Atlas of Spinal Imaging Phenotypes

Phenotypes, Measurements and Classification Systems

Philip Louie, Howard S. An, Dino Samartzis

• Publisher: Elsevier
• Year: 2021
• ISBN:
  9780323761123
• Topic: Medicine
• Subtopic: Radiology, Radiotherapy & Nuclear Medicine

Spine-related pain is the world's leading disabling condition, affecting every population and a frequent reason for seeking medical consultation and obtaining imaging studies. Numerous spinal phenotypes (observations/traits) and their respective measurements performed on various spine imaging have been shown to directly correlate and predict clinical outcomes.Atlas of Spinal Imaging Phenotypes: Classifications and Radiographic Measurementsis a comprehensive visual resource that highlights various spinal phenotypes on imaging, describes their clinical and pathophysiological relevance, and discusses and illustrates their respective measurement techniques and classifications.

• Helps readers better understanding spinal phenotypes and their imaging, and how today's knowledge will facilitate new targeted drug discovery, novel diagnostics and biomarker discovery, and outcome predictions.
  
  

• Features step-by-step instructions on performing the radiographic measurements with examples of normal and pathologic images to demonstrate the various presentations.
  
  

• Presents clinical correlation of the phenotypes as well as the radiographic measurements with landmark references.
  
  

• Includes validated classification systems that complement the phenotypes and radiographic measurements.
  
  

• Complies the knowledge and expertise of Dr. DinoSamartzis, thepreeminentglobal authority on spinal phenotypes who has discovered and proposed new phenotypes and classificationschemes;Dr. Howard S. An, a leading expert in patient management and at the forefront of 3D imaging of various spinal phenotypes; and Dr. Philip Louie, a prolific surgeon who is involved in one of the largest machine learning initiatives of spinal phenotyping.
  
  

Chapter 1: Introduction

Philip K. Louie^a; Dino Samartzis^b,c; Howard S. An^b,c    a Department of Neurosurgery, Virginia Mason Medical Center, Seattle, WA, United States
^b Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, United States
^c International Spine Research and Innovation Initiative (ISRII), Rush University Medical Center, Chicago, IL, United States

History of Spine Imaging

The idea of imaging to provide information on osseous anatomy dates back to 1895, when Wilhelm Conrad Roentgen demonstrated the existence and application of X-rays. Although introduced as a form of novel photography, physicians soon realized the medical utility of Roentgen’s discovery. X-rays rapidly developed into an invaluable diagnostic tool to image the spine by the early 1900s.¹ By the 1920s, practitioners discovered that they could manipulate adjacent tissue densities, resulting in differentiation between adjacent structures. In one scenario, Sicard and Forestier may have accidentally introduced an iodine-based solution into the epidural space when attempting to target a patient’s lumbar muscles (a technique considered as effective management for sciatica).² This experiment led to take radiographs after injections to evaluate for additional pathology, which subsequently led to the discovery that iodine enhances the anatomy of the spinal cord and subarachnoid space. Over the next few years, several improvements and innovations were described that improve the safety of these iodine-based contrast agents. Practitioners soon began to regularly inject these solutions into the dural sac and intervertebral discs.³

Due to limitations revolving around computing power, it would not be until 1973, when modern CT would emerge. Historians hypothesize that Dr. Godfrey Hounsfield conceived of CT in a thought experiment, where he reasoned it would be possible to identify the contents of a box by taking X-rays at every possible angle around it.⁴ He further extrapolated that there may be medical utility with this technique, specifically to identify human skull contents. Over the next few months, Dr. Hounsfield successfully produced the initial CT images of a patient’s brain and the original CT scanner was quickly adapted for full-body use, including the spine.⁵ Concurrently, around the same time, a chemist by the name of Paul Lauterbur was working heavily with nuclear magnetic resonance (NMR) spectroscopy. During his experiments, he conceived that the application of a magnetic field on a large object could produce images based on its chemical structure.⁶ This incredible theory laid the foundation for modern magnetic resonance imaging (MRI). MRI continued to evolve during the1970s, producing images with a low spatial resolution that advanced the discrimination of soft tissue proving superiority to CT, allowing earlier diagnoses. Furthermore, unlike CT, MRI had the advantage of not requiring ionizing radiation to produce high-resolution images. This accomplishment was eventually rewarded as a Nobel Prize in physiology and medicine.⁷ The technology quickly improved during the late 1980–1990s that resulted in high-resolution descriptions of spinal anatomy and pathology that were soon cleared for human use.^{8, 9}

Common Imaging Modalities

In today’s era, the imaging techniques continue to evolve, especially in the evaluation of spine anatomy. With the improved resolution of modern CT scanners, techniques such as myelography are not nearly as popular as they once were. Similarly, discography recommendations and indications have significantly narrowed due to increased rates of pain postoperatively induced associated with a discogram.¹⁰ With the discovery of additional MRI pulse sequences and technological advances with electromagnetic fields to provide greater accuracy, the resolution of present-day T1- and T2-weighted images has dramatically improved, making possible diagnoses of spinal pathology that was invisible at the turn of the century.

