Use of a Single Wearable Sensor to Evaluate the Effects of Gait and Pelvis Asymmetries on the Components of the Timed Up and Go Test, in Persons with Unilateral Lower Limb Amputation

Abstract

The Timed Up and Go (TUG) test quantifies physical mobility by measuring the total performance time. In this study, we quantified the single TUG subcomponents and, for the first time, explored the effects of gait cycle and pelvis asymmetries on them. Transfemoral (TF) and transtibial (TT) amputees were compared with a control group. A single wearable inertial sensor, applied to the back, captured kinematic data from the body and pelvis during the 10-m walk test and the TUG test. From these data, two categories of symmetry indexes (SI) were computed: One SI captured the differences between the antero-posterior accelerations of the two sides during the gait cycle, while another set of SI quantified the symmetry over the three-dimensional pelvis motions. Moreover, the total time of the TUG test, the time of each subcomponent, and the velocity of the turning subcomponents were measured. Only the TF amputees showed significant reductions in each SI category when compared to the controls. During the TUG test, the TF group showed a longer duration and velocity reduction mainly over the turning subtasks. However, for all the amputees there were significant correlations between the level of asymmetries and the velocity during the turning tasks. Overall, gait cycle and pelvis asymmetries had a specific detrimental effect on the turning performance instead of on linear walking.

Keywords: kinematics; limb prosthesis; sensory–motor gait disorders; spatial–temporal analysis; symmetry index.

Figure 1

Top view of typical path of 3-m long for the TUG test. The test was performed in clockwise (A,B) and counterclockwise (C,D) directions. The single subcomponents are indicated in the panels (A,B). Four basic phases are performed to accomplish the final turning, before sitting down (B,D): (1) the body rotated of about 90° around the inner limb, (2) allowing the swing of the outer limb; (3) the body rotated of another 90° around the outer limb, (4) allowing the swing of the inner limb and the completion of 180° body rotation.

Figure 2

Representative examples of anterior–posterior (AP) body acceleration during gait cycle performed on the left and right sides by one control participant (CTRL), one transtibial amputee (TT), and one transfemoral amputee (TF). The waveforms represent the means and the standard deviations of AP accelerations from the total number of cycles during the 10-m walk test. The linear correlation between the left and the right AP accelerations, estimated by the Pearson correlation coefficient, was the basis for the gait cycle symmetry index (see Section 2 for details).

Figure 3

Representative examples of pelvis angle obliquity during gait cycle performed on the left and right sides by one control participant (CTRL), one transtibial amputee (TT) and one transfemoral amputee (TF). The waveforms represent the means and the standard deviations of pelvis angle obliquity from the total number of cycles during the 10-m walk test. The linear correlation between the left and the right pelvis angle obliquity, estimated by the Pearson correlation coefficient, was the basis for the gait cycle symmetry index. (See Section 2 for details).

Figure 4

Box and whisker plots reporting the median value (horizontal line within the box) and the variability as interquartile range (vertical length of the box) and as the highest and the lowest values (lines above and below the box) of symmetry indexes of gait cycle (A), pelvis tilt (B), pelvis obliquity (C), and pelvis rotation (D), for each group. In all subplots, the horizontal lines with asterisks indicate statistically significant differences (* p < 0.05; ** p < 0.01). Abbreviations and symbols: SI = symmetry index; TF = transfemoral group (orange boxes); TT = transtibial group (green boxes).

Figure 5

Box and whisker plots reporting median and variability (as described in Figure 4) of parameters measured during the Timed Up and Go test: Total time (A), sit to stand (B), walking forward (C), mid-turning (D), walking back (E), final turning (F), (G) stand to sit, (H) mid-turning velocity, (I) final turning velocity. Abbreviations as in Figure 4. Symbols: * p < 0.05; ** p < 0.01.

Figure 6

Spearman’s correlation analysis between symmetry index and mid- and final turning time and velocity. Symmetry indexes of gait cycle, pelvis obliquity, and pelvis rotation were correlated with mid-turning time and velocity, when the amputated limb was in inner position (A–F), and with final turning time and velocity, when the amputated limb was in outer position (G–L). Abbreviation and symbol: r_s, Spearman’s Rho coefficient; p, level of significance; orange circles, TF; green circles, TT.