Kyphoplasty

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Chapter 18 Kyphoplasty

Yong-Chul Kim, MD, PhD, Seung-Eun Shim, MD, PhD

Balloon kyphoplasty is a minimally invasive option for treating vertebral compression fractures. It can be performed as an outpatient procedure and can provide immediate pain relief. The patient can return to activities of daily living just after the procedure, which stabilizes vertebral fractures and reduces spinal deformity by restoring vertebral body anatomy and height.

The incidence of cement leakage and other procedure-related complications is low, and pain relief has been reported in more than 90% of patients. The procedure time requires 20 to 40 minutes per level, and the medical cost is higher than that of vertebroplasty. Supplementary facet joint injections or medial branch blocks may improve the level of pain relief in some cases.

Treatment objectives of kyphoplasty

The treatment objectives are to provide an early return to function, to relieve pain, and to restore the anatomy by reducing and stabilizing the fracture, restoring vertebral height, and diminishing the spinal deformity.

Indications

Kyphoplasty is performed in patients with recent vertebral fractures due to osteoporosis, angiomas, myelomas, metastasis, and so on, who present with pain refractory to conservative treatment including bed rest and drug treatment. The best results are obtained when the vertebral collapse has occurred recently—that is 3 months or less before the patient’s presentation [1,2].

Complications

There is an overall incidence rate of complications with this procedure ranges from 0 to 9.8% [4–9]. The most common is cement extravasation, which may be avoided with the following precautions [10]:

Filling the void with thick, toothpaste-like cement using a low-pressure injection yields less cement leakage than filling the interstices of a fractured vertebra with thin, less viscous cement via a high-pressure injection, as is done in vertebroplasty.

Adequate imaging with high-quality digital fluoroscopy, adequate cement opacification with sterile barium, and injection of cement which is not too liquefied can avoid leakage.

Other, extremely rare complications of kyphoplasty are as follows:

Pneumothorax and rib fracture after thoracic kyphoplasty

Pulmonary embolism

Bleeding or spinal epidural hematoma

Radiculopathy

Paraplegia

Infection

Cerebrospinal fluid leakage

Transient adult respiratory distress syndrome

Preoperative preparation

The physician should obtain a description of the presenting symptoms from the patient, which may include complaints of limitation of motion, and varying degrees of local pain with or without radiation around the trunk and further anteriorly.

The physical examination at the level of the recent fracture(s) reveals corresponding tenderness upon deep palpation and pain provoked by percussion.

The imaging diagnosis would include the following:

Plain spine anteroposterior (AP) and lateral films

Computed tomography (CT) scan with or without three-dimensional imaging to assess details of the bony architecture in cases of suspicion of a posterior cortical fracture (Fig. 18-1)

Bone scan to determine the most recent fracture(s) in patients with multiple fractures [11]

Magnetic resonance imaging (MRI) to detect signal change caused by bone edema at the level of a recent fracture (Fig. 18-2)

Figure 18–1 Computed tomography scan with three-dimensional images of a vertebral body fracture from the right (A) and left (B).

Figure 18–2 Left, A T1-weighted sagittal magnetic resonance image shows a complete vertebral body collapse (vertebra plana) at T12 and L2. A few fracture fragments of T12 compress the spinal cord anteriorly. Right, A bone scan shows no radiotracer uptake at the T12 and L2 levels, indicating chronic, rather than acute, fractures at these levels. At the L3 lower vertebral body, there is a loss of high signal intensity on the T1-weighted image and a high uptake on the bone scan image, indicating an acute pathologic process. Kyphoplasty at the T12 and L2 levels are contraindicated, whereas a kyphoplasty at L3 is indicated.

Radiologic anatomy for kyphoplasty

Radiologic landmarks for kyphoplasty should be identified as follows (Fig. 18-3)

Pedicles, to define the starting point of bone access needle on each side

Spinous process, to gauge vertebral body rotation

End plates, to enable planning of a posterior-to-anterior trajectory

Posterior cortical margin, to avoid the anterior margin of the spinal canal

Figure 18–3 Fluoroscopic views of the lumbar spine. (A) On a true anteroposterior (AP) view, the pedicles (black circles) should be located equidistant from both lateral margins of the corresponding vertebral bodies, and the spinous process should also be located at the midline of the width of the vertebral body. (B) On an oblique view, the pedicle (dotted circle) should be visualized at its widest and most circular aspects. (C) On a true lateral view, the two pedicles should be superimposed. For assessment of the location of the needle tip and its correct trajectory, frequent check of the true AP and lateral views is essential.

