3-dimensional Scapular Kinematics Research Articles

The repeatability of 3-dimensional scapular kinematic analysis during bilateral upper extremity movements

Although three-dimensional electromagnetic systems are widely used to evaluate the 3-dimensional scapular kinematics their reliability when testing bilateral upper extremity tasks is unknown. The purpose of this study was to investigate the repeatability of the scapular kinematic analyses using the Flock of Birds (FOB) system during bilateral upper extremity movements.Twenty-one volunteers without shoulder problems were included (aged 24.8 years; body mass index averaged 21.2 kg/m2) to the study. Scapular internal-external rotation, upward-downward rotation, and anterior-posterior tilt was recorded during bilateral arm elevation on sagittal, scapular and frontal planes. Measurements were repeated at 5–7 days intervals. Intra-session and inter-session repeatability were determined using intraclass correlation coefficients (ICC) scores and standard errors of measurements (SEM).The ICC scores were found to be 0.81 to 0.99 for intra-session measurements and 0.60 to 0.83 for inter-session measurements. The SEM scores were 0.8°–3.4° and 2°–7.2° for the intra and inter-session measurements respectively.The repeatability of the FOB system was excellent for the intra-session measurements, but it was weaker for the inter-session measurements. These results support the use of the FOB system for assessing scapular orientation but the analyses should be conducted more carefully when it is applied to the longitudinal measurements.

Analysis of Scapular Kinematics and Muscle Activity by Use of Fine-Wire Electrodes During Shoulder Exercises

Background: During nonoperative or postoperative rehabilitation after sports injuries, exercise selection is often based on minimal load on the injured/repaired glenohumeral structures, while optimally activating scapulothoracic muscles. Previous research explored scapular muscle activity during rehabilitation exercises using surface electromyography (EMG). However, limited information exists about the deeper lying muscle activity, measured with fine-wire electrodes, even more in combination with 3-dimensional scapular kinematics. Purpose: To report scapular kinematics synchronously with surface and fine-wire EMG during specific shoulder exercises for early rehabilitation. Study Design: Descriptive laboratory study. Methods: A total of 23 healthy male patients were recruited. Three-dimensional scapular kinematics were measured combined with EMG recording of 8 muscles during 4 commonly used shoulder exercises (inferior glide, low row, lawnmower, and robbery). Upper (UT), middle (MT), and lower (LT) trapezius and serratus anterior muscle activities were measured with bipolar surface electrodes. Intramuscular electrodes were placed in the levator scapulae (LS), rhomboid major (RM), pectoralis minor (Pm), and infraspinatus (IS) muscles. All data were normalized as a percentage of maximal voluntary isometric contraction (%MVIC). A linear mixed model with Bonferroni correction was applied for statistical analysis. Results: Scapular kinematics revealed an anterior tilt position during the inferior glide, low row, and robbery (P < .05). An upward rotation position between 20° and 30° was reached in all exercises except low row. Inferior glide (31°) and low row (42°) represented a significantly increased internal rotation position compared with lawnmower and robbery. Lawnmower and robbery showed significantly (P < .05) more MT (lawnmower, 36% MVIC; robbery, 39% MVIC) and RM (lawnmower, 59% MVIC; robbery, 66% MVIC) activation compared with inferior glide and low row. Lawnmower and robbery showed significantly (P < .05) less Pm activation (9.5%-12% MVIC). LS was significantly more active during robbery (58% MVIC) compared with inferior glide and low row (27%-36% MVIC) (P < .05). IS showed moderate activity (24%-37% MVIC) for all exercises, except low row (13% MVIC). Conclusion/Clinical Relevance: This study provides new insights about scapular positions and activation of the deeper layer muscles during 4 commonly used shoulder rehabilitation exercises. The lawnmower showed a favorable position of the scapula with less Pm activity in contrast to the low row. The inferior glide, lawnmower, and robbery should not be implemented in early phases of shoulder rehabilitation because of their moderate muscle activity.

