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Vertebroplasty and Kyphoplasty for the Management of Osteoporotic Vertebral Compression Fractures
Orthop Clin N Am 38 (2007) 409–418
Vertebroplasty and Kyphoplasty for the Management of Osteoporotic Vertebral Compression Fractures Dhruv B. Pateder, MDa,*, A. Jay Khanna, MDb, Isador H. Lieberman, MD, MBA, FRCSCc a Steadman Hawkins Clinic, 181 West Meadow Drive, Suite 400, Vail, CO 81657, USA Johns Hopkins Orthopaedic Surgery at Good Samaritan Hospital, 5601 Loch Raven Boulevard, Suite G-1, Baltimore, MD 21239, USA c Department of Orthopaedic Surgery, Cleveland Clinic Spine Institute, A-41, The Cleveland Clinic Foundation, 9500 Euclid Ave., Desk A-41, Cleveland, OH 44195, USA b
Osteoporosis is a bone condition marked by a decrease in bone mass and density [1]. The pathophysiology of this condition is marked by an imbalance between bone production (by osteoblasts) and bone resorption (by osteoclasts) [1]. In normal bone, these two processes are tightly regulated and there is a balance between bone resorption and formation; however, in osteoporotic bone, there is an increase in osteoclastic bone resorption due to an overall decrease in osteoblastic bone production or a direct increase in bone resorption (ie, tumor cells directly stimulating osteoclasts) [1]. There are categories of osteoporosis: primary, secondary, and idiopathic [1]. Primary osteoporosis is further subdivided into senile and postmenopausal osteoporosis. Senile osteoporosis is a gradual decrease in bone mass that begins in all people during midadulthood and continues until death; it is due to a decrease in osteoblastic formation leading to a relative decrease in bone formation. Postmenopausal osteoporosis is marked by rapid bone loss that begins after menopause due to the loss of estrogen and its inhibiting effect on osteoclasts [1–3]. This process occurs concomitantly with senile osteoporosis and leads to very rapid bone loss [1–3]. Secondary osteoporosis is the result of any age-independent factors that lead to bone loss, Drs. Lieberman and Khanna are consultants for Kyphon, Inc. * Corresponding author. E-mail address: [email protected] (D.B. Pateder).
such as corticosteroids, diabetes, secondary amenorrhea, and so forth [1]. Idiopathic osteoporosis is a condition in which there is abnormal bone loss without any identifiable causative factors. There are over 26 million women in the United States affected by osteoporosis and over 700,000 pathologic vertebral body compression fractures annually (with thoracic and lumbar locations occurring most commonly) [4,5] (Fig. 1). With more than 25% of women over age 65 years sustaining a vertebral compression fracture, it is the most common complication of osteoporosis [6]. Vertebral compression fractures can be divided into two different morphologic types. The first type is the commonly encountered acute crush fracture, whereby the patient experiences sudden onset of pain and muscle spasm after some sort of minor or major trauma [1,6]. These fractures can sometimes be difficult to differentiate from pathologic fractures and may require a biopsy [7]. The second type is a minimally symptomatic anterior wedge compression fracture that occurs over multiple levels in time and leads to a kyphotic deformity and a loss of height [1,7]. Although vertebral fractures are the most common osteoporotic fractures, proximal femoral neck fractures are associated with the highest mortality [3,8]. Given the grave prognostic implications of femoral neck fractures on ambulation and overall health, patients who have hip fractures undergo operative fixation in an urgent manner; however, until recently, vertebral body compression fractures have been treated with
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Fig. 1. Lateral radiograph demonstrating a compression fracture of a thoracic vertebra.
medical management or benign neglect unless there was gross loss of spinal balance or an associated neurologic deficit [9–12]. Traditionally, this treatment was the case because vertebral compression fractures did not have any immediate effect on ambulation, and surgery to restore height and alignment meant subjecting the patient to the tremendous morbidity of thoracotomy or abdominal surgery in addition to the inherent problems associated with repairing brittle osteoporotic bone. Over time, however, it has become clear that approximately one third of vertebral compression fractures go on to become chronically painful [13]. In addition, several studies have shown that disturbance of the normal sagittal balance can lead to further back pain and have a negative effect on the ability to participate in the activities of daily living [14,15].
Percutaneous vertebral body augmentation Given the detrimental effects of nonoperative care and the morbidity associated with open reduction and internal fixation of vertebral compression fractures, there have been recent advances in minimally invasive modalities to address these fractures. Over the past 2 decades, vertebroplasty (a procedure in which polymethylmethacrylate [PMMA] is percutaneously injected into the vertebral body) was developed as a way to stabilize vertebral compression fractures without inducing the morbidity and mortality associated with open surgery [16]. More recently, kyphoplasty has been developed to address vertebral compression fractures [17]. Kyphoplasty is differentiated from vertebroplasty in that kyphoplasty
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involves inserting an inflatable balloon in the vertebral body to elevate the vertebral end plates; PMMA is then inserted in this cavity [18]. The theoretic advantages of this procedure over vertebroplasy include its ability to restore vertebral height and kyphosis and to allow for the more controlled deposition of the PMMA in a cavity, thus decreasing the risk for cement extravasation. Although vertebroplasty and kyphoplasty have been shown to reduce the back pain of vertebral compression fractures [16–19], identifying patients who would benefit from these procedures requires a thorough workup incorporating the findings of history, physical examination, and imaging studies [18]. Clinicians need to be extremely careful in correlating a patient’s back pain with the compression fracture. Most patients who have acute compression fractures report a sudden onset of back pain that may or may not be associated with a traumatic event. Because many of these patients have severe osteoporosis, many vertebral compression fractures occur with simple activities such as bending down or getting up from a seated position. On physical examination, patients who have acute compression fractures tend to have tenderness directly over the fracture site. This is an important finding because it helps differentiate back pain associated with compression fractures from ‘‘low back pain’’ [17]. Posteroanterior and lateral radiographs are very useful in detecting most vertebral compression fractures and the overall spinal column alignment; however, it is often difficult to differentiate whether the fracture is acute or chronic or whether it is a pathologic fracture. MRI is an excellent imaging modality because not only can it demonstrate the edema associated with acute compression fractures, but it can also detect any tumorous lesions that may have caused the fracture or may be present in other vertebral bodies. Special care should be taken to evaluate the sagittal T2-weighted and fat-suppressed T2-weighted or the short tau inversion recovery images (Fig. 2). These images show increased signal intensity at the fracture site in patients who have acute and subacute fractures and, thus, allow for selection of those patients more likely to experience pain relief after a vertebral augmentation procedure [20]. Patients who demonstrate no increased signal intensity on these images are unlikely to experience pain relief after vertebral augmentation. For patients who have a contraindication to MRI evaluation (ie, presence of a pacemaker or claustrophobia), nuclear scintigraphy (bone scan) can be used to evaluate the acuity and physiologic activity at the fracture site.
