6.1 Introduction

The first vertebroplasty was performed in 1984 and then introduced in the literature by Galibert et al in 1987. ¹ Polymethyl methacrylate (PMMA) cement was injected percutaneously via a transoral approach into a C2 vertebra that had been partially disrupted by an aggressive vertebral hemangioma. This injection of cement was effective in decreasing the patient’s pain and discomfort for an extended period of time. In spite of the fact that the first vertebroplasty was accomplished via a transoral approach, this is currently one of the least commonly utilized approaches to the vertebral bodies that exist.

A posterolateral extrapedicular approach was subsequently used in the thoracic spine, but after cement leakage along the track of the needle induced a case of intercostal radiculopathy, the transpedicular needle approach was developed. With the transpedicular approach, the needle passed through the pedicle into the vertebral body and was thought to result in a lower risk of cement discharging posteriorly along the needle track. ²

Since the introduction of vertebral augmentation procedures, many approaches have been explored to provide the safest and most effective treatment of pain and deformity resulting from many types of vertebral body compression fractures. In addition to the anterolateral procedure first described, approaches now include transpedicular, extrapedicular, parapedicular (▶Fig. 6.1), and modified extrapedicular and parapedicular approaches. In the cervical spine, the anterolateral approach has been employed (▶Fig. 6.2). The transpedicular approach directs the needle through the longitudinal axis of the pedicle into the vertebral body. The parapedicular path enters the vertebral body at the vertebral body/pedicle junction near the mid to superior point and traverses into the vertebral body without breaching the medial pedicle wall. Finally, the extrapedicular approach enters the vertebral body directly either just lateral to the transverse process at the level of the pedicle progressing horizontally into the vertebral body or accessing the vertebral body just anterior to the pedicle and just above the inferior end plate entering the vertebral body at a 45-degree angle. Both of these extrapedicular approaches are performed without passing through the pedicle. The choice of approach will depend on many factors, including fracture level and vertebral morphology, as well as operator experience and preference.

6.2 Indications

The most common indication for percutaneous vertebral augmentation is stabilization of a painful osteoporotic vertebral body compression fracture. Other common indications include fracture nonunion, pain from a primary tumor, osteolysis following malignant infiltration of a vertebra, pain from vertebral body involvement of an aggressive hemangioma, and a painful fracture resulting from osteonecrosis. ^{3 – 9}

6.3 Anatomy

Each vertebra consists of a body and a vertebral arch with articular, transverse, and spinous processes. The vertebral body consists primarily of cancellous bone and marrow encased by cortical bone at the margins, including the superior and inferior end plates. The vertebral arch consists of right and left pedicles (which connect it to the body) and right and left laminae (▶Fig. 6.3). The transverse processes project laterally at the junction of the pedicles and laminae, and the dorsal or posterior spinous process projects from the midline junction of the laminae. Postganglionic nerve roots exit bilaterally beneath the pedicle via foramina. Thoracic intercostal arteries and four pairs of lumbar arteries are located adjacent to the vertebrae.

6.4 Bilateral versus Unilateral Approach

There are substantial data supporting the bilateral approach for optimal outcomes in vertebral augmentation with balloon kyphoplasty; however, the unilateral approach may offer similar outcomes with reduced operative times and radiation exposure.

In a retrospective study of 296 patients with osteoporotic VCFs, Bozkurt et al identified significantly better height restoration following bilateral kyphoplasty compared to unilateral kyphoplasty and vertebroplasty. ¹² The advantage of height restoration with a bilateral technique is also supported by a meta-analysis of five studies that reported a short-term follow-up. ¹³ Bilateral kyphoplasty had a significantly (p = 0.03) better degree of anterior vertebral height restoration than unilateral kyphoplasty. ¹³

The unilateral approach was first introduced in an effort to overcome the challenge of visualizing superimposed cannulas and the second injection site in the lateral view. Depending on the fracture and vertebral morphology, pedicle size, pedicle angle of entry, bone quality, and experience of the operator, the unilateral approach has been used with equal success and favorable outcomes.

When multiple levels are being treated, they are typically all cannulated before the injection, allowing the bone fill material to be mixed once and injected in short order. If the levels to be treated are contiguous and the distance between levels is relatively small, the side of needle placement can be alternated for multiple unilateral approaches. This can significantly reduce operative time and radiation exposure to the operator as well as to give more working space for the needles than the same procedure with all of the levels done from the same side.

Several large systematic reviews of randomized control trials have examined the differences in height restoration, correction of kyphotic angulation, and patient ratings of pain associated with unilateral and bilateral approaches.

