Active and passive scapulohumeral movement in healthy persons: a comparison

Three-dimensional in vivo scapular kinematics and scapulohumeral rhythm: a comparison between active and passive motion

BACKGROUND

The aim of this study was to compare the scapular kinematics and scapulohumeral rhythm of healthy participants during arm elevation and lowering and to find the difference between active motion and passive motion of the shoulder.

METHODS

The study examined the shoulders of 10 healthy men (mean age, 23.5 years; age range, 22-28 years). The shoulders of participants were elevated and lowered while fluoroscopic images were taken, and 3-dimensional bone models were created from 2-dimensional to 3-dimensional images using model registration techniques. The Euler angle sequences of the models' scapular kinematics and scapulohumeral rhythm were compared during active and passive shoulder motion.

RESULTS

There was a significant statistical difference of upward rotation during arm elevation between active and passive shoulder movements (P = .027). In particular, the upward rotation between 45° and 90° of elevation showed a statistically significant difference (P < .001). When the scapula was tilted posteriorly by active motion, it resulted in a statistically significant difference as there was more tilting in the high-degree range of motions than when it was tilted by passive motion (P < .001). There was no statistically significant difference between the 2 groups in scapular external rotation. However, during arm lowering, scapular kinematics did not show statistically significant difference between active and passive motion.

CONCLUSIONS

The scapular kinematics showed statistically significant differences between active and passive motion of upward rotation and posterior tilting of the scapula during arm elevation, but there were none during lowering. In terms of upward rotation, active shoulders rotated more upward during arm elevation.

Scapular Upward Rotation During Passive Humeral Abduction in Individuals With Hemiplegia Post-stroke

Objective

To describe scapular upward rotation during passive humeral abduction in individuals with hemiplegia post-stroke compared to normal subjects.

Methods

Twenty-five individuals with hemiplegia post-stroke and 25 age- and gender-matched normal subjects voluntarily participated in this study. Scapular upward rotation during resting and passive humeral abduction at 30°, 60°, 90°, 120°, and 150° were measured using a digital inclinometer.

Results

In both groups, scapular upward rotation significantly increased as humeral abduction increased (p<0.001). Scapular upward rotation was significantly less in the hemiplegic group compared to that in the control at 90° (p=0.002), 120° (p<0.001), and 150° of humeral abduction (p<0.001). The mean difference in scapular upward rotation between these two groups ranged from 6.3° to 11.38°.

Conclusion

Passive humeral abductions ranging from 90° to 150° can significantly alter scapular upward rotation in individuals with hemiplegia post-stroke compared to those of matched normal subjects. The magnitude of reduction of the scapular upward rotation may potentially lead to the development of hemiplegic shoulder pain after prolonged repetitive passive movement. Scapular upward rotation should be incorporated during passive humeral abduction in individuals with hemiplegia post-stroke, especially when the humeral is moved beyond 90° of humeral abduction. Combined movements of scapular and humeral will help maintain the relative movement between the scapula and humerus. However, further longitudinal study in patients with shoulder pain post-stroke is needed to confirm these findings.

Analysis of scapular kinematics during active and passive arm elevation

[Purpose] Early postoperative passive motion exercise after arthroscopic rotator cuff repair remains controversial. To better understand this issue, this study was aimed at evaluating scapular kinematics and muscle activities during passive arm elevation in healthy subjects. [Subjects and Methods] The dominant shoulders of 27 healthy subjects were examined. Electromagnetic sensors attached to the scapula, thorax, and humerus were used to determine three-dimensional scapular kinematics during active arm elevation with or without external loads and passive arm elevation. Simultaneously, the activities of seven shoulder muscles were recorded with surface and intramuscular fine-wire electrodes. [Results] Compared with active arm elevation, passive elevation between 30° and 100° significantly decreased the scapular upward rotation and increased the glenohumeral elevation angle. However, no significant differences in scapular posterior tilt and external rotation were observed between active and passive arm elevation, and scapular plane kinematics were not affected by muscle activity. [Conclusion] Unlike active motion with or without an external load, passive arm elevation significantly decreased the scapular upward rotation and significantly increased the mid-range glenohumeral elevation. These data, which suggest that passive arm elevation should be avoided during the early postoperative period, may expand the understanding of rehabilitation after arthroscopic rotator cuff repair.

