Cervical Lordosis: Imaging Position and Measurement (CLIP-M)

April 30, 2026 updated by: Berkan Basançelebi, Medipol University

Position- and Measurement-Dependent Differences in Cervical Lordosis: A Comparative Analysis of Standing Radiographs and Supine MRI

This retrospective cross-sectional study aims to compare cervical lordosis measurements obtained from standing lateral radiographs and supine magnetic resonance imaging (MRI) in individuals without structural cervical pathology. The study also evaluates the independent contribution of T1 slope to cervical alignment and investigates whether imaging modality significantly alters measured lordosis values.

Study Overview

Status

Active, not recruiting

Conditions

Intervention / Treatment

Detailed Description

Cervical lordosis is a key determinant of sagittal spinal alignment and plays a critical role in maintaining horizontal gaze, biomechanical efficiency, and overall spinal balance. Accurate assessment of cervical alignment is essential for clinical decision-making, particularly in the evaluation of degenerative conditions, deformity, and surgical planning. However, despite its clinical importance, there remains substantial variability in both the measurement techniques and the reported normative values of cervical lordosis.

Among the available measurement methods, the Cobb technique and the posterior tangent method are the most commonly used approaches. While the Cobb method provides a global estimate of cervical curvature, the posterior tangent method allows for a more segmental analysis. Nevertheless, these techniques may yield significantly different results even within the same patient, contributing to inconsistency across studies. Furthermore, the absence of a universally accepted standard complicates comparisons between studies and limits the generalizability of findings.

One of the most important determinants of cervical lordosis is the T1 slope, defined as the angle between the superior endplate of the T1 vertebra and the horizontal plane. The T1 slope has been shown to function analogously to pelvic incidence in the lumbar spine, serving as a morphological parameter that dictates the required degree of cervical lordosis for maintaining sagittal balance. Several studies have demonstrated a strong linear relationship between T1 slope and cervical lordosis, suggesting that cervical curvature is largely T1 slope-dependent. This relationship has led to the development of predictive models for estimating ideal cervical lordosis based on T1 slope values.

Despite this established biomechanical relationship, another critical factor influencing cervical alignment is patient positioning during imaging. It is well recognized that standing radiographs and supine magnetic resonance imaging (MRI) produce systematically different measurements of cervical lordosis. Under weight-bearing conditions, the cervical spine adopts a more lordotic configuration to maintain head posture and balance, whereas in the supine position, the loss of axial loading leads to a relative reduction in lordosis. Previous studies have shown that MRI tends to underestimate cervical lordosis compared to standing radiographs, with reported differences ranging between 2° and 6° depending on the measurement technique and patient population.

However, most of the existing literature on imaging-related differences in cervical alignment has been conducted in populations with degenerative cervical pathology, such as cervical spondylotic myelopathy. These pathological conditions may introduce confounding factors, including stiffness, pain-related muscle guarding, and structural deformity, which can alter the natural biomechanical relationship between T1 slope and cervical lordosis. Consequently, the extent to which imaging modality alone influences cervical alignment in individuals without structural pathology remains incompletely understood.

Furthermore, although previous studies have demonstrated both (1) a strong association between T1 slope and cervical lordosis and (2) systematic differences between imaging modalities, these two aspects have rarely been evaluated together within a single analytical framework. In particular, there is a lack of studies that quantify the independent contribution of imaging modality after adjusting for T1 slope using multivariable regression analysis. This gap limits the ability to interpret MRI-based measurements in clinical practice and raises questions regarding the comparability of measurements obtained using different imaging techniques.

The present study aims to address this gap by evaluating cervical alignment in a cohort of individuals without structural cervical pathology, thereby minimizing confounding factors related to degenerative or deformity-related changes. Cervical lordosis is assessed using Cobb-based measurements (C1-C7 and C2-C7), which are widely accepted as clinically relevant parameters. The primary objective is to compare cervical lordosis values obtained from standing lateral radiographs and supine MRI. The secondary objective is to determine the independent effects of T1 slope and imaging modality on cervical lordosis using multivariable linear regression analysis.

In addition to group comparisons, a multivariable linear regression model will be constructed to evaluate the independent contributions of T1 slope and imaging modality to cervical lordosis measurements. Cervical lordosis (C2-C7 and C1-C7 Cobb angles) will be used as dependent variables, while T1 slope (continuous variable) and imaging modality (binary variable: supine MRI vs standing radiograph) will be included as independent predictors.

