Methods for determining spine instability and for eliminating the impact of patient effort on stability determinations
Inventors
Hipp, John A. • Wharton, Nicholas
Assignees
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Publication Number
US-9554764-B2
Publication Date
2017-01-31
Expiration Date
Abstract
The present disclosure describes a method for determining spinal instability, more particularly, a method for quantifying the type and extent of spinal instability in a standardized way. The disclosure also describes a method comprising measurement of the intervertebral rotation and intervertebral translation between a vertebrae pair using simple images, and from these measurements, determining if one or more vertebrae pair of the spine is unstable. Finally, the disclosure describes software that may be used to quantify the type and extent of spinal instability.
Core Innovation
The disclosed invention provides a method for detecting injuries or structural degeneration of the disc, facet joints or intervertebral ligaments of the spine using flexion-extension X-ray imaging. The method obtains an X-ray image of a first and a second vertebrae in a flexed position and obtains an X-ray image of the same vertebrae in an extended position. The approach aligns the first vertebrae and determines the rotation and translation required to align the second vertebrae between positions.
The method measures the change in disc height between the flexed position and the extended position, and converts this change into a spinal displacement per degree of rotation metric. Specifically, it divides the change in disc height by the rotation to give spinal displacement per degree of rotation (DPDR). The invention further standardizes and interprets DPDR using normative reference data derived from an asymptomatic radiographically normal population.
The method compares the DPDR to a standard to determine whether the DPDR is within normal limits for the same first and second vertebrae along the spine, and can express instability as a stability metric using a vertebra-pair-specific standardizing factor. The document also describes creating trait-specific normative data by dividing normative data for the entire asymptomatic population into trait-specific normative data based on a spinal characteristic distinguished from the entire population.
Claims Coverage
The document includes two independent claims. The inventive features center on flexion-extension X-ray imaging of a vertebra pair, alignment to determine rotation, disc-height change measurement, computation of DPDR, and use of normative group construction or comparison to establish within-normal-limits determinations and trait-specific standards.
Flexion-extension disc-height change divided by rotation to give DPDR
obtaining an x-ray image of a first and a second vertebrae in a flexed position; obtaining an x-ray image of a first and second vertebrae in an extended position; aligning the first vertebrae and determining the rotation and translation required to align the second vertebrae; measuring the change in disc height between the flexed positon and extended position; and dividing the change in disc height by the rotation to give spinal displacement per degree of rotation (DPDR).
Creating trait-specific normative DPDR groups from an asymptomatic population
obtaining an x-ray image of a first and a second vertebrae in a flexed position from an asymptomatic population; obtaining an x-ray image of a first and second vertebrae in an extended position from the same population; aligning the first vertebrae and determining the rotation and translation required to align the second vertebrae; measuring the change in disc height between the flexed positon and extended position; dividing the change in disc height by the rotation to give spinal displacement per degree of rotation (DPDR); collecting data from the population to create normative data; and dividing the normative data for the entire asymptomatic population into trait-specific normative data, the population being divided based upon a spinal characteristic that can be distinguished from the entire population to create a trait specific subpopulation.
Overall claim coverage is directed to computing DPDR from disc-height change over rotation between flexed and extended X-ray positions of a first/second vertebra pair, and then using either standards derived from an asymptomatic radiographically normal population to determine within-normal limits or creating trait-specific normative data by dividing asymptomatic normative data based on a distinguishable spinal characteristic.
Stated Advantages
Enables determining whether the DPDR is within normal limits by comparison to a standard defined from measurements in asymptomatic, radiographically normal individuals.
Converts DPDR into a standardized stability metric expressed as the number of standard deviations relative to the metric in an asymptomatic radiographically normal sub-population.
Supports creating trait-specific normative data for a trait specific subpopulation using a spinal characteristic distinguishable from the entire population.
Allows comparison of trait-specific subpopulation data to symptomatic patient data to determine whether DPDR is within normal limits for the same first and second vertebra along the spine.
Documented Applications
Detecting injuries or structural degeneration of the disc, facet joints or intervertebral ligaments of the spine using flexion-extension X-ray imaging of vertebra pairs and computing DPDR.
Creating and using normative groups by dividing asymptomatic population normative data into trait-specific normative data based on a spinal characteristic distinguished from the entire population.
Evaluating stability/instability by comparing a patient’s DPDR or trait-specific DPDR data to within-normal-limits standards derived from asymptomatic radiographically normal populations, including trait-specific subpopulations.
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