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A comparison of high viscosity bone cement and low viscosity bone cement vertebroplasty for severe osteoporotic vertebral compression fractures
Clinical Neurology and Neurosurgery 129 (2015) 10–16
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Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
A comparison of high viscosity bone cement and low viscosity bone cement vertebroplasty for severe osteoporotic vertebral compression fractures Liang Zhang, Jingcheng Wang, Xinmin Feng ∗ , Yuping Tao, Jiandong Yang, Yongxiang Wang, Shengfei Zhang, Jun Cai, Jijun Huang Department of Orthopedics, Clinical Medical College of Yangzhou University, Subei People’s Hospital of Jiangsu Province, No.98 Nantong West Road, Yangzhou, Jiangsu 225001, China
a r t i c l e
i n f o
Article history: Received 19 October 2014 Received in revised form 15 November 2014 Accepted 27 November 2014 Available online 4 December 2014 Keywords: Severe osteoporotic vertebral compression fractures Vertebroplasty Bone cement Viscosity Leakage
a b s t r a c t Objective: To compare the clinical outcome and complications of high viscosity and low viscosity polymethyl methacrylate bone cement PVP for severe OVCFs. Methods: From December 2010 to December 2012, 32 patients with severe OVCFs were randomly assigned to either group H using high viscosity cement (n = 14) or group L using low viscosity cement (n = 18). The clinical outcomes were assessed by the Visual Analog Scale (VAS), Oswestry Disability Index (ODI), Short Form-36 General Health Survey (SF-36), kyphosis Cobb’s angle, vertebral height, and complications. Results: Significant improvement in the VAS, ODI, SF-36 scores, kyphosis Cobb’s angle, and vertebral height were noted in both the groups, and there were no significant differences between the two groups. Cement leakage was seen less in group H. Postoperative assessment using computed tomography identified cement leakage in 5 of 17 (29.4%) vertebrae in group H and in 15 of 22 (68.2%) vertebrae in group L (P = 0.025). Conclusions: The PVP using high viscosity bone cement can provide the same clinical outcome and fewer complications compared with PVP using low viscosity bone cement. © 2014 Published by Elsevier B.V.
1. Introduction Osteoporotic vertebral compression fractures (OVCFs) are the most common types of osteoporotic fracture in the elderly population, causing back pain and loss of mobility due to the resulting spinal deformities [1–4]. Traditional conservative therapy includes bed rest, use of analgesics, physiotherapy, and external bracing. However, many patients may still complain of severe pain not responding to these therapies and even exhibiting progressive kyphosis and collapse of the vertebral body [5–7]. The classical open surgery with different types of metal implants is not an optimal treatment for a majority of patients due to the poor quality of osteoporotic bone and associated comorbidities. Percutaneous vertebroplasty (PVP) has gained popularity as a treatment modality for OVCFs, providing nearly immediate pain relief and mechanical strengthening of the vertebral body with low incidence of adverse events and morbidity [8–10].
∗ Corresponding author. Tel.: +86 18952578137; fax: +86 514 87373315. E-mail address: [email protected] (X. Feng). http://dx.doi.org/10.1016/j.clineuro.2014.11.018 0303-8467/© 2014 Published by Elsevier B.V.
The severe OVCF, refers to part of the vertebral body collapsed to less than one-third of its original height, has been cited as relative or even absolute contraindication by many authors for technical difficulties to perform and resultant high risk of cement leakage [11–14]. Some studies have reported the sustained efficacy of PVP treating severe OVCFs with advances in medical devices and imaging [11,12,15,16]. However, cement leakage, ranging from 43% to 45% detected by an X-ray to 78% to 91.9% detected by computed tomography (CT) scan, is still the main risk of complication for PVP with conventional low viscosity cement [11,16,17]. While most leakages are clinically asymptomatic, serious complications occurred in 3.9–7.5% of the patients who underwent PVP. If the cement leakages cause neurologic deficits, abdominal thromboembolisms, and pulmonary embolism, induction of new adjacent vertebral fractures by intradiscal cement leakage is suggested [18–21]. To reduce cement leakages, adequate patient selection, technical improvement, and its implementation such as accurate imaging in the hands of skilled operators were recommended, but the results were not conclusive [11,12,22]. Viscosity, the main characteristic parameter of the polymethyl methacrylate (PMMA) bone
L. Zhang et al. / Clinical Neurology and Neurosurgery 129 (2015) 10–16
cement, has been demonstrated to be the key influencing factor for leakage when PVP technique and radiological equipment are optimal. High viscosity cements have been demonstrated to effectively reduce the risk for extravasation, thereby improving overall clinical safety, and improve infiltration and restore height. Baroud et al. demonstrated that cement leakage ceased completely when its viscosity was very high in their experimental model [23]. Georgy and Anselmetti further confirmed that high viscosity cement is safe in application and may increase the safety of vertebral augmentation techniques compared with less viscous cements, in a prospective clinical study [24,25]. These cements reach a constant putty-like viscosity immediately after mixing, without a waiting period of few minutes as in other cements, and remain consistently injectable for 8–10 min before these cements solidify. The objective of this prospective randomized controlled study was to evaluate and compare the clinical outcomes and cement leakage of high viscosity PMMA bone cement versus low viscosity cement PVP in treating severe OVCFs. To our knowledge, no other report has been published on this comparison. 2. Materials and methods This was a prospective randomized controlled study, approved by the Institutional Review Board. From December 2010 to December 2012, a total of 32 patients with severe OVCFs adopting PVP were included in the present study. Written consent to participate in the study was obtained from each patient. Patients were included in the study if they (1) were aged above 50 years, (2) had severe OVCFs (part of the vertebral body collapsed to less than one-third of their original height), (3) had focal back pain without definite radicular signs and symptoms unresponsive to at least 8 weeks of appropriate conservative treatment, (4) had back pain related to the location of the OVCF on spinal radiographs, (5) were diagnosed to have an apparent bone edema in the fractured vertebra on magnetic resonance imaging (MRI) T2-weighted short tau inversion recovery sequences, and (6) had decreased bone mineral density (T scores < −1). Patients were excluded if they (1) had ordinary OVCFs (vertebral body collapsed to more than onethird of their original height), (2) had spinal cord compression or stenosis of the vertebral canal >30% of the local canal diameter, (3) had neurologic deficits, (4) had uncorrectable bleeding disorders, (5) had systemic or local spine infections, and (6) had severe comorbidity in the heart, liver, kidney, and lung intolerance to surgery. After enrollment, the patients were given a serial number according to the consecutive sequence of hospitalization and were assigned to either group H (used high viscosity cement) or group L (used low viscosity cement) randomly by computer according to the serial number. The study population consisted of 14 patients in the group H (mean age, 75.5 ± 9.3 years) and 18 patients in the group L (mean age, 75.8 ± 9.3 years). All procedures were performed by the same surgeon. 2.1. Radiological evaluation All patients underwent preoperative plain radiography, CT construction, MRI, and dual-energy X-ray absorptiometry for testing bone mineral density. Changes in marrow signal were assessed using MRI to determine the symptomatic levels of the fracture. Bone scans were used in cases where MRI was contraindicated (e.g. presence of a pacemaker). All radiological assessments were evaluated by two radiologists who were unaware of the clinical presentation and its outcome in the patients. The extent of vertebral body collapse was measured from the height of the maximum collapse on lateral radiographs. The percentage of collapse, compared with the normal vertebral body
