Endoscopic spine surgery has become a practical, minimally invasive technique for decompression in patients with spinal disc herniation or stenosis. This review aimed to summarize the current techniques of endoscopic decompression technique in spine surgery and to discuss the benefits, limitations, and future perspectives of this minimally invasive technique. Endoscopic spine decompression surgery can be categorized according to the endoscopic property: percutaneous endoscopic (full-endoscopic), microendoscopic, and biportal endoscopic. It can also be classified based on the approach: transforaminal, interlaminar, anterior, posterior, and caudal approaches. Theoretically, each technique can be applied in the lumbar, cervical, and thoracic spine. The various endoscopic spine surgery techniques should be appropriately conducted according to the disease entities, level, and zone of pathologies. Although the current level of evidence is relatively low and the relevance of the technique is controversial, recent clinical results and the critical concept are promising. Development in optics, instruments, and approach will improve its safety and reduce technical complexity. In the meantime, high-quality clinical studies, including randomized trials and meta-analyses, are due for publication. Eventually, endoscopic spine surgery is expected to become the golden standard for spinal surgery.
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Endoscopic spine surgery, in this viewpoint, can utilize the essential concept of MISS. Use of endoscopic technology in spine surgery can offer a minimally invasive, percutaneous approach rather than the wide-open surgical exposure ( 3 , 4 ). It may also provide an excellent and selective visualization of the lesion. Until now, most endoscopic spine surgeries have been developed for endoscopic discectomy or decompression techniques.
Minimally invasive spine surgery (MISS) has become a mainstream concept in spine medicine. Back or neck pain with radiculopathy is one of the common reasons for patients to opt for extensive treatment, and conventional surgical procedures for spinal disc disease or stenosis include open decompression with or without fusion surgery. However, perioperative complications and prolonged recovery time after surgery have emphasized the need of MISS ( 1 , 2 ). The goal is to minimize normal tissue trauma during the surgical approach while providing the same therapeutic effect. As a result of MISS, the patient can return to normal life earlier with less adverse impact and maintain a high quality of life.
The caudal approach, or trans-sacral approach, involves insertion of the small fiberoptic endoscope, or epiduroscope, through the sacral hiatus. This concept of the approach is similar to that of cardiac or cranial vascular intervention. However, the surgical space is very narrow, so the used endoscopic system is small and limited. Therefore, the definitive decompression effect is limited to small disc herniation at the current technical status ( ).
In the case of foraminal disc herniation or foraminal stenosis in the cervical spine, the posterior percutaneous endoscopic cervical foraminotomy and disc decompression can be more effective. The percutaneous endoscopic approach is easier, and the bony foraminal decompression is feasible with endoscopic burrs ( ).
The standard surgical option for cervical disc disease is anterior cervical discectomy and fusion. Likewise, the anterior percutaneous endoscopic approach may be the standard technique for endoscopic cervical decompression technique. The targeting and disc decompression are relatively easier without thecal sac retraction ( ).
This technique is characterized by a percutaneous posterior or interlaminar approach to the epidural space or disc pathology. The interlaminar approach is familiar to general spine surgeons, because it is similar to that of open microscopic lumbar/thoracic decompression. The decompression processes are also similar to those of open microscopic decompression ( ).
The transforaminal approach refers to a posterolateral percutaneous approach to the disc or epidural space through the foraminal window while preserving the normal musculoskeletal structures. The most critical benefit of this approach is that it may provide direct access to the pathologic point without requiring a large skin incision, wide muscle retraction, unnecessary bone resection, and general anesthesia ( ).
The third category of the endoscopic spine surgery is characterized by the use of an endoscopic or arthroscopic system with separate optical and working channels ( 13 - 16 ). This concept is similar to arthroscopic joint surgery, wherein two working portals are needed: the endoscopic portal and the instrumental portal. The endoscopic portal is used for viewing of the surgical field with constant saline irrigation, whereas the instrumental portal is used for surgical instrumentation and procedure ( ).
The second most frequently used endoscopic device is the microendoscopic system. This category involves using a rigid endoscope (microendoscope) attached to a tubular retractor with tissue dilators, which help minimize muscle retraction ( 9 - 12 ). The most commonly used system is the METRx tube assembly ( ). However, unlike the other endoscopic systems, this system is not a water-based procedure, and constant saline irrigation is not used. In real practice, it is frequently applied as a minimally invasive microscopic surgery with a tubular retractor system instead of an endoscopic assembly.
