Vertebral Augmentation: The Comprehensive Guide to Vertebroplasty, Kyphoplasty, and Implant Augmentation

11 Balloon Kyphoplasty

James Mooney, John W. Amburgy, D. Mitchell Self, Leah J. Schoel, and M.R. Chambers

Summary

Balloon kyphoplasty is a minimally invasive vertebral augmentation procedure used to treat painful vertebral compression fractures. The goal of any vertebral augmentation procedure is pain reduction, stabilization of the fracture, and improvement in patient function. Unique to balloon kyphoplasty is restoration of vertebral body height and reduction of kyphotic angulation through the use of inflatable bone tamps. In addition, the balloon tamps reduce the risk of cement leakage by facilitating an injection that follows the path of least resistance into and around the cavity created by the balloon. In this chapter, the diagnostic criteria, techniques, indications, and contraindications are discussed. Materials, equipment, imaging, and the procedure itself are described in detail. In addition, the importance of sagittal balance restoration and realignment is addressed as it relates to the risk of adjacent fractures. The risks and benefits of balloon kyphoplasty are summarized.

Keywords: balloon kyphoplasty, vertebral augmentation, vertebral compression fracture, bone cement, vertebral height, kyphotic angulation, sagittal balance, minimally invasive

11.1 Introduction

Vertebral augmentation is a category of surgical procedures used to treat vertebral fractures and includes vertebroplasty, kyphoplasty, and implants. The goal of any vertebral augmentation procedure is the minimally invasive reduction and stabilization of a painful vertebral compression fracture (VCF). Unique to balloon kyphoplasty is restoration of vertebral body height and reduction of kyphotic angulation through the use of inflatable bone tamps. The balloon tamps reduce the risk of cement leakage by facilitating an injection that follows the path of least resistance into and around the cavity created by the balloon.

11.2 Materials

The surgical equipment is available through numerous sources. A comprehensive list of manufacturers, materials, and equipment for kyphoplasty can be found in ▶Table 11.1. Components available from Medtronic Kyphon are listed in the following sections and shown in ▶Fig. 11.1.

Fig. 11.1 Kyphon Balloon Kyphoplasty devices. (a) Kyphon Osteo Introducers (Diamond introducer, Bevel introducer, and drill shown). (b) Kyphon inflatable bone tamps. (c) Kyphon inflation syringe. (d) Kyphon cement delivery system. (e) Kyphon Latitude II Curette.

Table 11.1 Providers of materials and equipment for balloon kyphoplasty

Balloon kyphoplasty

Ackermann

Alphatec Spine

BM Korea

BPB Medico

Biopsybell

Depuy Synthes

G-21

iMedicom

KMC-Maxxspine

Medtronic (Kyphon)

Osseon

Panmed US

Rontis

Taeyeon

Synimed

11.2.1 Bone Access Tools

• Jamshidi-style needle: Typically, an 11- or 13-gauge cannulated needle used to gain access to the vertebral body via the pedicle or a peripedicular approach. The internal stylet may have a variety of bevel tips for increased penetration capability or for directional control. Once in position, the inner trocar is removed.

• Kirschner’s wire (K-wire): It is placed in the cannula, which is then removed for a Seldinger-technique establishment of the working channel.

• Osteointroducer: An 8- or 10-gauge cannulated introducer or working channel is placed over the K-wire, which is then removed. The osteointroducer may be beveled for directional control.

• Drill: It is used to cut and channel through cancellous bone for placement of the balloon.

• Curette: It is used to expand the cavity created by the drill to accommodate the expansion of the balloon.

11.2.2 Balloons Tamps and Inflation Devices

• Inflatable bone tamps: These are available for use with 8- and 10-gauge introducers in three lengths (10, 15, and 20 mm) with volumes ranging from 3 to 6 mL and pressure ratings ranging from 300 to 700 psi.

• Inflation device: It has a manometer with a digital pressure gauge for controlled inflation.

• Cement delivery cannulas: It is an 8- or 10-gauge coaxial delivery system with an outer cannula and an inner rod or “pusher” for expelling cement.

