Study Design Controlled laboratory study. Objectives To examine the effects of altering posture on the subacromial space (SAS) in subjects with rotator cuff disease and subjects without shoulder pain. Background Poor upper quadrant posture has been linked to altered scapular mechanics, which has been theorized to excessively reduce SAS. However, no study has examined the direct effects of altering upper quadrant posture on SAS. We hypothesized that upright posture would increase and slouched posture would decrease the SAS, as compared to a normal posture, when measured both with the shoulder at rest along the side of the trunk and when maintained in 45° of active shoulder abduction. Methods Participants included 2 groups: the subjects with shoulder pain and rotator cuff disease, as diagnosed via magnetic resonance imaging (n = 31), and control subjects without shoulder pain (n = 29). The SAS was imaged with ultrasound using a 7.5-MHz linear transducer placed in the coronal plane over the posterior to midportion of the acromion. The SAS was measured on ultrasound images using the acromiohumeral distance (AHD), defined as the shortest distance between the acromion and the humerus. The AHD was measured in 2 trials at 2 arm angles (at rest along the trunk and at 45° of active abduction) and across 3 postures (normal, slouched, and upright), and averaged for data analysis. Results Two mixed-model analyses of variance, 1 for each arm angle, were used to compare AHD across postures and between groups. There was no interaction between group and posture, and no significant main effect of group for either arm position. There was no significant main effect of posture for the arm at rest (P = .26); however, there was a significant main effect of posture on AHD at the 45° abduction arm angle (P = .0002), with a significantly greater AHD in upright posture (mean AHD, 9.8 mm), as compared to normal posture (mean AHD, 8.6 mm). Conclusion The effect of posture on SAS, as measured by the 2-dimensional AHD using ultrasound of the posterior to middle aspect of the SAS, is small. The AHD increased with upright posture by 1.2 mm compared to normal posture, when the arm was in 45° active abduction. J Orthop Sports Phys Ther2010;40(10):633–640. doi:10.2519/jospt.2010.3155

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In this work, a modified Newton–[Formula: see text]zban composition of convergence order six for solving nonlinear systems is presented. The first two steps of proposed scheme are based on third-order method given by [Formula: see text]zban [[Formula: see text]zban, A. Y. [2004] “Some new variants of Newton’s method,” Appl. Math. Lett. 17, 677–682.] for solving scalar equations. Computational efficiency of the presented method is discussed and compared with well-known existing methods. Numerical examples are studied to demonstrate the accuracy of the proposed method. The basins of attraction of some of the existing methods along with the proposed method are given to exhibit their performance.

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