Methods of kyphoplasty

The two methods of kyphoplasty currently performed, along with available products for them, are as follows:

Balloon kyphoplasty (Kyphon, Inc., Sunnyvale, CA)

Bone graft kyphoplasty: OptiMesh Deployable Grafting System (Spineology, Inc., St. Paul, MN) (Fig. 18-4)

Figure 18–4 The OptiMesh system. (A) The OptiMesh graft containment device in its unfilled (left) and filled (right) states. (B) Allograft bone material prepared for the bone filling tube. (C) An expandable reamer. (D) Preoperative (left) and postoperative (right) computed tomography scans of three-level OptiMesh implantations for treatment of three vertebral fractures. (E) The surgeon fills the cavity with allograft bone through the bone filling tube. Pressure is exerted firmly with a mallet.

(Courtesy of Spineology, Inc., St. Paul, MN.)

Balloon kyphoplasty is described in detail in this chapter.

Instrumentation

Operating Room Setup

Figure 18-5 depicts the operating room setup for balloon kyphoplasty, consisting of the following:

Radiolucent operating table

A high quality C-arm (fluoroscope)

An anesthesia machine

Monitoring devices

Equipment for cardiopulmonary resuscitation

Figure 18–5 The operating room to be used for kyphoplasty contains a radiolucent operating table and a high quality C-arm (fluoroscope), both of which are mandatory for maximal procedural safety. An anesthesia machine, monitoring devices, and equipment for cardiopulmonary resuscitation are also necessary for the patient’s safety.

Kyphoplasty Kit

Figure 18-6 illustrates the components of the balloon kyphoplasty system manufactured by Medtronic, Sunnyvale, CA, use of which is described in the procedure section of this chapter:

KYPHON® Bone Access Needle, 11-gauge

KYPHON® Osteo Introducer® System (Fig. 18-7)

KYPHON® Precision Drill

Guide Pins

KYPHON® Bone filler device (Fig. 18-8)

KYPHON® Inflation Syringe, which consists of a long tube to keep the clinician out of the radiation beam, an easy to read digital pressure gauge and volume scale, and provide safe, precise control of balloon inflation (Fig. 18-9)

KYPHON® Inflatable Bone Tamp (Figs. 18-10 and 18-11)

Figure 18–6 The instruments used for a kyphoplasty.

Figure 18–7 Components of the Osteo Introducer System. From left, bone access needle, Precision drill, the Osteo Introducer, and guide pins.

(Courtesy of Kyphon, Inc., Sunnyvale, CA.)

Figure 18–8 Bone void filler device. The total volume of bone cement delivered by a bone void filler device is 1.5 mL. Use of this device allows the application of cement at a considerably higher viscosity with a lower-pressure injection, both of which reduce the risk of cement leakage.

(Courtesy of Kyphon, Inc., Sunnyvale, CA.)

Figure 18–9 Inflation syringe with volume scale (A) The digital pressure gauge and time shown on monitor. (B)

(Courtesy of Kyphon, Inc., Sunnyvale, CA.)

Figure 18–10 The balloon portion of Inflatable bone tamp (A) and the whole view of inflatable bone tamp (B) for the reduction of fractures and/or creation of a void in cancellous bone in the spine.

(Courtesy of Kyphon, Inc., Sunnyvale, CA.)

Figure 18–11 Top, An inflatable bone tamp with the potential to contain 6 mL of material for lumbar and lower thoracic vertebra. Bottom, A 4-mL capacity, inflatable bone tamp for most of the thoracic vertebra or small lumbar vertebra.

(Courtesy of Kyphon, Inc., Sunnyvale, CA.)

Bone Cement

Acrylic bone cements are the most commonly used type of bone cements for kyphoplasty. Among them, KyphX HV-R (High-Viscosity Radiopaque) Bone Cement (Kyphon, Inc.) and Concert VR Radiopaque Bone Cement (Advanced Biomaterial Systems, Inc., Chatham, NJ) are approved by the U.S. Food and Drug Administration (FDA) for use in kyphoplasty. Radiopacifier loading is usually required, and radiopacifier typically accounts for 25% to 35% of the total mass of the cement powder. (Radiopacifier-mixed brands, such as KyphX HV-R, are now available.)

Use of bone cement for kyphoplasty is associated with following potential problems:

A high exothermal polymerization temperature can lead to thermal necrosis of the soft tissues at the peri-augmentation site [12,13].

The residual liquid monomer can cause chemical necrosis of the tissue [12].

Exposure to the fumes of the liquid monomer may cause idiosyncratic or asthmatic reactions and/or lacrimation [13].

We use a bone cement mixture (CMW1, DePuy, Blackpool, UK) that consists of the following:

Powder polymethyl methacrylate (PMMA), 15 mL

Liquid PMMA, 8-9 mL

Barium sulfate, 3 mL

Other Equipment

A syringe and a 25-gauge spinal needle for infiltration of local anesthetics (see later) are also required.

