Early studies performed vertebroplasty only after conventional treatment (medication and rest) had failed.⁸ Later series have advocated treatment as early as weeks or days if the patient requires narcotic medication or admission to hospital secondary to pain. Others have recommended vertebroplasty within 4 months.³ Although late treatment is unlikely to be successful, there are case reports of patients being successfully treated after a few years.⁹

Even though some believe it is a reasonable indication,¹ there are insufficient data to categorically support the treatment of painful tumor infiltration without fracture. In addition, it is unclear whether to treat before or after radiation therapy. Injection of cement into the vertebral body will likely dislodge marrow elements that could potentially be absorbed into the blood stream. This concern for causing metastatic dissemination suggests that vertebroplasty should be performed only after radiation therapy.

Prophylactic vertebroplasty is neither widely accepted nor approved for osteoporotic vertebral compression fractures and no studies have been done to substantiate the utility of this practice.¹

TECHNIQUE

1. Pre-procedure planning. MRI, computed tomography (CT), and X-ray images of the fracture are evaluated in all views specifically looking for the angle of approach to the vertebra through the pedicle. Because normal anatomy (Fig. 32.1) is altered by the fractures, the approach to the body of the vertebra through the pedicle is altered. This altered bone architecture must be carefully analyzed by reviewing all the available radiological films. Specifically, the cortical margins of the bone are reviewed in anteroposterior (AP), lateral, and axial views to preplan the pathway of the trocar to the exact target area within the vertebral body. The angle will be altered based on the characteristics of the fractured vertebra. The vertebra may be approached through one pedicle or both pedicles. If the angle of insertion is achieved in such a way that the tip of the trocar is in the center of the body, then one may use a single-pedicle approach. If the trocar lies on one side of the body of vertebrae, then the other pedicle may be used to approach the other side of the vertebral body.

2. Prior food and medication. For procedure performed in the morning, the patient is informed not to eat or drink after midnight, but is allowed to take medications. When conscious, sedation is used for a procedure to be done later in the day, and the patient should not drink or eat for a minimum of 4 hours beforehand. Diabetics and other chronic medical illness management including the timing of anticoagulants should be coordinated with the primary care physician.

3. Prophylactic antibiotics. Intravenous antibiotics (cefazolin 1 g) are given 30 minutes before the procedure. Ciprofloxacin 500 mg orally twice a day may be given, if the patient is allergic to other medications and should be started 12 hours before the procedure and continued 24 hours after completion of the procedure.⁶

Fig. 32.1 Pedicles. (A) Axial view. (B) Lateral view.

We do not give any prophylactic antibiotics and prescribe antibiotics postoperatively for a week.

4. Position of patient. The patient is placed in a prone position for surgery in the thoracic and lumbar region and supine for cervical region.³ It is critical to confirm the level of pain and fracture under fluoroscopy before beginning vertebroplasty.¹ Applying pressure with the thumb or palm of the hand over each spinous process or side-to-side movement of the spinous process will often elicit tenderness. As the patient is awake during the procedure and placed in a prone position, the patient should be made comfortable with padding and arm supports.

5. Anesthesia. Percutaneous vertebroplasty is performed using local anesthesia typically combined with neuroleptanalgesia ^2,^3,^5,^10,¹¹ or general anesthesia.^10,^11,¹² The authors use a combination of intravenous midazolam (Versed; Roche, Manate, Puerto Rico) and fentanyl (Sublimaze; Abbott Laboratories, North Chicago, IL).^13,¹⁴ Dosages are based on patient size and condition and can be titrated during the procedure based on the patient’s response. General anesthesia is rarely used for this procedure. Two to 3 ml of 1% solution of lidocaine injected into the marrow through the needle will relieve pain, which some patient may experience when cement is injected into the bone.^6,¹⁵

6. Prepping and draping. The skin is prepared with iodine and then draped. As the position is checked many times in AP and lateral views, the field of procedure should be well protected with sufficient drapes.

7. CT scan versus C-arm fluoroscopy. Vertebroplasty is performed using biplanar fluoroscopy,^3,¹¹ C-arm fluoroscopy, and dual-guidance CT.^3,¹⁶ CT is only used for extremely difficult cases, such as tumor destruction of the posterior vertebral wall⁶ or vertebra plana.¹⁷ When using a single-plane C-arm fluoroscopy all the movements during the procedures should be confirmed in two planes, AP and lateral.

