Global and Segment-Level Cervical Motion Answer Different Questions
HeadX
Global cervical ROM provides an accessible way to document overall head-and-neck movement. Segment-level imaging adds a different layer: how that movement is distributed between vertebral levels.
A small 2026 biplane-videoradiography study compared 13 adults with chronic neck pain and 10 asymptomatic controls. It reported selected differences during axial rotation, while no group differences were observed for lateral bending.
The study does not diminish the value of global ROM. It clarifies the measurement boundary: global ROM documents overall movement; specialist imaging investigates vertebral-level distribution. Clinicians should use each measure for the question it can answer.
What did the researchers investigate?
Craig Kage and colleagues aimed to quantify cervical intervertebral kinematics in chronic neck pain. Routine clinical examination can describe global movement, symptoms and visible movement quality, but it cannot directly show how much each vertebral level contributes during a dynamic task.
Twenty-three adults took part: 13 with chronic neck pain and 10 controls. Each completed three seated trials of flexion-extension, lateral bending and axial rotation inside a custom biplane videoradiography system. The system combined synchronised radiographic imaging with optical motion capture.
CT-based models of the vertebrae were matched to the moving images. The researchers derived motion across C4-C7 and considered head-to-C4 and global head-to-torso movement. They examined total ROM, the percentage contribution of each relationship to the global movement and trial-to-trial variability.
This is highly specialised measurement. It is designed to answer a research question that cannot be answered from a standard goniometer, head-mounted inertial sensor or visual examination.
What did the study find?
During axial rotation, participants with chronic neck pain showed reduced total motion and a smaller percentage contribution at C5-6 compared with controls. At the same time, their head-to-C4 relationship contributed more to the global rotation.
During flexion-extension, the neck-pain group showed a greater contribution at C4-5. They also showed greater trial-to-trial variability in the percentage contribution of head-to-C4 motion. No group differences were observed during lateral bending.
The authors described this as a pattern of localised motion deficit with redistribution or compensatory mobility elsewhere. That is a plausible biomechanical interpretation of the group findings, but it should not be converted into a clinical diagnosis for an individual patient.
Why a global angle cannot reveal local contribution
Imagine two people who both rotate the head through the same overall angle. The total can be identical while the contribution from individual cervical levels differs. One person may distribute movement relatively evenly; another may contribute less at one level and more elsewhere.
A global ROM measure reports the combined result. It cannot identify which joint moved, the sequence of segmental motion or whether a particular level compensated. That is not a failure of global measurement—it is simply the boundary of the construct.
Segment-level imaging has the opposite trade-off. It can resolve local kinematics, but it requires specialist equipment, radiation exposure, CT-derived models and substantial analysis. It is not a routine clinic tool and this study does not establish that using it improves management or outcomes.
Practical takeaways for clinicians
1. Be precise about what ROM represents
Global active ROM describes the total angular movement produced under a defined protocol. It does not localise motion to one vertebral segment.
2. Record visible movement quality separately
Alongside the angle, note thoracic or shoulder substitution, deviation from the intended plane, symptom behaviour, hesitation and repeatability where relevant. These observations add context, but they still do not provide direct segment-level measurement.
3. Compare like with like
The paper found different patterns by movement plane. No group difference appeared in lateral bending. Standardise the movement, instructions, position and number of trials rather than assuming one finding applies across all directions.
4. Avoid segment-specific conclusions from a head trace
A global trace or sensor cannot show that C5-6 is restricted or that an upper segment is compensating. Such a claim would go beyond the measurement.
5. Keep laboratory findings in proportion
This was a 23-person exploratory study. It can generate useful hypotheses about how chronic neck pain and motion distribution relate, but it cannot establish a universal pattern, causal mechanism or treatment target.
Where HeadX measurement fits
HeadX Duo is designed to record global head and neck movement, including active cervical ROM, when used with a consistent protocol. That can support repeatable documentation of the total movement and its change over time.
It does not image individual vertebrae and cannot reproduce biplane videoradiography. Neither Duo nor Kross should be described as identifying C5-6 motion, segmental compensation or an intervertebral cause of pain. The featured study did not evaluate HeadX.
The connection is therefore conceptual: global and segment-level measures describe different layers of movement. A global measurement can remain clinically useful when its boundary is made explicit and it is interpreted alongside symptoms, function and the wider examination.
Important limitations
The study included only 13 people with chronic neck pain and 10 controls. Small samples are particularly vulnerable to unstable estimates and limited generalisability. The selected participants, laboratory setup and analysed levels may not represent other neck-pain populations or everyday movement.
The design was cross-sectional. It cannot show whether the altered motion distribution preceded pain, developed in response to pain or reflected another factor. The study did not test an intervention, prognosis or patient outcome. It also did not validate clinical palpation, observational segmental diagnosis or a simpler sensor-based substitute for imaging.
In summary
A whole-neck ROM value is the sum of movement distributed across multiple cervical relationships. This small biplane-videoradiography study suggests that adults with chronic neck pain may distribute selected movements differently, including reduced C5-6 axial rotation with greater contribution elsewhere. It is an intriguing biomechanical finding—not a diagnostic rule. Clinicians can use global ROM well by recording it consistently, describing movement quality separately and resisting segment-level conclusions that the measurement cannot support.
Suggested internal links
References
- Kage CC, Abbott RE, MacEwen M, et al. Altered cervical intervertebral motion in chronic neck pain: evidence from biplane videoradiography. Journal of Electromyography and Kinesiology. 2026;89:103163. PubMed
This article is written for qualified clinical professionals. It is educational and does not constitute medical advice. The featured study did not evaluate HeadX or establish the clinical performance of a HeadX product.