Epiduroscopic Surgical Tools

Günter Schütze

7.1 Introduction

The requirements for clinical use of spinal endoscopy medical products for diagnostics and therapy of neuraxial pain syndromes are regulated by the medical products statutes of the respective nations, for example, in the United States, by the Food and Drug Administration (FDA).1 A large number of these endoscopic products, including the necessary tools, are licensed under the FDA 510(k) process or under country-specific or European Union (EU) medical product licenses.² In the EU the CE mark on a medical product is the manufacturer’s declaration that the product meets all the legal requirements for that product for sale in the European Economic Area, and is recognized worldwide.

National and international medical guidelines exist for the performance of the most common neuraxial diagnostic and pain-therapeutic interventional procedures,, in particular, for the invasive operations for neuromodulation.³ In this context, it is important to give the experienced physicians latitude for decisions and corridors for action that depart from the technical recommendations in well-founded individual cases.

This chapter contains systematically developed proposals for the solution of special neuraxial diagnostic and therapeutic problem situations from the realm of pain medicine (see also Chapter 6).

As a minimum standard, the following materials should be kept ready in the operating room (OR) for epiduroscopy (EDS) ( Fig. 7.1):

• Local anesthetic.

• Contrast medium.

• Saline ampoules.

• Syringes.

• Needles.

• Scalpel.

• Surgical sutures.

• An introducer set (introducer needle, safety J-guide, dilator, and sheath).

• Catheter (epidural catheter, Caud-A-Kath, balloon catheter, and ultrasound catheter).

• Electrodes (spinal cord stimulation electrodes [SCS] and multifunction electrodes).

• Laser fiber.

• Flexible microsurgical instruments.

• Facility for warming epidural infusion fluids.

• Transport vessels for tissue samples and swabs.

• Bandage materials.

Percutaneous spinal endoscopy is to be realized only through caudal access to the epidural space of the patient with special flexible endoscopic apparatus and supporting instruments.⁴

7.2 Instruments for Access to the Epidural Space

To gain percutaneous access to the epidural space via the sacrococcygeal ligament, a special set of instruments or a commercial introducer set are required. We recommend a set consisting of an introducer needle (also called a guide needle), a safety J-guide (Seldinger wire), a dilator, and a sheath. Percutaneous access is obtained with this set of instruments and utilizing the Seldinger technique, a method developed in 1953 by the Swedish radiologist Sven-Ivar Seldinger for venipuncture in order to introduce an angiography catheter. The Seldinger wire, the safety J-guide in this case, plays a special role in this process.

Fig. 7.1 Basic supplementary instruments for spinal endoscopy.

7.2.1 Scalpel

Prepare the area for the sacral incision, or puncture, following current clinical hygiene regulations. After local anesthesia for the percutaneous placement of the sacral sheath, with a common surgical scalpel, incise the skin in the designated region of the sacral hiatus from about 4 cm away from the anal opening, up to contact with bone ( Fig. 7.2).

7.2.2 Introducer Needle (Puncture Needle)

With a introducer needle provided with a precision triangular bevel for an easy and uniform percutaneous puncture in the region of the sacral hiatus, puncture the tectorial membrane at an angle of about 45°. After the introducer needle has perforated the sacrococcygeal ligament, and after a facultatively negative aspiration test, an introducer wire (Seldinger wire) can be placed through the funnel-shaped needle approach of the safety guide.

Fig. 7.2 Commercial scalpels from various manufacturers with adjustable and fixed blades. (Courtesy of Wikimedia.)

7.2.3 Tuohy Needle

In patients where anatomical access to the sacral canal is difficult to attain, the more robust 14-gauge Tuohy needle is recommended instead of the needle from the introducer set. The tip of the Tuohy needle is relatively blunt and formed at an angle of about 20°. Using this needle, an atraumatic positioning or guidance of the wire, catheter, or electrode in the sacral canal is made possible. A stylet attached to the Tuohy needle prevents tissue coring (biopsy effect) and increases the stability of the puncture.5 The thin-wall needle technique ensures the penetration of guidewires and catheters of large diameter. Centimeter markings along the entire length of the needle make it possible to determine of the depth of penetration of the Tuohy needle. Tuohy 14- and 16-gauge introducer needles for sacral access are available in needle lengths of 9.2 cm, 11.4 cm, and 15.2 cm for SCS electrode placement. The Tuohy 15-gauge needle is available in needle lengths of 9.3 cm and 11.4 cm ( Fig. 7.3).