3D shoulder kinematics for static vs dynamic and passive vs active testing conditions

Shoulder motion analysis provides clinicians with references of normal joint rotations. Shoulder joints orientations assessment is often based on series of static positions, while clinicians perform either passive or active tests and exercises mostly in dynamic. These conditions of motion could modify joint coordination and lead to discrepancies with the established references. Hence, the objective was to evaluate the influence of static vs dynamic and passive vs active testing conditions on shoulder joints orientations. Twenty asymptomatic subjects setup with 45 markers on the upper limb and trunk were tracked by an optoelectronic system. Static positions (30°, 60°, 90° and 120° of thoracohumeral elevation) and dynamic motion both in active condition and passively mobilised by an examiner were executed. Three-dimensional sternoclavicular, acromioclavicular, scapulothoracic and glenohumeral joint angles (12 in total) representing the distal segment orientation relative to the proximal segment orientation were estimated using a shoulder kinematical chain model. Separate four-way repeated measures ANOVA were applied on the 12 joint angles with factors of static vs dynamic, passive vs active, thoracohumeral elevation angle (30°, 60°, 90° and 120°) and plane of elevation (frontal and sagittal). Scapulothoracic lateral rotation progressed more during arm elevation in static than in dynamic gaining 4.2° more, and also in passive than in active by 6.6°. Glenohumeral elevation increased more during arm elevation in active than in passive by 4.4°. Shoulder joints orientations are affected by the testing conditions, which should be taken into consideration for data acquisition, inter-study comparison or clinical applications.

Effects of sex differences on scapular motion during arm elevation

INTRODUCTION

Scapular motion during arm elevation is frequently evaluated in patients with shoulder disorders because it provides clinically useful information. With the development of measurement devices and improvement in accuracy, comparisons under various conditions have recently been reported. However, in most of these reports, the subjects examined were limited to males, or a mixed population of males and females. Only a few reports have described sex differences. In the current study, we performed three-dimensional dynamic analysis of arm elevation and investigated whether there is a sex difference in scapular motion.

METHODS

Subjects included 18 healthy adult males (18 shoulders) and 19 healthy adult females (19 shoulders). Thirty-seven shoulders were on the dominant side. The age range was 20.5 ± 0.03 years. Subjects performed scapular plane arm elevation, and kinematic data were recorded using an electromagnetic tracking device. Scapular upward rotation and internal rotation angles and the posterior tilt angle accompanying arm elevation were calculated from recorded data. Changes in each angle during scapular motion were recorded according to sex.

RESULTS

There were sex differences in scapular upward rotation and internal rotation angles. The upward rotation angle was significantly greater in males, whereas the internal rotation angle was significantly greater in females. No sex differences were noted in the scapular posterior tilt angle.

DISCUSSION

Findings of this study may serve as basic data for scapular motion during scapular plane elevation in healthy males and females. In addition, it is necessary to evaluate and treat the shoulder while taking sex differences in scapular movement into consideration.

Gender effect on the scapular 3D posture and kinematic in healthy subjects

Populations considered for shoulder analysis are often composed of various ratios of men and women. It is consequently hypothesized that gender has no significant effect on the joint kinematic. However, the literature reports, for the shoulder, differences in the range of motion between genders. The specific influence of gender on the scapulo-thoracic kinematics has not been studied yet. The dominant shoulder of two populations of men and women composed of 11 subjects each were evaluated in three dimensions for three distinct motions: flexion in the sagittal plane, abduction in the frontal plane and gleno-humeral internal/external rotation with the arm abducted at 90°. Posture, kinematics and range of motion were studied separately. For flexion and abduction and with regard to the scapular kinematic, external rotation was significantly larger for women than men. The differences were of at least 5° at 120° of humeral elevation. Upward rotations were identical. Women also showed larger average active humero-thoracic range of motion. The mean differences were of 13°, 7°, 12° and 5° for abduction, flexion, internal rotation and external rotation, respectively. No difference was observed between the scapular resting positions of both populations. The observed differences concerning both the scapular and humeral patterns would indicate that the shoulder behaviour of men and women should not be expected to be similar.

