Shrif Costandi MD and Nicholas Prayson MD Cleveland Clinic, Willoughby Hills, OH, USA Discogenic pain is common and has been estimated to be present in up to 26–42% of individuals with chronic back pain complaints [1]. The proposed theory for the development of discogenic pain revolves around a combination of increased sensory nerve ending growth at the site of annular tears or fissures and the associated inflammation at that site [2–5]. A separate mechanism of pain is caused by herniation of the nucleus pulposus, which can resultingly extend into or through the annulus leading to nerve compression and radicular pain. The procedures described in this chapter are used to diagnose and subsequently manage these types of discogenic pain. Recognition of the possible complications associated with these procedures allows one to offer effective risk assessment and hold more detailed conversations with patients as they decide between various therapeutic avenues. The human spinal column is made up of 7 cervical, 12 thoracic, and 5 lumbar vertebrae. Below these are fused sacral and coccygeal vertebrae. The intervertebral disc provides cushion, as well as flexibility, between the vertebral bodies of the vertebrae. The vertebral bodies and discs are bordered anteriorly by the anterior longitudinal ligament and posteriorly by the posterior longitudinal ligament. These ligaments help provide support and reduce the anterior or posterior sliding of the discs or vertebral bodies. The spinal cord travels posteriorly to the posterior longitudinal ligament within the spinal canal. At each vertebral level, the canal is enclosed anteriorly by the vertebral bodies and the intervertebral discs, laterally by the pedicles and posteriorly by the lamina as they meet midline to become the spinous process. Just below the pedicles of each vertebral level extend the spinal nerves laterally through the intervertebral foramen, which are bordered anteriorly by the vertebral bodies and intervertebral discs and posteriorly principally by the facet joint. The intervertebral discs themselves are formed by a thicker more fibrous outer layer called the anulus fibrosis, which surrounds a more gel-like internal material called the nucleus pulposus. Only the outer layer of the anulus fibrosis is supplied by small nerve endings that branch off the proximal spinal nerves. Segmental arterial vessels traverse the vertebral bodies and branch into interosseus arteries that extend to the cartilaginous vertebral end plates adjacent to the intervertebral discs. These vessels allow for the diffusion of nutrients to the vertebral discs. Discography is a diagnostic-assistive procedure used to assess the functional compliance of the intervertebral disc along with the presence of any structural defects such as tears, fissures or nucleus pulposus herniation. Specifically, radiopaque contrast is injected into the nucleus pulposus of the intervertebral disc in question and a control disc for comparison (Figures 62.1 and 62.2). Fluoroscopy is used to confirm the dye spread and identify any tears or fissures. The manometric variables of the discography are valuable in the assessment of the compliance of the discs. This procedure is a provocative diagnostic test, in which a positive test is signified by a worsening or reproduction of back pain upon the increase of the intradiscal pressure upon injection. Figure 62.1 An anterior posterior (AP) fluoroscopic view of L4–L5, L5–S1 discography. The image demonstrates L5–S1 intervertebral disc degeneration. Figure 62.2 Lateral fluoroscopic view of L4–L5, L5–S1 discography. The image demonstrates L5–S1 intervertebral disc degeneration. The incidence rate of complications associated with discography is variable and based upon the size of the study and the criteria that qualifies a complication. One study by Zeidman et al. of 4400 discography cases demonstrated a complication rate of 0.16% [6]. A separate series published by Guyer et al., identified a 1.49% complication rate out of 269 disc injections [7]. Some smaller studies have shown increased complications rates of up to 13% [8]. The list of complications includes: There are various types of infections that should be considered in association with intradiscal procedures, including subdural or epidural abscesses, paravertebral abscesses and most classically discitis. The ubiquitous infection associated with intradiscal injection is discitis and in a review study performed by Pobiel et al., of 12 634 patients undergoing discography, the incidence of discitis was found to be 0.016%, which translated to a risk of 0.0054% per disc level [9]. Case reports have indicated possible neurologic deficit or paralysis associated with discography due to displacement of part of the intervertebral disc into the spinal canal [10]. Neurologic damage involving the spinal cord, dorsal or ventral rami, or nerve roots can develop given the relative proximity involved in performing these injections, ranging from transient paresthesia to paraplegia requiring urgent surgical intervention [11–13]. Disc herniation, associated with an intradiscal injection, may be the precipitating factor in the development of acute neurologic symptoms [11, 13]. Headache has also been shown to be associated with intradiscal procedures, although this appears to be only rarely documented [7]. Inadvertant intravascular injection can result in bleeding or more commonly hematoma formation. There are no significant large vessels near