Fig. 32.1
Diagram capturing the progressive loss of stability due to acquired degenerative intervertebral dysfunction (ADIVD)
Stage 0: Minimal Dysfunction
This is the initial phase of elastic deformation due to the disk losing its viscoelastic properties. Lesions are only visible on histologic examination and only rarely manifest themselves as acute lumbar immobilization.
Stage I: Minor Dysfunction
This is the intermediate phase of elastic deformation with pure loss of stability, marked by lower back pain and brief episodes of posterior facet joint locking, which can occur at one or multiple levels and cause referred pain. This corresponds to Maigne’s notion of painful minor intervertebral dysfunction (PMID).
Stage II: Major Dysfunction
This corresponds to Kirkaldy-Willis’ stage of instability. This is the advanced stage of elastic deformation, with a dynamic, progressive loss of stability. Radiological and clinical signs of dynamic stenosis appear, leading to lumbar and sciatic symptoms due to changes in the spinal canal volume without anatomical modifications. Any disk protrusion, posterior facet osteoarthritis, or retrolisthesis can then alter the volume of the nerve root canal during the stage of static-dynamic stenosis and trigger neurogenic claudication symptoms. Next, the disks undergo plastic deformation because of water loss. This results in permanent lateral stenosis, made worse by the consequences of the loss of stability (osteophytes, abnormal movements).
In terms of functional signs, the only aspect that all authors agree on is the presence of mundane mechanical low back pain in combination with pseudoradicular pain, or Maigne’s referred pain; true radicular pain is rare.
There is no correlation between various clinical examination techniques and objective measurements. A comparative study of patients with suspected instability and patients in a control group was performed using a twist CT scan [3]. The findings disproved Graf’s hypothesis [4] that posterior facet separation was a pathognomonic sign of instability, since separation was also observed in patients who were asymptomatic. Pain in the posterior joint structures during trunk rotation or when striking the heel to the ground is only one of the many clinical signs of instability. The duration of pain relief after peri- or intra-articular lidocaine or corticosteroid injection is shorter in cases of facet pain due to instability than in cases of pain due to facet joint arthritis.
Stage III: Maximal Dysfunction
This corresponds to the final degenerative phase, characterized by structures that become wedged together and restabilize the spine, or the appearance of Junghanns degenerative spondylolisthesis or rotational dislocation, which causes degenerative lumbar scoliosis in adults.
The clinical symptoms including pain can either stem from the bone, adjacent spinous processes rubbing together (Baastrup’s disease), the posterior facet joints, or even be referred.
32.1.4 Need for Additional Examinations
The lack of specific symptoms, their multifactorial nature, and the lack of relationship between movement quantification and pain intensity make it challenging to understand the clinical picture of ADIVD. It also explains why the physician must turn to various types of additional tests [2]. Standard A/P and lateral and three fourth X-rays form the basis of the evaluation, along with dynamic views, which were first proposed by Nachemson in 1944. These were followed by many studies attempting to define segmental vertebral motion, quantify it, define standards, and as a consequence, get closer to the pathology using quantitative and hopefully reproducible data. Although these were all high-quality studies, there was no general agreement. However, White and Panjabi [5] were credited for showing that the vertebral unit had 6° of freedom. The twist CT scan is the only dynamic test with some evaluation potential, not necessarily by using true measurements, but by subjectively evaluating posterior facet joint separation in extreme positions of active rotation [3]. Magnetic resonance imaging (MRI) can reveal early signs of nucleus pulposus dehydration, which shows up as reduced T2 hypersignal. Modic underlines the lack of correlation between three levels of spinal cord signal intensity and degenerative disk disease and between clinical symptoms and anatomical disruptions [6, 7]. Pfirmann [8] subsequently proposed a treatment algorithm based on MRI classification of lumbar intervertebral disk degeneration.
32.2 Overview of Intradiskal Therapies
Conservative treatment encompasses several well-known nonsurgical and rehabilitation methods. Among the various intradiskal therapies currently being used to treat herniated lumbar disks and diskogenic lower back pain, we discuss the two we are most familiar with: radiofrequency (RF) ablation and nucleus pulposus implant.