Assessment of cognitive engagement in stroke patients from single-trial EEG during motor rehabilitation

We propose a novel method for monitoring cognitive engagement in stroke patients during motor rehabilitation. Active engagement reflects implicit motivation and can enhance motor recovery. In this study, we used electroencephalography (EEG) to assess cognitive engagement in 11 chronic stroke patients while they executed active and passive motor tasks involving grasping and supination hand movements. We observed that the active motor task induced larger event-related desynchronization (ERD) than the passive task in the bilateral motor cortex and supplementary motor area (SMA). ERD differences between tasks were observed during both initial and post-movement periods . Additionally, differences in beta band activity were larger than differences in mu band activity . EEG data was used to help classify each trial as involving the active or passive motor task. Average classification accuracy was 80.7 ±0.1% for grasping movement and 82.8 ±0.1% for supination movement. Classification accuracy using a combination of movement and post-movement periods was higher than in other cases . Our results support using EEG to assess cognitive engagement in stroke patients during motor rehabilitation.

Dominance effect on scapula 3-dimensional posture and kinematics in healthy male and female populations

BACKGROUND

The contralateral shoulder is often used as a reference when evaluating a pathologic shoulder. However, the literature provides contradictory results regarding the symmetry of the scapular pattern in a healthy population. We assume that several factors including gender and type of motion may influence the bilateral symmetry of the scapulae.

MATERIALS AND METHODS

The dominant and nondominant shoulders of 2 populations of men and women comprising 11 subjects each were evaluated for 3 distinct motions: flexion in the sagittal plane, abduction in the frontal plane, and glenohumeral internal/external rotation with the arm abducted at 90°. Posture, kinematics, and range of motion were studied separately.

RESULTS

Asymmetries are observed for motions performed in the frontal and sagittal plane but not for internal/external rotation with the arm abducted at 90°. For both male and female populations, multiplanar asymmetries are observed and the dominant scapula has a larger upward rotation. The asymmetries mainly originate in the scapula's kinematics and not in its original posture.

CONCLUSION

Small but significant asymmetries exist between the dominant and nondominant shoulders in terms of kinematics. One should be aware of these differences when using the contralateral shoulder as a reference.

LEVEL OF EVIDENCE

Basic science study, kinematics

The function of the clavicle on scapular motion: a cadaveric study

HYPOTHESIS

The clavicle serves as a strut between the thorax and scapula, and lack of this function could affect shoulder mobility. We hypothesized that clavicular discontinuity changes shoulder kinematics, particularly affecting scapular motion.

MATERIALS AND METHODS

The study used 14 cadaveric shoulders. Cadavers were stabilized in the sitting position. Manual elevation in the sagittal, scapular, and coronal planes was performed in the intact and clavicular discontinuity models. The thorax-scapula distance and 3-dimensional scapular motion during shoulder elevation were recorded using an electromagnetic tracking device. The differences between the 2 experimental models at each position were analyzed.

RESULTS

Clavicular discontinuity resulted in a decreased thorax-scapula distance and in reduced external rotation, upward rotation, and posterior tilting of the scapula. The kinematic changes were observed during elevations in all 3 planes but were greatest in the sagittal plane compared with the scapular and coronal planes.

CONCLUSIONS

The findings of this study revealed that discontinuity of the clavicle affects shoulder kinematics. Because of its anatomic shape and position, the clavicle stabilizes the external, upward, and posterior rotation of the scapula during arm movement. This function of the clavicle may assist glenohumeral joint motion and help prevent subacromial impingement.

LEVEL OF EVIDENCE

Basic Science Study, Biomechanics, Cadaver Model.

A comparison of 3D scapular kinematics between dominant and nondominant shoulders during multiplanar arm motion

BACKGROUND

Generally, the scapular motions of pathologic and contralateral normal shoulders are compared to characterize shoulder disorders. However, the symmetry of scapular motion of normal shoulders remains undetermined. Therefore, the aim of this study was to compare 3dimensinal (3D) scapular motion between dominant and nondominant shoulders during three different planes of arm motion by using an optical tracking system.

MATERIALS AND METHODS

Twenty healthy subjects completed five repetitions of elevation and lowering in sagittal plane flexion, scapular plane abduction, and coronal plane abduction. The 3D scapular motion was measured using an optical tracking system, after minimizing reflective marker skin slippage using ultrasonography. The dynamic 3D motion of the scapula of dominant and nondominant shoulders, and the scapulohumeral rhythm (SHR) were analyzed at each 10° increment during the three planes of arm motion.

