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Building blocks of the KineGraph VMA
The KineGraph VMA employs strategies that have shown significant reduction in measurement variability associated with end-range x-rays, patient motion standardization (via the Motion Normalizer™ devices) and automated image analysis.
Motion Normalization
In a study by Dvorak and Panjabi, et al., an assistant applied a constant force to the bending subject to achieve the maximum bending angle.1 This resulted in a 36% reduction in variability when compared to the mean standard deviation found in similar studies.2
Wong, et al. used fluoroscopy to capture images of subjects as they moved through trunk bending.3 An electro-goniometer was used to trigger the capturing of the fluoro images at every 10° of trunk bending, thus standardizing the angles at which the images were taken. The resulting images were then analyzed using imaging software. The combination of using standardized bending angles and automated image analysis resulted in overall 72% reduction in intervertebral variability found in a meta-analysis of similar studies.2
Automated image analysis
Wong, et al. published two datasets of normative values, one dataset that was derived manually, and a second dataset that was derived using automated software image processing algorithms.3,4 Both datasets were measured from active flexion extension bending of the lumbar spine. The average standard deviation across the levels measured in this study decreased over 50%, from 2.8° to 1.3°. Reitman, et al. published a cervical IVA dataset of 155 asymptomatic subjects that was derived using an automated software process (QMA software from Medical Metrics, Inc., Houston, Texas).5 The study reported an average standard deviation across cervical levels of 4.0° which is lower than 5.0°, the average value found in a meta-analysis of similar studies.2
- Dvorak J, Panjabi MM, Noventoy JE, Chang DG, Grob D: 1. Clinical Validation of Functional Flexion-Extension Roentgenograms of the Lumbar Spine. Spine 1991;16(8):943-950
- Deitz AK, Breen AC, Mellor FE, Teyhen DS, Wong KWN, Panjabi MM. Kinematics of the aging spine: A Review of Past Knowledge and Survey of Recent Developments, with a Focus on Patient-Management Implications for the Clinical Practitioner, In The Comprehensive Treatment of the Aging Spine: Minimally Invasive and Advanced Techniques (eds. by Yue, Guyer, Johnson, Khoo, Hochschuler) Elsevier, in press.
- Wong, KWM et al. Continuous Dynamic Spinal Motion Analysis. Spine 2006; 31(4), pp. 414-419
- Wong, KWM, et al. The Flexion/Extension Profile of 100 Healthy Volunteers. Spine 2004; 29(15):1636-1641
- Reitman, et. al. Intervertebral Motion Between Flexion and Extension in Asymptomatic Individuals. Spine 2004;29(24):2832-2843
