Validation of Kinect movement analyzer for shoulder movements

In the physiotherapeutic practice to assess the range of motion (ROM) of various joints is fundamental in order to find restrictions and to improve the motion. Goniometer is used conventionally to measure the total ROM at a specific joint. The Kinect movement analyzer is a newly developed motion sensor add-on. The device provides a natural user interface that allows users to interact intuitively and without any intermediary device. Comparing the two methods give us more information and freedom of assessments.
The primary aim of our study was to determine if the Kinect is as reliable as the manual goniometer and whether the same results would be yielded in shoulder movements. Further aim was to compare the proximal (shoulder) and the distal joints (elbow and wrist) by using the conventional method and Kinect device.
50 healthy physiotherapy students (46 female and 4 male; age: 20-25 years) were assessed on their dominant arm. The measurements were first done by a goniometer with an international movement system assessment protocol and straight followed with the Kinect measurements. Statistical analysis was made with MS Excel; mean and SD were calculated, paired t-test was used for determination of significance.
According to our findings shoulder flexion (177.3±6.1° vs 162.7±9.5°; p<0.001) and extension (40.5±11.7° vs 65.9±13.6; p<0.001) differed significantly by using the two methods, resp. Significant differences were also found by investigating the elbow extension (4.4±5.5° vs 7.7±6.3°; p<0.001) and wrist volar flexion (69.8±14.7° vs 65.3±9.5°; p<0.001) with goniometer and Kinect, resp. The elbow flexion (138.8±9.6° vs 140.9±7.4°; p=0.15) and wrist dorsal flexion (75.1±10.8° vs 74.9±10.8°; p=0.9) were not significantly different by using the different methods.
Based on our findings, we conclude that in shoulder flexion, extension, elbow extension and wrist volar flexion further measures are needed before the use of the device in practice, although dorsal flexion and elbow flexion have been proven worthy. Saving time can be expected when dealing with patients in the form of pre-assessments in a waiting room or at home before the visit to the physiotherapist.