Anesthesia

Conscious sedation is the anesthesia of choice for kyphoplasty; we use 50 μg of fentanyl, and 30 mg of ketorolac with or without 2-3 mg of midazolam IV. General anesthesia can be used for very anxious patients.

For local anesthesia, an agent such as 2% lidocaine or 0.5% bupivacaine is used.

Procedure

Inserting the Tools into the Fractured Vertebral Body

This step can be accomplished through the transpedicular approach, the extrapedicular approach, or the single posterolateral approach. The selection of approach depends on fracture configuration and the patient’s anatomy.

The single posterolateral approach should be restricted for special cases in which a transpedicular or extrapedicular approach cannot be performed. This approach could promote leakage directly back via the epidural veins to the epidural venous plexus along the anterior aspect of the spinal canal as a result of needle placement in the center of the vertebra rather than in the anterior quarter. Also, this approach carries the possibility of transecting the segmental artery or even injuring the exiting nerve root, because the needle trajectory potentially endangers the nerve root and segmental artery [14].

Please refer to the chapter 19 for the unipedicular approach from pages 266 to 267.

The transpedicular approach using a bipedicular approach is usually performed in lumbar and lower thoracic vertebrae; it is performed as follows:

1. The patient’s written informed consent is obtained.

2. To determine the skin entry site for the bone access needle, align the pedicles between the maximally compressed superior and inferior end plates in a true AP fluoroscopic image (Fig. 18-12A). Then turn the C-arm obliquely until the pedicle can be visualized at its widest and most round (Figs. 18-12B and 18-13). With this view, the skin entry point is at the location of the center of the target pedicle.

3. After skin infiltration of local anesthetics, a 3-mm skin incision is made.

4. The bone access needle can be advanced through the center of the target pedicle with use of a tunnel vision technique (i.e., the needle is advanced parallel to the fluoroscopic beam) without concern for accidental pedicle and end plate damage (Fig. 18-14).

5. Verification of the needle trajectory is performed as follows:

Mid-pedicle level: When the bone access needle tip is presumed to be located at the midpoint of the pedicular diameter on the lateral view, its location on the AP view should be checked; here it should be central in the pedicle outline. If the tip is located too laterally, the lateral cortical wall of the pedicle may be damaged, and ballooning of the bone tamp may not be possible. If the tip is located too medially, the medial cortical wall of pedicle may be damaged, thereby leading to spinal canal violation (Fig. 18-15).

At the posterior vertebral cortical margin on the lateral view: If the bone access needle reaches the posterior vertebral cortical margin on the lateral view, it should be just inside the medial border of the pedicle outline on the AP view and then is advanced slightly into the vertebral body. If the needle is placed too laterally, it may damage the lateral cortical wall of the pedicle, and ballooning of the bone tamp may not be possible. If the needle is placed too medially, it may result in an accidental penetration of the medial cortical wall of pedicle, thereby leading to spinal canal violation (Fig. 18-16).

Figure 18–12 The placement of the bone access needle. Aligning the pedicles between the maximally compressed superior and inferior end plates in a true anteroposterior image (A) and turning the C-arm obliquely until the pedicle can be visualized at its widest and roundest. (B). (C) Lateral image of the vertebral body and pedicles shown for comparison.

Figure 18–13 En face image obtained using a C-arm (A) and its illustration (B) for a transpedicular kyphoplasty approach. Turning the C-arm 10 to 20 degrees obliquely allows a direct view down the canal of the pedicle. The pedicle appears widest and roundest in this view. The bone access needle can be advanced using the tunnel vision technique, which assures the operator that the needle is not located too medial.

Figure 18–14 Trajectory of the transpedicular approach. (A) Anteroposterior (AP) view; (B) lateral view; (C) axial representation. Symbols along the trajectory indicate the position of the bone access needle tip at various depths of insertion: , insertion point, , point at pedicle/vertebral body junction; Δ, mid-vertebral body; The needle tip should not pass medial to the medial border of the pedicle on the AP view until it is anterior to the posterior margin of the vertebral body on the lateral view. After penetration of the posterior margin of the vertebral body, the bone access needle is advanced only approximately 5 mm beyond this position. At that time, on the AP view, the tip should be located just medial to the medial border of the pedicle.

(Modified from Spivak JM, Johnson MG. Percutaneous treatment of vertebral body pathology. J Am Acad Orthop Surg 2005;13:6-17.)

