Lumbar Spine

Lumbar Endoscopy: Historical Perspectives, Present & Future

Kai-Uwe Lewandrowski¹, ², ³, *, Jin-Sung Kim⁴, Friedrich Tieber⁶, Anthony Yeung

¹ Center for Advanced Spine Care of Southern Arizona and Surgical Institute of Tucson, Tucson AZ, USA

² Associate Professor of Orthopaedic Surgery, Universidad Colsanitas, Bogota, Colombia, USA

³ Visiting Professor, Department Orthopaedic Surgery, UNIRIO, Rio de Janeiro, Brazil

⁴ Professor, Spine Center, Department of Neurosurgery, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea 222 Banpo Daero, Seocho-gu, Seoul, 137-701, Korea

⁵ Clinical Professor, University of New Mexico School of Medicine, Albuquerque, New Mexico Desert Institute for Spine Care, Phoenix, AZ, USA

⁶ Am Webereck 6 1/2 - 86157 Augsburg, Germany

Abstract

Endoscopy of the lumbar spine has traditionally found much broader adoption than those endoscopic procedures of other areas of the spine. Initially, a herniated disc was the target of endoscopic spine surgery techniques. Stenosis indications were later identified as technological advancements permitted. Many endoscopic spinal surgeries commenced in the domain of interventional pain management. Lasers and radiofrequency were applied to some of the procedures that nowadays are aided by direct videoendsocopic visualization of the painful pathology. In this chapter, the authors briefly reviewed the history of spinal endoscopy and its key opinion leaders. Giving credit to the most prominent pioneers of this fast-moving field sets the stage for what the reader is about to discover in this most-up-to-date publication: Contemporary Spinal Endoscopy: Lumbar Spine.

Keywords: Lumbar spine, disc herniation, stenosis, impingement, degeneration, decompression, open, minimally invasive, endoscopic, historical considerations, lasers, radiofrequency.

* Corresponding author Kai-Uwe Lewandrowski: Center for Advanced Spine Care of Southern Arizona and Surgical Institute of Tucson, Tucson, AZ, USA, Department of Orthopaedic Surgery, UNIRIO, Rio de Janeiro, Brazil and Department of Orthoapedic Surgery, Fundación Universitaria Sanitas, Bogotá, D.C., Colombia, USA; Tel: +1 520 204-1495; Fax: +1 623 218-1215; E-mail: [email protected]

INTRODUCTION

Many historical perspectives have been revisited by repurposing existing technologies in new surgical approaches within the last ten years, during which spinal endoscopy has gained significant traction among spine surgeons. Likewise, have we witnessed the resurgence of previously employed surgical techniques that have been applied in the early years of spinal endoscopy. As in the fashion industry, where specific trends reappear in a modernized form by fusing different design elements or materials to create new products and marketing strategies, spine surgeons are similarly susceptible to embracing modern trends in spinal endoscopy in their quest to overcome shortcomings of existing treatment protocols for common degenerative conditions of the spine. Industry recycles existing medical know-how and often modernizes them by technology transfer from other commercial areas, such as the aerospace or the automotive industry, by innovation mechanisms of adoption, miniaturizations, automation, and system integration to develop advanced surgical instruments-, and equipment of improved performance, reliability, and durability. Innovations widely adopted in other industries are making their way into medical applications. Examples include high-definition (HD) video technology with touch-screen displays, high-speed HD recording equipment, robotics- and navigation tools, 3D heads-up display goggles for surgeons to be worn during surgery to improve eye-hand coordination, and many others. Rapid endoscopic spine surgery product development with a myriad of instruments being pushed by an army of sales associates is another area of rapid change that has been playing itself out in the operating room — endoscopes with larger inner working channels, sturdy enough to withstand the abuse of more frequent short sterilization cycles to respond to the rising caseload, motorized shavers, drills, and large Ø rongeurs employed during rapid decompression. Endoscopes previously rated for 200 to 250 simple discectomy surgeries are now used in more complex and demanding advanced endoscopic spine procedures. These include intradiscal therapies with heat-generating lasers or radiofrequency devices for the early stages of the disease and the late stages where aggressive decompression and reconstructive procedures may be needed for spinal stenosis instability-related neural element encroachment. Endoscopic placement of spinal implants, such as interbody fusion cages and posterior supplemental fixation with pedicle screw-rod constructs, are other examples of contemporary advancements in endoscopic spinal surgery. This increasing quality and durability demand on spinal endoscopes to work in a large variety of surgical indication scenarios has widened the field of industry competitors, with some front-runners pushing clinical product portfolios, reimbursement, and coding agendas. Traditional German endoscopic equipment makers are being displaced in China, Korea, and Japan by domestic Asian manufacturers whose technological know-how has now risen to a competitive level at lower acquisition costs. In some cases, Asian spinal endoscopy, radiofrequency, and motorized decompression equipment have even advanced beyond what European competitors can put forward, mainly because of progressive clinical agendas with broader indications for endoscopic spinal surgery.