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Fig. 2. A fat-suppressed T2-weighted MRI demonstrating a compression fracture (high signal) of a lumbar vertebra.
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[23] recently demonstrated the long-term (24 months) efficacy of kyphoplasty on back pain relief, back function, and quality of life in a prospective, multicenter study of 155 patients. It is unfortunate that this study did not have a nonoperative control group; however, the presence of a vertebral collapse predicted increased mortality and a fivefold increase in further fractures at adjacent or remote levels within 1 year [19]. Some contraindications for these percutaneous procedures include fractures associated with neurologic injury, fractures with a burst component, a fracture with a cleft or fracture plane that extends into the spinal canal, and healed, chronic compression fractures [18]. In patients who have severe cardiac disease, percutaneous vertebral augmentation also poses an additional risk that is cumulative for each added level because the PMMA contains a vasodilatory agent that is rapidly absorbed systemically [18]. Technique of vertebroplasty
Selection criteria It is important for the physician to treat only the symptomatic fractures and not to treat all fractures seen on imaging studies, because most evidence suggests that healed fractures are stable and do not cause pain [18,21]. Indications for vertebroplasty and kyphoplasy in the treatment of vertebral compression fractures include acute, painful osteporotic or osteolytic vertebral compression fractures; isolated vertebrae with metastatic lesions that are causing pain; painful vertebral hemangioma; and Ku¨mmell’s disease [18]. Similar to any other fragility fracture, the goals are to restore stability, anatomic alignment, and function as soon as safely possible. Although it is well-documented that 66% of patients who have vertebral compression fractures become asymptomatic after several months, it is important to remember that these fractures heal in a malaligned position where the vertebral height and the fractured vertebra’s relationship to adjacent vertebrae have been compromised [13,16]. A recent study by Diamond and colleagues [22] found that vertebroplasty for acute compression fracture was significantly better than nonoperative treatment in terms of pain relief, level of function, and hospital stay. Of interest, there were no differences in pain relief between the two groups at 12 and 24 months after the procedure. In addition, there was no significant difference between the two groups in the rates of new vertebral fractures or death. Similarly, Garfin and associates
Percutaneous vertebroplasty was started in France in 1984, introduced by Galibert and colleagues [24] in 1987, and subsequently introduced in the United States in 1993 [16]. Vertebroplasty is performed with the patient in a prone position with bolsters under the sternum and pelvis to reduce kyphosis at the fractured vertebra [3]. Although this procedure can be performed under local anesthetic for one or two levels, it is usually performed under general anesthesia in patients undergoing multiple-level vertebroplasty or who will not be able to stay still during the procedure if done under local anesthesia [17]. Fluoroscopy is used to identify the pedicles and end plates of the vertebrae in its true anteroposterior (AP) and lateral dimensions so that there is no parallax. This step is perhaps one of the most important in the procedure because it allows the most accurate and thus safest placement of the cannulas and other instruments. An extrapedicular or a transpedicular approach can be used to enter the vertebral body from its posterior aspect as described previously [17]. Both approaches have been shown to be safe and efficacious. A common practice is to use a transpedicular approach when the pedicles are larger, such as in the lumbar spine and lower thoracic spine, and an extrapedicular approach in the mid and upper thoracic spine. During vertebroplasty, PMMA is injected in a more fluid state because there is no cavity created for it and the cement permeates into the
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cancellous bone of the fractured vertebra. It is extremely important to inject the barium-impregnated cement under live fluoroscopy or while using multiple single-frame fluoroscopic views. If there is any extravasation of the cement from the vertebral body, particularly posteriorly toward the spinal canal, then the procedure must be immediately halted and the situation assessed. A certain degree of cement extrusion from the vertebra can be tolerated without any deleterious effects to the patient, but there have been reported cases in which cement extrusion has caused neurologic damage [18]. Although initial studies
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suggested that there was no fracture reduction or height restoration with this technique, more recent studies have demonstrated that fracture reduction and height restoration are achieved due to the dynamic mobility of the acute fracture (Fig. 3) [25]. Although there is no consensus on the definitive mechanisms for pain control, it is probably achieved by way of a multitude of pathways including fracture stabilization as the cement hardens and heat necrosis of the nerve endings at the fracture site. Some investigators have suggested that some height restoration can be achieved in vertebroplasty by putting the trocar
Fig. 3. Preoperative AP (A) and lateral (B) radiographs demonstrating a L1 compression fracture. (C) Sagittal fat-suppressed T2-weighted MR image demonstrating the compression fracture. Postoperative AP (D) and lateral (E) radiographs after a kyphoplasty of the L1 vertebra.
