Concurrent validity of a novel digital dynamometerfor assessing performance on the Cranio-Cervical Flexion Test

The Cranio-Cervical Flexion Test (CCFT) is a validated clinical test used to evaluate deep cervical flexor muscle function. A pressure biofeedback unit (PBU) has traditionally been the reference device. Recently, a new portable digital device known as the Neuromuscular Cranio-cervical Device (NOD) has been developed as a potential alternative.

In this cross-sectional concurrent validation study, 88 participants were recruited from four outpatient physiotherapy practices, including individuals with current neck pain and individuals with a previous history of neck pain. All participants performed the CCFT using both devices. The PBU was inflated to a baseline pressure of 20 mmHg, with the participant then performing C-CF to increase the pressure in increments of 2 mmHg over five progressive stages, while the NOD was calibrated to corresponding force targets. Agreement and concurrent validity between the devices were assessed, and C-CF range of motion (ROM) was analyzed using linear mixed-effects models.

Agreement between CCFT performance scores obtained with the NOD and the PBU was 94.3%, with a very strong positive correlation (Spearman's ρ = 0.930, p < 0.001). The NOD measured slightly greater C-CF ROM than the PBU (mean difference 0.68°), with significant differences at lower CCFT stages that converged at higher stages of the test.

These findings demonstrate strong concurrent validity between the NOD and the PBU, supporting the NOD as a valid digital alternative for assessment of the CCFT.