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height, was then calculated. Anterior and middle vertebral heights were defined as the distance between the upper and lower endplates at the anterior vertebral body wall and in the centre of the vertebral body, respectively. Normal heights of the anterior and midvertebra were defined as the mean of the equivalent values for the adjacent superior and inferior nonfractured vertebrae. Variation in vertebral body height was then calculated by fractured vertebral body height/normal vertebral body height × 100%. The kyphosis Cobb’s angle was assessed by measuring the kyphotic angle from the superior endplate of the vertebral body one level above the injury to the inferior endplate of the vertebral body one level below. 2.2. Procedural technique The procedure was performed under general anesthesia to provide a certain comfort, especially during the progression of the trocar, which can be painful. Patients were placed in a prone position and monitored by electrocardiograph and oxygen saturation during the procedures. After localizing the fractured vertebra using fluoroscopy, the surgeon placed overlapping palm on the vertebral spinous process to push toward ventral slowly for partial reduction of the fractured vertebra. Through a 0.5-cm-sized skin incision, the vertebroplasty needles were advanced to obtain bilateral transpedicular access until its tip reached the junction of the anterior and middle one-third of the vertebral body under C-arm fluoroscopic guidance. In cases where pedicles were not visualized on fluoroscopy, the parapedicular or unipedicular approach was used. Once the needle position was satisfactory, high viscosity cement (Confidence; DePuy Spine, Raynham, MA) or low viscosity cement (Vertebroplastic; DePuy Acromed, Raynham, MA) was injected into the vertebral body using continuous fluoroscopic guidance. Depending on the ambient temperature of the operation room, the time from the beginning of mixing to the beginning of application of low viscosity cement was 4–8 min, while high viscosity cement could be applied immediately after mixing for 30 s. The injection of cement was stopped whenever epidural or paravertebral opacification was observed or the cement reached the dorsal quarter of the vertebral body. The needles were not removed before the end of polymerization to prevent spreading of low viscosity cement, while the needles were removed immediately after the application of high viscosity cement (due to its high viscosity there was no possibility of cement leakage from the needles into the surrounding area). 2.3. Assessment of outcomes Patients were followed up postoperatively, and at 3 days, 3, 12, and 18 months after surgery. The Visual Analog Scale (VAS) score was used to evaluate back pain, Oswestry Disability Index (ODI) was used as a functional assessment, and Short Form-36 General Health Survey (SF-36) was used to evaluate the quality of life. Any clinical complications were recorded immediately after the procedure. Cement leakage, defined as the presence of any extravertebral cement, was assessed independent of the treating physician by two investigators using the CT scan. The position of any cement leakage was noted and was correlated with any symptoms reported during the follow-up period. 2.4. Statistical analysis Data were presented as the mean ± standard deviation. The SPSS for Windows Version 13.0 (SPSS, Chicago, IL) was used for the analysis. Intergroup comparisons were made using the Student’s paired t-test or Chi-square test. Comparisons between before and after operation were made using the Student’s paired t-test. The
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Table 1 Surgical parameters of the studied population.
Patients Male/female Age(years) Vertebral bodies(n) Operative time Injected cement volume Unipedicular/bipedicular approach
Group H
Group L
14 2:12 75.5 ± 9.3 17 41.8 ± 9.0 3.4 ± 1.0 4:13
18 3:15 75.8 ± 9.3 22 44.8 ± 12.5 3.5 ± 0.8 6:16
P-value 1.00 0.93 0.46 0.67 1.00
difference in proportions of cement leakage between the two groups was assessed using the Fisher’s exact test. P-values < 0.05 were considered statistically significant. 3. Results There were no significant differences between group H and group L in the gender ratios, age, and vertebral bodies involved according to the statistical results (Table 1). The mean follow-up duration was 24.5 months (range, 18–42 months). There was no statistical difference between the two groups according to the mean surgery time/vertebrae (P = 0.46) and mean injected cement volume/vertebrae (P = 0.67). Of 17 vertebrae in group H, PVP was unipedicular in 4 (23.5%) cases and bipedicular in 13 (76.5%), whereas the procedure was unipedicular in 6 (27.3%) cases and bipedicular in 16 (72.7%) of 22 vertebrae in group H, with no statistical difference (P = 1.00). These results are presented in Table 1. The two groups reported immediate postoperative pain relief, and none had subjective complaints of worsening pain at any time point of follow-up. The mean preoperative VAS score was 8.4 and 8.6, which significantly decreased to 2.2 and 1.9 at 18 months follow-up in group H and group L, respectively (P < 0.01) (Table 2). The mean preoperative ODI score was 73.9% and 75.5%, which significantly improved to 29.8% and 32.8% at 18 months follow-up in group H and group L, respectively (P < 0.01) (Table 2). The mean preoperative physical component score (PCS) of the SF-36 score was 32.1 and 31.6, which significantly improved to 50.5 and 48.8 at 18 months follow-up in group H and group L, respectively (P < 0.01). The mean preoperative mental component score (MCS) of the SF-36 score was 31.9 and 31.3, which significantly improved to 46.7 and 45.2 at 18 months follow-up in group H and group L, respectively (P < 0.01) (Table 2). However, there were no significant differences between group H and group L in VAS score, ODI score, and SF-36 score preoperatively and at 18 months follow-up (Table 2). The variation in the anterior vertebral height significantly increased from preoperative (30.8%) to postoperative (51.9%) period in group H (P < 0.01) and from preoperative (30.3%) to postoperative (47.3%) period in group L (P < 0.01), without any statistical difference between the two groups irrespective of preoperative (P = 0.82) or postoperative (P = 0.36) period. The variation in the middle vertebral height significantly increased Table 2 Mean VAS, ODI, PCS and MCS before and after vertebroplasty comparing between the two groups. Parameter
Group H (14 pt)
Group L (18 pt)
P-value
VAS pre-OP (0–10) VAS post-OP (0–10) ODI pre-OP (0–100%) ODI post-OP (0–100%) PCS pre-OP PCS post-OP MCS pre-OP MCS post-OP
8.4 2.2 73.9 29.8 32.1 50.5 31.9 46.7
8.6 1.9 75.5 32.8 31.6 48.8 31.3 45.2
0.66 0.46 0.65 0.14 0.71 0.45 0.65 0.40
Table 3 Mean anterior vertebral body height variation, middle vertebral body height variation, Kyphosis angle before and after vertebroplasty and cement leakage comparing between the two groups. Parameter
Group H (14 pt)
Group L (18 pt)
P-value
Anterior vertebral body height variation pre-OP (%) Anterior vertebral body height variation post-OP (%) Middle vertebral body height variation pre-OP (%) Middle vertebral body height variation post-OP (%) Kyphosis angle pre-OP (◦ ) Kyphosis angle post-OP (◦ ) Cement leakage
30.8%
30.3%
0.82
51.9%
47.3%
0.36
29.7%
32.8%
0.22
45.6%
50.7%
0.24
20.8 14.8 5
19.3 14.9 15
0.40 0.94 0.025
from preoperative (29.7%) to postoperative (45.6%) period in group H (P < 0.01) and from preoperative (32.8%) to postoperative (50.7%) in group L (P < 0.01), without any statistical difference between the two groups irrespective of preoperative (P = 0.22) or postoperative (P = 0.24) period. The mean kyphosis Cobb’s angle significantly increased from preoperative (20.9◦ ) to postoperative (14.8◦ ) period in group H (P < 0.01), and from preoperative (19.3◦ ) to postoperative (14.9◦ ) period in group L (P < 0.01), without any statistical difference between the two groups irrespective of preoperative (P = 0.40) or postoperative (P = 0.94) period (Table 3). No significant clinical complications or postprocedural clinical sequelae were encountered. Postoperative assessment using CT identified cement leakage in 5 of 17 (29.4%) vertebrae in group H and in 15 of 22 (68.2%) vertebrae in group L (P = 0.025). All leakages were clinically silent and no neural compromise or pulmonary embolism was found. The adjacent vertebral fractures did not occur in either group. Pre- and postoperative images of a typical patient in group H treated with PVP using high viscosity bone cement are shown in Figs. 1 and 2. 4. Discussion OVCFs are linked with older age and are metastatic with poor general condition, leading to significant rate of morbidity and mortality, problems in lung function, nourishment disorders, reduced mobility, and psychic disorder caused by pains and drugs [1–3]. The conventional surgeries of stabilization, ostrosynthesis and lumbar fusion, had no success because of bad quality of bones [6,26]. Despite marginal understanding of the mechanism, PVP is generally considered to be a safe and effective treatment option for OVCFs [8–10]. However, severe OVCFs have always been considered as a relative or even absolute contraindication due to the technical difficulty because of the extreme kyphotic angle and the severe loss of vertebral height [27–29]. In severe OVCFs, placement of needle is more challenging, and a second needle is more frequently necessary to obtain an adequate distribution of cement as compared to the treatment of nonsevere OVCFs [12,15,30]. O’Brien et al. were able to successfully advance the needle tip to the anterior one-third of all vertebral bodies with subsequent filling of the entire vertebral body in severe OVCFs using a bipedicular, far lateral approach [15]. The present study adopted a modified technique for treating severe OVCFs with emphasis on partial reduction of the fractured vertebra before puncture to increase the operating space of the needle. In combination with a smaller gauge trocar, the needle (unipedicular/bipedicular approach) could be advanced into the fractured vertebral body while remaining lateral to the dominant portion of the vertebral body, as most patterns of fracture result in maximal central collapse, making it impossible to position the needle tip at midline.
