Paula M. Ludewig

The Association of Scapular Kinematics and Glenohumeral Joint Pathologies

UNLABELLED There is a growing body of literature associating abnormal scapular positions and motions, and, to a lesser degree, clavicular kinematics with a variety of shoulder pathologies. The purpose of this manuscript is to (1) review the normal kinematics of the scapula and clavicle during arm elevation, (2) review the evidence for abnormal scapular and clavicular kinematics in glenohumeral joint pathologies, (3) review potential biomechanical implications and mechanisms of these kinematic alterations, and (4) relate these biomechanical factors to considerations in the patient management process for these disorders. There is evidence of scapular kinematic alterations associated with shoulder impingement, rotator cuff tendinopathy, rotator cuff tears, glenohumeral instability, adhesive capsulitis, and stiff shoulders. There is also evidence for altered muscle activation in these patient populations, particularly, reduced serratus anterior and increased upper trapezius activation. Scapular kinematic alterations similar to those found in patient populations have been identified in subjects with a short rest length of the pectoralis minor, tight soft-tissue structures in the posterior shoulder region, excessive thoracic kyphosis, or with flexed thoracic postures. This suggests that attention to these factors is warranted in the clinical evaluation and treatment of these patients. The available evidence in clinical trials supports the use of therapeutic exercise in rehabilitating these patients, while further gains in effectiveness should continue to be pursued. LEVEL OF EVIDENCE Level 5.

Motion of the Shoulder Complex During Multiplanar Humeral Elevation

BACKGROUND Many prior studies have evaluated shoulder motion, yet no three-dimensional analysis comparing the combined clavicular, scapular, and humeral motion during arm elevation has been done. We aimed to describe and compare dynamic three-dimensional motion of the shoulder complex during raising and lowering the arm across three distinct elevation planes (flexion, scapular plane abduction, and coronal plane abduction). METHODS Twelve subjects without a shoulder abnormality were enrolled. Transcortical pin placement into the clavicle, scapula, and humerus allowed electromagnetic motion sensors to be rigidly fixed. The subjects completed two repetitions of raising and lowering the arm in flexion, scapular, and abduction planes. Three-dimensional angles were calculated for sternoclavicular, acromioclavicular, scapulothoracic, and glenohumeral joint motions. Joint angles between humeral elevation planes and between raising and lowering of the arm were compared. RESULTS General patterns of shoulder motion observed during humeral elevation were clavicular elevation, retraction, and posterior axial rotation; scapular internal rotation, upward rotation, and posterior tilting relative to the clavicle; and glenohumeral elevation and external rotation. Clavicular posterior rotation predominated at the sternoclavicular joint (average, 31 degrees). Scapular posterior tilting predominated at the acromioclavicular joint (average, 19 degrees). Differences between flexion and abduction planes of humerothoracic elevation were largest for the glenohumeral joint plane of elevation (average, 46 degrees). CONCLUSIONS Overall shoulder motion consists of substantial angular rotations at each of the four shoulder joints, enabling the multiple-joint interaction required to elevate the arm overhead.

Relative Balance of Serratus Anterior and Upper Trapezius Muscle Activity During Push-Up Exercises

Background Serratus anterior strengthening is used in prevention and treatment programs for poor scapular control. In certain clinical cases, exercises substantially activating the serratus with minimal upper trapezius activation are preferred. Hypothesis The standard push-up plus would show both the highest serratus anterior activation and lowest upper trapezius/ serratus ratios for both groups and all phases. Study Design Controlled laboratory study. Methods Thirty subjects, grouped as healthy or with mild shoulder dysfunction, were evaluated performing standard push-up plus exercises and modifications on elbows, knees, and against a wall. Surface electromyography of the serratus anterior and upper trapezius was compared between exercises. Results Both groups responded similarly across exercises. The standard push-up plus demonstrated the highest activation of the serratus (to 123%) and lowest trapezius/serratus ratios (< 0.2) during plus phases. The wall push-up plus and phases of other exercises demonstrated higher upper trapezius/serratus ratios (to 2.0). Conclusions In clinical cases where excess upper trapezius activation or imbalance of serratus and trapezius activation occurs, the push-up plus is an optimal exercise. Other cases may benefit from a progression of modified push-up exercises. Clinical Relevance Clinical selection of exercises for improving scapular control should consider both maximum serratus activation and upper trapezius/serratus anterior ratios.