8. Approach to the vertebral body. Cervical vertebroplasty has been done with transoral approach,^18,¹⁹ lateral, and anterolateral approach.²⁰ The authors do, however, have concerns about the transoral approach. This technique necessitates traversing the oropharynx which is riddled with bacteria ready to flourish in the vertebral body. Consequently, we prefer the anterolateral approach used by Deramond in the first described vertebroplasty procedure.²¹ As osteoporotic fractures are rare in the cervical area, vertebroplasty is rarely done in the cervical region except for conditions such as tumors. During the needle placement one must be careful to avoid the carotid artery and internal jugular vein.⁶ Both structures are displaced laterally and the esophagus and trachea medially to reach the body of cervical vertebrae (Fig. 32.2).

Fig. 32.2 Cervical body, anterior.

The thoracic and lumbar vertebral bodies are usually approached through one or, most commonly, both pedicles.^2,^8,²¹^–²⁷ Various approaches are used including a costovertebral,⁵ paravertebral, posterolateral, or anterolateral (cervical) approach. The parapedicular or transcostovertebral²⁸ approach is used when a transpedicular approach cannot be used because of small pedicles, a fractured pedicle, or tumor invading the pedicle. Like most physicians, the authors prefer the transpedicular approach instead of the parapedicular approach, which may increase the chance of both a pneumothorax and that a paraspinous hematoma may not be controlled with application local pressure.⁶ The posterolateral approach increased the risk of injuring the exiting nerve root and segmental artery,⁶ and has largely been abandoned although some authors recommend it for lumbar vertebrae.^20,^23,²⁸

There are many companies which supply cement and delivery equipment: Parallax Medical Inc./Arthrocare Corporation; Cook Group Inc.; Interpore Cross International Inc.; Interpore Cross International Inc./American OsteoMedix Corp.; Medtronic Inc./Medtronic Sofamor Danek; Orthofix International NV/Orthofix Inc.; Stryker Corp.; Tecres SPA.²⁹ These sets contain stylets, needles, tubing, injectors, and injector barrels, but the end result is the same. The equipment allows one to inject cement into the anterior part of the vertebral body. Some authors have, however, modified the equipment and technique,³⁰^–³³ and before these sets were available, operators recommended using 1 mL syringes for injection of cement.^7,^11,^17,²⁴

9. Needle insertion. Mark a point on the skin after viewing the fractured vertebra in the anteroposterior and lateral views. This is the planned insertion site of the cannula. The initiation site should correspond with superolateral aspect of the pedicle. It should not be near the inferior or medial margins of the pedicle. Local anesthetic is infiltrated into the skin, subcutaneous tissue, and up to the periosteum of the pedicle. We inject 2–3 mL of lidocaine 1% with 25-gauge 1.5 inch needle for local anesthesia (Fig. 32.3).

Fig. 32.3 Injecting local anesthetic.

A small incision is made using a No. 11 knife blade and the introducer needle from the set is inserted (Fig. 32.4). A 15-gauge needle is used for cervical vertebrae and 10-gauge for thoracic and lumbar vertebrae.³ Currently, even thinner needles (13-gauge) are being used.⁶ The needle entry site is localized in the AP view. The authors use a diamond-tipped needle to start the entry.

Fig. 32.4 Needle is inserted and viewed on the monitor with the clamp holding the needle.

During the procedure, one must confirm all the movements and steps in both the AP and lateral fluorosopic views.

The needle is held with forceps to minimize radiation exposure to the operator.⁶ After confirming the position, the vertebroplasty needle is advanced through the superior-lateral cortex of the pedicle (Fig. 32.5). The vertical and horizontal diameter of the pedicle increases from upper thoracic to lower lumbar vertebrae (Table. 32.1). Proximally, in the sagittal plane, the direction of the pedicle is more oblique. (Fig. 32.6)

Fig. 32.5 Initial tap into the pedicle.

Table 32.1 Vertical and horizontal pedicle diameter

Pedicles	T3	L4
Vertical diameter	0.7 cm	1.5 cm
Horizontal diameter	0.7 cm	1.6 cm

Fig. 32.6 (A) Direction of insertion of the trocar and cannular (axial view). (B) Approach to vertebra on lateral view.

The authors start with a diamond-tipped needle and then change it to beveled needle to make directional adjustments.⁷ The bevel of the needle is directed so that the tip is pointed laterally to avoid the spinal canal.

The needle is directed anteriorly, medially, and inferiorly through the pedicle to reach the anterior third of the vertebral body in the midline in the sagittal plane.

Incremental changes in position of the needle are observed in the AP and lateral views to ensure that the proper pathway is being pursued.

