General Session: Diagnostic Imaging

Presented by: J. Hipp

Author(s):

J. Hipp(1), O. Avila-Montes(1), P. Newman(1)

(1) Medical Metrics, Research & Development, Houston, TX, United States

Abstract

Introduction: Controlled intervertebral motion (IVM) is required for asymptomatic activities of daily living. Abnormal IVM is potentially treatable but requires a reliable diagnostic test to identify the specific abnormality. Substantial improvements in treatment outcomes may be achievable by using reliable tests for abnormal IVM for optimal treatment selection. Many prior studies document wide variability in IVM due to the dependency on how a person flexes and extends when the radiographs are obtained. A standardized flexion/extension (F/E) protocol has yet to be established, and this may limit progress toward achieving improved clinical outcomes. A very simple upright load-bearing protocol requiring no specialized equipment (only a standard walker), and that is supported by online training videos (https://www.youtube.com/watch?v=7VLlVsbYJcA & https://youtu.be/Day_wvEG-yI), is now available. The goal of the research was to develop asymptomatic reference data for IVM measured from F/E radiographs obtained using the new protocol.

Methods: After signing informed consent, and watching the patient training video, 193 asymptomatic volunteers flexed and extended from a standing position using a walker for support while radiographs were obtained of their lumbar spine. Previously validated computer-assisted software was used to measure IVM (QMA®). Descriptive statistics were generated and compared to IVM data from a previously published study of 161 asymptomatic volunteers where F/E was performed from a seated position. A > 5 deg of intervertebral rotation criteria was used to classify each level as having been sufficiently stressed to reliably measure IVM metrics such as center-of-rotation, translation per degree of rotation and change in disc height per degree of rotation.

Results: 63 males (age 39±14 yrs) and 135 females (age 42±12 yrs) consented to the study. 95% of the intervertebral levels had > 5 deg of rotation. Compared to seated F/E, there is substantially greater motion at the L4-L5 and L5-S1 levels using the standing with walker F/E protocol. Variability in intervertebral rotation was not associated with height, weight, BMI, or sex (P>0.1). Intervertebral rotation tended to decrease with age, although the strength of that association was weak (R2< 0.2). Some IVM metrics were dependent on the F/E protocol while others were not. Discussion/

Conclusions: Analogous to other diagnostic tests intended to detect functional abnormalities (eg the knee drawer test), the mechanical integrity of the soft-tissues that should be controlling IVM cannot be reliably assessed unless the spine is stressed to a level where IVM would normally be constrained by soft-tissues. The medical expense and exposure to ionizing radiation to perform a spine F/E test is unjustified if the spine is not stressed adequately to diagnose incompetent IVM restraints. Preliminary evidence supports that if F/E tests adequately stress the spine, they can be used to help select the best treatment option. The results of the current study support that by educating both technicians and patients on how to flex and extend, and using a walker to provide balance and minimize rotation at the hip joint, the spine can be stressed adequately to identify IVM abnormalities. The current study provides the required normative reference data. The next step toward clinical validation of a standardized F/E method is deployment in a symptomatic population.