Needle Introduction and Placement

The original choice of a device for percutaneous cement introduction was based on device availability. The size of these devices was empirically chosen to allow the viscous PMMA cement to be injected. Originally 10- to 11-gauge trocar-cannula systems were used. It is becoming progressively common to see smaller gauge (13-15) needles used routinely. All will work with the least resistance during injection found with the larger bore, while the smaller needles are useful in small pedicles or in the cervical spine. From the thoracic through lumbar spine, a 13-gauge cannula can be placed through the adult pedicle without fear of its being too large.

Several introductory routes for needle delivery are possible, including (1) transpedicular, (2) parapedicular (transcostovertebral), (3) pos-terolateral (lumbar only), and (4) anterolateral (cervical only). The classic route for most PV is transpedicular. It offers the following advantages.

1. It usually provides the operating physician with a definite anatomical landmark for needle targeting (Figure 14.9).

2. It is very effective for PV and for biopsy of lesions inside the vertebral body.

3. It is inherently safe and does not carry the risk of needle damage to other adjacent anatomical structures (nerve root, lung, etc.) as long as an intrapedicular location is maintained.

In the upper thoracic region and in small patients, the pedicle may be too narrow for an 11-gauge needle. In this situation, a 13-gauge needle should be used.

The parapedicular or transcostovertebral approach (Figure 14.10) was devised to allow access when the transpedicular route is not desirable (e.g., small pedicle). Since the needle passes along the lateral aspect of

Transpedicular Versus Extrapedicular

Figure 14.9. (A) Typical transpedicular route for needle placement into the vertebral body. (B) Anterior-posterior radiograph demonstrates the placement of the needle through the pedicle, which is seen as a well-circumscribed oval (arrow). In this projection, the needle is initially positioned during fluo-roscopy while being held with a clamp (arrowhead) to avoid x-ray exposure to the operator's hands. (C) Lateral fluoroscopic image demonstrates the final needle position beyond the midline of the vertebra.

b 260

c the pedicle, rather than through it, a small pedicle does not preclude using an 11-gauge needle for cement introduction. Also, this approach angles the needle tip more toward the center of the vertebral body than does the transpedicular approach. At least in theory, this angle may allow easier filling of the vertebra with a single injection. There is a higher chance of pneumothorax with a parapedicular approach than with the transpedicular route. A second potential problem with the parapedicu-lar route is that the needle enters the body only through its lateral wall. This approach may increase the risk of paraspinous hematoma after needle removal. Because with a parapedicular approach the osteotomy site occurs laterally along the side of the vertebra, one cannot apply local pressure after needle removal as can be done with the transpedicular route.

In the cervical spine, a transpedicular route is very difficult, so an anterolateral approach may be used as an alternative. Needle introduction must avoid the carotid-jugular complex. To accomplish this goal, the operating physician (as in cervical discography) can manually push the carotid out of the path of the needle. Alternatively, CT can be used to visualize the carotid, and a trajectory that will miss the vascular structures can then be chosen. A small guide needle can be inserted to ensure accurate placement outside the carotid complex. I prefer the guide needle alternative because it gives positive guidance and confirmation without excessive fluoroscopy to my hands during needle introduction. However, because osteoporotic fractures in this area are rare, the cervical spine only occasionally undergoes PV. Neoplastic disease may produce an occasional need for PV intervention in the cervical spine.

Once the needle route is chosen, local anesthesia is administered, and a small dermatotomy incision is made with a no. 11 scalpel blade. The trocar-cannula system is introduced through the skin incision and subcutaneous tissue to the periosteum of the bone. This introduction can be facilitated with a sterile clamp to guide the needle during flu-oroscopy, thus avoiding radiation to the operating physician's hands (Figure 14.9B). In osteoporotic bone, penetrating the bone cortex and advancing the needle into the body is usually very easy. In a patient with neoplastic disease, the bone may still be very dense and strong (except where it has been destroyed by a tumor). The use of a mallet to advance the needle through very dense bone is a technique clearly superior to manual advancement. Regardless of whether a transpedic-ular or parapedicular route has been chosen, the tip of the needle should lie beyond the vertebral midpoint as viewed from the lateral projection. I usually try to obtain an even more anterior position by placing the needle tip at the junction of the anterior and middle thirds.

Two needles are routinely placed, usually via the transpedicular approach. This takes minimally longer than a single needle placement and affords a large margin of safety for being able to dependably complete a vertebral fill with a single mix of cement. There is no question that a single needle placement can give an adequate fill in a large number of cases. However, the single-needle method fails to produce uniform fills more often than the double-needle technique and may oblige the operator to accept a larger cement leak during filling (if the second needle is not in place as an alternate injection route).

Extrapedicular

Figure 14.10. (A) Needle location for parapedicular (extrapedicular) placement. (B) Lateral projection demonstrating that the needle must enter above the transverse process on the parapedicular approach.

Spine Transverse Process Needle

Figure 14.10. (A) Needle location for parapedicular (extrapedicular) placement. (B) Lateral projection demonstrating that the needle must enter above the transverse process on the parapedicular approach.

Venography

Venography was never used much in Europe and was introduced in the United States in an attempt to discover potential leak sites prior to injecting cement. However, this technique worked poorly because the contrast material and the bone cement differ hugely in viscosity. I discontinued using venography in 1996 and have found no disadvantage or added risk without its use.47 Other long-term proponents have belatedly stopped its use in routine PV as they found no safety benefit to its use.48

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