In vivo evaluation of rotator cuff internal impingement during scapular plane abduction in asymptomatic individuals

• Published in: Journal of orthopaedic research 2023-04, Vol.41 (4), p.718-726
• Main Authors: Lawrence, Rebekah L., Soliman, Steven B., Roseni, Kevin, Zauel, Roger, Bey, Michael J.
• Format: Article
• Language: English
• Subjects: Biomechanical Phenomena; Humans; internal impingement; kinematics; Range of Motion, Articular; Rotation; Rotator Cuff; Rotator Cuff Injuries; Scapula; Shoulder Impingement Syndrome; Shoulder Joint
• ISSN: 0736-0266; 1554-527X; 1554-527X
• DOI: 10.1002/jor.25423

Internal impingement—or entrapment of the undersurface of the rotator cuff tendon against the glenoid during overhead activities—is believed to contribute to articular‐sided tears. However, little is known about internal impingement outside athletic populations. Therefore, the objectives of this study were to (1) describe glenoid‐to‐footprint distances and proximity centers during dynamic, in vivo motion in asymptomatic individuals, and (2) determine the extent to which these measures differed between individuals with and without a rotator cuff tear. Shoulder kinematics were assessed in 37 asymptomatic individuals during scapular plane abduction using a high‐speed biplane radiographic system. Glenoid‐to‐footprint distances and proximity center locations were calculated by combining the kinematics with computerized tomography‐derived bone models. Glenoid‐to‐footprint contact was presumed to occur when the minimum distance was less than the estimated labral thickness. The condition of the supraspinatus tendon (intact, torn) was assessed using ultrasound. Minimum distances and proximity centers were compared over humerothoracic elevation angles (90°, 110°, 130°, 150°) and between supraspinatus pathology groups using two‐factor mixed model analysis of variances. Glenoid‐to‐footprint minimum distances decreased consistently across elevation angles (p