Modified 3D scapular kinematic patterns for activities of daily living in painful shoulders with restricted mobility: A comparison with contralateral unaffected shoulders

Differences in Tridimensional Shoulder Kinematics between Asymptomatic Subjects and Subjects Suffering from Rotator Cuff Tears by Means of Inertial Sensors: A Cross-Sectional Study

Background: The aim of this study was to analyze differences in three-dimensional shoulder kinematics between asymptomatic subjects and patients who were diagnosed with rotator cuff tears. Methods: This cross-sectional study recruited 13 symptomatic subjects and 14 asymptomatic subjects. Data were obtained from three inertial sensors placed on the humerus, scapula and sternum. Kinematic data from the glenohumeral, scapulothoracic and thoracohumeral joints were also calculated. The participants performed shoulder abductions and flexions. The principal angles of movements and resultant vectors in each axis were studied. Results: The glenohumeral joint showed differences in abduction (p = 0.001) and flexion (p = 0.000), while differences in the scapulothoracic joint were only significant during flexion (p = 0.001). The asymptomatic group showed higher velocity values in all sensors for both movements, with the differences being significant (p < 0.007). Acceleration differences were found in the scapula during abduction (p = 0.001) and flexion (p = 0.014), as well as in the sternum only during shoulder abduction (p = 0.022). Conclusion: The results showed kinematic differences between the patients and asymptomatic subjects in terms of the mobility, velocity and acceleration variables, with lower values for the patients.

In Vitro Simulation of Shoulder Motion Driven by Three-Dimensional Scapular and Humeral Kinematics

In vitro simulation of three-dimensional (3D) shoulder motion using in vivo kinematics obtained from human subjects allows investigation of clinical conditions in the context of physiologically relevant biomechanics. Herein, we present a framework for laboratory simulation of subject-specific kinematics that combines individual 3D scapular and humeral control in cadavers. The objectives were to: (1) robotically simulate seven healthy subject-specific 3D scapulothoracic and glenohumeral kinematic trajectories in six cadavers, (2) characterize system performance using kinematic orientation accuracy and repeatability, and muscle force repeatability metrics, and (3) analyze effects of input kinematics and cadaver specimen variability. Using an industrial robot to orient the scapula range of motion (ROM), errors with repeatability of ±0.1 mm and <0.5 deg were achieved. Using a custom robot and a trajectory prediction algorithm to orient the humerus relative to the scapula, orientation accuracy for glenohumeral elevation, plane of elevation, and axial rotation of <3 deg mean absolute error (MAE) was achieved. Kinematic accuracy was not affected by varying input kinematics or cadaver specimens. Muscle forces over five repeated setups showed variability typically <33% relative to the overall simulations. Varying cadaver specimens and subject-specific human motions showed effects on muscle forces, illustrating that the system was capable of differentiating changes in forces due to input conditions. The anterior and middle deltoid, specifically, showed notable variations in patterns across the ROM that were affected by subject-specific motion. This machine provides a platform for future laboratory studies to investigate shoulder biomechanics and consider the impacts of variable input kinematics from populations of interest, as they can significantly impact study outputs and resultant conclusions.

Assessing Smoothness of Arm Movements With Jerk: A Comparison of Laterality, Contraction Mode and Plane of Elevation. A Pilot Study

