Introduction

Traditionally, vertebral augmentation (VA) has been one of the safest interventional spine procedures done with the heretofore largest VA registry reporting only two adverse events and the largest post-market VA Kyphoplasty (KP) trial done to date, reporting no persistently symptomatic adverse events (AEs) [1, 2]. Despite the excellent record of safety with all forms of VA including vertebroplasty (VP), kyphoplasty (KP), and vertebral augmentation with implants (VAI), more serious complications have also been reported including osteomyelitis, epidural hematoma, injuries to the nerve roots and spinal cord, systemic cement toxicity and venous and pulmonary embolization.

The vast majority of VA cases involve treating patients with osteoporotic vertebral compression fractures (VCFs) and this patient population is typically fragile with multiple co-morbidities [3]. Patients with painful VCFs are also known to have increased mortality that can range up to eight to nine times aged matched controls so, when treating these patients and selecting the type of treatment to apply, it should be taken into consideration that non-surgical management (NSM) also has risks associated with it and those risks should always be balanced with the risks of the procedure itself [4]. A recent claims-based analysis by Ong et al., showed that kyphoplasty conferred a 55% 1-year mortality benefit and reduced patients’ 10-year mortality risk by 24% compared to NSM [4]. Another meta-analysis of 16 manuscripts by Hinde et al., showed a 10-year mortality reduction of 22% for patients with VCFs treated with VA as compared to those patients treated with NSM [5]. In addition to a mortality decrease, it can significantly decrease morbidities [6] and it has been shown to prolong life between 2.2 and 7.3 years per patient [7]. Knowledge of what happens to patients with painful VCFs, according to what type of treatment they receive, helps to stratify risk and contributes to making a decision that will optimize the combination of greatest amount of treatment benefit with least amount of risk.

The anatomy of the vertebral body and the pathologic process affecting it will determine the most common complications related to cement extravasation. In an intact vertebral body, the most common pathway of egress outside of the vertebral body is through the basivertebral plexus and paravertebral veins which can produce narrowing of the spinal canal and pulmonary embolism respectively [8] and a fractured end plate will predispose to extravasation into the adjacent intervertebral disc that can increase the risk of adjacent level fracture [9]. The anatomic level of the vertebrae being treated is also important as to the type of complication and the risk of severe adverse events. An extravasation into the canal at a thoracic level can more readily lead to catastrophic neural compression as the spinal cord is located at these spinal levels as compared to the lumbar level that is mostly adjacent to the cauda equina which is less easily compressed. A sacral insufficiency fracture is very different from the thoracic and lumbar levels as it does not have a basivertebral plexus located in the ala where fractures commonly occur and the most critical neural structures are located anterior and medial to the vertebrae being treated (the lumbosacral plexus and the sacral nerve roots respectively) rather than posterior to the vertebral body.

Indications and contraindications for vertebral augmentation have changed over time with more recent indications being fewer in number and with a pattern of being cumulative [10]. This means the greater the number of negative impact indications there are, the more appropriate the indications for VA become [10]. Contraindications for VA can be divided into absolute and relative contraindications with the vast majority being relative contraindications, leaving the decision to treat up to the clinician according to the specific scenario.

The approach to the vertebral body varies according to the level and the pathology affecting it but the three general approaches can be divided into transpedicular, parapedicular and extrapedicular [11–13]. The transpedicular approach was the most common early approach and was described for vertebral body biopsies [11] and for vertebroplasty [14]. Although the first vertebroplasty ever reported utilized a transoral anterior approach to treat a hemangioma of the C2 vertebral body [15], most of the approaches outside the pedicle have primarily been used for more recent vertebral augmentation procedures [12, 13].

Complications associated with vertebral augmentation have previously been classified as rare [16]. The adverse events associated with VA are mostly related to extravasation of bone cement (polymethylmethacrylate or PMMA). The vast majorities of extravasations are clinically unimportant and asymptomatic and should be separated from symptomatic complications as they don’t have any clinical implications regarding patient well being or need for future treatment. Extravasation of cement is one of the primary reasons VA is performed under fluoroscopy and patterns of cement extravasation are important to recognize as some extravasation routes are much more likely to produce complications than others [17].

Anatomy of the Vertebral Body

When performing VA, the anatomic considerations of the vertebral body should be taken into consideration. Depending on the anatomy of the fracture or neoplastic involvement, the most optimal choice for the approach should be the one to achieve the goal of restoring the native anatomy of the vertebral body as much as possible while forming an intrabody strut with the PMMA which is ideally placed between the pedicles in the center of the vertebral body (VB) from the superior end plate to the inferior end plate (Figure 38.1a,b).

The three general categories of approaches to the vertebral body are transpedicular, parapedicular, and extra-pedicular and one approach is usually selected over the other based on whether there is unfettered access to the appropriate portions of the VB. For example, if a patient has a VCF in a vertebral body that has pedicle screws, a para- or extra-pedicular approach should be chosen as the transpedicular route to the VB will be blocked or substantially impeded by the pedicle screws (Figure 38.2a–c).

