Endoscopic Removal of Intradural Extramedullary Space-Occupying Lesions

25 Endoscopic Removal of Intradural Extramedullary Space-Occupying Lesions

Shrinivas M. Rohidas

25.1 Introduction

The last two decades have seen the emergence of minimalism in spine surgery aimed at preventing approach-related trauma to tissue. MISS—minimally invasive spine surgery—is a term that is now used often. In fact, it is a misleading term, because MISS is potentially maximally invasive at the target area. There is no compromise in achieving the precise goal—that is, adequate decompression of compressed neural structures—in MISS, but approach-related trauma to surrounding tissue is minimized.

As MacNab wrote, “It really does not matter what technique you use to decompress the nerve root, if you fail to fully decompress the nerve root or introduce complications to the equation, you have failed to serve the patient.” It is advisable to remember this principle in spine surgery. In MISS, every patient’s symptoms, clinical signs, and radiology have to be evaluated separately and carefully. If the decompression of the compressed nerve root/cord is inadequate, then the compressive symptoms and signs will persist. If the decompression is aggressive or more than necessary, then there are chances that existing stability will be compromised. Hence there has to be an equilibrium between adequate decompression and not compromising existing stability. This equilibrium will be different for every patient, every level to be operated, the extent of stability/instability, and the pathology to be treated. It is dependent on each spine surgeon, along with the technique used by the surgeon. This is one of the many factors that are responsible for the steep learning curve in MISS and endoscopic spine surgery.

Fig. 25.1 Endospine outer tube and inner tube (working insert).

Fig. 25.2 Endospine inner tube with all channels. Working channel of 9-mm and 4-mm channels for suction and endoscope.

25.2 Destandau’s Technique

Jean Destandau, a neurosurgeon from Bordeaux, France, developed a technique for endoscopic spine surgery in 1993.1,2 His technique is based on the triangulation between an endoscope and suction with working instruments.

For Destandau’s technique, the authors use Endospine, a set of outer tube/insert and inner tube/working insert with an endoscope. The endoscope used with Endospine is an 18-cm, rigid, straight, 0° endoscope (that is, a universal endoscope used for cystoscopy, arthroscopy, sinoscopy, etc.). Endospine was initially used for lumbar disk herniation. The target area in the lumbar region is elliptical, between two laminae, medially the spinous process and laterally the medial facet, so the outer tube is elliptical rather than round. The inner tube/working insert fits into the outer tube with a ratchet-type lock. There is an inherent telescoping movement between the tubes (Fig. 25.1).

The working insert has four built-in channels. On the left side of the working insert, there are two 4-mm-diameter channels that are parallel to each other. The medial 4-mm channel hosts the endoscope and the endoscope remains fixed with the lock. The second 4-mm channel is for the suction tube. The largest channel, which has a 9-mm diameter, is for the working instrument (Fig. 25.2).

The channels for the endoscope and suction are at an angle of 12° to the wide channel of the instrument. Because of this angle, the 0° endoscope can be used as an angled scope. This helps to minimizing fogging of the endoscope tip. When the endoscope and the instrument are working parallel to each other, there is intermingling of the instruments, and the surgeon has to use an angled endoscope when endoscope and instrument work parallel to each other. The fourth channel is for the nerve root retractor, which retracts the nerve root medially to expose the disk space. The outer tube and inner tube are fixed in such a way that there is an artificial space created between the two tubes. This is the working space for the instruments. Once the excision of bone is achieved, then the inner tube can be pushed inside/down. If there is no space maintained between the outer tube and inner tube, then the endoscope will touch the tissue in front and will hamper the surgeon’s vision. Also, there will be splashing of fluid over the endoscope lens if adequate space is not maintained between the tubes.

The suction is used with the left hand and the working instrument is in the right hand. With suction in the left hand, the surgeon can move the whole system in medial, lateral, cranial, and caudal directions. The same movements are possible with the instrument in the right hand. The suction in the left hand and instrument in the right hand work to maintain the stability of the system. When the surgeon is using suction to clean the operative area, the instrument in the right hand keeps the system stable, and vice versa—when the surgeon is using the instrument, the suction in the left hand keeps the system stable. Synchronization of movements of both hands is necessary while looking at the image on the screen. The surgeon should learn the synchronization of both hands’ movements, along with using both hands while looking at the screen image. These are the basics of Destandau’s technique in spine surgery (Fig. 25.3, Fig. 25.4, Fig. 25.5).