Measuring the quality of movement is a need and a challenge for clinicians. Jerk, defined as the quantity of acceleration variation, is a kinematic parameter used to assess the smoothness of movement. We aimed to assess and compare jerk metrics in asymptomatic participants for 3 important movement characteristics that are considered by clinicians during shoulder examination: dominant and non-dominant side, concentric and eccentric contraction mode, and arm elevation plane. In this pilot study, we measured jerk metrics by using Xsens^® inertial measurement units strapped to the wrists for 11 different active arm movements (ascending and lowering phases): 3 bilateral maximal arm elevations in sagittal, scapular and frontal plane; 2 unilateral functional movements (hair combing and low back washing); and 2 unilateral maximal arm elevations in sagittal and scapular plane, performed with both arms alternately, right arm first. Each arm movement was repeated 3 times successively and the whole procedure was performed 3 times on different days. The recorded time series was segmented with semi-supervised algorithms. Comparisons involved the Wilcoxon signed rank test (p < 0.05) with Bonferroni correction. We included 30 right-handed asymptomatic individuals [17 men, mean (SD) age 31.9 (11.4) years]. Right jerk was significantly less than left jerk for bilateral arm elevations in all planes (all p < 0.05) and for functional movement (p < 0.05). Jerk was significantly reduced during the concentric (ascending) phase than eccentric (lowering) phase for bilateral and unilateral right and left arm elevations in all planes (all p < 0.05). Jerk during bilateral arm elevation was significantly reduced in the sagittal and scapular planes versus the frontal plane (both p < 0.01) and in the sagittal versus scapular plane (p < 0.05). Jerk during unilateral left arm elevation was significantly reduced in the sagittal versus scapular plane (p < 0.05). Jerk metrics did not differ between sagittal and scapular unilateral right arm elevation. Using inertial measurement units, jerk metrics can well describe differences between the dominant and non-dominant arm, concentric and eccentric modes and planes in arm elevation. Jerk metrics were reduced during arm movements performed with the dominant right arm during the concentric phase and in the sagittal plane. Using IMUs, jerk metrics are a promising method to assess the quality of basic shoulder movement.

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

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

Reliable interpretation of scapular kinematics depends on coordinate system definition

BACKGROUND

Interpretation of shoulder motion across studies has been complicated due to the use of numerous scapular coordinate systems in the literature. Currently, there are no simple means by which to compare scapular kinematics between coordinate system definitions when data from only one coordinate system is known.

RESEARCH QUESTION

How do scapular kinematics vary based on the choice of coordinate system and can average rotation matrices be used to accurately convert kinematics between scapular local coordinate systems?

METHODS

Average rotation matrices derived from anatomic landmarks of 51 cadaver scapulae (29 M/22 F; 59 ± 13 yrs; 26R/25 L; 171 ± 11 cm; 70 ± 19 kg; 23.7 ± 5.5 kg/m²) were generated between three common scapular coordinate systems. Absolute angle of rotation was used to determine if anatomical variability within the cadaver population influenced the matrices. To quantify the predictive capability to convert kinematics between the three coordinate systems, the average rotation matrices were applied to scapulothoracic motion data collected from 19 human subjects (10 M/9 F; 43 ± 17 yrs; 19R; 173 ± 9 cm; 71 ± 16 kg; 23.6 ± 4.5 kg/m²) using biplane fluoroscopy. Root mean squared error (RMSE) was used to compare kinematics from an original coordinate system to the kinematics expressed in each alternative coordinate system.

RESULTS

The choice of scapular coordinate system resulted in mean differences in scapulothoracic rotation of up to 23°, with overall different shapes and/or magnitudes of the curves. A single average rotation matrix between any two coordinate systems achieved accurate conversion of scapulothoracic kinematics to within 4° of RMSE of the known solution. The average rotation matrices were independent of sex, side, decomposition sequence, and motion.

SIGNIFICANCE

Scapulothoracic kinematic representations vary in shape and magnitude based solely on the choice of local coordinate system. The results of this study enhance interpretability and reproducibility in expressing scapulothoracic motion data between laboratories by providing a simple means to convert data between common coordinate systems. This is necessitated by the variety of available motion analysis techniques and their respective scapular landmark definitions.

Assessment of abduction motion in patients with rotator cuff tears: an analysis based on inertial sensors

Background

Reduced range of motion in the shoulder can be a source of functional limitation. The use of inertial sensors to quantify movement in addition to more common clinical assessments of the shoulder may allow clinicians to understand that they are potentially unnoticed by visual identification. The aim of this study was to generate an explanatory model for shoulder abduction based on data from inertial sensors.

Method

A cross-sectional study was carried out to generate an explanatory model of shoulder abduction based on data from inertial sensors. Shoulder abduction of thirteen older adults suffering from shoulder dysfunction was recorded with two inertial sensors placed on the humerus and scapula. Movement variables (maximum angular mobility, angular peak of velocity, peak of acceleration) were used to explain the functionality of the upper limb assessed using the Upper Limb Functional Index (ULFI). The abduction movement of the shoulder was explained by six variables related to the mobility of the shoulder joint complex. A multivariate analysis of variance (MANOVA) was used to explain the results obtained on the functionality of the upper limb.

