Reliability and Reproducibility of CT-Based Facet Joint Measurements in Patients With AOSpine Type A2, A3, and A4 Thoracolumbar Fractures

Reliability and Reproducibility of CT-Based Facet Joint Measurements in Patients With AOSpine Type A2, A3, and A4 Thoracolumbar Fractures

The Reliability Evaluation of Facet joint Assessment by Computed Tomography in thoracolumbar fractures (REFACT) study aims to evaluate how consistently different specialists assess thoracolumbar facet joints on computed tomography (CT) images in patients with AOSpine type A2, A3, or A4 thoracolumbar fractures.

The main questions are:

• How consistently do different raters classify facet joint degeneration using the Pathria grading system?
• How consistently do different raters measure facet joint angle and mean facet joint space width on CT images?
• How reproducible are these assessments when the same rater repeats the measurements after a one-month interval?

The study will use anonymized retrospective CT DICOM datasets obtained from the institutional imaging archive. Six independent raters (three neurosurgeons and three radiology specialists) will evaluate the same CT datasets using a standardized measurement protocol. Each rater will perform two independent assessment rounds separated by a one-month washout period. The results will be used to determine the inter-rater and intra-rater reliability of qualitative and quantitative CT-based facet joint assessment methods.

The Reliability Evaluation of Facet joint Assessment by Computed Tomography in thoracolumbar fractures (REFACT) study is an imaging-based, multirater reliability study designed to evaluate the reproducibility of computed tomography-based assessment of thoracolumbar facet joints.

The study represents the methodological stage of a broader research program investigating longitudinal degenerative changes in the facet joints after surgical or conservative treatment of thoracolumbar fractures. Before changes in facet joint morphology can be interpreted over time, the reliability of the imaging assessment methods must first be established in the target patient population.

Anonymized CT DICOM datasets will be selected from the institutional imaging archive of the Sklifosovsky Research Institute for Emergency Medicine. The datasets will include patients with AOSpine type A2, A3, or A4 thoracolumbar junction fractures and will cover the anatomical levels required for standardized facet joint assessment. No additional imaging, patient contact, study-specific treatment, or prospective clinical intervention will be performed.

Six independent raters will participate in the study: three neurosurgeons and three specialists in radiology or CT imaging. All raters will use the same standardized assessment protocol and the same DICOM viewing software.

Before the formal assessment, the raters will participate in a joint training session using one representative anonymized CT dataset that will not be included in the main analysis. The session will be used to demonstrate the assessment procedure, standardize image orientation and vertebral level identification, clarify the interpretation of the Pathria grading system, and review the procedures for measuring facet joint angle and facet joint space width. Any ambiguities in the assessment instructions will be resolved before the formal study begins.

During the first assessment round, each rater will independently evaluate the same anonymized CT datasets. The order of the datasets will be randomized separately for each rater. Raters will record the Pathria grade of facet joint degeneration and quantitative facet joint measurements according to the standardized protocol.

After a one-month washout interval, the same CT datasets will be re-randomized and reassessed independently by the same six raters during a second assessment round. The changed order and washout period are intended to reduce recall bias and allow evaluation of the reproducibility of repeated assessments by the same rater.

Throughout both assessment rounds, raters will be blinded to patient identifiers, clinical information, previous measurements, and the assessments of the other raters. Raters will not discuss individual study cases or measurement decisions until both rounds have been completed.

The study will evaluate agreement across different raters and the consistency of repeated assessments by the same rater. The assessment will include both ordinal grading of facet joint degeneration and continuous morphometric measurements. Exploratory analyses may examine whether reliability differs according to rater specialty, vertebral level, or anatomical side.

All study data will be entered into a standardized data collection form and stored in a restricted-access institutional database. Missing, technically inadequate, or non-evaluable assessments will not be imputed and will be reported descriptively.

Because the study uses only previously acquired, anonymized imaging data, participants will not undergo any study-related procedures and will not be exposed to additional radiation or treatment-related risk.

Inclusion Criteria:

• patient age from 18 to 50 years;
• thoracolumbar fracture classified as AOSpine type A2, A3, or A4;
• availability of CT images covering vertebral levels from Th9 to L3;
• absence of imaging artifacts at the levels planned for assessment.

Exclusion Criteria:

• bone density of the thoracolumbar junction vertebrae below 100 HU;
• systemic bone or joint disorders associated with changes in the FJs or intervertebral discs, including diffuse idiopathic skeletal hyperostosis, ankylosing spondylitis, rheumatoid arthritis, or other comparable conditions;
• previous spinal surgery, including procedures performed without implants;
• fractures with distraction or translational injury of the posterior supporting column.