Introduction

The aging spine typically begins with disc degeneration and annular dehiscence, followed by transfer of loads from the anterior spinal column to the facets. This may produce discogenic pain and axial back pain, resulting in segmental instability with resultant deformity. If the condition becomes painful, and nonsurgical treatment is not effective, traditional surgical treatment has been limited to diskectomy and fusion. Though diskectomy has been shown to be beneficial by the SPORT¹ study, the long-term cost-effectiveness of fusion is questioned. Traditional spine surgery to treat painful degenerative disc disease such as with herniated discs, spondylolisthesis, central spinal stenosis, and neuroforaminal stenosis encompasses many different techniques. Surgical treatment, however, often results in a “failed back surgery syndrome” (FBSS) with limited success for subsequent salvage procedures. Newer minimally invasive techniques, in skilled and experienced hands, when approaching the pathology along natural muscle and tissue planes opens the door to earlier and a greater number of minimally invasive surgical options for the painful, aging spine without excessive concern about the paradoxical effects of surgery. The concept of “endoscopic surgical pain management” is addressed in this chapter, based on the senior author’s (ATY) 20-year experience using his percutaneous endoscopic transforaminal surgical technique described as the YESS (Yeung Endoscopic Spine Surgery) procedure.

The YESS procedure eliminates the pain generator causing the pain syndrome, not just “masking” the pain with therapeutic injections. The approach accomplishes disc decompression by “selectively” removing degenerative nucleus, sealing and closing annular tears, decompressing spinal nerves, ablating nerves and inflammatory tissue contributing to discogenic and axial back pain, and surgically removing a wide spectrum of disc herniations. In more advanced stages, lumbar spondylolysis and isthmic and degenerative spondylolisthesis can also be addressed surgically. This brief overview provides examples of conditions that the senior author has treated endoscopically with minimal surgical morbidity, in contrast with the much more invasive traditional option. The reader is directed to the published references for more detailed information on the evolution of this new minimally invasive and innovative technique.^2–15

Traditional surgical correction in the aging spine usually involves open decompression, fixation, and fusion techniques. The percentage of fusion surgeries for these conditions as a whole has increased dramatically in the United States over the past few decades. Between 1990 and 2001, lumbar fusion surgery increased 220%.¹⁶ A recent article by Tosteson and colleagues,¹⁷ examining the data from the SPORT trial, concluded that even for degenerative spondylolisthesis surgery (decompression and fusion) is not a cost-effective procedure, when examined over a 2-year period. The importance of this data is that it emphasizes the need to better identify the source of back pain and sciatica, possibly earlier treatment, and more thorough study of the complex innervations of the spine in the foramen (Figure 64-1A-C). This area, known as the “hidden zone” of MacNab, holds the answer to the effectiveness of foraminal decompression and ablation of foraminal nerves in the treatment of discogenic and facet pain. It may have an impact on health care reform that seeks to reduce the cost of care, because over 100 billion dollars a year is spent on back pain in the United States, most of it being spent on nonsurgical treatment such as physical therapy, interventional pain management, and over-the-counter and prescription drugs. We also need to reduce the need for fusion as a surgical solution for pain. This can be accomplished if we are able to not only demonstrate the efficacy and cost-effectiveness of endoscopic surgical pain management, but help establish a new subspecialty in endoscopic surgical pain management, because it requires special training to acquire proficiency.