Results

The MANOVA model based on angular mobility explained 69% of the variance of the ULFI value (r-squared = 0.69). The most relevant variables were the abduction-adduction of the humerus and the medial/lateral rotation of the scapula.

Conclusions

The method used in the present study reveals the potential importance of the analysis of the scapular and humeral movements for comprehensive evaluation of the upper limb. Further research should include a wider sample and may seek to use this assessment technique in a range of potential clinical applications.

Influence of humeral abduction angle on axial rotation and contact area at the glenohumeral joint

BACKGROUND

Although the elevation angle of the arm affects the range of rotation, it has not been evaluated up to the maximal abduction angle. In this study we conducted an evaluation up to maximal abduction and determined the contact patterns at the glenohumeral (GH) joint.

METHODS

Fourteen healthy volunteers (12 men and 2 women; mean age, 26.9 years) with normal shoulders (14 right and 8 left) were instructed to rotate their shoulders at 0°, 90°, 135°, and maximal abduction for each shoulder at a time. Using 2-dimensional and 3-dimensional single-plane image registration, the internal rotation (IR), external rotation (ER), and range of motion (ROM; ie, axial rotations) at the thoracohumeral (TH) and GH joints, and the contribution ratio (%ROM = GH-ROM/TH-ROM) were calculated for each abduction. The glenoid position with respect to the humeral head was also analyzed.

RESULTS

The TH-IR and TH-ER shifted toward an ER with increasing abduction angle, whereas the TH-ROM significantly decreased except at abduction between 0° and 90° (P < .001). The GH-IR and GH-ROM significantly decreased except at abduction between 0° and 90° (P < .001), but the GH-ER remained constant regardless of the abduction. The contribution ratio exceeded 80% for every abduction angle. The glenoid moved on the central and posterior areas of the humeral head at 0° and 90° abduction, respectively, and on the posterosuperior and anterosuperior areas at 135° and maximal abduction, respectively.

CONCLUSION

Our results provide new knowledge about wide axial rotation up to maximal abduction and constant GH-ER at any abduction.

Kinematic analysis of the shoulder complex after anatomic and reverse total shoulder arthroplasty: A cross-sectional study

BACKGROUND

The movement of the arm relative to the trunk results from coordinated 3D glenohumeral and scapulothoracic movements. Changes in scapula kinematics may occur after total shoulder arthroplasty and could affect clinical and functional outcomes.

OBJECTIVES

To assess the 3D movement of the scapula during arm elevation after anatomic and reverse total shoulder arthroplasty.

DESIGN/METHODS

This was a single-centre, non-randomized, controlled cross-sectional study. Patients with anatomic (n = 14) and reverse total shoulder arthroplasty (n = 9) were prospectively enrolled and were compared to age-matched asymptomatic controls (n = 23). 3D scapular kinematics were assessed by a non-invasive, electromagnetic method during arm abduction and flexion. 3D scapular rotations and 3D linear displacements of the barycentre (geometrical centre) at rest and at 30°, 60° and 90° arm elevation; as well as scapulohumeral rhythm were analysed. Participant groups were compared using one-way ANOVA and Bonferroni post-hoc testing for normally distributed data, and Mann-Whitney U test for non-normally distributed data.

RESULTS/FINDINGS

Total range of scapular lateral rotation and barycentre displacement were increased, and scapulohumeral rhythm was reduced, in patients with anatomic and reverse total shoulder arthroplasty compared with age-matched controls; however, the global scapular kinematic pattern was preserved.

CONCLUSION/INTERPRETATION

For patients after total shoulder arthroplasty, the increased contribution of the scapula to arm elevation is consistent with a compensatory mechanism for the reduced glenohumeral mobility. The stability of the global scapula kinematic pattern reflects its mechanical and neuromotor strength.

