Procedure and Technique for Transforaminal Injection

Dorn Spinal Therapy

Spine Healing Therapy

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A high-resolution C arm fluoroscopy is the preferred imaging device so that AP, oblique, and lateral imaging planes can be assessed while the needle is advanced.

Under fluoroscopy the patient is positioned in a supine position or a steep oblique lateral decubitus position, so that the cervical intervertebral canal and foramina are seen in multiple projections. The ideal position of the target canal is at the widest diameter with the fluoroscope angled slightly caudally along the axis of the canal to achieve this. After accurate count to the target canal and sterile skin preparation, a 25-gauge or 22-gauge short-beveled spinal needle is positioned, so that the target is the anterior cortex of the superior articular pillar adjacent to the middle of the posterior wall of the canal. In the latter instance, the needle position must be changed by withdrawal and reentry at a slightly different plane.

The needle is then introduced along the central ray in small increments and directed to the bone cortex of the mid-posterior canal. Because the exit zone of the canal is quite superficial and the length of the canal is short, frequent small-needle increments with interval fluoro-scopic screening are necessary before the needle reaches the bone. Fluoroscopy in the true AP position will determine the accurate depth of the needle, which can be then repositioned to see the needle position in the oblique and lateral view abutting the anterior cortex of the articular pillar posterior to the intervertebral canal (Fig. 12). Progressive entry of the needle into the canal is performed under AP fluoroscopic control, so that the tip does not pass beyond the

FIGURE 12 (A) Oblique projection and (B) anteroposterior (AP) projection. Selective C8 epidural nerve block. The target is the posterior cortical wall of the C7-T1 intervertebral foramen in the oblique projection. The needle tip should not project anterior to the articular pillar to avoid piercing the vertebral artery. The needle is then advanced under AP fluoroscopic guidance lateral to the pedicles and uncinate processes to avoid piercing the dura.

FIGURE 12 (A) Oblique projection and (B) anteroposterior (AP) projection. Selective C8 epidural nerve block. The target is the posterior cortical wall of the C7-T1 intervertebral foramen in the oblique projection. The needle tip should not project anterior to the articular pillar to avoid piercing the vertebral artery. The needle is then advanced under AP fluoroscopic guidance lateral to the pedicles and uncinate processes to avoid piercing the dura.

lateral aspect of the intervertebral canal. Induction of severe radicular pain or intense paresthesia indicates the needle must be repositioned before any injection is performed. Spot film or image capture in true AP, oblique and lateral projections should document the position of the needle tip before the injection of contrast. To prevent needle movement, a short-length of minimal volume extension tubing is attached to the needle hub. Syringe aspiration will infrequently demonstrate blood or cerebraspinal fluid because of the small needle size. Therefore injection of 1.0 to 1.5 cc of contrast in a 3.0 cc syringe should be performed under real-time fluoroscopy with digital subtraction angiographic imaging in the antero-posterior plane to exclude inadvertent intra-arterial radicular arterial filling into the spinal canal (36). The contrast will typically outline the spinal nerve and flow into the adjacent epidural space (Fig. 13). Contrast may also follow the anterior spinal ramus distally. Rapid upward clearance indicates vertebral artery filling, and the needle must be repositioned without further injection. Venous filling of the radicular, epidural, and paraspinous veins leads to a slow washout of contrast usually directed caudally. Rotation of the needle and withdrawl to reposition the needle tip should be followed by a repeat digital subtraction angiogram to exclude intravascular filling. The procedure should be aborted with contrast opacification of a radicular artery. Injection of a small volume of lidocaine 2% (0.5-1.0 ml) requires observation of the non sedated patients for adverse neurological effect for several minutes and serves as a diagnostic block.

The dural sleeve extends along the nerve roots to the entrance zone of the foramen. A rapid dilution of contrast usually indicates that the needle tip has punctured the dura and is within the subarachnoid space. Withdrawal of the needle is then performed without further injection and consideration should also be given to abandoning the procedure and rescheduling it.

Bupivacaine and longer-acting anesthetics should be avoided because of the possibility of an unintended subarachnoid injection and possible respiratory arrest. Corticosteroids are given for therapeutic purposes in doses of 3.0 to 6.0 mg of betamethasone or 20 to 40 mg of triamcinolone for a single level. Dreyfuss et al. have demonstrated comparatively similar effectiveness of nonparticulate and particulate steriod preparations. They employed 12.5 mg dexamethasone sodium phosphate and found similar therapeutic responses to an injectate of 60 mg of triamcin-olone (37).

CT scan or fluoroscopic CT-guided cervical transforaminal blocks have been advocated by some authors (38), and are useful in large or obese patients, especially at the lower levels (C6-C7; C7-T1), which may be partially obscured by the shoulders or if there is marked bone

FIGURE 13 Anteroposterior view. Selective C8 epidural nerve block. A 22-gauge needle tip within the midportion of the C7-T1 intervertebral foramen. Contrast outlines the C8 spinal nerve within the canal and the adjacent medial epidural space.

hypertrophy or bone spurs from the adjacent zyagapophyseal joint. The principle of targeting the posterior wall cortex and the use of nonionic contrast to exclude intravascular injection must still be adhered to (Fig. 14A and B). The alignment of the carotid vessels and the vertebral artery to the foramen will be variable and may be in the path of the needle (Fig. 14C and D), particularly at C4-C5 and C5-C6. The use of a 25-gauge spinal needle decreases the risk of intravascular damage.

A diagnostic block with local anesthesia is achieved by injecting a small volume (0.5-1.5 cc) of preservative-free (single dose) lidocaine 1% into the perineural epidural space. Marcaine and longer-acting anesthetics should be avoided because of the possibility of an unintended subarach-noid injection and possible respiratory arrest. Corticosteroids are given for therapeutic purposes in doses of 3.0 to 6.0 mg of betamethasone or 20 to 40 mg of triamcinolone for a single level.

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