Alterations in the 3-dimensional scapular orientation in patients with non-specific neck pain

BackgroundAlthough it is thought that there is a relationship between neck pain and scapular dysfunction, there are controversial results and no clear information in the literature regarding this issue. This study aimed to investigate the alterations in the 3-Dimensional scapular orientation on patients with non-specific neck pain. MethodThirty-four patients with chronic non-specific neck pain [age, 29.1 (5) years; height, 165.3 (6.1) centimeters; weight, 62.1 (9.6) kilogram] and 29 healthy controls [age, 28.2 (3.3) years; height, 166.8 (8.1) centimeters; weight, 60.9 (8.5) kilogram] were included in the study. 3-Dimensional scapular kinematics were obtained during arm elevation and lowering trials in the sagittal, scapular, and frontal planes. FindingsCompared to healthy controls, the patients with neck pain demonstrated significantly reduced upward scapular rotation on both the dominant and non-dominant sides in all three planes. Patients with neck pain had increased internal rotation in the sagittal and frontal planes on the dominant side and increased external rotation in the frontal plane on the non-dominant side. No difference was observed between groups considering posterior scapular tilt. InterpretationThere are alterations in the 3-Dimensional scapular orientations in patients with chronic non-specific neck pain compared to healthy controls. Therefore, the scapular control may also be examined in patients with neck pain and it can be included in the rehabilitation program if needed.

Does scapular corrective taping alter periscapular muscle activity and 3-dimensional scapular kinematics? A systematic review

Study DesignThis is a systematic review. IntroductionScapular taping is widely used in the management of scapular dysfunction. However, its effects on the scapular kinematics and the electromyography (EMG) activity of the periscapular muscles are not clear. Purpose of the StudyThe purpose of the study was to systematically review the current literature to examine whether scapular corrective taping alters the EMG activity of the periscapular muscles and the 3-dimensional scapular kinematics. MethodMEDLINE and Web of Science databases were searched using specific mesh terms up to April 2018. A hand search was also conducted on the reference list of the included articles. A total of 157 studies were identified, and they were further analyzed for the eligibility to the systematic review. Studies that investigated the effects of scapular corrective taping on the EMG activity of the periscapular muscles and on the 3-dimensional scapular kinematics on patients with shoulder problems or asymptomatic subjects were eligible for the systematic review. The Cochrane Effective Practice and Organization of Care criteria were modified and used for the risk-of-bias assessment. ResultsEleven articles met the inclusion criteria and were included in the systematic review. Five studies investigated the effects of corrective taping on the scapular kinematics and 8 studies reported the effects of corrective taping on the EMG activity of the periscapular muscles. There was an agreement among the studies that scapular upward rotation is increased with the corrective taping, while there are inconsistent results concerning the scapular external rotation and posterior tilt. In addition, studies mostly reported that corrective taping decreases the activity of the upper trapezius, while it has conflicting effects on the activity patterns of other periscapular muscles. DiscussionScapular corrective taping was found to increase the scapular upward rotation; however, its effects on scapular external rotation and posterior tilt are controversial. It was also found that corrective taping might decrease the EMG activity of the upper trapezius, while it had no effects on the activity of lower trapezius, and its effects on other periscapular muscles were controversial. ConclusionThe results of the studies indicated that scapular corrective taping might alter the 3-dimensional scapular kinematics, while there are controversies about the effects of corrective taping on the EMG activity of the periscapular muscles. Further studies are needed to clarify the conflicts.

