Effects of different arm external loads on the scapulo-humeral rhythm (original) (raw)
Related papers
The influence of handheld weight on the scapulohumeral rhythm
Journal of Shoulder and Elbow Surgery, 2008
Scapulohumeral rhythm (SHR) provides insight to neuromuscular control and fundamental biomechanics of the shoulder. This rhythm often is disrupted in pathologic shoulders. As the first step, we sought to quantify SHR in healthy subjects for diagnostic assessment of shoulder function. Ten healthy shoulders were studied. Threedimensional models of the humerus and scapula were created from computed tomography scans. Dynamic shoulder motion was recorded by use of single-plane fluoroscopy during arm abduction with 0-kg and 3-kg handheld loads. Shoulder kinematics were quantified by use of model-based 3-dimensional-to-2-dimensional registration techniques. SHR decreased (more scapular motion) with increasing abduction. With a 3-kg load, scapulothoracic motion was significantly reduced through the range of 35 to 45 of glenohumeral motion. Muscular stabilization of the scapula increased with external loading, as shown by decreased SHR during early lifting. Dynamic scapular stabilization provides a critical platform for upper extremity activity. (J Shoulder Elbow Surg 2008;17:943-946.) Inman et al 16 reported in 1944 that the ratio of glenohumeral (GH) motion to scapulothoracic (ST) motion, the scapulohumeral rhythm (SHR), was 2:1. More recent studies report varying ratios, where humeral motion predominates at lower levels of arm elevation and scapular motion predominates at higher levels. The changing SHR captures this biphasic pattern of scapular motion, providing an important parameter to characterize shoulder function during dynamic activity. Kibler 19 has suggested that the SHR often is disrupted in patients with symptoms and signs of shoulder impingement (subacromial or internal). A large percentage of patients with shoulder impingement have scapular dyskinesis and alterations in scapular position or in dynamic scapular motion. Thus, it is necessary for shoulder surgeons and physical therapists to understand how SHR changes with shoulder dysfunction. Though previously studied by use of a variety of methods, we introduce a new method, using equipment available in most hospitals, and apply this method to quantify SHR in healthy subjects.
Journal of Orthopaedic & Sports Physical Therapy, 1996
levation of the arm for overhead activities is accomplished by combined motion at multiple articulations of the shoulder, including the sternoclavicular, acromioclavicular, and glenohumeral joints (24,48). Some authors include the scapulothoracic articulation when describing shoulder anatomy and kinesiology (24,29). Due to the ligamentous and capsular attachments of the scapula to the clavicle and the clavicle to the sternum, scapulothoracic movement requires motion of the clavicle on the thorax at the sternoclavicular joint, motion of the scapula relative to the clavicle at the acromioclavicular joint, o r some combination of both (24). Scapulothoracic motion, therefore, is a summation of sternoclavicular and acromioclavicular motion, and, subsequently, elevation of the arm is frequently described in terms of scapulothoracic and glenohumeral components. Cathcart, while observing arm movements in living subjects, first suggested that glenohumeral and scapulothoracic motion occur synchronously when lifting the arm overhead (7). Codman later termed this synchronous motion, scapulohumeral rhythm (8). Since that time, a great deal of research in shoulder kinematics has been directed toward the study of scapulohumeral rhythm (2, 14,19,24,45,48). The majority of this Abnormal scapular kinematics and associated muscle function presumably contribute to shoulder pain and pathology. An understanding of scapular kinematic and electromyographic profiles in asymptomatic individuals can provide a basis for evaluation of pathology. The purpose of this study was to describe normal three-dimensional scapular orientation and associated muscle activity during humeral elevation. Twenty-five asymptomatic subjects, 19-37 years old, were evaluated. Digitized coordinate data and surface electromyographic signals from the trapezius (upper and lower), levator scapulae, and serratus anterior were colleaed at static positions of 0, 90, and 140" of humeral elevation in the scapular plane. The scapula demonstrated a pattern of progressive upward rotation, decreased internal rotation, and movement from an anteriorly to a posteriorly tipped position as humeral elevation angle increased. Electromyographic activity of all muscles studied increased with increased humeral elevation angles. Differences between mean values at all elevation angles for all variables were significant (p < .05), except for the lower trapezius between the 90 and 140" humeral angles. The results of this study suggest assessment of scapular tipping and internal rotation as well as upward rotation may be necessary to understand pathologies of the shoulder that are related to abnormal scapular kinematics.
Manual Therapy, 2015
Previous studies have stated that the scapulohumeral rhythm dysfunction can make person prone to glenohumeral joint pathologies. The purpose of this study was to compare scapular upward rotation and scapulohumeral rhythm between dominant and non-dominant shoulder in male overhead athletes and non-athletes. Seventeen overhead athletes and seventeen non-athletes volunteered for this study. Two inclinometers were used to measure humeral abduction and scapular upward rotation in rest position, 45 , 90 and 135 humeral abduction in frontal plane. Findings indicated there was no significant asymmetry in scapular upward rotation and scapulohumeral rhythm in different abduction angles between dominant and non-dominant shoulder in non-athletes. In contrast, overhead athletes' dominant shoulders have more downward rotation in scapular rest position and more upward rotation in 90 and 135 shoulder abduction than non-dominant shoulders. Also, overhead athletes presented scapulohumeral rhythm asymmetry between dominant and non-dominant shoulder in 90 and 135 humeral abduction as dominant shoulders have less scapulohumeral rhythm ratio than non-dominant shoulders. Furthermore, overhead athletes dominant shoulders have more scapular downward rotation in scapular rest position, more scapular upward rotation in 90 and 135 humeral abduction and less scapulohumeral rhythm ratio in 45 , 90 and 135 humeral abduction than non-athletes in dominant shoulders. We suggest that clinicians should be aware that some scapular asymmetry may be common in some athletes. It should not be considered as a pathological sign but rather an adaptation to extensive use of upper limb.