Whether all of these innovations are genuinely impactful and leaps forward that ultimately improve patient outcomes and are not just vogue trends at an increased cost to patients and the health care system, on the whole, is not always obvious and often requires vetting them in the operating room with investigational clinical studies - all of which requires clinical testing, resources, and most of all, time. Spine surgeons have little of the latter and, by their very nature, may be innovation enthusiasts in their quest to overcome shortcomings of existing clinical protocols.

The authors of this chapter attempted to put some of these new trends in perspective within the historical context of spinal endoscopy by reviewing the contributions of some of the early key players in an attempt to help the aspiring endoscopic spine surgeon to position her-, or himself in the increasingly complex field of surgical procedures. With spinal endoscopy becoming more mainstream, many North American and European national and international spine surgeons' organizations are struggling with its adoption. They have just begun to embrace it by spelling out clinical treatment guidelines and figuring out how to establish an accredited core curriculum with validated training programs. On the contrary, if endoscopic spinal surgery training had made it into the mainstream core curriculum many years ago, informal education sources would be less and less relevant. For the time being, many novice endoscopic spine surgeons in many parts of the world – particularly in North America and Europe - have to rely on an industry-sponsored weekend cadaver- and other short instructional courses. While some of them are lucky enough to be mentored by veteran key opinion leaders (KOLs), the vast majority - by default - are autodidacts and primarily self-taught, having to go through an endoscopic learning curve that many find out is steeper than with other procedures they are routinely performing.

THE TRANSFORMATION

The final goal of spinal surgery is to decompress neural elements and stabilize unstable spinal motion segments. Traditionally, this required extensive exposure and stripping of soft tissues, which in turn may devitalize and degenerate the very structures whose integrity is paramount to maintaining a healthy spinal motion segment. Problems such as post-laminectomy instability and epidural fibrosis have long been recognized as some of the potential follow-up problems that could arise from traditional open spinal surgery [1-3]. Other well-recognized problems include disruption of vascular supply and denervation of paraspinal muscles with resultantly decreased trunk strength and chronic pain syndromes that at least in part arise from extensive spinal exposures [4]. At ten years, the cumulative rate of development of adjacent level disease in the cervical and lumbar spine in previously healthy spinal motion segments adjacent to fusions has been reported to be as high as 25%. This is not a small number, and recognition of this problem has prompted surgeons to look for alternative ways to accomplish the two fundamental goals of each spinal surgical procedure: Neural element decompression and stabilization of unstable motion segments [5-8].

