Shoulder Kinematics of Axillary Web Syndrome in Women Treated for Breast Cancer.

OBJECTIVE: To better understand how the shoulder moves in breast cancer survivors with axillary web syndrome (AWS), we compared 3-dimensional (3D) shoulder kinematics during shoulder elevation among breast cancer survivors with and without AWS 5 years postoperatively. Although research consistently shows decreased shoulder range of motion with AWS, we do not understand the underlying biomechanics. DESIGN: Nested case control study. SETTING: University Academic Breast Center. PARTICIPANTS: Twenty-five women who had surgery 5 years previously for unilateral breast cancer with the removal of at least 1 lymph node participated in this study (N=25). Twelve participants had AWS; 13 women did not have AWS. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Three-dimensional shoulder kinematic data during shoulder forward flexion, scapular plane abduction, and coronal plane abduction were collected using 3D electromagnetic motion tracking. Kinematic data were extracted at 30°, 60°, 90°, and 120° of arm elevation for scapular upward rotation, internal rotation, and posterior tilt as well as for glenohumeral external rotation. RESULTS: Women with AWS demonstrated 15.2° less scapular upward rotation at 120° humerothoracic elevation (95% confidence interval [-25.2, -5.2], P=.005), regardless of plane. No significant between-group differences were found for any other angle of scapular upward rotation, nor for scapular internal rotation, scapular posterior tilt, or glenohumeral axial rotation at any angle. CONCLUSIONS: Five years after surgery for breast cancer, women diagnosed with AWS have altered scapulohumeral kinematics that may place them at an increased risk of shoulder pain based on existing kinematic literature in healthy cohorts. This information can help guide rehabilitation programs for breast cancer survivors to facilitate pain-free upper extremity function after treatment.

Errors in Measuring Glenohumeral Arthrokinematics With 2-Dimensional Fluoroscopy.

Two-dimensional fluoroscopic imaging allows measurement of small magnitude humeral head translations that are prone to errors due to optical distortion, out-of-plane imaging, repeated manual identification of landmarks, and magnification. This article presents results from in vivo and in vitro fluoroscopy-based experiments that measure the errors and variability in estimating the humeral head translated position in true scapular plane and axillary views. The errors were expressed as bias and accuracy. The variability with repeated digitization was calculated using the intraclass correlation coefficient (ICC) and the standard error of measurement. Optical distortion caused underestimation of linear distances. The accuracy was 0.11 and 0.43 mm for in vitro and in vivo experiments, respectively, for optical distortion. The intrarater reliability was excellent for both views (ICC = .94 and .93), and interrater reliability was excellent (ICC = .95) for true scapular view but moderate (ICC = .74) for axillary views. The standard error of measurement ranged from 0.27 to 0.58 mm. The accuracy for the humeral head position in 10° out of true scapular plane images ranged from 0.80 to 0.87 mm. The current study quantifies the magnitude of error. The results suggest that suitable measures could be incorporated to minimize errors and variability for the measurement of glenohumeral parameters.

Bilateral magnetic resonance imaging findings in individuals with unilateral shoulder pain.

BACKGROUND: Magnetic resonance imaging (MRI) is commonly used to diagnose structural abnormalities in the shoulder. However, subsequent findings may not be the source of symptoms. The aim of this study was to determine comparative MRI findings across both shoulders of individuals with unilateral shoulder symptoms. MATERIALS AND METHODS: We prospectively evaluated 123 individuals from the community who had self-reported unilateral shoulder pain with no signs of adhesive capsulitis, no substantial range-of-motion deficit, no history of upper-limb fractures, no repeated shoulder dislocations, and no neck-related pain. Images in the coronal, sagittal, and axial planes with T1, T2, and proton density sequences were generated and independently and randomly interpreted by 2 examiners: a board-certified, fellowship-trained orthopedic shoulder surgeon and a musculoskeletal radiologist. Absolute and relative frequencies for each MRI finding were calculated and compared between symptomatic and asymptomatic shoulders. Agreement between the shoulder surgeon and the radiologist was also determined. RESULTS: Abnormal MRI findings were highly prevalent in both shoulders. Only the frequencies of full-thickness tears in the supraspinatus tendon and glenohumeral osteoarthritis were higher (approximately 10%) in the symptomatic shoulder according to the surgeon's findings. Agreement between the musculoskeletal radiologist and shoulder surgeon ranged from slight to moderate (0.00-0.51). CONCLUSION: Most abnormal MRI findings were not different in frequency between symptomatic and asymptomatic shoulders. Clinicians should be aware of the common anatomic findings on MRI when considering diagnostic and treatment planning.

