Snapping Scapula Syndrome
An uncommon cause of shoulder pain, snapping scapula syndrome, which is also known as jumped shoulder blade, occurs when there is dysfunction of the normal smooth sliding of the concave anterior scapula over the convex posterior thorax.
When this abnormal scapulothoracic motion occurs, a snapping, cracking, grating, or thumping sound in the region of the superomedial border of the scapula occurs.
These sounds can be quite distressing to the patient and those in proximity, as they can be very loud, as the sounds are amplified by the patient’s air-containing thorax.
While there are numerous causes of snapping scapula syndrome, the etiopathology of snapping scapula syndrome can be divided into five major categories: (1) scapulothoracic bursitis; (2) muscular abnormalities; (3) soft issue abnormalities; (4) bony abnormalities; and (5) idiopathic
Causes of Snapping Scapula Syndrome
|Scapular BursitisOveruse injury• Reactive bursitis of the infraserratus bursa• Reactive bursitis of the supraserratus bursa• Reactive bursitis of the scaphotrapezial bursaChronic Bursitis• Scarring of bursae and periscapular musculature• Fibrosis• Impingement• Pain• Snapping soundMuscular Abnormalities• Congenital muscle abnormalities• Abnormal muscle insertions• Periscapular muscle avulsions• Muscular injury• Muscular weakness• Muscle atrophy• Post-inflammatory muscular fibrosis• Post-traumatic muscular fibrosisSoft Tissue Lesions• Elastoma dorsi• Lipomas• Glomus tumors• Chondrosarcomas• OsteochondromasBony Abnormalities• Scapular anatomic variations• Winged scapula• Pseudo-winged scapula• Scapular fractures• Hypertrophic callus formation• Displacement of fracture• Malunion of healing fracture• Abnormal Luschka tubercle• Fractured posterior ribs• Hypertrophic callus formation• Displacement of fracture• Malunion of healing fracture• Osteophyte formation• Excessive thoracic kyphosis• Scoliosis• Joint hypermobility syndrome• Glenohumeral joint dysfunction• Idiopathic|
What are the Symptoms of Snapping Scapula Syndrome
The onset of snapping scapular syndrome may be acute or chronic depending on the etiopathology of the syndrome.
Common acute inciting factors are overhead activities such as painting a ceiling, overhand throwing, swimming, repetitive overuse of the shoulder (e.g., raking leaves, pushups), and scapulothoracic trauma.
However, regardless of the cause, it is invariably the abnormal sound on shoulder movement rather than the associated pain that prompts the patient to seek medical attention.
Descriptions of sounds associated with snapping scapula syndrome include snapping, cracking, grating, thumping, clinking, crunching, and popping. These sounds can be quite loud, as they are amplified by the air-filled thorax. The intensity of the pain associated with snapping scapula syndrome ranges from irritating to excruciating.
On physical examination, crepitus, and at times a grating sensation, can be appreciated on palpation as the scapula is moved anteriorly. This sensation can be magnified if the examiner exerts firm pressure to the superior angle of the scapula during movement.
Tenderness to palpation, most commonly at the superomedial border and inferior pole of the scapula, is present. Pain and scapular snapping are often reproduced by moving the affected extremity into the abducted position and then having the patient abduct the affected shoulder and then fully externally rotate the affected extremity with the thumb in a hitchhiking position.
This maneuver is known as the armed arm test and the test is positive if the maneuver reproduces the patient’s pain and elicits an audible snapping sound.
Pain and scapular snapping can be reduced by having the patient cup the hand of the affected extremity over the contralateral shoulder. This maneuver effectively lifts the affected scapula away from the underlying thorax. If there is significant bursitis and associated edema, pseudo-winging of the scapula may be present and compression of the scapula may produce a boggy sensation. If there is neural compromise, true winging of the scapula may be present.
How is Snapping Scapula Syndrome diagnosed?
Electromyography may help identify neural compromise (e.g., damage to the long thoracic nerve of Bell), although the test may be normal in mild cases even though significant neurapraxia is present.
Plain radiographs of the scapula, posterior ribs, and shoulder are indicated in all patients who present with snapping scapula syndrome to rule out fractures and occult bony pathological processes. Based on the patient’s clinical presentation, additional testing, including complete blood cell count, uric acid level, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated.
MRI and ultrasound imaging of the shoulder and scapula is indicated in all patients thought to have snapping scapula syndrome, given the large range of pathological processes responsible for this uncommon cause of shoulder pain. Computerized tomography (CT) may also help identify bony abnormalities responsible for the patient’s symptomatology.
Snapping syndrome is often initially misdiagnosed as bursitis, tendinitis, or arthritis of the shoulder. Parsonage-Turner syndrome, or idiopathic brachial neuritis, also may manifest as sudden onset of shoulder pain and can confuse the clinical picture.
Tumor involving this anatomical region also should always be considered in the differential diagnosis of snapping scapula syndrome, as should occult fractures of the scapula and other mass lesions such as large bursa, cysts, and lipomas.
Nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors represent a reasonable first step in the treatment of mild, self-limited snapping scapula syndrome.
The use of tricyclic antidepressants, such as nortriptyline, at a single bedtime dose of 25 mg, titrating upward as side effects allow, also is useful, especially if sleep disturbance is present.
Avoidance of repetitive trauma thought to be contributing to this uncommon pain syndrome also is important, especially in professional athletes. If these maneuvers fail to produce rapid symptomatic relief, local injection of the superomedial and inferior pole of the affected scapula and any inflamed bursae with local anesthetic and steroid is a reasonable next step For persistent cases, arthroscopic debridement of the anterior scapula may be indicated.
Failure to diagnose snapping scapula syndrome correctly puts the patient at risk for the missed diagnosis of other syndromes that may result in ongoing damage to the shoulder or lead to overlooked pathological processes in this anatomical region that may harm the patient, such as primary or metastatic tumors of the shoulder, posterior chest wall, and scapula.
MRI and ultrasound imaging are indicated in all patients thought to have snapping scapula, and aggressive treatment of surgically correctable causes is generally indicated sooner rather than later to avoid ongoing irreversible shoulder damage.
Avoidance techniques of the repetitive movements responsible for snapping scapula syndrome often are forgotten in the rush to treatment. Mild cases of snapping scapula syndrome are usually self-limited, but more severe cases may require injection with local anesthetic and steroid.
Occasionally, surgical intervention is indicated. As with other uncommon pain syndromes, snapping scapula syndrome should be considered a diagnosis of exclusion and the clinician should ensure that no potentially harmful occult space-occupying lesions are present before attributing symptoms to other benign causes.