Introduction

Traditional treatment of low back pain from an aging spine encompasses many techniques. When surgery is contemplated, diskectomy, laminectomy, and fusion are the most common surgical procedures utilized. Diskectomy, the most common surgical procedure for sciatica and back pain, may exacerbate the back pain, especially when there is concomitant spinal instability. Chronic back pain may therefore be a consequence following surgical diskectomy. Natural progression of the degenerative process also results in lumbar spondylosis, facet arthrosis, spinal stenosis, and spondylolisthesis in the time line of an aging spine, which may also be the source of pain generation. The costs of surgical procedures to correct these conditions vary widely, depending on the surgical procedures chosen and implemented by the surgeon. Fusion, the traditional procedure for back pain, is usually recommended with caution because of its surgical morbidity and high cost. Failed back surgery syndrome (FBSS), with a paucity of effective salvage procedures, then result when surgical treatment fails. One recent study by Katz ¹ estimated that the annual costs associated with all treatments of back pain in the United States are over $100 billion. This cost estimate does not even consider the difficult-to-calculate economic loss due to loss of productivity from disabling low back pain. Back surgeries to relieve back pain, however, continue to steadily increase in the United States, partly because of expansion of surgical techniques and implants used to facilitate fusion. Hazard² documented an increase in these numbers from 300,413 in 1994 to 392,948 in 2000. Though the majority of these surgeries are successful in relieving back pain, a significant percentage is not. Some studies estimate that, at best, only 60% of these surgeries are successful.^3,⁴ These data, along with the data reported in the Spine Outcomes Research Trial (SPORT),⁵ demonstrate that although most spine surgeries are cost-effective, even the 2-year results for degenerative spondylolisthesis, the premier indication for one-level fusion, is questioned. With good patient selection, accurate diagnostic criteria, and a low cost, a minimally invasive surgical option, addressing just the innervation of the facet-mediated pain generator, may be a viable minimally invasive procedure to be considered before the definitive surgical fusion or joint replacement option is considered.

The Yeung Endoscopic Spine Surgery (YESS) decompressive approach, described in Chapter 64, details a transforaminal endoscopic approach that utilizes a minimally invasive surgical technique enabling disc and foraminal decompression as well as ablation of painful nerves and removal of chemical mediators in the disc, annulus, and foramen. Presumed primary sensory nerves innervating the disc and facet can be ablated, and pathologic conditions causing inflammation (and, therefore, pain) are addressed. The technique, expanded to target denervation of the branches of the dorsal ramus responsible for facet mediated pain, is the subject of this chapter.

Lumbar spondylolysis, facet arthrosis, spondylolisthesis, both isthmic and degenerative, that may also be associated with spinal stenosis, are traditionally treated with open decompression, dynamic stabilization, or fusion. A recent article by Weinstein et al,⁵ examining the data from the SPORT trial, concluded that degenerative spondylolisthesis surgery (decompression and fusion) is not a cost-effective procedure when examined over a 2-year period. These data highlight the need to better evaluate back pain patients with more specific diagnostic procedures, such as evocative diskography, selective nerve root blocks, foraminal epidural steroids, and facet and medial branch blocks. The information obtained from these procedures in experienced hands allows the surgeon to more selectively choose who might benefit from surgical intervention. Many of the pain generators can also be addressed earlier in the disease process if surgery does not cause significant paradoxical effect on the aging spine. In this chapter we outline a technique for performing endoscopic medial, intermediate, and lateral branch rhizotomy arising from the dorsal ramus, a sensory branch from the origin of the main spinal nerve, that we have termed, dorsal endoscopic rhizotomy.

The endoscopic applications outlined in this chapter are therefore applicable to all painful conditions arising from the facet joint complex.

Indications and Contraindications

Endoscopic rhizotomy has been performed successfully, and remains effective at over 3-year follow-up in most patients in our pilot study. It is appropriate for the following conditions causing axial back pain.

