Atypical Gait Cycles in Parkinson's Disease

Abstract

It is important to find objective biomarkers for evaluating gait in Parkinson's Disease (PD), especially related to the foot and lower leg segments. Foot-switch signals, analyzed through Statistical Gait Analysis (SGA), allow the foot-floor contact sequence to be characterized during a walking session lasting five-minutes, which includes turnings. Gait parameters were compared between 20 PD patients and 20 age-matched controls. PDs showed similar straight-line speed, cadence, and double-support compared to controls, as well as typical gait-phase durations, except for a small decrease in the flat-foot contact duration (-4% of the gait cycle, p = 0.04). However, they showed a significant increase in atypical gait cycles (+42%, p = 0.006), during both walking straight and turning. A forefoot strike, instead of a "normal" heel strike, characterized the large majority of PD's atypical cycles, whose total percentage was 25.4% on the most-affected and 15.5% on the least-affected side. Moreover, we found a strong correlation between the atypical cycles and the motor clinical score UPDRS-III (r = 0.91, p = 0.002), in the subset of PD patients showing an abnormal number of atypical cycles, while we found a moderate correlation (r = 0.60, p = 0.005), considering the whole PD population. Atypical cycles have proved to be a valid biomarker to quantify subtle gait dysfunctions in PD patients.

Keywords: Parkinson’s disease; UPDRS; foot-floor contact; human locomotion; statistical gait analysis.

Figure 1

Schematic representation of the walking path. Subjects walked back and forth, without interruptions, along a straight path of 9 m, for approximately 5 min. U-turns were included in the analysis.

Figure 2

Panel (A) represents the acquisition system. Foot-switches were placed under the heel, the first, and the fifth metatarsal heads of each foot to detect the foot-floor contact events. Panel (B) shows an example of foot-switch signal acquired from the more-affected side of a representative PD patient of the sample population with the indication of the four gait phases (H: Heel Contact, F: Flat-Foot Contact, P: Push-Off, and S: Swing).

Figure 3

Example of 4-level foot-switch signals and gait cycle phases (H: Heel Contact, F: Flat-Foot Contact, P: Push-Off, and S: Swing) acquired from the right foot (more affected side) of a representative PD patient. Panel (A) represents an example of a typical gait cycle, while panel (B) shows two examples of atypical gait cycles (PFPS and PS).

Figure 4

Schematic representation of the methodological steps implemented in this study from the data acquisition step to the assessment of the results.

Figure 5

Boxplots of the percentage of atypical gait cycles (i.e., any gait cycle showing a foot-floor contact sequence different from HFPS) relative to the most frequently observed atypical gait-cycle classes in PD and control populations. Outliers are indicated by circles. Single and double asterisks represent statistically significant differences with p-values lower than 0.05 and 0.01, respectively.

Figure 6

Correlation analysis between the normalized percentage of atypical gait cycles (for the more-affected side of PD patients) and UPDRS-III computed for: (A) the whole PD group, and (B) the $PD\_with\_Atyp$ subgroup.