Snapping Scapula Syndrome

Toronto Blue Jays third baseman Addison Barger throws to first to put out Boston Red Sox second baseman Vaughn Grissom (not pictured) during the sixth inning at Rogers Centre. Mandatory Credit: John E. Sokolowski-Imagn Images

Have you ever had a patient complain of pain or clicking around the scapula?  These symptoms may be due to snapping scapula syndrome (SSS). It is a rare condition caused by disrupting the usual smooth articulation between the anterior scapula and posterior chest wall⁽¹⁾. This condition is also called ‘Washboard Syndrome’ due to the crepitation/snapping-like sound that patients experience during movements of the scapulothoracic joint⁽²⁾.

Epidemiology

The prevalence of SSS is not well-established in the general population and is very uncommon in comparison to other shoulder pathologies. It is more commonly seen in athletes who participate in sports requiring repetitive overhead movement, e.g., swimmers and weightlifters⁽³⁾. Furthermore, SSS may be more common in males due to higher rates of involvement in sports and overhead manual labor.

Anatomy

The scapula is a triangular-shaped bone between the second and seventh ribs and articulates with the posterior thorax⁽³⁾. It has three angles – superior, inferior, and lateral, and three borders – superior, medial, and lateral. The scapula is connected to the axial skeleton by only the acromioclavicular joint, and therefore, stability is provided by surrounding musculature^(2,3). The articulation between the scapula and the rib cage is incongruous as it does not have any true joint structures^(2,3).

The periscapular muscles provide stability to facilitate scapulothoracic articulation. Three layers of muscles surround the scapulothoracic joint – superficial (trapezius and latissimus dorsi), intermediate (rhomboid major, rhomboid minor, and levator scapulae), and deep (serratus anterior and subscapularis)⁽⁴⁾.

Therapists need to understand the neurovascular anatomy as trauma to these structures may have a direct/indirect effect on scapular movement mechanics and the overall patient presentation^(3,5). The accessory nerve moves through the levator scapulae, close to the superomedial angle of the scapula, and proceeds along the medial scapular border under the trapezius. The transverse cervical artery splits into the dorsal scapular artery (deep branch) and a superficial branch that follows the accessory nerve. The dorsal scapular artery runs alongside the dorsal scapular nerve just medial to the medial scapular border, penetrating the scalenus medius, running beneath, and innervating the rhomboid major and minor. The long thoracic nerve is located on the surface of the serratus anterior. The suprascapular nerve and artery head toward the suprascapular notch on the upper border of the scapula, medial to the base of the coracoid process.

Furthermore, there are several bursae that are potentially involved in SSS (see figure 1)⁽⁶⁾. Adventitial/minor bursae may develop due to abnormal scapulothoracic articulation(6). The bursa located at the superomedial angle is the most common source of symptoms, and the bursa at the inferior angle is the second most common⁽⁵⁾.