Ideal Indications

Patients who will most likely benefit from selective endoscopic rhizotomy include the following:

1. Axial back pain solely from arthropathy of the lumbar facet joints without leg pain: The diagnostic imaging of these patients may present with narrowing disc space, but the discogenic contribution to back pain is thought to be a minor contributor. These patients are usually not debilitated, but the patients’ pain significantly affects their activities of daily living (Figure 65-1A-C).

2. Axial back pain mostly from facet arthrosis with very mild buttock and thigh pain: Pain is approximately 90% in the back and 10% in the leg.

3. Subacute and chronic axial back pain following a posttraumatic injury to the facet joints refractory to nonsurgical treatment.

4. Axial back pain from adjacent disc level of fusion demonstrating spondylosis and facet arthrosis causing pain without disc segment instability.

5. All of the previously mentioned patients should have more than 80% pain relief after controlled diagnostic and therapeutic medial branch block (MBB).

FIGURE 65-1a, 1b, 1c Ideal patient with single level facet arthrosis and chronic, non-debilitating axial back pain.

Relative Indications

Patients in the following categories should expect only partial relief of axial back pain from dorsal ramus rhizotomy:

1. Axial back pain associated with mild buttock pain and leg pain: In general, back pain is about 50% to 80% and leg pain is 20% to 50%, with pain coming from the facet as well as the disc.

2. Axial back pain from facet is 50% with leg pain 50% in general: Patients received previous benefit from medial branch block, plus transforaminal epidural block. The patient has a strong desire for relief of axial back pain more permanently with a minimally invasive procedure, while intermittent sciatica is tolerable.

3. Patient has axial back pain, 40% to 50%, and leg pain, 50% to 60%, with stenosis and instability indicated for surgical decompression and fusion, but the patient elects a less invasive staged procedure or whose medical condition does not allow for higher-risk surgical procedure. The patient would be satisfied to have a decreased pain level and partially improve the quality of life, in addition to reduced pain medication dose. These patients, indicated for fusion, should not have high expectation with dorsal endoscopic rhizotomy.

4. FBSS without pseudarthrosis and gross deformity presenting with axial back pain only and responding well to MBB.

5. Patient associated with mild and stable spondylolisthesis, but presenting with axial back pain of facet origin.

6. All of the previously mentioned categories of patients should have 50% to 80% pain relief after MBB before dorsal endoscopic rhizotomy. This group of patients should be very realistic about the anticipated pain relief.

Patients with Poor Indications for Dorsal Ramus Rhizotomy

Patients with lumbosacral radiculopathy whose debilitating leg pain is greater than back pain:

1. Multiple-level disc disease with confirmed severe concordant discogenic pain by evocative diskography, and minimal relief with medial branch blocks

2. Significant motion segment instability or hypermobility

3. Pseudarthrosis following failed fusion

4. FBSS with more leg pain than back pain without known etiology

5. Patients with multiple debilitating painful conditions: severe multilevel stenosis including foraminal stenosis associated with scoliosis without good response to MBB

