Smartphone Accelerometry for Gait Analysis in Children With Unilateral Spastic Cerebral Palsy

Children with unilateral spastic cerebral palsy may have differences in walking speed, step timing, cadence, and symmetry between the affected and unaffected lower limbs. Instrumented gait laboratories can provide detailed gait measurements, but they may be expensive, time-consuming, or unavailable in many clinical settings. Smartphones contain built-in motion sensors that may offer a simpler and more accessible method of measuring gait.

This methodological validation study will examine the concurrent validity and intra-session test-retest reliability of smartphone-embedded linear accelerometry for the assessment of spatiotemporal gait parameters in children with unilateral spastic cerebral palsy.

A convenience sample of 35 children will be recruited from the Deraya University outpatient clinic. Eligible participants will be 6 to 12 years of age, have a clinical diagnosis of unilateral spastic cerebral palsy, and be classified as Gross Motor Function Classification System level I or II.

Each participant will attend one assessment session. A Samsung Galaxy A7 smartphone will be secured horizontally over the lower back at the L4-L5 vertebral level using an adjustable waist belt. This location is intended to approximate the body's center of mass. The smartphone's internal linear accelerometer will record movement data using the Phyphox application.

Participants will walk at a comfortable, self-selected speed along a flat, unobstructed 10-meter indoor walkway. At the same time, a high-definition video camera mounted on a stable tripod will record the walking trial from a perpendicular distance of approximately 3 meters. The video recordings will be analyzed frame by frame using Kinovea software and will serve as the reference method.

Each child will complete two identical walking trials during the same session. The trials will be separated by a seated rest period of approximately 5 to 10 minutes to reduce fatigue. No therapeutic intervention will be administered, and the child's usual medical or physical therapy care will not be changed.

Data obtained from the smartphone accelerometer and the video analysis will be used to calculate walking velocity, cadence, stride timing, and gait asymmetry. Smartphone-derived measurements will be compared with the corresponding Kinovea-derived measurements to evaluate concurrent validity. Measurements from the first and second walking trials will also be compared to evaluate intra-session test-retest reliability.

The study is intended to determine whether smartphone-based accelerometry can provide valid and repeatable gait measurements that may be useful as a practical, non-invasive, and low-cost clinical assessment method for children with unilateral spastic cerebral palsy.

Inclusion criteria

• Clinical diagnosis of unilateral spastic cerebral palsy.
• Chronological age ranging from 6 to 12 years.
• Gross Motor Function Classification System (GMFCS) Level I or II (capable of walking 10 meters independently without physical support or handheld mobility aids).
• Ability to comprehend and execute simple verbal instructions during clinical evaluation.

Exclusion criteria

• History of lower extremity corrective orthopedic surgery or joint casting within the preceding 12 months.
• Botulinum Toxin Type A injections administered to the lower limbs within the past 6 months.
• Fixed structural bony deformities or rigid joint contractures in the lower extremities.
• Severe, uncorrected visual or auditory deficits that threaten safety or test execution