Each approach will have its advantages to accessing the vertebrae, but each will also be associated with its own set of possible complications. The transpedicular approach can fracture the pedicle if too much shear force is applied via the needle insertion or by moving the needle once in place (Figure 38.3).

The parapedicular approach has a more lateral starting point and can fracture the transverse process if the needle tip is too inferior to pass over the transverse process. An extra-pedicular approach is very safe on the approach to the vertebral body as the target is just anterior to the pedicle, just superior to the inferior end plate and posterior to the anterior vertebral cortex. This approach does not have osseous structures in the pathway to the VB that may be injured but the patterns of extravasation can be different from the steeper approaches, and this should be kept in mind while filling the vertebral body so as to avoid unusual cement extravasations near the neural structures (Figure 38.4a,b).

In contradiction to the vertebrae in the thoracic and lumbar spine, the cervical vertebrae are accessed from a different direction. Instead of posterior or posterolaterally to anterior, the cervical vertebrae are typically accessed from anterior or anterolateral to posterior. The vertebral bodies from C3 to C7 are usually accessed from the anterolateral position in between the larynx and the carotid artery by displacing these structures manually prior to placing the needle. The needle is then inserted through the skin and into the cervical VB prior to inflating a balloon or injecting cement (Figure 38.5a,b).

The C2 vertebral body is either accessed posterolaterally or, more commonly, through the transoral approach (Figure 38.6a ,b).

The most important location to watch for extravasation is into the spinal canal and neural foramina of the cervical spine and, given the anatomy and the presence of less soft tissue to penetrate with fluoroscopy, this anatomic segment is typically easier to identify extravasation into an untoward location (Figure 38.7a,b).

The sacrum is a commonly fractured vertebral segment, but the most common fractures occur in the ala of the sacrum rather than in the vertebral body (Figure 38.8).

When performing sacral augmentation, the sacral ala are the structures typically augmented with bone cement. The ala do not have a basivertebral plexus such as the lumbar or thoracic VBs so extravasation into the canal is not common but can occur. The greatest risk of extravasation into the central spinal canal occurs with augmentation of the sacral body (Figure 38.9a,b).

The most common areas of extravasation that can lead to injury when performing sacroplasty are into the neural foramina or anterior to the sacral ala in the location of the lumbosacral plexus (Figure 38.10). The plexus can be displaced and stretched anteriorly leading to injury with permanent neurologic damage.

Indications and Contraindications to Vertebral Augmentation

No chapter on the complications of a procedure would be complete without reasons to do or not do the particular type of procedure being discussed. Overall, the indication for VA is a painful fracture of the vertebral body resulting from osteoporosis, neoplastic involvement or trauma. Osteoporotic fractures are the most common type of fracture being approximately 20 times more common than traumatic fractures and over six times more common than neoplastic fractures [18–22]. The indications should be taken into consideration along with additional guidance on the appropriateness of VA vs. that of NSM. This has been examined as part of a multidisciplinary appropriateness exercise using standard methodology [10] (Table 38.1).

In general, there is consensus agreement that painful vertebral fractures should be treated regardless of the fracture age. If the fracture is identified on advanced imaging findings and has typical characteristics such as increased signal on fluid-sensitive MR images or anatomic evidence of fracture on CT, then the fracture is eligible for treatment provided it has a sufficiently adverse effect on the patient’s activities of daily life. Additionally, the greater the degree of VB height loss and kyphotic deformity, especially when there is a progression of the anatomic deformity, the greater the need for VA. The evolution of the patients’ symptoms is probably the most important factor that determines the timing of the treatment and whether the patient is treated with VA or not. In patients who have mild symptoms, or who are improving over time, the treatment of choice would typically be NSM whereas patients who have severe symptoms or are worsening over time are usually treated with VA regardless of the length of time the fracture has been present.

The contraindications to VA (Table 38.2) should be divided into absolute and relative contraindications as not every contraindication should disallow the procedure. The only absolute contraindications agreed on by a multidisciplinary group of experts are an active infection at the surgical site and/or an untreated blood-borne infection. Vertebral augmentation should not proceed in the presence of these diagnoses unless the patient has been treated preoperatively with parenteral antibiotics in the case of a blood-borne infection. A strong, but not absolute, contraindication is the presence of osteomyelitis. In unusual circumstances, it may be deemed acceptable to proceed with VA and persistent suppression antibiotic therapy in patients with few or no other options. There are numerous relative contraindications to VA such as pregnancy, allergy to the fill material, coagulopathies, spinal instability, myelopathy, neurologic deficit and the presence of neural impingement. These relative contraindications should be handled on a case-by-case basis as some of these contraindications are easily dealt with (i.e., using another type of fill material in patients with an allergy to one type) while others are not (i.e., spinal instability). One of the traditional contraindications, fracture retropulsion, is currently thought not to be a contraindication, but it is also considered able to be improved with VA that maximizes fracture reduction and pulls the retropulsed fracture forward via ligamentotaxis of the posterior longitudinal ligament (Figure 38.11a,b).