Favoring the unilateral approach, an analysis of 15 randomized controlled trials including 850 patients by Yang et al found no difference in quality of life or complications from surgery. ¹⁴ Chen et al found that the unilateral approach resulted in a shorter operative time, a smaller amount of cement injected, and a lower risk of cement leakage. ⁶ There was no statistically significant differences in Visual Analog Scale pain scores, height changes, or kyphotic angle changes between the groups. ¹⁵ Papanastassiou et al found no difference in clinical or radiological outcomes in multiple myeloma patients treated with the unilateral approach. ¹⁶ In a review of five studies including 253 patients, Huang et al found no clinically important differences but suggested that unilateral kyphoplasty is advantageous due to decreased operative time and cost. ¹⁷ Similarly, in a systematic review and meta-analysis including 563 patients, Sun et al noted that the unilateral approach led to decreased surgical time, cement consumption, and cement leakage; reduced radiation dose and hospitalization costs; and improved short-term general health. ⁹ In a comparison between unilateral transverse process-pedicle and bilateral puncture techniques in percutaneous kyphoplasty, Yan et al noted that both bilateral and unilateral approaches for kyphoplasty provide effective treatment for patients with painful osteoporotic VCFs. ¹⁸ However, patients treated with the unilateral procedure received significantly less radiation, had shorter operation time, fewer complications, and significantly less cement leakage. In this study, the unilateral approach offered a higher degree of deformity correction, local sagittal angle, and vertebral body height restoration (anterior and posterior). Although both techniques had the ability to restore vertebral height and to improve alignment, more postoperative height was restored in the unilateral group. This was attributed to the bone cement distribution, which was placed mainly in the anterior and middle vertebral bodies. ¹⁸

In the bilateral group, 10.5% of patients had obvious pain in the puncture sites at 1 month postoperatively. With local block treatment, the pain disappeared in all patients at the last follow-up. ¹³ These complications were probably related to puncture technique as this issue has not been commonly reported. Compared with the bilateral technique, the puncture point of the unilateral technique was more lateral to the facet joint. Therefore, in the unilateral group, the violation of facet joint was rare and the bone cement was mainly distributed in the anterior and middle of the vertebral body. ¹³ There was no statistically significant difference in pain relief and functional improvement between the two groups during the 12-month follow-up. Similar clinical outcomes were achieved with either treatment procedure. ¹³

In general, based on the above manuscripts and analyses, the unilateral approach provides the advantages of reduced procedure time, costs, radiation exposure, and cement leakage with improved short-term health. Kyphoplasty using a bilateral approach has been shown to provide significantly less vertebral height loss over 2 years than the same procedure performed via a unilateral approach. ¹⁹ There appears to be no significant difference in pain reduction or quality-of-life improvement when comparing the unilateral versus bilateral approaches. ¹⁸ Procedural complications, such as cement leakage, show varied results among studies and may be operator dependent and dependent on which imaging modality is used to detect this extravasation as computed tomography (CT) is more sensitive at detecting small amounts of extravasation as compared with plain film radiography or fluoroscopy.

6.5 Imaging and Equipment

The procedure is guided with single-plane or biplanar fluoroscopy or, in some cases, CT. In our experience, fluoroscopy is sufficient to identify the salient anatomy and affected vertebral bodies. If uncertainty remains about the fracture anatomy and extent of vertebral involvement, CT may be performed. Fracture age and anatomy can be assessed with magnetic resonance (MR) imaging. ^{3 , 20} Nuclear bone scan imaging may also be helpful in characterizing a fracture, although the anatomic detail is limited and the spatial resolution poor.

6.6 Procedure

As with any image-guided procedure, preoperative positioning of the patient and fluoroscopes is paramount. Either conscious sedation or general anesthesia may be performed, but most patients with VCFs have multiple comorbidities and conscious sedation would be preferred over general anesthesia in this fragile patient population. The patient is positioned prone with shoulder and pelvis/hip bolsters. All pressure points are padded. The lateral image should be a “true lateral” that demonstrates the posterior margin of the vertebral body, spinal canal, and an optimized view of superimposed pedicles. The adjacent vertebrae can be used as guides if there is significant deformity of the fractured body. The AP view should be directed such that the spinous process is midline and both pedicles are visible and similar in size and shape and in the upper half of the incident vertebral body (▶Fig. 6.4). In this way, two-dimensional imaging is used to guide a three-dimensional approach. Although we routinely use this fluoroscopic approach, some may prefer the en face approach, a view straight down the pedicle that demonstrates a circle or oval outline of the edges of the pedicle for guidance (▶Fig. 6.5). This requires a 10- to 30-degree ipsilateral oblique angulation from the true AP. It is important to remember that the lateral imaging is used only for superior and inferior directional adjustments, while the AP image is only to be relied on for guidance with medial and lateral corrections.