7.2.4 Guidewire

Through the introducer needle or Tuohy needle placed in the sacral canal, a guidewire (J-guide) can be introduced for a short length into the sacral canal. The guidewire (Seldinger wire) consists of a very tightly wound helical steel wire. The wire tip is bent back semicircularly in a J-shape to avoid perforation of surrounding tissue while within the sacral canal. For improved navigating ability, longer guidewires are ensheathed in a circularly bent plastic sleeve.

To identify and follow the J-guide (Seldinger wire), 50-cm long as a rule, in the sacral canal, fluoroscopic imaging (C-arm technique), primarily in anteroposterior (AP) but also in lateral projection, is very helpful.

7.2.5 Introducer Sheath

The sheath must be matched in size to the endoscope as well as adapted to the anatomical conditions of the patient ( Fig. 7.4).

A dilator with plastic sheath, for example, in sizes from 9.0 to 12.0 Fr and with or without a side port (PVB, Smiths Medical, Kirchseeon, Germany), can be placed over the recumbent guidewire (J-guide) percutaneously for a short distance in the sacral canal of the patient. The selection of the perfect dilator and sheath is a prerequisite for a smooth introduction of the sheath through the skin at the sacral hiatus and the tectorial membrane of the sacral canal ( Table 7.1).

After a check of the exact location of introducer, remove the dilator including the guidewire. The plastic sheath of the introduction system, which remains, ensures a relatively atraumatic, safe, and permanent access for the introduction of the epiduroscope into the epidural cavity and provides important protection against shear.

Fig. 7.3 Selection of Tuohy needles. (Courtesy of Pajunk GmbH Medizintechnologie, Geisingen, Germany.)

Fig. 7.4 Introducer sheath with Seldinger guidewire (J-guide) in the sacral canal.

The basic instrument set for percutaneous access to the sacral canal according to Seldinger technique includes ( Fig. 7.5):

• Puncture needle, diameter 1.3 × 63.5 mm (18 gauge).

• Guidewire, 70 cm, 0.035-in. diameter (0.89 mm).

• Flexible J-guidewire with introduction aid.

• Introducer kit 6–12 Fr with dilator and introduction lock.

7.2.6 Introducer Kits

The “Break-Away” Introducath Desilet (Vygon GmbH & Co. KG, Aachen, Germany) is available for percutaneous access to the sacral canal for placement of a flexible endoscope. This introducer kit contains an introducer needle, safety J-guide, dilator (20 cm), and a fully radiopaque splittable sheath (14 cm) as accessories. Through the correspondingly large, percutaneously placed shell, the sterile epiduroscope can be introduced into the epidural space carefully and easily under visual control via the monitor. After completion of the spinal endoscopy, the sheath can be split and removed without problems, by pulling apart the grip pieces.

The first introducer kit for percutaneous sacral access for epiduroscopy according to the Seldinger method (9045S, Karl Storz, Tuttlingen, Germany), the introducer kit according to Schütze, includes a single-use 9-Fr dilator and sheath and a puncture needle and guidewire. A separate vent as a portal for the epiduroscope with the possibility of irrigation is available.

Clinical Notes

• Gaining access to the epidural space through the sacral hiatus sometimes succeeds only with the help of special navigation maneuvers and, as necessary, also by the use of suitable size dilators and sheaths (9 Fr, 10 Fr, 11 Fr, or 12 Fr). For use and protection of instruments introduced epidurally parallel to the endoscope, it is desirable to use a sheath 1-Fr larger than the epiduroscope.

• With the percutaneous sacral access technique, the distance from the lower end of the dural sac to the sacral hiatus must absolutely be observed, as the distance is very individual. It can be as much as 16 mm ( Fig. 7.6).

Fig. 7.5 Introducer kit. (Courtesy of PFM Medical AG, Cologne, Germany.)

