|Year : 2018 | Volume
| Issue : 1 | Page : 1-7
Poly(methyl methacrylate) bone cement and injectable artificial bone implantation in the treatment of senile degenerative thoracic osteoporotic vertebral compression fractures: study protocol for a randomized controlled trial
Yuan Zhang, Rong Ren, Ze-Qing Li, Yi-Bo Hu, Ming Li
Department of Orthopedics, Affiliated Hospital of Qinghai University, Xining, Qinghai Province, China
|Date of Web Publication||9-Apr-2018|
Department of Orthopedics, Affiliated Hospital of Qinghai University, Xining, Qinghai Province
Source of Support: None, Conflict of Interest: None
Background and objectives: Percutaneous kyphoplasty is an effective treatment method for senile degenerative thoracic osteoporotic vertebral compression fractures. However, its clinical long-term effect is controversial among scholars both inside and outside China. The poly(methyl methacrylate) (PMMA) bone cement commonly used in percutaneous kyphoplasty has good plasticity and formability, but its biocompatibility is not yet clear. Injectable artificial bone is a novel filling material that can induce bone formation, but its long-term efficacy remains to be verified. Therefore, we will compare the efficacy of OSTEOPAL® plus PMMA bone cement and geneX® injectable artificial bone graft in the treatment of senile degenerative thoracic osteoporotic vertebral compression fractures at 24 months postoperatively.
Design: This is a prospective, single-center, open-label, randomized controlled trial.
Methods: A total of 378 patients with senile degenerative thoracic osteoporotic vertebral compression fractures will be recruited from the Department of Orthopedics, Affiliated Hospital of Qinghai University, China. The patients will be randomized into two groups and undergo percutaneous kyphoplasty. The PMMA group (n = 189) will be treated with OSTEOPAL® plus PMMA bone cement. The artificial bone group (n = 189) will be treated with geneX® injectable artificial bone. Follow-ups will be conducted at 1 week and at 3, 6, 12, and 24 months.
Outcome measures: The primary outcome measure will be the vertebral body height restoration rate at 24 months postoperatively to evaluate the repair effect of the damaged thoracic vertebra. The secondary outcome measures will be the vertebral body height restoration rate at 1 week and 3, 6, and 12 months postoperatively; the incidence of bone cement leakage at 1 week and 3, 6, 12, and 24 months postoperatively; the Visual Analog Scale score, Oswestry Disability Index, compression rate of the anterior vertebral height, and thoracic morphology revealed by computed tomography preoperatively and at 1 week and 3, 6, 12, and 24 months postoperatively; and the incidence of adverse reactions at 1 week and 3, 6, 12, and 24 months postoperatively.
Discussion: Our results will verify whether OSTEOPAL® plus PMMA bone cement and geneX® injectable artificial bone graft are effective and safe for treating senile degenerative thoracic osteoporotic vertebral compression fractures in the short term and at the 2-year follow-up.
Ethics and dissemination: This trial has been approved by the Medical Ethics Committee of Affiliated Hospital of Qinghai University of China in November 2017. The study protocol will be conducted in accordance with the Declaration of Helsinki, formulated by the World Medical Association. Written informed consent will be obtained from all participants. This trial was designed in December 2017. The recruitment of subjects and data collection will begin in July 2018. Outcome measures will be analyzed in September 2020. This trial will be completed in October 2020. The results of the trial will be reported in a scientific conference or disseminated in a peer-reviewed journal.
Trial registration: This trial had been registered in the Chinese Clinical Trial Registry (registration number: ChiCTR1800015411). Protocol version (1.0).