RESULTS

There was no significant difference in upward rotation or internal rotation (P > 0.05) of the scapula between dominant and nondominant shoulders during the three planes of arm motion. However, there was a significant difference in posterior tilting (P = 0.018) during coronal plane abduction. The SHR was a large positive or negative number in the initial phase of sagittal plane flexion and scapular plane abduction. However, the SHR was a small positive or negative number in the initial phase of coronal plane abduction.

CONCLUSIONS

Only posterior tilting of the scapula during coronal plane abduction was asymmetrical in our healthy subjects, and depending on the plane of arm motion, the pattern of the SHR differed as well. These differences should be considered in the clinical assessment of shoulder pathology.

Pelvifemoral Kinematics while Ascending Single Steps of Different Heights

Motion of the femur and pelvis during hip flexion has been examined previously, but principally in the sagittal plane and during nonfunctional activities. In this study we examined femoral elevation in the sagittal plane and pelvic rotation in the sagittal and frontal planes while subjects flexed their hips to ascend single steps. Fourteen subjects ascended single steps of 4 different heights leading with each lower limb. Motion of the lead femur and pelvis during the flexion phase of step ascent was tracked using an infrared motion capture system. Depending on step height and lead limb, step ascent involved elevation of the femur (mean 47.2° to 89.6°) and rotation of the pelvis in both the sagittal plane (tilting: mean 2.6° to 9.7°) and frontal plane (listing: mean 4.2° to 11.9°). Along with maximum femoral elevation, maximum pelvic rotation increased significantly (p< .001) with step height. Femoral elevation and pelvic rotation during the flexion phase of step ascent were synergistic (r= .852–.999). Practitioners should consider pelvic rotation in addition to femoral motion when observing individuals’ ascent of steps.

Effect of shortening deformity of the clavicle on scapular kinematics: a cadaveric study

BACKGROUND

In some short malunion cases, midshaft clavicular fractures are reported to result in unsatisfactory clinical outcomes. Shortening deformity of the clavicle could change the anatomical alignment of the shoulder girdle and is surmised to affect shoulder kinematics on arm movements. Nevertheless, no report has ever referred to documented changes.

HYPOTHESIS

Scapular motion will change with clavicular shortening in cadaveric models.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve cadaveric shoulders were used, and sequential clavicular shortening by 0%, 5%, 10%, 15%, and 20% from the original length was simulated in this study. The scapulothoracic motion during passive arm elevation in 3 planes was monitored using an electromagnetic tracking device. Differences in kinematics of the scapula between the 0% shortening models and the other 4 experimental groups were analyzed.

RESULTS

During arm elevation, posterior tilting and external rotation of the scapula significantly decreased with > or = 10% shortening of the clavicle. Decreased posterior tilting was found with a shorter clavicle and at higher positions of arm elevation in all planes and became obvious during coronal plane elevation. Upward rotation of the scapula did not change with shortening at any elevated arm positions.

CONCLUSION

The findings of this study clearly indicated that shortening of the clavicle affects the kinematics in the shoulder girdle.

CLINICAL RELEVANCE

The results of this cadaveric study suggest that clavicular shortening of > or = 10% affects scapular kinematics and might produce clinical symptoms.

Scapular positioning in athlete's shoulder : particularities, clinical measurements and implications

Despite the essential role played by the scapula in shoulder function, current concepts in shoulder training and treatment regularly neglect its contribution. The 'scapular dyskinesis' is an alteration of the normal scapular kinematics as part of scapulohumeral rhythm, which has been shown to be a nonspecific response to a host of proximal and distal shoulder injuries. The dyskinesis can react in many ways with shoulder motion and function to increase the dysfunction. Thoracic kyphosis, acromio-clavicular joint disorders, subacromial or internal impingement, instability or labral pathology can alter scapular kinematics. Indeed, alteration of scapular stabilizing muscle activation, inflexibility of the muscles and capsule-ligamentous complex around the shoulder may affect the resting position and motion of the scapula. Given the interest in the scapular positioning and patterns of motion, this article aims to give a detailed overview of the literature focusing on the role of the scapula within the shoulder complex through the sports context. Such an examination of the role of the scapula requires the description of the normal pattern of scapula motion during shoulder movement; this also implies the study of possible scapular adaptations with sports practice and scapular dyskinesis concomitant to fatigue, impingement and instability. Different methods of scapular positioning evaluation are gathered from the literature in order to offer to the therapist the possibility of detecting scapular asymmetries through clinical examinations. Furthermore, current concepts of rehabilitation dealing with relieving symptoms associated with inflexibility, weakness or activation imbalance of the muscles are described. Repeating clinical assessments throughout the rehabilitation process highlights improvements and allows the therapist to actualize rationally his or her intervention. The return to the field must be accompanied by a transitory phase, which is conducive to integrating new instructions during sports gestures. On the basis of the possible scapular disturbance entailed in sports practice, a preventive approach that could be incorporated into training management is encouraged.