Development and validation of a basic arthroscopy skills simulator.

PURPOSE: The purpose of our study was to develop a low-fidelity surgical simulator for basic arthroscopic skills training, with the goal of creating a pretrained novice ready with the basic skills necessary for all joint arthroscopic procedures. METHODS: A panel of education, arthroscopy, and simulation experts designed and evaluated a basic arthroscopic skills training and testing box. Task deconstruction was used to create 2 modules, which incorporate core skills common to all arthroscopic procedures. Core metrics measured were time to completion, number of trials to steady state, and number of errors. Face validity was evaluated using a questionnaire. Construct validity was examined by comparing 8 medical students with 8 expert orthopaedic surgeons. RESULTS: Surgeons were faster than students on both module 1 (P = .0013), simulating triangulation skills, and module 2 (P = .0190) simulating object manipulation skills. Surgeons demonstrated fewer errors (6.9 errors versus 28.1; P = .0073). All surgeons were able to demonstrate steady state (i.e., perform 2 trials that were within 10% of each other for time to completion and errors) on both modules within 3 trials on each module. Only 2 novices were able to demonstrate steady state on either module, and both did so within 3 trials. Furthermore, face validity of the skills trainer was shown by the expert arthroscopists. CONCLUSIONS: We describe a basic arthroscopy skills simulator that has face and construct validity. Our expert panel was able to design a simulator that differentiated between experienced arthroscopists and novices. CLINICAL RELEVANCE: Surgical simulation is an important part of efficient surgical education. This simulator shows good construct and face validity and provides a low-fidelity option for teaching the entry-level arthroscopist.

Effectiveness of home exercise on pain, function, and strength of manual wheelchair users with spinal cord injury: a high-dose shoulder program with telerehabilitation.

OBJECTIVE: To test the effectiveness of a high-dose home exercise/telerehabilitation program for manual wheelchair users who have a spinal cord injury (SCI) by determining whether the intervention would reduce pain and increase function, as we hypothesized. DESIGN: A pre-post trial with outcomes measured at 3 time points: baseline, postintervention (12wk), and follow-up (>24 wk). SETTING: Subjects performed an exercise program at their homes using telerehabilitation for therapist monitoring of technique and exercise advancement. Baseline and postintervention data were collected at a motion analysis laboratory in a tertiary medical center. PARTICIPANTS: A convenience sample of manual wheelchair users (N=16, 3 women; average age, 41y; average time in a wheelchair, 16y) with shoulder pain (average pain duration, 9y) and mechanical impingement signs on physical examination. INTERVENTIONS: A 12-week home exercise program of rotator cuff and scapular stabilization exercises was given to each participant. The program included a high dose of 3 sets of 30 repetitions, 3 times weekly, and regular physical therapist supervision via videoconferencing. MAIN OUTCOME MEASURES: Primary outcomes of pain and function were measured with the Wheelchair User's Shoulder Pain Index (WUSPI), Disabilities of Arm, Shoulder, and Hand (DASH) Index, and Shoulder Rating Questionnaire (SRQ). Secondary outcomes of strength were measured with isometric strength tests of scapulothoracic and glenohumeral muscles, and a static fatigue test of the lower trapezius. RESULTS: Pain was reduced and function improved after the intervention. There was a significant main effect for pain and function between the 3 time points based on the Friedman signed-ranked test, WUSPI (χ(2)2=5.10, P=.014), DASH Index (χ(2)2=5.41, P=.012), and SRQ (χ(2)2=23.71, P≤.001). Wilcoxon signed-rank tests demonstrated that isometric strength measurements of the serratus anterior and scapular retractors increased after the exercise intervention ([t=2.42, P=.04] and [t=4.67, P=.003], respectively). Muscle impulse produced by the lower trapezius during a fatigue task also improved (t=2.2, P=.02). No differences were measured in isometric strength for the lower trapezius, glenohumeral rotators, and abductors between the baseline and 12-week time points. CONCLUSIONS: A high-dose scapular stabilizer and rotator cuff strengthening program using telerehabilitation for supervision holds promise for shoulder pain treatment in manual wheelchair users with SCI. Additional work is needed to determine the effectiveness compared with other interventions, as well as the potential for earlier intervention to prevent development of shoulder pain.

