What is Shoulder impingement syndrome?
Shoulder pain is ranked third amongst the musculoskeletal system disorders, following low back pain and knee or neck pain. Also termed as Subacromial impingement syndrome, it exhibits a prevalence of 44-70% of all shoulder pains. The human shoulder comprises of the humerus, scapula and clavicle. The scapula is made up of an acromian process and a coracoid process which together form the glenohumeral articulation. There are four morphological types of acromian process: straight or flat, curved, hooked and convex. The rotator cuff comprises of four muscles supraspinatus which arises from the medial two-thirds of scapula, assists in the initial 0 to 15 degrees of shoulder abduction and externally rotates the arm;infraspinatus which runs posteriorly and attaches immediatedly below the supraspinatus on the humerus, and helps in external rotation of the shoulder;teres minorwhich is a long and narrow muscle attaching below the infraspinatus on the humerus, and assist in external rotation of the shoulder; and subscapularis which is a large triangular muscle preventing the anterior dislocation of shoulder during abduction. These rotator cuff muscles stabilize the shoulder in dynamic equilibrium. They work synchronously to stabilize the humeral head against the glenoid, thus providing a fulcrum to the supraspinatus and deltoid to work. The fluid-filled subacromial bursa in the shoulder reduces friction in the supraspinatus and deltoid. In comparison toother joints in the body, the shoulder has maximum range of motion. The glenohumeral joint exhibits six degrees of freedom, three rotations and translations each. Shoulder impingement syndrome is a multifactorial, complex combination of symptoms caused by the traumatized and inﬂamed supraspinatus tendon crossing the narrow restricted subacromial arc.
Causes of Shoulder impingement syndrome
o Variant morphology of the acromion and acromioclavicular joint pathologies such as spurs and osteophytes, obtrude the subabcromial space causing entrapment of supraspinatus and subacromial bursa.The subacromial space can also be obscured by acute or chronic inﬂammation termed as bursitis, thickening or calcifcation of the coracoacromial ligament, and by fractures involving the proximal part of humerus.
o Shape of acromion: According to reports a normal subacromial arch is seen in 6% of impingement patients, whereas 46% of the patients demonstrated an aggressive arch morphology. In another report it was recorded that 36% of the impingement patients had type 1 acromion, 24% had type 2 acromion and 40% had type 3 acromion.
o Degeneration of acromioclavicular joint: The intra-articular disc of acromioclavicular joint tends to degenerate due to trauma or increasing age. Anatomical angle of glenohumeral abduction between the rotator cuﬀ and the acromioclavicular joint is 60°. At 70° of abduction, the greater tuberosity comes to lie directly below the acromioclavicular joint, and at this juncture even minor encroachmentmay cause rotator cuﬀimpingement.
o Forward elevation and internal rotation of the shoulder is carried out by the coracoacromial arch as it comes in contact with the rotator cuﬀ. A large coracoid insertion has reported significant association with degeneration of the rotator cuff.
o Osacromiale: It is the condition of failed fusion of epiphysis of the anterior part of acromion, which if unstable tilts anteriorly and induces impingement. It accounts for 1.3 to 15% of cases.
- Biomechanical factors: The shoulder gets elevated when the scapula rotates upward, externally and posteriorly after 90 degrees. Downward rotation of the scapula and the weight of the limb, are responsible for the initial degrees of shoulder elevation. A decreased upward rotation of the scapula with a reduced posterior tilt is seen in shoulder impingement cases. Tension overload and aging might weaken the muscles diminishing the depressor force and proximal migration of humerus, that consequently leads to impingement.
- Degenerative tendinopathy: Degenerative changes in the supraspinatus reduce its ability place the humeral head centrally on the glenoid, which pushes the humerus posteriorly, thus reducing the subacromial space and causing impingement.
- Overuse of the shoulder: Common cause seen in sportsperson involving an overhead motion. Chronic irritation, persistent strain, muscular overuse, defective mechanicsrigorous work schedule, ponderous weight lifts, and perverse work postures, cause progressive soft tissue inflammation leading to diminution of subacromial space.
- Age: Aging has been found to increase the risk of sclerosis of the medial acromion and degenerative changes in the acromioclavicular joint. As age increases, associated risk of shoulder pain incidence increases.
Signs & symptoms of Shoulder impingement syndrome
- Pain: Dull aching pain radiating to the middle part of humerus. Pain develops insidiously over days and months. Patient may complain of waking up at night due to shoulder pain, which is aggravated when sleeping on the side of the affected arm or sleeping with hands placed over the head. Resolute and progressive pain debilitates patient making daily functional life difficult and exigent. An important clinical finding is the painful arch throughshoulder abduction.
- Diminished strength in the affected arm: Patient experiences difficulty in forward flexion of arm, abduction of shoulders and external rotation of the arm.