FIGURE 64-1 A, Fresh cadaver dissection of dorsal and foraminal anatomy showing the relationship of the disc annulus, spinal nerves, facets, and lamina dictating surgical access. Normal left foraminal anatomy L2-S1. Blue: hubbed needles are inserted into the disc space in the foramen accessing the posterolateral quadrant of the disk. Note the furcal nerve branch at L4-L5. The epidural space can be reached with a far lateral trajectory and/or by removing the ventral facet with trephines, lasers, or endoscopic high-speed diamond burrs. All soft tissue has been stripped from the transverse processes, including dorsal ramus innervation of the dorsal column. The intertransverse ligament covering the exiting nerves in the foramen has been stripped away. B, Facet innervation and the relationship of the transverse process, the interspinous ligament, and the exiting nerve in the foramen. The right exiting nerve at L3-L4 exhibits a furcal nerve branch traversing the foramen in the far lateral quadrant of the L3-L4 disc annulus. Furcal nerves are the myelinated branches of normal spinal nerves (usually the exiting nerve), commonly seen endoscopically in the foramen. When stimulated or cut, these nerves can cause dysesthesia and react like the parent spinal nerve. It does not respond like the main nerve because it is usually too small to be detected by continuous intraoperative electromyography or radicular pain reported by the patient. The endoscopic surgeon should take care to recognize and not injure these furcal nerves if they are more than 1 mm in diameter, but they cannot always be avoided. Dysesthesia, immediately postoperative or delayed, is readily treated by transforaminal epidural blocks combined with sympathetic blocks. Furcal nerves can be responsible for sciatica that is seemingly out of proportion to what is suggested by relatively normal MRI appearance, and may be part of the sciatica reported preoperatively. Note also the proximity of the intermediate and lateral branches of the dorsal ramus on the cephalic edge of the transverse process at L3. The dorsal ramus sends a medial branch that crosses the transverse process on the way to innervate the facet joint above and below the disc level. Irritation of the lateral branch, when irritated, can cause muscle spasm and an involuntary list. C, Dorsal ramus innovation of L3, L4, and L5 facets. The dorsal ramus emanating from the origin of the spinal nerve sends off medial, intermediate, and lateral branches to innervate the facets and the dorsal muscle column. The interspinous ligament has been removed to expose the dorsal ramus. It is found just ventral to the intertransverse ligament and can irritate the exiting nerve and its dorsal root ganglion. This poorly studied nerve can be responsible for severe chronic axial back pain associated with a degenerating disc exhibiting grade IV and V far lateral annular tears. Back pain, not just sciatica, caused by disc protrusions and annular tears can be explained by irritation of the dorsal ramus, not just the spinal nerves. Selective endoscopic diskectomy and thermal annuloplasty can reduce axial back pain and sciatica, and Intradiscal Electrothermic Therapy (IDET) cannot reach these nerves! Endoscopic rhizotomy of the branches of the dorsal ramus has shown to be a very effective means of decreasing chronic severe axial back pain.

Understanding chronic, surgically treatable back pain begins with understanding common lumbar pain. Cadaver microdissection of the nerves in the foramen reveals an extensive network of nerves arising from the spinal cord, splitting into the dorsal and ventral rami before exiting the foramen as the spinal nerve. A ramus communicans connects with the sinuvertebral nerves innervating the annulus. When there is an inflammatory response to annular tears with the development of an inflammatory membrane, the subsequent neo-neurogenesis and angiogenesis response contributes to pain that is not detected by imaging studies currently available. Better soft tissue imaging and imaging of chemical changes in the spine may help. We traditionally only grossly see the traversing and exiting spinal nerves as surgeons, and routinely fail to recognize and miss the relatively common furcal nerve, or the dorsal ramus and its medial and lateral branches that emanate from each spinal nerve. This network of nerves from the dorsal ramus contributes greatly to chronic discogenic and axial back pain not responsive to nonsurgical treatment. It is undetected by MRI or CT scan, but can be visualized endoscopically and confirmed by meticulous cadaver dissection (Figure 64-1B, C). Rational treatment calls for the appropriate and effective use of diagnostic and therapeutic diagnostic procedures such as diskography, selective nerve root blocks, foraminal epidural steroid blocks, facet and medial branch blocks, and sympathetic nerve blocks. Research studies, such as those by Caragee¹⁸, that emphasize the risks and the difficulty of interpretation of diagnostic tests such as diskography without balancing the indications and usefulness of the diskography, does a disfavor to endoscopic minimally invasive surgeons who are able to look at pathoanatomy and are skilled at spinal endoscopy. This skill affords endoscopic surgeons the opportunity to treat lumbar pain and sciatica without fusion.