Repositioning the scapula with taping following distal radius fracture: Kinematic analysis using 3-dimensional motion system

Study DesignCross-sectional and controlled laboratory study using pretest-posttest design. IntroductionPatients with distal radius fracture (DRfx) report proximal segment problems. Taping is commonly recommended because it provides improved posture and function. Purpose of the StudyThis study aimed to investigate the 3-dimensional scapular kinematics and the effect of taping on the kinematics in participants with DRfx. MethodsTwenty participants with a unilateral history of DRfx and 20 healthy controls participated. Scapular kinematics was assessed using an electromagnetic system. Three separate strips of elastic taping were applied for participants with DRfx over the arm, scapula, and middle and lower trapezius muscles through the paravertebral muscles. Afterward, the scapular kinematics was reassessed in taped condition. ResultsWhen participants with DRfx and healthy controls compared, the scapula was more downwardly rotated at 120° of humerothoracic elevation (mean difference [MD], 9.06°) and at 120° (MD, 9.04°), 90° (MD, 5.6°) of humerothoracic lowering, more upwardly rotated at 30° of humerothoracic lowering (MD, 5.1°). Taping showed a significant effect on kinematics; specifically, the scapula was more externally rotated (38.9° untaped vs 31.1° taped) and posteriorly tilted (−9.2° untaped vs −4.8° taped) during humerothoracic elevation and lowering for participants with DRfx. DiscussionParticipants with DRfx showed different scapular kinematics and taping resulted in changes on tested kinematic parameters during humeral movements. Differences in scapular motion during elevation with taping showed a specific pattern. ConclusionsOverall, taping maintained a position likely to produce optimal rotator cuff function during early rehabilitation of patients with DRfx. Level of EvidenceN/A.

Effects of Scapular Stabilization Exercise Training on Scapular Kinematics, Disability, and Pain in Subacromial Impingement: A Randomized Controlled Trial

ObjectiveTo investigate the effects of 2 different exercise programs on 3-dimensional scapular kinematics, disability, and pain in participants with subacromial impingement syndrome (SIS). DesignRandomized controlled trial. SettingOutpatient clinic and research laboratory. ParticipantsParticipants who were diagnosed with SIS and who also exhibited scapular dyskinesis (N=30). InterventionsThe participants were randomized in 2 different exercise groups: (1) shoulder girdle stretching and strengthening with additional scapular stabilization exercises based on a kinetic chain approach (intervention group), and (2) shoulder girdle stretching and strengthening exercises only (control group). Main Outcome MeasuresThree-dimensional scapular kinematics, self-reported shoulder pain, and disability were evaluated at baseline, after 6 weeks of training, and after 12 weeks of training. ResultsSignificant differences were observed between the control and intervention groups in external rotation and posterior tilt after 6 weeks of training and in external rotation, posterior tilt, and upward rotation after 12 weeks of training. All groups showed improvement in self-reported pain and disability scores; however, there were no significant differences between the groups. ConclusionsProgressive exercise training independent from specific scapular stabilization exercises provides decreased disability and pain severity in impingement syndrome.

Effects of short malunion of the clavicle on in vivo scapular kinematics

Short malunion of the clavicle after fracture can change scapular kinematics and alter clinical outcome. However, the effects of malunion on kinematics and outcomes remains poorly understood because there have been no in vivo studies measuring changes during active motion with malunion. This study aimed to measure and to compare in vivo 3-dimensional (3D) scapular kinematics between normal shoulders and shoulders with short malunion using 3D-2-dimensional model image registration techniques. Fifteen patients with clavicle fracture who had been treated conservatively were enrolled in this study. In these patients, the angle of scapular upward rotation, posterior tilting, and external rotation were compared between shoulders with short malunion and contralateral, normal shoulders. A 3D-2-dimensional model image registration technique was used to determine the 3D orientation of the scapula. Scapular upward rotation increased following increase of the arm elevation angle and also showed a significant difference by arm elevation in both groups (P = .04). Posterior tilting of the scapula gradually increased as the arm abduction angle increased, and this varied significantly between groups (P = .01). Shoulders with short malunion also showed a more internally rotated position than the contralateral, normal shoulders between 100° and the maximum abduction angle (P = .04). Our results suggest that clavicle shortening of >10% greatly affects scapular kinematics in vivo. Further studies will be needed to determine the clinical implications of short malunion of the clavicle.