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in the fracture cleft and extending at the site, thus opening up the fracture [3]; however, there are no studies confirming this. One of the dangers of this maneuver is that the open cleft can allow cement to escape from the confines of the vertebral body and into the surrounding tissue. As a result, one must be extremely careful with this maneuver and may consider performing a kyphoplasty if height restoration is desired. Technique of kyphoplasty Similarly to vertebroplasty, kyphoplasty begins with prone positioning on a radiolucent table with bolsters and by using biplanar fluoroscopy to identify the anatomic landmarks on true AP and lateral views. Entry into the vertebral body is performed similarly by way of an extrapedicular or transpedicular approach as described previously [17]. Unlike vertebroplasty, however, after the cannula is appropriately placed in the vertebral body, a hand drill is placed through the cannula, with the goal being that the drill tip is eventually placed just posterior to the anterior vertebral cortex on the lateral view and past the midline on the AP view. On the lateral view, when the drill is midway across the vertebral body, an AP image should be obtained; on the AP view, the drill should be midway between the pedicle and spinous process. If it is closer to the spinous process than this, then there is a chance that it could be in the spinal canal; similarly, if it is too close to the pedicle on the AP view, then it may be out laterally. After
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the appropriate track is created, the drill can be removed. The drilling allows for the creation of a pathway for the placement of the inflatable balloon tamp. The balloon is placed in the cavity and inflated using a manometer with a digital pressure gauge (Fig. 4). The balloon contains saline with barium in it such that it may be visualized under fluoroscopy as it is inflated. It is recommended that it be inflated under live fluoroscopy to ensure that it does not malreduce the fracture or fracture the vertebral end plate. When two balloons are to be used, most surgeons first place them both and then inflate them at the same time or alternately (‘‘backand-forth’’) to prevent ‘‘herniation’’ of the first balloon to the contralateral side, thus preventing ideal placement of the second balloon. When only one balloon is to be used, the balloon can be deflated and the cement (mixed with barium) deposited into the cavity under live fluoroscopy in a retrograde fill pattern, from the ventral aspect of the cavity to its dorsal aspect (Fig. 5A, B). The consistency of the cement used for kyphoplasty is different than it is for vertebroplasty. For vertebroplasty, the cement must be in a more liquefied state to permeate and spread into the vertebral cancellous bone, whereas for kyphoplasty, it can be in a more viscous or ‘‘doughy’’ state because it is deposited in a cavity created by the balloon. The surgeon should be aware of the setting times of the cement before performing a clinical case, and usually the cement is ready to be injected for kyphoplasty when it no longer
Fig. 4. Intraoperative AP (A) and lateral (B) fluoroscopic images demonstrating balloon placement in the vertebra during a kyphoplasty procedure. (C) After the balloon is in satisfactory position, it is inflated to create a cavity for the cement.
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Fig. 5. (A,B) After the balloon is deflated and removed, cement (mixed with barium) is deposited into the cavity under live fluoroscopic guidance in a retrograde fill pattern (from the ventral aspect of the cavity to its dorsal aspect). Final AP (C) and lateral (D) radiographs are taken to evaluate cement position and overall alignment.
sticks to the surgeon’s gloves. The volume of liquid used to inflate the balloon provides a general idea about the quantity of cement that will be required for each level. When ready to fill, the inflatable bone tamp is deflated and the balloon is carefully removed. A cement cannula is advanced to the anterior aspect of the vertebral body by passing it through the working cannula. Fluoroscopy is used to confirm the location of the cannula. When the cannula is in a satisfactory position, cement is slowly ejected by pushing it out of the cannula with a blunt probe. As more cement is ejected into the cavity, the cement cannula should be pulled back slightly to allow cement to be injected into the posterior aspect of the cavity. The cement generally does not extravasate unless it is too thin or there has
been a breach in the vertebral cortex. When a cement leak (out of the intended cavity) is detected, injection should be stopped immediately and the cement allowed to harden for 1 to 2 minutes before slowly injecting again under live fluoroscopic guidance. When the cement is hardened, the cannula can be removed and final imaging views can be taken (see Fig. 5C, D).
Results Vertebroplasty and kyphoplasty are highly successful procedures when it comes to relieving the pain associated with vertebral compression fractures [26–33]. Patients undergoing vertebroplasty experience pain relief within 72 hours and
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have reported consistent pain relief for up to 10 years after the procedure [21]. Studies have also reported an improvement in functional outcomes and analgesic requirements after vertebroplasty. Similarly, Garfin and colleagues [34] reported that 90% of 1439 patients treated with kyphoplasty reported significant pain relief within 2 weeks after undergoing the procedure. Lieberman and colleagues [17] and, more recently, several different investigators [26] have reported significant improvement in overall SF-36 function scores in a large group of patients who had undergone kyphoplasty. In a review of patients undergoing kyphoplasty, Phillips and colleagues [28] noted that visual analog scores also improved from 8.6 preoperatively to 2.6 at 1week postoperatively and to 0.6 at 1 year postoperatively in patients undergoing kyphoplasty. Kyphoplasty affords deformity correction at the fractured vertebra and has been found to correct up to 97% of the deformity (compared with 30% with vertebroplasty) in an ex vivo model [35]. Numerous clinical studies have also demonstrated the ability of kyphoplasty to restore vertebral height anywhere from 50% to 70% and to improve the sagittal angulation at the fracture site [17,27,28,34]. A recent study by Shindle and colleagues [36] demonstrated that fracture reduction with kyphoplasty was 46.6% better than postural reduction with extension positioning alone. Of interest, Pradhan and colleagues [37] found that although kyphoplasty can restore height at the fractured vertebra, it did not lead to an improvement in overall sagittal balance. In a prospective study of patients who had reducible nonacute vertebral fracture with kyphotic deformity, Grohs and colleagues [38] found that although vertebroplasty and kyphoplasty were effective in reducing pain in the short-term, kyphoplasty had a longer-lasting effect on pain relief and activities of daily living compared with vertebroplasty. The investigators attributed this effect to restoration of sagittal balance and its secondary effect on reducing the work and subsequent fatigue of the paraspinal musculature [38]. In a very systematic and well-designed meta-analysis of 69 studies (37 retrospective, 25 prospective, and 7 nonreported study designs), Hulme and associates [39] found that vertebroplasty and kyphoplasty were similar with regard to pain relief (87% of patients for vertebroplasty versus 92% of patients for kyphoplasty), vertebral height restoration (6.6 for both), and refracture rates. The only difference between the two groups was the
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rate of cement extravasation, occurring in 41% of the vertebroplasty patients versus 9% of the kyphoplasty patients.
Complications Although complications are very rare after vertebral augmentation procedures, there have been reports of cement leakage and neurologic injuries with both procedures. Extravertebral cement extrusion has been reported to be as high as 65% with vertebroplasty, and although this is usually clinically asymptomatic, cases of spinal cord and nerve root injuries have been reported [18,27–29,40]. A recent study in 2006 by Bhatia and colleagues [41] found asymptomatic cement leaks in 22.5% of osteoporotic vertebral fractures that underwent percutaneous vertebroplasty. With kyhoplasty, extravertebral cement extrusion has been reported to be as high as 10% in several different studies without any clinical consequences or leakage into the spinal canal [18,27–29]. In an interesting study by Schmidt and colleagues [42], it was discovered that only 34% of intraoperative cement leaks are discovered using lateral fluoroscopy and that by using AP and lateral fluoroscopy, the detection rate increases to 48%. In other prospective multicenter studies, a major complication rate of 1.1% has been reported; of these complications, 0.75% were neurologic complications [18].