11.2.3 Bone Cement

Acrylic bone cement (ABC) is the most commonly used cement for vertebral augmentation. The main components of ABC are solid and liquid acrylic compounds that cure rapidly when mixed at room temperature and even faster when exposed to body temperature. A number of brands are commercially available. Disadvantages of using ABC include nonbiodegradability and significant mechanical mismatch with the osseous components of the vertebral body.¹ Efforts have been made to improve the mechanical characteristics, porosity, and biodegradability of the products. Polymethyl methacrylate (PMMA) is the most popular bone cement. A modern version of PMMA was first used in the United Kingdom by Dr. John Charnley in total hip replacement surgery² and was Food and Drug Administration (FDA) approved for treating VCFs in 2004.

In 2017, calcium phosphate cement (CPC) was redesigned by incorporating starch and BaSO₄ to create a new cement. Biomechanical strengths measured by in vitro and in vivo models were not less than that of PMMA, while its biodegradability and osseointegrative capacities were significantly enhanced compared to PMMA.

Other less commonly used bone cements include CPC, calcium sulfate cement (CSC), and magnesium phosphate cement (MPC). Chapter 7 provides a detailed discussion of the various cements and fill materials.

11.3 Diagnosis and Preoperative Preparation

A patient with an acute or subacute vertebral body compression fracture will almost always complain of severe back pain. Physical examination will reveal tenderness to palpation and percussion over the corresponding spinous process. Subsequent radiographs, CT, MR, and/or nuclear bone scan imaging are used to confirm and characterize a fracture. Short tau inversion recovery (STIR) and T1-weighted sequences on MR imaging are considered the gold standard for evaluating VCFs. There is a high degree of correlation between increased STIR signal and a pain-generating fracture and the T1-weighted images well demonstrate fracture lines and marrow signal changes (▶Fig. 11.2). If MR imaging is not possible, nuclear bone scan imaging may be used to demonstrate radionuclide uptake in an acute or subacute fracture and can be used in combination with CT scanning for accurate anatomic characterization of the fracture.

Patients undergoing kyphoplasty are often elderly, are deconditioned, and have inherent vulnerability to perioperative stress. For example, inhalation agents are affected by the minimum alveolar anesthetic concentration, which decreases approximately 6% for every decade. Clearance and the volume of the central compartment decrease with age. Metabolism of medications and their durations of action depend on renal or hepatic excretion. It is important to titrate doses and prudent to use short-acting drugs. Preoperative assessment of organ function and reserve is essential to know how the patient might react with anesthesia.³ Although preoperative laboratory studies and testing will vary from patient to patient, we routinely include CBC with differential, chemistries, coagulation studies, anteroposterior (AP) chest radiograph, and an ECG.

Fig. 11.2 Sagittal (a) T1 turbo spin echo (TSE), (b) T2 TSE, and (c) T2 short tau inversion recovery (STIR) images of an acute L1 vertebral compression fracture (white arrows). Bone marrow edema is hypointense on T1-weighted and hyperintense on T2 STIR images. (These images are provided courtesy of Dr. M. R. Chambers).

11.4 Indications and Contraindications

Indications for kyphoplasty include intractable severe pain or moderate to severe persistent pain associated and correlating with a VCF. In 2017, a multidisciplinary expert panel of orthopaedic and neurosurgeons, interventional radiologists, and pain specialists, using the RAND/UCLA Appropriateness Method (RUAM), developed the Clinical Care Pathway (CCP), defining patient-specific recommendations for vertebral fragility fractures (VFF). The panel assessed the relative importance of signs and symptoms for the suspicion of VFF, the relevance of diagnostic procedures, and the appropriateness of vertebral augmentation versus nonsurgical management for a variety of clinical scenarios (▶Fig. 11.3). Their report included the following guidelines for relative and absolute contraindications (▶Table 11.2).

Absolute contraindications include active infection at the surgical site and untreated blood-borne infections. Strong contraindications include osteomyelitis, pregnancy, allergy to fill material, coagulopathy, spinal instability, myelopathy from the fracture, neurologic deficit, and neural impingement. Although dependent on degree, fracture repulsion and canal compromise are not generally a contraindication. Relative contraindications include cardiorespiratory compromise such that safe sedation or anesthesia cannot be achieved and in such cases the procedure may need to be done under local anesthesia. Breach of posterior vertebral cortex by tumor and tumor extension into the spinal canal are also relative contraindications for percutaneous vertebral augmentation techniques due to the potential for leakage of cement and/or displacement of tumor posteriorly.