THREE-DIMENSIONAL ANALYSIS OF SCAPULAR KINEMATICS DURING ARM ELEVATION IN BASEBALL PLAYERS WITH SCAPULAR DYSKINESIS: COMPARISON OF DOMINANT AND NON-DOMINANT ARMS

BackgroundThe knowledge of 3-dimensional (3D) scapular kinematics is essential for understanding the pathological lesions of shoulder and elbow in throwing athletes. To date, a number of studies about alterations of...

Effect of taping on 3-dimensional scapular kinematics and trapezius activity

Effect of taping on 3-dimensional scapular kinematics and trapezius activity

In vivo 3-dimensional analysis of scapular and glenohumeral kinematics: comparison of symptomatic or asymptomatic shoulders with rotator cuff tears and healthy shoulders

Alteration in shoulder kinematics has been suggested as one cause of symptoms in shoulders with rotator cuff tears (RCTs). However, only a few studies comparing symptomatic and asymptomatic RCTs using kinematic analysis have been performed. The purpose of this study was to compare 3-dimensional (3D) scapular and glenohumeral kinematics during scapular-plane abduction among symptomatic RCTs, asymptomatic RCTs, and healthy shoulders. This study included 7 healthy shoulders in subjects with a mean age of 62 years, 5 symptomatic RCTs in subjects with a mean age of 70 years, and 7 asymptomatic RCTs in subjects with a mean age of 67 years. All shoulders with RCTs had medium-sized tears (1-3 cm in the coronal plane) that were confirmed with magnetic resonance imaging. Biplane fluoroscopic images during scapular-plane abduction were recorded, and computed tomography-derived 3D bone models were matched with the silhouettes of the bones on the fluoroscopic images using 3D/2-dimensional model-image registration techniques. Angular values of the scapula and glenohumeral kinematics were compared among the 3 groups. Posterior tilt of the scapula was significantly smaller in the symptomatic RCTs (3.1° ± 1.8°) than in healthy shoulders (10.4° ± 0.8°) (P = .049). The humerus of the symptomatic shoulders was less externally rotated relative to the scapula throughout the activity than the healthy shoulders and asymptomatic RCTs (P = .006 and P = .028 respectively). However, there were no kinematic differences between the asymptomatic RCTs and healthy shoulders. Kinematic changes in symptomatic RCTs might be associated with development of symptoms. Improvement of these kinematic changes may be a key to successful conservative treatment for symptomatic RCTs.

The Scapular Assistance Test Results in Changes in Scapular Position and Subacromial Space but Not Rotator Cuff Strength in Subacromial Impingement

Controlled laboratory study. To determine the effect of the modified scapular assistance test (SAT) on 3-dimensional shoulder kinematics, strength, and linear measures of subacromial space in patients with subacromial impingement syndrome (SAIS). Abnormal scapular kinematics have been identified in patients with SAIS. Increased scapular upward rotation and posterior tilt, as induced with manual assistance using the SAT, have been theorized to increase subacromial space and may alter shoulder strength. Forty-two subjects (21 with SAIS and 21 controls) participated in this study. The anterior outlet of the subacromial space, measured via the acromiohumeral distance on ultrasound images, and 3-dimensional scapular kinematics, measured using motion analysis, were determined with the arm at rest, and at 45° and 90° of active elevation with and without the SAT. A dynamometer was used to measure isometric shoulder strength. Full factorial mixed-model analyses of variance evaluated the effects of the SAT on variables between groups. There was an increase in scapular posterior tilt at all angles, upward rotation at rest and 45° of elevation, and acromiohumeral distance at 45° and at 90° with the SAT. The SAT did not alter normalized isometric strength. There were no differences in response to the SAT between the SAIS and control groups. Manual scapular assistance using the SAT influences factors associated with SAIS, such as subacromial space and potentially scapular orientation during static arm elevation, but not more so in individuals with SAIS than in healthy individuals. The SAT performed statically may be a way to identify potential subgroups of individuals with SAIS for whom subacromial space narrowing may be a contributing factor.

