Dynamic tracking of the scapula using skin-mounted markers

Three-dimensional shoulder kinematics: Upright four-dimensional computed tomography in comparison with an optical three-dimensional motion capture system

Although shoulder kinematics have been analyzed by various methods, dynamic shoulder motion is difficult to track. This study aimed to validate the shoulder kinematic analysis using upright four-dimensional computed tomography (4DCT) and to compare the results with optical three-dimensional motion capture. During active elevation, bilateral shoulders of 10 healthy volunteers were tracked using 4DCT and motion capture. The scapulothoracic and glenohumeral rotations and the scapulohumeral rhythm (SHR) at each position were calculated, and the differences between 4DCT and motion capture were compared. During 10-140° of humerothoracic elevation, the scapulothoracic joint showed upward rotation, internal rotation, and posterior tilting, and the glenohumeral joint showed elevation, external rotation, and anterior plane of elevation in both analyses. In scapulothoracic rotations, the mean differences between the two analyses were -2.6° in upward rotation, 13.9° in internal rotation, and 6.4° in posterior tilting, and became significant with humerothoracic elevation ≥110° in upward rotation, ≥50° in internal rotation, and ≥100° in posterior tilting. In glenohumeral rotations, the mean differences were 3.7° in elevation, 9.1° in internal rotation, and -8.8° in anterior plane of elevation, and became significant with humerothoracic elevation ≥110° in elevation, ≥90° in internal rotation, and ≥100° in anterior plane of elevation. The mean overall SHRs were 1.8 in 4DCT and 2.4 in motion capture, and the differences became significant with humerothoracic elevation ≥100°. The 4DCT analysis of in vivo shoulder kinematics using upright computed tomography scanner is feasible, but the values were different from those by skin-based analysis at the elevated arm positions.

Three-Dimensional Quantitative Evaluation of the Scapular Skin Marker Movements in the Upright Posture

Motion capture systems using skin markers are widely used to evaluate scapular kinematics. However, soft-tissue artifact (STA) is a major limitation, and there is insufficient knowledge of the marker movements from the original locations. This study explores a scapular STA, including marker movements with shoulder elevation using upright computed tomography (CT). Ten healthy males (twenty shoulders in total) had markers attached to scapular bony landmarks and underwent upright CT in the reference and elevated positions. Marker movements were calculated and compared between markers. The bone-based and marker-based scapulothoracic rotation angles were also compared in both positions. The median marker movement distances were 30.4 mm for the acromial angle, 53.1 mm for the root of the scapular spine, and 70.0 mm for the inferior angle. Marker movements were significantly smaller on the superolateral aspect of the scapula, and superior movement was largest in the directional movement. Scapulothoracic rotation angles were significantly smaller in the marker-based rotation angles than in the bone-based rotation angles of the elevated position. We noted that the markers especially did not track the inferior movement of the scapular motion with shoulder elevation, resulting in an underestimation of the marker-based rotation angles.

A Modified Kinematic Model of Shoulder Complex Based on Vicon Motion Capturing System: Generalized GH Joint with Floating Centre

Due to the complex coupling motion of shoulder mechanism, only a small amount of quantitative information is available in the existing literature, although various kinematic models of the shoulder complex have been proposed. This study focused on the specific motion coupling relationship between glenohumeral (GH) joint center displacement variable quantity relative to the thorax coordinate system and humeral elevation angle to describe the shoulder complex. The mechanism model of shoulder complex was proposed with an algorithm designed. Subsequently, twelve healthy subjects performed right arm raising, lowering, as well as raising and lowering (RAL) movements in sixteen elevation planes, and the motion information of the markers attached to the thorax, scapula, and humerus was captured by using Vicon motion capturing system. Then, experimental data was processed and the generalized GH joint with floating center was quantized. Simultaneously, different coupling characteristics were detected during humerus raising as well as lowering movements. The motion coupling relationships in different phases were acquired, and a modified kinematic model was established, with the description of overall motion characteristics of shoulder complex validated by comparing the results with a prior kinematic model from literature, showing enough accuracy for the design of upper limb rehabilitation robots.

