- M/C cause of shoulder pain (44-65% of all shoulder complaints)
Subacromial pathology has attracted the attention of orthopaedic surgeons for a long time. In 1934, Codman described rotator cuff pathology and he was of the opinion that humeral head and acromion impingement during shoulder abduction was the cause of rotator cuff lesions and he suggested that lateral acromioplasty would resolve the patient’s symptoms.
In 1972, Dr Charles Neer coined the term impingement syndrome and he was of the opinion that impingement occurred anterolaterally at the anterior acromion and the coracoacromial ligament. He proposed anterior acromioplasty as a mode of treatment for impingement syndrome.
Impingement is classified into four types, depending on the site of soft-tissue entrapment:
- External impingement:
- Subacromial impingement syndrome (M/C)
- Internal impingement (rare):
- Subcoracoid impingement
- Posterosuperior inner impingement
- Anterosuperior inner impingement
Subacromial impingement syndrome (SAIS)(M/C)Results from inflammation, irritation, and degradation of the anatomic structures within the subacromial space. Occurs secondary to a repetitive impingement in overhead throwers or manual laborers and constitutes articular-sided rotator cuff pathology, glenohumeral internal rotation deficit (GIRD), and SLAP tears
Neer’s classification of SAIS:Stages of subacromial impingement
- Stage 1: Edema and hemorrhage, age <25 years, reversible
- Stage 2: Fibrosis and tendinitis, age 25–40 years, recurrent pain with activity
- Stage 3: Bone spurs and tendon rupture, age >40 years, progressive disability
Primary impingement:Due to structural changes that mechanically narrow the subacromial space
- Outlet impingement: Bony narrowing on the cranial side
- Non-outlet impingement: Bony malposition after a fracture of the greater tubercle, or an increase in the volume of the subacromial soft tissues – due, e.g., to subacromial bursitis or calcific tendinitis – on the caudal side
Secondary impingement:Results from functional disturbance of centering of humeral head, such as muscular imbalance, leading to an abnormal displacement of the center of rotation in elevation and thereby to soft tissue entrapment
Bigliani and Morrison acromion classification:Acromion shape plays a role in the development of external, or “outlet-based” impingement syndrome.
- Class I: flat acromion
- Class II: curved acromion
- Class III: hooked acromion
- Persistent shoulder pain without any known preceding trauma
- Pain on elevating the arm, on forced movement above the head, and when lying on the affected side.
History-taking and a thorough physical examination are the basis of the diagnostic assessment.
- Special tests to evaluate for shoulder instability (classically, these tests are negative in shoulder impingement syndrome):
- Sulcus sign: With the patient sitting upright with arm resting at their side, the clinician stabilizes the shoulder proximally and applies an inferiorly-directed force at the elbow. A positive test is noted based on the inferior displacement of the humeral head.
- Anterior apprehension test: With the patient lying supine, this test is performed by placing the patient’s shoulder in 90° abduction and 90° external rotation. While supporting the proximal shoulder, the clinician then applies greater gentle external rotation movement. The exam is considered positive when the patient reports a subjective feeling of impending subluxation or near dislocation
- Relocation test: This test requires a positive anterior apprehension test. After the patient reports the prodrome of dislocation or subluxation described above, the clinician applies a posteriorly directed force on the anterior humeral head, which relieves the patient’s symptoms.
Conservative management:In the absence of major structural damage, conservative multimodal treatment for 3–6 months is the initial therapy of choice. The treatment mainly addresses pain at first, then passive and active motion, and lastly strength and coordination.
- Nonsteroidal anti-inflammatory drugs (NSAID)
- Cortisone injections
- Physical therapy
Surgical management:Indicated only if the symptoms, physical examination, and imaging findings are concordant. It is contraindicated if no structural abnormality is suspected.
- Subacromial decompression: Removal of anterior and lateral portions of the undersurface of the acromion (5–8 mm) and detachment of the coraco-acromial ligament
- Bursectomy: As the bursa is usually affected by inflammatory changes, this tissue is removed
- Coplaning: Removal of inferior acromial osteophytes and of the lateral end of the clavicle without total resection of the acromioclavicular (AC) joint.