32.2.1 Radiofrequency Intradiskal Techniques for Treating Herniated Lumbar Disks and Diskogenic Lower Back Pain
32.2.1.1 Introduction
Percutaneous intradiskal RF techniques are an integral part of the fairly complex treatment of low back pain or radicular diskogenic lumbar pain. These techniques came to the forefront when the chymopapain enzyme used for chemonucleolysis was discontinued. They were developed in parallel with nucleolysis techniques, which use chemical agents instead.
All RF techniques are performed through a minimally invasive transforaminal approach, the same approach used for a diskogram in Kambin’s triangle [9, 10] under the outgoing nerve root. A thin catheter is used to deliver a variable dose of thermal energy to a specific part of the lumbar disk; this catheter is connected to a preprogrammed external RF generator that can determine the disk impedance, among other variables. The catheter is removed at the end of the procedure. This procedure, which is carried out in an ambulatory care setting under local anesthesia or with neurosedative agents, must be performed in the appropriate aseptic environment with fluoroscopy. Prophylactic antibiotics during the procedure are recommended.
The exact mechanism of action is not well understood. It is based on the principles of decompressing the disk and/or destroying the disk’s peripheral neoinnervation and neovascularization, along with altering the disk’s collagen.
The clinical outcomes for these procedures are a function of patient selection and the technical requirements of the procedure, which are very specific. These techniques are aimed at relatively young patients who have failed a full course of conservative treatment and physical therapy, prior to discussing surgical disk stabilization. Even if only temporarily effective, these radiofrequency techniques can be used as patient selection criteria for disk arthroplasty or interbody fusion, as the success of intradiskal treatment confirms that the pain originates in the disk. If not effective, another surgical procedure can be performed without any additional problems.
32.2.1.2 History and Classification
In the mid-1970s, chemical nucleolysis was only performed with chymopapain. Since chymopapain was first introduced in 1963, its efficacy (70–80 % good and very good results) has been demonstrated in several randomized studies and compared with surgical treatment [11–13]. When the manufacture and sale of chymopapain were discontinued in 2001 for financial reasons, other percutaneous intradiskal therapies such as RF developed rapidly.
There are two main types of RF therapies:
Those that target the nucleus pulposus, such as disk decompression (e.g., Nucleoplasty® by ArthroCare)
Those that target the annulus fibrosis, such as annuloplasty with intradiskal electrothermal therapy (IDET) (e.g., SPINECATH and ACUTHERM from NeuroTherm)
Among these techniques, some are best suited to nerve root compression (Nucleoplasty, ACUTHERM) and others to isolated disk disease (SPINECATH).
32.2.1.3 Advantages
Generally, the risks associated with this procedure are considerably reduced because intradiskal RF ablation is performed through a percutaneous approach and the procedure is short (less than 20 min).
Local anesthesia or neurosedative agents are sufficient for these minimally painful procedures. This allows for continued oral communication with the patient about pain and neurological signs.
The spinal canal is not breached and there are no epidural scars. The posterior musculature is not touched.
The risk of sepsis is negligible.
Only a very small part of the disk structure is removed.
32.2.1.4 Common Mechanisms of Action
Percutaneous techniques are indicated in early degenerative disk disease, at a stage where the disk is still hydrated.
Diskogenic pain is provoked by excessive pressure on the disk, along with inflammation and hyperinnervation of annulus fibers within the fissures. Contained disk herniation within the annulus is only one of the degenerative stages.
Several mechanisms of actions have been proposed to explain the effectiveness of these procedures:
Denaturation of type I collagen (greater stiffness and dehydration)
Nuclear cavitation leading to reduction in nucleus volume and reintegration of annular fragments (disk nucleoplasty)
Destruction of annular fissures and destruction of peripheral inflammatory neovascularization and newly formed pain receptors (annuloplasty)
Disintegration of the herniated mass (annuloplasty)
32.2.1.5 Patient Selection and Results
RF ablation techniques are aimed at patients with diskogenic lower back pain, with or without small contained disk herniation, with or without compressive or referred radiculalgia. As with every treatment, the outcomes are a function of patient selection. The outcomes are also affected by the procedure quality, catheter placement, navigation within the disk, and the surgeon’s practices.