New Tracking System of Human Scapula Using Ultrasonography and Motion Sensors: A Descriptive Test-Retest Design

CONTEXT

Several studies have shown that the kinematics of the scapula is altered in many disorders that affect the shoulder. Description of scapular motion in the chest continues to be a scientific and clinical challenge.

OBJECTIVE

To check the validity and reliability of a new, minimally invasive method of tracking the internal and external rotation of the scapula using ultrasound imaging combined with the signal provided by a 3-dimensional electromagnetic sensor.

DESIGN

A cross-sectional study with a repeated-measures descriptive test-retest design was employed to evaluate this new tracking method. The new method was validated in vitro and the reliability of data over repeated measures between scapula positions was calculated in vivo.

SETTING

University laboratory.

PARTICIPANTS

A total of 30 healthy men and women.

MAIN OUTCOME MEASURE

The validation of the scapula rotation tracking using the in vitro model was calculated by Pearson correlation test between a 2-dimensional cross-correlation algorithm of the new method and another software image. The reliability of the tracking of the scapula rotation was measured using the intraclass correlation coefficient.

RESULTS

In the validation in vitro, the correlation of rotations obtained by the 2 methods was good (r = .77, P = .01). The reliability in vivo had excellent results (intraclass correlation coefficient = .88; 95% confidence interval, .82-.93) in the test-retest analysis of 8 measures. The intrarater analysis of variance test showed no significant differences between the measures (P = .85, F = 0.46).

CONCLUSION

Ultrasound imaging combined with a motion sensor to track the scapula has been shown to be a reliable and valid method for measuring internal and external rotation during separation of the upper limb.

Comparison of the kinematics and kinetics of shoulder exercises performed with constant and elastic resistance

Background

Internal and external rotation exercises of the shoulder are frequently performed to avoid injury and pain. Knowledge about the motion and loadings of the upper extremities during these exercises is crucial for the development of optimal training recommendations. However, a comparison of the angles and corresponding moments in the upper extremities that are achieved during internal and external rotation exercises for the shoulder by using different resistance types has not yet been performed. Therefore, the aim of the study was to examine upper extremity kinetics and kinematics in 3D of the internal and external rotation exercises.

Methods

The kinematics and kinetics of 12 participants while they performed 10 different exercises with a constant and with an elastic external load corresponding to 2% body mass was assessed. The motion of the upper extremities was recorded three-dimensionally with a motion capture system, using a newly developed marker set and joint coordinate systems with 28 markers. The applied external load was measured with a load cell placed in series with the external resistance, and moments were calculated using an inverse dynamics approach.

Results

The range of motion and the joint loading was highly dependent on the exercises. The range of motion in the glenohumeral joint did not differ significantly between the two resistance types, whereas internal/external rotation moments were significantly higher with constant resistance than those with elastic resistance.

Conclusions

Larger or lower moments can, therefore, be achieved through selection of the appropriate resistance type, while the range of motion can be altered through the selection of exercise type. Therefore, the loading motion patterns identified in this study can help to choose suitable shoulder exercises dependent on the training objective.

Electronic supplementary material

The online version of this article (10.1186/s13102-018-0111-7) contains supplementary material, which is available to authorized users.

A survey of human shoulder functional kinematic representations

In this survey, we review the field of human shoulder functional kinematic representations. The central question of this review is to evaluate whether the current approaches in shoulder kinematics can meet the high-reliability computational challenge. This challenge is posed by applications such as robot-assisted rehabilitation. Currently, the role of kinematic representations in such applications has been mostly overlooked. Therefore, we have systematically searched and summarised the existing literature on shoulder kinematics. The shoulder is an important functional joint, and its large range of motion (ROM) poses several mathematical and practical challenges. Frequently, in kinematic analysis, the role of the shoulder articulation is approximated to a ball-and-socket joint. Following the high-reliability computational challenge, our review challenges this inappropriate use of reductionism. Therefore, we propose that this challenge could be met by kinematic representations, that are redundant, that use an active interpretation and that emphasise on functional understanding.