11.5 Procedure

Kyphoplasty may be performed under general anesthesia or monitored anesthesia care (MAC) with conscious sedation and local anesthetic. In our practice, with rare exceptions, we perform kyphoplasty under general endotracheal anesthesia. In patients who cannot tolerate general anesthesia due to severe cardiopulmonary disease, for example, sedation with MAC is used with caution to avoid oversedation and respiratory compromise.

The patient is positioned prone on the operating table with shoulder and hip bolsters to aid in spinal extension and vertebral height restoration. All pressure points are padded and checked. With fluoroscopic guidance for localization, the area of planned surgery is prepped and draped in the usual sterile fashion. Appropriate prophylactic antibiotics are administered. Fluoroscopy is used to identify the pedicles and fractured vertebral body. Fluoroscopic views include true AP and lateral views. Another technique includes the en face view, directed down the longitudinal axis of the pedicle (▶Fig. 11.4).

Fig. 11.3 The clinical care pathway (CCP) for the management of vertebral compression fractures.

Table 11.2 Absolute and relative contraindications for kyphoplasty

Condition	Panel recommendation
Active infection at surgical site	Absolute contraindication for curent vertebral augmentation (VA).
Untreated blood-borne infection	Absolute contraindication. Preoperative antibiotic (parenteral) therapy is required. Once cultures are negative, following an appropriate period of antibiotic therapy, one can proceed with caution.
Osteomyelitis	Usually a strong contraindication for VA. In rare situations, VA may be considered, for example, if the patient is not stable for an open procedure and the infection is chronic and caused by a less virulent organism. The infection may then be controlled locally with antibiotic-loaded cement and long-term antibiotic suppression.
Pregnancy	Although VA is usually contraindicated in pregnant patients, there may be exceptional situations in which benefits could prevail over risks. Radiation exposure to the fetus should be minimized.
Allergy to fill material	Relative contraindication, depending on the severity of the allergy. If prior reactions were not associated with severe anaphylaxis, the allergy can be pretreated with steroids, Tylenol, and Benadryl. Alternatively, another fill material can be chosen.
Coagulopathy	Relative contraindication. Try to normalize/correct clotting function if possible (international normalized ratio [INR] < 1.7). The risk of bleeding should be balanced against the complications from bed rest. Caution in patients with thrombocytopenia (platelets less than 30,000/μL).
Spinal instability	Relative contraindication, depending on the degree of instability and level of fracture. If needed, plan an additional intervention to address instability, possibly but not necessarily in the same session.
Myelopathy from the fracture	Relative contraindication. Decompression and stabilization is the preferred option, but VA may be considered if the patient is unable to undergo surgery. Coordination with spine surgeon and neurologist is mandatory.
Neurologic deficit	Relative contraindication. Additional decompression with or without stabilization may be required. Patients should be informed about the risk of cement in the spinal canal. Coordination with spine surgeon and neurologist is mandatory.
Neural impingement	Relative contraindication, depending on the degree. Take extra care to avoid delivery of cement into canal or neural foramen. May need an additional open procedure.
Fracture retropulsion/canal compromise	Generally not a contraindication. Avoid hyperextension or aggravating stenosis. A CT scan may be used to determine integrity of posterior wall.

Fig. 11.4 (a) Proper positioning of patient and anteroposterior and lateral fluoroscopy for kyphoplasty procedure. (Source: Kim CW, Garfin SR. Percutaneous cement augmentation techniques [vertebroplasty, kyphoplasty]. In: Vaccaro AR, Albert TJ. Spine Surgery: Tricks of the Trade. New York, NY: Thieme; 2009:250–254.) (b) The en face view provides an angle directly down the axis of the pedicle. (Source: Resnick DK, Barr JD, and Garfin SR. Vertebroplasty and Kyphoplasty. 1st ed. New York, NY: Thieme Publishers; 2005.) (c) Fluoroscopic view: 20-degree ipsilateral right-sided oblique; starting position on the upper outer pedicle (white circle).

