Diagnostic Studies and Radiographic Imaging Modalities for Spine-Related Pain

5 Diagnostic Studies and Radiographic Imaging Modalities for Spine-Related Pain

Carlos J. Roldan and Billy K. Huh

5.1 Introduction

There are several diagnostic imaging techniques available to assist in identifying the structural abnormalities causing back pain. X-ray, the most common and least expensive form of imaging, is usually obtained first. Then, based on the result of the X-ray, the more sophisticated imaging studies may be utilized to more accurately determine the source and extent of the anatomic pathologies and the development of an appropriate treatment plan. A routine imaging study is not always necessary to assess back pain, but if a patient experiences bowel or bladder incontinence, or progressive loss of neurologic function, an immediate imaging study is warranted. As with performing an invasive procedure, interpretation of radiographic images depends on a solid foundation of anatomy ( Fig. 5.1). In this chapter, we discuss the most commonly used diagnostic and imaging tests for patients with spine-related pain, including X-rays, C-arm fluoroscopy, ultrasound, computed tomography (CT), myelograms, magnetic resonance imaging (MRI), electromyograms (EMGs) and nerve conduction studies, diskograms, and nuclear medicine.

5.1.1 X-Rays (Radiographs)

X-rays provide details of the bone structures in the spine and are used to rule out back pain resulting from instability, fractures, or tumors. X-rays show excellent bony details, but soft tissues such as disks and nerve roots are poorly visualized ( Fig. 5.2). An X-ray, therefore, cannot be used to diagnose lumbar disk herniation or other causes of nerve impingement.

Fig. 5.1 (a) Lateral view of the lumbar spine. (b) Superior view of a lumbar vertebral body. (c) Structures in the lumbar neural foramina. (d) Relationship of the exiting nerve root to the pedicle and neural foramen.

Fig. 5.1 (e) Lateral view of the thoracic spine. (f) Superior view of a thoracic vertebral body. (g) Sacral spinal nerve exiting the sacrum. Note that there is usually some distance from the sacral hiatus to the termination of dura mater. The distance is variable; therefore, when the sacrococcygeal ligament in perforated, fluoroscopy with contrast should be performed to confirm location.

Fig. 5.2 X-rays show excellent bony details, but soft tissues such as disks and nerve roots are poorly visualized as here. (a) Anteroposterior (AP) view and (b) lateral view.

Advantages

• Noninvasive.

• Low cost.

• Readily available.

• Able to detect gross bone abnormalities in the vertebrae and the disks, such as degenerative changes, osteoporosis, or infections.

• Helpful to evaluate spinal alignment and curvature, bone stability, and some congenital defects and tumors.

Disadvantages

• Limited to single view.

• Nonspecific and limited details of soft tissue.

• Accumulative radiation if used repeatedly.

• Difficult interpretation and high rate of false-positive findings.

5.1.2 C-Arm Fluoroscopy

C-arm fluoroscopy is the most commonly used imaging technique for spinal endoscopy and spinal axis procedures.

Advantages

• Portable and convenient for spinal injection procedures.1

• Real-time feedback.

• Multiplanar correlation.

Disadvantages

• Limited to two-dimensional anatomy images.

• Cannot be used to treat complicated cases or in the presence of deformities.

• Repeated use may result in significant radiation exposure to the patient and surgical staff.

5.1.3 Ultrasound

Ultrasound has recently been used to facilitate lumbar spinal and epidural anesthesia. Prior to the spinal procedure, ultrasound spine examinations allow identification of the level of the spine at which the procedure should be performed and the optimal needle entry site. The ultrasound technique is a good alternative to fluoroscopy for performing facet joint and interlaminar lumbar epidural steroid injections if the patient has contraindications to contrast dye or fluoroscopy. For lumbar medial branch blocks, needle placement precision ranges from 62 to 95% in trained hands.2 Ultrasound can also reduce the risk of failed or traumatic lumbar punctures and epidural catheterizations ( Fig. 5.3).³

Advantages

• Inexpensive and portable.

• Lack of radiation or known accumulative effects.

• Real-time needle advancement visualization.

• Good imaging technique for spondyloarthritis and enthesis pathology.

• Enhanced safety and reduction in procedure time.⁴

• Other procedures such as thoracic paravertebral blockade are simplified with a low incidence of complications.⁵

Disadvantages

• Operator dependent; sonoanatomy differs from traditional two-dimensional techniques.

• Narrow image windows.

• Imaging is limited by increased depths and acoustic shadow artifacts.

• Inability to detect intravascular injection and the spread of the injectate.

• Maximal potential still not proven in many interventions and diagnosis.

• More studies are needed to validate the safety and efficacy for lumbosacral procedures.

5.1.4 Computed Tomography

CT scan can provide a detailed picture of bone, soft tissue, muscles, organs, tumors, and other spinal pathologies. A computer is used to reformat the image into cross-sections of the spine. Hence, CT is capable of imaging source of back pain caused by specific conditions such as disk herniation or spinal stenosis.

Spiral CT scan is more accurate and faster with reduced radiation exposure. Intravenous contrast allows better visualization of soft tissue structures and blood vessels ( Fig. 5.4).