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Background: The concept of dynamic anterior shoulder stabilization (DAS) combines a Bankart repair with the additional sling effect of the long head of the biceps (LHB) tendon to treat anterior glenohumeral instability. This surgi...
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Background: The concept of dynamic anterior shoulder stabilization (DAS) combines a Bankart repair with the additional sling effect of the long head of the biceps (LHB) tendon to treat anterior glenohumeral instability. This surgical technique was created to close the gap between the indications for isolated Bankart repair and those requiring bone transfer techniques. Purpose: To biomechanically investigate the stabilizing effects of the DAS technique in comparison with the standard Bankart repair in different defect models. Study Design: Controlled laboratory study. Methods: Twenty-four fresh-frozen cadaveric shoulders (mean +/- SD age, 60.1 +/- 8.6 years) were mounted in a 6 degrees of freedom shoulder testing system. With cross-sectional area ratios, the rotator cuff muscles and LHB tendon were loaded with 40 N and 10 N, respectively. Anterior and inferior glenohumeral translation was tested in 60 degrees of abduction and 60 degrees of external rotation (ABER position) while forces of 20 N, 30 N, and 40 N were applied to the scapula in the posterior direction. Total translation and relative translation in relation to the native starting position were measured with a 3-dimensional digitizer. Maximal external rotation and internal rotation after application of 1.5-N center dot m torque to the humerus were measured. All specimens went through 4 conditions (intact, defect, isolated Bankart repair, DAS) and were randomized to 1 of 3 defect groups (isolated Bankart lesion, 10% anterior glenoid defect, 20% anterior glenoid defect). The DAS was performed by transferring the LHB tendon through a subscapularis split to the anterior glenoid margin, where it was fixed with an interference screw. Results: Both surgical techniques resulted in decreased anterior glenohumeral translation in comparison with the defect conditions in all defect groups. As compared with isolated Bankart repair, DAS showed significantly less relative anterior translation in 10% glenoid defects at translation forces of 20 N (0.3 +/- 1.7 mm vs 2.2 +/- 1.8 mm, P = .005) and 30 N (2.6 +/- 3.4 mm vs 5.3 +/- 4.2 mm, P = .044) and in 20% glenoid defects at all translation forces (20 N: -3.2 +/- 4.7 mm vs 0.8 +/- 4.1 mm, P = .024; 30 N: -0.9 +/- 5.3 mm vs 4.0 +/- 5.2 mm, P = .005; 40 N: 2.1 +/- 6.6 mm vs 6.0 +/- 5.7 mm, P = .035). However, in 20% defects, DAS led to a relevant posterior and inferior shift of the humeral head in the ABER position and to a relevant increase in inferior glenohumeral translation. Both surgical techniques did not limit the rotational range of motion. Conclusion: In the context of minor glenoid bone defects, the DAS technique demonstrates less relative anterior translation as compared with an isolated Bankart repair at time zero.
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Abstract This article provides an anatomical and biomechanical framework for the postoperative management and progression of treatment for shoulder arthroplasty. The clinical relevance of normal shoulder anatomy, biomechanics, and...
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Abstract This article provides an anatomical and biomechanical framework for the postoperative management and progression of treatment for shoulder arthroplasty. The clinical relevance of normal shoulder anatomy, biomechanics, and pathomechanics related to this surgery is emphasized to provide the reader with an understanding of the rationale for treatment. We review the rehabilitation implications of surgical indications and technique for both traditional total shoulder arthroplasty and reverse total shoulder arthroplasty procedures with an emphasis on biomechanical considerations. Relevant factors that affect rehabilitation outcomes are discussed along with supporting evidence from the literature. Principles to guide and progress treatment are highlighted with a discussion on return to sports with the ultimate objective of providing a comprehensive approach for successful rehabilitation.
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Background: Bone loss in anterior glenohumeral instability occurs on both the glenoid and the humerus; however, existing biomechanical studies have evaluated glenoid and humeral head defects in isolation. Thus, little is known abo...
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Background: Bone loss in anterior glenohumeral instability occurs on both the glenoid and the humerus; however, existing biomechanical studies have evaluated glenoid and humeral head defects in isolation. Thus, little is known about the combined effect of these bony lesions in a clinically relevant model on glenohumeral stability.
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To validate the assumption that the center of rotation in the glenohumeral (GH) joint can be described based on the geometry of the joint, two methods for calculation of the CH rotation center were compared. These are a kinematic ...