Shoulder External Rotation Fatigue and Scapular Muscle Activation and Kinematics in Overhead Athletes

Glenohumeral external rotation (GH ER) muscle fatigue might contribute to shoulder injuries in overhead athletes. Few researchers have examined the effect of such fatigue on scapular kinematics and muscle activation during a functional movement pattern. To examine the effects of GH ER muscle fatigue on upper trapezius, lower trapezius, serratus anterior, and infraspinatus muscle activation and to examine scapular kinematics during a diagonal movement task in overhead athletes. Human performance research laboratory. Descriptive laboratory study. Our study included 25 overhead athletes (15 men, 10 women; age = 20 ± 2 years, height = 180 ± 11 cm, mass = 80 ± 11 kg) without a history of shoulder pain on the dominant side. We tested the healthy, dominant shoulder through a diagonal movement task before and after a fatiguing exercise involving low-resistance, high-repetition, prone GH ER from 0° to 75° with the shoulder in 90° of abduction. Surface electromyography was used to measure muscle activity for the upper trapezius, lower trapezius, serratus anterior, and infraspinatus. An electromyographic motion analysis system was used to assess 3-dimensional scapular kinematics. Repeated-measures analyses of variance (phase × condition) were used to test for differences. We found a decrease in ascending-phase and descending-phase lower trapezius activity (F(1,25) = 5.098, P = .03) and an increase in descending-phase infraspinatus activity (F(1,25) = 5.534, P = .03) after the fatigue protocol. We also found an increase in scapular upward rotation (F(1,24) = 3.7, P = .04) postfatigue. The GH ER muscle fatigue protocol used in this study caused decreased lower trapezius and increased infraspinatus activation concurrent with increased scapular upward rotation range of motion during the functional task. This highlights the interdependence of scapular and glenohumeral force couples. Fatigue-induced alterations in the lower trapezius might predispose the infraspinatus to injury through chronically increased activation.

In vivo 3-dimensional analysis of scapular kinematics: comparison of dominant and nondominant shoulders

Alterations in scapular motion frequently are seen in association with various shoulder disorders. It is common clinically to compare the pathological shoulder with the contralateral shoulder, in spite of arm dominance, to characterize the disorder. However, there have been few articles that test the underlying assumption that dominant and nondominant shoulders exhibit comparable dynamic kinematics. The purpose of this study was to compare the 3-dimensional (3-D) scapular kinematics of dominant and nondominant shoulders during dynamic scapular plane elevation using 3-D-2-D (2-dimensional) registration techniques. Twelve healthy males with a mean age of 32 years (range, 27-36) were enrolled in this study. Bilateral fluoroscopic images during scapular plane elevation and lowering were taken, and CT-derived 3-D bone models were matched with the silhouette of the bones in the fluoroscopic images using 3-D-2-D registration techniques. Angular values of the scapula and scapulohumeral rhythm were compared between dominant and nondominant shoulders with statistical analysis. There was a significant difference in upward rotation angles between paired shoulders (P < .001), while significant differences were not found in the other angular values and scapulohumeral rhythm. The dominant scapulae were 10° more downwardly rotated at rest and 4° more upwardly rotated during elevation compared to the nondominant scapulae. Scapular motion was not the same between dominant and nondominant arms in healthy subjects. The dominant scapula was rotated further downward at rest and reached greater upward rotation with abduction. These differences should be considered in clinical assessment of shoulder pathology.

