Clinical reliability and validity of a video-based markerless gait evaluation method

Intraclass correlation coefficient (ICC) is a widely used reliability index in test-retest, intrarater, and interrater reliability analyses. This article introduces the basic concept of ICC in the content of reliability analysis.

Three-dimensional kinematic measures of gait are routinely used in clinical gait analysis and provide a key outcome measure for gait research and clinical practice. This systematic review identifies and evaluates current evidence for the inter-session and inter-assessor reliability of three-dimensional kinematic gait analysis (3DGA) data. A targeted search strategy identified reports that fulfilled the search criteria. The quality of full-text reports were tabulated and evaluated for quality using a customised critical appraisal tool. Fifteen full manuscripts and eight abstracts were included. Studies addressed both within-assessor and between-assessor reliability, with most examining healthy adults. Four full-text reports evaluated reliability in people with gait pathologies. The highest reliability indices occurred in the hip and knee in the sagittal plane, with lowest errors in pelvic rotation and obliquity and hip abduction. Lowest reliability and highest error frequently occurred in the hip and knee transverse plane. Methodological quality varied, with key limitations in sample descriptions and strategies for statistical analysis. Reported reliability indices and error magnitudes varied across gait variables and studies. Most studies providing estimates of data error reported values (S.D. or S.E.) of less than 5 degrees , with the exception of hip and knee rotation. This review provides evidence that clinically acceptable errors are possible in gait analysis. Variability between studies, however, suggests that they are not always achieved.

The repeatability of gait variables is an important consideration in the clinical use of results of quantitative gait analysis. Statistical measures were used to evaluate repeatability of kinematic, kinetic, and electromyographic data waveforms and spatiotemporal parameters of 40 normal subjects. Subjects were evaluated three times on each test day and on three different test days while walking at their preferred or natural speed. Intrasubject repeatability was excellent for kinematic data in the sagittal plane both within a test day as well as between test days. For joint angle motion in the frontal and transverse planes, the repeatability was good within a test day and poor between test days. Poor between-day repeatability of joint angle motion in the frontal and transverse planes was noted to be partly due to variabilities in the alignment of markers. Vertical reaction and fore-aft shear forces were more repeatable than the mediolateral shear force. Sagittal plane joint moments were more repeatable than frontal or transverse plane moments. For electromyographic data, repeatability within a day was slightly better than between test days. In general, the results demonstrate that with the subjects walking at their natural or preferred speed, the gait variables are quite repeatable. These observations suggest that it may be reasonable to base significant clinical decisions on the results of a single gait evaluation.