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 scapular kinematics between elevation and lowering of the arm in the scapular plane

OBJECTIVE To compare scapular orientation during both the concentric (elevation) and eccentric (lowering) phases of scapular plane abduction in subjects with and without shoulder impingement. DESIGN Mixed model analysis of variance with one between-subjects factor (group) and within-subjects factors of phase, humeral angle, and trial. BACKGROUND Abnormal scapular kinematics have been identified in shoulder impingement patients during the concentric phase of arm elevation, and under static conditions. Because abnormal scapular motion is observed clinically during the eccentric phase of arm elevation, analysis of this phase of motion is warranted. METHODS Twenty-six symptomatic and 26 healthy subjects performed five repetitions of humeral scapular plane abduction. An electromagnetic tracking device described three-dimensional scapular kinematics during arm elevation and lowering. Angular values for scapular anterior/posterior tipping in the sagittal plane, upward/downward rotation in the scapular plane, and internal/external rotation in the transverse plane were calculated. Scapular orientation relative to the thorax at humeral angles of 40 degrees, 60 degrees, 80 degrees, 100 degrees, and 120 degrees was statistically tested for effects of phase and trial, or for interactions of phase with group or humeral angle. RESULTS Internal rotation was significantly increased in the eccentric phase for both groups at the 100 degrees angle (P<0.05) and for the symptomatic group only at the 120 degrees angle (P<0.05). Scapular anterior tipping was significantly decreased during the eccentric phase in both groups at the 80 degrees (P<0.001), 100 degrees (P<0.0001), and 120 degrees (P<0.0001) angles. CONCLUSIONS Small but statistically significant differences in scapular tipping and internal rotation during the eccentric phase of arm elevation were identified at higher humeral angles in both subject groups, while no significant phase differences for scapular upward rotation or for scapular variables at lower humeral angles were found. Averaged across phases, the symptomatic group demonstrated significant reductions in upward rotation at lower humeral elevation angles, and significant increases in anterior tipping at higher elevation angles as compared to the healthy group. RELEVANCE Normal and abnormal scapular kinematics during varying types of motion need to be understood in order to optimally design rehabilitation programs for individuals with impingement syndrome.

Scapular and rotator cuff muscle activity during arm elevation: a review of normal function and alterations with shoulder impingement

OBJECTIVE: The purpose of this manuscript is to review current knowledge of how muscle activation and force production contribute to shoulder kinematics in healthy subjects and persons with shoulder impingement. RESULTS: The middle and lower serratus anterior muscles produce scapular upward rotation, posterior tilting, and external rotation. Upper trapezius produces clavicular elevation and retraction. The middle trapezius is primarily a medial stabilizer of the scapula. The lower trapezius assists in medial stabilization and upward rotation of the scapula. The pectoralis minor is aligned to resist normal rotations of the scapula during arm elevation. The rotator cuff is critical to stabilization and prevention of excess superior translation of the humeral head, as well as production of glenohumeral external rotation during arm elevation. Alterations in activation amplitude or timing have been identified across various investigations of subjects with shoulder impingement as compared to healthy controls. These include decreased activation of the middle or lower serratus anterior and rotator cuff, delayed activation of middle and lower trapezius, and increased activation of the upper trapezius and middle deltoid in impingement subjects. In addition, subjects with a short resting length of the pectoralis minor exhibit altered scapular kinematic patterns similar to those found in persons with shoulder impingement. CONCLUSION: These normal muscle functional capabilities and alterations in patient populations should be considered when planning exercise approaches for the rehabilitation of these patients.

Differences in 3-Dimensional Shoulder Kinematics Between Persons With Multidirectional Instability and Asymptomatic Controls

Background Evidence that persons with multidirectional instability (MDI) of the shoulder have abnormal shoulder kinematics is limited. A kinematic description of scapulothoracic and glenohumeral motion can assist both conservative and surgical rehabilitative programs. Hypothesis Persons with MDI of the shoulder demonstrate increased anterior and inferior glenohumeral translation and decreased scapular upward rotation and increased scapular internal rotation compared with age-matched and gender-matched asymptomatic controls. Study Design Controlled laboratory study. Methods Sixty-two subjects were recruited from an outpatient orthopaedic clinic. Subjects with MDI were matched according to age, gender, and hand dominance to asymptomatic controls. An electromagnetic motion capture system evaluated the 3-dimensional position of the trunk, scapula, and humerus during frontal and scapular plane elevation. A repeated measures analysis of variance evaluated joint positions and glenohumeral translations during 4 phases of elevation (0°-30°, 31°-60°, 61°-90°, and 91°-120°). Results When averaged across the 4 phases of elevation, persons with MDI demonstrated a significant decrease in scapular upward rotation in scapular plane abduction (8°, P = .006) and abduction (5.8°, P = .016) and increased internal rotation during scapular plane abduction (12.2°, P = .03). Alterations in glenohumeral translations in the MDI group did not reach statistical significance (P = .54-.71). Conclusion Abnormal scapular kinematics are seen in the MDI shoulder, highlighting the importance of incorporating scapular positioning and stability exercises during rehabilitation. Additional study is warranted concerning the efficacy of various rehabilitation programs, and also both surgical and nonsurgical interventions in this population.