Figure 18–15 The bone access needle tip should be located at the midpoint of the pedicular diameter (blue line) on the lateral view and its location on the anteroposterior view should be verified as central in the pedicle outline (black needle on red circle) (A). If the tip is located too laterally (1), the lateral cortical wall of the pedicle may be damaged and ballooning of the bone tamp may not be possible. If the tip is located too medially (2), the medial cortical wall of pedicle may be damaged and, thereby, spinal canal violation may be anticipated. (B and C)

Figure 18–16 If the bone access needle reaches the posterior vertebral cortical margin on the lateral view (red line), it should be just inside the medial border of the pedicle outline on the anteroposterior view and is then advanced slightly into the vertebral body (A). On the schematic drawing, the black needle shows correct needle placement when the needle reaches the posterior vertebral cortical margin on the lateral view. The “1” needle shows a placement of the needle that is too lateral and may damage the lateral cortical wall of the pedicle (red circle) and ballooning of bone tamp may not be possible. The “2” needle shows a placement of the needle that is too medial and that may result in an accidental penetration of the medial cortical wall of pedicle (red circle) and, thereby, spinal canal violation. (B and C)

The extrapedicular approach is commonly used in the thoracic spine. In contrast to the transpedicular route, the skin entry point in the extrapedicular approach is more lateral than the pedicle, and the trajectory of the needle is more medially directed. The approach is performed as follows:

1. The skin entry point is lateral to the pedicle, either through the thoracic transverse process or along the transverse process–rib junction (Fig. 18-17).

2. The bone access needle is advanced along the medial border of the rib until the lateral border of the pedicle is reached on the AP view and the posterior vertebral body margin is reached on the lateral view. The tip should not pass medial to the lateral border of the pedicle on the AP view before the posterior aspect of the vertebral body is seen on the lateral view.

3. After correct needle placement has been confirmed on AP and lateral views, the bone access needle is advanced only about 5 mm beyond this position:

On an AP view, the tip should be located just medial to the lateral border of the pedicle.

Figure 18–17 The trajectory of the extrapedicular approach for needle or bone access needle placement. (A) AP view; (B) lateral view; (C): axial representation. , insertion point; , point at pedicle/vertebral body junction; Δ, mid-vertebral body;

(Modified from Spivak JM, Johnson MG. Percutaneous treatment of vertebral body pathology. J Am Acad Orthop Surg 2005;13:6-17.)

Placing and Inflating the Bone Tamp

The bone tamp is placed (Fig. 18-18) and inflated (Fig. 18-19) as follows:

1. The bone access needle is exchanged for an Osteo Introducer needle over a guide pin.

2. The Osteo Introducer needle is positioned near the posterior vertebral body margin while the working instruments, such as precision drill, bone tamp, and bone filler device, are advanced anteriorly until they are approximately 3 mm from the anterior vertebral body border. Careful observation of the working instruments on a lateral view is very important to avoid accidental penetration of the anterior vertebral body border.

3. The inflatable bone tamp is inflated with liquid contrast media to 50 psi.

Figure 18–18 Sequence of procedures for the insertion of the bone tamp. (A) to (C) The bone access needle is exchanged for an Osteo Introducer (Kyphon, Inc.) over a guidewire. (D) to (F) The Osteo Introducer is positioned near the posterior vertebral body margin while the working instrument is advanced anteriorly until they are approximately 3 mm from the anterior vertebral body border. (G and H) The inflatable bone tamp is positioned after removal of bone filler. (I) The inflatable bone tamp is inflated with liquid contrast medium to 50 psi.

(Courtesy of Kyphon, Inc., Sunnyvale, CA.)

Figure 18–19 Inflating the bone tamp and the fluoroscopy shows the balloon filled with contrast media in lateral (A) and AP view (B).

The allowable balloon pressure in cancellous bone ranges from 70 to 300 psi (the maximum allowable pressure is 300 psi). The pressure will typically increase until the bone yields, allowing the balloon to expand. As the bone shifts, the pressure in the balloon will gradually decrease.

Mixing the Cement and Filling the Void

A discussed previously, the mixture of cement to be used (CMW1 bone cement, DePuy, Blackpool, UK) is 15 mL of powder PMMA, 8 to 9 mL of liquid PMMA, and 3 mL of barium sulfate.

The factors influencing the cement hardening time included the following:

Amount of barium sulfate

Quantity of solvent

Mixing time

Ambient temperature

Irrespective of individual varying hardening times for the multitude of cements available, the consistency must always remain constant.

1. Bone cement with thick paste-like consistency can be filled into the vertebral body cavity created by the inflatable bone tamp. As a result of the thicker consistency, the incidence of cement leakage in the cases of kyphoplasty is significantly lower than that of vertebroplasty (Fig. 18-20).

2. Injection is continued until the void filling is achieved (Fig. 18-21). It is stopped immediately if any extravasation is noted into the surrounding veins, the spinal canal, or the disc space.

3. After completing the injection, the Osteo Introducer needle is removed, and hemostasis is obtained by pressure.

4. The cement filler should be removed after the hardening time needed for the specific cement used has passed (Table 18.1).