Spinal Cord and Dorsal Root Ganglion Stimulation
Products available:
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Boston Scientific: Spectra Wavewriter
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Abbott: The Proclaim Elite, (recharge free system)
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Nevro: HF-10
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Medtronic
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Stimwave
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Nalu.
Spinal Cord Stimulation
Spinal cord stimulation is based on the gate control theory, an idea put forth by Patrick Wall and Ronald Melzack in 1965, stating that “control of pain may be achieved by selectively activating the large, rapidly conducting fibers.” Two years later, the first dorsal column stimulation, conducted by Dr. Norman Shealy, occurred. Based on these early studies, spinal cord stimulator (SCS) therapy succeeded by applying electric fields to membranes, altering their electric potentials and leading to either the activation or inhibition of the neuron. SCS can increase the concentration of inhibitory neurotransmitters and inhibit the nociceptive sensorimotor reflex, a polysynaptic spinal reflex intrinsic to pain sensation. It is most successful for patients with pain due to failed back surgery syndrome, complex regional pain syndrome (CRPS) types I and II, and intractable neuropathic pain. In current times, about 50,000 SCSs are implanted every year.
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Traditional spinal cord stimulation (40 to 60 Hz)—provides repetitive electrical stimulation, which is interpreted by the brain as a paresthesia sensation over the painful body part. The SCS lead is located in the midline dorsal epidural space.
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High-frequency stimulation (10k Hz)—involves stimulation with increased frequency rate, which results in targeting different neuronal targets and subthreshold perception (able to have stimulation without paresthesia). High-frequency SCS leads are located in the midline epidural space.
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Burst stimulation (5 pulses 500HZ 40 times per second) —altered waveform pattern of stimulation that mimics organic nerve firing. This pattern of stimulation results in subthreshold perception and improved pain control compared to traditional stimulation.
Many studies have indicated that SCS is a safe, successful treatment for a variety of chronic pain syndromes. In 2005, North et al. conducted the first randomized, controlled trial comparing 60 participants with failed back surgery syndrome who underwent either SCS or repeat lumbar spine surgery. Significantly more individuals in the SCS group endorsed pain relief. When compared to conservative managements, SCS patients experienced greater reductions in leg pain, as well as an increase in quality of life. In a similar study, Kemler et al. found that SCS was superior to physical therapy for patients with CRPS. The vast collection of studies investigating the efficacy of SCS is constantly increasing, although most indicate that it is an effective, minimally invasive therapy for patients with neuropathic pain conditions.
The SENZA-RCT trial, a multicenter, randomized, controlled trial evaluating the safety and efficacy of 10-kHz high-frequency (HF10) therapy for the management of chronic back and leg pain, represented a major change in the traditional SCS treatment algorithm. The NEVRO system delivered electrical stimulation pulses at high frequency (10,000 Hz) as compared with traditional low-frequency SCS systems (typically around 50 Hz). Significant pain relief was seen in both low back and lower extremity pain without inducing paresthesia.
New SCS programming sequences targeting microglia and astrocytes (Medtronic DTM) are emerging as another potential stimulation technology for targeting pain signaling in the central nervous system. Microglia and astrocytes within the central nervous system (CNS) have been shown to play a significant role in the development and maintenance of neuropathic pain. Following peripheral nociceptive activation (via nerve injury, infection, or inflammation), microglia become activated and release pro-inflammatory cytokines such as TNF-a, IL-1b, and IL-6, thereby initiating the pain process. Microglia propagate the neuroinflammation by recruiting other microglia and eventually activating nearby astrocytes, which prolongs the inflammatory state and leads to chronic neuropathic pain.
SCS does not eliminate or mechanically alter the source of pain but, instead, blocks the transmission of pain signals in the dorsal columns so that the patient perceives less painful stimuli. The device is programmed to provide each patient with settings that are best suited to their condition. Before a permanent stimulation system is implanted, patients undergo a trial of spinal cord stimulation (typically 5 to 7 days) with temporary lead insertion to determine if the amount of relief they receive is meaningful enough to implant a permanent system. The amount of relief provided varies from person to person and, if the trial stimulator is unsuccessful, it can easily be removed and the patient can pursue other forms of treatment.
Common Pathology
Current FDA approval is targeted for patients with various pain syndromes due to failed back surgery syndrome/post-laminectomy syndrome, CRPS types I and II, intractable neuropathic pain, visceral abdominal pain, and intractable angina pectoris. Success has been reported for off-label use for the treatment of vascular, abdominal, and pelvic pain.