The minimum imaging assessment consists of weight-bearing and dynamic X-rays, MRI without contrast, and CT scan.
The indications are:
Diskogenic lower back pain and lumbar radicular pain due to contained disk herniation that has not responded to at least 6 months of well-conducted conservative treatment and physical therapy. Individual background variables such as the presence of secondary gains or social and professional conflicts must also be evaluated. Components of the diskogenic lower back pain diagnosis may include the outcome of the corset test and a negative result after facet joint block. Other diagnostic tools include the diskography results associated with provoked pain and evidence of posterior fissure. This evaluation is recommended before performing RF ablation to evaluate disk pressure (if the goal is to reduce it) or to eliminate the presence of non-contained disk herniation.
Involvement of one or two levels. The procedure is harder to perform at L5–S1 in men because the disk is embedded into the iliac crests.
MRI: type 0 Modic changes.
Disk height >70 % on weight-bearing X-rays.
The contraindications are suspicion of facet-related low back pain, extruded disk, spondylolisthesis or retrolisthesis, symptomatic lumbar stenosis, disk asymmetry, scoliosis, type I Modic changes (inflammatory changes in vertebral end plates), collapsed disk, and epidural leakage on diskogram (non-contained hernia).
32.2.1.6 Intradiskal RF Ablation Techniques
There are two types of techniques, aimed either at isolated disk degeneration or contained disk herniation.
Treatment of Isolated Disk Degeneration
The SPINECATH IDET [14] is an annuloplasty procedure where a bipolar RF catheter is inserted into the posterior or lateral section of the annulus (until the fissure is reached). Fluoroscopy is used to verify the catheter position (Fig. 32.2) and then thermal energy (40–60 °C) delivered over a 5-cm area for 16 in. Optimal placement of the catheter can be challenging, as the entire posterior annulus must be covered without breaching it (Fig. 32.3). Moderate resurgence of the diskogenic pain during the procedure is a sign of efficacy.
Fig. 32.2
Unrolled configuration of the SPINECATH IDET (NeuroTherm) on A/P (left) and lateral (right) fluoroscopy views
Fig. 32.3
Drawing of the optimal position of the SPINECATH catheter
Several nonrandomized studies have reported moderate improvements with 50 % pain reduction after 1 year [15–18]. Two randomized studies found good results versus placebo in terms of reduction in the Oswestry Disability Index (ODI) [19, 20].
Treatment of Contained Disk Herniation
Laser diskectomy was first introduced in 1986 [23]. This is not actually an RF technique, but one where the nucleus is vaporized using a laser diode. This procedure is aimed at treating lumbar radicular pain due to contained disk herniation. The needle or catheter is introduced in the center of the disk and then moved to the posterolateral side toward the suspected hernia. Intermittent bursts of energy are given up to a total dose of 1,200–1,600 J to vaporize part of the nucleus [23]. This technique is demanding and requires optimal placement of the powerful catheter. Secondary end plate inflammatory lesions have been described by Cvitanic in 30 % of cases [24], as well as a few cases of thermal discitis with flare-up of the low back pain.
Several studies have reported good results and pain reduction in about 70 % of cases [25–27]. This pain reduction occurs 6–8 weeks after the procedure. The best indication seems to be contained herniation or failed disk decompression using radiofrequency energy (nucleoplasty) for the same indications. However, the efficacy of this technique has yet to be truly demonstrated [28].
DISK nucleoplasty™ is a newer technique introduced by ArthroCare. This technique consists of RF catheter coblation (cold ablation) to induce nucleus cavitation (Fig. 32.4) and reduce intradiskal pressure. Less heat (40–70 °C) is produced than with a laser, thus the risk of end plate damage is lower. The indications are midline- or lateral-contained herniation in minimally degenerated disks. In an animal model, this treatment was shown to alter cytokines such as IL-1 and IL-8 [29]. Cohort studies have shown significant decrease in VAS pain and with good results in 70–80 % of cases [30–32].