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Fig. 1. Preoperative images of a 68-year-old woman with severe OVCFs in group H treated with PVP using high viscosity bone cement. (A) Anteroposterior and (B) lateral radiograph showing a severe compression fracture of the T12 vertebral body. (C) Coronal and (D) sagittal 2D CT reconstruction image of the T12 vertebral body showing a severe compression fracture and the most severe portion of the compression fracture located in the center of the vertebral body. (E) Sagittal MR image of the T12 vertebral body confirming the severe compression fracture. 2D, two-dimensional; CT, computed tomography; MR, magnetic resonance; OVCF, osteoporotic vertebral compression fracture; PVP, percutaneous vertebroplasty
It is unclear whether spatial distribution of the cement influenced by its viscosity affects the outcome of PVP. The results of the present study showed a clinically relevant, significant, immediate, and durable reduction in mean back pain and function, which was comparable between both the groups. Increase in quality of life, measured using the SF-36, was similar in both the groups. Thus there is no direct dependence between the quantity of cement applied and clinical outcome. Severe OVCFs often have some cleft in the vertebral wall, which increases the risk of cement leakage. Although most leakages remain clinically asymptomatic, the cement leakage is reported up to 91.9% in severe OVCFs receiving PVP [12]. A majority of leakages are cortical, with venous leakages occurring infrequently. Other cement-related severe complications include paraplegia, spinal cord and nerve root compression, cement pulmonary embolisms, and possible death [18–21]. Hence, severe OVCFs represent a unique subgroup, and additional care should be exercised with PVP in severe OVCFs. Bhatia et al. recently demonstrated that significant reduction in leakage (22.5% versus 41.7%) can be achieved
by embolization using gelfoam preinjection [31]. Although this is an easy and well-known method for interventional radiologists, it is unfamiliar to orthopedicians who perform most of the cases of PVP in China. Three major factors may influence the cement flow into and out of the vertebral body: bone- and fracture-related parameters, injection methods, and properties of cement. Although fracture morphology is impossible to control and the method of injection has been standardized, the properties of cement may be manipulated to ultimately decrease the rate of leakage of cement. In terms of properties of cement, an increased viscosity leads to a uniformly expanding cloud and a decreased spreading distance ideally, ignoring preformed paths by vessels or structural irregularities, thus reducing the risk of leakage [23–25]. A reduction in extravasation with the high viscosity cement is hypothesized to be achieved by reaching maximum viscosity at a quicker rate and remaining at this higher viscosity for a longer duration compared with lower viscosity cement [23]. The link between the viscosity of PMMA bone cement and leakage was recently demonstrated by Baroud et al. Although the
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Fig. 2. Postoperative images of a 68-year-old woman with severe OVCFs in group H treated with PVP using high viscosity bone cement. (A) Anteroposterior and (B) lateral radiograph obtained postoperatively showing satisfactory reduction of vertebral height and bone cement filling, with only a small bone cement leakage. (C) Coronal and (D) sagittal 2D CT reconstruction postoperatively show satisfactory reduction of vertebral height and bone cement filling.
working time of the cement is approximately 17 min, they concluded that delivery of high viscosity cement may approach or exceed the human physical limit of injection forces and it may not be manually injectable with a standard syringe [23]. Anselmetti et al. analyzed the effect of high viscosity bone cement on the rate
of extravasation observed during PVP in 60 patients, compared to the use of low viscosity cement [32]. Their results showed that high viscosity bone cement system is safe and effective for clinical use, allowing a significant reduction in the rate of extravasation and, thus, leakage-related complications. In a recent study by Georgy,
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the safety of PVP techniques was possibly increased in patients who underwent PVP using high viscosity cement as compared with low viscosity cements. The high viscosity Confidence cement resulted in a rate of leakage which was comparable to that of percutaneous kyphoplasty [24]. In the present study, when low viscosity cement was used, asymptomatic cement leakage (as confirmed by the CT scan) was observed in 15 (68.2%) of 22 vertebrae treated. However, cement leakage was observed only in 5 (29.4%) vertebrae when high viscosity cement was used, which was significantly lower than Young’s finding (72.0%)(17) and Nieuwenhuijse’s finding (91.9%) [12]. CT scan is regarded as the gold standard to detect cement leakage, at least for scientific purposes, because the rates of detection using X-rays are low and complicated by only fair interobserver agreement [33,34]. Thus, although the two groups of patients in the present study were not equal in size and all detected leakages were asymptomatic, in our opinion, group H treated with high viscosity cement had reduced rate of asymptomatic cement leakages, which consequently makes PVP a safer procedure in severe OVCFs. Although use of higher viscosity cement leads to a lower risk of cement leakages as compared with low viscosity cement, intravertebral pressure during application might increase disproportionately, and may result in an increased rate of fat embolisms [35]. However in the present study, such embolisms did not occur, which may be due to the partial reduction of the fractured vertebra before injection of the cement, thus reducing the internal pressure of vertebral body when the cement is injected. Although there is lack of clinical evidence to determine the optimal volume of cement to be injected, 2–6 mL cement per vertebral body represents the current standard when fractures are located at the lumbar and lower thoracic spine [17,22,30,36]. However, to achieve full kyphosis correction and restore segmental stiffness in the thoracolumbar region, up to 8 mL may be needed [37]. A trade-off may be that a larger volume of injected cement is also more likely to result in extravasations. In a prospective clinical trial with 159 patients receiving PVP, Ryu found epidural cement leakage after PVP was dose dependent and noted a positive correlation with additional volume of cement [38]. According to our experience, for severe OVCFs, appropriate restoration of vertebral height and correction of kyphosis can reduce the difficulty in puncture, but injecting more cement blindly to pursue restoration of the vertebral height and kyphosis angle is not recommended as it is accompanied by increasing risk of leakage. Thus the injected cement volume was 3.6 mL and 3.5 mL in group H and group L, respectively, which was less than that reported by others [16,17,22,38]. Relatively shorter time of surgery in group H using high viscosity cement in the present study can be attributed to earlier beginning of application of the cement delivered by the hydraulic cement delivery system immediately after mixing the components of cement, while we had waited polymerization of low viscosity cement to end to prevent leakage of cement in the surrounding musculature at removal of a needle. The chief limitation of this study was the relatively small number of vertebrae and patients included. Moreover, kyphoplasty was not performed in both groups; hence, comparison with patients undergoing kyphoplasty and vertebroplasty using high viscosity bone cement could not be achieved.