Dorsal Root Ganglion Stimulation
Products available:
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Abbott: Proclaim dorsal root ganglion (DRG)
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Stimwave
Similar to normal SCS, dorsal root ganglion (DRG) stimulation is based on the gate control theory, an idea put forth by Patrick Wall and Ronald Melzack in 1965 stating that “control of pain may be achieved by selectively activating the large, rapidly conducting fibers.” Typical SCS has multiple shortcomings, such as inability to target specific dermatomes and vulnerability to position changes. DRG stimulation, on the other hand, can directly stimulate affected nerve roots. DRG stimulation is based on targeting a different part of the spinal cord, specifically the DRG. The application of DRG SCS results in specific stimulation/pain relief that is extremely focused in a dermatomal pattern that mimics its spinal nerve level. The SCS lead is lateral and exits neural foramen (currently limited to lower thoracic and lumbar levels).
To determine the efficacy of DRG, Timothy et al. performed a randomized trial, comparing DRG and SCS stimulation in patients with CRPS. This study found that 81.2% of patients that underwent DRG were relieved of their pain at 3 months, compared to 55.7% of those who underwent traditional SCS. This finding was consistent at 12 months. Similar studies had conclusions consistent with the study by Timothy et al., finding that DRG stimulation provides sustained relief in patients with focal neuropathic pain.
Common Pathology
Similar to SCS, patients can receive DRG stimulators, which are devices that interfere with pain signaling from the DRG, an easy-to-reach structure in the spine that contains a large amount of sensory nerves. This device is used to treat pain signaling from areas that are difficult to treat through SCS, such as within the hands, groin, knee, chest, or abdomen. This method does not eliminate the source of pain but, instead, blocks the sensation so that the patient feels less of it. The device is programmed to provide each patient with settings that are best suited to their condition. In addition, patients are given a remote that they can use to control their DRG stimulator, allowing them to further personalize their settings and receive the most relief possible. Before a permanent stimulator device is placed in the body, patients can trial an external version. The amount of relief provided varies from person to person and, if the trial stimulator is unsuccessful, it can easily be removed and the patient can pursue other forms of treatment.
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Mononeuritis of Lower Extremity Unspecified (G57.90)
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Other Nerve Root and Plexus Disorder (G54.8)
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Mononeuritis of Lower Extremity RIGHT (G57.91)
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Mononeuritis of Lower Extremity LEFT (G57.92)
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Failed Back Surgery Syndrome (M96.1)
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Off label use: Abdominal pain and vascular claudication
Pertinent Anatomy
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Traditional spinal cord stimulation is performed via the interlaminar approach with resulting lead placement in the epidural space.
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Vertebral body, pedicles, and dorsal epidural space
Equipment
SCS kit, per manufacturer, varies
Patient Position
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Prone with pillow under abdomen to reduce lumbar lordosis
Clinician Position
Standing on the side of patient
C Arm Position
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AP and lateral views are necessary to track lead advancement and final position.
Needle Position
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Needle starting point typically is placed 1.5 to 2 vertebral levels below intended level to be accessed.
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Reason for the difference in needle origin to needle target is to keep needle tip/SCS lead located in the dorsal aspect of the epidural space.
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The interlaminar approach/access is safely done utilizing a loss of resistance syringe to identify safe entry into the epidural space.
Target
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Traditional/Burst/High frequency stimulation—needle tip final position midline in dorsal aspect of epidural space. SCS lead midline space between T7 to T9.
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DRG stimulation—needle tip slightly contralateral to midline of desired exiting foramen. Needle tip one level inferior to exiting foramen.
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Besides traditional radicular symptoms, spinal cord stimulation can be useful. DRG/SCS has superior pain relief of distal extremity. However, reports of injury to DRG or exiting nerve root have been reported. So, caution while placing the DRG lead is imperative ( Figs. 35.1 and 35.2 ).
Fig. 35.1
Right dorsal root ganglion stimulation lead placement at L4-5 and L5-S1 on an anteroposterior fluoroscopy image.
Fig. 35.2
(A and B) Thoracic sacral insufficiency fracture lead placement at T9 on anteroposterior and lateral fluoroscopy images.
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SCS trial is the most important predictor of potential success. Trials vary from 3 to 7 days. SCS trials involve evaluating the patient’s degree of pain relief.
Spine Fracture Therapies
Products available
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Medtronic:
Kyphon Balloon Kyphoplasty, Vertebroplasty, Sacroplasty for vertebral column and sacral fracture repair
Stryker: AVAflex Ballon Kyphoplasty, iVAS Balloon Kyphoplasty for vertebral augmentation and sacroplasty. Spine Jack novel system that includes implantation of a fixation expandable system at spine fracture level. Indicated for vertebral fracture expansion, fixation, stabilization, and ultimately reduction and stabilization of same level.