The politics and social-economic pressures of medicine create even more controversy as poorly qualified “experts” provide personal opinion on “standard of care” in medical-legal and insurance coverage disputes.

The information obtained from these diagnostic and therapeutic injection procedures allows the surgeon to more selectively pinpoint the pain source and to determine how to mitigate the source of pain.

Indications and Contraindications

A widely accepted indication for foraminal endoscopic disc surgery is currently a foraminal or extraforaminal lumbar disc herniation. All sizes and types of herniations, however, are possible in the hands of a skilled and experienced endoscopic surgeon. Indications rely heavily on the skill and experience of the surgeon, as well as the patient’s anatomy relative to the location of the herniation and the ability to access the herniation. Indications may also depend on injection and imaging studies to identify a painful condition of the disc. The painful condition is currently identified by preoperative diagnostic and therapeutic injections such as evocative chromo-diskography, foraminal epidurography, therapeutic foraminal blocks, or selective nerve root blocks. Small disc herniations with sciatica, herniations with predominant back pain from the herniation, and annular tears that cause chemical sciatica that may be considered relative contraindications for traditional surgery because of the surgical risk-benefit ratio of the procedure, but may be an indication for foraminal endoscopic surgery. Any condition that obviously benefits from intradiscal therapy such as intradiscal debridement of diskitis is best performed percutaneous transforaminally. Contraindications are relative, dependent on percutaneous access to the pathoanatomy and the interventionalist’s experience. It is not unusual to find pathoanatomy, such as chronic granulation and inflammatory tissue in the disc or furcal nerves in the foramen, that is not apparent on preoperative imaging studies, but is clearly visualized endoscopically during foraminal endoscopic surgery.

Description of the Device

The design of the endoscope and endoscopic system is an important factor for endoscopic surgeons to consider. Techniques of endoscopic decompression vary depending on the endoscope design, the available surgical instruments, and surgical techniques practiced by the developer of the system. Not all endoscopic systems are designed for or amenable to the technique described here, but techniques and endoscopic systems continue to evolve. This chapter specifically describes the YESS transforaminal “inside-out-technique,” utilizing the YESS foraminoscope (Figure 64-2) and the instruments designed for the system and technique. Not only is it important to have the necessary instruments, but specially configured cannulas are designed to expose the pathoanatomy to be surgically treated but, in the process, also protect vital anatomy such as the nerve and dura. Other systems are also evolving, so that in time, there will be similarities evolved and copied from the YESS transforaminal technique illustrated here.

FIGURE 64-2 Richard Wolf YESS Multichannel Operative Endoscope. The spinal endoscope is designed with an operative channel, multichannel irrigation for improved visualization, and a cannula system configured to enhance surgical access to pathoanatomy while protecting sensitive anatomy such as spinal nerves.

(Reprinted from Yeung CA, Hayes VM, Siddiqi FN, Yeung AT. Lumbar endoscopic posterolateral (transforaminal) approach. In Motion preservation surgery of the spine. Yue JJ, Bertagnoli R, McAfee PC, An HS (eds). Philadelphia, Saunders/Elsevier, 2008.)

Background of Scientific Testing and Clinical Outcomes

Peer-reviewed literature for disc herniation, first reported by Mayer and Brock¹⁹ in 1993³ then by Hermantin² in a prospective randomized study, has concluded that the results with transforaminal endoscopic (coined “arthroscopic” by Kambin²⁰) diskectomy in the lumbar spine are generally similar to those with open diskectomy, but with significantly less surgical morbidity and quicker recovery (Table 64-1). The YESS technique evolved from the original Kambin technique as Yeung originally learned from Kambin. The procedure, done on an outpatient basis, utilizes local anesthesia with sedation. Patients are usually discharged an hour after surgery. Results show that patients use less postoperative pain medication and return to work within 1 to 6 weeks. It is not unusual for individual patients to return to work in a matter of days. Long-term follow-up has demonstrated decreased recurrence (6%), less postlaminectomy syndrome, and greater patient satisfaction overall. Morganstern, a student of Yeung²¹, has reported⁶