Local anesthetic is injected and a small stab incision is made with a no. 15 or a no. 11 blade approximately 1 cm superior and 2 cm lateral to the superior pedicle border. For a standard transpedicular approach, the Jamshidi needle is inserted and guided under direct fluoroscopy through the pedicle into the vertebral body. Other approaches and access techniques may also be used (see Chapter 6). The inner cannula is removed and replaced with a K-wire. Using the Seldinger technique, the Jamshidi cannula is removed and the cannulated osteointroducer is passed over the K-wire and advanced through two-thirds of the AP vertebral body diameter. The K-wire and inner cannula are removed when the outer cannula position is confirmed. The drill is passed manually with fluoroscopic guidance to create a void for the bone tamp and to obtain biopsy material for pathology. Core bone biopsies may be obtained through the introducer or a biopsy cannula (▶Fig. 11.1).

Next, a 10- or 15-mm bone tamp connected to a syringe prefilled with iodinated contrast is inserted through the cannula and, under direct fluoroscopic guidance, guided into the tract created by the drill. The radiopaque markers on the balloon tamp are visualized distal to the cannula sheath in both AP and lateral fluoroscopic images. When a bilateral approach is used, this procedure is repeated identically on the contralateral side.

The use of balloon tamps allows for safe and gentle end plate reduction, displacement of trabecular bone, and the creation of a void. The balloon tamps are incrementally inflated while being monitored with AP and lateral imaging. Digital manometers incorporated into the inflation devices demonstrate increases in pressure with each increase in volume. The pressure then gradually diminishes as the trabecular bone is displaced. This process is repeated as safely tolerated. Fracture reduction is guided by the degree of end plate distraction, height restoration, and reduction of kyphotic angulation. Pressure, volume, and fluoroscopic images will all dictate an endpoint. There should be no breach of lateral wall or anterior cortex of the vertebral body. The final balloon volume is recorded and one or both tamps are deflated and removed. The cement-delivery cannula is inserted through the working channel and advanced until the tip of the cannula reaches the anterior extent of the void created by the tamp, preferably just posterior to the anterior cortical wall of the vertebral body. The rod is used to expel cement from the cannula. As cement is delivered, the cannula and rod are retracted gently to allow room for the cement to fill the void. As the cement extends posteriorly, the injection should be slow to watch for extravasation. The cement should extend from superior to inferior end plate and be located between the pedicles. The cement can extend up to the posterior vertebral body wall, but it is important to watch for and recognize extension of cement beyond this margin. This process is repeated on each side until an adequate fill is achieved. As the cement begins to harden, the cannulas are removed. The internal fixation and stabilization of the vertebrae is achieved through the hardening of the cement injected into the vertebral body. Final fluoroscopic images are taken to document the final cement position. Wounds are dressed with Dermabond or Steri-Strips (▶Fig. 11.5).

11.5.1 Bilateral versus Unilateral Approach

Several large systematic reviews of randomized control trials have examined the difference between bilateral and unilateral approaches for kyphoplasty. Some differences were observed between the two approaches in terms of height restoration, correction of kyphotic angulation, and patient ratings of pain.⁴^,⁵

In an analysis of 15 randomized control trials including 850 patients, Yang et al found no difference in quality-of-life or complications from surgery between bilateral and unilateral kyphoplasty.⁴ Chen et al found that the unilateral approach resulted in a shorter operative time, smaller amount of cement injected, and lower risk of cement leakage.⁵ There were no statistically significant differences in visual analog scale pain scores, height changes, or kyphotic angle changes between the groups.⁵ Papanastassiou et al examined the differences between unilateral and bilateral kyphoplasty in multiple myeloma patients and found no difference in clinical or radiological outcomes.⁶ Huang et al in a review of five studies including 253 patients found no clinically important differences but suggested that unilateral kyphoplasty is advantageous due to decreased operative time and cost.⁷ Similarly, in a systematic review and meta-analysis including 563 patients, Sun et al noted that unilateral approach led to decreased surgical time, cement consumption, and cement leakage; reduced radiation dose and hospitalization costs; and improved short-term general health.⁸

There are also substantial data supporting the bilateral approach for optimal outcomes in vertebral augmentation with balloon kyphoplasty. In a retrospective study of 296 patients with osteoporotic VCFs, Bozkurt et al showed that although there was no statistically significant difference between unilateral kyphoplasty and vertebroplasty regarding height restoration of the fractured vertebral body, there was a further advantage of significant height restoration of bilateral kyphoplasty compared to the other two techniques.⁹ 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 that indicated bilateral balloon kyphoplasty had a significantly (p = 0.03) better degree of anterior vertebral height restoration than unilateral balloon kyphoplasty.¹⁰

Fig. 11.5 Pre- and postoperative images demonstrating cement filling and height restoration after kyphoplasty of an L1 compression fracture. Measurements are made at three points from posterior (measurement on a) to anterior (measurement on b). The height of the three points of the vertebral body is listed in millimeters. (These images are provided courtesy of Dr. M. R. Chambers.)

