Three-dimensional scapular kinematics during open and closed kinetic chain movements in asymptomatic and symptomatic subjects

The combination of open kinetic chain (OKC) and closed kinetic chain (CKC) exercises is commonly recommended in shoulder rehabilitation, aiming at improving strength and sport-specific performance. This study aimed to investigate the three-dimensional (3-D) scapular kinematics and bilateral symmetry of scapular motion during dynamic OKC and CKC movements in asymptomatic and symptomatic shoulders. Fifty subjects with unilateral shoulder pain (symptomatic subjects diagnosed with subacromial impingement syndrome, n=20) or without shoulder pain during active shoulder elevation (asymptomatic subjects, n=30) participated in the study. Furthermore, 3-D scapular kinematics were recorded using an electromagnetic tracking device in the sagittal plane of shoulder elevation for both the OKC and CKC conditions performed with slings. Data for scapular kinematics and symmetry angle (SA) were analyzed at 30°, 45°, 60°, 90°, and 120° of humerothoracic elevation. Analysis of variance models and Student׳s t-test were used to make comparisons between conditions. In general, the scapula was more externally rotated, upwardly rotated and anteriorly tilted for asymptomatic shoulders, and more upwardly rotated for symptomatic shoulders during CKC shoulder elevation. Further, comparisons of SA obtained during OKC and CKC movements revealed that during CKC, scapular motion was more symmetrical for upward-downward rotation and anterior-posterior tilt in asymptomatic shoulders and for anterior-posterior tilt in symptomatic shoulders, especially above 90° humerothoracic elevation. Differences in scapular motion during the CKC condition were in a specific pattern and enhanced symmetry, which would be considered to be a position less likely to produce compression of the rotator cuff tendons for both training in asymptomatic populations and for treatment in early rehabilitation of patients, such as those who have shoulder impingement syndrome.