Bubble Sign: An Arthroscopic Technical Trick to Differentiate Between Partial- and Full-Thickness Rotator Cuff Tears

Abstract

Distinguishing between partial-thickness and small focal full-thickness tears of rotator cuff may be important for determining the appropriate surgical treatment options and repair constructs in the care of patients with rotator cuff pathology. This article presents a simple intraoperative technical trick to aid in identification of small full-thickness tears of the superior rotator cuff. The relatively higher-pressured subacromial space and the low-pressured glenohumeral joint are separated by the supraspinatus tendon. When this barrier is compromised due to a full-thickness tear, free fluid flows from high to low pressure down the native pressure gradient. This is seen as the movement of air bubbles into the glenohumeral joint from the subacromial space and can be used to identify the presence of a full-thickness rotator cuff tear on diagnostic arthroscopy.

Fig 1

(A) This diagram demonstrates the native shoulder joint. The high-pressured subacromial space (red mark) has a pressure range around 8-17.5 mm Hg at 0° of abduction. The glenohumeral joint (green mark) has a much lower pressure of around –4 mm Hg. As seen in the diagram, an intact rotator cuff separates these 2 areas of high and low pressure, hence creating a native pressure gradient. (B) When a full-thickness tear occurs in the superior rotator cuff, there is now a conduit that connects the high- and low-pressure areas, causing a loss of the native pressure gradient. This results in movement of air from the subacromial space (the high-pressure area; red) to the glenohumeral joint (the low-pressure area; green), which we call the "bubble sign.”

Fig 2

(A) The patient is placed in the beach-chair position, and the right upper extremity is prepped and draped in the normal sterile fashion. The operative shoulder is placed in neutral rotation and slight flexion, and this position is held by a commercially available arm positioning device (Spyder; Smith & Nephew). (B) The coracoid, anterior portal (AP), anterolateral portal (ALP), posterolateral portal (PLP), and posterior portal (PP) are carefully marked.

Fig 3

(A) An intra-articular diagnostic arthroscopy of a patient in the beach-chair position showing the right glenohumeral joint from the posterior viewing portal. The humeral head, supraspinatus tendon (labeled), and long head of the biceps tendon (labeled) are in view. (B) As the supraspinatus tendon is raised by the blunt trocar, air bubbles (the “bubble sign”; black arrow) can be seen entering from the subacromial space (not visualized) into the field of the glenohumeral joint.