Interventional Spine Procedures: A Case-based Approach Alexander R Vaccaro, Jeremy Simon, Mitchell Freedman, Michael J Mehnert
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Basic Principles of Fluoroscopically-guided Procedures1

Jeremy Simon
 
INTRODUCTION
Interventional procedures in the treatment of pain have become a common practice. While the use of fluoroscopy can significantly reduce the risk of complications, some basic principles must be utilized to reduce the potential for harm. The practitioner should be well-educated and competent in anatomy, fluoroscopic anatomy and in needle-driving to safely deliver the treatment. It is recommended that a formal fellowship with an experienced clinician(s) be performed before using these procedures in clinical practice.
Ultimately these are elective procedures. The principle of Primum non nocere, “first do no harm” must be considered in patient selection. This applies to the patient's ability to stop anticoagulants, poor experiences with prior injections, glycemic control, and degree of neurologic impairment. The author will not perform cervical interlaminar epidural injections in patients with signs and symptoms of myelopathy, cord edema, or significant cord compression as demonstrated by the lack of cerebrospinal fluid around the cervical spinal cord on axial X-rays. This is for fear of placing pressure on a tenuous spinal cord and potential reversible or irreversible cord damage.1 While other practitioners may differ in their opinion on this matter, the concept of “do no harm” should always be considered when planning any interventional procedure.
 
STERILE PREPARATION
Thorough handwashing or scrubbing should be performed prior to gloving. Sterile gloves should be utilized and put on the hands without touching the outer portion with the ungloved fingers.
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A sterile field consists of a preparation of the skin with a povidone solution or chlorhexidine. Some studies showed superiority of chlorhexidine2–6 while others have shown no difference.7–11 The preparation should be made after locating the area with a spot film and making concentric circles from the target area outward. This reduces the chance of “inoculating” the target region with bacteria present on other areas of the skin. The area should be allowed to dry prior to skin puncture. A fenestrated sterile drape or sterile towels should be placed around the target area.
The use of sterile medications from an FDA-regulated (Food and Drug Administration regulated) pharmaceutical company is a must. Reports of fungal meningitis from presumed sterile medications have made it imperative to obtain medications from well-vetted companies.12–14 Medications should be drawn in a sterile fashion at the time of the procedure and placed in the sterile tray.
 
NEEDLE-DRIVING
The spinal needle has a notch at the top and a beveled tip. The inner portion, or cannula, is removable and gives added stiffness to the needle as well as helps to prevent tissue from entering the needle during placement. The tendency of the needle is to move in the direction of the slope of the bevel. Tissue will deflect against the bevel. This is the “opposite” direction as the notch. For example, if the notch is up, the tendency of the needle is to go down. If it is facing left, it will “tend” to go right.
The further the needle is into tissue, particularly stiffer tissues such as muscle, it will be more difficult to direct. Many practitioners will “accentuate the bevel” by placing a bend on the needle of about 10 degrees. This allows for larger movements to be made in deeper tissues.
Tuohy needles utilized in interlaminar approaches are of typically larger bore, often 18- or 20-gauge. They are thus more difficult to steer in tissue. The bevel and notch are in the same orientation, i.e. the needle will tend to move in the “same” direction as the notch.
 
FLUOROSCOPY
The use of fluoroscopy adds a significant advantage in procedural safety. The use of an anterior-posterior (AP) and lateral views allow the practitioner to determine the precise location of the needle before administering the treatment. The AP view lets the practitioner how close to the midline, or how “medial” the needle tip is placed. The lateral view shows the depth of the needle. This allows for subtle adjustments so that the needle can be placed accurately and without violation of the spinal canal.
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Care should be exercised by the interventionalist to minimize their exposure to radiation in the procedure suite. Radiation badges and rings should be worn and monitored to keep record of year-to-date and lifetime exposure. Lead aprons should be used to keep the soft-tissues, particularly the gonads and thyroid, covered. X-ray reducing goggles should also be worn to minimize eye exposure. X-ray reducing gloves may also be worn underneath the sterile gloves when possible.
Planning the procedure ahead of time by noting on plain films and magnetic resonance imaging (MRI)/computed tomography (CT) scan if there is transition anatomy (lumbarization of S1, sacralization of L5), hardware, osteophytes or obesity may also allow for reduced fluoroscopy times. A study in obese individuals showed a significantly longer fluoroscopy times in obese individuals.15
The use of pulsed, intermittent and half-dose fluoroscopy can reduce exposures, particularly at noncritical portions of the placement of the needle. Reducing the fluoroscopy time is also useful in so far as patient and procedure safety are not compromised.
The top of the C-arm is known as the image intensifier and the bottom is the source of the X-ray. Keeping farther away from the source when possible will reduce the interventionalist's exposure, as well as the “scatter” of the X-ray from the patient. The X-ray exposure will decrease as an “inverse square” of the distance from the source.16 Placing lead over the patient in areas outside of the field, when practical, may reduce scatter.17
Potential risks of radiation exposure include cataracts, radiation burns and various types of cancers.18 These risks are cumulative and monthly readings are essential for helping to alert the practitioner of their exposure.
 