In osteoporotic bones it may be easy to advance the needle by hand, but in cases where the bone is dense, as in pathologic fractures, a mallet is necessary to advance the needle.⁶ While advancing the needle by hand the direction of needle may change, and using the mallet may keep the needle advancing in the direction wanted. We invariably use a mallet to advance the needle as this provides much greater control of the needle direction. As the needle is slowly advanced through the pedicle, we are hypervigilant about the location of the needle tip and the orientation of the needle. At no point do we want to breach the medial wall and subject the patient to the risk of cement extravasation into the spinal canal. When we reach the anterior part of the pedicle on lateral view, the trocar should be just lateral to the medial border of the pedicle on anteroposterior view. This ensures we are not going to break the medial wall of the pedicle. In addition, we do not want to fracture the roof or the base of the pedicle and inadvertently pierce an exiting nerve root. Advancing the needle through the lateral border of the pedicle will deposit cement intramuscularly. We have experienced this latter scenario on a few occasions and it is not associated with any adverse effects. Theoretically, it is conceivable that the needle could be placed too close to the aorta if the needle breaks through the lateral margin of the left pedicle, but this is a highly unlikely event. It is also important to be sure that the angle of inclination will allow the needle to ultimately rest in the anterior one-third of the vertebral body. To obtain ideal terminal position, it is critical that one repeatedly re-checks the cephalocaudal tilt while traversing through the pedicle. It is very difficult to re-orient the angle of inclination once the needle has passed through the pedicle and enters the vertebral body. If the angle of inclination is too steep then gentle downward pressure on the hub will minimize this angle, especially if the needle is still within the pedicle. We emphasize the term ‘gentle’ since osteoporotic bone can easily fracture if aggressive motions are used. If such gentle pressure does not achieve the intended result, a beveled needle can be substituted for the diamond-tipped needle. The bevel can be rotated so that the needle courses in the direction of choice. After the needle is observed to enter the vertebral body using a lateral view, the AP perspective does not need to be checked until the cement is injected. An AP view is needed at three points during the procedure: when planning where to insert he needle, checking the progress of the needle as it courses through the pedicle, and then later when cement is injected. Once the needle is in the vertebral body it should be rotated so that the tip is opening medially.

10. Biopsy. If a biopsy is required, it is done by introducing the needle coaxially ³⁴ or thorough the needle. The biopsy is done before the cement is injected.¹ The authors introduce a thinner biopsy cannula through cannula already through the pedicle. Biopsy kits are commercially available and the biopsy needle size is compatible with the vertebroplasty cannula. After the trocar and cannula have been placed in the vertebral body through the pedicle, the trocar is removed. The biopsy needle is inserted through the vertebroplasty cannula. The biopsy needle is longer than the vertebroplasty cannula and precaution should be taken not to pierce the anterior cortex. The authors initially stop the vertebroplasty cannula in the posterior third of the vertebral body. The biopsy needle is then inserted and advanced through the vertebroplasty cannula in a rotating motion and then pulled out. After the biopsy is obtained, the trocar is reinserted into vertebroplasty cannula and it is advanced anteriorly to the target area.

11. Another needle may be placed in the contralateral pedicle in the manner mentioned above for bipedicular approach.

12. Venography can be done after achieving the correct position with the needle.^10,²⁸ Contrast dye is injected into the vertebral body and leakage can be visualized under fluoroscopy. Because the viscosity of the contrast material and bone cement is so different, venography may not be an accurate assessment of the embolization risk.⁶ In fact, venography is seldom used in Europe and is only done in United States to discover the potential leak sites. Some authors, however, continue to defend its use,^2,^35,³⁶ while others have either seldom^7,^37,³⁸ or never used venography.^39,⁴⁰ Embolization of vascular lesions may be done by microfibrillar collagen after venography.²

13. Cement preparation. Bone cement, approved by FDA specifically for vertebroplasty with radio opaque material already incorporated, is available.

There are two kinds of cement, slow set or fast set. The authors prefer the fast-set cement. Prior to starting the procedure we place the monomer in a refrigerator. Cooling the liquid slows the set time, allowing a few extra minutes to complete the procedure. Once the monomer and cement powder are mixed, a chemical reaction ensues that cannot be aborted, which ultimately results in hardening of the mixture. Once this reaction has progressed beyond a certain point it becomes impossible to advance cement through the delivery apparatus. So, cooling of the monomer decreases the kinetic energy and slows the chemical reaction time, thereby providing a few extra minutes to the potential cement delivery time. Some interventional spine physicians have suggested altering the monomer to powder ration as a method of altering the set time. We do not do this and do not advocate such a solution. Using polymethyl methacrylate (PMMA) for vertebroplasty is considered off-label use although it is off-label only because of the ratio of monomer to cement powder. But before one modifies the cement preparation, one must first understand that the mechanical properties of the cement would be inextricably altered. Second, and probably most important, is that the amount of free or unbound monomer would likely increase, which could lead to increased complication due to intravascular monomer uptake.