Fig. 32.4
Drawing of catheter positioning used during disk decompression (Nucleoplasty® by ArthroCare)
The ACUTHERM IDET is an annuloplasty technique derived from the SPINECATH system (same RF generator) that uses a catheter to provide targeted disk decompression. A catheter heats the area of the disk-nerve root impingement, which alters the collagen and reduces the hernia by desiccation. This technique can be used with foraminal hernias (Fig. 32.5).
Fig. 32.5
Drawing of ACUTHERM™ decompression catheter (NeuroTherm) being used to treat a lateral disk herniation
Other Percutaneous Techniques
These other techniques revolve around chemonucleolysis (injection of a chemical agent) and percutaneous diskectomy (mechanical action), for example:
Nucleolysis with Hexatrione®, which has been abandoned because of the risk of disk calcification
Ozone chemonucleolysis
Absolute alcohol nucleolysis
Discogel® nucleolysis
Discogel® (jellified ethanol, manufactured by Gelscom in France) is an implantable device that is a promising treatment for contained disk herniation. It aims at improving water diffusion from the periphery to the center of the disk. The gel’s viscosity keeps the alcohol from leaking outside the disk. Results of a pilot study were encouraging [33]. A study funded by the PHRC in France is currently under way. We will soon be publishing the results of 35 patients that were treated with Discogel®.
32.2.1.7 Conclusion
Percutaneous intradiskal RF techniques are easy to perform in the hands of a trained surgeon. They are minimally invasive for disk and perivertebral structures and have a low complication rate, but require specific instrumentation and consumable products (RF generator and catheter).
Their main role resides in treating diskogenic lower back pain at an early, nonsurgical stage of the disease progression and as an alternative to traditional diskectomy surgery for treating disk herniation. However, the uptake of these techniques has been limited because of persistent questions about their efficacy, despite numerous publications.
32.2.2 Nucleus Pulposus Implant: Preliminary Results of a Memory-Coiling Spiral Implant
32.2.2.1 Introduction
The aftereffects of disk nucleus ablation have been evaluated clinically and biomechanically. During an in vitro study, Brinckmann [34] found progressive loss of disk height and increased radial disk bulging proportional to the mass of the excised nucleus tissue. This loss of disk height can lead to overload of the posterior facet joints and biological changes in the joint cartilage [35, 36]. These changes can cause painful spondylarthrosis and eventually require surgical treatment. After nucleus removal, kinematic studies have shown increased range of motion and clear displacement of the center of rotation in flexion/extension and lateral bending [37–39].
32.2.2.2 Design Specifications for a Memory-Coiling Spiral Nucleus Pulposus Implant
Our primary goal was to come up with an original method to replace only the nucleus pulposus through a minimally invasive procedure that would be an extension of the surgical diskectomy procedure used to treat disk herniation and to maintain the physiology of the mobile spinal segment and adjacent disks [40–44]. For this “memory-coiling spiral” implant, the memory effect is achieved through a specific manufacturing process where the base polycarbonate urethane elastomer (Sulene™ PCU, previously produced by Centerpulse, now Zimmer) is modified at the molecular level. When implanted in its unrolled state into the empty intradiskal cavity, the implant spontaneously regains its pre-formed spiral shape and completely fills the cavity without mechanical fixation (Fig. 32.6).
Epidemiology of Lumbar Degenerative Disk Disease
To Fuse or Not to Fuse: That’s the Question
Lessons from a Life: The Journey of Spinal Neurosurgery in the United States
Minimally Invasive Transforaminal Lumbar Interbody Fusion (TLIF): Indications and Techniques
Oblique Lumbar Interbody Fusion
Compensatory Mechanisms Contributing to the Maintenance of Sagittal Balance in Degenerative Diseases of the Lumbar Spine
Related posts:
Epidemiology of Lumbar Degenerative Disk Disease
To Fuse or Not to Fuse: That’s the Question
Lessons from a Life: The Journey of Spinal Neurosurgery in the United States
Minimally Invasive Transforaminal Lumbar Interbody Fusion (TLIF): Indications and Techniques
Oblique Lumbar Interbody Fusion
Compensatory Mechanisms Contributing to the Maintenance of Sagittal Balance in Degenerative Diseases of the Lumbar Spine
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