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.

Measurement of dynamic scapular kinematics using an acromion marker cluster to minimize skin movement artifact

The measurement of dynamic scapular kinematics is complex due to the sliding nature of the scapula beneath the skin surface. The aim of the study was to clearly describe the acromion marker cluster (AMC) method of determining scapular kinematics when using a passive marker motion capture system, with consideration for the sources of error which could affect the validity and reliability of measurements. The AMC method involves placing a cluster of markers over the posterior acromion, and through calibration of anatomical landmarks with respect to the marker cluster it is possible to obtain valid measurements of scapular kinematics. The reliability of the method was examined between two days in a group of 15 healthy individuals (aged 19-38 years, eight males) as they performed arm elevation, to 120°, and lowering in the frontal, scapular and sagittal planes. Results showed that between-day reliability was good for upward scapular rotation (Coefficient of Multiple Correlation; CMC = 0.92) and posterior tilt (CMC = 0.70) but fair for internal rotation (CMC = 0.53) during the arm elevation phase. The waveform error was lower for upward rotation (2.7° to 4.4°) and posterior tilt (1.3° to 2.8°), compared to internal rotation (5.4° to 7.3°). The reliability during the lowering phase was comparable to results observed during the elevation phase. If the protocol outlined in this study is adhered to, the AMC provides a reliable measurement of upward rotation and posterior tilt during the elevation and lowering phases of arm movement.

Intra-protocol repeatability and inter-protocol agreement for the analysis of scapulo-humeral coordination

Multi-center clinical trials incorporating shoulder kinematics are currently uncommon. The absence of repeatability and limits of agreement (LoA) studies between different centers employing different motion analysis protocols has led to a lack dataset compatibility. Therefore, the aim of this work was to determine the repeatability and LoA between two shoulder kinematic protocols. The first one uses a scapula tracker (ST), the International Society of Biomechanics anatomical frames and an optoelectronic measurement system, and the second uses a spine tracker, the INAIL Shoulder and Elbow Outpatient protocol (ISEO) and an inertial and magnetic measurement system. First within-protocol repeatability for each approach was assessed on a group of 23 healthy subjects and compared with the literature. Then, the between-protocol agreement was evaluated. The within-protocol repeatability was similar for the ST ([Formula: see text] = 2.35°, [Formula: see text] = 0.97°, SEM = 2.5°) and ISEO ([Formula: see text] = 2.24°, [Formula: see text] = 0.97°, SEM = 2.3°) protocols and comparable with data from published literature. The between-protocol agreement analysis showed comparable scapula medio-lateral rotation measurements for up to 120° of flexion-extension and up to 100° of scapula plane ab-adduction. Scapula protraction-retraction measurements were in agreement for a smaller range of humeral elevation. The results of this study suggest comparable repeatability for the ST and ISEO protocols and between-protocol agreement for two scapula rotations. Different thresholds for repeatability and LoA may be adapted to suit different clinical hypotheses.

The accuracy of an external frame using ISB recommended rotation sequence to define shoulder joint angle

When investigating shoulder kinematics, it may be necessary to limit shoulder joint angles at a specific level. Previous studies used external frames or external surfaces to assist the participant to reach the shoulder joint angles of interest. The accuracy of these methods, however, has not yet been investigated. In the current study, an external frame was designed to assist in maintaining specific shoulder postures in a wide range. The three degrees of freedom of rotation of the proposed frame were designed to be consistent with the description of shoulder joint angles recommended by the International Society of Biomechanics. Six participants used this frame to perform 118 different shoulder postures. The reference joint angles measured by a motion tracking system were compared with the frame-defined angles. The angle differences among all the participants ranged from 12.7° to 85.6°, with an average of 32.2° (SD 15.1°) across all postures. For the postures with elevation angles on or below horizontal, the average angle difference was 23.7° (SD 8.5°). Findings suggest that errors exist when using an external frame to assist in reaching specific shoulder postures. Error is minimized at elevation angles close to -30°, and the performance is poor for extreme shoulder postures.