Kyphoplasty versus vertebroplasty Although kyphoplasty and vertebroplasty have been shown to provide excellent pain relief, there is still a great deal of debate regarding which of the two procedures is ‘‘better.’’ One should keep in mind that the two procedures are not mutually exclusive and that they may be used for specific fracture types and indications to provide a spectrum of treatment that ranges from stabilization of the vertebral body to reduction and reconstruction of the fracture and spinal column. One of the most significant advantages of kyphoplasty over vertebroplasty is that it has now been shown in multiple studies to restore lost vertebral body height, thus preventing kyphosis at that level and its potential long-term implications [17,28,34,35]. Ledlie and colleagues [27] reported height restoration from radiographic measures of anterior and midline points of the fractured vertebra using the two nearest normal vertebrae as
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reference points [27,34]. Ledlie and colleagues [27] reported that one year after kyphoplasty, the anterior vertebral height restoration was maintained at 20% greater than preoperative height, whereas midline height was maintained at 16% greater than preoperative height. Similarly, Phillips and colleagues [28] reported that sagittal alignment in kyphoplasty patients improved between 8.8 and 14.2 in vertebral compression fractures. The other potential advantage of kyphoplasty over vertebroplasty is the lower reported rates of cement extravasation as previously discussed. It is important to note, however, that most of the cement extravasations seen with vertebroplasty have little or no clinical significance. The longterm implication of the differences in cement extravasation is unknown. In a meta-analysis of 75 studies, Taylor and colleagues [43] cited the overall excellent benefit-to-harm ratio of vertebroplasty and of kyphoplasty and suggested that the higher cement extravasation rate and the adverse event rate (pulmonary embolism and neurologic injury) give vertebroplasty a slightly lower benefit-to-harm ratio than kyphoplasty. Biomechanical studies have found that cement augmentation leads to increased stiffness in that vertebral body and can lead to altered forced distribution in the adjacent vertebrae, thus increasing the chances of additional osteoporotic compression fractures [44]. Although data regarding adjacent-level fractures after vertebroplasty or kyphoplasty are limited, Grados and colleagues [45] reported a 52% incidence of remote or adjacentlevel vertebral compression fractures after vertebroplasty. The incidence of this phenomenon seems to be lower after kyphoplasty, with one study reporting an approximate 11% incidence of adjacent-segment fractures in primary osteoporotic patients [46]. Similarly, Phillips and colleagues [28] reported new adjacent-level compression fractures in 3 of 29 patients who underwent kyphoplasty for osteoporotic compression fractures. In the most current study, Pflugmacher and colleagues [47] reported a 10% annual refracture rate after kyphoplasty. These results suggest that kyphoplasty is perhaps less prone than vertebroplasty to cause adjacent-level compression fractures by more effectively restoring the overall spinal balance.
Summary Although osteoporotic vertebral compression fractures were treated nonoperatively in the past
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due to the substantial morbidity of open surgery, they can now be stabilized using relatively benign minimally invasive techniques. Vertebral augmentation by vertebroplasty or kyphoplasty is clearly an effective treatment for painful progressive osteoporotic compression fractures. Although each technique has its own advantages and disadvantages, numerous studies have shown that the techiniques are similar with regard to functional outcomes and short-term improvement in pain. Although each technique has its supporters and critics, both techniques have unique advantages and disadvantages that afford them a vital role in the treatment of osteoporotic compression fractures. Future studies directly comparing different aspects of these two techniques will elucidate whether one is superior to the other or whether the choice of procedure should be made based on the fracture configuration or other clinical or radiographic parameters. References [1] McCarthy EF, Frassica FJ. Metabolic bone disease. In: Frassica FJ, McCarthy EF, editors. Pathology of bone and joint disorders. Philadelphia: WB Saunders Company; 1998. p. 88–99. [2] Silver JJ, Einhorn TA. Ostoporosis and aging. Clin Orthop 1995;316:10–20. [3] Rao RD, Singrakhia MD. Painful osteoporotic vertebral facture: pathogenesis, evaluation, and roles of vertebroplasty and kyphoplasty in its management. J Bone Joint Surg Am 2006;85(10):2010–22. [4] Melton LJ III, Kan SH, Frye MA, et al. Epidemiology of vertebral fractures in women. Am J Epidemiol 1989;129:1000–11. [5] Cooper C, Atkinson EJ, O’Fallon WM, et al. Incidence of clinically diagnosed vertebral fractures: a population-based study in Rochester, Minnesota, 1985–1989. J Bone Miner Res 1992;7:221–7. [6] Lopez LM, Grimes DA, Schulz KF, et al. Steroidal contraceptives: effect on bone fractures in women. Cochrane Database Syst Rev 2006;(4):CD006033. [7] Chaiamnuay S, Saag KG. Postmenopausal osteoporosis. What have we learned since the introduction of bisphosphonates? Rev Endocr Metab Disord 2006; 7(1–2):101–12. [8] World Health Organization Study Group. Assessment of fracture risk and its application to screening for postmenopausal osteoporosis. Report no 843. Geneva (Switzerland): World Health Organization; 1994. [9] Black DM, Arden NK, Palermo L, et al. Prevalent vertebral deformities predict hip fractures and new vertebral deformities but not wrist fractures. Study of osteoporotic fractures research group. J Bone Miner Res 1999;14(5):821–8.
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[37] Pradhan BB, Bae HW, Kropf MA, et al. Kyphoplasty reduction of osteoporotic vertebral compression fractures: correction of local kyphosis versus overall sagittal alignment. Spine 2006;31(4):435–41. [38] Grohs JG, Matzner M, Trieb K, et al. Minimal invasive stabilization of osteoporotic vertebral fractures: a prospective nonrandomized comparison of vertebroplasty and balloon kyphoplasty. J Spinal Disord Tech 2005;18(3):238–42. [39] Hulme PA, Krebs J, Ferguson SJ, et al. Vertebroplasty and kyphoplasty: a systematic review of 69 clinical studies. Spine 2006;31(17):1983–2001. [40] Cortet B, Cotton A, Boutry N, et al. Percutaneous vertebroplasty in the treatment of osteporotic vertebral compression fractures: an open prospective study. J Rheumatol 1999;26:2222–8. [41] Bhatia C, Barzilay Y, Krishna M, et al. Cement leakage in percutaneous vertebroplasty: effect of preinjection gelfoam embolization. Spine 2006;31(8): 915–9. [42] Schmidt R, Cakir B, Mattes T, et al. Cement leakage during vertebroplasty: an underestimated problem? Eur Spine J 2005;14(5):466–73 [Epub 2005 Feb 3].