Technique and the Most Common Approaches for Vertebral Augmentation

The traditional approach to the vertebral body is the transpedicular approach. The first percutaneous biopsy of the vertebral body was described in 1934 by Ball [23] and the transpedicular approach was first described in 1963 and was re-emphasized in 1983 by Dr. Roy-Camille who was working at the Raymond Poincaré Hospital in Garches as the assistant to Dr. Robert Judet [24]. The approach gained substantial popularity following this report and has a proven utilization record for its usefulness and low complication rate [25]. The transpedicular route is the most commonly used approach for vertebral augmentation [26].

The transpedicular approach is based on the upper outer portion of the pedicle with these locations identified as the 10 o’clock and 2 o’clock positions of the left and right pedicles respectively. The starting point is one centimeter superior and two centimeters lateral to the upper outer portion of the pedicle (Figure 38.12a).

An incision is placed at this point and the needle is placed at an angle 30° from the direct vertical and the needle directed to the upper outer portion of the ipsilateral pedicle until bone is encountered. The needle is advanced with a mallet until the tip of the needle is immediately adjacent to the medial wall of the pedicle on the anteroposterior view (Figure 38.12b). A lateral view is then obtained to ensure that the needle tip is anterior to the posterior wall of the vertebral body (Figure 38.12c). When this appearance is confirmed, the clinician performing the procedure can rest assured that the spinal canal has not been violated and there is little to no chance of neurologic injury.

The parapedicular approach is an alternative to the transpedicular approach. This approach begins in a more lateral location and creates a more favorable needle trajectory that can allow for a more predictable approach to the center of the vertebral body. As with any approach to the vertebral body, potential complications include nerve root injury, hematoma, and injury to other organs although injuries like these are rare and the parapedicular approach has been shown to be consistent and safe [12].

The parapedicular approach starting point is one vertebral body width from the ipsilateral superior vertebral body on a line from the contralateral inferior vertebral body to the ipsilateral superior vertebral body (Figure 38.13a). A 30° ipsilateral oblique is obtained to make sure the entry point is just anterior to the pedicle and just above the middle of the pedicle (Figure 38.13b). As the needle is advanced into the VB, care is taken not to cross the medial wall of the pedicle prior to the needle tip entering the posterior portion of the vertebral body. As with the transpedicular approach, this will ensure the osseous structures surrounding the spinal canal are not violated.

There are various extra-pedicular approaches but the most commonly utilized approach for VA is the relatively recently described modified inferior end-plate extra-pedicular approach [13]. This approach has all the potential complications of the other approaches but an additional possible clinical complication when performing this approach that is more lateral than the parapedicular body approach is a pneumothorax or pleural tear when accessing the thoracic vertebral bodies. Despite this, and other possible complications, the modified inferior end-plate extra-pedicular approach has been shown to be very safe and not associated with any significant complications [13].

The modified inferior end-plate extra-pedicular approach accesses the lumbar vertebral bodies at 45° off the midline and at 30° for the thoracic vertebral bodies. The target is just anterior to the pedicle and below the midline of the vertebral body (Figure 38.14).

The starting point is usually lateral to the paraspinal musculature so the needle will need to be stabilized with a surgical clamp as the needle is advanced under fluoroscopy. The entry point to the vertebral body is not nearly as robust as the osseous structures encountered during the transpedicular and parapedicular approaches and, in very osteoporotic patients, it may be difficult to determine when the osseous tissue is encountered.

Complications of Vertebral Augmentation vs. the Complications of Treatment with Non-Surgical Management

When considering treatments for patients with painful VCFs, remember to consider the risks for the NSM patient as well as the patient who would undergo VA. The primary consideration with these patients is that NSM is not risk-free therapy [27]. The strategy of bedrest and limiting the patients’ activities of daily life can be counterproductive in the elderly population, especially when combined with opioid therapy which is especially problematic for this patient population [28]. An example of this is seen in the safety and efficacy of vertebroplasty for acute painful osteoporotic fractures (VAPOUR) trial where the NSM patient cohort had more significant adverse events than the vertebroplasty cohort including a patient paralysis due to progressive collapse of a vertebral body two weeks after the patient was enrolled in the trial [29].

There is elevated mortality risk in patients with painful VCFs and the relative rate of mortality has been shown to be as high as 8.6 times age-matched controls as was seen in the fracture intervention trial [4]. Even in the absence of a painful vertebral compression fracture, there is an elevated mortality risk for geriatric patients with kyphotic posture as has been seen in a prospective trial of more than 1300 patients [30].

Claims-based data analysis has repeatedly demonstrated mortality advantages of VA over NSM and of kyphoplasty over vertebroplasty and many manuscripts have reported significant reductions in mortality in many countries including the United States, Germany, South Korea, China, Sweden, and Taiwan [6, 31–33, 33–38]. Ong et al. and Edidin et al. noted 55% mortality advantages over NSM at one year in separate analyses [6, 31] and recent meta-analysis noted a 10-year mortality benefit of 22% for those patients undergoing VA vs. those undergoing treatment with NSM [5

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