In general, based on the above studies and analyses, a unilateral approach provides an advantage regarding procedure time, procedure and hospital costs, radiation dose, and improved short-term health and cement extravasation. Additionally, there appears to be no significant difference in the unilateral versus bilateral approach with respect to pain reduction, quality-of-life improvement, or procedural complications. Finally, balloon kyphoplasty using a bilateral approach has been shown to provide significantly better short-term height restoration than the same procedure performed via a unilateral approach.

11.6 Risks and Benefits

As with any surgical procedure, possible adverse events include infection, hemorrhage, cardiac arrest, and stroke. Other risks specific to kyphoplasty include cement leakage and emboli, spinal cord compression, and nerve injury. Risks related to balloon failure are generally minimal. With failure or rupture of the balloon, pressure will rapidly drop to or near zero and a small amount of contrast medium and saline escape. The balloon may be gently removed after deflation. Fortunately, the complication rate for kyphoplasty is very low and this procedure has been shown to lead to significant and sustained reduction of pain, disability, and opioid analgesic usage, which results in a significantly improved quality of life.¹¹^–¹⁶

11.7 Importance of Sagittal Balance Restoration and Kyphosis Correction

The physical consequences of vertebral deformity, sagittal imbalance, and kyphosis include reduced pulmonary function, early satiety and gastric distress, difficulty with balance, postural compensation with altered gait and reduced velocity, chronic back pain, reduced activity and function, increased fracture risk independent of bone mineral density, and increased mortality.⁹^,¹⁰^,¹⁷^–²⁸

Sagittal balance is recognized as an important factor in determining outcomes following spine surgery and is included in the radiographic assessment of spinal deformity.²⁹^–³² Many patients with VCFs present with sagittal imbalance due to the kyphosis caused by the compression fracture itself. Sagittal balance is determined with respect to a plumb line drawn from the middle of the C7 vertebral body. In normal sagittal balance, the line will pass through a point at the posterosuperior aspect of the S1 vertebral body. A patient is in positive balance if the line passes greater than 2 cm anterior to this point and in negative balance if the line passes greater than 2cm posterior to the same point (▶Fig. 11.6).

Few studies have directly examined the relationship between kyphoplasty and sagittal vertical axis (SVA) correction. Pradhan et al retrospectively reviewed 65 patients undergoing level 1 to 3 kyphoplasty procedures to examine the effects of single and multilevel kyphoplasty on local and overall sagittal alignment of the spine. The authors found that the majority of kyphosis correction by kyphoplasty was limited to the vertebral body treated and that correction over longer spans with multilevel kyphoplasties could achieve improved sagittal balance.³³ In a study of 21 patients who underwent kyphoplasty, Yokoyama et al found that the preoperative SVA was 7 ± 3.9 cm, demonstrating a significant shift to anterior (positive) sagittal balance as compared to a healthy group that measured 1.45 ± 2.7 cm. After kyphoplasty, the SVA decreased to 5.02 ± 2.91 and this decrease correlated with the kyphotic reduction of the treated vertebrae.³⁴

Fig. 11.6 Sagittal balance is determined by the C7 plumb line, which is a vertical line drawn from the center of the C7 vertebral body. Positive sagittal balance occurs when this line falls greater than 2 cm anterior to the posterosuperior corner of S1. Negative sagittal balance occurs when the line falls greater than 2 cm posterior to this point. (Source: Dickson R, Harms J, eds. Pathogenesis. In: Modern Management of Spinal Deformities: A Theoretical, Practical, and Evidence-Based Text. 1st ed. New York, NY: Thieme; 2018.)

Fig. 11.7 (a, b) Postoperative images following a three-level kyphoplasty procedure. (Source: Resnick DK, Barr JD, and Garfin SR. Vertebroplasty and Kyphoplasty. 1st ed. New York, NY: Thieme Publishers; 2005.)

