10 Transforaminal and Interlaminar Approaches in Epiduroscopy

10.1 Introduction

An important indication for epiduroscopy has been to further address chronic back pain following failed back surgery. Epiduroscopy in chronic radicular pain demonstrated fibrosis in almost 100% of patients.1 The high prevalence of scar tissue in these patients has created interest in using epiduroscopy for performing adhesiolysis to remove the fibrosis and possibly alleviate pain associated with irritation of affected nerves.² It can also be used to deliver corticosteroids to more specific sites. In recent years, the interlaminar and transforaminal approaches have been developed and refined ( Fig. 10.1). However, they are not widely used, especially in the United States, and there is limited literature about the technique and benefits of one approach versus another. Epidural lysis and diskectomy appear to be more common uses of epiduroscopy at this time. Among surgeons, the significance of adhesions causing pain is not uniformly accepted. Adhesions are part of the healing process and occur in every surgery, but not every surgery or even a significant number of spine surgeries have pain from adhesions. In addition, it should also be noted that there may be a lack of correlation between the extent of radicular symptoms and the amount of displacement of a herniated disk.³

There is a significant body of evidence over the past decade involving epiduroscopy utilizing caudal insertion. Recently, techniques have involved utilizing smaller instruments in an attempt to employ epiduroscopy via transforaminal and interlaminar techniques. Due, in part, to the large needles required, the interlaminar approach is not commonly practiced. Interventional pain specialists not trained in surgery will seldom use these techniques secondary to the innate complexity requiring significantly more training with exponentially more risk for medical errors. This chapter focuses on these newer techniques and provides a very general introduction for people interested in these approaches to pain management. Adhesions can be observed in every epidural space, but do not correlate with these flimsy adhesions. Just irrigating the epidural space can bring temporary relief from pain caused by inflammation. Furthermore, relief can be obtained with caudal epidural blocks without the use of an epiduroscope.

10.2 Transforaminal Approach

The transforaminal approach can be advantageous to gain access to the epidural space and facets without disrupting or denervation the multifidus and sacral spinalis muscles.4 Transforaminal endoscopic approach can also provide the least invasive basic access to the disk and foramen to cover a large spectrum of painful pathologies. Indications for using the transforaminal approach as stated by Gore and Yeung³ include removal of foraminal fibrosis from failed back surgery, foraminal and extraforaminal stenosis, foraminal osteophytosis, and annular tears with diskogenic lumbar pain. Yeung and Gore also note that the absolute ideal indication of the transforaminal approach is for foraminal and extraforaminal disk herniations and diskitis.

Fig. 10.1 The various approaches to the epidural space include the transsacral hiatus, transforaminal, and interlaminar approaches.

10.2.1 Preoperative

Preoperative administration of moderate sedation to the patient is dependent on surgeon preference, but is largely a requirement. Experienced endoscopic surgeons use less and less sedation in order to obtain greater feedback from the patient during surgery—a safety factor and a condition that produces the best results while monitoring the procedure during surgery. In reviewing the literature, either a 14- or 18-gauge needle is employed, allowing for appropriate delivery of local anesthetic imperative for a smooth procedure and comfort of the patient. In this regard, the patient must continually be conscious in order to provide an indicator to whether there the structure visualized is a pain generator or if there is any nerve compromise,2 as this could result in a catastrophic outcome. Generally, midazolam, 1 to 2 mg intravenously, is administered half an hour before the surgery. Additionally, fentanyl, 25 to 50 μg intravenously, is typically administered 15 minutes prior to the procedure and continued intermittently intraoperatively.⁵ In very rare patients, propofol can be administered in a small dose, 25 to 50 μg/kg/min intravenously, to provide a uniform plane of anesthesia to accomplish intraoperative moderate sedation.

10.2.2 Intraoperative

• The patient is faced prone on the operating table to ensure the patient is comfortable for the duration of the procedure ( Fig. 10.2). The trajectory to the neural foramen is determined on preoperative computed tomography scan or magnetic resonance imaging and a skin entry site marked ( Fig. 10.3).

Step 2: Local Anesthesia

• A wheel is formed using 2 mL of lidocaine 1%. Under fluoroscopic guidance and using the posterolateral approach, an 18-gauge spinal needle approximately 7 inches in length is used to create a track along the anticipated course, while evenly administering 10 mL lidocaine 1% ( Fig. 10.4).⁵

Step 3: Transforaminal Epidural Approach

• Related to the pain of this procedure, a concomitant epidural can be preliminarily performed at this step to further assist with pain reduction. First, a 20-gauge spinal needle is inserted into the epidural space.⁵ Fluoroscopy confirms the trajectory to the neural foramen ( Fig. 10.5). The needle is directed toward the foramen ( Fig. 10.6) and a fluoroscopic picture taken from an anteroposterior (AP) view should show the tip of the needle located at the corresponding midpedicular line within the epidural space ( Fig. 10.7a) and inferior aspect of the foramen on lateral view ( Fig. 10.7b).⁴ The stylet is removed and the guidewire is passed through the spinal needle ( Fig. 10.8). The position of the guidewire is confirmed by fluoroscopy ( Fig. 10.9). The spinal needle is removed over the guidewire ( Fig. 10.10) and the 14-gauge Tuohy needle is passed over the guidewire ( Fig. 10.11). Fluoroscopy is used to confirm the position of the Tuohy needle ( Fig. 10.12). The Tuohy needle is removed and the skin entry site is enlarged with a 15 blade ( Fig. 10.13). The dilators is then passed over the guidewire ( Fig. 10.14) and confirmed on fluoroscopy ( Fig. 10.15). The guidewire is then removed and radiopaque dye is injected, confirming proper placement ( Fig. 10.16 and Fig. 10.17).⁴

Fig. 10.2 Operating room setup.

Fig. 10.3 Estimation of the trajectory angle from the skin entry to the neural foramen.

• The guidewire is reinserted through the dilator ( Fig. 10.18). With the guidewire in position, the dilator is removed ( Fig. 10.19) to allow passage of the dilator with sheath ( Fig. 10.20). The position of the dilator and sheath is confirmed on fluoroscopy ( Fig. 10.21). The dilator and guidewire are removed, leaving the sheath in position ( Fig. 10.22).

Step 5: Endoscope Insertion

• The endoscope is brought in and inserted through the sheath ( Fig. 10.23). Should the patient report symptoms of nerve irritation, the sheath can be maneuvered to avoid the exiting nerve root.⁴ The endoscope is now in place for viewing ( Fig. 10.24). After the procedure is completed, the cannula and endoscope are slowly withdrawn, taking caution not to damage any of the nerve roots.

Fig. 10.4 Determination of skin entry site. Local anesthesia is injected along the trajectory of the spinal needle.

Fig. 10.5 (a) Anteroposterior fluoroscopic view of the spinal needle approaching the foramen. (b) Lateral fluoroscopic view of the spinal needle approaching the foramen.

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