Keywords: poly(methyl methacrylate); osteoporotic; compression fractures; senile; bone cement leakage; compression rate of anterior vertebral height; vertebral body height restoration rate; biocompatible materials; clinical trial
|How to cite this article:|
Zhang Y, Ren R, Li ZQ, Hu YB, Li M. Poly(methyl methacrylate) bone cement and injectable artificial bone implantation in the treatment of senile degenerative thoracic osteoporotic vertebral compression fractures: study protocol for a randomized controlled trial. Clin Trials Degener Dis 2018;3:1-7
|How to cite this URL:|
Zhang Y, Ren R, Li ZQ, Hu YB, Li M. Poly(methyl methacrylate) bone cement and injectable artificial bone implantation in the treatment of senile degenerative thoracic osteoporotic vertebral compression fractures: study protocol for a randomized controlled trial. Clin Trials Degener Dis [serial online] 2018 [cited 2019 Aug 21];3:1-7. Available from: http://www.clinicaltdd.com/text.asp?2018/3/1/1/228985
| Introduction|| |
According to epidemiological surveys, the distal humerus, hip, and thoracolumbar vertebrae are prone to fractures, especially in patients with osteoporosis.,,, Osteoporotic vertebral compression fractures (OVCFs) are very common in the clinical setting.,, The patient’s quality of life can be severely affected by obstinate low back pain after an OVCF. Without timely treatment, the patient may develop secondary progressive kyphosis or even respiratory and cardiovascular system failure, shortening the patient’s lifespan and increasing the risk of mortality.,
Scholars have reported that minimally invasive surgery, conservative treatment, and open surgery are the main treatments for OVCF. Percutaneous kyphoplasty (PKP) is one type of minimally invasive surgery. PKP is performed to restore the vertebral height by balloon dilatation, inject bone cement into the compressed vertebral body, and slowly compress the vertebral body to restore the vertebral body and correct the kyphotic deformity. PKP offers a completely new choice for the treatment of OVCF. However, scholars both inside and outside China have different views on the clinical long-term effects of this procedure, and the controversy is obvious.,,,,
The poly(methyl methacrylate) (PMMA) bone cement commonly used in PKP has good plasticity and formability, but its biocompatibility is poor.15, 16 geneX® injectable artificial bone is a new type of filling material that can induce bone formation, but its long-term efficacy remains to be verified.
Three studies that assessed the research progress in the treatment of senile degenerative thoracic OVCF published from 2010 to 2016 are listed in [Table 1].,,
|Table 1: Previous studies addressing the research progress in the treatment of senile degenerative thoracic OVCF published from 2010 to 2016|
Click here to view
Novelty of this study
This randomized controlled trial will reveal the difference in the short-term and long-term efficacy of OSTEOPAL® plus PMMA bone cement and geneX® injectable artificial bone in the treatment of senile degenerative thoracic OVCF. The objective data will show the filling effect and biocompatibility of the two materials.
The aim of this trial is to compare the efficacy of OSTEOPAL® plus PMMA bone cement and geneX® injectable artificial bone graft in the treatment of senile degenerative thoracic OVCF in the short term and at 2 years postoperatively.
| Methods/Design|| |
This is a prospective, single-center, open-label, randomized controlled clinical trial.
Department of Orthopedics, Affiliated Hospital of Qinghai University, Qinghai Province, China.
Our recruitment notice containing details of the study will be posted on a bulletin board at the Affiliated Hospital of Qinghai University of China. Patients or family members (will not participate) of patients who are interested in participating in the study can directly call the study leader. After screening, and based on the inclusion and exclusion criteria and provision of informed consent, these patients will be enrolled in our study. The research doctor will treat the patients and regularly perform follow-up according to the diagnosis and treatment plan. During the trial, the hospital will provide a certain subsidy as follow-up fare. Moreover, the registration fee and test room inspection fee will be exempted during follow-up.
In total, 378 outpatients or inpatients with senile degenerative thoracic OVCF will be recruited from the Department of Orthopedics, Affiliated Hospital of Qinghai University, China.
Patients who meet all of the following criteria will be considered for study inclusion:
- Compression of the anterior edge of a single thoracic vertebrae with a > 20% degree of compression
- T value of ≤ −2.5 for osteoporosis as confirmed by a bone densitometer
- Age of 65 to 75 years
- Preoperative imaging findings suggesting that the posterior wall of the vertebral body is complete and that no space occupation is present in the spinal canal
- No signs or symptoms of spinal cord or nerve root damage
- Provision of informed consent
Patients who meet one or more of the following conditions will be excluded from the study:
- Vertebral fracture caused by trauma or external force
- Old fractures and tumor lesion-induced fractures
- Thoracic vertebral compression greater than 3/4
- Severe bone destruction at the posterior edge of the vertebral body leading to incomplete bone in the posterior edge of the vertebral body
- Spinal cord injury or nerve injury
- Infection in the puncture area or combination with other lesions
Randomization and blinding
Random number tables will be generated using SPSS 19.0 software (IBM, Armonk, NY, USA). The patients will be randomly assigned a number (1–378) after admission. Patients with an odd number will be included in the PMMA group, and those with an even number will be included in the artificial bone group. Thus, all participants will be equally and randomly divided into two groups. No allocation concealment or blinding method will be used.
