Pathologic vertebral compression fractures (VCFs) can result from a variety of disorders that cause osseous compromise, including osteoporosis, multiple myeloma, and metastatic tumors. Osteoporosis, a systemic disease characterized by decreased bone mass and microarchitectural deterioration, is by far the most common cause of vertebral fractures (1,2). The International Osteoporosis Foundation estimates that more than 200 million women worldwide and nearly 44 million men and women in the United States are at risk for developing fragility fractures secondary to osteoporosis. In the United States, an estimated 700,000 osteoporotic vertebral compression fractures occur annually (3).

Pain associated with acute VCFs can be incapacitating. Although acute symptoms may subside over a period of weeks to months, severe pain may become chronic in some patients (4). Chronic pain may result from incomplete vertebral healing often associated with progressive bony collapse, with altered spine kinematics as a consequence of spinal deformity, or with the development of a true pseudarthrosis at the involved vertebra. In myeloma and metastatic disease, pain also may be caused by nerve stimulation in the endosteum and by increased intraosseous pressure from perilesional edema and tumor enlargement. Chronic pain associated with VCFs often leads to impaired quality of life and depression (4,5).

Regardless of the pain levels related to the VCF, any resulting spinal deformity can adversely affect physical function (4,5,6,7,8,9), quality of life (9,10,11,12,13), and survival (14,15,16,17). These effects are related to the severity of the spinal deformity and are, in part, independent of pain (18,19). Kyphotic deformities in the osteopenic spine may also create a biomechanical environment that promotes additional fractures (20,21,22,23).

The symptoms of acute VCFs are routinely treated medically with some combination of analgesic medication, bed rest, or orthotics. Unfortunately, these treatments can have deleterious side effects. The elderly patient population often poorly tolerates anti-inflammatory and narcotic medications, in part because these drugs may predispose to confusion, increased fall risk, and gastrointestinal side effects. Extended bed rest promotes an overall physiologic deconditioning and further accelerates bone loss. Bracing is also not well-tolerated by older patients and may restrict diaphragmatic excursion. Surgical intervention is usually avoided, except in rare cases in which the fracture is associated with neurological compromise or advanced spinal instability. Spinal surgery in this patient population is fraught with complications, not only related to advanced patient age and comorbidities, but also to difficulties in securing fixation in osteopenic bone.

Over the past decade, percutaneous vertebroplasty, involving the injection of polymethylmethacrylate (PMMA) into a fractured vertebral body in an attempt to alleviate pain, has been popularized. Substantial pain relief has been reported in a majority of patients treated with vertebroplasty for VCFs (24,25,26,27,28,29,30,31). Although effective at relieving vertebral fracture pain, vertebroplasty is not designed to address the associated sagittal plane deformity. Kyphoplasty involves the penetration of the vertebral body with a trochar, followed by insertion of an inflatable balloon tamp. Inflation of the balloon tamp restores lost vertebral height while creating
a cavity for the bone void filler. This technique was first performed in 1998, and results of kyphoplasty suggest significant pain relief, as well as the ability to improve height of the collapsed vertebral body (32,33,34,35,36,37,38,39).

Suggested indications include stabilization of painful osteoporotic and osteolytic vertebral fractures due to osteoporosis, metastases, multiple myeloma, hemangioma, and Kummell disease. Contraindications and precautions include fractures that result in neurologic compromise, result from high-energy injury, possess significant burst components, involve the posterior vertebral body wall, have a geometry that restricts vertebral body access, and have poor intraoperative radiographic visualization. Also, patients who are younger; who have localized spine infections, sepsis, or bleeding disorders; who require anticoagulation therapy; or who risk cardiopulmonary compromise that precludes safely performing the procedure should not be treated.

Vertebroplasty may be performed in a radiology suite or operating room and is typically performed under local anesthesia. The patient is positioned prone with the spine extended by chest and pelvic bolsters. Typically, an 11- to 13-guage needle is advanced toward the center of the vertebral body using a transpedicular or extrapedicular approach and fluoroscopic guidance. Typically, PMMA is mixed with barium sulfate for opacification and sometimes with antibiotics (25,40,41). When the mixture attains the consistency of toothpaste, the cement is transferred to syringes. Between 2 and 10 mL of partially cured cement is injected into the vertebral body under live, multidirectional fluoroscopy. Cement injection is stopped if extravasation is detected. Ideally, the vertebral body is completely filled with cement, but pain relief has been reported when the anterior two-thirds of the vertebra contain cement (42). Using a cement injector tool has been shown to increase epidural cement leakage, while the position of the needle tip in the vertebral body does not predict leakage (43). The patient is not moved from the prone position until the remaining cement has solidified. Most patients rest supine under observation for at least 4 hours before discharge.

Vertebroplasty has proven effective in reducing pain in 60% to 100% of patients from retrospective or consecutive cohort studies. Pain relief often occurs within 72 hours after surgery and is usually stable through follow-up visits, ranging from 6 months to 10 years (27,44,45,46). As a result of the decrease in pain, patient mobility was also reported to improve in many of these studies (46).

The mechanism of pain relief after vertebroplasty is not clear. Pain relief is not proportional to the percentage of lesion filling with cement (47), but one potential explanation may be a mechanical immobilization of the fracture and the support of the cortex by the cement (48,49). Another theory suggests that the heat produced during PMMA polymerization may cause deafferentation of the fractured vertebra.

