Reliability of Using a Handheld Tablet and Application to Measure Lower Extremity Alignment Angles
King D.L, Belyea B.C. J Sport Rehabil; 2014; ahead of print
Take Home Message: A tablet application is a promising, reliable tool to capture objective landing kinematics. Intra-rater reliability is good to excellent with an average of 6 trials. Inter-rater reliability is fair to excellent depending on the level of experience.
Evaluating an athlete’s risk for injury is necessary to tailor injury prevention plans for an athlete. To assess risk for injury, medical personnel most commonly employ visual observations of an exercise (e.g., drop vertical jump); however, errors in visual estimations of lower extremity joint angles have been reported. Utilizing a tablet with a movement analysis application is a more objective way of determine joint angles during functional movement. Though, the reliability of this new tool has not been established. Therefore, the authors measured the interrater and inter-trial reliability among multiple researchers who evaluated 23 healthy college students using an iPad2 and the KinesioCapture application. The athletes performed 6 two-footed drop vertical jumps, while 1 researcher with experience with 2-D videography captured all the trials. Then, 4 researchers (2 experienced & 2 novices) analyzed the previously captured video for the degrees of knee and hip flexion. The researchers measured 3 of the jumps in the sagittal plane followed by 3 jumps in the frontal plane. Inter-rater reliability ranged from low (0.39) to excellent (0.98). Experienced raters performed slightly better with moderate to good reliability (0.69-0.93) compared with the novice raters (0.39-0.98). Novice and experienced raters were more consistent at measuring joint angles at maximum knee flexion than at initial ground contact. Averaging the trials offered better reliability than assessing each trial separately.
This is an important study since properly operating new and affordable tools are imperative for better objective measures to determine an athlete’s risk of injury. The authors demonstrated that the handheld tablet is a reliable tool to measure knee and hip flexion during a drop vertical jump. The authors also found that experience as well as multiple trials are necessary for optimal reliability. An average of multiple trials may represent the true movement pattern, and reduces the influence of errors (e.g., a bad movement on one trial, error in one measurement). Future research needs to determine how much training medical personnel requires before becoming an experienced rater. Furthermore, all of the videos were captured by a trained individual so we may need to train clinicians to capture an optimal video for these analyses. Future research, will have to determine how much measurement error could be caused by changes in how the videos are acquired. Additionally, assessing how many trials are required for a reliable reading is necessary to apply this tool for functional use. It will also be interesting to see how these measurements compare to traditional motion analysis systems. While more research is needed this study shows that measuring lower extremity movement can be reliably assessed on a tablet if one experienced person records the video, average joint angles are calculated across three trials, and the person doing the measurement is adequately trained. This study is a good reminder that clinicians should check their reliability over time and among other clinicians in a clinic to ensure consistency.
Questions for Discussion: Do you have access to a tablet? If so, would you use the tablet to measure landing kinematics? Do you measure/observe landing kinematics to identify athletes at risk for knee injuries?
Written by: Jane McDevitt, PhD
Reviewed by: Jeffrey Driban