Asymmetric Resting Scapular Posture in Healthy Overhead Athletes

Observation of the scapular posture is one of the most important components of the physical examination in overhead athletes. Postural asymmetry is typically considered to be associated with injuries. However, asymmetry in the overhead athlete's scapula may be normal due to the dominant use of the limb. To quantify the differences in resting scapular posture between the dominant and nondominant sides in 3 groups of healthy overhead athletes (baseball pitchers, volleyball players, and tennis players) using an electromagnetic tracking device. Cross-sectional design. University-based biomechanics laboratory. A total of 43 players participated, including 15 baseball pitchers, 15 volleyball players, and 13 tennis players. All participants were healthy college-aged men. Bilateral 3-dimensional scapular kinematics with the arm at rest were measured using an electromagnetic tracking device. Bilateral scapular position and orientation were measured. Between-groups and between-sides differences in each variable were analyzed using separate analyses of variance. In tennis players, the scapula was more protracted on the dominant side than on the nondominant side (P < .05). In all overhead athletes, the dominant-side scapula was more internally rotated (P = .001) and anteriorly tilted (P = .001) than the nondominant-side scapula was. The dominant-side scapula of the overhead athletes was more internally rotated and anteriorly tilted than the nondominant-side scapula. The dominant-side scapula of the tennis players was more protracted than that on the nondominant side. Clinicians evaluating overhead athletes need to recognize that scapular posture asymmetry in unilateral overhead athletes may be normal. Our results emphasize the importance of the baseline evaluation in this population in order to accurately assess pathologic change in bilateral scapular positions and orientations after injury.

Relationship of glenohumeral elevation and 3-dimensional scapular kinematics with disability in patients with shoulder disorders

To determine variables among glenohumeral elevation and 3-dimensional scapular rotations that are related to shoulder function as assessed by the Disability of the Arm, Shoulder and Hand-Disability/Symptom (DASH-D/S) scale. Prospective, cross-sectional study. Eighty-eight patients with shoulder pain and limited range of motion were included. Each patient performed 2 full active range of motion activities, forward flexion and abduction, and 2 activities of daily living, combing hair and simulating washing the back. Glenohumeral elevation and scapular rotations were measured by the Polhemus Fastrak electromagnetic system. On multiple regression analysis, glenohumeral elevation in combing hair and scapular lateral rotation in both abduction and simulating washing the back were the best predictors of shoulder function and explained 39.7% of the variance of the DASH-D/S score. These findings support the classical rehabilitation of the shoulder based on glenohumeral elevation and suggest the importance of attention paid to scapular lateral rotation.

Shoulder Function and 3-Dimensional Scapular Kinematics in People With and Without Shoulder Impingement Syndrome

Several factors such as posture, muscle force, range of motion, and scapular dysfunction are commonly believed to contribute to shoulder impingement. The purpose of this study was to compare 3-dimensional scapular kinematics, shoulder range of motion, shoulder muscle force, and posture in subjects with and without primary shoulder impingement syndrome. Forty-five subjects with impingement syndrome were recruited and compared with 45 subjects without known pathology or impairments matched by age, sex, and hand dominance. Shoulder motion and thoracic spine posture were measured goniometrically, and force was measured with a dynamometer. An electromagnetic motion analysis system was used to capture shoulder kinematics during active elevation in both the sagittal and scapular planes as well as during external rotation with the arm at 90 degrees of elevation in the frontal plane. The impingement group demonstrated slightly greater scapular upward rotation and clavicular elevation during flexion and slightly greater scapular posterior tilt and clavicular retraction during scapular-plane elevation compared with the control group. The impingement group demonstrated less range of motion and force in all directions compared with the control group. There were no differences in resting posture between the groups. The kinematic differences found in subjects with impingement may represent scapulothoracic compensatory strategies for glenohumeral weakness or motion loss. The decreased range of motion and force found in subjects with impingement support rehabilitation approaches that focus on strengthening and restoring flexibility.

Shoulder Function and 3-Dimensional Kinematics in People With Shoulder Impingement Syndrome Before and After a 6-Week Exercise Program