Reports examining the correlation between restoration of sagittal balance alignment and clinical outcome parameters have been mixed. Several studies have shown that improvements in sagittal balance after kyphoplasty are correlated with surgical outcomes involving pain and quality-of-life scores.³⁵^–³⁷ Particularly in patients with adult degenerative spinal deformity, correlations between sagittal balance correction and surgical outcomes have been strong. However, other studies have demonstrated no relationship between sagittal balance alignment restoration and clinical outcome parameters.³⁸^–⁴² The FREE trial, a randomized, nonblinded trail comparing kyphoplasty with nonsurgical management of acute painful vertebral fractures, reported that patients with the greatest quality-of-life improvement, based on the SF-36 PCS (physical component summary) scores, had the better kyphosis correction (5.18 degrees) compared with the subgroup having the least quality-of-life improvement (1.98 degrees of angulation correction). Similarly, patients with the highest kyphotic angulation correction had higher SF-36 PCS quality-of-life improvement.³⁵

11.8 Adjacent Fractures

Additional fractures have been reported following vertebral augmentation procedures, but the causal relationship between the procedures and subsequent adjacent vertebral fractures is doubtful as patients with osteoporosis who do not undergo surgery also develop additional fractures.⁴³^–⁵³ A fracture rate above that of the natural history of osteoporosis has not been demonstrated. Additional fractures occur more quickly in patients who have undergone augmentation as compared to those who have not. This may explain the perception that augmented patients fracture more often (▶Fig. 11.7).²⁰^,⁵⁴^–⁵⁶

Regardless of bone mineral density, age, and other clinical risk factors, vertebral fractures confirmed radiographically—even if asymptomatic—signal-impaired bone quality and strongly predict new vertebral and other nonvertebral fractures. The presence of a single vertebral fracture increases the risk of subsequent vertebral fractures fivefold and the risk of hip and other fractures twofold to threefold.⁵⁷ Following an initial fracture, osteoporotic patients not treated with systemic antiosteoporosis therapy develop an additional fracture at twice the rate (20%) of those on antiresorptive medication and even fewer vertebral fractures are seen in patients receiving anabolic bone agents with dramatic absolute and relative risk reductions of 3.6 and 86%, respectively.⁵²^,⁵⁵^,⁵⁸^,⁵⁹

Vertebral augmentation may serve to decrease additional or adjacent-level fractures. Numerous studies have demonstrated a lower incidence of adjacent fractures in patients treated with kyphoplasty (4.2%), compared to published rates in untreated patients with osteoporotic fractures (20%).¹⁵ In retrospectively analyzing 240 patients with painful VCFs, Baek et al found that risk for adjacent-level fractures after vertebral augmentation decreased significantly when the SVA was less than 6 cm and the segmental kyphotic angle was less than 11 degrees.⁶⁰ In a matched prospective study, Palombaro reported a 6-month adjacent fracture rate of 37% in patients treated with balloon kyphoplasty and 65% in nonsurgically treated patients.⁶¹

Kyphosis resulting from a wedge-shaped fracture shifts the center of gravity of the upper body forward. This increases the flexion bending moment and leads to a compensatory stance with hamstrings foreshortened (knees bent) and paraspinal muscle activity increased in the effort to maintain balance. In a finite element study, Rohlmann et al measured intradiskal pressure (IDP) in the disks adjacent to a fractured vertebra before and after augmentation. The elastic modulus of PMMA varied between 1,000 and 3,000 MPa and the volume between 4 and 10 mL. The effects of volume and elastic modulus of bone cement on IDP were negligible. Augmentation of the fractured vertebral body with bone cement had a much smaller effect on IDP than did the vertebral fracture itself (with or without compensatory upper-body shift). In cadaveric studies completed in 2005, Berlemann et al described a “stress riser” effect weakening a functional spinal unit (two vertebral bodies and the intervening disk), whereby increased stiffness of the treated vertebra altered the load transfer to the noncemented adjacent level.⁵⁵ Much more pronounced than any stiffness increase resulting from cement injection is the effect on spinal load resulting from the fracture and upper-body shift.⁶² Restoration of anterior vertebral body height and correction of kyphosis reduces the compressive forces by reducing the bending moment.⁶³