All participants will be admitted to the hospital for treatment of thoracic OVCF. All patients will be expected to report pain in the fracture area, and physical examination should show obviously limited range of motion, tenderness over the spinous process at the fracture site, and percussion pain. However, there should be no sign of nerve damage. Imaging examination will be expected to reveal discontinuity of the fracture. The main lesion will be a compression fracture at the anterior edge of the vertebral body [Figure 1].
|Figure 1: Filling repair with PMMA bone cement.|
Note: PMMA: Poly(methyl methacrylate).
Click here to view
(1) The patients will be placed in the prone position and undergo general anesthesia. (2) Using X-ray fluoroscopy, a sleeve will be implanted into the vertebral body by percutaneous puncture using a No. 11 needle. The pedicle approach will be used to implant the balloon in the anterior and middle parts. (3) The puncture needle will be placed at the junction of the pedicle and vertebral body. At this site, the working sleeve will be implanted to create a balloon implant channel. (4) After balloon implantation, a contrast agent will be injected under continuous fluoroscopy to slowly inflate and expand the balloon. (5) According to the size and intensity of the vertebral body, 1.4 to 5.5 mL of contrast agent will be injected on each side. (6) The balloon will stop expanding when it contacts the vertebral cortex or the pressure reaches 250 psi. The injectable calcium phosphate will be adjusted to a suitably dilute consistency and viscosity; it will then be pressurized and injected into the vertebral body by a syringe through the working channel. The injection will continue until the space created by the balloon is completely filled.
Artificial bone group
Induction of anesthesia and establishment of the balloon implantation pathway will be performed in a manner identical to that described above. The balloon will stop expanding when it contacts the vertebral cortex or the pressure reaches 250 psi. geneX® injectable artificial bone will be pressurized and injected into the vertebral body by a syringe through the working channel. The injection will continue until the space created by the balloon is completely filled.
Methylprednisolone 80 mg will be administered within 6 hours postoperatively to prevent nerve root edema. The skin sensation and muscle strength of both lower extremities will be regularly observed, and symptomatic measures will be adopted when necessary. At 7 days postoperatively, when the compressive strength of the calcium phosphate cement (Biopex) reaches its maximum, the patients will begin to walk.
Primary outcome measure
The primary outcome measure will be the vertebral body height restoration rate at 24 months postoperatively, which will be assessed to evaluate the repair effect of the damaged thoracic vertebra. The vertebral body height restoration rate is calculated as follows: (postoperative vertebral height -preoperative vertebral height) / (vertebral height before fracture − preoperative vertebral height) × 100%. A higher value indicates better postoperative recovery of the vertebral height in patients with senile degenerative thoracic OVCF.
Secondary outcome measures
The secondary outcome measures will be as follows:
- Vertebral body height restoration rate at 1 week and 3, 6, and 12 months postoperatively: The evaluation criteria are the same as described above.
- Incidence of bone cement leakage at 1 week and 3, 6, 12, and 24 months postoperatively: Bone cement leakage indicates poor biocompatibility of the material, which fails to fuse with the injury area; this results in infection and nerve compression. The incidence of bone cement leakage is calculated as follows: number of patients with bone cement leakage / total number of patients × 100%.
- Visual Analog Scale score preoperatively and at 1 week and 3, 6, 12, and 24 months postoperatively: The score ranges from 0 to 10. A higher score indicates more severe chest pain.
- Oswestry Disability Index preoperatively and at 1 week and 3, 6, 12, and 24 months postoperatively: This questionnaire contains 10 items: pain intensity, self-care, lifting, walking, sitting, standing, sleep disturbance, sex life, social life, and travel. Each item has six options. The highest score for each item is 5. A higher score indicates more severe dysfunction and a poorer quality of life.
- Compression rate of anterior vertebral height preoperatively and at 1 week and 3, 6, 12, and 24 months postoperatively: The original vertebral height before injury is defined as h. The heights of the upper and lower injured vertebral bodies are measured and defined as f and g, respectively; then h = (f + g) / 2. The anterior vertebral height will be measured preoperatively and 3 days postoperatively, defined as e and n, respectively; then the preoperative compression rate = (h − e) / h × 100%, and the postoperative compression rate = (h − n) / h × 100%.