Development of three-dimensional shoulder kinematic and electromyographic exposure variation analysis methodology in violin musicians.

A total of 11 male and 19 female violinists performed 30-second random-ordered slow and fast musical repertoire while right shoulder three-dimensional kinematic, and upper trapezius and serratus anterior surface electromyography (EMG) data were summarised using exposure variation analysis (EVA), a bivariate distribution of work time spent at categories of signal amplitude, and duration spent at a fixed category of amplitude. Sixty-two per cent of intraclass correlation coefficients [1,1] for all kinematic and EMG variables exceeded 0.75, and 40% of standard error of the measurement results were below 5%, confirming EVA reliability. When fast repertoire was played, increases in odds ratios in short duration cells were seen in 23 of 24 possible instances, and decreases in longer duration cells were seen in 17 instances in all EVA arrays using multinomial logistic regression with random effects, confirming a shift towards shorter duration. A reliable technique to assess right shoulder kinematic and EMG exposure in violinists was identified. PRACTITIONER SUMMARY: A reliable method of measuring right shoulder motion and muscle activity exposure variation in violinists was developed which can be used to assess ergonomic risk in other occupations. Recently developed statistical methods enabled differentiation between fast and slow musical performance of standardised musical repertoire.

Erratum: 404 Mechanisms of a Dynamic Stability Protocol for Persons with Thumb Osteoarthritis - CORRIGENDUM.

[This corrects the article DOI: 10.1017/cts.2024.351.].

The long head of the biceps tendon undergoes multiaxial deformation during shoulder motion.

The long head biceps tendon (LHBT) is presumed a common source of shoulder joint pain and injury. Despite common LHBT pathologies, diagnosis and preferred treatment remain frequently debated. This Short Communication reports the development of a subject-specific finite element model of the shoulder joint based on one subject's 3D reconstructed anatomy and 3D in vivo kinematics recorded from bone-fixed electromagnetic sensors. The primary purpose of this study was to use the developed finite element model to investigate the LHBT mechanical environment during a typical shoulder motion of arm raising. Furthermore, this study aimed to assess the viability of material models derived from uniaxial tensile tests for accurate simulation of in vivo motion. The findings of our simulations indicate that the LHBT undergoes complex multidimensional deformations. As such, uniaxial material properties reported in the existing body of literature are not sufficient to simulate accurately the in vivo mechanical behavior of the LHBT. Further experimental tests on cadaveric specimens, such as biaxial tension and combinations of tension and torsion, are needed to describe fully the mechanical behavior of the LHBT and investigate its mechanisms of injury.

Effects of Scapular Angular Deviations on Potential for Rotator Cuff Tendon Mechanical Compression.

Background: One proposed mechanism of rotator cuff disease is scapular motion impairments contributing to rotator cuff compression and subsequent degeneration. Purpose: To model the effects of scapular angular deviations on rotator cuff tendon proximity for subacromial and internal mechanical impingement risk during scapular plane abduction. Study Design: Descriptive laboratory study. Methods: Three-dimensional bone models were reconstructed from computed tomography scans obtained from 10 asymptomatic subjects and 9 symptomatic subjects with a clinical presentation of impingement syndrome. Models were rotated to average scapular orientations from a healthy dataset at higher (120°) and lower (subject-specific) humeral elevation angles to investigate internal and subacromial impingement risks, respectively. Incremental deviations in scapular upward/downward rotation, internal/external rotation, and anterior/posterior tilt were imposed on the models to simulate scapular movement impairments. The minimum distance between the rotator cuff insertions and potential impinging structures (eg, glenoid, acromion) was calculated. Two-way mixed-model analyses of variance assessed for effects of scapular deviation and group. Results: At 120° of humerothoracic elevation, minimum distances from the supraspinatus and infraspinatus insertions to the glenoid increased with ≥5° changes in upward rotation (1.6-9.8 mm, P < .001) or external rotation (0.9-5.0 mm, P≤ .048), or with ≥10° changes in anterior tilt (1.1-3.2 mm, P < .001). At lower angles, ≥20° changes in most scapular orientations significantly increased the distance between the supraspinatus and infraspinatus insertions and the acromion or coracoacromial ligament. Conclusion: A reduction in scapular upward rotation decreases the distance between the rotator cuff tendon insertions and glenoid at 120° humerothoracic elevation. Interpretation is complicated for lower angles because the humeral elevation angle was defined by the minimum distance. Clinical Relevance: These results may assist clinical decision making regarding the effects of scapular movement deviations in patients with rotator cuff pathology and scapular dyskinesia and may help inform the selection of clinical interventions.