the common path for intradiscal procedures, but small feeding arteries or venous plexi are present and trauma can result in bleeding. Importantly, such hematomas can develop at not only the immediate operative site, but also at various less accessible locations that might require surgical intervention including; the psoas muscle, retroperitoneal or epidural space [14, 15]. Intravascular injection of dye during attempted intradiscal discography has been documented, but without symptomatic issue [16]. An exceptionally rare complication noted in a case report by Shreck et al., where fatal nucleus pulposus pulmonary embolism occurred in the context of lumbar discography [17]. Fluoroscopic guidance is necessary to safely perform discography. This allows visualization of the needle trajectory as the procedure is completed in the appropriate trajectory. Aspiration, prior to injection of any contrast material, is prudent in order to minimize risk for inadvertent vascular injection. Since infection appears to be the principle complication associated with discography, the question of periprocedural antibiotics is a reasonable one. In a systematic review of the literature, Willems et al., noted that, due to the relative paucity of post-discography discitis cases in the literature, routine prophylactic antibiotics could not reasonably be recommended at the time [18]. A meta-analysis performed by Sharma et al., also examined the efficacy of periprocedural antibiotic in association with discography and concluded that, despite animal models supporting prophylactic antibiotic use, in humans such a relationship was not conclusively shown [19]. The leading cause of discitis is Staphylococcus aureus, hence, the recommendation is to employ the “through the needle” technique, where the first needle is passed through the skin until the annulus fibrosus is reached, then a thinner needle is passed through the first needle down to the nucleus pulposus. Sharma et al. demonstrated that the risk for discitis is reduced from 2.7% down to 0.7% when this technique is adopted [19]. Bleeding, in the form of clinically significant hematoma, is an extremely rare side effect. The risk for bleeding and subsequent hematoma can be minimized by holding anticoagulation medications periprocedurally but, ultimately, such decisions to hold these medications should be weighed against the potential risk for thromboembolic event [20]. Routine coagulation labs or platelet counts are not warranted in the absence of a clinically relevant diagnosis or concerns. Intradiscal injections of various types have been developed to treat discogenic pain. These injections are performed using fluoroscopic guidance to ensure proper localization of the needle prior to injection (Figures 62.3 and 62.4). The technique is performed in a similar manner to discography, with the difference being injection of various therapeutics into the nucleus pulposus. A variety of therapeutics have been used for intradiscal injections, including steroids, saline, methylene blue, stem cells, platelet-rich plasma, fibrin glue, and ozone. The various types of injections have different proposed mechanisms for pain relief. Steroid medications have ubiquitous anti-inflammatory properties that have made such medications mainstream therapeutics for various pain medicine injections. Pressurized saline can be used to release the posterior longitudinal ligament in disc herniation cases thereby releasing the mechanical compression caused by the herniation upon the nearby nerve structures [21]. The proposed mechanism for intradiscal pain relief via methylene blue injection is due to its inhibition of nitric oxide synthase, and subsequent anti-inflammatory sequelae [2]. Multipotent stem-cell injections have a postulated mechanism of reducing catabolism within the disc environment, while also promoting regeneration of discal tissue [22]. Platelet-rich plasma has several possible theorized mechanisms substantiating its consideration for intradiscal injection, including anti-inflammatory properties, as well as its high concentration of various growth factors [23]. Fibrin glue has been employed as a method to try and seal fissure within intervertebral discs. Intradiscal injection of ozone has emerged as a possible therapeutic for disc herniations with some promising long-term results [24]. There are two mechanisms that have been postulated for why ozone can be beneficial. First, the injection of ozone can cause the disc volume to decrease, principally through dehydration [25]. Second, it has been suggested that additional pain relief may also be gained through anti-inflammatory pathways mediated by the injection [25]. Figure 62.4 Lateral fluoroscopic view of final needle placement during an intradiscal injection. Figure 62.3 AP fluoroscopic view of the final needle placement during an intradiscal injection. Since intradiscal injections follow a similar procedural technique as discography, many of the risks are the same as those noted above.
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Complications of Intradiscal Therapeutic Procedures
Introduction
Anatomy
Diagnostic Dsicography
Indications
Contraindications
Technique
Complications
Infection
Nerve Injury
Headache
Vascular Injury/Hematoma
Intravascular Injection
Nucleus Pulposus Embolism
Prevention of Complications
Intradiscal Injections
Indications
Contraindications
Techniques
Complications
Infection
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