Vertebral compression fractures affect 26% of women over the age of 50 and 40% of women over 80 years of age. Of these individuals, more than one-third develop chronic back pain. Typically, individuals with vertebral compression fractures are treated conservatively with analgesics, bed rest, external fixation, and/or rehabilitation. However, the most frequently prescribed medications are poorly tolerated by elderly patients, and bed rest can further demineralize the vertebrae, making these patients more susceptible to additional fractures. Furthermore, surgical fixation is often unsuccessful due to weakness within the osteoporotic bone. Therefore, physicians have explored other treatment options for patients with vertebral compression fractures.
Vertebroplasty is a minimally invasive procedure in which acrylic bone cement is injected into a pathologically compressed vertebral body. Studies have shown short- and long-term pain relief in 70% to 95% of patients. Kyphoplasty is similar in concept to percutaneous vertebroplasty, except that an inflatable balloon is used to expand a collapsed vertebral body as close as possible to its natural height before introducing the mechanical fixation by injecting polymethylmethacrylate (PMMA), a cement-like material, into the cavity created by the balloon. In theory, the expansion of a cavity by the balloon permits infusion of bone cement into the cavity under lower pressure than the bone cement injected during vertebroplasty. Doing so can stabilize the compression fracture while realigning the endplate of the vertebral body. Stabilization of the bone limits movement within the fracture, thereby relieving symptoms of pain. One of the primary reasons for choosing kyphoplasty in lieu of vertebroplasty is decreased cement leakage, which is a main complication with resulting compression of exiting spinal nerve roots or central spinal cord compression. A 2017 review article consisting of 22 studies reported 54.7% and 18.4% cement leakage for vertebroplasty and kyphoplasty, respectively. Additionally, a review published in 2018 of 16 studies showed that kyphoplasty had significantly less risk of cement leakage versus vertebroplasty compared to vertebroplasty. There were no significant differences in pain and functional scores.
Sacroplasty
First described in the literature in 1982, sacral insufficiency fractures (SIFs) affect 1% to 5% of patients in at-risk populations. This condition most commonly affects elderly women with osteoporosis, as well as those with pelvic radiation, steroid-induced osteopenia, rheumatoid arthritis, multiple myeloma, Paget disease, renal osteodystrophy, and hyperparathyroidism. SIFs are thought to occur when stress is applied to sacral bones with insufficiency, with pain symptoms resulting from micromotion within the fracture site. However, there is often a delay in diagnosing individuals with SIFs due to the vagueness of symptoms and similarities to other diseases that frequently affect elderly populations. Once diagnosed, patients are typically treated conservatively with analgesics, bed rest, external fixation, and/or rehabilitation. However, the most frequently prescribed medications are poorly tolerated by elderly patients and bed rest can further demineralize the vertebrae, making these patients more susceptible to additional fractures. Therefore, physicians have explored other treatment options for patients with SIFs.
The injection of cement into the sacrum was initially used to treat painful bony metastases, expanding to SIFs in 2002. During this procedure, PMMA cement is injected into the fractured sacrum with the assistance of imaging devices. This stabilizes the fracture, minimizing micromotion and relieving pain. The goal is to alleviate symptoms while increasing mobility, limiting the need for narcotics and bed rest. A study conducted by Lyders et al. looked at the efficacy of sacroplasty.
By analyzing 52 patients that underwent sacroplasties, the authors concluded that this procedure is safe and effective, providing rapid relief of pain in individuals with SIFs. Participants endorsed a 50% reduction in pain at 2 days, 80% reduction at 2 weeks, and 90% reduction at 1 year. Furthermore, patients relied less on narcotic medications and endorsed improved ability to complete activities of daily living (ADLs) following the procedure. A notable complication is the unexpected extrusion of PMMA cement outside of the sacrum, resulting in neurologic sequelae, although this is rare. This study did not include a control group and, therefore, it should ideally be repeated with a randomized controlled trial design. However, the results are promising, indicating that sacroplasty is an effective treatment for SIFs.
Similar to a balloon kyphoplasty, this procedure is intended to reduce pain while increasing stability for patients with the use of a biological cement. During this procedure, bone needles are inserted into the affected area with the assistance of fluoroscopy. Once in the correct position, bone cement is inserted through the needles, hardening along the fracture. Pain reduction is almost immediate, with some patients endorsing alleviation of symptoms only 30 minutes after treatment.