5. Conclusions The results of this prospective randomized controlled study suggest that PVP using high viscosity bone cement can produce the same clinical outcome as PVP using low viscosity bone cement; however, the former reduces the rate of cement leakage and improves the safety of the PVP technique.
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Conflicts of interest and source of funding Project supported by the National Natural Science Foundation for Young Scholars of China (Grant No. 81401830), Project supported by the Medicine Technology Development Research Center, Ministry of Health of China (Grant No. W2012ZT14) and Project supported by the Natural Science Foundation for Young Scholars of Jiangsu Province, China (Grant No. BK 20140496) were received in support of this study. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. References [1] Kim KW, Cho KJ, Kim SW, et al. A nation-wide, outpatient-based survey on the pain, disability, and satisfaction of patients with osteoporotic vertebral compression fractures. Asian Spine J 2013;7:301–7. [2] Lee YK, Jang S, Lee HJ, et al. Mortality after vertebral fracture in Korea: analysis of the National Claim Registry. Osteoporos Int 2012;23:1859–65. [3] Sakuma M, Endo N, Oinuma T, et al. Incidence of osteoporotic fractures in Sado, Japan in 2010. J Bone Miner Metab 2014;32:200–5. [4] Venmans A, Klazen CA, Lohle PN, et al. Natural history of pain in patients with conservatively treated osteoporotic vertebral compression fractures: results from VERTOS II. AJNR Am J Neuroradiol 2012;33:519–21. [5] Anderson PA, Froyshteter AB, Tontz Jr WL. Meta-analysis of vertebral augmentation compared with conservative treatment for osteoporotic spinal fractures. J Bone Miner Res 2013;28:372–82. [6] Shen WJ, Liu TJ, Shen YS. Nonoperative treatment versus posterior fixation for thoracolumbar junction burst fractures without neurologic deficit. Spine (Phila Pa 1976) 2001;26:1038–45. [7] Wood K, Buttermann G, Mehbod A, et al. Operative compared with nonoperative treatment of a thoracolumbar burst fracture without neurological deficit. A prospective, randomized study. J Bone Joint Surg Am 2003;85-A:773–81. [8] Chen D, An ZQ, Song S, et al. Percutaneous vertebroplasty compared with conservative treatment in patients with chronic painful osteoporotic spinal fractures. J Clin Neurosci 2014;21:473–7. [9] Liu J, Li X, Tang D, et al. Comparing pain reduction following vertebroplasty and conservative treatment for osteoporotic vertebral compression fractures: a meta-analysis of randomized controlled trials. Pain Physician 2013;16:455–64. [10] Lange A, Kasperk C, Alvares L, et al. Survival and cost comparison of kyphoplasty and percutaneous vertebroplasty using German claims data. Spine 2014;39:318–26. [11] Peh WC, Gilula LA, Peck DD. Percutaneous vertebroplasty for severe osteoporotic vertebral body compression fractures. Radiology 2002;223:121–6. [12] Nieuwenhuijse MJ, van Erkel AR, Dijkstra P. Percutaneous vertebroplasty in very severe osteoporotic vertebral compression fractures: feasible and beneficial. J Vasc Intervent Radiol 2011;22:1017–23. [13] Cotten A, Boutry N, Cortet B, et al. Percutaneous vertebroplasty: state of the art. Radiographics 1998;18:311–20 [discussion 20-3]. [14] Manson NA, Phillips FM. Minimally invasive techniques for the treatment of osteoporotic vertebral fractures. J Bone Joint Surg Am 2006;88:1862–72. [15] O’Brien JP, Sims JT, Evans AJ. Vertebroplasty in patients with severe vertebral compression fractures: a technical report. AJNR Am J Neuroradiol 2000;21:1555–8. [16] Chen C, Bian J, Zhang W, et al. Unilateral versus bilateral vertebroplasty for severe osteoporotic vertebral compression fractures. J Spinal Disord Tech 2014, http://dx.doi.org/10.1097/BSD.0000000000000118. [17] Young C, Munk PL, Heran MK, et al. Treatment of severe vertebral body compression fractures with percutaneous vertebroplasty. Skeletal Radiol 2011;40:1531–6. [18] Lee B-J, Lee S-R, Yoo T-Y. Paraplegia as a complication of percutaneous vertebroplasty with polymethylmethacrylate: a case report. Spine 2002;27:E419-E22. [19] Baumann C, Fuchs H, Kiwit J, et al. Complications in percutaneous vertebroplasty associated with puncture or cement leakage. Cardiovasc Intervent Radiol 2007;30:161–8. [20] Wang LJ, Yang HL, Shi YX, et al. Pulmonary cement embolism associated with percutaneous vertebroplasty or kyphoplasty: a systematic review. Orthop Surg 2012;4:182–9. [21] Ha KY, Kim YH, Chang DG, et al. Causes of late revision surgery after bone cement augmentation in osteoporotic vertebral compression fractures. Asian Spine J 2013;7:294–300. [22] Zhang H, Sun Z, Zhu X, et al. Kyphoplasty for the treatment of very severe osteoporotic vertebral compression fracture. J Int Med Res 2012;40: 2394–400. [23] Baroud G, Crookshank M, Bohner M. High-viscosity cement significantly enhances uniformity of cement filling in vertebroplasty: an experimental model and study on cement leakage. Spine 2006;31:2562–8. [24] Georgy BA. Clinical experience with high-viscosity cements for percutaneous vertebral body augmentation: occurrence, degree, and location of cement leakage compared with kyphoplasty. AJNR Am J Neuroradiol 2010;31:504–8.
