Kyphoplasty and Vertebroplasty

Sina Rajamand and Daniel K. Fahim

Abstract

Vertebroplasty and kyphoplasty are useful vertebral augmentation surgeries that can be performed in an inpatient or outpatient setting to effectively treat acute pathologic or traumatic compression fractures of a vertebral body causing intractable pain. When indicated, the fairly simple procedures of vertebroplasty and kyphoplasty are extremely effective in reducing the debilitating pain associated with vertebral body compression fractures especially in the osteoporotic elderly population. Patients are able to return to their baseline functional level of activity postprocedure due to the reduction of pain. With the utilization of modern imaging techniques including X-ray, CT scans, MRI studies, and bone scintigraphy, the clinician is able to quickly identify and intervene in patients with acute compression fractures of a vertebral body to limit debility and the potential comorbidities that can be associated with it.

Keywords: vertebroplasty, kyphoplasty, compression fracture, vertebral body, vertebral augmentation, pathologic compression fracture

29.1 Introduction

Vertebroplasty was first performed in France in 1987 for painful vertebral body hemangioma treatment. Shortly thereafter, it was used to treat osteoporotic compression fractures. It was later introduced in the United States in 1993. A subsequent modification of the original procedure, involving fracture reduction with the use of a balloon, was introduced in 1998.¹^,²^,³

Osteoporotic vertebral compression fractures affect more than 700,000 Americans per year, and approximately 10 million people are affected by osteoporosis in the United States.⁴ Vertebral compression fracture may be the first symptom of osteoporosis, and clinicians must be vigilant in correctly diagnosing this potentially devastating disease. Although vertebroplasty and kyphoplasty are used in other pathologies resulting in painful compression fractures (such as metastatic disease), they are most frequently utilized in osteoporotic vertebral compression fractures.

Vertebroplasty is a minimally invasive procedure where polymethyl methacrylate (PMMA) is injected into the vertebral body to treat pain associated with a compression fracture of that segment.⁵ Kyphoplasty is similar, except a balloon tamp is inserted prior to injection of the cement and a cavity is created within the vertebral body into which PMMA is subsequently injected.⁶ Kyphoplasty is the more expensive and technically demanding of the two. However, relative benefits of kyphoplasty are the ability to restore height by virtue of the balloon and the compaction of the cancellous bone in the vertebral body resulting in greater strength along the cortical walls.⁷^,⁸ The creation of a cavity by the balloon is also thought to lessen the chance of cement migration or leakage during cement injection, which is a complication more frequently observed with vertebroplasty. The cavity helps loculate and contain the cement and the compaction of the cancellous bone will theoretically tamp off the previous channels and pores created from the original fracture. The cement acts like an internal cast that stabilizes that segment. Pain relief is thought to be a function of both the stabilization of the vertebral body and denervation of the bone matrix due to the cytotoxicity of the cement to the nerve tissue, as well as free oxygen radical production and heating during cement polymerization.⁹^,¹⁰

29.2 Indications and Contraindications

29.2.1 Indications

Indications for kyphoplasty are osteoporotic compression fractures, traumatic compression fractures, and compression fractures secondary to metastases to the vertebral body that are limiting the mobility and functional capacity of the patient.¹¹^,¹²^,¹³ Guidelines from the Society of Interventional Radiology and the Cardiovascular and Interventional Radiological Society of Europe state the indications for vertebroplasty are as follows¹⁴:

• Osteoporotic vertebral compression fractures refractory to 3 weeks of analgesic therapy.

• Primary or secondary benign or malignant bone tumor resulting in painful vertebrae.

• Painful osteonecrotic vertebral compression fracture.

• Reinforcement of a vertebral segment prior to surgical intervention.

• Chronic traumatic vertebral compression fractures with nonunion.