All vertebral augmentation procedures require the establishment of a working channel for delivery of cement or an implant. Each of the following approaches begins with a small (~5 mm) skin incision and the introduction of a Jamshidi-style needle to establish the working channel extending into the vertebral body. An 11-gauge Jamshidi needle is generally used in the lumbar and lower thoracic spine. Smaller needles may be used in upper thoracic spine and as needed at other levels. Larger needles may be used in the lumbar spine or during the insertion of vertebral body implants. Needles are available in 10- to 15-mm lengths.

6.6.2 Transpedicular Approach

The basic bilateral transpedicular approach is considered standard for percutaneous access to the lumbar and lower thoracic vertebrae (▶Fig. 6.6). The transpedicular needle path offers protection for the surrounding tissues, including the postganglionic nerve roots, but is most likely to require bilateral needle insertion to accomplish proper balloon placement and adequate cement fill. In the upper thoracic spine, the transpedicular approach will not allow proper medial placement of the instruments and balloons placed too laterally will not achieve proper fracture reduction and may result in violation of the lateral cortex before fracture reduction is achieved.

Following sterile preparation and confirmation of appropriate imaging, the incision site just superior and lateral (1–2 cm) to the target pedicle is determined (▶Fig. 6.6). The surgeon must visualize the passage of a working channel from that site through the length of the pedicle and two-thirds of the vertebral body, ending at or near the midline. The imagined course must not enter or traverse the spinal canal. Corresponding lateral and AP landmarks along the course (▶Fig. 6.6) will ensure that instruments do not stray from the planned trajectory, risking injury.

Landmarks that must be identified include the pedicles, the spinous process, and the end plates (▶Fig. 6.6). In a true AP view, the spinous process will be midline and the pedicles will be seen as symmetric ovals equidistance from the process and superimposed over the upper half of the vertebral body. End plates will be parallel (allowing for defects of the fracture). It is very important to locate these landmarks on true AP and lateral images before beginning (▶Fig. 6.6). After injecting local anesthetic, a small approximately 5-mm stab incision is made (▶Fig. 6.6). The Jamshidi needle is introduced and “docked” at the superolateral border of each pedicle (“10 and 2 o’clock positions”’; ▶Fig. 6.6). Just as the AP imaging demonstrates this starting point (▶Fig. 6.6), lateral imaging should confirm that the needle tip is at the posterior margin of the pedicle (▶Fig. 6.6). As the needle is advanced, it should reach mid-pedicle on both AP (▶Fig. 6.6) and lateral imaging. As the needle reaches the medial aspect of the pedicle as seen on AP imaging (▶Fig. 6.6), it should be seen in or near the posterior portion of the vertebral body on lateral imaging (▶Fig. 6.6). The needle must not violate the medial pedicle wall, thereby entering the spinal canal and risking serious injury. After the Jamshidi needle is advanced via the pedicle into the vertebral body, a contralateral needle is placed if necessary. When performing a vertebroplasty, the needle(s) is/are advanced into the anterior one-third of the vertebral body and cement is then injected (▶Fig. 6.7). During a balloon kyphoplasty procedure, the needles are place approximately 0.5 to 1.0 cm into the posterior portion of the vertebral body and then either a bone biopsy needle (if a biopsy is desired) or a drill is passed into the anterior portion of the vertebral body up to within 0.3 to 0.5 cm of the anterior vertebral body wall cortex (▶Fig. 6.8).

In the case of balloon kyphoplasty, the bone tamp (balloon) is inserted through the working channel and guided into the tract created by the drill (▶Fig. 6.8). The radiopaque markers on the tamp are visualized distal to the cannula sheath on at least the lateral view (▶Fig. 6.8) but preferably both the AP and lateral fluoroscopic images. This procedure is repeated on the contralateral side and each bone tamp is inflated (▶Fig. 6.8) while being monitored with AP and lateral imaging. In the case of kyphoplasty, manometric controls are used to monitor the pressure of the balloons as they are inflated in small increments to the intended pressure. The inflation is done according to a combination of pressure, fracture characteristics, and balloon shape. The endpoint of balloon inflation is achieved when any of the following occurrences are seen: fracture reduction achieved, maximum inflation volume reached, maximum sustained balloon pressure achieved, cortical wall contact, or adequate cavity creation performed. The maximum balloon volume and balloon pressure will vary according to the balloon type and manufacturer.

After a void is created and height restoration is achieved as safely permitted, the bone tamps are removed and internal fixation is achieved through a low-pressure injection of bone void filler (▶Fig. 6.8). After the cavity is filled and there is adequate interdigitation of cement into the interstices of the surrounding cancellous bone, the cannulas are removed.

Related posts:

4 Physical Examination Findings in Patients with Vertebral Compression Fractures 10 Cervical and Posterior Arch Augmentation 14 Appropriateness Criteria for Vertebral Augmentation 18 Predisposing Factors to Vertebral Fractures 23 Number of Levels Appropriately Treated with Vertebral Augmentation 30 Vertebral Augmentation in Instrumented Spinal Fusions

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