Clinical implications of scapular dyskinesis in shoulder injury: the 2013 consensus statement from the 'Scapular Summit'.

The second international consensus conference on the scapula was held in Lexington Kentucky. The purpose of the conference was to update, present and discuss the accumulated knowledge regarding scapular involvement in various shoulder injuries and highlight the clinical implications for the evaluation and treatment of shoulder injuries. The areas covered included the scapula and shoulder injury, the scapula and sports participation, clinical evaluation and interventions and known outcomes. Major conclusions were (1) scapular dyskinesis is present in a high percentage of most shoulder injuries; (2) the exact role of the dyskinesis in creating or exacerbating shoulder dysfunction is not clearly defined; (3) shoulder impingement symptoms are particularly affected by scapular dyskinesis; (4) scapular dyskinesis is most aptly viewed as a potential impairment to shoulder function; (5) treatment strategies for shoulder injury can be more effectively implemented by evaluation of the dyskinesis; (6) a reliable observational clinical evaluation method for dyskinesis is available and (7) rehabilitation programmes to restore scapular position and motion can be effective within a more comprehensive shoulder rehabilitation programme.

Comparison of rotator cuff to glenoid proximity based on scapulothoracic upward rotation classification.

BACKGROUND: Recent evidence suggests that internal impingement, or rotator cuff tendon deformation against the glenoid, occurs during overhead motions and may therefore be a mechanism of pathology even in non-athletes. Clinically, knowing how movement impacts potential injury mechanisms would be useful to guide movement-based treatment strategies. OBJECTIVE: To compare the distance between the glenoid and rotator cuff footprint between two groups classified based on scapulothoracic upward rotation (UR) magnitude (i.e., low, high) at 90° humerothoracic elevation. METHODS: Shoulder kinematics were quantified during scapular plane abduction in 60 participants using single-plane fluoroscopy. Of these, 40 were subsequently classified as having high or low scapulothoracic UR based on the sample's distribution. The minimum distance between the glenoid and rotator cuff footprint was calculated along with the locations of closest proximity (i.e., proximity centers). Minimum distances and proximity center locations were compared between groups using 2-factor mixed-model ANOVAs. The prevalence of glenoid-to-footprint contact was also compared. RESULTS: Glenoid-to-footprint distances consistently decreased as humerothoracic elevation angle increased, and the anterior aspect of the footprint was closest to the posterosuperior glenoid. Minimum distances were not significantly different between UR groups (p≥0.16). However, group differences existed in proximity center locations (p<0.01). Glenoid-to-footprint contact was identified in 75.0% of participants at an average (SD) of 133.6° (3.2°) humerothoracic elevation. CONCLUSION: The results of this study suggest that decreased UR as classified and assessed in this study does not significantly impact glenoid-to-footprint distances but does alter the location of the contact, which occurred in most participants.

Effect of shoulder pain on shoulder kinematics during weight-bearing tasks in persons with spinal cord injury.