The workhorse imaging modalities that continue to persist for the evaluation of spine pathology are plain radiographs, MRI, and CT. Plain radiographs remain the first-line imaging study for the evaluation of pain, numbness, weakness, or any other symptoms localizing to the spine. This form of imaging also serves as the initial diagnostic study in the setting of trauma, malignancy, infection, deformity, and degenerative spine pathology, due largely to the ease in acquisition and relatively low cost. Another strength of plain radiographs is the ability to implement specialized views to evaluate stability and flexibility. In parallel with standard anteroposterior and lateral views of the spine, flexion-extension, sitting, and bending views allow providers the ability to appreciate anatomical changes that occur with movement. Due to the high-resolution multiplanar images of vertebral and soft tissue anatomy, MRI remains a first-line advanced imaging study to evaluate spine pathology, avoiding risks associated with radiation exposure. As such, MRI is routinely ordered in the clinic setting and offers relatively high sensitivity and specificity for infections, tumors, disc degeneration, pathologic fractures, and herniations. However, MR imaging does carry a relatively expensive cost and has varying degrees of utility in obese, claustrophobic, and pacemaker-dependent individuals. CT imaging provides for a greater detailed evaluation of the bony anatomy, largely due to its ability to reconstruct three-dimensional and multiplanar images. However, this study comes with the risk of elevated radiation exposure compared to other imaging modalities.

Goals of This Textbook

Over the years, the evaluation of spine anatomy and pathology with plain radiographs, MRIs, and CTs has rapidly developed with a multitude of studies describing various phenotypes and measurements. From these descriptions, various classification systems have been developed to bridge the radiographic findings and measurements with clinical practice. It is important that trainees and providers understand the basics of the radiographic parameters and clinical associations. However, no comprehensive manual exists that describes important phenotypes and measurements based on plain radiographs, MRI, and CT imaging of the cervical, thoracic, and lumbosacral spine. The goal of this textbook was to provide a single source that outlines common radiographic parameters based on these three common spine imaging modalities. There will also be a focus on the clinical application of these imaging phenotypes through the description of classification systems that are often utilized to guide the evaluation, diagnosis, and treatment of spine pathology.

References

1 Dewing S.B. Modern Radiology in Historical Perspective. Thomas; 1962.

2 Hoeffner E.G., Mukherji S.K., Srinivasan A., Quint D.J. Neuroradiology back to the future: spine imaging. Am J Neuroradiol. 2012;33:999–1006. doi:10.3174/ajnr.a3129.

3 Hesselink J.R. Spine imaging: history, achievements, remaining frontiers. AJR Am J Roentgenol. 1988;150:1223–1229.

4 Isherwood I. Sir Godfrey Hounsfield. Radiology. 2005;234:975–976.

5 Hounsfield G.N. Computerized transverse axial scanning (tomography): part 1. Description of system. BJR Suppl. 1973;46:1016–1022.

6 Lauterbur P.C. Image formation by induced local interactions: examples employing nuclear magnetic resonance. Nature. 1973;242:190–191. doi:10.1038/242190a0.

7 Bradley W.G. History of medical imaging. Proc Am Philos Soc. 2008;152:349–361.

8 Edelman R.R., Shoukimas G.M., Stark D.D., Davis K.R., New P.F., Saini S. High-resolution surface-coil imaging of lumbar disk disease. AJR Am J Roentgenol. 1985;144:1123–1129.

9 Modic M.T., Steinberg P.M., Ross J.S., Masaryk T.J., Carter J.R. Degenerative disk disease: assessment of changes in vertebral body marrow with MR imaging. Radiology. 1988;166:193–199.

10 Carragee E.J., Alamin T.F. Discography: a review. Spine J. 2001;1:364–372.

Section I

Upper Cervical Spine

Chapter 2: Radiographic Evaluation of the Upper Cervical Spine

Mark A. Pastore^a; Anthony Viola, III^a; Vadim Goz^b; Noor Tamimi^b; Alexander Vaccaro^{b a} Department of Orthopaedic Surgery, Philadelphia College of Osteopat...