# Is the head-mounted laser an appropriate tool to measure cervical movement across three planes?

## TL;DR

The head-mounted laser is effective for measuring cervical movement in some planes but not all, suggesting it is not fully reliable for complete clinical assessments.

## Contribution

This study is the first to evaluate the head-mounted laser's accuracy in measuring cervical movement across three planes using a validated IMU.

## Key findings

- The head-mounted laser accurately measured movement in the sagittal and transverse planes.
- It failed to accurately measure lateral flexion in the coronal plane.
- Other devices are recommended for full cervical position assessment.

## Abstract

The head-mounted laser is commonly used in clinical proprioceptive tests, but its ability to measure movement across three planes of motion has not been investigated. Therefore, this study evaluated the head-mounted laser against a validated gold standard multi-sensor inertial measurement unit (IMU) (XsensTM) in measuring cervicocephalic movement across three planes. Fourteen healthy adults (seven males and seven females) performed six repetitions each of active cervical flexion, extension, lateral flexion and rotation, whilst instructed to maintain the laser beam within a bullseye corresponding to 4.5° of movement. Primary plane means XsensTM range of motion (ROM) was used to evaluate if movement remained less than 4.5°. During flexion, extension and rotation movements, mean ROM in the primary plane using XsensTM remained within the 4.5° threshold (2.97°−3.57°), indicating that the head-mounted laser corresponded with the IMU (p ≤ 0.01). However, XsensTM mean lateral flexion movement reached 11.34° and 12.10° for left and right lateral flexion, indicating poor correspondence (p = 0.95 and 0.97). The head-mounted laser is appropriate for clinical movement assessment in the sagittal and transverse planes but not recommended for the coronal plane. Other devices should be considered for complete clinical assessment of cervical position sense.