with the physiotherapist stabilizing the clavicle and scapula with one hand and internally rotating and passively flexing the patients arm. If the pin is reproduced with this maneuver, the test is considered positive and indicative of shoulder impingement syndrome.
Stage 1 impingement syndrome is managed with conservative treatment strategies which include rest and avoidance of the aggravating and precipitating activities. Physical therapy and occupational therapy are very important in managing patients at this stage of the disease. These therapies would serve to strengthen the muscles of the shoulder girdle and rotator cuff muscles, while occupational therapy counsels on job modifications if the patients job involves activities which cause or aggravate the symptoms. In these patients, pain relief with non-steroidal inflammatory drugs and ice packs are beneficial, the ice packs are applied severally up to 20 minutes each time. A sling is avoided in the management of shoulder impingement syndrome because the resulting immobilization may predispose to adhesive capsulitis.
Stage 2 impingement requires more intense physical therapy. Range of motion is restored with isometric stretch exercises preferable with a fixed weight. These exercises are performed on a regular basis to achieve effectiveness. Some sport activities including throwing, swimming, and serving motions are incorporated in the physical therapy. Other physiotherapy treatment modalities include transverse friction massages, ultrasound therapy, and electro galvanic stimulation.
Corticosteroid injections (with lidocaine) are essential for cases which do not improve with conservative and physical therapy. Steroid injections are all indicated for patients with a surgical pathology in the shoulder such as a subacromial spur, who are unsuitable for surgery. Corticosteroid injections are both therapeutic and diagnostic. Diagnostically, it helps to distinguish rotator cuff impingement from other shoulder pathologies. If the patient still records non resolution of symptoms after corticosteroid injections in the presence of normal plain radiograph findings, shoulder impingement is unlikely. Therefore, the diagnostic physical examination tests should be done after corticosteroid injections to detect if the pain is unresolved  . Steroid injections are also useful for temporary pain relief in patients considered for surgery.
In 60-90% of cases of shoulder impingement syndrome, a conservative management is successful, however, if after 3 months of conservative treatment, no improvement is observed, other pathologies are considered and investigated while referring the patient for surgical review .
With prompt diagnosis and appropriate treatment, the outcome of shoulder impingement syndrome is generally good with 60-90% of patients showing complete recovery with medical treatment. Surgery also provides significant relief of symptoms in patients in whom conservative treatment fails.
The etiological factors responsible for shoulder impingement syndrome may be classified as primary or secondary. Primary causes include disease of the components of the supraspinatus space or coracoacromial arch, directly narrowing the supraspinatus space causing the impingement of the tendon. These include acromial pathologies including calcium deposits in the subacromial space and abnormal hooking of the acromion , arthrosis of the acromioclavicular joint, hypertrophy of the corocoacromial ligament, direct or repeated trauma to the shoulder, coracoid impingement, and chronic subacromial bursitis.
Secondary causes of shoulder impingement are abnormalities of other adjacent structures which in turn indirectly cause impingement by affecting the primary structures forming the supraspinatus space. These include muscle overload and imbalance, scapular dyskinesia , glenoid labral lesions, laxity of the long head of biceps tendon, laxity of the glenohumeral joint, and paralysis of the trapezius muscle.
Trauma, both direct and repeated microtrauma, is a common cause of shoulder impingement in young and middle-aged adults, most of whom are under the age of 40 years and who participate in activities which involve frequent abduction and external rotation of the arms. These activities are common in sports which require overhead movement of the arm such as racket sports .
The skeletal makeup of the shoulder or pectoral girdle consists of the humerus and scapula interconnected by the glenohumeral and acromioclavicular joints, and the scapulothoracic and acromiohumeral articulations.
There are a number of structures which stabilize the shoulder. These include the rotator cuff muscles, shoulder girdle muscles, scapulothoracic motion, and the long head of the biceps tendon, all of which provide dynamic stabilization for the shoulder. Structures which stabilize the shoulder when not in motion, called static stabilizers, include the articular structures, joint capsule, glenohumeral ligaments, and the negative forces in the joint. The soft tissues are the major stabilizers of the shoulder joint.
The rotator cuff muscles consist of 4 muscles which produce abduction, external and internal rotation movements of the shoulder. These muscles include supraspinatus, infraspinatus, teres minor, and subscapularis. The supraspinatus muscle controls abduction, while the infraspinatus and teres minor muscles produce the external rotation of the shoulder, and the subscapularis causes internal rotation of the shoulder. These rotator cuff muscles are powerful dynamic stabilizers of the shoulder, stabilizing the head of the humerus on the glenoid fossa, and working in concert with the deltoid muscle to move the arm upwards. This combination of rotator cuff muscles and deltoid accounts for 45% of the abduction strength and 90% of the strength of external rotation of the shoulder.
The acromion, acromioclavicular joint, and the coracoacromial arch form a space on the head of the humerus and the glenoid called the supraspinatus outlet which serves to allow the passage of the supraspinatus tendon. Problems with the supraspinatus outlet causing impingement of the tendon are the commonest causes of the shoulder impingement and rotator cuff syndromes. A study by Bigliani et al first described how anatomic variations in the sizes and shapes of the acromial process cause shoulder impingement .