Fig. 7.6 (a) Guidewire (double flex, 0.038-in. diameter, 45-cm length) in the sacral canal. (b) Tuohy needle and guidewire in the sacral canal.

7.3 Microsurgical Instruments

Along with the digital endocamera system and a fluoroscopic unit (C-arm), a corresponding sterile microsurgical instrument set is to be provided for the EDS and endoscopic operations. For a full list of EDS equipment to be kept in the OR, please refer to the list in 7.1 Introduction.

7.3.1 Forceps

There are a wide range of forceps available for taking targeted tissue samples under epiduroscopic view. In selecting the forceps to be used, you should be guided by the type and amount of tissue to be extracted and the neuraxial region where the operation will take place. Along with endoscopic tissue removal, mechanical epidural adhesiolysis or reduction or resection of epidural fibroses or scar tissue can be accomplished with the help of microsurgical forceps.6

For the extraction of neuraxial tissue for histologic investigation, the chosen microsurgical forceps are introduced through the working channel of the epiduroscope into the epidural space.

Flexible microsurgical forceps, or microforceps, are available in various lengths and diameters according to the epiduroscope used and to the tissue material to be removed. The following instruments, among others, are available:

• Oval flexible grasping forceps of various effective lengths up to 160 cm with an outside diameter (OD) at least 0.8 mm.

• Flexible grasping forceps, alligator jaws, of various lengths up to 160 cm with an OD of 1.0 mm.

For epiduroscopes with a shorter effective length, the selection of flexible microsurgical forceps include ( Fig. 7.7):

Fig. 7.7 Most common working ends for autoclavable flexible microsurgical instruments. (Courtesy of Günter Stoffel Medizintechnik GmbH, Wurmlingen, Germany.)

• Flexible grasping forceps with movable jaws (0.8-mm OD, length 60 cm); the same forceps with 100-cm length.

• Flexible grasping forceps with movable jaws (1.0-mm OD, length 60 cm); the same forceps with 100-cm length.

Basically, flexible forceps are opened and closed by a cable.

Because of the risk of damage to the working channel of the epiduroscope, for example, by a forceps thorn, forceps without thorns should absolutely be used ( Fig. 7.8; Fig. 7.9; Fig. 7.10).

Without sufficient endoscopic imaging, risky microsurgical procedures, above all in the thoracic and cervical regions of the spinal canal, should be forgone on the basis of patient safety. Special caution should be observed and attention given to biopsy and lysis procedures for inflammatory processes and in the region of the nerve roots! Additional safety can be ensured by epidural ultrasound navigation or endomicroscopy (see Chapter 8).

Clinical Notes

• Because of the vulnerability of neuraxial structures, it is essential to endoscopically observe the tissue removal with microsurgical forceps to help insure that no blood vessels, spinal dura mater, or nerve structures are injured.⁶

• If vessels are damaged by a biopsy, these can, as necessary, be coagulated with a laser fiber (diode laser) through the working channel of the endoscope.

• Epidural lysis or biopsy procedures with microsurgical instruments, above all in the cervical region of the spinal canal, must be carried out particularly carefully and scrupulously.⁷

7.3.2 Laser Fiber

Through the working channel of the epiduroscope, the light guide, the bare fiber, can be introduced under endoscopic view into the epidural space without problems.

Fig. 7.8 Flexible autoclavable microsurgical grasping forceps of lengths 60 cm and 160 cm. (Courtesy of Karl Storz, Tuttlingen, Germany.)

The forward-emitting light guide is a standard accessory for minimally invasive endoscopic intervention. The bare fibers are available in diameters of 200 μm, 300 μm, 400 μm, and 600 μm. The 3-m long bare fiber provides the user with the highest possible flexibility and distinctive radii of curvature and expands the load-bearing capacity for light through an improved light guide core and the surrounding protective layer.

Fig. 7.9 Microsurgical instruments. (a) Open forceps in the epidural space. (b) Open forceps.

Fig. 7.10 (a) Spinal catheter endoscopically removed with microsurgical grasping forceps from the dorsal thoracic epidural space (picture-in-picture technique). (b) Endoscopically removed foreign body (a sheared-off epidural catheter).