This modeling approach allows for quantification of the extent to which imaging modality influences cervical lordosis independently of underlying biomechanical alignment. Furthermore, the regression model provides a predictive framework for estimating cervical lordosis based on T1 slope and imaging conditions, addressing the lack of standardized conversion between supine MRI and standing radiographic measurements reported in the literature.

It is hypothesized that:

  1. Cervical lordosis measurements obtained from supine MRI are significantly lower than those obtained from standing radiographs, and
  2. Imaging modality has an independent effect on cervical lordosis measurements even after adjusting for T1 slope.

By integrating biomechanical parameters with imaging modality effects, this study aims to provide a more comprehensive understanding of cervical sagittal alignment and to contribute to the development of clinically applicable models for interpreting MRI-based measurements. Ultimately, these findings may help improve the accuracy of preoperative planning and the interpretation of cervical spine imaging in both research and clinical settings.

This study has been designed, conducted, and will be reported in accordance with the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) statement. As the study utilizes retrospectively collected routine clinical imaging data, additional adherence to the RECORD (REporting of studies Conducted using Observational Routinely-collected health Data) guidelines is ensured.

Sample size considerations were informed by previously reported differences in cervical sagittal alignment across imaging modalities and positions. Prior studies have demonstrated that differences in cervical lordosis between radiographic and MRI-based measurements may range from small to large, depending on imaging conditions and patient positioning. Considering this variability, a conservative moderate-to-large standardized effect size (Cohen's d = 0.75) was assumed for sample size estimation. Based on this assumption, a total sample size of 58 participants (29 per group) was considered sufficient to detect clinically meaningful differences between groups at a significance level of 0.05 with a statistical power of approximately 80%, while acknowledging that smaller effects may remain underpowered.

Descriptive statistics will be reported as mean ± standard deviation for continuous variables and count (percentage) for categorical variables. Normality will be assessed using the Shapiro-Wilk test. Between-group comparisons will be performed using independent-samples t test or Mann-Whitney U test, as appropriate. Sex distribution will be compared using the chi-square test or Fisher exact test, where appropriate. The primary analytical framework will include multivariable linear regression models with Cobb C2-C7 and Cobb C1-C7 angles as dependent variables and T1 slope and imaging modality as independent variables. Statistical significance will be defined as p < 0.05. All statistical analyses will be conducted using jamovi version 2.6.44 and RStudio version 2025.09.2.

Study Type

Observational

Enrollment (Estimated)

58

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Adults aged 18-65 years with clinically obtained standing cervical radiographs or supine cervical MRI during the registry period and without structural cervical pathology affecting alignment.

Description

Inclusion Criteria:

  • Adults aged 18 to 65 years
  • Availability of standing lateral cervical radiograph or supine cervical MRI performed during the registry period
  • No structural cervical pathology affecting sagittal alignment
  • Images of adequate quality for radiographic measurement
  • Neutral standing radiograph position for Standing Radiograph Group
  • Standard supine acquisition for Supine MRI Group

Exclusion Criteria:

  • Prior cervical spine surgery
  • Cervical fracture, dislocation, or whiplash history
  • Primary or metastatic cervical malignancy
  • Congenital vertebral anomaly including Klippel-Feil syndrome, os odontoideum, hemivertebra, block vertebra, or atlantoaxial instability
  • Spinal deformity or postural disorder likely to affect cervical alignment, including scoliosis, hyperkyphosis, or Scheuermann disease
  • Advanced degenerative cervical disease, including severe spondylosis, cervical spinal stenosis, OPLL, or DISH
  • Inflammatory or autoimmune rheumatologic disease affecting the spine
  • Neuromuscular or neurologic disorders affecting posture or alignment
  • Inadequate image quality, major artifact, or improper positioning

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Standing Radiograph Group
Individuals with standard lateral cervical radiographs obtained in the upright neutral standing position.
Other: No intervention
This is an observational study with no assigned intervention. Groups are defined based on the imaging modality (standing radiograph vs supine MRI).
Supine MRI Group
Individuals with standard cervical magnetic resonance imaging obtained in the supine position.
Other: No intervention
This is an observational study with no assigned intervention. Groups are defined based on the imaging modality (standing radiograph vs supine MRI).