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To validate the assumption that the center of rotation in the glenohumeral (GH) joint can be described based on the geometry of the joint, two methods for calculation of the CH rotation center were compared. These are a kinematic estimation based on the calculation of instantaneous helical axes, and a geometric estimation based on a spherical fit through the surface of the glenoid. Four fresh cadaver arms were fixed at the scapula and fitted with electromagnetic sensors. Each arm was moved in different directions while at the same time the orientation of the humerus was recorded. Subsequently, each specimen was dissected and its glenoid and humeral head surfaces were digitized. Results indicate no differences between the methods. It is concluded that the method to estimate the GH center of rotation as the center of a sphere through the glenoid surface, with the radius of the humeral head, appears to be valid. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 13]
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Modem human shoulder function is affected by the evolutionary adaptations that have occurred to ensure survival and prosperity of the species. Robust examination of behavioral shoulder performance and injury risk can be holistical...
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Modem human shoulder function is affected by the evolutionary adaptations that have occurred to ensure survival and prosperity of the species. Robust examination of behavioral shoulder performance and injury risk can be holistically improved through an interdisciplinary approach that integrates anthropology and biomechanics. Coordination of these fields can allow different perspectives to contribute to a more complete interpretation of biomechanics of the modem human shoulder. The purpose of this study was to develop a novel biomechanical and comparative chimpanzee glenohumeral model, designed to parallel an existing human glenohumeral model, and compare predicted musculoskeletal outputs between the two models. The chimpanzee glenohumeral model consists of three modules - an external torque module, a musculoskeletal geometric module and an internal muscle force prediction module. Together. these modules use postural kinematics, subject-specific anthropometrics, a novel shoulder rhythm, glenohumeral stability ratios, hand forces, musculoskeletal geometry and an optimization routine to estimate joint reaction forces and moments, subacromial space dimensions, and muscle and tissue forces. Using static postural data of a horizontal bimanual suspension task, predicted muscle forces and subacromial space were compared between chimpanzees and humans. Compared with chimpanzees, the human model predicted a 2 mm narrower subacromial space, deltoid muscle forces that were often double those of chimpanzees and a strong reliance on infraspinatus and teres minor (60-100% maximal force) over other rotator cuff muscles. These results agree with previous work on inter-species differences that inform basic human rotator cuff function and pathology.
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? 2022Study Design: Invited review. Background: Shoulder osteoarthritis can result in significant functional deficits. To improve diagnosis and treatment, we must better understand the impact of osteoarthritis on shoulder biomecha...
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? 2022Study Design: Invited review. Background: Shoulder osteoarthritis can result in significant functional deficits. To improve diagnosis and treatment, we must better understand the impact of osteoarthritis on shoulder biomechanics and the known mechanical benefits of currently available treatments. Purpose: The purpose of this paper is to present up-to-date data on the effects of osteoarthritis and rehabilitation on the biomechanical parameters contributing to shoulder function. With this goal, we also reviewed the anatomy and the ranges of motion of the shoulder. Methods: A search of electronic databases was conducted. All study designs were included to inform this qualitative, narrative literature review. Results: This review describes the biomechanics of the shoulder, the impact of osteoarthritis on shoulder function, and the treatment of shoulder osteoarthritis with an emphasis on rehabilitation. Conclusions: The shoulder is important for the completion of activities of daily living, and osteoarthritis of the shoulder can significantly reduce shoulder motion and arm function. Although shoulder rehabilitation is an integral treatment modality to improve pain and function in shoulder osteoarthritis, few high-quality studies have investigated the effects and benefits of shoulder physical and occupational therapies. To advance the fields of therapy and rehabilitation, future studies investigating the effects of therapy intensity, therapy duration, and the relative benefits of therapy subtypes on shoulder biomechanics and function are necessary.
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Osteoarthritis (OA) of the glenohumeral joint constitutes the most frequent indication for nontraumatic shoulder joint replacement. Recently, a small critical shoulder angle (CSA) was found to be associated with a high prevalence ...
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Osteoarthritis (OA) of the glenohumeral joint constitutes the most frequent indication for nontraumatic shoulder joint replacement. Recently, a small critical shoulder angle (CSA) was found to be associated with a high prevalence of OA. This study aims to verify the hypothesis that a small CSA leads to higher glenohumeral joint reaction forces during activities of daily living than a normal CSA. A shoulder simulator with simulated deltoid (DLT), supraspinatus (SSP), infraspinatus/teres minor (ISP/TM), and subscapularis (SSC) musculotendinous units was constructed. The DLT wrapping on the humerus was simulated using a pulley that could be horizontally adjusted to simulate the 28 degrees CSA found in OA or the 33 degrees CSA found in disease-free shoulders. Over a range of motion between 6 degrees and 82 degrees of thoracohumeral abduction joint forces were measured using a six-axis load cell. An OA-associated CSA yielded higher net joint reaction forces than a normal CSA over the entire range of motion. The maximum difference of 26.4N (8.5%) was found at 55 degrees of thoracohumeral abduction. Our model thus suggests that a CSA typical for OA predisposes the glenohumeral joint to higher joint reaction forces and could plausibly play a role in joint overloading and development of OA. (c) 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1047-1052, 2016.