Structured Wii protocol for rehabilitation of shoulder impingement syndrome: A pilot study

OBJECTIVE

To determine the feasibility and efficacy of using a structured Nintendo Wii protocol to improve range of motion, strength, and quality of life in patients with shoulder impingement syndrome.

METHODS

A total of 14 patients with shoulder pain were randomized to perform a structured Wii protocol (n=8) or conventional therapy (n=6). Pain-free shoulder range of motion, strength, shoulder pain and disability, and quality of life were assessed pre- and post-treatment.

RESULTS

All 8 patients completed the Wii protocol, and 3 completed conventional therapy. The Wii protocol conferred significant improvements in shoulder range of motion, pain and disability, and quality of life but not strength, whereas conventional therapy conferred a significant improvement in strength.

CONCLUSIONS

As compared to conventional treatment, the structured Wii protocol implemented in this pilot study was a viable adjunct to therapy for shoulder impingement syndrome. Gaming may have a supplemental benefit by increasing motivation, pleasure, and/or adherence. Further investigation in larger cohorts is warranted.

Three-dimensional kinematics of upper limb anatomical movements in asymptomatic adults: Dominant vs. non-dominant

The effect of dominance on upper limb (UL) kinematics has only been studied on scapular movements. Moreover, when an anatomical UL movement is performed in a specific plane, secondary movements in the remaining planes involuntarily occur. These secondary movements have not been previously evaluated. The aim of this study was to compare the kinematics of primary and secondary angles of dominant and non-dominant UL during anatomical movements in asymptomatic adults. 25 asymptomatic adults performed 6 anatomical movements bilaterally: shoulder flexion-extension, abduction-adduction, horizontal abduction-adduction, internal-external rotation, elbow flexion-extension and wrist pronation-supination. Kinematics of the dominant and non-dominant UL were compared by their ranges of motion (ROM) and their angular waveforms (Coefficient of Multiple Correlations, CMC). The comparison between dominant and non-dominant UL kinematics showed different strategies of movement, most notably during elbow flexion-extension (CMC=0.29): the dominant UL exhibited more pronation at maximal elbow flexion. Significant secondary angles were found on most of the UL anatomical movements; e.g. a secondary ROM of shoulder (humero-thoracic) external-internal rotation (69°±16°) was found when the subject intended to perform maximal shoulder abduction-adduction (119°±21°). Bias of dominance should be considered when comparing pathological limb to the controlateral one. Normative values of primary and secondary angles during anatomical movements could be used as a reference for future studies on UL of subjects with neurological or orthopedic pathologies.

Age-related changes analyzing shoulder kinematics by means of inertial sensors

BACKGROUND

Shoulder kinematics alteration has been previously proven in subjects suffering from shoulder damage, which is also related to shoulder degenerative changes as consequence of aging. Because of that, it would be interesting to investigate age-related kinematics. The main objective was to analyze age-related differences in shoulder kinematics by means of inertial sensors in asymptomatic subjects during shoulder abduction and flexion.

METHODS

Twenty-five right arms were measured (11 from the young adult group and 14 from the older adult group). In the young group, age ranged between 20 and 34years old, while in the older group age ranged between 45 and 72years old. Angular mobility and linear acceleration from the scapula, humerus and sternum as well as mobility in the glenohumeral and scapulothoracic joints were calculated by three inertial sensors. Subjects performed shoulder abduction and flexion.

FINDINGS

Significant differences in mobility were found in humerus and scapula in mobility and acceleration during both tasks. Those differences varied depending on the plane analyzed. A moderate negative correlation between age and humerus and scapula ranged from -0.624** to -0.409*. A positive correlation was found in some planes.

INTERPRETATION

The results from the present study suggest that humerus elevation and scapular protraction-retraction as well as medio-lateral rotation are more likely to present kinematics age-related differences, i.e. older: age is associated with less mobility and acceleration in some planes and axes. Results provide inertial tridimensional measures from shoulder complex comparing groups of different age. Findings also concur with previous research supporting age-related shoulder changes.

Does Scapular Motion Regress with Aging and is It Restricted in Patients with Idiopathic Frozen Shoulder?

