Abstract
BackgroundClinical examinations are subjective and often show a low validity and reliability. Objective and highly reliable quantitative assessments are available in laboratory settings using 3D motion analysis, but these systems are too expensive to use for simple clinical examinations. Qinematic™ is an interactive movement analyses system based on the Kinect camera and is an easy-to-use clinical measurement system for assessing posture, balance and side-bending. The aim of the study was to test the test-retest the reliability and construct validity of Qinematic™ in a healthy population, and to calculate the minimal clinical differences for the variables of interest. A further aim was to identify the discriminative validity of Qinematic™ in people with low-back pain (LBP).MethodsWe performed a test-retest reliability study (n = 37) with around 1 week between the occasions, a construct validity study (n = 30) in which Qinematic™ was tested against a 3D motion capture system, and a discriminative validity study, in which a group of people with LBP (n = 20) was compared to healthy controls (n = 17). We tested a large range of psychometric properties of 18 variables in three sections: posture (head and pelvic position, weight distribution), balance (sway area and velocity in single- and double-leg stance), and side-bending.ResultsThe majority of the variables in the posture and balance sections, showed poor/fair reliability (ICC < 0.4) and poor/fair validity (Spearman <0.4), with significant differences between occasions, between Qinematic™ and the 3D–motion capture system. In the clinical study, Qinematic™ did not differ between people with LPB and healthy for these variables. For one variable, side-bending to the left, there was excellent reliability (ICC =0.898), excellent validity (r = 0.943), and Qinematic™ could differentiate between LPB and healthy individuals (p = 0.012).ConclusionThis paper shows that a novel software program (Qinematic™) based on the Kinect camera for measuring balance, posture and side-bending has poor psychometric properties, indicating that the variables on balance and posture should not be used for monitoring individual changes over time or in research. Future research on the dynamic tasks of Qinematic™ is warranted.
Highlights
Clinical examinations are subjective and often show a low validity and reliability
The subjects in the low-back pain (LBP) group were significantly taller: 180 cm (SD = 8.6) compared to 173 cm (SD = 6.9) for the healthy controls, (p = 0.012). Another difference between the groups was that only 25% were classified as physically active in the LBP group compared to 59% in the healthy control group, but there were no differences between the groups regarding body weight; 82 kg in the LBP group compared to 75 kg in the healthy control group (p = 0.297)
In the laboratory-based studies, there was missing data for one subject concerning the measurements of the CoP during the double- and single leg balance trials and another subject’s data was missing concerning the sidebending trials in the reliability study
Summary
Objective and highly reliable quantitative assessments are available in laboratory settings using 3D motion analysis, but these systems are too expensive to use for simple clinical examinations. Visual observations of balance and active movements are challenging, since these movements are fast and, in order to analyse posture, the therapist needs to observe the patient from different directions at the same time. These clinical examinations are highly subjective and often show a low validity and reliability [2,3,4]. There is a need to develop simpler yet more objective ways of assessing posture and balance in the clinic [2]
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