Even a short period of pain limiting activity may be unacceptable and deleterious to an elderly individual with already limited mobility. The comorbidities of substantially decreased daily activity and prolonged bed rest due to pain can lead to detrimental adverse outcomes such as deep venous thrombosis, pulmonary embolism, pressure ulcers and sores, decreased muscle mass, and further decreased bone density. Decreased bone density or osteoporosis is one of the main factors in vertebral body compression fractures. Further decrease in bone density due to decreased stress on the bones of the body from limited daily activity and prolonged bed rest can progress to long bone fractures and compression fractures of other vertebral levels, leading to further decrease in activity resulting in a downward spiral with the eventual demise of the patient due to irrecoverable insults to the body and the morbidity and mortality attributable to prolonged bed rest.

Suitability for vertebral augmentation surgery can be evaluated with proper imaging. Plain radiographs of the spine are often the starting point due to the nature of the disease. Patients are often discovered to have a compression fracture at their primary doctor’s office or in the emergency department where a plain radiograph is inexpensive and easily obtained. CT scans and MRIs are more definitive and are often the next step in diagnostic imaging. Bone scans can also be useful in evaluating compression fractures of vertebral bodies.¹⁵^,¹⁶^,¹⁷ CT scan is excellent at identifying vertebral fractures or osseous destruction; however, it is less helpful in evaluating the acuity of the injury. MRI is useful to identify the chronicity versus acuity of a compression fracture by evaluating the presence or lack of edema. Alternatively, bone scintigraphy can identify which levels to treat as increased uptake generally indicates acute fracture of the vertebral body. The vertebral segment with increased uptake has been shown to respond well to vertebral augmentation with kyphoplasty or vertebroplasty.¹⁵^,¹⁶^,¹⁷ However, bone scans have continued to show increased uptake up to 1 year after an injury, making it difficult to discern acute injuries from chronic injuries with this modality alone. In this situation, vertebral augmentation surgery may have limited benefits as it is recommended to treat compression fractures less than 8 weeks old for the best results.¹⁵

As the number of patients with metastases to the spine increases, there is a rapidly growing body of literature on vertebral body compression fractures in this patient population. Although a painful vertebral body compression fracture secondary to a metastatic lesion is a well-established indication for kyphoplasty, the indications for “prophylactic” vertebral body augmentation are under investigation.¹⁸^,¹⁹^,²⁰ Patients with spine metastases frequently undergo radiation therapy. Increasingly, these patients are undergoing stereotactic radiosurgery. Multiple studies have identified risk factors for the development of compression fractures in patients receiving radiation for treatment of spine metastases. There is growing discussion about offering prophylactic vertebral body augmentation for patients with increased risk of developing compression fractures during their radiation treatment.²¹^,²²^,²³

29.2.2 Contraindications

Contraindications include nonpainful or asymptomatic vertebral compression fractures, adequate pain control with oral analgesics, sepsis or active systemic infection, epidural abscess, infection in the soft tissue or skin overlying the approach trajectory, severe or uncorrectable coagulopathy, cord compression from retropulsion of bone resulting in myelopathy, complete collapse of the vertebral body (vertebra plana), allergy to PMMA, and severe posterior vertebral body wall destruction.²⁴^,²⁵^,²⁶ Relative contraindications include radicular pain, vertebral compression fractures greater than 70% of vertebral body height, and advanced tumor extension into the central canal. Osteomyelitis presents an interesting challenge as this disease entity can result in painful compression fractures that can sometimes be effectively treated with PMMA mixed with an antimicrobial agent (in addition to the requisite intravenous [IV] antibiotics).

29.3 Surgical Technique

The procedure can be performed in the outpatient setting with conscious sedation and local anesthesia in a location with the proper imaging tools. Usually patients can return to their normal daily activity that day, and often patients have almost immediate pain relief.

29.3.1 Patient Positioning

The patient is sedated and then positioned prone with arms above their head. An imaging apparatus is then properly set up for a biplane image. The procedure can be performed in either a biplane angiography suite or with two C-arm fluoroscopy machines. Anteroposterior (AP) and lateral fluoroscopic images are obtained to localize the fractured vertebral level. The patient is prepped and draped in the usual fashion. The skin is marked approximately 1 cm lateral to the lateral and superior border of the pedicle. Next, the skin surface is anesthetized with a small gauge needle, creating a wheal with lidocaine. Once the skin surface has been anesthetized, a longer needle with local anesthetic is inserted down to the periosteal level of the proposed trocar entry site at the pedicle and anesthetic is injected while withdrawing the needle.