Scapular kinematics during supraspinatus rehabilitation exercise: a comparison of full-can versus empty-can techniques

BACKGROUND

Supraspinatus strengthening is an important component of shoulder rehabilitation. Previous work has determined that the full-can and empty-can exercises elicit the greatest amount of supraspinatus activity. However, scapular kinematics has not been considered when prescribing supraspinatus exercises.

HYPOTHESIS

Scapular downward rotation, internal rotation, and anterior tipping during the empty-can exercise are increased when compared with the full-can exercise.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twenty participants performed full-can and empty-can exercises while an electromagnetic tracking system was used to collect three-dimensional scapular kinematic data. Scapular angles at 30 degrees, 60 degrees, and 90 degrees of the ascending and descending phases of humeral elevation were compared using 2-way repeated measures analysis of variance.

RESULTS

There was more scapular anterior tipping and internal rotation during the empty-can exercise at all sampled humeral elevation angles except at 30 degrees of the descending phase for anterior/posterior tipping (P < .05).

CONCLUSION

Scapular anterior tipping and internal rotation are increased during the empty-can exercise, whereas scapular upward rotation was not different between exercises.

CLINICAL RELEVANCE

Increased scapular internal rotation and anterior tipping decrease the volume of the supraspinatus outlet during the empty-can exercise. When maintenance of the subacromial space is important, use of the full-can exercise seems most appropriate for selective strengthening of the supraspinatus muscle.

Functional activity characteristics of individuals with shoulder dysfunctions

Shoulder-related dysfunction affects individuals' ability to function independently and thus decreases quality of life. Functional task assessment is a key concern for a clinician in diagnostic assessment, outcome measurement, and planning of treatment programs. The purpose of this study was to test the reliability of the FASTRAK 3-dimensional (3-D) motion analysis and surface electromyography (sEMG) systems to analyze 3-D shoulder complex movements during functional tasks and compare motion patterns between subjects with and without shoulder dysfunctions (SDs).For the test, sEMG and 3-D motion analysis systems were used to characterize the functional tasks. Twenty-five asymptomatic male subjects and 21 male subjects with right shoulder disorders performed four functional tasks which involved arm reaching and raising activities with their dominant arms. Reliability was estimated by the intraclass correlation coefficient (ICC). Motion pattern was compared between two groups using mixed analysis of variances (ANOVAs). Shoulder complex kinematics and associated muscular activities during functional tasks were reliably quantified (ICC=0.83-0.99) from the means of three trials. Relative to the group without SDs, the group with SDs showed significant alteration in shoulder complex kinematics (3 degrees -40 degrees ) and associated muscular activities (3-10% maximum). Scapular tipping, scapular elevation, upper trapezius muscle function, and serratus anterior muscle function may have implications in the rehabilitation of patients with SDs.

Three-dimensional scapulothoracic motion during active and passive arm elevation

BACKGROUND

Scapulothoracic muscle activity is believed to be important for normal scapulothoracic motion. In particular, the trapezius and serratus anterior muscles are believed to play an important role in the production and control of scapulothoracic motion. The aim of this study was to determine the effects of different levels of muscle activity (active versus passive arm elevation) on three-dimensional scapulothoracic motion.

METHODS

Twenty subjects without a history of shoulder pathology participated in this study. Three-dimensional scapulothoracic motion was determined from electromagnetic sensors attached to the scapula, thorax and humerus during active and passive arm elevation. Muscle activity was recorded from surface electrodes over the upper and lower trapezius, serratus anterior, anterior and posterior deltoid, and infraspinatus muscles. Differences in scapulothoracic motion were calculated between active and passive arm elevation conditions.

FINDINGS

Scapular motion was observed during the trials of passive arm elevation; however, there was more upward rotation of the scapula, external rotation of the scapula, clavicular retraction, and clavicular elevation under the condition of active arm elevation. This was most pronounced for scapular upward rotation through the mid-range (90-120 degrees) of arm elevation.