Diagonsis of Shoulder impingement syndrome
- Neer’s test: The examiner stands behind the patient pinning down the acromion and collar bone preventing the elevation of scapula and passively elevates his/her affected arm in forward flexion, which pushes the tuberosity of humerus below the acromion, compressing the supraspinatus tendon in between the two bones. This maneuver replicates the pain which is recorded accordingly. Another method to elicit pain is by rotating the muscle internally thus maximizing contact pressure. A shot of local anesthetic is injected just below the anterior part of the acromion. If the pain subsides, it indicates pain of impingement syndrome. To demonstrate the characteristics painful arc, the patient is placed in a standing position and instructed to elevate and depress the arm actively in abduction. If the patient experiences pain on moving the arm at either 70 degrees or 120 degrees upwards or downwards, then the test is considered to be positive for impingement syndrome. Neer’s test has a sensitivity rate of 75 to 89%.
- Hawkins–Kennedy test: In this test, the examiner elevates the patients’ arm at 90 degrees in forward flexion, rotated internally and then placed down. This act rotates the humerus against the coracoacromial ligament eliciting supraspinatus impingement. Reproduction of pain is recoreded. This test has a sensitivity rate of 92%.
- Yocum’s test: As the patient touches his/her shoulder by the contralateral hand, the examiner elevates the only the elbow. Impingement of supraspinatus elicits pain.
- Cross-body adduction: The patient is asked to flex the affected arm in a forward direction at 90 degrees and then touch the contralateral shoulder. Compression of acromioclavicular joint invokes pain.
- Jobe’s test or the empty can test: The patient lifts his/her affected arm superiorly with fully extended elbows and then make a full internal rotation in the scapular plane. Simultaneously the examiner depresses the upper arm. Positive test elicits pain during resistance.
- Codman’s sign or the drop arm test:Patient is asked to abduct both arms maximally and then slowly reverse the action along the same arc of motion. If the affected arm drops suddenly with a jerk, it indicates a positive test. This test has a specificity rate of 97%.
- Infraspinatus drop sign: The patient is placed in a seated position while the examiner elevates his/her affected arm at 90 degrees in scapular plane. The elbow is bent at 90 degrees while the arm is in external rotation. In case of impingement the patient is not able to hold this position.
- External rotation lag sign:The patient is asked to flex the elbow at 90 degrees, while the examiner elevates his/her affected arm at 20 degrees to the scapular plane. Later on, the examiner releases the wrist but still continues to elevate the elbow. In case of a positive test the patient is unable to hold the position and the wrist drops.
- Radiology: Radiographs are needed to confirm the diagnosis of shoulder impingement syndrome and to assess the extent of osseous abnormalities. An outlet view if preferred to analyze the acromion configuration. An acromiohumeral distance reduced to 6-7mm demonstrates a rotator cuff tear.
- Magnetic resonance imaging (MRI): It is used to evaluate the condition of soft tissues, classify the retraction rate of tendon, to evaluate the extent of muscle atrophy and fatty tissue infiltration. Sensitivity rate of MRI is 92% and specificity rate of 93%.
- Ultrasonography: Inflammation of the bursa seen as an anechoic effusion and tendon ruptures can be viewed in standardtomographic planes via a 5–12 MHz linear transducer.
- Computed tomography (CT): It can be used as a supplemental method to evaluate bony changes.
Types of Shoulder impingement
- Primary impingement: It occurs due to direct entrapment of rotator cuff muscles in between the head of the humerus and the soft tissues of acromioclavicular joint.
- Secondary impingement: Impairment of the capsular ligaments which are the static stabilizers of the shoulder joint due to hyperactivity makes the joint rickety. This enhances the range of motion of the humerus head beyond normal, thus encroaching the rotator cuff muscles.
- Internal or undersurface impingement: When the affected arm is placed at 90 degrees in abduction and 90 or more degrees in external rotation, the rotator cuff muscles get impinged by the adjoining posterior surface of the glenoid rim, thus eliciting pain in posterior part of the shoulder. It is also termed as ‘thrower’s shoulder’ because it is frequently seen in overhead-throwing athletes like baseball pitchers and javelin throwers.These anatomic modifications consequently result in Glenohumeral internal rotation deficit (GIRD) that increases the risk of developing internal impingement.
- External impingement: Occurs by compression of the acromion by external factors leading to subacromial bursitis and other injuries on the bursal side of the rotator cuff.
Stages of Shoulder impingement
- Edema and hemorrhage: It is the resultant effect of persistent irritation caused by disoriented hyperactivity of the rotator cuff, usually seen in sportsperson and by occupational overuse of rotator cuff above the shoulders.
- Fibrosis and tendonitis: As a sequel of constant irritation, inflammatory changes occur in the rotator cuff tendons termed as tendonitis. Progressive inflammatory insult causes the bursa to become fibrotic and rigid. At this stage, activities involving raising the arms above shoulder level become difficult to perform.
