Abstract
BackgroundThe evaluation of foot posture in a clinical setting is useful to screen for potential injury, however disagreement remains as to which method has the greatest clinical utility. An inexpensive and widely available imaging system, the Microsoft Kinect™, may possess the characteristics to objectively evaluate static foot posture in a clinical setting with high accuracy. The aim of this study was to assess the intra-rater reliability and validity of this system for assessing static foot posture.MethodsThree measures were used to assess static foot posture; traditional visual observation using the Foot Posture Index (FPI), a 3D motion analysis (3DMA) system and software designed to collect and analyse image and depth data from the Kinect. Spearman’s rho was used to assess intra-rater reliability and concurrent validity of the Kinect to evaluate foot posture, and a linear regression was used to examine the ability of the Kinect to predict total visual FPI score.ResultsThe Kinect demonstrated moderate to good intra-rater reliability for four FPI items of foot posture (ρ = 0.62 to 0.78) and moderate to good correlations with the 3DMA system for four items of foot posture (ρ = 0.51 to 0.85). In contrast, intra-rater reliability of visual FPI items was poor to moderate (ρ = 0.17 to 0.63), and correlations with the Kinect and 3DMA systems were poor (absolute ρ = 0.01 to 0.44). Kinect FPI items with moderate to good reliability predicted 61% of the variance in total visual FPI score.ConclusionsThe majority of the foot posture items derived using the Kinect were more reliable than the traditional visual assessment of FPI, and were valid when compared to a 3DMA system. Individual foot posture items recorded using the Kinect were also shown to predict a moderate degree of variance in the total visual FPI score. Combined, these results support the future potential of the Kinect to accurately evaluate static foot posture in a clinical setting.
Highlights
The evaluation of foot posture in a clinical setting is useful to screen for potential injury, disagreement remains as to which method has the greatest clinical utility
Reliability of the visual Foot Posture Index (FPI) items was mixed, with the intraclass correlation coefficient (ICC) value for the total visual FPI score demonstrating good to excellent intra-rater reliability (ICC = 0.87), moderate to good reliability was shown for lateral curvature and congruence of the medial longitudinal arch (ρ = 0.52 to 0.63), and poor reliability for talar head palpation, calcaneal inversion/eversion, talo-navicular joint bulging and forefoot abduction/adduction (ρ = 0.17 to 0.42)
The concurrent validity results demonstrated that all individual visual FPI items correlated poorly with the corresponding items recorded using either the Kinect or Vicon systems, with all of the items indicating little to fair relationships
Summary
The evaluation of foot posture in a clinical setting is useful to screen for potential injury, disagreement remains as to which method has the greatest clinical utility. Despite the existence of many different techniques to evaluate foot posture in the clinical setting, there is still disagreement as to which method is the most clinically useful [8]. Some studies have found contrasting results regarding the association between abnormal foot type and injury depending on the clinical technique employed [3,4,9,10], with some researchers arguing that these conflicting findings may be at least partly due to the lack of reliability and validity of many of these measures [11,12,13]. The inability of many of the static measures of foot posture to predict dynamic function calls in to question their clinical utility [14,15]
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