INTERPRETATION

The upper and lower trapezius and serratus anterior muscles have an important role in producing upward rotation of the scapula especially throughout the mid-range of arm elevation. Additionally, it appears that capsuloligamentous and passive muscle tension contribute to scapulothoracic motion during arm elevation. Assessment of the upper and lower trapezius and serratus anterior muscles and upward rotation of the scapula should be part of any shoulder examination.

Effects of muscle fatigue on 3-dimensional scapular kinematics

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 degrees of elevation), external rotation (up to 120 degrees of elevation), and upward rotation (up to 60 degrees 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.

Anatomical and biomechanical mechanisms of subacromial impingement syndrome

Subacromial impingement syndrome is the most common disorder of the shoulder, resulting in functional loss and disability in the patients that it affects. This musculoskeletal disorder affects the structures of the subacromial space, which are the tendons of the rotator cuff and the subacromial bursa. Subacromial impingement syndrome appears to result from a variety of factors. Evidence exists to support the presence of the anatomical factors of inflammation of the tendons and bursa, degeneration of the tendons, weak or dysfunctional rotator cuff musculature, weak or dysfunctional scapular musculature, posterior glenohumeral capsule tightness, postural dysfunctions of the spinal column and scapula and bony or soft tissue abnormalities of the borders of the subacromial outlet. These entities may lead to or cause dysfunctional glenohumeral and scapulothoracic movement patterns. These various mechanisms, singularly or in combination may cause subacromial impingement syndrome.

Comparison of Surface Sensor and Bone-Fixed Measurement of Humeral Motion

A common method of tracking humeral motion involves securing a thermoplastic cuff to the humerus with an electromagnetic sensor attached. The data on the accuracy of this technique are limited. This study addressed two questions: (a) How similar are surface and bone-fixed measurements of 3-D humeral rotations? (b) How similar are surface and bone-fixed measurements of 3-D humeral translations? Electromagnetic motion sensors were secured to a bone-fixed external humeral fixator, a surface humeral cuff, and the skin over the sternum and scapular acromion process. The 3-D data were collected during successive slow velocity (10–20°/second) repetitions of humeral active-assisted scapular plane abduction, sagittal plane flexion, and internal/external rotation with the arm adducted. Root mean square errors of surface measures compared to bone-fixed angular and translational values were calculated, and paired t-tests were computed between the two methods. Root mean square errors for humeral rotations ranged from 1° (1%) for humeral elevation during scapular plane abduction to 7.5° (9%) for humeral internal/external rotation. Peak errors were under-representations of 5.7° for internal/external rotation during scapular plane abduction and 15.6° for internal rotation with the arm adducted at the side. Average translation errors ranged from 0.1 to 2.1 mm. Data from this study suggest that dynamic measurement of humeral motion with a surface humeral cuff sensor can be performed for certain slow velocity motions with root mean square errors less than 8°. Caution is called for when interpreting internal/external rotation values, which were underrepresented. Results may vary with one’s age, weight, or general physical condition, with different velocities of movement, or with different movements.

Three-dimensional shoulder kinematics in individuals with C5-C6 spinal cord injury

The shoulder kinematics of five able-bodied subjects and those of five arms in three subjects with spinal cord injuries at C5 or C6 levels were measured as the subjects elevated their arms in three different planes: coronal, scapular and sagittal. The range of humeral elevation was significantly reduced in all spinal cord injury (SCI) subjects relative to able-bodied subjects. Over this restricted range of humeral motion, the scapula of SCI subjects tended to be medially rotated, relative to able-bodied subjects, and the protraction and spinal tilt angles of the scapula of the SCI subjects indicated scapular winging. These results are consistent with paralysis or at least with significant weakness of the serratus anterior muscle. If further study confirms this hypothesis, functional neuromuscular stimulation of the serratus anterior muscle via a nerve cuff electrode may be an effective intervention for improving shoulder function in C5-C6 SCI.