The typical concentration is 0.40 mL of PMMA powder (SimplexP; Stryker-Howmedica-Osteonics) combined with 6 g of sterile barium sulfate powder, tantalum,^3,¹¹ or tungsten (Figs 32.7, 32.8).¹⁰ The barium sulfate powder is included to better visualize the PMMA under fluoroscopy. The safety of the procedure depends on cement leakage rather than the type of cement used.⁴¹ In addition, before adding the 10 mL liquid monomer, one can add 1 g of tobramycin antibiotic to reduce the chance of disc space infection.^5,^25,^42,⁴³ Some authors, including ourselves, recommend not adding antibiotics to PMMA unless the patient is immunocompromised.^6,¹⁷

Fig. 32.7 Mixing PMMA and barium.

Fig. 32.8 Preparing cement.

After the barium is added to the powder, the polymer is added to the monomer using a 10 cc syringe and an 18-gauge, 5” needle. The tube is closed and the mixture is shaken vigorously for 45 seconds. Open mixing should be avoided to maintain a sterile environment.

While one is mixing the cement, an assistant connects the long, flexible tube for delivery to the injector barrel. The bone cement preparation is mixed until a doughy, cohesive consistency (similar to toothpaste) is obtained. We delay the polymerization process by cooling the polymer in the refrigerator for an hour before the procedure and this gives additional working time.^6,⁴⁴

In limited circumstances, slow-set cement Cranioplastic type 1 Slow Set (Codman/Johnson & Johnson, Berkshire, UK), at room temperature can be used.^6,³⁵ Rapid-set material has the advantage as it rapidly sets in case of leaks, as seen with these procedures. If a cement leak is observed on fluoroscopy, one can stop for a few minutes till the fast cement hardens and blocks that area. As the leaking area is blocked by the hardening cement, more cement may be re-injected. One should look for cement flowing into the opposite direction to the area where the previous cement had already hardened. The cement will rapidly polymerize and will plug the leak in 1–2 minutes and further cement can be injected, which is not possible with slow-setting cement. In addition, slow-setting cement stays liquid longer in the body and thus could potentially leak for a longer time and may leak along the needle tract when the needle is pulled out.⁶

Once mixing is completed, the bone cement is slowly poured into the injector tube (Fig. 32.9). The injector device is attached and rotated till the cement starts pouring from the tip of the flexible tube (Figs 32.10, 32.11). One can see the consistency of the cement at the end (Fig. 32.12). The flexible tube is connected to the needle inserted earlier into the vertebral body (Fig. 32.13).

14. Cement injection. The paste-like cement is slowly injected into the vertebral body under constant fluoroscopic control with help of the injector device (Fig. 32.14). The amount of cement injected is monitored under fluoroscopy and the quantity can be measured from the labeled injector tube. The objective is to fill the anterior two-thirds of the vertebral body as seen on the lateral view. If required, further cement can be injected from the contralateral pedicle cannulation.³ At times, the cement does not flow according to the plan. The cement may pool in front of the needle, and the cannula may be repositioned by slightly moving anteriorly or posteriorly. If the cement is moving into the anterior part of the vertebral body, the cannula can be withdrawn slightly and one can then inject more cement. If the cement is flowing to the posterior or lateral part of the vertebral body, the inserting device can be rotated in the opposite direction to create a negative pressure. In some cases, cement may fortuitously flow to the opposite side of the vertebral body and injection through the second pedicle may not be required.

Fig. 32.9 Pouring cement into the chamber.

Fig. 32.10 Connecting the rotator.

Fig. 32.11 Connecting the delivery tube.

Fig. 32.12 Checking the consistency of the cement.

Fig. 32.13 Connecting the delivery tube to the needle.

Fig. 32.14 Ready to inject with hands out of the radiation field.