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delivery system for vertebral augmentation in benign and malignant compression fractures. Cardiovasc Int Radiol 2008;31:937–47. Tie B, He SC, Teng GJ, et al. Cement leakages in percutaneous vertebroplasty:analysis of postoperative computed tomography. Zhonghua Yi Xue Za Zhi 2012;92:299–302. Gstottner M, Angerer A, Rosiek R, et al. Quantitative volumetry of cement leakage in viscosity-controlled vertebroplasty. J Spinal Disord Tech 2012;25:E150–4. Breusch S, Heisel C, Muller J, et al. Influence of cement viscosity on cement interdigitation and venous fat content under in vivo conditions: a bilateral study of 13 sheep. Acta Orthop Scand 2002;73:409–15. Ruger M, Schmoelz W. Vertebroplasty with high-viscosity polymethylmethacrylate cement facilitates vertebral body restoration in vitro. Spine (Phila Pa 1976) 2009;34:2619–25. Belkoff SM, Mathis JM, Jasper LE, et al. The biomechanics of vertebroplasty. The effect of cement volume on mechanical behavior. Spine (Phila Pa 1976) 2001;26:1537–41. Ryu KS, Park CK, Kim MC, et al. Dose-dependent epidural leakage of polymethylmethacrylate after percutaneous vertebroplasty in patients with osteoporotic vertebral compression fractures. J Neurosurg 2002;96: 56–61.
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Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
A comparison of high viscosity bone cement and low viscosity bone cement vertebroplasty for severe osteoporotic vertebral compression fractures Liang Zhang, Jingcheng Wang, Xinmin Feng ∗ , Yuping Tao, Jiandong Yang, Yongxiang Wang, Shengfei Zhang, Jun Cai, Jijun Huang Department of Orthopedics, Clinical Medical College of Yangzhou University, Subei People’s Hospital of Jiangsu Province, No.98 Nantong West Road, Yangzhou, Jiangsu 225001, China
a r t i c l e
i n f o
Article history: Received 19 October 2014 Received in revised form 15 November 2014 Accepted 27 November 2014 Available online 4 December 2014 Keywords: Severe osteoporotic vertebral compression fractures Vertebroplasty Bone cement Viscosity Leakage
a b s t r a c t Objective: To compare the clinical outcome and complications of high viscosity and low viscosity polymethyl methacrylate bone cement PVP for severe OVCFs. Methods: From December 2010 to December 2012, 32 patients with severe OVCFs were randomly assigned to either group H using high viscosity cement (n = 14) or group L using low viscosity cement (n = 18). The clinical outcomes were assessed by the Visual Analog Scale (VAS), Oswestry Disability Index (ODI), Short Form-36 General Health Survey (SF-36), kyphosis Cobb’s angle, vertebral height, and complications. Results: Significant improvement in the VAS, ODI, SF-36 scores, kyphosis Cobb’s angle, and vertebral height were noted in both the groups, and there were no significant differences between the two groups. Cement leakage was seen less in group H. Postoperative assessment using computed tomography identified cement leakage in 5 of 17 (29.4%) vertebrae in group H and in 15 of 22 (68.2%) vertebrae in group L (P = 0.025). Conclusions: The PVP using high viscosity bone cement can provide the same clinical outcome and fewer complications compared with PVP using low viscosity bone cement. © 2014 Published by Elsevier B.V.
1. Introduction Osteoporotic vertebral compression fractures (OVCFs) are the most common types of osteoporotic fracture in the elderly population, causing back pain and loss of mobility due to the resulting spinal deformities [1–4]. Traditional conservative therapy includes bed rest, use of analgesics, physiotherapy, and external bracing. However, many patients may still complain of severe pain not responding to these therapies and even exhibiting progressive kyphosis and collapse of the vertebral body [5–7]. The classical open surgery with different types of metal implants is not an optimal treatment for a majority of patients due to the poor quality of osteoporotic bone and associated comorbidities. Percutaneous vertebroplasty (PVP) has gained popularity as a treatment modality for OVCFs, providing nearly immediate pain relief and mechanical strengthening of the vertebral body with low incidence of adverse events and morbidity [8–10].
∗ Corresponding author. Tel.: +86 18952578137; fax: +86 514 87373315. E-mail address: [email protected] (X. Feng). http://dx.doi.org/10.1016/j.clineuro.2014.11.018 0303-8467/© 2014 Published by Elsevier B.V.
The severe OVCF, refers to part of the vertebral body collapsed to less than one-third of its original height, has been cited as relative or even absolute contraindication by many authors for technical difficulties to perform and resultant high risk of cement leakage [11–14]. Some studies have reported the sustained efficacy of PVP treating severe OVCFs with advances in medical devices and imaging [11,12,15,16]. However, cement leakage, ranging from 43% to 45% detected by an X-ray to 78% to 91.9% detected by computed tomography (CT) scan, is still the main risk of complication for PVP with conventional low viscosity cement [11,16,17]. While most leakages are clinically asymptomatic, serious complications occurred in 3.9–7.5% of the patients who underwent PVP. If the cement leakages cause neurologic deficits, abdominal thromboembolisms, and pulmonary embolism, induction of new adjacent vertebral fractures by intradiscal cement leakage is suggested [18–21]. To reduce cement leakages, adequate patient selection, technical improvement, and its implementation such as accurate imaging in the hands of skilled operators were recommended, but the results were not conclusive [11,12,22]. Viscosity, the main characteristic parameter of the polymethyl methacrylate (PMMA) bone
L. Zhang et al. / Clinical Neurology and Neurosurgery 129 (2015) 10–16
cement, has been demonstrated to be the key influencing factor for leakage when PVP technique and radiological equipment are optimal. High viscosity cements have been demonstrated to effectively reduce the risk for extravasation, thereby improving overall clinical safety, and improve infiltration and restore height. Baroud et al. demonstrated that cement leakage ceased completely when its viscosity was very high in their experimental model [23]. Georgy and Anselmetti further confirmed that high viscosity cement is safe in application and may increase the safety of vertebral augmentation techniques compared with less viscous cements, in a prospective clinical study [24,25]. These cements reach a constant putty-like viscosity immediately after mixing, without a waiting period of few minutes as in other cements, and remain consistently injectable for 8–10 min before these cements solidify. The objective of this prospective randomized controlled study was to evaluate and compare the clinical outcomes and cement leakage of high viscosity PMMA bone cement versus low viscosity cement PVP in treating severe OVCFs. To our knowledge, no other report has been published on this comparison. 