From the patient’s point of view, reducing blood loss and surgical time, with rapid recovery and return to work, are clear advantages that are now being openly discussed. With the overall online availability of educational information, patients have become more educated, curious, at times critical, and hopeful that their specific problem can be solved with less aggressive procedures. To many patients, spinal endoscopy intuitively presents itself as such a solution. From a surgeon’s point of view, these advantages are no less critical as they lessen the burden to patients and drive patient satisfaction: lower blood loss, complications, infection rates, faster return to work, and social reintegration. Less time to narcotic independence are clinical upsides of spinal endoscopy that can easily be communicated to patients, families, and in due to time to hospitals, health insurance companies, and third-party payers, who still frequently deem spinal endoscopy as an experimental procedure. Since the first edition of Spinal Endoscopy, several high-grade clinical evidence studies have been published. A large body of literature on spinal endoscopy has emerged out of Asia and China in particular. In North America and Europe, however, spinal endoscopy is still yet to be included in treatment and coverage guidelines despite a substantial increase of peer-reviewed journal articles on the safety, efficacy, and equivalency of endoscopic decompression to other minimally invasive (MIS) and open spinal surgeries. Regional variations of the degree of acceptance and utilization of endoscopic spine surgery and changes from the previously dominating transforaminal to the now more popular interlaminar and full endoscopic approach have been discovered. The differences in the surgeon’s endoscopic approach preference reflect a shift to more complex decompression and reconstructive procedures. Historically a method developed for simple discectomies, spinal endoscopy is now the most commonly employed minimally invasive spinal surgery technique the world over which has found use in a much more comprehensive range of surgical application.

HISTORY PERSPECTIVES OF ENDOSCOPIC SPINAL SURGERY

Mixter and Barr, in 1934, performed the first microdiscectomy procedures for radicular pain due to a herniated disc. They reported on 19 patients who underwent laminectomy [9]. The concept of a less aggressive decompression was first introduced by Hult, who performed nucleotomy through an extraperitoneal approach in 1951 [10]. In the 1960s, the concept of chemonucleolysis evolved after Lyman and Smith discovered that percutaneous injection of Chymopapain could hydrolyze a herniated nucleus pulposus in a patient with sciatica due to the herniated disc [11].

In 1973, Parvis Kambin introduced a transforaminal approach using percutaneously placed Craig’s cannula through which he performed microdiscectomy in a non-visualized fashion [12]. Hijikata reported on the non-visualized posterolateral percutaneous nucleotomy in 1975 [13]. William Friedman introduced the direct lateral approach for percutaneous nucleotomy in 1983. A higher rate of bowel injury was noted, though [14]. The introduction of a specially modified arthroscope into the intervertebral disc, and, thus, the first visualized microdiscectomy, was first reported by Forst and Hausman in 1983 [15]. Coaxial endoscopes with a central working channel soon emerged as an alternative to traditional arthroscopic systems, often using a separate tubular working channel for instruments. They were developed because they offered the option to visualize and remove the painful pathology with a wide range of surgical instruments or thermal therapy equipment. Onik described the addition of a motorized shaver in 1985, which led to the coining of the term Automated Percutaneous Nucleotomy [16].

Kambin published his first discoscopic views from within the disc in 1988 and later emphasized the importance of epidural visualization [17]. One year later, Schreiber described the injection of indigo carmine dye into the disc to stain abnormal nucleus pulposus and annular fissures [18]. Kambin also first described the safe or working zone in 1990 as the triangle bordered by the exiting nerve root, the inferior endplate and the superior articular process of the inferior vertebra, and medially by the traversing nerve root (Fig. 1) [19]. Ultimately, a larger diameter working cannula allowed for more sophisticated instruments and endoscopes to be used (Fig. 2) [20].

Fig. (1))

Surgical anatomy of the safe zone: The safe zone is formed by the lateral border of the exiting nerve root above, medially by the border of the traversing root or thecal sack, inferiorly by the endplate and dorsally by the superior articular process of the inferior vertebral body. Safe zone is located within the axilla between the exiting and traversing nerve roots (with permission from R.F. McLain).

Fig. (2))

The safe zone is entered by removing parts of the superior articular process of the inferior vertebral body thus performing a foraminoplasty (with permission from R.F. McLain).

Schreiber and Leu (Zurich) contributed to the development of multichannel endoscopes [18] in cooperation with Karl Storz Endoskopie, Tuttlingen (Fig. 3), and by Hal Matthews in partnership with Danek Inc., Memphis [21-23]. Since the endoscope was directed via the posterolateral approach into the lumbar neuroforamen, the surgical technique was called Foraminoscopy.