- Thoracic morphology revealed by CT preoperatively and at 1 week and 3, 6, 12, and 24 months postoperatively: The restoration of the injured vertebra will be measured using chest CT.
- Incidence of adverse reactions at 1 week and 3, 6, 12, and 24 months postoperatively: The paravertebral tissue may be damaged by bone cement leakage. Therefore, adverse reactions may occur, such as spinal compression, intercostal neuralgia, bone cement leakage into the spinal space, paravertebral filling veins, arterial embolization, infection, secondary nerve injury, and loss of anterior vertebral height. The incidence of adverse reactions is equal to the number of patients with adverse reactions / total number of patients × 100%.
The schedule of outcome measurement assessments is shown in [Table 2].
Adverse reactions, shown in the secondary outcome measures, will be recorded. If severe adverse reactions occur, the investigators will report the details, including the date and type of occurrence and the measures taken to treat the adverse events, to the trial leader and the ethics committee within 24 hours.
A total of 378 patients with senile degenerative thoracic OVCF will be recruited from the Department of Orthopedics, Affiliated Hospital of Qinghai University, China. The patients will be randomized into PMMA and artificial bone groups (n = 189 per group) [Figure 2].
|Figure 2: Trial flow chart.|
Note: OVCF: Osteoporotic vertebral compression fracture; PKP: percutaneous kyphoplasty; PMMA: poly(methyl methacrylate); CT: computed tomography.
Click here to view
In accordance with previous study and our experience,, we hypothesize that the vertebral body height restoration rate at postoperative 24 months will be 90% in the PMMA group and 80% in the artificial bone group. Taking β = 0.2 and power = 80% with a significance level of α = 0.05, the final effective sample size of n = 157 per group will be calculated using PASS 11.0 software (PASS, Kaysville, UT, USA). If we assume a loss rate of 20%, we will include 189 patients per group, totally 378 patients.
All data will be analyzed using SPSS 18.0 software (IBM, Armonk, NY, USA) according to the intention-to-treat principle. Normally distributed measurement data will be expressed as the mean ± SD. Non-normally distributed measurement data will be expressed as the lower quartile (q1) and median and upper quartiles (q3). Enumeration data will be presented as percentages.
Selection of statistical methods
The vertebral body height restoration rate, incidence of bone cement leakage, compression rate of anterior vertebral height, and incidence of adverse reactions will be compared with Pearson’s chi-square test in both groups. Above data in each group at various time points will be compared using Kruskal-Wallis H test. Visual Analogue Scale score and Oswestry Disability Index will be compared between the two groups using independent sample t-test (normally distributed data) or Mann-Whitney U test (non-normally distributed data). Above data in each group at various time points will be compared using repeated measures analysis of variance. The significance level will be α = 0.05.
Included subjects will be assigned to the per protocol set. Per protocol set is a subset of the full analysis set, refers to the set of subjects who meet inclusion and exclusion criteria, complete the study without major protocol deviations, provide effective baseline efficacy and tight enough compliance, and fulfill the case report form.
Data collection and management
Case report forms will be recorded, collected and summarized. Above data will be recorded electronically using a double-data entry strategy.
The electronic database will be accessible and locked only by the project manager. This arrangement will not be altered. Only authorized researchers will be able to access the data. A professional statistician will statistically analyze the electronic database and create an outcome analysis report that will be submitted to the lead researchers. The Affiliated Hospital of Qinghai University of China will preserve all of the data regarding this trial.
Data monitoring committee composition
Before the start of the study, the data monitoring committee will have a meeting to review the committee charter and research plan. The committee will play a leading role in data monitoring to ensure the integrity of the research and protect the patient’s safety.
All surgeons participating in this study have a wealth of orthopedic surgery experience, including the professional leader, chief physician, and senior associate chief physician. Experimental data processing and statistical calculations will be performed by statisticians.
The auditors will confirm whether the records and reports of all data are correct and complete and whether all case report forms are correct and consistent with the original data. Changes in treatment, interim illness, loss to follow-up, and examination omissions for each patient will be confirmed and recorded.
Compensation to study participants
Patients participating in the trial will receive free laboratory examinations and imaging examinations included in the study protocol during follow-up. The hospital will allow professional doctors to receive free visits, closely follow up each patient’s condition, and reimburse each patient’s travel expenses.
