Research Article: Quantitative Evaluation of Gait Disturbance on an Instrumented Timed Up-and-go Test

Date Published: February 01, 2019

Publisher: JKL International LLC

Author(s): Shigeki Yamada, Yukihiko Aoyagi, Kazuo Yamamoto, Masatsune Ishikawa.


Although the 3-m timed up-and-go test (TUG) is reliable for evaluating mobility, TUG time is insufficient to evaluate mild gait disturbance; we, therefore aimed to investigate other measurements with instrumented TUG (iTUG) using a free smartphone application. Our inclusion criterion in this study is only that participants can walk without any assistance. This study included three heterogeneous groups; patients who underwent a tap test or shunt surgery, 29 inpatients hospitalized for other reasons, and 87 day-care users. After the tap test, 28 were diagnosed with tap-positive idiopathic normal-pressure hydrocephalus (iNPH) and 8 were diagnosed with tap-negative. Additionally, 18 patients were assessed iTUG before and after shunt surgery. During iTUG, time and 3-dimensional (3D) acceleration were automatically recorded every 0.01 s. A volume of the 95% confidence ellipsoid (95%CE) of all plots for 3D acceleration was calculated. Additionally, an iTUG score was defined as (95%CE volume) 0.8 / 1.9 – 1.9 × (time) + 60. The measurement reliability was evaluated using intraclass correlations and Bland-Altman plots. The participants with mild gait disturbance who accomplished within 13.5 s on the iTUG time had the 95%CE volumes for 3D acceleration of ≥70 m3/s6 and iTUG scores of ≥50. The mean iTUG time was shortened and the mean 95%CE volumes and iTUG scores were increased after the tap test among 28 patients with tap-positive iNPH and after shunt surgery among 18 patients with definite iNPH. Conversely, the mean iTUG score among 8 patients with tap-negative was decreased after the tap test. The intraclass correlations for the time, 95%CE volume and iTUG score were 0.97, 0.80 and 0.90, respectively. Not only the iTUG time but also the 95%CE volume was important for evaluating mobility. Therefore, the novel iTUG score consisting both is useful for the quantitative assessment of mobility.

Partial Text

In this study, we described a novel iTUG method using a free iPhone application that was able to assess not only the time but also the angular speed and acceleration in three axial directions by designing automatic analysis algorithms. After a systematic investigation, both the time and 95%CE volume for the tracks of the chronological changes of 3D acceleration on iTUG were found to play an important role in evaluating mobility. Moreover, the time and 95%CE volume for 3D acceleration on iTUG had a high accuracy and reliability. The time or gait velocity on TUG is reported to be insufficient to assess the effects of the tap test, including for diagnosing iNPH and selecting shunt candidates, especially in patients with mild gait disturbance [13, 15]. The cutoff times on TUG at a fast walking speed were reported to be 11-13.5 s for identifying individuals at an increased risk of falls [3, 8, 16-21]. Particularly, the most popular cutoff time on TUG at a fast pace for predicting falls is ≥13.5s [3, 8, 16, 18]. In this study, tap-positive iNPH patients with an initial TUG time of ≥13.5 s showed improved TUG time after the tap test, whereas those with a TUG time of <13.5 s did not demonstrate reduced time but showed increased ellipsoid volume on iTUG. This result confirms that the TUG time is a reliable measure for evaluating gait disturbance only at ≥13.5 s, and mild gait disturbance with a TUG time of <13.5 s should be evaluated with a focus on the 95%CE volume for 3D acceleration measured using iTUG rather than based on the TUG time. Many patients with iNPH whose TUG time is < 13.5 s have various gait disturbances and a history of falls. The reduced stride length (i.e. senile gait), diminished step height (shuffling), broad based gait, unsteady gait, antepulsion, and magnetic gait are known to be typical features of gait disturbance in iNPH [22, 23]. The reduced stride length might be mainly due to reduction of forward and vertical upward acceleration generated by kicking out with a toe. Reduction of vertical upward acceleration may be related with the diminished step height. Reduction of horizontal acceleration may cause the broad-based gait. Reduction of backward acceleration may cause the antepulsion. Further research is required to ascertain the relationship between the disturbed gait pattern in iNPH and characteristics of 3D acceleration during the iTUG.   Source:


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