Pertinent Anatomy
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The vertebral body is comprised of anterior and posterior elements with the connecting element being the pedicle.
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The pedicle is both the entryway and safe zone for the procedure being done (see Fig. 13.2 ).
Common Pathology
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Compression fracture (with resulting pain) can occur from multiple causes (osteoporotic compression fractures, multiple myeloma, spinal tumors, hemangioma, myeloma, metastasis, and lymphoma)
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Most compression fractures occur between T9 and L4
Equipment
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Vertebral augmentation kit, per manufacturer, varies
Common Injectates
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Local anesthetics: Lidocaine 0.5%, Lidocaine 2%, Bupivacaine 0.25%
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PMMA powder/barium sulfate/tobramycin powder
Injectate Volume
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6 to 10 mL is typical for local anesthetic injectate
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PMMA or Cortoss cement (injectate averages 2 to 3 mL per level)
Lumbar Spine
Patient Position
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Prone with abdomen on a pillow to reduce lumbar lordosis
C-Arm Position
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Appropriate vertebral body level is confirmed in the anteroposterior (AP) view by identifying the 12th rib and counting from there.
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Proceduralist will advance the needle biplanar in AP and lateral views.
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Appropriate planning for trajectory and end point being posterior 1⁄3 of vertebral body.
Needle Position
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Plan for trajectory by localization of local anesthetic needle under fluoroscopy at superior lateral aspect of the pedicle (respective 10 and 2 o’clock positions).
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Needle/trocar is advanced using both AP and lateral views to identify needle tip within the pedicle (NOT violating the medial pedicle body) until it passes the posterior vertebral body wall.
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Transpedicular is most common route due to its inherent safety. Prevents neural compression via cement extravasation. Guide trocar to the 10 o’clock (left side) or 2 o’clock (right side) entry to prevent medial border violation.
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Trocar needle is advanced using mallet and intermittent fluoroscopy imaging to clarify tip staying within the pedicle as it advanced
Target
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Central anterior 1⁄3 of vertebral body.
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Recommend monitored anesthesia care (MAC)
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If possible, perform a transpedicular approach, with focus on not violating medial border.
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Using blend of contrast/bone cement injected slowly to identify any extravasation into perineural structures.
Thoracic Spine
Patient Position
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Prone
C-Arm Position
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Oblique AP view with ipsilateral pedicle 25% medial to lateral edge of the vertebral body
Needle Position
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Extrapedicular approach/intercostotransverse (thoracic)—avoids pleural and parenchymal injury. Trocar passes lateral to the transverse process and medial to the rib border. Traditional transpedicular approach is limited due to narrower pedicles and difficulty with central vertebral body endpoint.
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Parapedicular—approach to obtain more central endpoint orientation, increased risk of damage to other anatomical structures.
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Can be done with two-needle or one-needle technique, depending on need and vertebral body level.
Target
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Desired target is anterior (1/3) vertebral body, preferred contralateral vertebral body to facilitate unipedicular approach/treatment
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Most fractures above T2 are not operated on in an office-based setting.
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Recommend 11-gauge needle (reports of pedicle fracture with smaller 13-gauge needle, most likely secondary to challenges with needle positioning with smaller needle)
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Cement leak is the most common complication—avoided based on needle position in anterior (1/3) of vertebrae and intermittent radiographic imaging to clarify cement extravasation ( Fig. 35.3 ).
Fig. 35.3
(A to C) Thoracic kyphoplasty images using fluoroscopy. (A) in anteroposterior (AP) at T11 on the right and T12 on the left. (B) Lateral image of T11 and T12 with needle placement. (C) AP image with cement in T11 and T12 after needle removal.
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Second most common complication is infection—adherence to strict sterile technique with optional use of antibiotic (both intravenously and via PMMA mixture) to help decrease the risk
Cervical Spine
NOTE: This is usually not performed in office-based setting, and rarely by non-orthopedic surgeons or neurosurgeon
Patient Position
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Supine position, neck extended with towel or bolster under shoulders
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Larynx and trachea displace medially, carotid artery laterally
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Needle entry adjacent to medial border of right sternocleidomastoid muscle under direct image guidance (specifically ultrasound to assess presence of vascular structures)
C-Arm Position
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Biplanar technique with straight AP and lateral views, with neck in neutral position and cervical extension
Needle Position
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Anterolateral (cervical spine)—anterior approach into the vertebral body, avoiding blood vessels, trachea, esophagus, and neural structures. Additional ultrasonography imaging is optimal to identify a safe trocar path.
