Spinal Instability Quantification via Translation Per Degree of Rotation
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Solution Overview
Problem
Current methods for diagnosing spinal instability are unreliable, inaccurate, and lack a standard, objective measure, making it difficult to differentiate between normal and abnormal spinal motion, especially due to variability between levels and patient effort, and are not suitable for routine clinical practice.
Innovation Solution
A method that calculates the translation per degree of rotation (TPDR) independent of vertebrae size, using x-ray films to measure intervertebral rotation and translation, and applies a standardizing formula to generate a stability metric as a number of standard deviations from an asymptomatic population, allowing for objective quantification of spinal instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If simple radiographs in two or more different positions are used to assess motion in the spine, then the method is inexpensive and readily obtainable in a physician's office, but the method is highly unreliable and trained clinicians not infrequently disagree regarding how to interpret the assessed motion
Solution Approach 1:
The patent transforms qualitative visual assessment into quantitative measurement by calculating translation per degree of rotation (TPDR). This parameter change converts subjective clinician interpretation into an objective numerical value that can be reliably compared across patients and clinicians, resolving the reliability issue while maintaining the simplicity of using standard radiographs
Solution Approach 2:
The patent replaces the mechanical/visual assessment system with a computational system. By using software to automatically calculate TPDR from radiograph measurements, the method eliminates inter-clinician variability and provides consistent, reliable results while maintaining ease of data acquisition through standard imaging
2Measurement precision
If rotation and translation metrics are used to diagnose spinal instability, then objective measurements can be obtained, but significant variability between levels and individuals makes it exceedingly difficult to classify measurements as normal or abnormal
Solution Approach 1:
The patent changes the diagnostic parameter from absolute rotation or translation values to the ratio of translation per degree of rotation (TPDR). This normalization accounts for variability between spinal levels and individuals, allowing objective classification of measurements as normal or abnormal while maintaining the objectivity of quantitative measurement
Solution Approach 2:
The patent creates an equipotential diagnostic framework by establishing normal TPDR ranges that account for natural variability across different spinal levels and patient populations. This allows the same diagnostic criterion to be applied universally across all levels and individuals, resolving the adaptability issue while maintaining measurement precision
3Measurement precision
If patients are required to move as much as the asymptomatic population to ascertain asymptomatic movement, then true motion can be captured, but people with back pain often make less effort than may be required to diagnose spinal instability
Solution Approach 1:
The patent changes from measuring absolute motion values to measuring the ratio of translation per degree of rotation (TPDR). This parameter transformation allows for accurate assessment of spinal instability even when patients cannot achieve full range of motion, as the ratio remains valid for detecting abnormal coupling between translation and rotation at reduced motion amplitudes
Data Source
Figure 1
AI summary
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.