2 Endoscopic Surgical Instruments

General Characteristics of a Spinal Endoscope

The heart of the endoscopy system is the endoscope itself.1
Endoscopes are used in the same fashion as an operating microscope employed for open spinal surgery.
They magnify the anatomy while providing a source of illumination and precise visualization.
Unlike microscopes, endoscopes provide illumination at depth and can be positioned directly over the working area to provide unobstructed vision.
Spinal endoscopes differ from other endoscopes in the following ways:2
- They are working-channel scopes. That is, the procedures are performed through the endoscope.
- Angled scopes are used in the lumbar and thoracic spine because they provide a viewing trajectory that is oblique to the anatomy.
  - They can be used to look around the corners or edges that cannot be viewed with a 0-degree scope.
  - They can provide a substantially greater field of view but are more difficult to use because they have more variables to control in terms of image orientation, perspective, and navigation.
- A 0-degree endoscope is preferred in cervical diskectomy because it provides a direct end-on view of the pathology.
- The elliptical shape of the endoscope when fitted inside the round cannula spares some space between the endoscope and the cannula, which serves as an outflow channel for the irrigation fluid.
- Recently developed large-sized working-channel endoscopes allow passage of large-sized forceps, endoscopic reamers, chisels, and drills.

General Characteristics of Endoscopic Surgical Instruments

Endoscopic tools differ from those used in open surgery in the following ways3:
- The tools are much longer.
- Depth markings are calibrated on their shafts.
- End tips are slightly angled or curved to facilitate visualization of the tip during dissection.
- Longer tools often dampen or reduce the feel of the tissue planes.
  - The surgeon has to rely heavily on the visual characteristics of the tissue for identification.
  - Video-assisted endoscopic spinal surgery requires a three-dimensional visuospatial orientation.
Endoscopic surgical instruments can be categorized into five groups:
- Mechanical instruments: rigid forceps, dissecting instruments, etc.
- Special instruments: endoscopic chisel, bone trephines, or reamers
- Electrosurgical instruments: radiofrequency bipolar unit
- Motorized instruments: endoscopic drill
- Laser: side-firing holmium:yttrium-aluminum-garnet (Ho:YAG) laser
The endoscope and the ancillary instruments available for performing diskectomy in the lumbar and cervical spine are different from each other. This chapter describes both of these systems in detail.

Endoscopy Systems for Percutaneous Endoscopic Lumbar Diskectomy

There are numerous endoscopes available, each having its own advantages and disadvantages because of minor changes in design ( Fig. 2.1, Table 2.1 ).
In general, an endoscope consists of an eyepiece, a barrel with a metal casing enclosing the lens for visualization, a fiberoptic system for the transmission of light, an irrigation channel for inflow, and a working channel.
An attachment connects the endoscope to the light source by a fiberoptic cable.

**Fig. 2.1** Telescope: Panoview Plus Discoscope can be rotated through 360 degrees and can be removed for cleaning. Different parts of a lumbar spinal endoscope are shown. (Richard Wolf Medical Instruments Corporation, Vernon Hills, Illinois)

Instruments Used for Lumbar Endoscopy

The wide range of instruments available increases the surgical armamentarium, making the system more complex and expensive and also creating potential confusion for the beginner.
Following here we describe the essential instruments for performing an effective endoscopic diskectomy. The instruments are grouped according to the surgical steps in which they are used.

Instruments Used for Insertion of the Endoscope

Spinal needle set ( Fig. 2.2 )
- 20 gauge: 250 mm
- Also called an approach needle

**Fig. 2.2** Spinal cannula set. Disposable (PU = 10 pieces individually sterile packed) consisting of spinal cannula, inner needle. (Richard Wolf Medical Instruments Corporation, Germany)

Inserted by a posterolateral approach under fluoroscopic guidance
Used to administer a transforaminal epidural block before it is advanced further into the disk space to perform diskography

Guide wire
- Measures 1.8 mm in diameter and can be easily passed through the approach needle
- Replaces the approach needle
Annular cutters/annulotomes.
- A 3-mm diameter bone trephine with a length of 420 mm is used to make a hole in the tough and fibrous annulus to allow easy passage of the obturator.
Obturator ( Fig. 2.3 )
- The obturator is a cannulated cylindrical instrument, which is passed over the guide wire.
- It has an outer diameter of 5.9 or 6.9 mm with a working length of 235 mm.
- It is blunt and tapered at the end that enters the body.

