Abstract
BackgroundNo clear trend has emerged from the literature regarding three-dimensional (3D) translations of the humerus relative to the scapula in shoulders with rotator cuff tears (RCTs). The purpose of this study was to evaluate the kinematics of RCT shoulders using 3D-to-two-dimensional (2D) model-to-image registration techniques.MethodsDynamic glenohumeral kinematics during scapular plane abduction and axial rotation were analyzed in 11 RCT patients and 10 healthy control subjects. We measured the 3D kinematic parameters of glenohumeral joints using X-ray images and CT-derived digitally reconstructed radiographs.ResultsFor scapular plane abduction, the humeral head center was positioned significantly more medially in shoulders with RCTs than in controls at 135° of humeral abduction (p = 0.02; RCTs versus controls: − 0.9 ± 1.6 versus 0.3 ± 1.3 mm). There was no significant difference in the superior/inferior translation of the humeral head center (p = 0.99). For axial rotation in adducted position, the humeral head center was positioned significantly more anteriorly in shoulders with RCTs than in controls at − 30° of glenohumeral external rotation (p < 0.0001; RCTs versus controls: 3.0 ± 1.7 versus 0.3 ± 1.5 mm).ConclusionsThis study revealed the kinematics of shoulders with large to massive full-thickness RCTs: the humeral head center showed a medial shift at the late phase of scapular plane full abduction, and an anterior shift at the internal rotation position during full axial rotation. The kinematic data in this study, which describe the patterns of movement of shoulders with large to massive full-thickness RCTs, provide valuable information for future studies investigating glenohumeral translations in other pathological conditions of the shoulder. For clinical relevance, quantitative assessment of the dynamic kinematics of shoulders with RCTs might be a therapeutic indicator for achieving functional restoration.
Highlights
No clear trend has emerged from the literature regarding three-dimensional (3D) translations of the humerus relative to the scapula in shoulders with rotator cuff tears (RCTs)
Scapular plane full abduction The S/I translation of the humeral head center did not significantly differ between the RCT and control groups (p = 0.99), even though the humeral head center was positioned slightly superiorly in shoulders with RCTs compared to controls at 15°, 30°, 45°, 60°, 75°, 90°, 135°, and 150° of humeral abduction (Fig. 3a)
Full axial rotation in adducted position The S/I translation of the humeral head center did not significantly differ between the RCT and control groups (p = 0.63), even though the humeral head center was positioned slightly inferiorly in shoulders with RCTs compared to controls at − 30°, 20°, 30°, and 40° of glenohumeral external rotation (Fig. 3d)
Summary
No clear trend has emerged from the literature regarding three-dimensional (3D) translations of the humerus relative to the scapula in shoulders with rotator cuff tears (RCTs). The purpose of this study was to evaluate the kinematics of RCT shoulders using 3D-to-two-dimensional (2D) model-to-image registration techniques. Rotator cuff tears (RCTs) are a common shoulder disorder among elderly people and can cause shoulder pain, weakness, and decreased range of motion [1]. The accurate evaluation of kinematics under weightbearing conditions has been achieved using 3D-to-two-dimensional (2D) model-to-image registration techniques [7,8,9,10,11,12,13]. With regard to the shoulder joint, several studies have recently reported shoulder kinematics using 3D-to2D model-to-image registration techniques [14,15,16,17,18,19,20]. Our previous study demonstrated the in vivo kinematics of healthy shoulder joints with coordinated humeral and scapular dynamic movements [17]
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