The design of a five-degree-of-freedom powered orthosis for the upper limb

In response to the need for a sophisticated powered upper-limb orthosis for use by people with disabilities and/or limb weakness or injury, the MULOS (motorized upper-limb orthotic system) has been developed. This is a five-degree-of-freedom electrically powered device having three degrees of freedom at the shoulder, one at the elbow and one to provide pronation/supination. The shoulder mechanism consists of a serial linkage having an equivalent centre of rotation close to that of the anatomical shoulder; this is a self-contained module in which power transmission is provided by tensioned cables. The elbow and pronation/supination modules are also self-contained. The system has been designed to operate under three modes of control: 1. As an assistive robot attached directly to the arm to provide controlled movements for people with severe disability. In this case, it can be operated by a variety of control interfaces, including a specially designed five-degree-of-freedom joystick. 2. Continuous passive motion for the therapy of joints after injury. The trajectory of the joints is selected by 'walk-through' programming and can be replayed for a given number of cycles at a chosen speed. 3. As an exercise device to provide strengthening exercises for elderly people or those recovering from injury or surgery. This mode has not been fully implemented at this stage. In assistive mode, prototype testing has demonstrated that the system can provide the movements required for a range of simple tasks and, in continuous passive motion (CPM) mode, the programming system has been successfully implemented. Great attention has been paid to all aspects of safety. Future work is required to identify problems of operation, and to develop new control interfaces.

Glenohumeral subluxation, scapula resting position, and scapula rotation after stroke: a noninvasive evaluation

OBJECTIVES

To determine whether scapular downward tilt (ScDT) and dynamic scapular lateral rotation (ScLR) in subjects with and without stroke is associated with subluxation, and to prove the reliability of a Scapula Locator System in an elderly population.

DESIGN

Repeated measures of ScLR by 2 observers.

SETTING

Outpatient rehabilitation department of a district general hospital.

PARTICIPANTS

To test device reliability, 5 healthy men (mean age +/- standard deviation, 72 +/- 5 yr). To test scapula position, 30 stroke patients (19 men, 11 women; mean age, 73 +/- 6 yr) and 15 healthy controls (12 men, 3 women; mean age, 62 +/- 6 yr).

INTERVENTIONS

The control subjects' ScDT was compared with stroke subjects' ScDT after stratification according to 3 patterns of ScLR symmetry and the presence of palpable glenohumeral subluxation.

MAIN OUTCOME MEASURES

For device reliability, 3-way analysis of variance. For scapula position, triangulated location by Scapula Locator System of acromion, inferior angle, and root of the scapular spine; then measurement of scapula motion to determine symmetry, lag, or lead.

RESULTS

The inter- and intraobserver reliability of the Scapula Locator System device was high (1% of variance each). Normal ScDT was positive (left side: 10.94 degrees +/- 2.62 degrees; right side: 9.69 degrees +/- 4.36 degrees ), indicating a downward-facing glenoid fossa. This finding was unchanged by stroke (10.46 degrees +/- 2.42 degrees ). All controls and 16 stroke subjects had symmetry between shoulders for ScLR rate and ScDT. Two other patterns (p <.01) of ScLR were found after stroke: 8 subjects had a slower rate of affected arm ScLR (lag) with a correspondingly greater ScDT on the affected side (2.61 degrees +/- 6.7 degrees ); 6 subjects had a faster rate of affected arm ScLR (lead) but with an upward-facing glenoid fossa on the affected side (ScDT: -11.84 degrees +/- 8.48 degrees ). No significant inter- or intrasubject difference in ScDT existed in the 6 cases of glenohumeral subluxation.

CONCLUSIONS

The scapula normally tilts downward with or without stroke. The effect of stroke is similar on tonic (ScDT) and phasic (ScLR) control of scapula position. Subluxation is not linked with a particular scapular resting position after stroke.

Scapular and clavicular kinematics during humeral elevation: a study with cadavers

A combination of kinematic testing and graphic reconstruction of cadaveric shoulders was used to characterize shoulder kinematics during a simulated passive clinical range-of-motion examination. Cadaveric shoulders were elevated in the coronal, scapular, and sagittal planes while the scapula, clavicle, and humerus were kinematically tracked. Graphic models of each shoulder were created from computed tomography data. The models were animated to display the experimental motions. Shoulder kinematics varied between elevation planes. The scapular and clavicular rotations were relatively small until the humerus reached approximately 90 degrees of elevation. Clavicular and scapular rotations that occurred at low humeral elevation angles for elevation in the coronal plane were significantly larger than for the other two planes. The glenohumeral to scapulothoracic ratio was approximately equal to 2 for the entire range of elevation for each elevation plane, but it was dramatically larger during early elevation than during late elevation.