Fig. (3))

First Storz™ working channel endoscope developed by Leu.

These authors recognized that it was necessary to direct the foraminoscope in different trajectories to reach all types of a herniated disc in the various foraminal zones and the possible cranial to caudal locations (Fig. 4).

Fig. (4))

Zone classification to describe the location of a herniated lumbar disc proposed by Schreiber & Leu in 1993.

Citation Medical Corp., Reno NV, produced the Danek endoscope. Hal Matthews introduced it at the Laser Conference in 1991 in San Francisco [21]. Its 0°-viewing angle is dictated by the glass fiber bundles used for image transmission. This endoscope allowed the introduction of instruments of up to 3.5 mm. The single-use Danek design failed because of cost and poor image quality. Moreover, it did not fit into the lumbar foramen, and the 0° optic was impractical for visualized treatment of central herniation. It was taken off the market in 1994.

The Leu foraminoscope was designed for the treatment of foraminal and extraforaminal herniations. Karl Storz produced it, and its clinical use was demonstrated by Dr. Leu in 1991 (Fig. 5) [24]. The Storz-built endoscope used a Hopkins rod lens system with a 6° viewing angle acceptable for the chosen indications.

Fig. (5))

The Leu foraminoscope produced by Karl Storz, Tuttlingen, Germany in 1991. It had a Hopkins rod lens system with a 6° viewing, a working length of 145 mm and the inner working channel large enough to accommodate instruments of up to 3.0 mm in Ø.

Karl Storz offered the foraminoscope designed by Hans-Jörg Leu until 2012 when more current products replaced it after a 21-year run. Popular design features included a working length of 145 mm, and an inner working channel Ø of 3.0 mm (Fig. 4). It had several advantages with a brilliant image and the great tools required to do endoscopic discectomy surgery. It could be sterilized and therefore was suitable for multi-use. Moreover, large capital purchases for proprietary videoendoscopic tower equipment were unnecessary since the Leu-designed and Storz-produced foraminoscope easily connected to existing Video Towers. Storz also provided the first interlaminar endoscopic nucleotomy set, popularized by Vogl (Fig. 6).

Fig. (6))

Storz™ interlaminar nucleotomy developed by Vogl.

In 1992, Dr. Thomas Hoogland recognized the need to innovate endoscopic spine surgery beyond the scope of what the Danek foraminoscope was able to do. Shortcomings in the treatment of intracanal, foraminal, extraforaminal herniations with free fragments were the basis for innovations that followed. He first reported the utility of a foraminoplasty to deal with these types of herniations in 1994. His technique deployed reamers and drills over a guidewire introduced over the „Tom Shidi" guide cannula - one of the critical elements of his outside-in technique [25]. A comparison of the specifications of the early foraminoscopes produced between 1992 – 1997 is shown in Table 1.

Table 1 Comparison of specifications of the early foraminoscopes 1992 – 1997.

In 1993, Schreiber started working with large working channel endoscopes allowing direct visualization of annular tears [18]. Kambin and Zhou demonstrated using a 30-degree endoscope, recognizing that lateral recess stenosis can hamper the procedure's effectiveness. In 1996, they established foraminoplasty via endoscopic removal of facet overhang, osteophytes, and annulectomy using specialized forceps and trephines [20, 26]. Foley, Mathews, and Ditsworth published their transforaminal series in 1998 and 1999 [27-29]. In 1998, Yeung introduced The Yeung Endoscopic Spine System (YESS) using a rod-lense multichannel, wide-angled endoscope with integrated suction irrigation channels produced by Richard Wolf [30]. The oval-shaped device had a 207 mm working channel of 2.7 mm Ø suitable for 2.5 mm surgical instruments. The YESS system was designed for the inside-out technique employing foraminoplasty with trephines, lasers, and radiofrequency (Fig. 7) [66].