Vertebroplasty makes no attempt to correct kyphosis and, therefore, will not influence sagittal plane deformity. Recent reports suggest that during vertebroplasty, some vertebral body height restoration can be achieved via postural reduction, particularly if the VCF is characterized by an intravertebral cleft (50,51,52,53,54). Hiwatashi et al. reported an average increase of 2.5 mm anteriorly, 2.7 mm centrally, and 1.4 mm posteriorly in their study of 37 patients who underwent 85 vertebroplasty procedures (50). In a study of 41 patients and 65 VCFs treated with vertebroplasty, McKiernan et al. reported an up to fourfold increase in height restoration, depending on initial fracture severity (55). A vertebral body height restoration study by Teng et al. reported that after 73 vertebroplasty procedures in 53 patients, the mean reduction in kyphosis angle was 4.3 degrees. Gain in the height of the fractured vertebral bodies was 16.7% for the anterior border, 14% for the center, and 7% for the posterior border (53).

The ideal timing of the kyphoplasty procedure is uncertain. In patients with acute VCFs and relatively minor degrees of vertebral collapse, a 6-week trial of conservative care during which serial radiographs are obtained is warranted. If there is progressive collapse of the vertebral body, kyphoplasty is recommended. If the pain attributed to the VCF is incapacitating or does not respond to a period of conservative care, kyphoplasty is recommended. With advanced kyphosis at the time of presentation after a VCF, kyphoplasty may be considered immediately to improve sagittal alignment. It has been observed that thoracolumbar junction fractures, fractures due to steroid-induced osteoporosis, and fractures occurring in vertebrae with extremely low bone mineral density are predisposed to progressive collapse and deformity, so that earlier kyphoplasty may be warranted.

Although this procedure may be performed in a radiology suite or operating room using local, spinal, or general anesthesia,
most kyphoplasty procedures are performed in an operating room with general anesthesia. The patient is positioned prone on a Jackson table with the spine extended by chest and pelvic bolsters. Simultaneous biplane fluoroscopy is used throughout the procedure. An 11-gauge Jamshidi needle is placed percutaneously into the posterior vertebral body through a bilateral transpedicular or extrapedicular approach. The biopsy needles are exchanged over a guide wire for a working cannula. KyphX® inflatable bone tamps (IBTs; Kyphon, Inc., Sunnyvale, CA) are placed bilaterally into the vertebral body through working cannulas. The IBTs are inflated using visual (fluoroscopic) and manometric parameters. Inflation continues until vertebral body height is restored, the IBT contacts a vertebral body cortical wall, the IBT reaches 220 psi, or the maximal balloon volume is reached. After the IBTs are withdrawn, a stylet and bone filler cannula are used to place partially cured PMMA cement mixed with additional barium into the cavity within the fractured vertebral body. The cement volume approximates the volume of the cavity created by the IBT. The patient is not moved from the prone position until the remaining cement has solidified.

Kyphoplasty has proven effective in reducing pain in a majority of patients from retrospective or consecutive cohort studies. Coumans et al. report significant improvement in seven axes of the SF-36 inventory, VAS pain scores, and the Oswestry Disability Index (ODI) that were durable for up to 1 year (36). Similarly, Wong et al. reported a 94% reduction in pain in their study of 85 patients treated with 143 kyphoplasty procedures (42). Ledlie et al. achieved an 89% pain reduction and significant improvement in mobility that was durable for at least 1 year in their 96 patients following 133 procedures (35).

Kyphoplasty has the potential to improve spinal deformity by elevating the vertebral end plates before fixation. Initial reports indicate that vertebral height could be restored partially or completely in the majority of fractures (42,56). Lieberman et al. reported vertebral height restoration in 70% of 70 fractured vertebrae treated with kyphoplasty. In those patients whose vertebral fractures were reduced by kyphoplasty, vertebral height was increased by a mean of 46.8% (57). In treated fractures, Ledlie et al. report a 35% and 38% increase in the predicted anterior and midline height, respectively, which correspond to a 68% to 71% restoration of lost height. In addition, the increase in height associated with kyphoplasty was stable for at least one year (35). Rhyne et al. found improved anterior and midline height of 4.6 and 3.9 mm, Cobb angle increase of 14%, a VAS score increase of 7 points, and Roland-Morris Disability Survey improvement of 11 points (32). Crandall et al. investigated the difference in the effect of kyphoplasty on acute and chronic fractures. Acute fractures were associated with greater increases in height and Cobb angle, but chronic fractures also experienced significant increases in height and Cobb angle, as well as improved VAS pain and ODI scores (39).

Fourney et al. report on kyphoplasty, vertebroplasty, or a combination of both for the treatment of fractures in cancer patients. The mean percentage of restored vertebral height after kyphoplasty was 42% with significant improvement in local kyphosis of 4.1 degrees and significant increase in VAS pain scores (58). Berlemann et al. report an average vertebral kyphosis reduction of 47.7% and no loss of reduction after 1 year in a small study of 24 patients with 27 osteoporotic VCFs. In fractures less than 40 days old, reduction was 54.6% and in fractures older than 40 days, a change of 35.8% was measured (33).

Phillips et al. reported the effects of kyphoplasty on sagittal alignment using a radiographic technique that has been previously validated for measurement of posttraumatic kyphosis. In those authors’ early experience with kyphoplasty, local sagittal alignment was improved by a mean of 8.8 degrees for all fractures and 14.2 degrees in those fractures considered reducible (i.e., that experienced at least 5 degrees of correction) (34). This degree of improvement in local sagittal alignment reported with kyphoplasty is similar to that reported for open reduction and internal fixation of traumatic burst fractures. Esses et al. reported a 9.3-degree (anterior instrumentation) and 11.3-degree (posterior instrumentation) improvement in local kyphotic angle with open reduction and internal fixation of burst fractures (59).