The most commonly used system in endoscopic spine surgery is the percutaneous endoscopic or full-endoscopic system. This is typically characterized by the following ( 5 , 6 ): (I) use of a working channel endoscope with the working channel and the optics in the same tubular device; (II) complete percutaneous approach with a stab skin incision, and (III) utilization of a monoportal approach with continuous saline irrigation. This technique was developed in the mid-1980s and has become the standard endoscopic spine surgery ( 3 , 4 , 7 , 8 ) ( ).
In terms of spinal disease for endoscopic spine surgery, there are two major disease entities: disc herniation and stenosis. Any thecal sac or nerve root compression due to herniated disc or spinal stenosis can be the primary candidate for endoscopic decompression techniques. Generally, endoscopic decompression techniques are not suitable for other spinal conditions, such as segmental instability, tumor, trauma, infection, and deformity. The most basic level for endoscopic decompression is the lumbar or lumbosacral level, followed by the cervical and thoracic levels. The approach can be variable based on the purpose of the surgery: transforaminal, interlaminar, anterior, posterior, caudal and other approaches. The last and most critical factor for categorization is the used endoscopic property: percutaneous endoscope, microendoscope, biportal endoscope, and epiduroscope.
Until now, many kinds of endoscopic decompression techniques have been introduced. Among them, the following methods have been the most commonly studied and applied in real practice throughout the history of endoscopic spine surgery: percutaneous endoscopic lumbar discectomy (PELD), percutaneous endoscopic decompression (PED) for lumbar stenosis, and percutaneous endoscopic cervical discectomy (PECD).
Transforaminal PELD is the representative endoscopic spine surgery with a long history and full application. The initial indication of this technique was soft lumbar disc herniation in various situations. Given the advancement in endoscopic technology, its practical application has widened, and has included migrated, recurrent, foraminal, extraforaminal, and even partially calcified disc herniations. This technique has been proven by many randomized trials, meta-analyses, and systematic reviews (17-24). The basic concept of this technique is the direct access to the disc pathologies through the intervertebral foramen or safety working zone while preserving the normal tissues. It could be argued that this is the best technique for implementation of MISS.
The patient is placed in prone position on a radiolucent table. The procedure is usually performed under local anesthesia or conscious sedation. A posterolateral transforaminal lumbar approach is performed under fluoroscopic control. The approach needle is inserted into the herniated disc through the foraminal window, avoiding the exiting nerve root. After discography, the needle is replaced serially by the guidewire, dilator, and final working cannula. Then the working channel endoscope is inserted, and a selective discectomy and epidural decompression can be performed. Success can be achieved through the following technical keys: precise discrimination of endoscopic anatomy, the release of annular anchorage, and removal of the whole herniated fragment. First, the anatomical layers, including the herniated disc, annular fissure, posterior longitudinal ligament, and neural tissues, should be discriminated precisely. Second, the herniated disc fragment should be released from the annular anchorage or adhesion using micropunches and annulus cutter. Third, the released hernia fragment should be removed entirely without any loose pieces in the epidural and intradiscal space. Finally, the endpoint of the procedure should be adequately determined by a free mobilization of the neural tissue and strong pulsation of the dural sac.
The most common pathology of the lumbar lateral recess stenosis and foraminal stenosis is hypertrophy of the superior articular process (SAP). As a result, the traversing nerve root is compressed in the lateral recess stenosis and the exiting nerve root is compressed in the foraminal stenosis. The transforaminal endoscopic approach can be suitable for the treatment of the lateral recess/foraminal stenosis by resection of the hypertrophied SAP.