Direct Kinematic Modeling of the Upper Limb During Trunk-Assisted Reaching

The study proposes a rigid-body biomechanical model of the trunk and whole upper limb including scapula and the test of this model with a kinematic method using a six-dimensional (6-D) electromagnetic motion capture (mocap) device. Large unconstrained natural trunk-assisted reaching movements were recorded in 7 healthy subjects. The 3-D positions of anatomical landmarks were measured and then compared to their estimation given by the biomechanical chain fed with joint angles (the direct kinematics). Thus, the prediction errors was attributed to the different joints and to the different simplifications introduced in the model. Large (approx. 4 cm) end-point prediction errors at the level of the hand were reduced (to approx. 2 cm) if translations of the scapula were taken into account. As a whole, the 6-D mocap seems to give accurate results, except for pronosupination. The direct kinematic model could be used as a virtual mannequin for other applications, such as computer animation or clinical and ergonomical evaluations.

In vivo three-dimensional motion analysis of the shoulder joint during internal and external rotation

PURPOSE

The purpose of this study was to assess accurately the three-dimensional movements of the scapula and humerus relative to the thorax during internal/external rotation motion with abduction of the shoulder joint.

METHODS

Ten right shoulders of ten healthy volunteers were examined using a wide-gantry open magnetic resonance imaging (MRI) system. MRI was performed every 30° from 90° external rotation to 90° internal rotation of the shoulder joint.

RESULTS

The contribution ratio of the scapulothoracic joint was 12.5% about the long axis of the humerus during internal/external rotation motion. With arm position changes from 90° external rotation to 60° internal rotation, most movement was performed by the glenohumeral joint. Conversely, at internal rotation of ≥60°, the scapula began to markedly tilt in the anterior direction. At 90° internal rotation, the scapula was significantly tilted anteriorly (p < 0.05) when compared with the other positions.

CONCLUSIONS

We clarified the existence of a specific scapulohumeral motion pattern, whereby the glenohumeral joint moves with internal rotation and the scapulothoracic joint moves with anterior tilt together with internal rotation motion of the shoulder joint.

Motion analysis of the glenohumeral joint during activities of daily living

The shoulder complex has a larger range of motion (ROM) than any other joint complex in the human body, leaving it prone to numerous injuries. Objective kinematic analysis could yield useful functional insights that may assist clinical practice. Non-invasive optoelectronic motion analysis techniques have been used to assess the shoulders of five healthy subjects performing ROM tasks and 10 functional tasks of daily living. The four most demanding tasks - touching the side and back of the head, brushing the opposite side of the head, lifting an object to shoulder height and lifting an object to head height, required 78%, 60%, 61% and 71%, respectively, of the glenohumeral elevation necessary for full abduction in the scapular plane for the 10 shoulders. This has implications for clinical practice where maximum arm elevation is commonly used to determine a patient's ability to return to work and other everyday activities.

Alteration of scapula lateral rotation for subjects with the reversed anatomy shoulder replacement and its influence on glenohumeral joint contact force

It has previously been reported that motion of the scapula varies for subjects with shoulder joint pathologies and is different from that of normal subjects. In this study, an electromagnetic tracking device was used to measure the three-dimensional scapula motion of nine patients with Bayley-Walker (B-W) reverse anatomy joint replacements. The data were then compared to scapula kinematics of 12 normal subjects with no known shoulder pathology. The scapula kinematics for each subject was determined and a regression analysis to find the mean scapula lateral rotation (SLR) for B-W and normal subjects was performed. The regression model which showed the highest change compared to normal was identified and was used in the biomechanical shoulder model to predict the glenohumeral joint contact force. A high variability of the scapula kinematics was observed, with some subjects having a maximum SLR smaller than that of the normal subjects and some similar to the normal subjects. It was found that scapula may move in such a way to keep the deltoid length at its optimum. The change in the scapula kinematics affected the predicted joint force and its point of application. Hence, knowledge of scapular kinematics is essential for realistic modelling of implanted shoulders.