et al [43] Taylor RS, Taylor RJ, Fritzell P. Balloon kyphoplasty and vertebroplasty for vertebral compression fractures: a comparative systematic review of efficacy and safety. Spine 2006;31(23):2747–55. [44] Liebschner MA, Rosenberg WS, Keaveny TM, et al. Effects of bone cement volume and distribution on vertebral stiffness after vertebroplasty. Spine 2001; 26:1547–54. [45] Grados F, Depriester C, Cayolle G, et al. Long-term observations of vertebral osteoporotic fractures treated by percutaneous vertebroplasty. Rheumatology (Oxford) 2000;39:1410–4. [46] Harrop J, Reinhardt M, Lieberman IH, et al. Steroid-induced secondary osteoporosis: relationship to subsequent compression fractures after kyphoplasty. Read at the Annual Meeting of the North American Spine Society. Montreal, Quebec, Canada, October 29–November 2, 2002. [47] Pflugmacher R, Schroeder RJ, Klostermann CK. Incidence of adjacent vertebral fractures in patients treated with balloon kyphoplasty: two years’ prospective follow-up. Acta Radiol 2006;47(8): 830–40.
Vertebroplasty and Kyphoplasty for the Management of Osteoporotic Vertebral Compression Fractures Dhruv B. Pateder, MDa,*, A. Jay Khanna, MDb, Isador H. Lieberman, MD, MBA, FRCSCc a Steadman Hawkins Clinic, 181 West Meadow Drive, Suite 400, Vail, CO 81657, USA Johns Hopkins Orthopaedic Surgery at Good Samaritan Hospital, 5601 Loch Raven Boulevard, Suite G-1, Baltimore, MD 21239, USA c Department of Orthopaedic Surgery, Cleveland Clinic Spine Institute, A-41, The Cleveland Clinic Foundation, 9500 Euclid Ave., Desk A-41, Cleveland, OH 44195, USA b
Osteoporosis is a bone condition marked by a decrease in bone mass and density [1]. The pathophysiology of this condition is marked by an imbalance between bone production (by osteoblasts) and bone resorption (by osteoclasts) [1]. In normal bone, these two processes are tightly regulated and there is a balance between bone resorption and formation; however, in osteoporotic bone, there is an increase in osteoclastic bone resorption due to an overall decrease in osteoblastic bone production or a direct increase in bone resorption (ie, tumor cells directly stimulating osteoclasts) [1]. There are categories of osteoporosis: primary, secondary, and idiopathic [1]. Primary osteoporosis is further subdivided into senile and postmenopausal osteoporosis. Senile osteoporosis is a gradual decrease in bone mass that begins in all people during midadulthood and continues until death; it is due to a decrease in osteoblastic formation leading to a relative decrease in bone formation. Postmenopausal osteoporosis is marked by rapid bone loss that begins after menopause due to the loss of estrogen and its inhibiting effect on osteoclasts [1–3]. This process occurs concomitantly with senile osteoporosis and leads to very rapid bone loss [1–3]. Secondary osteoporosis is the result of any age-independent factors that lead to bone loss, Drs. Lieberman and Khanna are consultants for Kyphon, Inc. * Corresponding author. E-mail address: [email protected] (D.B. Pateder).
such as corticosteroids, diabetes, secondary amenorrhea, and so forth [1]. Idiopathic osteoporosis is a condition in which there is abnormal bone loss without any identifiable causative factors. There are over 26 million women in the United States affected by osteoporosis and over 700,000 pathologic vertebral body compression fractures annually (with thoracic and lumbar locations occurring most commonly) [4,5] (Fig. 1). With more than 25% of women over age 65 years sustaining a vertebral compression fracture, it is the most common complication of osteoporosis [6]. Vertebral compression fractures can be divided into two different morphologic types. The first type is the commonly encountered acute crush fracture, whereby the patient experiences sudden onset of pain and muscle spasm after some sort of minor or major trauma [1,6]. These fractures can sometimes be difficult to differentiate from pathologic fractures and may require a biopsy [7]. The second type is a minimally symptomatic anterior wedge compression fracture that occurs over multiple levels in time and leads to a kyphotic deformity and a loss of height [1,7]. Although vertebral fractures are the most common osteoporotic fractures, proximal femoral neck fractures are associated with the highest mortality [3,8]. Given the grave prognostic implications of femoral neck fractures on ambulation and overall health, patients who have hip fractures undergo operative fixation in an urgent manner; however, until recently, vertebral body compression fractures have been treated with
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Fig. 1. Lateral radiograph demonstrating a compression fracture of a thoracic vertebra.
medical management or benign neglect unless there was gross loss of spinal balance or an associated neurologic deficit [9–12]. Traditionally, this treatment was the case because vertebral compression fractures did not have any immediate effect on ambulation, and surgery to restore height and alignment meant subjecting the patient to the tremendous morbidity of thoracotomy or abdominal surgery in addition to the inherent problems associated with repairing brittle osteoporotic bone. Over time, however, it has become clear that approximately one third of vertebral compression fractures go on to become chronically painful [13]. In addition, several studies have shown that disturbance of the normal sagittal balance can lead to further back pain and have a negative effect on the ability to participate in the activities of daily living [14,15].