**Table 2.1 Comparison of Currently Available Endoscopes**
	YESS*	Vertebris*
Scope dimensions	5.8 × 5.0 mm	5.9 × 5.0 mm, 6.9 × 5.6 mm
Optics	The barrel consists of a working-channel, rod-lens system and two irrigation channels	Modification of the old YESS system consisting of a larger working channel, smaller fiberoptics, and only one irrigation channel

Working length	205 mm	205 mm endoscope for transforaminal approach 165 mm endoscope for interlaminar approach
Working channel diameter	2.7 mm 2.7 mm	3.1 mm 4.1 mm
Optical (lens) angle	20 degrees	25 degrees
Working cannula sleeve diameter	6.9	8 mm
Abbreviation: YESS, Yeung Endoscopic Spine System. ^*Richard Wolf Medical Instruments Corporation, Vernon Hills, Illinois.

**Fig. 2.3** Dilator. (Richard Wolf Medical Instruments Corporation, Vernon Hills, Illinois)

The tapered end facilitates displacement of the neural structures away from the operating field during its insertion, thereby preventing injury to the nerve root.

Working sleeve/cannula ( Fig. 2.4 )
- The working cannula is a hollow cylindrical sheath with an outer diameter ranging from 7 to 8 mm and a length varying from 145 mm (for interlaminar endos-copy) to 165 mm (for transforaminal endoscopy).
- The end that is inserted inside the body is either beveled or flat (round).
- The beveled cannula is used for an intracanalicular disk herniation, and the round cannula proves more useful in foraminal and extraforaminal disk herniations.
- The cannula is inserted over the obturator into the disk space.
Hammer driver and mallet ( Fig. 2.5 )
- The working cannula, which is inserted over the obturator, is usually hammered inside the disk space with the help of a hammer driver and a mallet.
- It is done under fluoroscopic guidance in the antero-posterior view, and the position is then confirmed on the lateral view.

Instruments Used for Diskectomy

Rigid forceps
- Fluoroscopic forceps ( Fig. 2.6 )
  - Not very commonly used
  - Forceps are 5 mm to 5.2 mm in diameter and therefore cannot be passed through the endoscope.
  - They are passed directly through the working cannula.
  - They are used strictly under fluoroscopy guidance for the initial removal of the disk material.
  - Inadvertent use can cause injury to the nerve root or the dural tube.
- Large-diameter endoscopic forceps ( Fig. 2.7 )
  - Most commonly used forceps having a diameter of 3.5 mm
  - Can be easily passed through the working channel of the endoscope and therefore are always used under direct endoscopic visualization
  - Two types: upbiting or downbiting forceps
  - The jaw margins can be serrated or nonserrated (plain)
- Small-diameter endoscopic forceps ( Fig. 2.8 )
  - Diameter is 2.5 mm or less.
  - Used in situations when there is less space available for the insertion of large forceps (e.g., narrow space between the nerve root and the dural sac or some bony obstacle)
Articulating forceps ( Fig. 2.9 )
- Optional instrument not used by all surgeons
- Useful in cases when the herniated fragments are placed away from the tip of the endoscope and, though visible, are not directly accessible
Dissecting instruments
- Probe ( Fig. 2.10 )
  - A cylindrical instrument with an outer diameter of 2 mm and a length of 400 mm
  - The working end can be straight or angled at 90 degrees to form a 3 mm hook with a blunt tip.
  - It is used for probing the tissues or dissecting the disk fragments from the neural tissue.
- Dissector ( Fig. 2.11 )
  - The working end is flattened in the form of a spade.