Disk Area Is a More Reliable Measurement Than Anteroposterior Length in the Assessment of Lumbar Disk Herniations: A Validation Study.

STUDY DESIGN

Retrospective study.

OBJECTIVE

The goal of this study is to identify and validate the reliability and accuracy of 2 methods used to assess lumbar disk herniations (LDHs): anteroposterior length and cross-sectional area.

BACKGROUND

Many clinicians characterize LDHs through the measurement of the anteroposterior length in the axial plane. Radiologists, on the other hand, have utilized software to measure the disk and canal areas to define the injury. In this study, the authors consider the reliability and accuracy of anteroposterior length in comparison with the area.

METHODS

Using International Classification of Diseases, 10th Revision (ICD-10) code M51.26, patients at a single academic medical center who received a diagnosis of primary lumbar radicular pain with subsequent magnetic resonance imaging documentation of a single-level disk herniation in 2015 and 2016 were identified. AGFA-IMPACS software was utilized to make the following measurements: anterior-posterior canal length; anterior-posterior disk length; mid-canal width; mid-disk width; total canal area; total disk area. Data analysis was conducted in SPSS and a 2-tailed reliability analysis using Cronbach alpha as a measure of reliability was obtained.

RESULTS

A total of 408 patients met the inclusion and exclusion criteria for this study. Sixteen (3.9%) had L3-L4 herniation, 208 had L4-L5 herniation (51.0%), and 184 had L5-S1 herniation (47.5%). The least reliable interobserver metrics, with respective Cronbach alpha values of 0.381 and 0.659, were the linear measurements of mid-disk width and anterior-posterior canal length. Area measurements of the disk and canal areas generated Cronbach alpha values of 0.707 and 0.863. Intraobserver Cronbach alpha values for all measurements, including all areas and lengths, met or exceeded 0.982.

CONCLUSIONS

The cross-sectional area provides a more reliable measurement modality for diskLDHs in comparison to linear measurements. Unlike anteroposterior length, cross-sectional area incorporates the shape of a herniation or canal in its measurement. Thus, it is superior in its characterization LDH particularly in light of its stronger reproducibility.

LEVEL OF EVIDENCE

Level III-retrospective study.