Josien van den Noort, Suzanne Wiertsema, Karin Hekman, Casper Schönhuth, Joost Dekker, Jaap Harlaar

VU University Medical Center, Department of Rehabilitation Medicine, MOVE Research Institute, Amsterdam, The Netherlands

Background
The scapula plays an important role in shoulder function. In people with shoulder pathologies, alterations in scapular position and motion (scapular dyskinesis) have been observed. To direct interventions aimed at improving scapular position, motion, and muscle force, objective and reliable measurement of scapular dyskinesis in clinical setting is important. Currently used measures are not reliable or objective, clinically not suitable, static or invasive (e.g. visual based scapular dyskinesis tests, optoelectronic markers, scapula locators or bonepins). An inertial and magnetic measurement system (IMMS: small, wireless sensors containing gyroscopes, accelerometers, and magnetometers, Xsens MTw) could be a good alternative to measure scapular motion in clinical routine. The aim of this study is to evaluate the intra- and inter-observer reliability and the validity of the IMMS for measurement of scapular motion in 20 healthy subjects and in 20 patients with shoulder pathology and suspicion of scapular dyskinesis.

Methods
So far, twenty healthy subjects without shoulder problems participated in the reliability study. For intra-observer reliability, the scapular motion was measured with the IMMS by the same physical therapist on two different days (T0 and T1). For inter-observer reliability, at T1 a second physical therapist also measured the scapular motion with the IMMS. Four IMMS sensors were placed on the scapula (edge of spina), thorax, upper and lower arm. The subjects repeatedly elevated their arm in the sagittal plane (anteflexion) and in the frontal plane (ab/adduction) (3 trials with 3 repetitions per plane). 3D kinematics of the scapula with respect to the thorax were measured. Reliability of 3D scapular motion at 0, 30, 60, 90 and 120 deg arm elevation was assessed.

Results & Discussion
 The intra- & inter-observer reliabilities are found to be high and comparable for all movements (standard error of measurement about 4 deg).
In the near future, patients measurements will be performed to assess reliability and validity of the IMMS for scapular dyskinesis. The IMMS is well suitable for application in clinical routine since sensors are wireless, small and easy to use, and measurement could be performed objectively during dynamic tasks.

Publications
Part of this study has been presented at the ESMAC 2012 conference.