1. Reliability and Validity of Two Clinical Scapular Dyskinesis Tests Michael Donohoe1,2, Niamh Ní Chéilleachair2, Giles Warrington3, Neil Rowan1, & Siobhán O’Connor2. Bioscience Research Institute, Athlone Institute of Technology, Westmeath, Ireland1 Department of Life and Physical Science, Athlone Institute of Technology, Westmeath, Ireland2 Department of Physical Education and Exercise Science, University of Limerick, Limerick, Ireland3
Introduction
Participant Recruitment
Experimental Design
30 healthy males with no upper limb pain 7 days prior to testing
Aged 18 – 45
Scapular dyskinesis is a term given to visible alterations in the scapula’s position and motion patterns, and such alterations have been associated with shoulder injury (Tate et al. 2009). Previous research has correlated abnormalities in scapula positioning and motion with impingement symptoms, rotator cuff dysfunction, and instability (Kibler et al. 2013). Due to these associations a number of classification systems have been developed to assess scapular dyskinesis.
Tate et al. (2009) used 3D electromagnetic motion sensors to validate one such classification system by identifying changes in scapular kinematics in those determined to possess scapular dyskinesis. However, since scapular dyskinesis is thought to be a result of abnormal muscle activation patterns (MAPs) there is a need to assess these classification systems to ascertain whether they are capable of identifying alterations in the MAPs of key periscapular muscles, which determine the scapula’s position and motion.
The objective of this study was to establish the inter- and intra-tester reliability of two previously published classification systems and to establish their validity in assessing altered MAPs.
Ethical approval was granted by the AIT Research Ethics Committee.
Thirty healthy males (25±5 years) free from any orthopaedic or neurological disorders participated in this study.
Participants were recruited from a convenience sample of collegiate staff and students, and the general public (Table 1).
The study design is illustrated in Figure 1.
Informed Consent & Screening
Introduction to study
Plain Language Statement
Informed consent
Pre-participation Questionnaire
Pre-participation screening
Collection of anthropometric data
Methodology
Video Recording of Scapular Dyskinesis Tests
Testing
All participants completed both the McClure et al. (2009) Scapular Dyskinesis Test (SDT) and the O'Connor et al. (2015) Scapular Control Test (SCT). The tests were first performed and videotaped without any sensors in place, to allow the therapists an unobstructed view of the posterior thorax. This was followed by the placement of the sensors and the collection of surface electromyographic (sEMG) data for the assessment of MAPs.
The two therapists underwent standardised training prior to assessment of participants videos, via self-directed slideshows with embedded pictures and videos, of both scapular dyskinesis classification systems. Both presentations detailed the motion available at the scapulothoracic joint and what is considered normal or abnormal movement.
Intraclass correlation coefficients (ICC), with 95% Confidence Intervals (CI), were computed for both inter- and intra-tester reliability for comparison with previous publications.
For the assessment of MAPs, sEMG electrodes were place on five key muscles on both the dominant and non-dominant sides; middle deltoid, upper trapezius fibres, lower trapezius fibres, infraspinatus, and serratus anterior (Figure 2). The sensor on the middle deltoid also collected accelerometer data, which was used to identify the onset of movement.
Participants were grouped into normal and dyskinesis groups depending on tester A’s evaluation and their MAPs were compared for group differences (Figure 3). To identify MAPs, the mean onset of muscle activity for each muscle was compared between groups using independent sample T-tests.
Placement of sEMG Sensors
sEMG Analysis of Scapular Dyskinesis Tests
Figure 1: Schematic diagram of study design.
Table 1: Participant Demographics.
Participants
Male (n=30)
Age (y)
25 ± 5
Hand Dominance
29 Right/1 Left
Height (m)
1.78 ± .06
Weight (kg)
80.9 ± 11.5
Body Mass Index (kg/m2)
25.4 ± 3.0
Results
Inter- and Intra-tester Reliability: Both the SDT and SCT scored between good to excellent for ICC inter- and intra-tester reliability. Inter- and Intra-tester results can be seen, with 95% CI values, in Table 2.
Validity: No statistical difference in MAPs was found between the normal and dyskinesis groups in all but one muscle. Only the infraspinatus muscle on the non-dominant shoulder during the SCT demonstrated a significant difference between groups (p=0.014, d=1.08). Figure 3 illustrates the MAPs of the non-dominant limb during the SCT.
Figure 2: Placement of sEMG sensors.
Table 2: SDT & SCT inter- and intra-tester reliability.
Test
Inter-tester Reliability
Intra-tester Reliability
ICC
95% CI
SDT
SCT
Discussion
This study demonstrated that the inter- and intra-tester reliability for both the SDT and the SCT show good to excellent reliability.
However, while both tests proved to be reliable the EMG data questions their validity for determining alterations in MAPs in those determined to possess scapular dyskinesis. The results depicted in Figure 3 illustrate that there was considerable variability in both groups as to when each muscle was activated relevant to movement of the arm. The variability seen in both groups would suggest that the timing of muscle activation is not consistent in either those determined to demonstrate normal or abnormal scapulothoracic motion. This study therefore speculates whether altered MAPs of periscapular muscles truly plays a key role in the altered kinematics of the scapulae. This could be extrapolated to question treatment interventions that aim to improve scapular kinematics by addressing altered MAPs. * *
Figure 3: SCT MAPs during Abduction: Non-dominant limb mean & 95% CI times of muscle activation for normal (n=13) & dyskinesis (n=17) groups.
Conclusion
While both tests demonstrated high inter- and intra-tester reliability neither proved to be valid at determining a difference in MAPs between groups. The results indicate that:
The use of these tests in a clinical setting to determine abnormalities in MAPs may be unwarranted
The high variation in onset of muscle activation observed across groups may call into question the relevance of altered MAPs and scapular dyskinesis as a risk factor for injury.
References
Further Information
Kibler, W. Ben, Ludewig, P.M., McClure, P.W., Michener, L. a, Bak, K., Sciascia, A.D. (2013) Brit J Sport Med, 47(14), 877–85.
McClure, P., Tate, A.R., Kareha, S., Irwin, D., Zlupko, E. (2009). J Athl Training, 44(2), 160–164.
O’Connor, S., Mccaffrey, N., Whyte, E., Moran, K. (2015). J Sport Rehabil [In press]
Tate, A.R., McClure, P., Kareha, S., Irwin, D., Barbe, M.F. (2009). J Ahl Training, 44(2), 165–173.
For further information on this study please contact:
This study was funded by the AIT President Seed Fund.