Cadeveric studies reveal 3 types of variations in the anatomy of the acromial process. In type 1, the acromion is flat, in type 2, it is curved, while in type 3 the acromion is hooked anteriorly. Type 2 was observed to be the most common anatomic variant with a prevalence rate of 43%. The prevalence rates of types 1 and 3 were 17% and 40% respectively. Type 3 anatomic variation was most commonly associated with full thickness rotator cuff tears.
Other sites of impingement within the supraspinatus outlet include the coracoacromial ligament and the inferior surface of the acromioclavicular joint. The corocoacromial ligament is a common site because the ligament is prone to thickening. When the humerus assumes an internally-rotated and forward-flexed position, the impingement sites are further compressed by forcefully placing the greater tubercle of the humerus into the inferior surface of the acromion and coracoacromial arch.
Impingement can occur outside the suprasinatus outlet and may result from weakness of the rotator cuff muscles sequel to a subscapularis mononeuropathy or a cervical spinal pathology. This, as well as severe rotator cuff tears, in turn cause depression of the head of the humerus and shoulder impingement. Thickening of the subacromial bursa and the rotator cuff tendons can also cause shoulder impingement.
The most important preventive measures against shoulder impingement syndrome include educating at-risk individuals about activities which precipitate and aggravate the symptom and teaching them on ways to circumvent the occurrence. The athletes are instructed on proper warm-ups before sporting activities, and strengthening exercises for the shoulder muscles to increase the stability of the shoulder.
Shoulder impingement syndrome is characterized by compression or impingement of a number of structures in the shoulder. Overtime, this compression may cause injury and tears to the structure involved .
Shoulder impingement syndrome occurs in three stages: Stage 1 is the initial stage of the disease and it occurs in people under the age of 25 years. The pathology consists of acute inflammation of the shoulder structures involved. Stage 2 occurs in people aged between 25 and 40 years and it consists of weakening of the tendons of the shoulder muscles. It is caused by chronic inflammatory changes caused by the long-standing impingement. Stage 3 is the stage in which the structure involved is injured as in a rotator cuff tear or a bicipital tendon rupture. At this stage, surgical repair is recommended.
The causes of shoulder impingement syndrome include abnormalities of the bones, joints, or other musculoskeletal components of the shoulder joint which stabilize the shoulder. These include hypertrophy of the coracoacromial ligament, laxity of the glenohumeral joint, and abnormal structure of the acromion. These abnormalities basically narrow the supraspinatus space or impingement interval through which the supraspinatus tendon passes causing impingement of this tendon.
Shoulder impingement syndrome presents with shoulder pain which is worsened by activities involving frequent abduction and external rotation of the arms.
Diagnosis of shoulder impingement syndrome is essentially by physical examination and imaging studies. Nerve block with lidoaine is also diagnostically useful in distinguishing shoulder impingement syndrome from other differential diagnoses.
Treatment of shoulder impingement syndrome is largely conservative, however corticosteroid injections and surgery are considered in recalcitrant cases.
Shoulder impingement syndrome is a common shoulder condition in adults who take part in sporting and certain job activities. This condition is characterized by compression or impingement of a component of the shoulder architecture causing symptoms mainly shoulder pain which is worse on moving the shoulder.
The main structures impinged in this syndrome are the rotator cuff muscles, a group of 4 muscles which serve to rotate the arm and move it outward.
There is a space in the shoulder called the impingement interval or supraspinatus outlet which becomes narrow as the arm is moved away form the body (abducted). This space occurs between the head of the humerus and some joints in the shoulder. Any condition which causes further narrowing of the impingement space would cause impingement or compression of the content of the space which is the supraspinatus tendon.
The factors which predispose to shoulder impingement include bony deformities or diseases in the shoulder and laxity of the structures which stabilize the shoulder.
Shoulder impingement syndrome is most commonly seen in young adults under the age of 40 years who take part in sporting activities which requires frequent outward movement and rotation of the arms. These spots include racket sports, baseball, swimming, and javelin throws.
Typical symptoms of shoulder impingement includes shoulder pain which is worsened by moving the arms above the head or behind the back. Weakness of the shoulder and difficulty moving the shoulder in all directions are also common symptoms of this disease.
Shoulder impingement is diagnosed by imaging studies including the X-rays and the magnetic resonance imaging (MRI). The doctors could also perform physical tests manoeuvering the arms and shoulder to detect if the pain is caused by impingement. Another test is by injecting an anesthetic drug into the shoulder to see if pain would subside. If the pain doesn't subside, shoulder impingement is unlikely. X-rays would help show the bony deformities of the injured tendons in the shoulder.
In the early stages of shoulder impingement, treatment would include resting the shoulder, avoiding the aggravating activities, using over-the-counter pain killers, and application of ice packs. A physiotherapy program is also necessary at this stage to strengthen the shoulder muscles which also serve to stabilize the shoulder. The ice packs should be applied several times on the affected shoulder for up to 20 minutes each time.
In cases where the above treatment strategies fail and in the late stages of the disease, injecting corticosteroid solution into the shoulder helps to relieve the pain. If symptoms still remain unresolved after a period of regular steroid injections, doctors would investigate for other causes of the symptoms, and surgery is opted for. In these persistent cases, tears of the rotator cuff tendons may be the culprit.