The Repeatability of Scapular Rotations Across Three Planes of Humeral Elevation
Research in Sports Medicine: An International Journal, 2005
Measurement of scapular kinematics is an important component in the assessment of shoulder function; however, repeatability of these measurements has not been established. The purpose of this study, therefore, was to determine the repeatability of scapular rotation measures for different humeral elevation planes between trials, sessions, and days. Three-dimensional scapular rotations were collected using an electromagnetic tracking system in three planes of humeral elevation. Coefficient of multiple correlation (CMC) values were calculated between trials, sessions, and days for curves of scapular rotations. CMC values were compared with repeated measures analysis of variance (ANOVAs) and Takey's post-hoc procedures. Tests of simple main effects were performed for significant interaction effects. Our results suggest that scapular rotation measures are repeatable between trials within the same testing session, but less repeatable between testing sessions and days. Sagittal plane elevation consistently yielded tlie highest CMC values for all scapular rotations. These results suggest sagittal plane elevation should be considered to evaluate differences in scapular rotations.
2005
The purpose of this study was to determine whether plane, end-range determination, or scapular motion affects shoulder range-of-motion measurements. In 16 healthy subjects, instrumentation with a magnetic tracking device was used to measure shoulder internal and external range of motion. The arm was supported while it was rotated either actively or passively with a measured torque. There was a significant main effect of plane for internal rotation (P Ͻ .001) but not for external rotation (P ϭ .584). Passive humerothoracic motion was significantly greater than active humerothoracic motion for internal rotation (P Ͻ .006) and external rotation (P Ͻ .01). Active and passive humerothoracic motion was significantly greater than active and passive glenohumeral motion in 6 of the 7 active conditions and all 7 passive conditions (P Ͻ .002). Our results suggest that significant amounts of scapulothoracic motion may impact measurements of isolated glenohumeral joint motion. (J Shoulder Elbow Surg 2005;14:602-610.) The shoulder is one of the most mobile joints in the human body and moves in a complex 3-dimensional pattern. This motion is accomplished through coordinated interactions between 3 diarthrodial articulations: the glenohumeral, acromioclavicular, and sternoclavicular joints, of which the former has the largest range of motion. However, this mobility comes at a price, as this joint is the most frequently dislocated in the body. Whereas active muscle contraction and glenoid geometry are primarily responsible for stability in the mid ranges of motion, the ligaments and capsular structures are mainly responsible for stability at the end ranges of motion. 36,46 A failure of any of these stabilizers can negatively affect shoulder kinematics and may result in decreased glenohumeral joint function. From a biomechanical perspective, the glenohumeral joint is typically described as having the following 3 degrees of rotational freedom: plane of motion, elevation, and internal and external rotation. 2 Although many of the traditional studies of shoulder motion have primarily focused on shoulder elevation, 20,43 there has been considerable interest of late in measuring internal and external rotation along the long axis of the humerus. 9,45 Study of this motion is important for two main reasons. First, the available range of internal and external rotation impacts shoulder function, from simple activities of daily living, such as hair combing, to more complex tasks required by athletes and occupational workers. Depending on the level of force applied throughout the shoulder joint, osseous and soft-tissue adaptations can result from repetitive shoulder motions. For example, bodybuilders have a decreased internal range of motion, 5 whereas professional baseball pitchers have an increased external range of motion coupled with a decreased internal range of motion. Second, measurements of internal and external rotation can be used as indicators of capsular tightness. Cadaveric studies using either selective cutting protocols 11,24,34,39,50 or strain measurements, 14,42,49,52 as well as numerical models, have been used to assess the extent to which various portions of the capsule limit rotation. Clinically, measurements of capsular tightness are used in the assessment of patients with impingement syndrome. The American Academy of Orthopaedic Surgeons' current recommendations for clinical measurement of shoulder rotation is by goniometer for external rotation with the arm at the side and for internal and external rotation with the arm at 90°of humeral abduction. In addition, internal rotation with the arm at the side is assessed by having the patient reach behind his or her back and noting what vertebral level can be reached with the thumb. These measurements are cost-effective and easy to perform and have fair to good intrarater and interrater reliability. 28 However, from a biomechanical perspec-From the
Journal of athletic training
Using constant, variable, and absolute error to measure movement accuracy might provide a more complete description of joint position sense than any of these values alone. To determine the effect of loaded movements and type of feedback on shoulder joint position sense and movement velocity. Applied study with repeated measures comparing type of feedback and the presence of a load. Laboratory. Twenty healthy subjects (age = 27.2 +/- 3.3 years, height = 173.2 +/- 18.1 cm, mass = 70.8 +/- 14.5 kg) were seated with their arms in a custom shoulder wheel. Subjects internally rotated 27 degrees in the plane of the scapula, with either visual feedback provided by a video monitor or proprioceptive feedback provided by prior passive positioning, to a target at 48 degrees of external rotation. Subjects performed the internal rotation movements with video feedback and proprioceptive feedback and with and without load (5% of body weight). High-speed motion analysis recorded peak rotational velo...