- Rotator cuff tears and bone abnormalities: Constant impingement of the rotator cuff tendons by the traumatic shoulder movements lead to partial or complete tear. The acromion and humeral tuberosity by also show traumatic abnormalities.
Treatment procedures for Shoulder impingement syndrome
- Non-operative treatment: Rest and analgesics, stretching and guided exercises, cold or ice treatment, thermotherapy, acupuncture, transcutaneous nerve stimulation (TENS), kinesio taping and shoulder bracing.
- Operative or surgical treatment: Surgical intervention is indicated in patients with persistent pain which is not relieved by the non-operative methods.
o Subacromial decompression: This form of treatment modality involvesacromioplasty i.e. reshaping the acromion simulating type 1 morphology by decompressing the rotator cuff. The subacromial space is consequently increased that diminishes the irritation on rotator cuff. Additionally, osteophytes are removed from the coracoacromial arch and acromioclavicular joint. This surgical procedure was introduced by Ellman in 1985 and termed as Arthroscopic acromioplasty.In the classical approach, the acromial part of the deltoid muscle is disengaged, while the mini-open approachinvolves detaching the deltoid fibers and preserving the attachment of the deltoid to the bone. Advantages of this technique are that it provides a better appreciable view of the undersurface of the arch assisting in adequate removal of osteophytes and better detection of arch abrasion.
o Bursectomy: It involves removal of the part of bursa affected by the inflammatory processes. It can be performed with or without additional acromioplasty.
o Coplaning: In this technique, the osteophytes are removed from the inferior part of the acromion and the lateral part of the clavicle, preserving the acromioclavicular joint. This procedure is contentious hence it’s advised that in case of patients with painful arthritic changes of the acromioclavicular joint,an open or arthroscopic manipulation should be used, involving the resection of 3–4 mm of the acromion and the clavicle. The coracoclavicular ligaments maintain the stability of the clavicle.
Risk factors associated with Shoulder impingement syndrome
- Gender: Reports have shown a female preponderance in cases of shoulder pain. Health surveys have reported a lifetime prevalence of 51% in women in contrast to 43% in men. 23% of women exhibited decreased frequency of shoulder in the preceding years as compared to 18% of men.
- Hand dominance: Shoulder impingement syndrome often affects the patients’ dominant arm. If one arm is affected it increases the risk for the other arm to develop the same condition. Health reports have documented a two-fold difference in the right and left arm affected patients of the working age group, indicating an association of the syndrome and physical activities.
- Obesity: Effect of obesity is controversial. Some reports have documented an increased risk of rotator cuff tendinitis in obese patients.
Complications associated with Shoulder impingement syndrome
- Technical errors: Improper orientation and inaccurate acromion resection can weaken the deltoid attachment and injure the acromioclavicular joint
- Incorrect indication: such as persistent untreated cases of the acromioclavicularjoint or the biceps tendon
- Adhesive capsulitis: is the rigidity of shoulder and is quite rare
- Infection: a rare complication. Accounts for under 0.5% of complications
Am I a Good Candidate for surgical treatment of Shoulder impingement syndrome?
If the patient is experiencing constant, progressive pain in the shoulder with functional loss of motion in the arm, find it arduous to perform activities involving elevating the arm above shoulder, and wake up in the middle of the night with excruciating shoulder pain, are best suited for surgical intervention. Young patients who require restoring of high functional needs should undergo surgical correction. All traumatic ruptures are strongly indicated for surgical manipulation.
Recovery time and aftercare
Patient might be discharged on the intraoperative day depending on the type of surgery. A shoulder immobilizer sling is used to hold the operative arm and to assist in repair of trapezius, which is to be worn for approximately a month or as directed by the surgeon. Patient is instructed to follow a graduated strengthening program for at least twelve weeks. He/she can resume activity thereafter.
Success Rate of Shoulder impingement syndrome treatment
The satisfaction rate observed in patients who underwentacromioplasty was reported to be 88%. Studies have also documented that 77% of patients experienced minimal or no pain following the procedure. Patient satisfaction was sustained for at least six years following arthroscopic acromioplasty. 79-84% of the patients have reported satisfied results maintained for up to 20 years.
Benefits of Shoulder impingement syndrome treatment:
- Appreciable improvement in functional life
- Significant enhancement in quality life
- Reduced risk of disability
Cost of shoulder surgical interventions varies depending on the stage of shoulder impingement, type of surgical approach, rehabilitation following surgery, quality of functional life to be maintained and associated medical conditions. On an average subacromial decompression might cost $1657 and rotator cuff repairs approximately$3388.
Why Choose MedcureIndia?
Shoulder impingement correction requires a multidisciplinary approach involving physicians, surgeons and physiotherapists. We at MedcureIndia have an elite consortium of professionals working round the clock and provide cost effective operative care and rehabilitative assistance. We follow standard protocol for diagnosis and postoperative follow-up.