Luo et al analyzed “stress profiles” of 28 cadaveric spine specimen comprising three thoracolumbar vertebrae and intervening disks and ligaments before and after compression injury to one of the three vertebrae, and again after vertebroplasty. Induction of the injury reduced IDP to an average of 47% of prefracture value at the affected level and 73% of baseline values at adjacent levels. Injury also transferred compressive load bearing from the nucleus to the annulus and from the disk to the neural arch. Vertebroplasty partially reversed these changes, increasing mean IDP to 76 and 81% of baseline values at fractured and adjacent levels, respectively. Following injury, a 14-fold increase in creep deformation of the vertebral body under load was noted. Vertebroplasty also reversed these changes, reducing deformation of the anterior vertebral body by 62% at the fractured level and 52% at the adjacent level, compared to postfracture values.⁶⁴

Balloon kyphoplasty has been shown to significantly (p < 0.001) restore more than 80% of the original vertebral height following a wedge fracture and to correct vertebral wedge fracture deformity in up to 92% of patients⁶⁵^,⁶⁶ with changes remaining stable for at least two years following surgery.⁶⁵ Local kyphosis reduction continues to be one of the advantages of balloon kyphoplasty over vertebroplasty. Reduction of kyphosis with kyphoplasty has been shown to be greater than that for vertebroplasty (3.7–8 degrees vs. 0.5–3 degrees) and this kyphotic correction allows for a more effortless upright posture leading to relaxation of the paraspinal muscles, reduced pain, and fewer additional VCFs.¹²

Although there is limited evidence that postural reduction (preoperative positioning) is the most important factor for kyphosis correction,⁶⁷ there is strong evidence that the balloon tamps used in kyphoplasty enhance reduction greater than 4.5-fold over positioning maneuvers alone and account for over 80% of the reduction.³⁵^–³⁷^,⁴⁰^–⁴²^,⁶⁸^–⁷⁹

More information on additional or adjacent VCFs after vertebral augmentation can be found in Chapter 17.

11.9 Postoperative Care

Although it is customary to perform kyphoplasty as an outpatient procedure, many affected patients are elderly and have multiple medical comorbidities; thus, an overnight admission may be indicated. Elderly patients have an inherent progressive loss of functional reserve in all organ systems. Common causes of postoperative morbidity include atelectasis, bronchitis, pneumonia, delirium, heart failure, and myocardial infarction.³

Increased vulnerability to perioperative stress favors minimally invasive surgery with shorter operative times and a shorter hospital stay. Meticulous intraoperative management of coexisting disorders and postoperative pain control will help mitigate patient stress. When treating elderly patients, the clinician should always keep in mind that changes in pharmacokinetics and pharmacodynamics render some medications more potent in geriatric patients. Morphine clearance, for example, is decreased in the elderly, leading to a decreased narcotic requirement for pain relief. There is an increase in brain sensitivity to opioids with age.³

Patients are encouraged at discharge to resume all of their typical daily activities as soon as feasible with few restrictions. Patients are examined at 2 weeks postoperatively to evaluate their response to the procedure, their progress in healing, and to determine the need for additional care including physical therapy. Back-strengthening programs are often useful in these patients after kyphoplasty. All patients presenting with VFF should be referred for bone mineral density monitoring and osteoporosis education with treatment as indicated. The treatment of their underlying disorder of osteoporosis will be discussed in greater detail in Chapter 34. If their pain is not resolved or significantly diminished following kyphoplasty, re-evaluation with imaging is indicated. There are countless nonsurgical causes of back pain as well as frequent additional vertebral fractures after the initial vertebral augmentation procedure.

11.10 Conclusion

Kyphoplasty is a minimally invasive procedure designed to relieve pain and improve function in patients with pain and disability associated with VCFs. Results of numerous studies have demonstrated significant and durable pain relief, reduced disability, improved function, and enhanced quality of life after kyphoplasty in patients with VCFs resulting from a wide range of etiologies. In addition, restoration of vertebral height, correction of kyphotic angulation, and improved sagittal balance may decrease the risk of future vertebral fractures.

Performed under general anesthesia or MAC with sedation and local anesthetic, kyphoplasty has an extremely low complication rate in experienced hands and has been shown to significantly improve the rates of patient morbidity and mortality. Kyphoplasty remains a first-line treatment option for patients with painful VCFs unresponsive to medical therapy.