Shoulder impingement: biomechanical considerations in rehabilitation.

Shoulder impingement is a common condition presumed to contribute to rotator cuff disease. Impingement can occur externally with the coracoacromial arch or internally with the glenoid rim. Normal scapulothoracic motions that occur during arm elevation include upward rotation, posterior tilting, and either internal or external rotation. These scapulothoracic motions and positions are the result of coupled interactions between sternoclavicular and acromioclavicular joints. The sternoclavicular and acromioclavicular joints both contribute to scapulothoracic upward rotation. Posterior tilting is primarily an acromioclavicular joint motion. The sternoclavicular and acromioclavicular joint motions offset one another regarding final scapulothoracic internal/external rotation position. This manuscript discusses these coupled interactions in relation to shoulder muscle function. Two case examples are presented to demonstrate application of understanding these interactions and potential mechanisms of movement abnormalities in targeting treatment interventions for movement based subgroups of impingement patients.

Three-Dimensional Acromioclavicular Joint Motions During Elevation of the Arm

STUDY DESIGN Descriptive laboratory study. OBJECTIVES To determine the 3-dimensional motions occurring between the scapula relative to the clavicle at the acromioclavicular joint during humeral elevation in the scapular plane. BACKGROUND Shoulder pathology is commonly treated through exercise programs aimed at correcting scapular motion abnormalities. However, little is known regarding how acromioclavicular joint motions contribute to normal and abnormal scapulothoracic motion. METHODS AND MEASURES Thirty subjects (16 males, 14 females) participated. Subjects with positive symptoms on clinical exam or past history of shoulder pathology, trauma, or surgery were excluded. Electromagnetic surface motion analysis was performed tracking the thorax, clavicle, scapula, and humerus. Subjects performed 3 repetitions of scapular plane abduction. Passive motion data were also collected for scapular plane abduction from cadaver specimens. Data were analyzed using within-session reliability and descriptive statistics as well as repeated measures analyses of variance (ANOVAs) to determine the effect of elevation angle from rest to 90 masculine humeral elevation. Reliability was determined from repeated trials in the same session without removing sensors or redigitizing landmarks. RESULTS Angular values were highly repeatable within session (ICC>0.94; SEM, < 2.3 degrees ). During active scapular plane abduction from rest to 90 degrees , average acromioclavicular joint angular values demonstrated increased internal rotation (approximately 4.3 degrees ), increased upward rotation (approximately 14.6 degrees ), and increased posterior tilting (approximately 6.7 degrees ) (P<.05). Passive motions on cadavers demonstrated similar kinematic patterns. CONCLUSIONS Significant motion occurs at the acromioclavicular joint during active humeral elevation, contributing to scapular motion on the thorax. This information provides a foundation for understanding normal acromioclavicular joint motion as a basis for further investigation of pathology and rehabilitation approaches.

Clinical trial of exercise for shoulder pain in chronic spinal injury.

Background and Purpose. The high prevalence of shoulder pain in wheelchair users may be related to the repetitive use of the upper limbs during self-care and wheelchair-related activities. The purpose of this study was to determine the effects of a controlled 8-week, scapula-focused exercise intervention on pain and functional disability in people with spinal cord injury (SCI) and shoulder impingement symptoms. Subjects. Forty-one manual wheelchair users (with SCI and spina bifida), both with (n=21) and without (n=20) shoulder impingement symptoms, participated. Methods. The study design was a clinical trial with an asymptomatic control group. Subjects completed the Wheelchair User’s Shoulder Pain Index (WUSPI) and the Shoulder Rating Questionnaire (SRQ) and provided patient satisfaction scores at initial and 8-week visits. Subjects in the intervention group were instructed in a home exercise program consisting of stretching and strengthening exercises. Subjects in the asymptomatic control group received no intervention. An analysis of variance model was used to test for group and time effects for the WUSPI, SRQ, and satisfaction scores. Results. Subjects in the intervention group showed significant improvements in all measures as a result of the intervention, whereas asymptomatic control group subjects remained stable. Discussion and Conclusion. A selective 8-week home exercise program is effective in reducing pain and improving function and satisfaction in this population of wheelchair users.