2. Materials and methods This was a prospective randomized controlled study, approved by the Institutional Review Board. From December 2010 to December 2012, a total of 32 patients with severe OVCFs adopting PVP were included in the present study. Written consent to participate in the study was obtained from each patient. Patients were included in the study if they (1) were aged above 50 years, (2) had severe OVCFs (part of the vertebral body collapsed to less than one-third of their original height), (3) had focal back pain without definite radicular signs and symptoms unresponsive to at least 8 weeks of appropriate conservative treatment, (4) had back pain related to the location of the OVCF on spinal radiographs, (5) were diagnosed to have an apparent bone edema in the fractured vertebra on magnetic resonance imaging (MRI) T2-weighted short tau inversion recovery sequences, and (6) had decreased bone mineral density (T scores < −1). Patients were excluded if they (1) had ordinary OVCFs (vertebral body collapsed to more than onethird of their original height), (2) had spinal cord compression or stenosis of the vertebral canal >30% of the local canal diameter, (3) had neurologic deficits, (4) had uncorrectable bleeding disorders, (5) had systemic or local spine infections, and (6) had severe comorbidity in the heart, liver, kidney, and lung intolerance to surgery. After enrollment, the patients were given a serial number according to the consecutive sequence of hospitalization and were assigned to either group H (used high viscosity cement) or group L (used low viscosity cement) randomly by computer according to the serial number. The study population consisted of 14 patients in the group H (mean age, 75.5 ± 9.3 years) and 18 patients in the group L (mean age, 75.8 ± 9.3 years). All procedures were performed by the same surgeon. 2.1. Radiological evaluation All patients underwent preoperative plain radiography, CT construction, MRI, and dual-energy X-ray absorptiometry for testing bone mineral density. Changes in marrow signal were assessed using MRI to determine the symptomatic levels of the fracture. Bone scans were used in cases where MRI was contraindicated (e.g. presence of a pacemaker). All radiological assessments were evaluated by two radiologists who were unaware of the clinical presentation and its outcome in the patients. The extent of vertebral body collapse was measured from the height of the maximum collapse on lateral radiographs. The percentage of collapse, compared with the normal vertebral body
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height, was then calculated. Anterior and middle vertebral heights were defined as the distance between the upper and lower endplates at the anterior vertebral body wall and in the centre of the vertebral body, respectively. Normal heights of the anterior and midvertebra were defined as the mean of the equivalent values for the adjacent superior and inferior nonfractured vertebrae. Variation in vertebral body height was then calculated by fractured vertebral body height/normal vertebral body height × 100%. The kyphosis Cobb’s angle was assessed by measuring the kyphotic angle from the superior endplate of the vertebral body one level above the injury to the inferior endplate of the vertebral body one level below. 2.2. Procedural technique The procedure was performed under general anesthesia to provide a certain comfort, especially during the progression of the trocar, which can be painful. Patients were placed in a prone position and monitored by electrocardiograph and oxygen saturation during the procedures. After localizing the fractured vertebra using fluoroscopy, the surgeon placed overlapping palm on the vertebral spinous process to push toward ventral slowly for partial reduction of the fractured vertebra. Through a 0.5-cm-sized skin incision, the vertebroplasty needles were advanced to obtain bilateral transpedicular access until its tip reached the junction of the anterior and middle one-third of the vertebral body under C-arm fluoroscopic guidance. In cases where pedicles were not visualized on fluoroscopy, the parapedicular or unipedicular approach was used. Once the needle position was satisfactory, high viscosity cement (Confidence; DePuy Spine, Raynham, MA) or low viscosity cement (Vertebroplastic; DePuy Acromed, Raynham, MA) was injected into the vertebral body using continuous fluoroscopic guidance. Depending on the ambient temperature of the operation room, the time from the beginning of mixing to the beginning of application of low viscosity cement was 4–8 min, while high viscosity cement could be applied immediately after mixing for 30 s. The injection of cement was stopped whenever epidural or paravertebral opacification was observed or the cement reached the dorsal quarter of the vertebral body. The needles were not removed before the end of polymerization to prevent spreading of low viscosity cement, while the needles were removed immediately after the application of high viscosity cement (due to its high viscosity there was no possibility of cement leakage from the needles into the surrounding area). 2.3. Assessment of outcomes Patients were followed up postoperatively, and at 3 days, 3, 12, and 18 months after surgery. The Visual Analog Scale (VAS) score was used to evaluate back pain, Oswestry Disability Index (ODI) was used as a functional assessment, and Short Form-36 General Health Survey (SF-36) was used to evaluate the quality of life. Any clinical complications were recorded immediately after the procedure. Cement leakage, defined as the presence of any extravertebral cement, was assessed independent of the treating physician by two investigators using the CT scan. The position of any cement leakage was noted and was correlated with any symptoms reported during the follow-up period. 2.4. Statistical analysis Data were presented as the mean ± standard deviation. The SPSS for Windows Version 13.0 (SPSS, Chicago, IL) was used for the analysis. Intergroup comparisons were made using the Student’s paired t-test or Chi-square test. Comparisons between before and after operation were made using the Student’s paired t-test. The
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Table 1 Surgical parameters of the studied population.
Patients Male/female Age(years) Vertebral bodies(n) Operative time Injected cement volume Unipedicular/bipedicular approach
Group H
Group L
14 2:12 75.5 ± 9.3 17 41.8 ± 9.0 3.4 ± 1.0 4:13
18 3:15 75.8 ± 9.3 22 44.8 ± 12.5 3.5 ± 0.8 6:16
P-value 1.00 0.93 0.46 0.67 1.00
difference in proportions of cement leakage between the two groups was assessed using the Fisher’s exact test. P-values < 0.05 were considered statistically significant. 3. Results There were no significant differences between group H and group L in the gender ratios, age, and vertebral bodies involved according to the statistical results (Table 1). The mean follow-up duration was 24.5 months (range, 18–42 months). There was no statistical difference between the two groups according to the mean surgery time/vertebrae (P = 0.46) and mean injected cement volume/vertebrae (P = 0.67). Of 17 vertebrae in group H, PVP was unipedicular in 4 (23.5%) cases and bipedicular in 13 (76.5%), whereas the procedure was unipedicular in 6 (27.3%) cases and bipedicular in 16 (72.7%) of 22 vertebrae in group H, with no statistical difference (P = 1.00). These results are presented in Table 1. The two groups reported immediate postoperative pain relief, and none had subjective complaints of worsening pain at any time point of follow-up. The mean preoperative VAS score was 8.4 and 8.6, which significantly decreased to 2.2 and 1.9 at 18 months follow-up in group H and group L, respectively (P < 0.01) (Table 2). The mean preoperative ODI score was 73.9% and 75.5%, which significantly improved to 29.8% and 32.8% at 18 months follow-up in group H and group L, respectively (P < 0.01) (Table 2). The mean preoperative physical component score (PCS) of the SF-36 score was 32.1 and 31.6, which significantly improved to 50.5 and 48.8 at 18 months follow-up in group H and group L, respectively (P < 0.01). The mean preoperative mental component score (MCS) of the SF-36 score was 31.9 and 31.3, which significantly improved to 46.7 and 45.2 at 18 months follow-up in group H and group L, respectively (P < 0.01) (Table 2). However, there were no significant differences between group H and group L in VAS score, ODI score, and SF-36 score preoperatively and at 18 months follow-up (Table 2). The variation in the anterior vertebral height significantly increased from preoperative (30.8%) to postoperative (51.9%) period in group H (P < 0.01) and from preoperative (30.3%) to postoperative (47.3%) period in group L (P < 0.01), without any statistical difference between the two groups irrespective of preoperative (P = 0.82) or postoperative (P = 0.36) period. The variation in the middle vertebral height significantly increased Table 2 Mean VAS, ODI, PCS and MCS before and after vertebroplasty comparing between the two groups. Parameter