OBJECTIVE: To assess 3-dimensional scapulothoracic and glenohumeral kinematics between subjects with spinal cord injury and disease (SCI/D) with and without shoulder pain during a weight-relief raise and transfer task. DESIGN: Case-control, repeated-measures analysis of variance. SETTING: Movement analysis laboratory. PARTICIPANTS: Subjects (N=43; 23 with clinical signs of impingement and 20 without) between 21 and 65 years of age, at least 1 year after SCI/D (range, 1-43y) resulting in American Spinal Injury Association Impairment Scale T2 motor neurologic level or below, and requiring the full-time use of a manual wheelchair. INTERVENTIONS: Weight-relief raises and transfer tasks. MAIN OUTCOME MEASURES: An electromagnetic tracking system acquired 3-dimensional position and orientation of the thorax, scapula, and humerus. Dependent variables included angular values for scapular upward and downward rotation, posterior and anterior tilt, and internal and external rotation relative to the thorax, and glenohumeral internal and external rotation relative to the scapula. The mean of 3 trials was collected, and angular values were compared at 3 distinct phases of the weight-relief raise and transfer activity. Comparisons were also made between transfer direction (lead vs trail arm) and across groups. RESULTS: Key findings include significantly increased scapular upward rotation for the pain group during transfer (P=.03). Significant group differences were found for the trailing arm at the lift pivot (phase 2) of the transfer, with the pain group having greater anterior tilt (mean difference ± SE, 5.7°±2.8°). The direction of transfer also influenced kinematics at the different phases of the activity. CONCLUSIONS: Potentially detrimental magnitude and direction of scapular and glenohumeral kinematics during weight-bearing tasks may pose increased risk for shoulder pain or injury in persons with SCI/D. Consideration should be given to rehabilitation strategies that promote favorable scapular kinematics and glenohumeral external rotation.

To what extent do typical components of shoulder clinical evaluation explain upper-extremity disability? A cross-sectional study.

BACKGROUND: Physical therapists use several evaluation measures to identify the most important factors related to disability. However, the degree to which these evaluation components explain shoulder disability is not well known and that may detract clinicians from the best clinical reasoning. OBJECTIVE: To determine how much evaluation components explain shoulder function. METHODS: Eighty-one individuals with unilateral shoulder pain for at least four weeks and meeting clinical exam criteria to exclude cervical referred pain, adhesive capsulitis, and shoulder instability, participated in this study. Several typical clinical evaluation components were assessed as potential independent variables in a regression model using the Disabilities of the Arm, Shoulder, and Hand (DASH) score as a proxy to shoulder function. Two multivariate models were built to include (1) evaluation components from physical exam plus clinical history and (2) a model considering all previous variables and magnetic resonance imaging (MRI) data. RESULTS: Pain catastrophizing was the best variable in the model explaining at least 10% of the DASH variance. Sex and lower trapezius muscle strength explained considerably less of shoulder function. The MRI data did not improve the model performance. CONCLUSION: The complexity of shoulder function is not independently explained by pathoanatomical abnormalities. Psychological aspects may explain more of shoulder function even when combined with physical components in some patients.

Changing our Diagnostic Paradigm Part II: Movement System Diagnostic Classification.

Diagnostic classification is a foundational underpinning of providing care of the highest quality and value. Diagnosis is pattern recognition that can result in categories of conditions that ideally direct treatment. While pathoanatomic diagnoses are common and traditional in orthopaedic practice, they often are limited with regard to directing best practice physical therapy intervention. Replacement of pathoanatomic labels with non-specific regional pain labels has been proposed, and occurs frequently in clinical practice. For example non-specific low back pain or shoulder pain of unknown origin. These labels avoid some disadvantages of tissue specific pathoanatomic labels, but are not specific enough to direct treatment. A previously introduced movement system diagnostic framework is proposed and updated with application to shoulder conditions. This framework has potential for broad development and application across musculoskeletal physical therapist practice. Movement system diagnostic classification can advance and streamline practice if considered while recognizing the inherent movement variability across individuals.

The effect of tactile and verbal guidance during scapulothoracic exercises: An EMG and kinematic investigation.

