Kazuya Madokoro

Effects of sex differences on scapular motion during arm elevation

Introduction: Scapular motion during arm elevation is frequently evaluated in patients with shoulder disorders because it provides clinically useful information. With the development of measurement devices and improvement in accuracy, comparisons under various conditions have recently been reported. However, in most of these reports, the subjects examined were limited to males, or a mixed population of males and females. Only a few reports have described sex differences. In the current study, we performed three-dimensional dynamic analysis of arm elevation and investigated whether there is a sex difference in scapular motion. Methods: Subjects included 18 healthy adult males (18 shoulders) and 19 healthy adult females (19 shoulders). Thirty-seven shoulders were on the dominant side. The age range was 20.5 ± 0.03 years. Subjects performed scapular plane arm elevation, and kinematic data were recorded using an electromagnetic tracking device. Scapular upward rotation and internal rotation angles and the posterior tilt angle accompanying arm elevation were calculated from recorded data. Changes in each angle during scapular motion were recorded according to sex. Results: There were sex differences in scapular upward rotation and internal rotation angles. The upward rotation angle was significantly greater in males, whereas the internal rotation angle was significantly greater in females. No sex differences were noted in the scapular posterior tilt angle. Discussion: Findings of this study may serve as basic data for scapular motion during scapular plane elevation in healthy males and females. In addition, it is necessary to evaluate and treat the shoulder while taking sex differences in scapular movement into consideration.

Cut-off values of the Japanese Orthopaedic Association score corresponding to Constant scores for evaluating outcomes in rotator cuff tear:

Purpose: To clarify the cut-off value of the Japanese Orthopaedic Association (JOA) score corresponding to rotator cuff tear outcome as evaluated by the Constant score. Methods: The subjects were 230 patients with rotator cuff tear. The Constant and JOA scores on the first examination in our hospital were evaluated. After investigation of the correlation between the Constant and JOA scores, the cut-off JOA score was calculated, corresponding to excellent, good and fair outcomes as evaluated by the Constant score. Results: The Constant and JOA scores on the first examination were 49.64 ± 12.84 and 72.52 ± 12.84, respectively, with a strong correlation (r = 0.87, p < 0.01). Receiver operating characteristic analysis revealed that the cut-off JOA score was 87.0 for excellent outcome (area under the curve, AUC: 0.93; sensitivity: 100%; specificity: 88.6%; p < 0.01), 84.0 for good outcome (AUC: 0.94; sensitivity: 100%; specificity: 83.4%; p < 0.01) and 78.0 for fair outcome (AUC: 0.88; sensitivity: 100%; specificity: 71.3%; p < 0.01). Conclusions: In patients with rotator cuff tear, good outcome as judged by a Constant score of ≥80 corresponds to a JOA score cut-off of 84.0. Judgement of the treatment outcomes and evaluation of the surgical method may be more accurate when using clear cut-off values for the scoring system employed, such as those determined in our study.

Analysis of scapular kinematics during active and passive arm elevation

[Purpose] Early postoperative passive motion exercise after arthroscopic rotator cuff repair remains controversial. To better understand this issue, this study was aimed at evaluating scapular kinematics and muscle activities during passive arm elevation in healthy subjects. [Subjects and Methods] The dominant shoulders of 27 healthy subjects were examined. Electromagnetic sensors attached to the scapula, thorax, and humerus were used to determine three-dimensional scapular kinematics during active arm elevation with or without external loads and passive arm elevation. Simultaneously, the activities of seven shoulder muscles were recorded with surface and intramuscular fine-wire electrodes. [Results] Compared with active arm elevation, passive elevation between 30° and 100° significantly decreased the scapular upward rotation and increased the glenohumeral elevation angle. However, no significant differences in scapular posterior tilt and external rotation were observed between active and passive arm elevation, and scapular plane kinematics were not affected by muscle activity. [Conclusion] Unlike active motion with or without an external load, passive arm elevation significantly decreased the scapular upward rotation and significantly increased the mid-range glenohumeral elevation. These data, which suggest that passive arm elevation should be avoided during the early postoperative period, may expand the understanding of rehabilitation after arthroscopic rotator cuff repair.

Electromyographic study of rotator cuff muscle activity during full and empty can tests

The empty can (EC) and full can (FC) tests are used as diagnostic tools for patients with rotator cuff disease. However, recently concerns have been raised that these tests do not selectively activate the muscle. Therefore, the purpose of this study was to evaluate the rotator cuff muscle activation levels during the EC and FC tests in various positions using electromyography. Twelve healthy, right-handed men without shoulder complaints (mean age: 26.1 years, range: 23–35 years) were included. The tests were performed isometrically with the shoulder elevated at 45° and 90° in the sagittal, scapular, and coronal planes, either in the thumb-up (FC test) or thumb-down (EC test) positions. During these positions, the electromyographic signal was recorded simultaneously from the four shoulder muscles using a combination of surface and intramuscular fine-wire electrodes. The average activation of the supraspinatus and subscapularis was greater during the EC test than during the FC test and in the scapular and coronal planes than in the sagittal plane at 90°. For the infraspinatus, there were no significant differences in any positions between the two tests. Thus, the rotator cuff muscles are influenced by arm position and the elevation plane during the EC and FC tests.