29.3.2 Procedure

A small stab skin incision is made at the proper level and a trocar needle is introduced to localize the pedicle. An AP image and a lateral image are obtained to assure proper alignment. The AP image should show the tip of the trocar at the lateral superior edge of the pedicle. Care must be taken not to cross the medial border of the pedicle prior to entering the body of the vertebrae. Early medialization can result in entering the central canal and damaging the cord or nerve roots. If a parapedicular approach is chosen, the trocar is placed on the transverse process of the chosen vertebral level and walked superiorly and laterally just above the transverse process.²⁷^,²⁸ The trocar is then advanced with biplane guidance to enter the vertebral body just lateral to the pedicle at the pedicle body interface. The pedicle body interface can best be visualized with the lateral X-ray. The trocar needle should be passed until it resides near the center of the vertebral body. A bipedicular approach results in the most uniform cement injection; however, a unipedicular approach can result in sufficient cement placement, as well.²⁹^,³⁰^,³¹^,³²^,³³ There are also instruments with articulating heads for the balloon-tapping portion of a kyphoplasty that will help facilitate obtaining a midline deployment of the balloon.

Once the proper position is reached and confirmed with AP and lateral images, the trocar introducer needle portion is taken out leaving behind the dilator. Injection of cement is then performed. The cement used is usually PMMA with contrast material premixed into the preparation. The PMMA is mixed to the consistency of toothpaste before injection. Injection is performed under fluoroscopic guidance with frequent images to visualize the placement of the cement insuring there is no extravasation through venous tributaries or posterior leakage into the spinal canal, which can have detrimental consequences. Enough cement is usually injected under direct fluoroscopic guidance to fill the anterior 2/3 of the vertebral body. The introducer needle is left in place for a few minutes to allow cement setting. Marcaine without epinephrine is injected along the paraspinal muscles for postoperative analgesia. The needle is then removed and the incision sites are closed, usually with a skin adhesive.

29.4 Postoperative Care

The patient can be left prone for another 10 to 15 minutes to allow the cement to further harden. The patient is then returned to the supine position and observed in the recovery room until he or she is sufficiently awake and stable to be discharged home, hopefully with much less pain.

29.5 Management of Complications

Complications include failure to obtain pain relief or worsening of symptoms, osteomyelitis, vertebral fracture, pedicle fracture, retropulsion or spillage of cement into the spinal canal or neural foramen, paralysis, nerve root irritation or damage, venous embolism, and fatal anaphylactic reaction to PMMA (very rare but reported).³⁴^,³⁵^,³⁶^,³⁷^,³⁸^,³⁹^,⁴⁰

29.6 Clinical Case

A 95-year-old female was brought to the emergency department with a status post fall from standing 10 days before. Since that time, the patient had been bedridden secondary to severe lower back pain. CT scan and MRI demonstrated an L3 compression fracture. Due to the severe morbidity and mortality associated with prolonged bed rest in a 95-year-old, including deconditioning, potential for deep venous thrombosis, urinary tract infections, skin breakdown and ulceration leading to infection, and pneumonia, a decision was made with the patient and family that a percutaneous kyphoplasty would be an appropriate procedure. All risks of the procedure were also discussed with the patient and family ( Fig. 29.1).

29.7 Conclusion

Kyphoplasty is a safe and effective treatment for painful vertebral body compression fracture etiology, even in patients of advanced age. It can routinely be performed with local anesthetic and sedation on an outpatient basis.

Clinical Caveats

• Osteoporotic vertebral compression fractures affect around 700,000 Americans per year.

• Vertebral augmentation surgery is useful for the treatment of painful acute or pathological compression fractures of the vertebral body.

• Vertebroplasty and kyphoplasty are vertebral augmentation surgeries that can be performed in the inpatient or outpatient setting with local anesthetic and sedation.

• Compression fractures can be debilitating, especially in the elderly osteoporotic population. Vertebral augmentation through vertebroplasty or kyphoplasty can prevent the comorbidities associated with pain limiting activity in this population by decreasing the pain associated with these fractures and returning them to functional daily activities sooner.

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