Percutaneous vertebral body augmentation Given the detrimental effects of nonoperative care and the morbidity associated with open reduction and internal fixation of vertebral compression fractures, there have been recent advances in minimally invasive modalities to address these fractures. Over the past 2 decades, vertebroplasty (a procedure in which polymethylmethacrylate [PMMA] is percutaneously injected into the vertebral body) was developed as a way to stabilize vertebral compression fractures without inducing the morbidity and mortality associated with open surgery [16]. More recently, kyphoplasty has been developed to address vertebral compression fractures [17]. Kyphoplasty is differentiated from vertebroplasty in that kyphoplasty
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involves inserting an inflatable balloon in the vertebral body to elevate the vertebral end plates; PMMA is then inserted in this cavity [18]. The theoretic advantages of this procedure over vertebroplasy include its ability to restore vertebral height and kyphosis and to allow for the more controlled deposition of the PMMA in a cavity, thus decreasing the risk for cement extravasation. Although vertebroplasty and kyphoplasty have been shown to reduce the back pain of vertebral compression fractures [16–19], identifying patients who would benefit from these procedures requires a thorough workup incorporating the findings of history, physical examination, and imaging studies [18]. Clinicians need to be extremely careful in correlating a patient’s back pain with the compression fracture. Most patients who have acute compression fractures report a sudden onset of back pain that may or may not be associated with a traumatic event. Because many of these patients have severe osteoporosis, many vertebral compression fractures occur with simple activities such as bending down or getting up from a seated position. On physical examination, patients who have acute compression fractures tend to have tenderness directly over the fracture site. This is an important finding because it helps differentiate back pain associated with compression fractures from ‘‘low back pain’’ [17]. Posteroanterior and lateral radiographs are very useful in detecting most vertebral compression fractures and the overall spinal column alignment; however, it is often difficult to differentiate whether the fracture is acute or chronic or whether it is a pathologic fracture. MRI is an excellent imaging modality because not only can it demonstrate the edema associated with acute compression fractures, but it can also detect any tumorous lesions that may have caused the fracture or may be present in other vertebral bodies. Special care should be taken to evaluate the sagittal T2-weighted and fat-suppressed T2-weighted or the short tau inversion recovery images (Fig. 2). These images show increased signal intensity at the fracture site in patients who have acute and subacute fractures and, thus, allow for selection of those patients more likely to experience pain relief after a vertebral augmentation procedure [20]. Patients who demonstrate no increased signal intensity on these images are unlikely to experience pain relief after vertebral augmentation. For patients who have a contraindication to MRI evaluation (ie, presence of a pacemaker or claustrophobia), nuclear scintigraphy (bone scan) can be used to evaluate the acuity and physiologic activity at the fracture site.
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Fig. 2. A fat-suppressed T2-weighted MRI demonstrating a compression fracture (high signal) of a lumbar vertebra.
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[23] recently demonstrated the long-term (24 months) efficacy of kyphoplasty on back pain relief, back function, and quality of life in a prospective, multicenter study of 155 patients. It is unfortunate that this study did not have a nonoperative control group; however, the presence of a vertebral collapse predicted increased mortality and a fivefold increase in further fractures at adjacent or remote levels within 1 year [19]. Some contraindications for these percutaneous procedures include fractures associated with neurologic injury, fractures with a burst component, a fracture with a cleft or fracture plane that extends into the spinal canal, and healed, chronic compression fractures [18]. In patients who have severe cardiac disease, percutaneous vertebral augmentation also poses an additional risk that is cumulative for each added level because the PMMA contains a vasodilatory agent that is rapidly absorbed systemically [18]. Technique of vertebroplasty
Selection criteria It is important for the physician to treat only the symptomatic fractures and not to treat all fractures seen on imaging studies, because most evidence suggests that healed fractures are stable and do not cause pain [18,21]. Indications for vertebroplasty and kyphoplasy in the treatment of vertebral compression fractures include acute, painful osteporotic or osteolytic vertebral compression fractures; isolated vertebrae with metastatic lesions that are causing pain; painful vertebral hemangioma; and Ku¨mmell’s disease [18]. Similar to any other fragility fracture, the goals are to restore stability, anatomic alignment, and function as soon as safely possible. Although it is well-documented that 66% of patients who have vertebral compression fractures become asymptomatic after several months, it is important to remember that these fractures heal in a malaligned position where the vertebral height and the fractured vertebra’s relationship to adjacent vertebrae have been compromised [13,16]. A recent study by Diamond and colleagues [22] found that vertebroplasty for acute compression fracture was significantly better than nonoperative treatment in terms of pain relief, level of function, and hospital stay. Of interest, there were no differences in pain relief between the two groups at 12 and 24 months after the procedure. In addition, there was no significant difference between the two groups in the rates of new vertebral fractures or death. Similarly, Garfin and associates
Percutaneous vertebroplasty was started in France in 1984, introduced by Galibert and colleagues [24] in 1987, and subsequently introduced in the United States in 1993 [16]. Vertebroplasty is performed with the patient in a prone position with bolsters under the sternum and pelvis to reduce kyphosis at the fractured vertebra [3]. Although this procedure can be performed under local anesthetic for one or two levels, it is usually performed under general anesthesia in patients undergoing multiple-level vertebroplasty or who will not be able to stay still during the procedure if done under local anesthesia [17]. Fluoroscopy is used to identify the pedicles and end plates of the vertebrae in its true anteroposterior (AP) and lateral dimensions so that there is no parallax. This step is perhaps one of the most important in the procedure because it allows the most accurate and thus safest placement of the cannulas and other instruments. An extrapedicular or a transpedicular approach can be used to enter the vertebral body from its posterior aspect as described previously [17]. Both approaches have been shown to be safe and efficacious. A common practice is to use a transpedicular approach when the pedicles are larger, such as in the lumbar spine and lower thoracic spine, and an extrapedicular approach in the mid and upper thoracic spine. During vertebroplasty, PMMA is injected in a more fluid state because there is no cavity created for it and the cement permeates into the
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cancellous bone of the fractured vertebra. It is extremely important to inject the barium-impregnated cement under live fluoroscopy or while using multiple single-frame fluoroscopic views. If there is any extravasation of the cement from the vertebral body, particularly posteriorly toward the spinal canal, then the procedure must be immediately halted and the situation assessed. A certain degree of cement extrusion from the vertebra can be tolerated without any deleterious effects to the patient, but there have been reported cases in which cement extrusion has caused neurologic damage [18]. Although initial studies
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suggested that there was no fracture reduction or height restoration with this technique, more recent studies have demonstrated that fracture reduction and height restoration are achieved due to the dynamic mobility of the acute fracture (Fig. 3) [25]. Although there is no consensus on the definitive mechanisms for pain control, it is probably achieved by way of a multitude of pathways including fracture stabilization as the cement hardens and heat necrosis of the nerve endings at the fracture site. Some investigators have suggested that some height restoration can be achieved in vertebroplasty by putting the trocar
Fig. 3. Preoperative AP (A) and lateral (B) radiographs demonstrating a L1 compression fracture. (C) Sagittal fat-suppressed T2-weighted MR image demonstrating the compression fracture. Postoperative AP (D) and lateral (E) radiographs after a kyphoplasty of the L1 vertebra.
