*2.1. Participants*

The study was approved by the Bioethics Committee of the Faculty of Medicine of the University of Rzeszow, Poland (9/2/2017). All children and their parents were informed about the procedures of this study and have signed written informed consent. All measurements were performed in accordance to the Declaration of Helsinki. Participants were recruited from the rehabilitation center for children and youth in Poland. The study population included 37 pediatric patients (19 male and 18 female, with a mean age of 13 years and 7 months). Sixteen children had a right hemiparetic CP and 21 had a left hemiparetic CP (Table 1). All participants walked without additional aids.

Inclusion criteria for hemiplegic CP children were: unilateral, spastic CP as defined by Bax et al. [11]; ability to walk independently at least 10 m; and age between 6 and 18 years. Exclusion criteria were: a previous orthopedic or neurosurgical intervention; botulinum toxin injections within the last 12 months; systemic, anti-spasticity medications; and inability to understand the oral instructions given during the gait analysis. All participants had the posterior leaf spring AFO (PLS) prescribed by their physician. It allows slight plantarflexion, as well as dorsiflexion in stance to promote 'normal' ankle rocker function and to create more dynamic gait. All children had been wearing the PLS for at least 1 month before the gait analysis.



BMI—Body Mass Index, GMFCS—Gross Motor Function Classification System.

### *2.2. Data Collection*

3D-gait analysis was performed using a six-camera (120 Hz) movement analysis system with passive markers (BTS Smart, Milan, Italy).

The study procedure included:


Reflective markers were placed at defined anatomical points on the pelvis and lower limbs, according to the modified Davis protocol [12]. When walking with the posterior leaf spring AFO and shoes, the lateral malleolus markers were placed on the skin, and the heel and toe markers were placed on the shoes at the positions best projecting the anatomical landmarks (at the level of calcaneous bone tuberosity aligned with the marker at the level of fifth metatarsal). All other markers remained at the same positions throughout the testing procedure. All subjects were asked to walk along a 12-m walkway at self-selected speed, both barefoot and wearing their AFO, in the random order. For each condition, six successive gait trials were recorded and the results of an average of six full gait cycles were subject for further analysis. The same experienced specialist performed these 3DGAs.

Selected spatio-temporal parameters of the gait (the stance phase—percentage of the gait cycle, step length, gait speed, and gait cadence), as well as selected, specific kinematic parameters of the gait (ankle dorsiflexion at initial contact, maximal ankle dorsiflexion at swing, knee flexion at initial contact, maximal knee flexion at swing, knee + hip flexion), for both a ffected and non-a ffected lower limb, were computed and analyzed.

### *2.3. GDI Calculations*

The GDI was determined based on the following 9 kinematic parameters: pelvic and hip range of motion in all three planes, knee flexion and extension, ankle dorsiflexion and plantarflexion, and foot progression. GDI values were calculated using the Excel spreadsheet developed by Schwartz and Rozumalski [7].

### *2.4. GVI Calculations*

The GVI was determined based on the following nine spatiotemporal gait parameters: step length (cm), stride length (cm), step time (s), stride time (s), swing time (s), single support time (s), double support time (s), velocity (cm/s), and standard deviations (SDs) of each parameter. GVI values were computed using the Excel spreadsheet developed by Gouelle et al. [9].

### *2.5. Statistical Analysis*

The significance of the differences of the gait parameters in the study group between the two conditions (walking with orthoses and walking barefoot) was calculated using a non-parametric Wilcoxon test. The significance of differences between these two conditions was assessed using a non-parametric, precise version of this test for small samples. The level of significance was assumed at *p* < 0.05. Statistical analyses were performed using Statistica software (StatSoft, ver. 10.0, Krakow, Poland).