Fig. (7))

The Yeung Endoscopic Spine System (YESS) produced by Richard Wolf consisted of an oval-shaped multichannel, wide-angled endoscope with a 207 mm working channel of 2.7 mm in Ø for use of 2.5 mm surgical instruments, an irrigation channel, and a rod lens system. It was designed for intradiscal decompression for protrusions, for foraminal and extraforaminal herniations and for foraminoplasty with lasers and radiofrequency.

In 1998, Dr. Hoogland pioneered a multichannel 1.9 mm Ø rod-lens endoscope with a length of 180 mm, and capable of accomodating Ø 3.5 mm instruments. The system had excellent image quality and an irrigation channel and was based on a fiberglass illumination system that came with a 0° and a 30° optic (Fig. 8). To date, this OEM offers still the broadest range of coaxial endoscopes with a working channel in many different lengths, diameters of the inlet, and outer diameter.

Fig. (8))

Hoogland’s multichannel endoscope produced by a German OEM manufacturer in 1998 with the following specifications: length 180 mm, working channel Ø of 3.6 mm for instruments up to Ø 3.5 mm, irrigation channel, 0° and 30° optic fiber glass illumination system, outer Ø 6.3 mm, and 1.9 mm Ø rod-lens system delivering excellent image quality.

In 2001, Knight et al. published on endoscopic foraminoplasty employing a side-firing Ho: YAG laser [31]. The advent of lasers also stimulated electrothermal annuloplasty for low back pain, which Tsou and Yeung described in 2002 [32]. Soon after that, more modern systems were introduced by the senior author of this chapter (Anthony Yeung) in 1998-2002, with the launch of the new Yeung Endoscopic Spine System (YESS), followed by additional decompression instruments and cannula modifications which were designed around the transforaminal endoscopic approach for intradiscal and epiduroscopic procedures [33]. Yeung et al. describe the utility of provocative intraoperative discography, thermal discoplasty, and annuloplasty, annular resection for creating an annular window to perform foraminoplasty using endoscopic Kerrison, abrasive drills, burrs, and lasers. Bipolar electro-frequency probes were introduced by Tsou and Yeung, who performed a thermal electro-annuloplasty for chronic discogenic low back pain. This technique was done on the direct visualization targeting disc nucleus and annular fissures [34]. A variety of intradiscal conditions, including delamination and fissuring and entrapment of herniated disc material into annular fissures, have been described by the senior author of this chapter (Anthony Yeung), who has employed the inside-out technique to diagnose and treat these intradiscal entities.

Another leap forward was achieved by Ruetten et al., who dealt with poor visualization of the epidural space with the popularization of the direct lateral approach with the uniportal use of a foraminoscope [35]. Ruetten and his group also validated the indications of the interlaminar and full endoscopic techniques [36-46]. Hoogland and Schubert dealt with the problem alternatively by describing foraminoplasty with transforaminal reamers in 2005 [47]. This technique made it easier to access sequestered disc fragments that migrated in locations far from the interspace. Lee further analyzed this problem in 2006 and found that patients with severe canal and lateral recess stenosis had less favorable clinical outcomes due to a higher risk for remnant disc fragments responsible for persistent clinical symptoms [48].

Lee et al. also pioneered the definition and application of a classification system for the location of a herniated disc by dividing them into near-migrated (zone two and zone three), and upward (zone one), or downward (zone four) far-migrated disc fragments [49]. The first author’s own clinical experience underlines the importance of using radiographic classification systems for both herniated disc and spinal stenosis. Another chapter of this text demonstrates the utility of a radiographic classification system for foraminal and lateral recess stenosis. The division of the neuroforamen into entry-, mid-, and exit zone is helpful when stratifying patients and selecting appropriate surgical candidates [50].

THE NITZE-LEITER MUSEUM FOR ENDOSCOPY

The International Nitze-Leiter Research Society for Endoscopy houses many historical instruments, writings, and construction drawings. The highlight is the original light conductor by the Frankfurt doctor Philipp Bozzini from 1806. It is recognized in the professional world as the first endoscope, with all the properties still the basis for modern endoscopes today. The collection includes the significant achievements in endoscopy through to the developments of the 20th century. In its entirety, the Endoscopy Museum houses items from the first endoscopic aids to modern endoscopic technologies of the computer age. More than 3000 exhibits show the viewer the milestone development over more than two centuries and many individual pieces (Figs. 9 and 10). Each in itself represents a piece of medical history and shows doctors' will to develop ever-better medical devices to improve the treatment of patients.