Ethics and dissemination
This trial has been approved by the Medical Ethics Committee of Affiliated Hospital of Qinghai University of China. The study protocol will be conducted in accordance with the Declaration of Helsinki, formulated by the World Medical Association. The writing and editing of the article were performed in accordance with the Standard Protocol Item: Recommendations for Interventional Trail (SPIRIT) (Additional file 1 [Additional file 1]). Participants have provided signed informed consent prior to participation in the study. If and when any unexpected risk occurs during the clinical trial, informed consent-related content will be modified in accordance with the sponsor. After receiving agreement by the ethics committee, informed consent will be obtained again by the involved subjects or their guardians. Results will be disseminated through presentations at scientific meetings and/or by publication in a peer-reviewed journal. Anonymized trial data will be published at www.figshare.com.
| Trial Status|| |
This study protocol was designed in December 2017 and patient recruitment will begin in July 2018.
| Discussion|| |
Contributions and problems of previous studies in this field
PMMA bone cement is commonly used in PKP for the treatment of senile degenerative thoracic OVCF. PMMA has good plasticity and formability. However, some scholars have found that PMMA bone cement has some disadvantages: it readily produces heat during the polymerization, probably decomposes to produce toxic methyl methacrylate monomer, and has poor biocompatibility. However, these limitations have not been confirmed by other clinical research.
geneX® injectable artificial bone is a novel vertebral body filling material, the main components of which are calcium phosphate and calcium sulfate. The artificial bone can absorb aggregated molecules and proteins after special polarization and can induce bone formation. geneX® injectable artificial bone is currently used in PKP for the treatment of thoracic OVCF, and its short-term effect is good.
Features of this study protocol
OSTEOPAL® plus PMMA is a novel low-viscosity bone cement material with many advantages in filling and fixing vertebrae. PMMA bone cement contains the X-ray contrast agent zirconium dioxide to improve the clarity of postoperative imaging. It also contains copper chlorophyll (E141), which can improve the visibility at the surgical area, allow for accurate observation of bone cement leakage after the operation, and improve the stability of the vertebral body. Few prospective randomized controlled trials have been performed to assess the treatment of vertebral fractures with this material.
Limitations of this study
The lack of an allocation concealment or blinding method and short follow-up time will affect the accuracy of the results.
Significance of this study
This prospective randomized controlled trial will reveal the efficacy and biocompatibility of OSTEOPAL® plus PMMA bone cement and geneX® injectable artificial bone implantation in the treatment of senile degenerative thoracic OVCF in the short term and until the 2-year follow-up. This trial will help clinicians to select suitable filling materials for PKP and thus improve the stability of the vertebral body and develop a good surgical plan.
Additional file 1: SPIRIT checklist.
Study design and manuscript writing: YZ. Subject recruitment: RR. Data collection and analysis: YZ, RR, ZQL, YBH and ML. All authors approve the final version of the manuscript.
Conflicts of interest
The authors declare that the use of medical device-related funding in clinical trials does not affect the authors’ opinions or reports on the results of the data (medical devices: OSTEOPAL® plus poly(methyl methacrylate) bone cement and geneX® injectable artificial bone).
This trial has been approved by the Medical Ethics Committee of Affiliated Hospital of Qinghai University of China. The study followed international and national regulations in accordance with the Declaration of Helsinki and relevant ethical principles.
Declaration of patient consent
The authors certify that they will obtain patient consent forms. In the form, patients will give their consent for their images and other clinical information to be reported in the journal. The patients will understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Data sharing statement
Individual participant data that underlie the results reported in this article, after deidentification (text, tables, figures, and appendices) will be in particular shared. Study protocol and informed consent form will be available. The data will be available immediately following publication without end date. Results will be disseminated through presentations at scientific meetings and/or by publication in a peer-reviewed journal. Anonymized trial data will be available indefinitely at www.figshare.com.
Checked twice by iThenticate.
Externally peer reviewed.
| References|| |
Li X, Lu Y, Lin X. Refracture of osteoporotic vertebral body after treatment by balloon kyphoplasty: Three cases report. Medicine (Baltimore)
Pfeifer M, Gehlen M, Hinz C. Spinal orthoses in the treatment of vertebral fractures with osteoporosis: a systematic review article. Z Rheumatol
Schnake KJ, Bula P, Spiegl UJ, et al. Thoracolumbar spinal fractures in the elderly: Classification and treatment. Unfallchirurg
Hajnovic L, Sefranek V, Schütz L. Influence of blood supply on fracture healing of vertebral bodies. Eur J Orthop Surg Traumatol
. 2017. doi: 10.1007/s00590-017-2069-7.
