Lightning Podiums: Smorgasboard - Room 802B

Presented by: H.-K. Wong

Author(s):

H.W.D. Hey(1), K.-A. Tan(1), G.K.-P. Liu(1), H.-K. Wong(1)

(1) National University Hospital, Singapore, Singapore

Abstract

Purpose of the Study: Sagittal alignment of the spine is important for maintaining horizontal gaze, and is therefore essential for determining surgical correction. However, horizontal gaze remains poorly-defined from a radiological point-of-view. This study aims to establish the radiographic criteria for horizontal gaze. Describe the methods used: This prospective study was conducted at a tertiary healthcare institution over a 1-month period. It includes healthy patients to determine the best radiological criteria for defining horizontal gaze. Two categories of radiographic parameters for determining horizontal gaze were tested: (1) the vertical offset distances of key identifiable structures from the horizontal gaze axis; and (2) imaginary lines convergent with the horizontal gaze axis. Sixty-seven healthy subjects underwent whole body radiographs taken in a directed standing posture. Horizontal gaze was radiographically defined using each parameter, as represented by their means, 95% confidence intervals (CI) and associated two standard deviations (SD). A retrospective cohort (prior to the implementation of strict radioimaging standardization) of patients without rigid spinal deformities was then used to audit the prevalence of horizontal gaze using the selected radiographic criteria. Summarize the

Findings: The mean age of our prospective cohort was 46.8 years while that of our retrospective cohort was 37.2 years. Gender was evenly distributed across both cohorts. The 4 parameters with the lowest 95% CI and 2SD were the distance offsets of the midpoint of the hard palate (A), and the base of the sella turcica (B), as well as the horizontal convergents formed by the tangential line to the hard palate (C), and the line joining the centre of the orbital orifice with the internal occipital protuberance (D). In the prospective cohort, good sensitivity (>98%) was attained when two or more parameters were used. Audit using criteria B+D yielded compliance rates of 76.7% - a figure much closer to that of A+B+C+D (74.8%). From a practical viewpoint, criteria B+D is most suitable for clinical use, and can be simplified to the "3-6-12 rule" as a form of cursory assessment. The retrospective cohort demonstrated that verbal instructions in the absence of stringent postural checks only ensured that ~75% of subjects achieved horizontal gaze. Include statement of

Conclusions: Fulfilment of criteria B+D is sufficient to evaluate for horizontal gaze. Further criteria can be added to increase sensitivity. Verbal instructions alone yield high rates of inaccuracy when attempting to image patients in horizontal gaze. Apart from improving methods for obtaining radiographs, a radiological definition of horizontal gaze should be routinely applied for better evaluation of sagittal spinal alignment.