Vital signs should be monitored looking for hypotension, as cement injection has been known to cause hypotension in patients undergoing joint replacement surgery.^45,⁴⁶

15. Amount of cement. Total volume of cement injected is commonly 2–8 mL.^3,⁶ Outcome, however, is not related to the amount of cement injected, and even 2 mL of cement injected has been reported to provide pain relief.⁴⁷ Only a small amount of bone cement (≈15% volume of fill) is necessary to restore compressive stiffness of the damaged vertebral body to its value before damage.⁴⁸

The injection of cement is stopped whenever epidural or paravertebral opacification is observed or when the cement reaches the dorsal quarter of the vertebral body.³ If extravasation of cement is seen, further injection of cement is stopped. The extravasation is evaluated in both AP and lateral views. If it is considered safe to proceed with the procedure, the needle position should be adjusted. Another needle can also be placed from the contralateral pedicle.

16. Removal of the needle. The stylet should be repositioned into the needle before removal of the needle whenever possible to prevent cement leak.³ The authors prefer not to place the trocar as that may lead to unmonitored injecting of cement. We leave both cannulas in the vertebral body till the cement is injected from the cannula. If one cannula is pulled out before the cement is injected into the second pedicle, then one is potentially providing a route for cement to leak from the first pedicle.

17. Dressing. Local pressure is applied at the skin puncture site to prevent any bleeding. The puncture site is closed with steristrips and a sterile dressing applied.

Postprocedure

The cement polymerizes in 1 hour and the patient remain recumbent in supine position for that duration. The patient may be discharged after an hour of monitoring.⁵ At our center, we discharge patients after keeping them for 1 hour postprocedure, or if medically required we admit them overnight.

The patient is discharged with narcotic medication to be used on an as-needed basis and is prescribed Keflex for a week. If the patient is allergic, ciprofloxacin is prescribed. The patient is not given any brace on discharge.

Multiple compressions

Multiple-level vertebral compression fractures may be treated by percutaneous vertebroplasty. It is less cumbersome to stagger needles by alternating between right and left pedicles.² However, there may be additional stress on the adjacent vertebrae.⁴⁹ If there are multiple compression fractures, one should treat the most painful fracture first.¹ No more than two should be treated on a particular day. It is the authors’ preference to treat a single vertebral fracture per day to ensure monomer toxicity risk is minimized. Incidence of venous extravasation of cement or fat⁵⁰ increases with multiple-level treatment.

Repeat vertebroplasty

If the recurrent pain arises from a vertebra previously treated with vertebroplasty, repeat percutaneous vertebroplasty offers therapeutic benefit.³⁷ Repeat vertebroplasties may be approached from the pedicle opposite the previous insertion.^37,⁵¹

AVOIDANCE OF COMPLICATIONS

The complications are minimal if precautions are taken.⁵²

Leakage of cement

Leakage of cement can cause neurologic injury or pulmonary emboli.⁵³^–⁵⁶ One can, however, prevent cement leaks by using high-resolution fluoroscopy (or rarely CT), adequate cement opacification, and by interrupting or terminating the procedure on first recognition of a leak. Biplanar fluoroscopy is not required but does make visualization in two projections simpler and faster. One must visualize the vertebra in two planes numerous times. The authors use a uniplanar machine which is rotated at every step to obtain anteroposterior and lateral views. Sterile barium sulfate is added to bring the barium quantity to 30% by weight, making the cement opaque for visualization under fluoroscopy. Presently, FDA approved premixed cement for vertebroplasty is available commercially. Terminating injection when early leakage of cement is visualized limits the size of the leak and usually prevents it from becoming significant. Venography has been used to observe leakage but it does not accurately predict the leak of cement.¹⁴ If there is leakage into the spinal canal with neurological deficit, a neurosurgeon or spinal surgeon should be consulted.^57,⁵⁸

The cement emboli can leak into the valveless veins of the vertebrae and migrate into the paraspinal plexus which drains into the azygous vein. The azygous veins empty in to the right atrium of the heart, after which blood then flows to the lungs. Asymptomatic leakage of the cement routinely occurs and a patient with mediastinal problem had an MRI of chest done at our center. Small emboli of cement were observed in the lungs and he had previous history of percutaneous vertebroplasty. This patient probably had asymptomatic multiple microemboli of cement. The PMMA cement emboli were not the source of his problem.

Pain exacerbation

At times the pain may exacerbate due to local ischemia or increased pressure. A CT scan be immediately obtained to ensure no leakage. Otherwise, the pain usually resolves in a few hours or a few days.¹⁴ We discharge all patients with narcotic medication (oxycodone) to be used on an as-needed basis. If radicular pain occurs secondary to leakage into the neural foramen, within 10–20 minutes we inject 10 cc of 0.2% lidocaine followed by 100–200 cc of pressurized saline perfusion.^59,⁶⁰ During the injection, the patient may feel some pressure, but the surgeon should be aware of this and slow or stop injection if significant radicular pain occurs.