Ye LQ, Liang, Jiang XB, et al. Risk factors for the occurrence of insufficient cement distribution in the fractured area after percutaneous vertebroplasty in osteoporotic vertebral compression fractures. Pain Physician
Youn MS, Shin JK, Goh TS, et al. Minimally invasive percutaneous endoscopic treatment for acute pyogenic spondylodiscitis following vertebroplasty. Eur Spine J
. 2018. doi: 10.1007/s00586-018-5478-3.
Lim J, Choi SW, Youm JY, et al. Posttraumatic delayed vertebral collapse: kummell’s disease. J Korean Neurosurg Soc
. 2018. doi: 10.3340/jkns.2017.0505.010.
Beall DP, Tutton SM, Murphy K, et al. Analysis of reporting bias in vertebral augmentation. Pain Physician
Leali PT, Solla F, Maestretti G, et al. Safety and efficacy of vertebroplasty in the treatment of osteoporotic vertebral compression fractures: a prospective multicenter international randomized controlled study. Clin Cases Miner Bone Metab
Ge FT, Zhao S, Niu F, et al. Treatment of osteoporotic vertebral fractures with percutaneous balloon kyphoplasty using calcium phosphate cement. Zhongguo Gushang
Wang H, Zhang Z, Liu Y, Jiang W. Percutaneous kyphoplasty for the treatment of very severe osteoporotic vertebral compression fractures with spinal canal compromise. J Orthop Surg Res
Jin C, Xu G, Weng D, et al. Impact of magnetic resonance imaging on treatment-related decision making for osteoporotic vertebral compression fracture: a prospective randomized trial. Med Sci Monit
Yılmaz A, Çakır M, Yücetaş CŞ, et al. Percutaneous kyphoplasty, is bilateral approach necessary? Spine (Phila Pa 1976)
. 2017. doi: 10.1097/BRS.0000000000002531.
Jia-Jia S, Zhi-Yong S, Zhong-Lai Q, et al. Tuberculous spondylitis after vertebral augmentation: a case report with a literature review. J Int Med Res
. 2017. doi: 10.1177/0300060517728008.
Shang LP, Tian Y, Liu XG. Clinical comparison of polymethylmeth- acrylate and bone cement in the treatment of osteoporotic vertebral compression fractures: a retrospective study. Beijing Da Xue Xue Bao Yi Xue Ban
Xu BS, Hu YC, Yang Q, Xia Q, Ma XL, Ji N. Long-term results and radiographic findings of percutanous vertebroplasties with polymethylmethacrylate for vertebral osteoporotic fractures. Chin Med J (Engl)
Hu M, Ma H, Shi H, et al. Early clinical outcome of manual reduction combined with uni-lateral percutaneous kyphoplasty to treat osteoporotic vertebral compression fracture. Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi
Yan L, He B, Guo H, et al. The prospective self-controlled study of unilateral transverse process-pedicle and bilateral puncture techniques in percutaneous kyphoplasty. Osteoporos Int
Yin F, Sun Z, Song S, et al. A comparative study on treatment of mid-thoracic osteoporotic vertebral compression fracture using percutaneous kyphoplasty with unilateral and bilateral approaches. Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi
Knop C, Oeser M, Bastian L, et al. Development and validation of the Visual Analogue Scale (VAS) Spine Score. Unfallchirurg
Ruiz FK, Bohl DD, Webb ML, et al. Oswestry Disability Index is a better indicator of lumbar motion than the Visual Analogue Scale. Spine J
Yang HL, Niu GQ, Liang DC, et al. The contrast study between single and double balloon bilateral dilatation of kyphoplasty. Zhonghua Waike Zazhi
Xing WZ, Zhang ZG, Liu CC, et al. Minidose bone cement injection for osteoporotic compression fractures of vertebrae in senior patients. Zhonghua Chuangshang Guke Zazhi
Yang H, Observation of the effect of GENEX enhanced surgery on the prevention of adjacent vertebral refracture after multiple vertebroplasty. Beijing: Capital Medical University. 2015.
[Figure 1], [Figure 2]
[Table 1], [Table 2]