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in the fracture cleft and extending at the site, thus opening up the fracture [3]; however, there are no studies confirming this. One of the dangers of this maneuver is that the open cleft can allow cement to escape from the confines of the vertebral body and into the surrounding tissue. As a result, one must be extremely careful with this maneuver and may consider performing a kyphoplasty if height restoration is desired. Technique of kyphoplasty Similarly to vertebroplasty, kyphoplasty begins with prone positioning on a radiolucent table with bolsters and by using biplanar fluoroscopy to identify the anatomic landmarks on true AP and lateral views. Entry into the vertebral body is performed similarly by way of an extrapedicular or transpedicular approach as described previously [17]. Unlike vertebroplasty, however, after the cannula is appropriately placed in the vertebral body, a hand drill is placed through the cannula, with the goal being that the drill tip is eventually placed just posterior to the anterior vertebral cortex on the lateral view and past the midline on the AP view. On the lateral view, when the drill is midway across the vertebral body, an AP image should be obtained; on the AP view, the drill should be midway between the pedicle and spinous process. If it is closer to the spinous process than this, then there is a chance that it could be in the spinal canal; similarly, if it is too close to the pedicle on the AP view, then it may be out laterally. After
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the appropriate track is created, the drill can be removed. The drilling allows for the creation of a pathway for the placement of the inflatable balloon tamp. The balloon is placed in the cavity and inflated using a manometer with a digital pressure gauge (Fig. 4). The balloon contains saline with barium in it such that it may be visualized under fluoroscopy as it is inflated. It is recommended that it be inflated under live fluoroscopy to ensure that it does not malreduce the fracture or fracture the vertebral end plate. When two balloons are to be used, most surgeons first place them both and then inflate them at the same time or alternately (‘‘backand-forth’’) to prevent ‘‘herniation’’ of the first balloon to the contralateral side, thus preventing ideal placement of the second balloon. When only one balloon is to be used, the balloon can be deflated and the cement (mixed with barium) deposited into the cavity under live fluoroscopy in a retrograde fill pattern, from the ventral aspect of the cavity to its dorsal aspect (Fig. 5A, B). The consistency of the cement used for kyphoplasty is different than it is for vertebroplasty. For vertebroplasty, the cement must be in a more liquefied state to permeate and spread into the vertebral cancellous bone, whereas for kyphoplasty, it can be in a more viscous or ‘‘doughy’’ state because it is deposited in a cavity created by the balloon. The surgeon should be aware of the setting times of the cement before performing a clinical case, and usually the cement is ready to be injected for kyphoplasty when it no longer
Fig. 4. Intraoperative AP (A) and lateral (B) fluoroscopic images demonstrating balloon placement in the vertebra during a kyphoplasty procedure. (C) After the balloon is in satisfactory position, it is inflated to create a cavity for the cement.
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Fig. 5. (A,B) After the balloon is deflated and removed, cement (mixed with barium) is deposited into the cavity under live fluoroscopic guidance in a retrograde fill pattern (from the ventral aspect of the cavity to its dorsal aspect). Final AP (C) and lateral (D) radiographs are taken to evaluate cement position and overall alignment.
sticks to the surgeon’s gloves. The volume of liquid used to inflate the balloon provides a general idea about the quantity of cement that will be required for each level. When ready to fill, the inflatable bone tamp is deflated and the balloon is carefully removed. A cement cannula is advanced to the anterior aspect of the vertebral body by passing it through the working cannula. Fluoroscopy is used to confirm the location of the cannula. When the cannula is in a satisfactory position, cement is slowly ejected by pushing it out of the cannula with a blunt probe. As more cement is ejected into the cavity, the cement cannula should be pulled back slightly to allow cement to be injected into the posterior aspect of the cavity. The cement generally does not extravasate unless it is too thin or there has
been a breach in the vertebral cortex. When a cement leak (out of the intended cavity) is detected, injection should be stopped immediately and the cement allowed to harden for 1 to 2 minutes before slowly injecting again under live fluoroscopic guidance. When the cement is hardened, the cannula can be removed and final imaging views can be taken (see Fig. 5C, D).
Results Vertebroplasty and kyphoplasty are highly successful procedures when it comes to relieving the pain associated with vertebral compression fractures [26–33]. Patients undergoing vertebroplasty experience pain relief within 72 hours and
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have reported consistent pain relief for up to 10 years after the procedure [21]. Studies have also reported an improvement in functional outcomes and analgesic requirements after vertebroplasty. Similarly, Garfin and colleagues [34] reported that 90% of 1439 patients treated with kyphoplasty reported significant pain relief within 2 weeks after undergoing the procedure. Lieberman and colleagues [17] and, more recently, several different investigators [26] have reported significant improvement in overall SF-36 function scores in a large group of patients who had undergone kyphoplasty. In a review of patients undergoing kyphoplasty, Phillips and colleagues [28] noted that visual analog scores also improved from 8.6 preoperatively to 2.6 at 1week postoperatively and to 0.6 at 1 year postoperatively in patients undergoing kyphoplasty. Kyphoplasty affords deformity correction at the fractured vertebra and has been found to correct up to 97% of the deformity (compared with 30% with vertebroplasty) in an ex vivo model [35]. Numerous clinical studies have also demonstrated the ability of kyphoplasty to restore vertebral height anywhere from 50% to 70% and to improve the sagittal angulation at the fracture site [17,27,28,34]. A recent study by Shindle and colleagues [36] demonstrated that fracture reduction with kyphoplasty was 46.6% better than postural reduction with extension positioning alone. Of interest, Pradhan and colleagues [37] found that although kyphoplasty can restore height at the fractured vertebra, it did not lead to an improvement in overall sagittal balance. In a prospective study of patients who had reducible nonacute vertebral fracture with kyphotic deformity, Grohs and colleagues [38] found that although vertebroplasty and kyphoplasty were effective in reducing pain in the short-term, kyphoplasty had a longer-lasting effect on pain relief and activities of daily living compared with vertebroplasty. The investigators attributed this effect to restoration of sagittal balance and its secondary effect on reducing the work and subsequent fatigue of the paraspinal musculature [38]. In a very systematic and well-designed meta-analysis of 69 studies (37 retrospective, 25 prospective, and 7 nonreported study designs), Hulme and associates [39] found that vertebroplasty and kyphoplasty were similar with regard to pain relief (87% of patients for vertebroplasty versus 92% of patients for kyphoplasty), vertebral height restoration (6.6 for both), and refracture rates. The only difference between the two groups was the
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rate of cement extravasation, occurring in 41% of the vertebroplasty patients versus 9% of the kyphoplasty patients.