Fig. (9))

Shown is an exhibition at The Nitze-Leiter Museum for Endoscopy of the Institute for the History of Medicine at the University of Vienna. The chair has existed since 1848. The museum was opened in 1996.

Particular emphasis is placed in the urology department with urethroscopes, cystoscopes, blind and optical lithotriptors, resectoscopes in various development phases, and gastroenterology esophagoscopes gastro-, recto-colonoscopes, and laparoscopes of all development stages.

Fig. (10))

The Endoscopy Museum has been housed for a long time in the Josefinum since 1920. The building was created in 1785 by Emperor Josef II near the Center of Vienna, Austria.

Donations to the International Nitze-Leiter Research Society for Endoscopy, consisting of instruments, equipment, catalogs, image and video material from closed ordinations, hospital departments, or international instrument manufacturers, as well as numerous bequests, form the holdings of the Nitze-Leiter collection. The collection also contains treasures from the history of bronchoscopy, ophthalmology, gynecology, and ENT. Instruments from international manufacturers provide information about the individual development steps in lighting, optics, and mechanics and show therapeutic applications' progress. With a steady influx of objects, aspects of the more recent endoscopy history are also on display.

THE EVOLUTION OF LASERS IN SPINAL ENDOSCOPY

Lasers have always been appealing for surgeons when applied in minimally invasive procedures. Peter Ascher demonstrated it by employing neodymium:yttrium-aluminum-garnet (Nd: YAG) laser through an 18 gauge needle introduced fluoroscopically into the intervertebral disc [51]. His technique ablated and vaporized intradiscal tissue in short bursts without heat damage to adjacent tissues. This procedure was ideally suitable for an outpatient setting as the patient was discharged off the needle is withdrawn in the puncture wound was covered with a small Band-Aid.

The Ho: YAG laser was compared to the Nd: YAG laser in a clinical trial conducted by Quigley et al. in 1991 [52]. He noted that the Ho: YAG laser was the best to compromise between the efficacy of absorption and the convenience of fiber-optic delivery at that time. In 1990, Davis et al. reported clinical success in 85% of his 40 patients who underwent laser discectomy with the potassium-titanyl-phosphate (KTP 532-nm) laser [53]. Only six of the 40 patients required revision with open discectomy procedures because of clinical failures. In 1995, Casper et al. described using the side-firing Ho: YAG laser [54], which was also employed later by Yeung et al. [55]. At a one-year follow-up, Casper et al. reported an 84% success rate [55]. Siebert et al. published a 78% success rate on 100 patients with a mean follow-up of 17 months treated with the Nd: YAG laser [56].

Mayer et al. were the first to suggest the combined use of an endoscope with laser ablation through an endoscopically introduced fiber. Extensive clinical trials followed and were very supportive of the clinical use of lasers to remove the herniated disc [57]. Hellinger reported in 1999 on more than 2500 patients he treated with the help of the Ascher technique with an 80% success rate over 13 years [58]. Yeung et al. noted an 84% success rate on more than 500 patients he treated with the KTP laser [59].

The current state-of-the-art has been summarized by Ahn et al. in a recent article [60]. Open microscopic laser surgery, percutaneous endoscopic laser surgery, and laser-tissue modulation for spinal pain comprise the three ways lasers are currently applied in interventional and minimally invasive spinal surgery. Ahn et a. encouraged further study of the select clinical indications demonstrating efficacy to substantiate the lack of evidence with randomized clinical trials [60]. A multicenter randomized prospective trial by Brouwer et al. failed to show a difference in clinical outcomes between 57 conventional microdiscectomy patients to another 55 percutaneous laser disc decompression patients [61, 62]. The needle-based (18G) percutaneous laser procedure placed a 600-micron glass fiber into the center of the disc employing a diode laser (Biolitec, 980 nm, 7 W, 0.6 s pulses, interval 1 s) to total energy delivered of 1500 J. Nonetheless, the reoperation rate was higher in the laser group (52%) than in the microdiscectomy (21%) group [63, 64]. The cost-effectiveness of laser- over standard microdiscectomy has been demonstrated for a simple herniated disc. However, it remains to be seen when integrated with an endoscopic platform and applied in more complex clinical scenarios such as foraminal and lateral recess stenosis [65]. At a minimum, the concern for nerve root injury with laser application in the spine remains [66, 67].

