Reliability and Measurement Precision of a Low-cost Head-mounted Laser Device for Cervical Joint Position Error Assessment: A Reproducibility Study

1. Postgraduate Student, Department of Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Ambala, Haryana, India. 2. Postgraduate Student, Department of Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Ambala, Haryana, India. 3. Postgraduate Student, Department of Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Ambala, Haryana, India. 4. Postgraduate Student, Department of Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Ambala, Haryana, India. 5. Postgraduate Student, Department of Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Ambala, Haryana, India. 6. Postgraduate Student, Department of Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Ambala, Haryana, India. 7. Postgraduate Student, Department of Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Ambala, Haryana, India. 8. Assistant Professor, Department of Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Ambala, Haryana, India.

Abstract

Introduction: Sensorimotor control and postural stability heavily rely on cervical propriocep-tion. A head-mounted laser pointer is often used in a clinical practice as it is a simple and inexpen-sive head-to-neutral Joint Position Error (JPE) test. Its test-retest reliability and measurement preci-sion need to be established.

Aim: To find out the test-retest reliability and measurement error of an indigenously developed low-cost head-mounted laser pointer instrument to measure cervical JPE in healthy adults.

Materials and Methods: This was an observational repeated-measures reliability test conducted in the Department of Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilita-tion, Maharishi Markandeshwar (Deemed to be University), Mullana, Ambala, Haryana, India, from November 2025 to December 2025. This study employed a test-retest reliability design with repeated measures in-volving 51 healthy adults aged 18-45 years of age. Cervical JPE was measured in flexion, right rotation, left rotation and right lateral flexion and left lateral flexion using a laser device mounted on the head placed 90 cm away against a board. The protocol was repeated again after 72 hours under the same conditions. The Intraclass Correlation Coefficient (ICC 2,1) was used to assess test-retest reliability. The measure of absolute reliability was determined by computing the Standard Error of Measurement (SEM) and Minimal Detectable Change (MDC) at the 95% confidence level (MDC95). Intersession comparison was analysed through Bland Altman analysis.

Results: High reliability of all movements with ICC values of between 0.98 and 0.99 were exhib-ited. The range of SEM was between 0.03° and 0.04°, and the range of MDC was between 0.08° and 0.12°. Bland Altman analysis revealed that there were small mean bias and close Limits of Agreement (LoA).

Conclusion: The test-retest reliability of the device showed excellent performance and low measurement error among the healthy adults. The findings support its potential utility as a low-cost clinical assessment tool on cervical proprioception.

Proprioception, Reproducibility of results, Test-retest reliability, Young adults