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Validity and reliability of the GYKO inertial sensor system for the assessment of the elbow range of motion.

BACKGROUND
The evaluation of joints range of motion (ROM) represents a fundamental step in the diagnosis of joint disorders. Assessors usually measure the ROM angle through a universal goniometer (UG). GYKO inertial system (Microgate, Bolzano, Italy) represent a noninvasive, easy-to-use, Inertial Measurement Unit (IMU) method for the measurement of the elbow ROM. The aim of this study was to validate the GYKO digital device comparing it with the gold standard UG in the measurement of elbow flexion-extension ROM in healthy subjects.


METHODS
Thirty healthy subjects (15 females, 15 males; mean age: 34 years, range 25-58 years) were enrolled. The elbow ROM of the dominant arm was measured with two methods, UG and GYKO. Active flexion-extension movement of the elbow was measured by two operators with UG (A1_UG; A2_UG) and with GYKO (A1_GYKO; A2_GYKO; B_GYKO). Intra-rater reliability, inter-rater reliability, and concurrent validity were analyzed by intraclass correlation coefficient (ICC) values. Bland-Altman plot was used to compare UG and GYKO.


RESULTS
Both methods were very reliable (P<0.001). Intra-rater reliability showed strong correlation respectively for the UG (ICC=0.798) and for GYKO (ICC=0.859) while inter-rater reliability showed moderate correlation with UG (ICC=0.726) and strong correlation with GYKO (ICC=0.942). The concurrent validity, obtained by three comparisons (A1, A2 and B) showed moderate correlation (ICC: 0.576-0.776).


CONCLUSIONS
The results of this study support the use of GYKO as useful as the UG for the assessment of the active flexion-extension ROM of the elbow.