BACKGROUND: Clinician-led training through tactile and verbal guidance to improve muscle activity and joint motion are a common but understudied focus of therapeutic interventions for shoulder pain. The purpose of this study was to determine if clinician guidance changes scapulothoracic muscle activity and kinematics compared to unguided shoulder exercises. METHODS: Eleven participants with shoulder pain were studied. Electromyographic (EMG) sensors were placed on the serratus anterior and upper and lower trapezii. Scapulothoracic and sternoclavicular kinematics were collected using electromagnetic sensors. Five common resisted shoulder exercises were performed with the following guidance: unguided, combined (verbal and tactile cues), and verbal guidance only. One-way repeated measures ANOVAs determined the effect of guidance versus unguided conditions for each exercise. RESULTS: Nine of ten combinations of exercise and guidance techniques demonstrated a significant effect of guidance for either muscle activity or joint kinematics. The guidance condition with the most frequent significant improvements across all variables was the combined condition. The exercises with the most frequent significant improvements across all variables were the external rotation exercises. Variables improved most frequently were: upper:lower trapezius EMG ratio (up to 11%), sternoclavicular elevation (up to 6°) and scapulothoracic internal rotation positioning (up to 8°), and sternoclavicular retraction displacement (up to 5°). CONCLUSION: Shoulder muscle activity and kinematics during exercises can be modified by tactile and verbal guidance. Most improvements in muscle activity occurred with verbal guidance during external rotation exercises. Most improvements in joint positioning and movement occurred with combined guidance during external rotation exercises.

Kinematics and biomechanical validity of shoulder joint laxity tests as diagnostic criteria in multidirectional instability.

BACKGROUND: Clinical laxity tests are commonly used together to identify individuals with multidirectional instability (MDI). However, their biomechanical validity in distinguishing distinct biomechanical characteristics consistent with MDI has not been demonstrated. OBJECTIVE: To determine if differences in glenohumeral (GH) joint laxity exist between individuals diagnosed with multidirectional instability (MDI) and asymptomatic matched controls without MDI. METHODS: Eighteen participants (9 swimmers with MDI, 9 non-swimming asymptomatic matched controls without MDI) participated in this observational study. Participants were classified as having MDI with a composite laxity score from three laxity tests (anterior/posterior drawer and sulcus tests). Single plane dynamic fluoroscopy captured joint motion with 2D-3D joint registration to derive 3D joint kinematics. Average GH translations occurring during the laxity tests were compared between groups using an independent sample's t-test. The relationship of composite laxity scores to overall translations was examined with a simple linear regression. Differences of each laxity test translation between groups were analyzed with a two-way repeated measures ANOVA. RESULTS: Mean composite translations for swimmers were 1.7 mm greater (p = 0.04, 95% Confidence Interval (CI): 0.1, 3.3 mm) compared to controls. A moderate association occurred (r2 = 0.40, p = 0.005) between composite laxity scores and composite translation. Greater translations for the posterior drawer (-2.4 mm, p = 0.04, 95% CI: -0.1, -4.6) and sulcus tests (-2.7 mm, p = 0.03, 95% CI: -0.3, -5.0) existed in swimmers compared to controls. CONCLUSION: Significant differences in composite translation existed between symptomatic swimmers with MDI and asymptomatic control participants without MDI during GH joint laxity tests. The results provide initial biomechanically based construct validity for the clinical criteria used to identify individuals with MDI.

Supraspinatus-to-Glenoid Contact Occurs During Standardized Overhead Reaching Motion.