Parallax
Maximizing safety, minimizing risk and improving accuracy are all part of advantages in the use of fluoroscopy in interventional spine procedures. Knowing how to position the patient and how to obtain ideal images in set-up helps also to expedite the procedure and reduce patient discomfort through reducing needle manipulation.
The top of the fluoroscopy unit, the image intensifier, can be thought of as the physician's eyes. The picture on the screen represents the X-ray image of the segment at that angle. If the needle is placed in line with the beam, it will appear as a dot with the hub of the needle visible (Fig. 1.1). “Following the beam”, or following this target trajectory, allows for minimal needle manipulation. The concept of aligning the needle with the X-ray beams is also known as “parallax”.
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zoom view
Fig. 1.1: Sacroiliac denervation. Note the needle over the right L5 dorsal ramus is seen in parallax, while the needles placed below are not
 
CONTRAST
Nonionic iodinated contrast allows the interventionalist to confirm that the medication is placed in the desired location. The use of extension tubing allows for the live injection of contrast while keeping the hands out of the field and reducing X-ray exposure. While aspiration of blood is a specific indicator of vascular placement, it is not sensitive.19,20
Patients with known allergy to iodine need to have proper medication prophylaxis and monitored during and after the procedure (see Chapter 15: Adverse Reactions to Medications). Attempts to minimize the amount of contrast injected should be made within reason.
 
ANTICOAGULANTS
Differing opinions exist regarding the cessation of anticoagulants during interventional spine procedures. Spinal injections in fully anticoagulated-patients are generally contraindicated.21,22 Clearance from the prescribing physician is essential, and the risks and benefits need to be weighed by both physicians prior to scheduling the procedure.
Nonsteroidal anti-inflammatory agents are generally accepted to be safe for most nonsurgical interventional spine procedures.23 A survey of interventional pain physicians showed that most held antithrombotics prior to procedures and fewer held nonsteroidal anti-inflammatory drugs (NSAIDs).24 While not a standard, below is the author's practice's anticoagulation protocol.
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Protocol for Holding Anticoagulants25–27
The following anticoagulant holding schedule is recommended prior to spinal procedures (clearance must be obtained from the prescribing physician first):
  • Ticlopidine (Ticlid): Hold for 14 days
  • Aspirin: Hold for 7 days
    • including: Alka-Seltzer, Anacin, Fiorinal, Ascriptin, Bayer, Bufferin, Lortab ASA, Darvon, Ecotrin, Excedrin, Percodan, Midol, Pepto-Bismol, Talwin
  • Clopidogrel (Plavix): Hold for 7 days
  • Dipyridamole (Aggrenox or Persantine): Hold for 7 days
  • Cilostazol (Pletal): Hold for 7 days
  • Pentoxifylline (Trental): Hold for 7 days
  • Agrylin (Anagrelide): Hold for 7 days
  • Prasugrel (Effient): Hold for 7 days
  • Ticagrelor (Brilinta): Hold for 7 days
  • Warfarin (Coumadin): Hold for 5 days
    • INR (drawn day before or day of procedure) should be below 1.3 to proceed with injection
  • Dabigratan (Pradaxa): Hold for 5 days
  • Rivaroxaban (Xarelto): Hold for 5 days
  • Apixaban (Eliquis): Hold for 5 days
  • NSAIDs: Hold for 5 days for cervical and thoracic procedures. Does not need to be held for lumbar and hip procedures
    • including: Diclofenac, Etodolac, Fenoprofen, Flurbiprofen, Ibuprofen, Indomethacin, Ketoprofen, Ketorolac, Meloxicam, Nabumetone, Naproxen, Oxaprozin, Piroxicam, Sulindac, Celebrex
  • Fondaparinux (Arixtra): Hold for 24–48 hours
  • Enoxaparin (Lovenox): Hold for 12 hours (prophylactic dose) or 24 hours (therapeutic dose)
  • Heparin: Hold for 4 hours.
Herbal drugs (specifically garlic, ginseng and gingko) seem to represent no added significant risk for the development of spinal hematoma in patients having epidural or spinal anesthesia.
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