Group H (14 pt)
Group L (18 pt)
P-value
VAS pre-OP (0–10) VAS post-OP (0–10) ODI pre-OP (0–100%) ODI post-OP (0–100%) PCS pre-OP PCS post-OP MCS pre-OP MCS post-OP
8.4 2.2 73.9 29.8 32.1 50.5 31.9 46.7
8.6 1.9 75.5 32.8 31.6 48.8 31.3 45.2
0.66 0.46 0.65 0.14 0.71 0.45 0.65 0.40
Table 3 Mean anterior vertebral body height variation, middle vertebral body height variation, Kyphosis angle before and after vertebroplasty and cement leakage comparing between the two groups. Parameter
Group H (14 pt)
Group L (18 pt)
P-value
Anterior vertebral body height variation pre-OP (%) Anterior vertebral body height variation post-OP (%) Middle vertebral body height variation pre-OP (%) Middle vertebral body height variation post-OP (%) Kyphosis angle pre-OP (◦ ) Kyphosis angle post-OP (◦ ) Cement leakage
30.8%
30.3%
0.82
51.9%
47.3%
0.36
29.7%
32.8%
0.22
45.6%
50.7%
0.24
20.8 14.8 5
19.3 14.9 15
0.40 0.94 0.025
from preoperative (29.7%) to postoperative (45.6%) period in group H (P < 0.01) and from preoperative (32.8%) to postoperative (50.7%) in group L (P < 0.01), without any statistical difference between the two groups irrespective of preoperative (P = 0.22) or postoperative (P = 0.24) period. The mean kyphosis Cobb’s angle significantly increased from preoperative (20.9◦ ) to postoperative (14.8◦ ) period in group H (P < 0.01), and from preoperative (19.3◦ ) to postoperative (14.9◦ ) period in group L (P < 0.01), without any statistical difference between the two groups irrespective of preoperative (P = 0.40) or postoperative (P = 0.94) period (Table 3). No significant clinical complications or postprocedural clinical sequelae were encountered. Postoperative assessment using CT identified cement leakage in 5 of 17 (29.4%) vertebrae in group H and in 15 of 22 (68.2%) vertebrae in group L (P = 0.025). All leakages were clinically silent and no neural compromise or pulmonary embolism was found. The adjacent vertebral fractures did not occur in either group. Pre- and postoperative images of a typical patient in group H treated with PVP using high viscosity bone cement are shown in Figs. 1 and 2. 4. Discussion OVCFs are linked with older age and are metastatic with poor general condition, leading to significant rate of morbidity and mortality, problems in lung function, nourishment disorders, reduced mobility, and psychic disorder caused by pains and drugs [1–3]. The conventional surgeries of stabilization, ostrosynthesis and lumbar fusion, had no success because of bad quality of bones [6,26]. Despite marginal understanding of the mechanism, PVP is generally considered to be a safe and effective treatment option for OVCFs [8–10]. However, severe OVCFs have always been considered as a relative or even absolute contraindication due to the technical difficulty because of the extreme kyphotic angle and the severe loss of vertebral height [27–29]. In severe OVCFs, placement of needle is more challenging, and a second needle is more frequently necessary to obtain an adequate distribution of cement as compared to the treatment of nonsevere OVCFs [12,15,30]. O’Brien et al. were able to successfully advance the needle tip to the anterior one-third of all vertebral bodies with subsequent filling of the entire vertebral body in severe OVCFs using a bipedicular, far lateral approach [15]. The present study adopted a modified technique for treating severe OVCFs with emphasis on partial reduction of the fractured vertebra before puncture to increase the operating space of the needle. In combination with a smaller gauge trocar, the needle (unipedicular/bipedicular approach) could be advanced into the fractured vertebral body while remaining lateral to the dominant portion of the vertebral body, as most patterns of fracture result in maximal central collapse, making it impossible to position the needle tip at midline.
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Fig. 1. Preoperative images of a 68-year-old woman with severe OVCFs in group H treated with PVP using high viscosity bone cement. (A) Anteroposterior and (B) lateral radiograph showing a severe compression fracture of the T12 vertebral body. (C) Coronal and (D) sagittal 2D CT reconstruction image of the T12 vertebral body showing a severe compression fracture and the most severe portion of the compression fracture located in the center of the vertebral body. (E) Sagittal MR image of the T12 vertebral body confirming the severe compression fracture. 2D, two-dimensional; CT, computed tomography; MR, magnetic resonance; OVCF, osteoporotic vertebral compression fracture; PVP, percutaneous vertebroplasty
It is unclear whether spatial distribution of the cement influenced by its viscosity affects the outcome of PVP. The results of the present study showed a clinically relevant, significant, immediate, and durable reduction in mean back pain and function, which was comparable between both the groups. Increase in quality of life, measured using the SF-36, was similar in both the groups. Thus there is no direct dependence between the quantity of cement applied and clinical outcome. Severe OVCFs often have some cleft in the vertebral wall, which increases the risk of cement leakage. Although most leakages remain clinically asymptomatic, the cement leakage is reported up to 91.9% in severe OVCFs receiving PVP [12]. A majority of leakages are cortical, with venous leakages occurring infrequently. Other cement-related severe complications include paraplegia, spinal cord and nerve root compression, cement pulmonary embolisms, and possible death [18–21]. Hence, severe OVCFs represent a unique subgroup, and additional care should be exercised with PVP in severe OVCFs. Bhatia et al. recently demonstrated that significant reduction in leakage (22.5% versus 41.7%) can be achieved
by embolization using gelfoam preinjection [31]. Although this is an easy and well-known method for interventional radiologists, it is unfamiliar to orthopedicians who perform most of the cases of PVP in China. Three major factors may influence the cement flow into and out of the vertebral body: bone- and fracture-related parameters, injection methods, and properties of cement. Although fracture morphology is impossible to control and the method of injection has been standardized, the properties of cement may be manipulated to ultimately decrease the rate of leakage of cement. In terms of properties of cement, an increased viscosity leads to a uniformly expanding cloud and a decreased spreading distance ideally, ignoring preformed paths by vessels or structural irregularities, thus reducing the risk of leakage [23–25]. A reduction in extravasation with the high viscosity cement is hypothesized to be achieved by reaching maximum viscosity at a quicker rate and remaining at this higher viscosity for a longer duration compared with lower viscosity cement [23]. The link between the viscosity of PMMA bone cement and leakage was recently demonstrated by Baroud et al. Although the
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Fig. 2. Postoperative images of a 68-year-old woman with severe OVCFs in group H treated with PVP using high viscosity bone cement. (A) Anteroposterior and (B) lateral radiograph obtained postoperatively showing satisfactory reduction of vertebral height and bone cement filling, with only a small bone cement leakage. (C) Coronal and (D) sagittal 2D CT reconstruction postoperatively show satisfactory reduction of vertebral height and bone cement filling.