Shoulder impingement syndrome is a common condition and is often managed with an exercise program. The purpose of this study was to examine an exercise program in patients with shoulder impingement syndrome. Specifically, the purpose was to identify changes that might occur in 3-dimensional scapular kinematics, physical impairments, and functional limitations. Fifty-nine patients with impingement syndrome were recruited, and 39 patients successfully completed the 6-week rehabilitation program and follow-up testing. Impingement was defined as having at least 3 of 6 predefined clinical signs or symptoms. Subjects were assessed before and after a 6-week rehabilitation program and again at 6 months. Pain, satisfaction, and function were measured using the University of Pennsylvania Shoulder Scale. Range of motion, isometric muscle force, and 3-dimensional scapular kinematic data also were collected. Subjects were given a progressive exercise program that included resistive strengthening, stretching, and postural exercises that were done daily at home. Subjects also were given shoulder education related to anatomy, the basic mechanics of impingement, and strategies for reducing load on the shoulder. Each subject attended one physical therapy session per week for a 6-week period, primarily for monitoring and upgrading the exercise program. Pretest and posttest scores were compared using paired t tests and repeated-measures analysis of variance. Passive range of motion increased for both external and internal rotation but not for elevation. Abduction external and internal rotation force all increased. There were no differences in scapular kinematics. Improvements were found for pain, satisfaction, and shoulder function and for Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) scores related to physical function. At 6-month follow-up, improvements made in pain, satisfaction, and function were maintained. The use of this exercise protocol in the management of shoulder impingement syndrome may have a positive impact on patients' impairments and functional limitations. Our findings suggest a relatively simple exercise program combined with patient education may be effective and, therefore, merits study in a larger trial using a control group. Changes in scapular kinematics did not appear to be a primary mechanism underlying improvement in symptoms and function.

Effects of muscle fatigue on 3-dimensional scapular kinematics

Tsai N-T, McClure PW, Karduna AR. Effects of muscle fatigue on 3-dimensional scapular kinematics. Arch Phys Med Rehabil 2003;84:1000-5. Objective:To determine the effects of fatigue during an external rotation task on 3-dimensional scapular kinematics. Design:A single-group, pretest-posttest measurement design. Setting:Research laboratory. Participants:Thirty healthy subjects. Interventions:Not applicable. Main Outcome Measures:Three-dimensional scapular kinematics were recorded with a Polhemus magnetic tracking device during arm elevation in the scapular plane. Results:There was a significant fatigue effect for all scapular rotations in the early to middle phases of humeral elevation. Significantly less posterior tilting (up to 90° of elevation), external rotation (up to 120° of elevation), and upward rotation (up to 60° of elevation) were observed. Additionally, there were fair to good correlations (r range, .39–.60) between the changes in scapular posterior tilting and the amount of muscle fatigue. Conclusions:Fatigue in shoulder external rotation altered the scapular resting position and the movement of posterior tilting in the early range during arm elevation in the scapular plane. Observed changes in scapular kinematics may affect the amount of area in the subacromial space and facilitate impingement. Data regarding changes produced by fatigue of the external rotators may also help with the development of a model of diminished rotator cuff function.

Effect of sitting posture on 3-dimensional scapular kinematics measured by skin-mounted electromagnetic tracking sensors

Finley MA, Lee RY. Effect of sitting posture on 3-dimensional scapular kinematics measured by skin-mounted electromagnetic tracking sensors. Arch Phys Med Rehabil 2003;84:563-8. Objective: To determine the effect of trunk sitting posture on scapular kinematics during humeral elevation by using skin-mounted electromagnetic tracking sensors. Design: Repeated-measures design contrasting scapular kinematics in 2 different sitting postures. Setting: A biomechanics laboratory in Hong Kong with a real-time, 3-dimensional electromagnetic tracking device for measuring movements of the scapula. Participants: A sample of 16 healthy adults (12 women, 4 men; age, 21.6[plusmn]3.92y) with full, pain-free shoulder range of motion and no history of shoulder pathology. Interventions: Not applicable. Main Outcome Measures: Movements of the scapula were measured while each subject performed humeral elevation in an upright seated position and a slouched seated position. Results: In both postures, posterior tip, lateral and upward rotation of the scapula, and lateral rotation of the humerus were observed during humeral elevation. When the slouched posture was adopted, there were significant decreases in the posterior tip and lateral rotation of the scapula, but there was no significant change in the magnitude of the upward rotation of the scapula. Conclusion: Increased thoracic kyphosis significantly alters the kinematics of the scapula during humeral elevation.