Facet (Zygapophyseal) Intraarticular Joint Injections

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Chapter 12 Facet (Zygapophyseal) Intraarticular Joint Injections

Cervical, Lumbar, and Thoracic

Chapter Overview

Chapter Synopsis: It is estimated that nearly half the general population experiences spinal pain. In many cases, this pain arises from the facets, the tiny, paired joints between each vertebra of the spine. Although the facet joints promote stability of the spine, they also prevent spinal injury by limiting the bones’ range of motion. Naturally, these structures are richly innervated and therefore subject to painful conditions. This chapter considers the anatomical details of facets at the cervical, thoracic, and lumbar levels, which impact the procedures to inject the joints. Fluoroscopy is generally required to visualize during the injection procedure, but ultrasonography and computed tomography may also be used. Other technical details and risk of complications are also considered.

Important Points:

Clinical Pearls:

Clinical Pitfalls:

Introduction

Spinal pain is extremely common. The incidences of pain in the neck, thoracic, and low back are estimated at 44%, 15%, and 56%, respectively, in the general population.1 Facet arthropathy is an important source of spinal pain, and facet interventions are the second most common procedure performed in the United States by pain physicians, behind epidural steroid injections. This chapter focuses on the intraarticular injections of facet joints between vertebrae C2 through S1 for diagnostic and therapeutic purposes. The injection of the atlanto-axial joint (AAJ) between vertebrae C1-C2 is discussed elsewhere.

Prevalence of Facet Joint Pain

Estimates of lumbar facetogenic pain vary, from 15% of all back pain complaints2 to 59.6% males and 66.7% females in the community based on a population study.3 The prevalence of lumbar facetogenic pain, determined by placebo-controlled diagnostic blocks using a criterion of 90% pain reduction, ranges from 27% to 40% in patients with axial low back pain.4,5 Sedation may increase false-positive rates of diagnostic blocks by 10%, but psychological comorbidity has not been shown to affect the diagnostic accuracy. Aging is positively related to the prevalence of lumbar facet arthropathy, with an occurrence of 89% in individuals 60 to 69 years old. The most common level is at L4-L5.2

The prevalence of thoracic facet pain ranges between 33% and 48% with a 95% confidence interval based on responses to comparative controlled diagnostic blocks.6 The prevalence of cervical facet pain is 30% to 70% of cases79 and is not significantly affected by prior surgery, psychopathology, or age. The most commonly affected facet is C4-C5 (14.62%) followed by C3-C4, C2-C3, C5-C6, and C6-C7, respectively.10 There is no proven correlation between clinical manifestation of facetogenic pain and facet arthrosis shown by imaging studies or cadaveric observations. Diagnostic block remains the best available tool to identify facetogenic pain despite its high false-positive rates (39% to 53%).

Thus, facet arthropathy accounts for approximately 40% of axial cervical and thoracic pain and approximately 30% of axial lumbar pain. The most commonly affected levels are C4-C5 at the cervical region and L4-L5 at the lumbar region. Whereas lumbar facet pain is more age dependent, predominantly occurring in elderly adults, cervical and thoracic facet pain is not significantly affected by age.

Establishing Diagnosis

Numerous studies have attempted to determine the historical, or physical, and radiographic findings that correlate with pain associated with facet arthropathy. None has been proven specific, sensitive, and reliable.2 Consequently, diagnosis is primarily based on pain reduction and mobility improvement in response to controlled diagnostic facet blocks.4,6,11 The diagnosis of facetogenic pain is suggested by controlled comparative (lidocaine/bupivacaine) medial branch blocks. A criterion of 80% pain reduction and the ability to perform maneuvers that were painful before the diagnostic intervention are commonly used. However, a recent study suggests that using 50% pain reduction as a criterion for positive diagnostic block is just as effective as using 80% pain reduction in predicting the outcomes of medial branch radiofrequency ablation.12

Even though facetogenic pain is primarily determined by diagnostic blocks, clinical findings from history and physical examinations usually help physicians decide if diagnostic facet blocks are warranted. For example, pain from the AAJ is typically provoked by head rotation with the neck slightly flexed forward. This information may lead to an AAJ block rather than a cervical facet block. Therefore, taking the patient history and performing a physical examination is still an indispensable step in establishing a diagnosis of facet pain. Pain referral patterns for cervical and thoracic facet pain have been generated,2,1315 as shown in Fig. 12-1.

image

Fig. 12-1 Maps of referred pain from the cervical (A) and thoracic (B) facets.

(Part A adapted from Bogduk N, Marland A: The cervical zygapophysial joints as a source of neck pain, Spine 13:610-617, 1988; part B adapted from Dreyfuss P, Tibiletti C, Dreyer SJ: Thoracic zygapophyseal joint pain patterns: a study in normal volunteers, Spine 19:807-811, 1994.)

Cervical Facet Pain

Restricted range of motion is not pathognomonic for facet pain and can present in a variety of neck disorders, such as whiplash injury. Point tenderness was recently evaluated in 33 patients by assessing pain pressure thresholds in symptomatic and asymptomatic facets joints.16 Although the pain pressure thresholds are significantly lower in patients with neck pain, this approach is not diagnostic for cervical facet joint pain. Neck point tenderness can be indicative of myofascial pain or associated with tension headache.17 No provocative tests tend to produce pain in the referral patterns. As a general rule, the upper facet joints may cause headache, and the lower joints may have pain referred to the shoulder in a nondermatomal distribution. Cervical radicular pain is usually absent.

Thoracic Facet Pain

Pain from thoracic facet joints may be provoked by facet capsule distention,14 such as extension, lateral bending, and twisting or paraspinal pressure overlying the facet joints. Pain is often nonradicular, and there is no associated weakness.

Anatomy of the Facet Joints

The vertebral column most commonly consists of seven cervical, 12 thoracic, and five lumbar vertebrae. Two adjacent vertebrae make joint connections through the intervertebral disc in the front and a pair of facet joints in the back, with the exception of C1-C2 vertebrae. The facet is a true synovial joint between the inferior and superior articular processes composed of a synovial membrane, hyaline cartilage, and fibrous capsule. These joints function to support the stability of the spine and prevent injury by limiting excessive motion in all directions.

The facet joints have rich innervation, including encapsulated, unencapsulated, and free nerve endings.2 These innervations provide nociception through C and A-δ afferents as well as proprioception through low-threshold, rapidly adapting mechanoreceptors.19 Immunocytochemistry of facet joints demonstrated the presence of substance P, calcitonin-gene-related peptide, and neuropeptide Y, suggesting pain transmission and sympathetic fibers.2022 Facet joint distraction in rats produces spinal astrocyte activation and persistent mechanical allodynia.23 The expression of a binding protein BiP, also known as growth-related protein 78, is upregulated 2.1-fold in the dorsal root ganglion after painful distraction injury to the rat C6-C7 facet, indicating neuronal stress activation.24 Cytokines and neurotrophic factors are upregulated in dorsal root ganglion neurons in models of facet joint inflammation.2528

The architecture and orientation of the facet joint vary with function and position along the vertebral column.2931 The lumbar facet joint can accommodate an average of 1 to 1.5 mL fluid. The joint is C

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