Purposes:

It has been reported that the amount of posterior tilt and upward rotation in scapular motions decreases with aging. The purposes of the current study were to investigate age related scapular motion regression and scapular restriction in patients with idiopathic frozen shoulder (IFS).

Methods:

The groups were recruited as follows: two groups of 50 asymptomatic subjects aged in their twenties and fifties, and 56 patients with IFS. We passively moved the scapula toward 8 directions: elevation/depression; upward/downward rotation; external/internal rotation; and anterior/posterior tilt. The grading of scapular motion was ranged from 0 to 3 (3, normal; and 0, severe restriction) and the score for each direction and the total aggregated score for all directions were calculated.

Results:

Scapular restriction was present in 3 subjects (6%) in the normal 20s group, 10 (14%) in the 50s group, and 51 (91%) in the IFS group. The total score between the normal 20s and 50s groups did not show statistical difference; however, greater significance was present between the normal 50s group and the IFS group (p < 0.01). There was statistical significance in depression (p < 0.01), downward rotation (p < 0.01), and posterior tilt (p < 0.01) among the 3 groups.

Conclusion:

Depression, downward rotation, and posterior tilt substantially regress with aging. Scapular motions towards depression, downward rotation, external rotation, and posterior tilt are severely restricted in the IFS group.

Studying upper-limb kinematics using inertial sensors: a cross-sectional study

Background

In recent years, there has been a great interest in analyzing upper-limb kinematics in order to investigate scapulohumeral rhythm, as its alteration has been associated with shoulder joint complex injuries. The use of inertial sensors is presented as a convenient and portable analysis method for studying kinematics in terms of angular mobility and linear acceleration. The aim of this study was to analyze upper-limbs kinematics in the three anatomical axes, obtained by inertial sensors.

Results

Descriptive graphics of analytical tasks performed were obtained. The main difference in mobility between the scapula and humerus was found in pitch axis for abduction (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\bar{\text{X}}}$$\end{document}X¯ = 107.6°, SD = 9.3°) and flexion (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\bar{\text{X}}}$$\end{document}X¯ = 113.1°, SD = 9.3°).

Conclusion

The use of inertial sensors for human kinematics analysis is favorable. Although this study identified movement patterns, and supports inertial sensors as a useful device to analyze upper-limb kinematics, further studies with subjects with shoulder pathology to establish differences in movement patterns and scapulohumeral rhythm between healthy and pathological shoulders should be carried out.

Kinematic analysis of reaching movements of the upper limb after total or reverse shoulder arthroplasty

Studies have analyzed three-dimensional complex motion of the shoulder in healthy subjects or patients undergoing total shoulder arthroplasty (TSA) or reverse shoulder arthroplasty (RSA). No study to date has assessed the reaching movements in patients with TSA or RSA. Twelve patients with TSA (Group A) and 12 with RSA (Group B) underwent kinematic analysis of reaching movements directed at four targets. The results were compared to those of 12 healthy subjects (Group C). The assessed parameters were hand-to-target distance, target-approaching velocity, humeral-elevation angular velocity, normalized jerk (indicating motion fluidity), elbow extension and humeral elevation angles. Mean Constant score increased by 38 points in Group A and 47 in Group B after surgery. In three of the tasks, there were no significant differences between healthy subjects and patients in the study groups. Mean target-approaching velocity and humeral-elevation angular velocity were significantly greater in the control group than in study groups and, overall, greater in Group A than Group B. Movement fluidity was significantly greater in the controls, with patients in Group B showing greater fluidity than those in Group A. Reaching movements in the study groups were comparable, in three of the tasks, to those in the control group. However, the latter performed significantly better with regard to target-approaching velocity, humeral-elevation angular velocity and movement fluidity, which are the most representative characteristics of reaching motion. These differences, that may be related to deterioration of shoulder proprioception after prosthetic implant, might possibly be decreased with appropriate rehabilitation.