Unlike PELD, the working cannula is usually docked within the foramen, not in the disc space, in PED. The safety docking zone of the working cannula is the caudal surface of the SAP and pedicle. This is the typical out-to-in technique described by Schubert and Hoogland (25-27). The tip of the SAP may be typically removed by a bone trephine or endoscopic burrs. After sufficient removal of the bony stenosis, the exposed ligamentum flavum can be subsequently removed by micropunches or forceps. For the lateral recess stenosis, the caudal part of the foramen and the traversing nerve root are decompressed, whereas for the foraminal stenosis, the cranial part of the foramen and the exiting nerve root are decompressed. Additional pedicle resection may enhance the decompression effect. The key to success in this technique is the adequate landing of the working cannula and sufficient decompression of the critical point, which is usually located around the hypertrophied SAP and thickened ligamentum flavum. The technical difficulties that interpose with complete decompression are safe engagement of the working cannula within the foramen, extraforaminal or epidural bleeding, and confusion in the endoscopic anatomical discrimination. Therefore, this technique is regarded as more challenging than the standard endoscopic discectomy.
In fact, the interlaminar PELD was developed for lumbar disc herniation at the L5–S1 level with high iliac crest. In this case, a usual transforaminal approach is difficult or even impossible. Some expert surgeons developed the interlaminar approach to overcome this problem (28,29). They found that the interlaminar space of the L5–S1 level is usually large enough to pass the endoscopy and working cannula. This technique uses a posterior interlaminar approach with the small working cannula in the epidural or intradiscal space, while preserving paraspinal musculatures and lamina. It can also be applicable to the other levels by using endoscopic punches or drills to enlarge the interlaminar space for introduction of the working cannula and instruments. A standard spine surgeon can be more familiar with the interlaminar approach than the transforaminal approach. In fact, the presence of the innocent exiting nerve root during the transforaminal approach can be stressful for the endoscopic spine surgeons. This technique has evolved and eventually become the interlaminar endoscopic lumbar decompression technique for lumbar stenosis.
As the size of the working channel endoscope and associated instruments became bigger, a definitive endoscopic decompression technique for lumbar central or lateral recess stenosis was developed.
The definitive indications for interlaminar PED are as follows: (I) central or lateral recess stenosis on magnetic resonance imaging (MRI) and computed tomography (CT) scan without a foraminal stenosis; and (II) neurogenic claudication with leg pain with or without motor weakens.
The surgical technique can be performed using the standard method described in previous studies (28,29). The patient is placed in a prone position under general or epidural anesthesia. The initial target point is the lateral edge of the interlaminar window. After serial dilation, the final working cannula was placed on the lamina surface. Endoscopic laminotomy was performed from the medial border of the superior facet using the endoscopic burr and bunches. Decompression can proceed including cranial and caudal laminotomy, medial facetectomy, and removal of the ligamentum flavum. In the case of bilateral decompression, further decompression of the contralateral side is needed after ipsilateral decompression. The endoscope and the working cannula were directed toward the contralateral side, dorsal to the dural sac. At this point, it is better to leave the ligamentum flavum intact to protect the dural sac during the contralateral laminotomy. The undercutting technique over the ligamentum flavum should be performed until the medial aspect of the contralateral facet can be reached. The remaining ligamentum flavum is then completely removed using the endoscopic punches and other supplementary instruments. All surgical fields were manipulated under endoscopic visual control and constant saline irrigation.
The main disease entity for PECD is soft cervical disc herniation with or without foraminal stenosis. The following two approaches are used for cervical disc herniation: anterior and posterior. The approach direction can be determined according to the zone of disc pathology. The anterior approach is effective for cervical disc herniation cases in which the main herniation is located medial to the lateral edge of the myelon.
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Anterior endoscopic decompression for the cervical level has theoretical benefits compared to the lumbar level (30). First, the cervical nerve root is usually confined to a smaller space. Second, a slight volume reduction leads to a more significant effect. Third, topographically, the approach is performed in an anterior-posterior direction. Thus, targeting is more comfortable and more precise. Any zones of disc herniation can be treated with anterior PECD, including central, paracentral, and foraminal disc herniations. It also has typical advantages of the minimally invasive percutaneous approach. Minimal skin incision and muscle retraction may reduce the risk of hematoma, infection, vocal cord palsy, and injury of significant structures, such as the carotid artery, trachea, and esophagus. The procedure can be performed under local anesthesia. Therefore, it will be useful for the elderly or medically compromised patients. However, there are some limitations associated with this technique. First, the central nucleus may be disrupted by the anterior percutaneous approach, thereby postoperative disc space narrowing or instability may occur. Second, this approach cannot be applied in case of disc space narrowing or advanced spondylosis.