BACKGROUND: Rotator cuff tears may result from repeated mechanical deformation of the cuff tendons, and internal impingement of the supraspinatus tendon against the glenoid is one such proposed mechanism of deformation. PURPOSE: To (1) describe the changing proximity of the supraspinatus tendon to the glenoid during a simulated overhead reaching task and (2) determine the relationship between scapular morphology and this proximity. Additionally, the patterns of supraspinatus-to-glenoid proximity were compared with previously described patterns of supraspinatus-to-coracoacromial arch proximity. STUDY DESIGN: Descriptive laboratory study. METHODS: Shoulder models were created from magnetic resonance images of 20 participants. Standardized kinematics were imposed on the models to simulate functional reaching, and the minimum distances between the supraspinatus tendon and the glenoid and the supraspinatus footprint and the glenoid were calculated every 5° between 0° and 150° of humerothoracic elevation. The angle at which contact between the supraspinatus and the glenoid occurred was documented. Additionally, the relationship between glenoid morphology (version and inclination) and the contact angle was evaluated. Descriptive statistics were calculated for the minimum distances, and glenoid morphology was assessed using Pearson correlation coefficients and simple linear regressions. RESULTS: The minimum distances between the tendon and the glenoid and between the footprint and the glenoid decreased as elevation increased. Contact between the tendon and the glenoid occurred in all participant models at a mean elevation of 123° ± 10°. Contact between the footprint and the glenoid occurred in 13 of 20 models at a mean of 139° ± 10°. Less glenoid retroversion was associated with lower tendon-to-glenoid contact angles (r = -0.76; R 2 = 0.58; P < .01). CONCLUSION: This study found that the supraspinatus tendon progressively approximated the glenoid during simulated overhead reaching. Additionally, all participant models eventually made contact with the glenoid by 150° of humerothoracic elevation, although anatomic factors influenced the precise angle at which contact occurred. CLINICAL RELEVANCE: Contact between the supraspinatus and the glenoid may occur frequently within the range of elevation required for overhead activities. Therefore, internal impingement may be a prevalent mechanism for rotator cuff deformation that could contribute to cuff pathology.

Three-dimensional in vivo kinematics of an osteoarthritic shoulder before and after total shoulder arthroplasty.

A case of a patient with glenohumeral joint arthritis is presented which demonstrated the three-dimensional shoulder motion before and after total shoulder arthroplasty. Pre-operative shoulder motion differed compared to normal controls, while post-operatively her glenohumeral-to-scapulothoracic motion ratios were restored to near normal ratios.

Shoulder kinematics during the wall push-up plus exercise.

BACKGROUND AND HYPOTHESIS: The push-up plus exercise is a common therapeutic exercise for improving shoulder function and treating shoulder pathology. To date, the kinematics of the push-up plus exercise have not been studied. Our hypothesis was that the wall push-up plus exercise would demonstrate increased scapular internal rotation and increased humeral anterior translation during the plus phase of the exercise, thereby potentially impacting the subacromial space. METHODS: Bone pins were inserted in the humerus and scapula in 12 healthy volunteers with no history of shoulder pathology. In vivo motion during the wall push-up plus exercise was tracked using an electromagnetic tracking system. RESULTS: During the wall push-up plus exercise, from a starting position to the push-up plus position, there was a significant increase in scapular downward rotation (P < .05) and internal rotation (P < .05). The pattern of glenohumeral motion was humeral elevation (P < .05) and movement anterior to the scapular plane (P < .05), with humeral external rotation remaining relatively constant. CONCLUSION: We found that during a wall push-up plus exercise in healthy volunteers, the scapula was placed in a position potentially associated with shoulder impingement. Because of the shoulder kinematics of the wall push-up plus exercise, utilization of this exercise without modification early on in shoulder rehabilitation, especially in patients with subacromial impingement, should be considered cautiously.

Shoulder kinematics impact subacromial proximities: a review of the literature.

BACKGROUND: Alterations in glenohumeral and scapulothoracic kinematics have been theorized to contribute to rotator cuff pathology by impacting the magnitude of the subacromial space. OBJECTIVE: The purpose of this review is to summarize what is currently known about the relationship between shoulder kinematics and subacromial proximities. CONCLUSIONS: A variety of methods have been used to quantify subacromial proximities including photographs, MR imaging, ultrasonography, and single- and bi-plane radiographs. Changes in glenohumeral and scapulothoracic kinematics are associated with changes in subacromial proximities. However, the magnitude and direction of a particular motion's impact on subacromial proximities often vary between studies, which likely reflects different methodologies and subject populations. Glenohumeral elevation angle has been consistently found to impact subacromial proximities. Plane of humeral elevation also impacts subacromial proximities but to a lesser degree than the elevation angle. The impact of decreased scapulothoracic upward rotation on subacromial proximities is not absolute, but instead depends on the angle of humerothoracic elevation. The effects of scapular dyskinesis and humeral and scapular axial rotations on subacromial proximities are less clear. Future research is needed to further investigate the relationship between kinematics and subacromial proximities using more homogenous groups, determine the extent to which compression and other factors contribute to rotator cuff pathology, and develop accurate and reliable clinical measures of shoulder motion.