The Use of Two Different Smartphone Applications in Measuring

This study is designed as an observational, methodological study to investigate the intra-rater and inter-rater reliability and concurrent validity of two smartphone-based inclinometer applications used for sagittal spinal curvature assessment.

The study will include healthy volunteers aged 18-25 years. Participants will be informed about the study procedures, and written informed consent will be obtained before enrollment. Demographic and anthropometric characteristics, including age, sex, height, body weight, and body mass index, will be recorded.

Measurement Procedures An experienced physiotherapist will identify and mark five anatomical reference points along the spine, extending from the cervical region to the lumbosacral region. These reference points will be used to standardize the measurement locations across devices and assessment sessions.

Sagittal spinal inclination angles will be measured using three different devices:

A conventional gravity-based bubble inclinometer. An Android smartphone equipped with an inclinometer application. An iOS smartphone equipped with an inclinometer application. Measurements will be performed at the same anatomical reference points using all three devices. The conventional inclinometer will serve as a reference instrument for evaluating the concurrent validity of the smartphone applications.

Reliability Assessment To evaluate intra-rater and inter-rater reliability, measurements will be performed by three assessors using a standardized assessment protocol.

Each measurement will be repeated twice during the initial assessment session. A second assessment session will be conducted 24-48 hours after the first session, during which the measurements will be repeated using the same three devices.

The repeated measurements will allow the evaluation of within-assessor consistency, agreement between different assessors, and measurement stability across assessment sessions.

Concurrent Validity Assessment The measurements obtained from the Android and iOS smartphone applications will be compared with those obtained using the conventional bubble inclinometer.

The agreement between the smartphone applications and the conventional inclinometer will be examined to determine whether smartphone-based measurements provide comparable results for sagittal spinal inclination assessment.

Statistical Analysis Descriptive statistics will be used to summarize participant characteristics and measurement results.

Intraclass correlation coefficients (ICCs) will be calculated to evaluate intra-rater reliability, inter-rater reliability, and test-retest reliability. Measurement error will be examined using the standard error of measurement (SEM) and minimal detectable change (MDC).

Concurrent validity will be assessed through correlation and agreement analyses. Pearson correlation coefficients, Lin's concordance correlation coefficients, and Bland-Altman analyses will be used to investigate the relationships, concordance, and systematic differences between measurements obtained using the smartphone applications and the conventional inclinometer.

Expected Contribution The study aims to provide evidence regarding the reliability and concurrent validity of smartphone-based inclinometer applications for assessing sagittal spinal inclination. The findings may help determine the potential clinical applicability of smartphone-based measurement tools in physiotherapy and rehabilitation assessments.

Inclusion criteria

• Being over 18 years of age,
• being able to stand and walk without an assistive device,
• not having experienced back pain or lower extremity pain in the last 6 months,
• and being willing to participate in the study.

Exclusion criteria

• Lack of consent,
• lower extremity injuries (dislocation, sprain) within one month prior to measurement,
• lower extremity fractures within the last 6 months,
• tactile sensitivity that prevents the adoption of a free and habitual posture.