RADIOFREQUENCY ABLATION

High-frequency radiofrequency ablation has found several applications in neurosurgery, endoscopic spine, orthopedic and pain management. High (RF) radio frequency with low temperatures has been employed for tissue dissection (monopolar) and coagulating mode (mono and bipolar). Five years ago, when the first edition of Spinal Endoscopy was published, only one radiofrequency product was dominating the market. Nowadays, nearly every vendor selling spinal endoscopes also has a radiofrequency probe in the portfolio produced in-house or by a third party. Typically, radiofrequency probes are compatible with the working channel of the spinal endoscope are used for hemostasis, shrinkage, or ablative effects in the soft tissue to dissect them of a herniated disc.

Radiofrequency ablation of tissues is well accepted in other areas such as plastic surgery, oral maxillofacial surgery, and dental procedures. These devices have found their way into spinal surgery for thermal ablation of disc tissue. With further miniaturization and reduced acquisition costs, they nowadays present an attractive alternative to lasers. While the acquisition cost of lasers nowadays may be comparable to the expense of capital equipment purchase of a complete radiofrequency system, radiofrequency is found in most operating rooms. In a routine clinical application in high-turn-over operating rooms, radiofrequency with disposable probes is perceived more practical by most and less cumbersome. Besides, lasers may impose additional safety issues for patients, surgeons, and supporting staff that does not exist with the radiofrequency application.

The utility of High (RF) radio frequency with low temperatures tissue ablation has been investigated in at least one study. In 2004, Tsou et al. reviewed 113 consecutive patients with a minimum postoperative follow-up of 2 years. Patients were treated for discogenic low back pain [34]. Their clinical analysis showed excellent results in 15%, good in 28.3%, fair in 30.1%, and poor results in 26.5% of patients, respectively. The authors concluded that the treatment interrupted the purported annular defect pain sensitization process [34].

In 2016, Pan et al. demonstrated the benefit of using radiofrequency treatment of annular tears and adhesions to the dural sac due to inflammatory granulomas in 63 consecutive patients with discogenic low back pain [68]. The authors claimed that concordant pain could be triggered by stimulating the inflammatory granulation tissue within the annular tears or between the posterior longitudinal ligament and the dural sac with a bipolar radiofrequency probe. The authors concluded that the debridement of the granuloma with the radiofrequency probe was essential in achieving favorable clinical outcomes. Others have corroborated the observations. In 2013, Wang used radiofrequency to alleviate refractory pain of spinal metastasis patients with ablation during transforaminal endoscopy [69], and Sairyo employed it to treat low back pain in professional athletes [70]. Similar radiofrequency applications were demonstrated in 2016 by Pereira et al. and Bellini et al. They both reported improved clinical outcomes in patients with postoperative epidural fibrosis following epiduroscopic rather than endoscopic visualization [71, 72]. Nowadays, high radio frequency with low temperatures tissue ablation is useful in spinal endoscopy when controlling bleeding and shrinking tissue to facilitate visualization. The need for a modernized radiofrequency application may arise from advances in endoscopic spinal decompression and reconstructive procedures.

NEW LANDMARK CLINICAL OUTCOME STUDIES

Until recently, randomized prospective trials comparing the traditional open versus the endoscopically performed lumbar microdiscectomy procedure were unavailable. Earlier studies, however, suggested that successful outcomes can be achieved. In 2006 and 2007, Choi et al. reported