Three-dimensional comparative strain analysis of the capsuloligamentous complex during passive glenohumeral motion

Understanding the three-dimensional biomechanical behavior of the capsuloligamentous complex, considering it as a single sheet of fibrous tissue, is beneficial for assessing patients with limited glenohumeral range of motion in vivo. The aim of this study was to investigate the three-dimensional strain distribution of all capsuloligamentous regions, viewing it as a single sheet of fibrous tissue, during passive glenohumeral motion and to determine which area of the capsuloligamentous structure is essential for a particular glenohumeral motion.

Three-dimensional strain changes of the capsuloligamentous complexes of six fresh-frozen cadavers were measured using a stereoimaging technique and finite element analysis. The comparative strain of the capsuloligamentous complex was measured at 0°, 30°, 60°, and 90° of glenohumeral abduction in the scapular plane and from 60° of internal rotation to 60° of external rotation in 15° increments across four regions (i.e., posterior, superior, anterior, and inferior) and 30 subregions.

At 0° of abduction, the superior capsule affected only the range from 30° of internal rotation to 30° of external rotation. Only the anterior and posterior capsules affected more than 30° of external and internal rotations, respectively. At 30° of abduction, the posterior capsule primarily affected internal rotation, whereas the anterior capsule primarily affected external rotation. At 60° of abduction, the inferior capsule, especially the anterior subregions, significantly affected internal and external rotations. The anterior capsule affected external rotation to a lesser extent than the inferior capsule. At 90° of abduction, only the inferior capsule primarily affected internal and external rotation.

Evaluation of all capsuloligamentous regions as a single continuous sheet of fibrous tissue showed that the comparative strain of the superior and posterior capsular regions during passive glenohumeral rotation is more limited than previously known. The inferior capsular region has a more significant comparative strain during glenohumeral rotational motion than has been documented in previous studies.