Target
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Central anterior (1/3) vertebral body.
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High risk procedure given the concentrated anatomy with vascular and neurologic structures in proximity.
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Cement leakage can occur between 12% to 84% of treated vertebrae, but many of those are asymptomatic.
Minimally Invasive Lumbar Decompression
Minimally Invasive Lumbar Decompression Procedure
Minimally invasive lumbar decompression (MILD) is a procedure to treat lumbar spinal stenosis (LSS) in part due to ligament flavum hypertrophy. Pain that is present in the axial spine with radicular symptoms (indicative of neurogenic claudication) is most likely to respond. Finding the greatest stenotic level on magnetic resonance imaging (MRI) with ligamentum flavum thickening (noting that both level and laterality are a must to determine targeted areas). It is an outpatient procedure performed under monitored anesthesia (i.e., MAC). It treats lumbar decompression by using a 5.1 mm gauge trocar with associated tools to remove a hypertrophied ligamentum flavum and small portions of the lamina, causing lumbar spina stenosis (LSS).
To evaluate the efficacy of MILD, scientists have compared this procedure to other common treatments for LSS, such as epidural steroid injections (ESI). In a randomized controlled study performed by Peter et al., treatment outcomes for patients with LSS and neurogenic claudication symptoms were compiled from 26 interventional pain management centers. In total, 149 MILD patients were compared to 131 patients that were treated with ESIs. They found that MILD procedures provided sustained relief, with patients endorsing significant improvements in their pain, symptoms, and physical functionality levels for up to 2 years following treatment. In addition, there were no procedure-related adverse events or spinal instability for those that underwent MILD procedures. Individuals that received ESIs also endorsed alleviation of their symptoms, however, the effects were not as durable and many required repeat injections to sustain their pain relief. When compared to other spinal procedures, MILD patients are less likely to require surgical reoperation; in this study, 5.6% of MILD patients required a repeat operation at 2 years, compared to the national average of 12.5% to 16.9% for individuals that received spinal fusions and 14.4% to 26.0% for individuals that underwent interspinous process distraction. This study and similar experiments indicate the MILD is successful in alleviating symptoms of LSS, providing more durable results than ESIs and other spinal operations. MILD procedure training requires attendance at a specific hands-on training course provided by the company, thus only a general explanation is presented here.
Common Pathology
LSS often leads to neurogenic claudication, which causes extremity and lower back pain that can significantly reduce an individual’s quality of life. Approximately 19.4% of individuals between the ages of 60 and 69 experience LSS, making spinal surgeries common procedures within this population. Usually, this condition affects both sides of the body, although symptoms can be asymmetric, with one side experiencing worse effects. About 43% of individuals with LSS experience numbness, often exacerbated by prolonged periods of standing and walking. LSS is often accompanied by bulging discs, foraminal narrowing, facet hypertrophy, facet arthropathy, and degenerative disc disease. To treat this condition, many physicians offer MILD procedures, where excess bones and ligaments are removed to minimize stress on spinal nerves.
Pertinent Anatomy
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The proceduralist needs to understand and visualize on fluoroscopy the spinous processes, lamina, ligamentum flavum, and pedicles.
Common Pathology
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MILD is indicated for a thickened ligamentum flavum (2.5 mm or greater), which causes narrowing of the spinal canal.
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It is typically accompanied by neurogenic claudication, resulting in pain and numbness of the lower back, legs, and buttocks.
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It is interesting to note that other conditions may find benefit in pain relief and function due to increased canal space. Some of these conditions include bulging disc, facet hypertrophy, and foraminal narrowing.
Equipment
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C-arm fluoroscopy
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Trocar
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One sculptor/rongeur
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Tissue sculptor
Common Injectates
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Contrast for epidurogram
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Local anesthetic, with or without, corticosteroids is optional.
Injectate Volume
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2 to 5 mL of contrast
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2 to 5 mL of injectate
Patient Position
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Prone with abdomen on a pillow to reduce lumbar lordosis
Clinician position
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Side of patient
Fluoroscopy Position
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Posterior-anterior, lateral, and contralateral oblique view (for epidurogram)
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The fluoroscopy machine is rotated to obtain a contralateral view as the optimal working view
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Tissue removal is conducted under live fluoroscopy
Needle Position
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Epidurogram by translaminar Tuohy needle ( Fig. 35.4A and B).
Fig. 35.4
(A) Epidurogram anteroposterior view. (B) Contralateral oblique view.
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Trocar will be placed just lateral to the spinous process at the lamina ( Fig. 35.5A and B).