A new description of scapulothoracic motion during arm movements in healthy subjects

The participation of scapula motion in arm movement is clinically well known and recent three dimensional (3D) analyses using kinematic techniques have confirmed its importance. Scapular motion relative to the thorax has a theoretical maximum of 6 degrees of freedom (DoF), resulting from rotations at both clavicular joints (3 rotational DoF each). However, most recent kinematic studies have only analysed the 3D rotations of the scapula relative to the thorax. In the present study, the 3D translations of the barycentre of the scapula were considered in order to complete the description of movement at the shoulder complex. Eight healthy subjects performed arm elevation in the sagittal and frontal planes, simulated activities of daily living (hair combing and back washing) and maximum voluntary scapula movement (forward and backward rolling). Measurements were recorded using a 6 DoF electromagnetic device and the acromial method of analysis was used. The results showed that 3D scapular rotations and translation of its barycentre were functionally consistent for all tasks. A principal component analysis (PCA) yielded three factors, explaining 97.6% of the variance. The first two factors (protraction and shrug, according to clinical descriptions) combined rotations and translations, consistent with the hypothesis that the scapula rolls over the curved thoracic surface. The third factor related to lateral-medial rotation, thus representing rotation in the plane tangential to the thorax. The PCA suggested that scapular motion can be described using these 3 DoF. This should be studied in a larger group of individuals, including patients with pathological conditions.

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

Specific scapular kinematic patterns to differentiate two forms of dynamic scapular winging

BACKGROUND

Dynamic scapular winging (DSW) is a rare and misdiagnosed disorder causing considerable disability due to reduced scapular stability and abnormal motion. Two common causes are long thoracic nerve lesions resulting in serratus anterior muscle palsy and spinal accessory nerve lesions resulting in trapezius muscle palsy. The aim of this study was to analyse 3D scapular kinematic patterns in patients with DSW due to long thoracic (LTNL) or spinal accessory nerve lesions (SANL).

METHODS

3D scapular kinematics were assessed using a non invasive method involving an electromagnetic device during arm elevation in the frontal and sagittal planes in 9 patients (4 with SANL and 5 with LTNL) with unilateral DSW confirmed by electrical evidence. Within subject affected-unaffected differences were measured and compared between pathological groups (Mann-Whitney).

FINDINGS

Differences between affected and unaffected shoulders were significantly greater for scapular posterior tilt (at rest and 30° for sagittal arm elevation, at rest, 30° and 60° for frontal arm elevation) in the LTNL compared to the SANL group. Differences between affected and unaffected shoulders were significantly greater for scapular protraction (at rest and 60° of sagittal arm elevation, at rest, 30° and 60° of frontal arm elevation) and scapular lateral rotation at 60° for frontal arm elevation in the SANL compared to the LTNL group.

INTERPRETATIONS

These kinematic findings show two different scapular patterns that are specific to the neurological lesion. Moreover our kinematic data relate to specific clinical signs and the functional roles of the muscles involved.

Precision of 3D scapular kinematic measurements for analytic arm movements and activities of daily living

Electromagnetic devices allow the non invasive and accurate measurement of 3D scapula kinematics. The acromial method allows continuous dynamic measurement using a skin surface sensor fixed to the acromion. Inter-session intra and inter-observer repeatability of 3D scapular kinematics have only been partially assessed for analytical movements and never for functional tasks. Inter-session intra and inter-observer repeatability of 3D scapular kinematics were assessed for arm elevation in the sagittal and frontal planes and for two activities of daily living (ADL), hair combing and back washing, in both shoulders of 15 healthy subjects, using the intraclass correlation coefficient (ICC), the standard error of measurement (SEM), the small real difference (SRD) and the Bland and Altman's graphical method. Intra-observer repeatability was good to excellent for every scapular rotation for both arm elevation in isolated planes and ADL (ICC ranged from 0.64 to 0.95). Inter-observer repeatability of scapular rotations was fair to excellent for arm elevation in isolated planes (ICC ranged from 0.49 to 0.92) and poor to excellent for ADL (ICC ranged from 0.35 to 0.89). Inter-observer repeatability of scapular protraction/retraction had the lowest ICC. For both inter-session intra and inter-observer reliability, the SEM and SRD remained low and Bland and Altman's graphical method showed a good repeatability of the measurement method. Longitudinal monitoring of a subject's scapular kinematics by a trained observer is reliable. The inter-observer repeatability of scapular protraction/retraction must be improved.