# Application of the Gait Kinematics Index in Patients with Cerebral Palsy
## 2 Materials and Methods  
### Participants  
An a priori sample size estimation/power analysis was performed in G*Power. To calculate a representative sample size for the ANOVA test/the Kruskal-Wallis ANOVA test involving three groups, the expected effect size (large 0.4), significance level (\(\alpha=0.05\)), and statistical power (\(1-\beta=0.80\)) were calculated. Appropriate statistical formulas and data from previous studies [28] were used to calculate the minimum number of participants. These calculations aimed to ensure adequate statistical power to detect significant differences between the groups. G*Power indicated a total sample size of 66 participants. In the current study, 77 participants were recruited. This study was a single-cross-sectional study, which means that participants were assessed only once, without being re-examined. The study involved a reference group and a group of patients with cerebral palsy, and was conducted at the Upper Silesian Children's Health Centre (USCHC) in Poland. Participants were recruited in the hospital. The recruitment process was systematic and in accordance with the ethical standards of clinical research. Patients with CP were recruited from the hospital's patient database, including those already receiving hospital treatment. Patients who met the initial eligibility criteria were informed about the study by telephone or in a face-to-face interview with a doctor or member of the research team. The patient qualification assessment was carried out by the doctors of the USCHC.  
Inclusion criteria for the reference group were as follows: age between 30 months and 18 years, no musculoskeletal disorders (medically qualified for the study), and a written consent to participate in the study by a parent/guardian.  
The following criteria were used to select patients with CP for the study group: age of patients in all groups--from 30 months to 18 years--diagnosed with cerebral palsy in the form of spastic syndrome (diagnosis based on the clinical picture and results of neuroimaging examinations), patients rehabilitated and treated with botulinum toxin, patients qualified for the procedure of selective rhizotomy of dorsal roots, patients qualified for at least level II on the GMFCS scale, parental consent obtained for gait testing, and patients walking independently and in cooperation. Patients under 30 months of age, patients diagnosed with motor disorders other than cerebral palsy, patients using lower limb orthoses and unable to walk without orthoses, non-rehabilitated patients, and uncooperative patients were excluded from the study group. This study was approved by the ethical committee of the Medical University of Silesia in Katowice (protocol number KNW/0022/KB1/19/11).  
The testing group consisted of 56 healthy children--without dysfunctions of the motor system (28 boys and 28 girls)--as well as 72 patients with CP (45 boys and 27 girls). The reference group (the healthy group) was composed of 56 healthy children aged 11 \(\pm\) 3 y.o., body mass: 41.8 \(\pm\) 13.2 kg and body height: 147 \(\pm\) 17 cm. The age of children with CP was 9 \(\pm\) 4. y.o., body mass: 29.3 \(\pm\) 13.7 kg and body height: 128.73 \(\pm\) 22.3 cm.  
The patients were divided in terms of CP type--diplegia (43 patients), hemipleggia (17 patients) or quadriplegia (12 patients)--as well as in terms of treatment methods: children subjected solely to rehabilitation (12 patients), botulinum toxin injection procedures (43 patients) or qualified for the procedure of selective rhizotomy of dorsal roots (17 patients).