6. SI joint dysfunction

7. Severe osteoporosis, particularly with vertebral compression fracture

8. Severe depression, fibromyalgia, rheumatoid arthritis, and ankylosing spondylitis as well as autoimmune diseases

9. Drug dependency

10. Psychosocial problems and pending litigation

11. No benefit from MBB

Patients initially benefiting from dorsal endoscopic rhizotomy, who have recrudescence of some of their back pain, may have pain from progression of vertical load forces shifting to the facets, such as progressive degenerative scoliosis. These patients will have relief for 2 to 3 years before the effect of rhizotomy fails. Spinal pain, however, may also come from multiple causes and multiple anatomic structures in the spine. Certain conditions such as anomalous nerves in the foramen may not be detectable using currently available technology, but may be visualized endoscopically. For a structure to be implicated, it needs to be shown to be a source of pain from reliable diagnostic techniques. Endoscopic examination of the foramen during foraminal surgery, discussed in Chapter 64 on foraminal surgery for painful conditions of the lumbar spine, identifies some of these nerve structures and anomalies. The known structures responsible for pain in the spine include, but are not limited to, the vertebral bodies, intervertebral discs, nerve roots, facet joints, ligaments, muscles, and sacroiliac joints. Postlaminectomy syndrome (FBSS) following operative procedures may affect these structures, and, except for recurrent disc herniation or lateral recess stenosis, may not be surgically correctable. Contraindications for facet rhizotomy are pain syndromes not involving the facet joint in some way. Neural blockade or nerve block therapy, however, is a validated procedure that, when performed properly, can implicate the facet joint as responsible for spinal pain in up to 40% of patients with low back pain.⁷ Patients with this condition usually have moderate to severe back pain that does not have a strong radicular component. Pain is aggravated by hyperextension of the spine, and may present with tenderness to palpation at the level of the suspected facet joint. Patient selection, therefore, depends more on the patient’s response to proper administration of medial branch blocks rather than facet injections, because the procedure targets the nerve innervating the facet joint. Although x-ray, CT scan, and MRI findings of degenerative disc disease, lumbar spondylosis, and facet arthrosis are helpful in concluding that the facet is involved in axial back pain, the success of surgical ablation of the branches of the dorsal ramus is dependent on clear interpretation and effective resolution of axial back pain from medial branch blocks. Adding low-dose steroids (methylprednisolone [Depo-Medrol]) to longer-acting anesthetic agents such as 0.5% bupivacaine provides long enough relief of axial back pain to help make a clinical decision on the projected effectiveness of endoscopic rhizotomy. Patient selection for the procedure for the prospective study begun in 2006 was indicated for patients receiving at least 50% back pain relief, but the pilot study demonstrated endoscopic rhizotomy is most successful for those reporting 80% to 90% relief of their axial back pain following a medial branch block. Contraindications are relative, since there may be limitations on the effects of nerve denervation. In patients with multiple or nonspecific pain generators such as myofascial pain syndrome, sacral iliac joint pain, or those with a soft tissue source of pain where no nerve root pathology exists, have less satisfactory results, even if there is a facet-component. Therefore, including these patients who also have facet-mediated pain may serve as relative contraindications. However, if the patient understands that the relief they get from facet rhizotomy is limited to the facet joint, then a satisfactory result can be obtained. The effect of facet denervation in the pain management literature cites pain relief lasting only 6 months to 1 year.^8,⁹ This is because current techniques of radiofrequency lesioning may not be complete. Dorsal endoscopic rhizotomy, however, was able to attain pain relief for this time frame more effectively, because the surgeon is able to confirm adequate ablation of a visualized nerve branch or the consistent location at least of the medial branch. Patients who fail to get relief from radiofrequency ablation have been shown to get significantly more relief following dorsal endoscopic rhizotomy. These patients may be offered dorsal endoscopic rhizotomy cautiously, because we assume that failure may be due to poor patient selection rather that technique failure. An ongoing continued review of A. Yeung’s 2006 prospective pilot study (presentation made at the International Society for Minimally Invasive spine surgery in January 2007. Information not published.) reveals a majority of patients still experiencing continued relief since the inception of the study (up to 3 years). Because of multiple pain sources in patients with an aging spine, results of endoscopic rhizotomy are less predictable in patients who were only partially relieved of back pain obtained from the diagnostic blocks. Each injection should be individually evaluated for clinical efficacy. In patients with only very temporary pain relief, another trial block may be considered. Patients unable to stop taking their anticoagulants for stroke, transient ischemic attacks, and thrombophlebitis are at greater risk for surgical morbidity. These patients are operated on with caution, risking complications from bleeding at the surgical site. However, the ability to cauterize a small wound to control bleeding may make the contraindication a relative one.

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