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Difference in Cobb C2-C7 angle between standing radiographs and supine MRI
Time Frame: Baseline retrospective image assessment
Cobb C2-C7 angle measured using standard endplate-based methodology on standing lateral cervical radiographs and supine cervical MRI. The primary comparison evaluates the difference in cervical lordosis between imaging modalities obtained under weight-bearing and non-weight-bearing conditions.
Baseline retrospective image assessment
Difference in Cobb C1-C7 angle between standing radiographs and supine MRI
Time Frame: Baseline retrospective image assessment
Cobb C1-C7 angle measured on standing lateral radiographs and supine MRI using standard radiographic techniques. This outcome assesses global cervical lordosis differences between imaging modalities.
Baseline retrospective image assessment

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Association between T1 slope and Cobb C2-C7 angle
Time Frame: Baseline retrospective image assessment
The relationship between T1 slope and Cobb C2-C7 angle will be evaluated using correlation and regression analyses. This outcome assesses the biomechanical dependence of cervical lordosis on T1 slope.
Baseline retrospective image assessment
Association between T1 slope and Cobb C1-C7 angle
Time Frame: Baseline retrospective image assessment
The relationship between T1 slope and Cobb C1-C7 angle will be analyzed to evaluate the influence of T1 slope on global cervical alignment.
Baseline retrospective image assessment
Multivariable linear regression model for Cobb C2-C7
Time Frame: Baseline retrospective image assessment
A multivariable linear regression model will be constructed with Cobb C2-C7 angle as the dependent variable. Independent variables will include T1 slope (continuous), imaging modality (binary: supine MRI vs standing radiograph), and sex (male vs female). An interaction term between imaging modality and sex (Group × Sex) will be included to evaluate whether the effect of imaging modality differs according to sex.
Baseline retrospective image assessment
Multivariable linear regression model for Cobb C1-C7
Time Frame: Baseline retrospective image assessment
A multivariable linear regression model will be constructed with Cobb C1-C7 angle as the dependent variable. Independent variables will include T1 slope, imaging modality, and sex. The model will also include an interaction term (Group × Sex) to assess potential effect modification.
Baseline retrospective image assessment
Effect of sex on cervical sagittal alignment
Time Frame: Baseline retrospective image assessment
Sex will be evaluated as an independent predictor of cervical alignment parameters (Cobb C2-C7 and Cobb C1-C7) within multivariable regression models.
Baseline retrospective image assessment
Interaction between sex and imaging modality
Time Frame: Baseline retrospective image assessment
The interaction between sex and imaging modality will be assessed to determine whether the difference in cervical lordosis between standing radiographs and supine MRI varies according to sex.
Baseline retrospective image assessment

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
Difference in posterior tangent C2-C7 angle between standing radiographs and supine MRI
Time Frame: Baseline retrospective image assessment
Posterior tangent C2-C7 angle measured using vertebral posterior border tangential lines. This exploratory outcome compares segmental cervical alignment between imaging modalities.
Baseline retrospective image assessment
Association between T1 slope and posterior tangent C2-C7 angle
Time Frame: Baseline retrospective image assessment
The relationship between T1 slope and posterior tangent C2-C7 angle will be evaluated to determine whether segmental alignment follows similar biomechanical patterns as Cobb-based measurements.
Baseline retrospective image assessment
Multivariable linear regression model for posterior tangent C2-C7
Time Frame: Baseline retrospective image assessment
A multivariable regression model will be constructed using posterior tangent C2-C7 as the dependent variable, with T1 slope, imaging modality, and sex as predictors. An interaction term between imaging modality and sex (Group × Sex) will be included to evaluate effect modification across measurement techniques.
Baseline retrospective image assessment

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Medipol University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 1, 2025

Primary Completion (Actual)

January 1, 2026

Study Completion (Estimated)

June 1, 2026

Study Registration Dates

First Submitted

April 14, 2026

First Submitted That Met QC Criteria

April 14, 2026

First Posted (Actual)

April 21, 2026

Study Record Updates

Last Update Posted (Actual)

May 6, 2026

Last Update Submitted That Met QC Criteria

April 30, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • CLIP-M-001

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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