Study of Gait and Posture Kinematic Indices for the Evaluation of Ankle-Foot Orthoses *

Abstract

Motor disabilities resulting from pathologies such as brain injuries, strokes, spinal cord injuries and other neurological diseases usually lead to deficits in locomotion. One such problem is Drop Foot (DF), which can severely impair walking function. To cope with this pathology, ankle-foot orthoses (AFOs) can be used, which allow the patient to improve ankle dorsiflexion during the swing phase of the foot. The aim of this research work is to evaluate the impact of the use of a passive AFO orthosis on gait by studying the kinematic indices of gait in patients with DF. The study was conducted on a population of 19 patients at the IRCCS Istituti Clinici Maugeri in Bari. Ninteen subjects (12 males, 7 females), with unilateral DF syndrome, were involved in this research. The experimental data collection procedures consisted of gait analysis sessions performed with the Mobility Lab system by APDM (APDM Inc, Portland, OR, USA, http://apdm.com). In this test subjects wore 3 IMUs (low back and dorsal surface of the feet) and are instructed to stand quietly for 30 s and then asked to walk over a 7 meters walkway, turn around a pivot and walk back to the starting point. Each subject performed two sessions in two different gait conditions: (i) unconstrained gait (without any AFO); (ii) gait with an AFO attached to the participant’s affected limb. The median value of each parameter among the three selected trials was extracted and considered for the analysis. We focused on the following set of spatio-temporal parameters, which have clinical relevance in patients with DF: Elevation at Midswing ( cm ) (EMS), Gait Cycle Time ( s ) (GCT), Stride Length ( m ) (SL). These metrics were statistically analysed with two-way ANOVA test to explore the effects produced by the variables ‘Condition’ (With/Without AFO), ‘Limb’ (Affected/Contralateral) and the interaction between these two factors. Statistical analyses were performed using R version 4.0.3 (R Foundation, Vienna, Austria). Table 1 presents the results of the statistical test, reporting p-values when a significant difference was obtained (p−value < 0.05). Otherwise the absence of statistical significance is reported (ns). The level of statistical significance is specified by a different number of stars (∗): the higher number of stars, the lower α value threshold for the p − value. Fig. 1 shows the boxplots representing the distribution of the analysed data. This paper presented a clinical study regarding the impact of using a solid plastic AFO on spatio-temporal gait metrics of 19 patients with DF syndrome. Our analysis pointed out that EMS is generally higher in affected limb than in contralateral limb, as the patient compensates for difficulties in lifting the front part of the foot by increasing foot elevation during swing. However the use of the AFO has no significant effects on either foot. On the contrary, the GCT is reduced when the AFO is worn by the patient demonstrating higher confidence in step execution. The use of the AFO also tends to improve the stride length of both feet, however this difference is not statistically significant. In future studies, it would be better to evaluate changes in gait metrics on a longer walking trial, to carry out the assessment on a larger number of steps.