The general indications for anterior PECD were as follows: (I) soft cervical disc herniation at any zone of the cervical disc; (II) unilateral cervical radiculopathy without central stenosis or foraminal stenosis.
The surgical technique was performed using the standard method described in previous studies (31-33). The patient was placed in a supine position, and the procedure was performed under local or general anesthesia. The approach needle was inserted from the contralateral side to the intradiscal space through a safe working zone between the carotid artery and the tracheoesophagus. After a serial dilation process, the final working cannula was placed intradiscally with the tip of the working cannula on the posterior vertebral line. A working channel endoscope was then inserted, and the intradiscal structures were examined. Then, a selective discectomy was performed using endoscopic forceps and supplementary radiofrequency or laser. The anterior and central nucleus should be preserved to avoid postoperative disc collapse, while the herniated fragment at the posterior part of the disc is completely removed.
The overall success rate of the anterior PECD is variable from 51% to 95% (30-33). According to the randomized trial of Ruetten et al. (34), the anterior PECD technique is a sufficient and safe alternative to conventional surgery with benefits of minimally invasive intervention when the indication criteria are fulfilled.
The main target for this procedure is foraminal cervical disc herniation or foraminal stenosis. Given that the cervical spinal cord should not be retracted medially, the posterior approach is useful for cervical disc herniation, in which the primary pathology is located lateral to the lateral edge of the myelon. The main indications for posterior PECD are as follows: (I) foraminal/lateral cervical disc herniation; (II) unilateral cervical foraminal stenosis with intractable cervical radiculopathy.
The surgical procedure can be performed according to the standard technique (35). The procedure is performed under general or local anesthesia, with the patient placed in a prone position. The main target point of the approaching needle is the laminofacet junction (so-called “Y-point”). After serial dilation, the final working cannula is placed on the laminofacet junction under fluoroscopic guidance. A working channel endoscope is then introduced and the bony structures were examined. The foraminal unroofing and foraminotomy are then performed using endoscopic burrs around the Y-point. The extent of facet removal is limited to 50% of the facet joint (36). After adequate foraminotomy, a selective endoscopic discectomy is performed. After identification of the exiting nerve root, the extruded disc can be removed using a dissector and forceps. The endpoint of the procedure can be achieved by free pulsation or mobilization of the nerve root from the proximal to the distal exiting zone.
The clinical outcomes of the posterior PECD technique have been reported to be comparable to those of open cervical surgery (35,37). According to the randomized trial of Ruetten et al. (35), the posterior PECD can be an effective alternative to conventional open surgery in adequately selected cases.
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Richard Wolf offers a hands-on in-service session with a Richard Wolf expert. One of our knowledgeable clinical specialists, our clinical educator, or a sales representative will perform in-depth training on the proper handling of your instruments, including a competency skills test for successful completion.
For a hands-on departmental training session on our rigid endoscopes, Richard Wolf provides the Care and Handling of Rigid Endoscopes training and competency packet that includes the following:
DVD: Care and Handling of Rigid Endoscopes, 15 min.
Leave Behinds: Three wall posters that outline key components of the care and handling process―laminated, full color, 12" x 18" wall posters on Patient Care, Decontamination, and Assembly and Sterilization.
Two print collateral documents: 8½" x 11", informative and instructional guides on the care and handling of Richard Wolf endoscopes.
Essential Information for Rigid Endoscope Reprocessing outlines the approved chemicals and techniques for reprocessing a Richard Wolf rigid endoscope.
Orientation and Annual Review Guide focuses on documenting staff competency.
Additionally, we have a departmental training session on our flexible endoscopes that includes the Care and Handling of Flexible Endoscopes training and competency packet containing:
DVD: Care and Handling of Flexible Endoscopes, 18 min.
Leave Behinds: Four wall posters that detail key reprocessing steps―laminated, full color, 12" x 18" wall posters on Patient Care, Decontamination, Assembly, and Sterilization.
Two print collateral documents: 8½" x 11", educational guides on the care and handling of Richard Wolf endoscopes.
Essential Information for Flexible Endoscope Reprocessing covers the approved chemicals and machines to reprocess Richard Wolf flexible endoscopes.
Orientation and Annual Review Guide assists you with documenting staff competency.
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