Complications Although complications are very rare after vertebral augmentation procedures, there have been reports of cement leakage and neurologic injuries with both procedures. Extravertebral cement extrusion has been reported to be as high as 65% with vertebroplasty, and although this is usually clinically asymptomatic, cases of spinal cord and nerve root injuries have been reported [18,27–29,40]. A recent study in 2006 by Bhatia and colleagues [41] found asymptomatic cement leaks in 22.5% of osteoporotic vertebral fractures that underwent percutaneous vertebroplasty. With kyhoplasty, extravertebral cement extrusion has been reported to be as high as 10% in several different studies without any clinical consequences or leakage into the spinal canal [18,27–29]. In an interesting study by Schmidt and colleagues [42], it was discovered that only 34% of intraoperative cement leaks are discovered using lateral fluoroscopy and that by using AP and lateral fluoroscopy, the detection rate increases to 48%. In other prospective multicenter studies, a major complication rate of 1.1% has been reported; of these complications, 0.75% were neurologic complications [18].
Kyphoplasty versus vertebroplasty Although kyphoplasty and vertebroplasty have been shown to provide excellent pain relief, there is still a great deal of debate regarding which of the two procedures is ‘‘better.’’ One should keep in mind that the two procedures are not mutually exclusive and that they may be used for specific fracture types and indications to provide a spectrum of treatment that ranges from stabilization of the vertebral body to reduction and reconstruction of the fracture and spinal column. One of the most significant advantages of kyphoplasty over vertebroplasty is that it has now been shown in multiple studies to restore lost vertebral body height, thus preventing kyphosis at that level and its potential long-term implications [17,28,34,35]. Ledlie and colleagues [27] reported height restoration from radiographic measures of anterior and midline points of the fractured vertebra using the two nearest normal vertebrae as
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reference points [27,34]. Ledlie and colleagues [27] reported that one year after kyphoplasty, the anterior vertebral height restoration was maintained at 20% greater than preoperative height, whereas midline height was maintained at 16% greater than preoperative height. Similarly, Phillips and colleagues [28] reported that sagittal alignment in kyphoplasty patients improved between 8.8 and 14.2 in vertebral compression fractures. The other potential advantage of kyphoplasty over vertebroplasty is the lower reported rates of cement extravasation as previously discussed. It is important to note, however, that most of the cement extravasations seen with vertebroplasty have little or no clinical significance. The longterm implication of the differences in cement extravasation is unknown. In a meta-analysis of 75 studies, Taylor and colleagues [43] cited the overall excellent benefit-to-harm ratio of vertebroplasty and of kyphoplasty and suggested that the higher cement extravasation rate and the adverse event rate (pulmonary embolism and neurologic injury) give vertebroplasty a slightly lower benefit-to-harm ratio than kyphoplasty. Biomechanical studies have found that cement augmentation leads to increased stiffness in that vertebral body and can lead to altered forced distribution in the adjacent vertebrae, thus increasing the chances of additional osteoporotic compression fractures [44]. Although data regarding adjacent-level fractures after vertebroplasty or kyphoplasty are limited, Grados and colleagues [45] reported a 52% incidence of remote or adjacentlevel vertebral compression fractures after vertebroplasty. The incidence of this phenomenon seems to be lower after kyphoplasty, with one study reporting an approximate 11% incidence of adjacent-segment fractures in primary osteoporotic patients [46]. Similarly, Phillips and colleagues [28] reported new adjacent-level compression fractures in 3 of 29 patients who underwent kyphoplasty for osteoporotic compression fractures. In the most current study, Pflugmacher and colleagues [47] reported a 10% annual refracture rate after kyphoplasty. These results suggest that kyphoplasty is perhaps less prone than vertebroplasty to cause adjacent-level compression fractures by more effectively restoring the overall spinal balance.
Summary Although osteoporotic vertebral compression fractures were treated nonoperatively in the past
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due to the substantial morbidity of open surgery, they can now be stabilized using relatively benign minimally invasive techniques. Vertebral augmentation by vertebroplasty or kyphoplasty is clearly an effective treatment for painful progressive osteoporotic compression fractures. Although each technique has its own advantages and disadvantages, numerous studies have shown that the techiniques are similar with regard to functional outcomes and short-term improvement in pain. Although each technique has its supporters and critics, both techniques have unique advantages and disadvantages that afford them a vital role in the treatment of osteoporotic compression fractures. Future studies directly comparing different aspects of these two techniques will elucidate whether one is superior to the other or whether the choice of procedure should be made based on the fracture configuration or other clinical or radiographic parameters. References [1] McCarthy EF, Frassica FJ. Metabolic bone disease. In: Frassica FJ, McCarthy EF, editors. Pathology of bone and joint disorders. Philadelphia: WB Saunders Company; 1998. p. 88–99. [2] Silver JJ, Einhorn TA. Ostoporosis and aging. Clin Orthop 1995;316:10–20. [3] Rao RD, Singrakhia MD. Painful osteoporotic vertebral facture: pathogenesis, evaluation, and roles of vertebroplasty and kyphoplasty in its management. J Bone Joint Surg Am 2006;85(10):2010–22. [4] Melton LJ III, Kan SH, Frye MA, et al. Epidemiology of vertebral fractures in women. Am J Epidemiol 1989;129:1000–11. [5] Cooper C, Atkinson EJ, O’Fallon WM, et al. Incidence of clinically diagnosed vertebral fractures: a population-based study in Rochester, Minnesota, 1985–1989. J Bone Miner Res 1992;7:221–7. [6] Lopez LM, Grimes DA, Schulz KF, et al. Steroidal contraceptives: effect on bone fractures in women. Cochrane Database Syst Rev 2006;(4):CD006033. [7] Chaiamnuay S, Saag KG. Postmenopausal osteoporosis. What have we learned since the introduction of bisphosphonates? Rev Endocr Metab Disord 2006; 7(1–2):101–12. [8] World Health Organization Study Group. Assessment of fracture risk and its application to screening for postmenopausal osteoporosis. Report no 843. Geneva (Switzerland): World Health Organization; 1994. [9] Black DM, Arden NK, Palermo L, et al. Prevalent vertebral deformities predict hip fractures and new vertebral deformities but not wrist fractures. Study of osteoporotic fractures research group. J Bone Miner Res 1999;14(5):821–8.
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