Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Oct;8(5):893-899.
doi: 10.1007/s43390-020-00137-x. Epub 2020 Jun 3.

Mandibular slope: a reproducible and simple measure of horizontal gaze

Stephen George  1 , Matthew Spiegel  2 , Themistocles Protopsaltis  2 , Aaron J Buckland  2 , Jaime A Gomez  3 , Subaraman Ramchandran  1 , Renaud Lafage  4 , Virginie Lafage  4 , Thomas Errico  1 , Baron Lonner  5
Affiliations

Mandibular slope: a reproducible and simple measure of horizontal gaze

Stephen George et al. Spine Deform. 2020 Oct.

Abstract

Study design: This study is a single-center retrospective radiographic review.

Objectives: The objective of this study is to evaluate a novel measurement parameter, mandibular slope (MS), as a measure of horizontal gaze.

Introduction: Assessment of sagittal spinal alignment is essential in the evaluation of spinal deformity patients. Ability to achieve a horizontal gaze, a parameter of sagittal alignment, is needed for the performance of daily activities. Standard measures of horizontal gaze, including the gold-standard chin-brow to vertical angle (CBVA) and the surrogate measures McGregor's line (McGS) and Chamberlain's line (CS), require high-quality imaging, precise head positioning, and reliance on difficult to view visual landmarks. A novel measurement parameter, MS, utilizing the caudal margin of the mandible on standard lateral spine radiographs is proposed.

Methods: 90 radiographs from spine deformity patients with or without spinal implants from a single center were evaluated. Three spine surgery fellows independently measured CBVA, McGS, CS, and MS at two timepoints at least one week apart to assess accuracy and reliability. MS was measured as the angle created by the inferior edge of the mandibular body and the horizontal. Formulas for calculating CBVA based on the above parameters were derived and compared to the actual CBVA.

Results: Mean age was 49.7 years, 76 females and 14 males. CBVA correlated with CS, McGS, and MS, r = 0.85, 0.81, and 0.80, respectively (p < 0.001). Standard error between real CBVA and calculated CBVA using CS (0.4 ± 4.79) and McGS (0.4 ± 3.9) was higher than that calculated using MS (- 0.2 ± 4.3). ICC demonstrated the highest inter-observer reliability with MS (0.999). MS had the highest intra-observer reliabilities 0.975, 0.981, and 0.988 (p < 0.001); CS and McGS also demonstrated high intra-observer reliability.

Conclusions: MS is a promising measure of horizontal gaze that correlates highly with CBVA, has excellent intra- and inter-observer reliability with CBVA, and is easily measured using standard lateral spine radiographs.

Keywords: Horizontal gaze; Mandibular slope; Novel measurement parameter; Sagittal spinal alignment.

PubMed Disclaimer