working time of the cement is approximately 17 min, they concluded that delivery of high viscosity cement may approach or exceed the human physical limit of injection forces and it may not be manually injectable with a standard syringe [23]. Anselmetti et al. analyzed the effect of high viscosity bone cement on the rate
of extravasation observed during PVP in 60 patients, compared to the use of low viscosity cement [32]. Their results showed that high viscosity bone cement system is safe and effective for clinical use, allowing a significant reduction in the rate of extravasation and, thus, leakage-related complications. In a recent study by Georgy,
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the safety of PVP techniques was possibly increased in patients who underwent PVP using high viscosity cement as compared with low viscosity cements. The high viscosity Confidence cement resulted in a rate of leakage which was comparable to that of percutaneous kyphoplasty [24]. In the present study, when low viscosity cement was used, asymptomatic cement leakage (as confirmed by the CT scan) was observed in 15 (68.2%) of 22 vertebrae treated. However, cement leakage was observed only in 5 (29.4%) vertebrae when high viscosity cement was used, which was significantly lower than Young’s finding (72.0%)(17) and Nieuwenhuijse’s finding (91.9%) [12]. CT scan is regarded as the gold standard to detect cement leakage, at least for scientific purposes, because the rates of detection using X-rays are low and complicated by only fair interobserver agreement [33,34]. Thus, although the two groups of patients in the present study were not equal in size and all detected leakages were asymptomatic, in our opinion, group H treated with high viscosity cement had reduced rate of asymptomatic cement leakages, which consequently makes PVP a safer procedure in severe OVCFs. Although use of higher viscosity cement leads to a lower risk of cement leakages as compared with low viscosity cement, intravertebral pressure during application might increase disproportionately, and may result in an increased rate of fat embolisms [35]. However in the present study, such embolisms did not occur, which may be due to the partial reduction of the fractured vertebra before injection of the cement, thus reducing the internal pressure of vertebral body when the cement is injected. Although there is lack of clinical evidence to determine the optimal volume of cement to be injected, 2–6 mL cement per vertebral body represents the current standard when fractures are located at the lumbar and lower thoracic spine [17,22,30,36]. However, to achieve full kyphosis correction and restore segmental stiffness in the thoracolumbar region, up to 8 mL may be needed [37]. A trade-off may be that a larger volume of injected cement is also more likely to result in extravasations. In a prospective clinical trial with 159 patients receiving PVP, Ryu found epidural cement leakage after PVP was dose dependent and noted a positive correlation with additional volume of cement [38]. According to our experience, for severe OVCFs, appropriate restoration of vertebral height and correction of kyphosis can reduce the difficulty in puncture, but injecting more cement blindly to pursue restoration of the vertebral height and kyphosis angle is not recommended as it is accompanied by increasing risk of leakage. Thus the injected cement volume was 3.6 mL and 3.5 mL in group H and group L, respectively, which was less than that reported by others [16,17,22,38]. Relatively shorter time of surgery in group H using high viscosity cement in the present study can be attributed to earlier beginning of application of the cement delivered by the hydraulic cement delivery system immediately after mixing the components of cement, while we had waited polymerization of low viscosity cement to end to prevent leakage of cement in the surrounding musculature at removal of a needle. The chief limitation of this study was the relatively small number of vertebrae and patients included. Moreover, kyphoplasty was not performed in both groups; hence, comparison with patients undergoing kyphoplasty and vertebroplasty using high viscosity bone cement could not be achieved.
5. Conclusions The results of this prospective randomized controlled study suggest that PVP using high viscosity bone cement can produce the same clinical outcome as PVP using low viscosity bone cement; however, the former reduces the rate of cement leakage and improves the safety of the PVP technique.
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Conflicts of interest and source of funding Project supported by the National Natural Science Foundation for Young Scholars of China (Grant No. 81401830), Project supported by the Medicine Technology Development Research Center, Ministry of Health of China (Grant No. W2012ZT14) and Project supported by the Natural Science Foundation for Young Scholars of Jiangsu Province, China (Grant No. BK 20140496) were received in support of this study. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. References [1] Kim KW, Cho KJ, Kim SW, et al. A nation-wide, outpatient-based survey on the pain, disability, and satisfaction of patients with osteoporotic vertebral compression fractures. Asian Spine J 2013;7:301–7. [2] Lee YK, Jang S, Lee HJ, et al. Mortality after vertebral fracture in Korea: analysis of the National Claim Registry. Osteoporos Int 2012;23:1859–65. [3] Sakuma M, Endo N, Oinuma T, et al. Incidence of osteoporotic fractures in Sado, Japan in 2010. J Bone Miner Metab 2014;32:200–5. [4] Venmans A, Klazen CA, Lohle PN, et al. Natural history of pain in patients with conservatively treated osteoporotic vertebral compression fractures: results from VERTOS II. AJNR Am J Neuroradiol 2012;33:519–21. [5] Anderson PA, Froyshteter AB, Tontz Jr WL. Meta-analysis of vertebral augmentation compared with conservative treatment for osteoporotic spinal fractures. J Bone Miner Res 2013;28:372–82. [6] Shen WJ, Liu TJ, Shen YS. Nonoperative treatment versus posterior fixation for thoracolumbar junction burst fractures without neurologic deficit. Spine (Phila Pa 1976) 2001;26:1038–45. [7] Wood K, Buttermann G, Mehbod A, et al. Operative compared with nonoperative treatment of a thoracolumbar burst fracture without neurological deficit. A prospective, randomized study. J Bone Joint Surg Am 2003;85-A:773–81. [8] Chen D, An ZQ, Song S, et al. Percutaneous vertebroplasty compared with conservative treatment in patients with chronic painful osteoporotic spinal fractures. J Clin Neurosci 2014;21:473–7. [9] Liu J, Li X, Tang D, et al. Comparing pain reduction following vertebroplasty and conservative treatment for osteoporotic vertebral compression fractures: a meta-analysis of randomized controlled trials. Pain Physician 2013;16:455–64. [10] Lange A, Kasperk C, Alvares L, et al. Survival and cost comparison of kyphoplasty and percutaneous vertebroplasty using German claims data. Spine 2014;39:318–26. [11] Peh WC, Gilula LA, Peck DD. Percutaneous vertebroplasty for severe osteoporotic vertebral body compression fractures. Radiology 2002;223:121–6. [12] Nieuwenhuijse MJ, van Erkel AR, Dijkstra P. Percutaneous vertebroplasty in very severe osteoporotic vertebral compression fractures: feasible and beneficial. J Vasc Intervent Radiol 2011;22:1017–23. [13] Cotten A, Boutry N, Cortet B, et al. Percutaneous vertebroplasty: state of the art. Radiographics 1998;18:311–20 [discussion 20-3]. [14] Manson NA, Phillips FM. Minimally invasive techniques for the treatment of osteoporotic vertebral fractures. J Bone Joint Surg Am 2006;88:1862–72. [15] O’Brien JP, Sims JT, Evans AJ. Vertebroplasty in patients with severe vertebral compression fractures: a technical report. AJNR Am J Neuroradiol 2000;21:1555–8. [16] Chen C, Bian J, Zhang W, et al. Unilateral versus bilateral vertebroplasty for severe osteoporotic vertebral compression fractures. J Spinal Disord Tech 2014, http://dx.doi.org/10.1097/BSD.0000000000000118. [17] Young C, Munk PL, Heran MK, et al. Treatment of severe vertebral body compression fractures with percutaneous vertebroplasty. Skeletal Radiol 2011;40:1531–6. [18] Lee B-J, Lee S-R, Yoo T-Y. Paraplegia as a complication of percutaneous vertebroplasty with polymethylmethacrylate: a case report. Spine 2002;27:E419-E22. [19] Baumann C, Fuchs H, Kiwit J, et al. Complications in percutaneous vertebroplasty associated with puncture or cement leakage. Cardiovasc Intervent Radiol 2007;30:161–8. [20] Wang LJ, Yang HL, Shi YX, et al. Pulmonary cement embolism associated with percutaneous vertebroplasty or kyphoplasty: a systematic review. Orthop Surg 2012;4:182–9. [21] Ha KY, Kim YH, Chang DG, et al. Causes of late revision surgery after bone cement augmentation in osteoporotic vertebral compression fractures. Asian Spine J 2013;7:294–300. [22] Zhang H, Sun Z, Zhu X, et al. Kyphoplasty for the treatment of very severe osteoporotic vertebral compression fracture. J Int Med Res 2012;40: 2394–400. [23] Baroud G, Crookshank M, Bohner M. High-viscosity cement significantly enhances uniformity of cement filling in vertebroplasty: an experimental model and study on cement leakage. Spine 2006;31:2562–8. [24] Georgy BA. Clinical experience with high-viscosity cements for percutaneous vertebral body augmentation: occurrence, degree, and location of cement leakage compared with kyphoplasty. AJNR Am J Neuroradiol 2010;31:504–8.
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