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Climbing is an increasingly popular recreational and competitive behavior, engaged in a variety of environments and styles. However, injury rates are high in climbing populations, especially in the upper extremity and shoulder. De...
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Climbing is an increasingly popular recreational and competitive behavior, engaged in a variety of environments and styles. However, injury rates are high in climbing populations, especially in the upper extremity and shoulder. Despite likely arising from an arboreal, climbing ancestor and being closely related to primates that are highly proficient climbers, the modern human shoulder has devolved a capacity for climbing. Limited biomechanical research exists on manual climbing performance. This study assessed kinematic and muscular demands during a bimanual climbing task that mimicked previous work on climbing primates. Thirty participants were recruited - 15 experienced and 15 inexperienced climbers. Motion capture and electromyography (EMG) measured elbow, thoracohumeral and trunk angles, and activity of twelve shoulder muscles, respectively, of the right-side while participants traversed across a horizontal climbing apparatus. Statistical parametric mapping was used to detect differences between groups in kinematics and muscle activity. Experienced climbers presented different joint motions that more closely mimicked the kinematics of climbing primates, including more elbow flexion (p = 0.0045) and internal rotation (p = 0.021), and less thoracohumeral elevation (p = 0.046). Similarly, like climbing primates, experienced climbers generally activated the shoulder musculature at a lower percentage of maximum, particularly during the exchange from support to swing and swing to support phase. However, high muscle activity was recorded in all muscles in both participant groups. Climbing experience coincided with a positive training effect, but not enough to overcome the high muscular workload of bimanual climbing. Owing to the evolved primary usage of the upper extremity for low force, below shoulder-height tasks, bimanual climbing may induce high risk of fatigue-related musculoskeletal disorders. (C) 2019 Elsevier Ltd. All rights reserved.
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Digitizing bony landmarks is a common technique used to measure scapular position, but it has not been validated against a gold standard. The aim of this study was to determine the accuracy of this technique for four physiological...
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Digitizing bony landmarks is a common technique used to measure scapular position, but it has not been validated against a gold standard. The aim of this study was to determine the accuracy of this technique for four physiological arm movements using optoelectronic markers mounted on scapular bone pins as a gold standard. Eight subjects had bone pins inserted into their lateral scapular spine. Three points were digitized on the scapula with an optoelectronic probe: the medial root of the scapular spine, the posterolateral corner of the acromion, and the inferior angle of the scapula. The four active movements tested in this study were glenohumeral abduction, glenohumeral horizontal adduction, hand behind back, and forward reaching. The three bony landmarks were digitized six times in three different positions for each movement. Data from one subject were rejected secondary to pin loosening. The overall position-specific r.m.s. errors ranged from 2.0° to 12.5°. The full abduction position had considerably higher r.m.s. errors than the other positions (posterior tipping, 12.5°; upward rotation, 7.3°; internal rotation, 12.0°). It appears that the digitization of bony landmarks may be a valid method for measuring changes in scapular attitude with the following caveats: the full abduction position has a high r.m.s. error, and small scapular motions have high percentage errors.
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This study described the three-dimensional shoulder motion during the arm elevation in individuals with isolated acromioclavicular osteoarthritis (ACO) and ACO associated with rotator cuff disease (RCD), as compared to controls. S...
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This study described the three-dimensional shoulder motion during the arm elevation in individuals with isolated acromioclavicular osteoarthritis (ACO) and ACO associated with rotator cuff disease (RCD), as compared to controls. Seventy-four participants (ACO = 23, ACO + RCD = 25, Controls = 26) took part of this study. Disability was assessed with the DASH, three-dimensional kinematics were collected during arm elevation in the sagittal and scapular planes, and pain was assessed with the 11-point numeric pain rating scale. For each kinematic variable and demographic variables, separate linear mixed-model 2-way ANOVAs were performed to compare groups. Both ACO groups had higher DASH and pain scores. At the scapulothoracic joint, the isolated ACO group had greater internal rotation than control, and the ACO + RCD group had greater upward rotation than both other groups. At the sternoclavicular joint, both groups with ACO had less retraction, and the isolated ACO group had less elevation and posterior rotation. At the acromioclavicular joint, the isolated ACO group had greater upward rotation, and both ACO groups had greater posterior tilting. Patients with ACO had altered shoulder kinematics, which may represent compensatory responses to reduce pain and facilitate arm motion during arm elevation and lowering.
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