Vertebroplasty and kyphoplasty: filler materials

Modified and alternative bone cements can improve the induced membrane: Critical size bone defect model in rat femur

BACKGROUND

As a two-stage surgical procedure, Masquelet's technique has been used to care for critical-size bone defects (CSD). We aimed to determine the effects of modified and altered bone cement with biological or chemical enriching agents on the progression of Masquelet's induced membrane (IM) applied to a rat femur CSD model, and to compare the histopathological, biochemical, and immunohistochemical findings of these cements to enhance IM capacity.

METHODS

Thirty-five male rats were included in five groups: plain polymethyl methacrylate (PMMA), estrogen-impregnated PMMA (E+PMMA), bone chip added PMMA (BC+PMMA), hydroxyapatite-coated PMMA (HA) and calcium phosphate cement (CPC). The levels of bone alkaline phosphatase (BALP), osteocalcin (OC), and tumor necrosis factor-alpha (TNF-α) were analyzed in intracardiac blood samples collected at the end of 4 weeks of the right femur CSD intervention. All IMs collected were fixed and prepared for histopathological scoring. The tissue levels of rat-specific Transforming Growth Factor-Beta (TGF-β), Runt-related Transcription Factor 2 (Runx2), and Vascular Endothelial Growth Factor (VEGF) were analyzed immunohistochemically.

RESULTS

Serum levels of BALP and OC were significantly higher in E+PMMA and BC+PMMA groups than those of other groups (P = 0.0061 and 0.0019, respectively). In contrast, TNF-α levels of all groups with alternative bone cement significantly decreased compared to bare PMMA (P = 0.0116). Histopathological scores of E+PMMA, BC+PMMA, and CPC groups were 6.86 ± 1.57, 4.71 ± 0.76, and 6.57 ± 1.51, respectively, which were considerably higher than those of PMMA and HA groups (3.14 ± 0.70 and 1.86 ± 0.69, respectively) (P < 0.0001). Significant increases in TGF-β and VEGF expressions were observed in E+PMMA and CPC groups (P = 0.0001 and <0.0001, respectively) whereas Runx2 expression significantly increased only in the HA group compared to other groups (P < 0.0001).

CONCLUSIONS

The modified PMMA with E and BC, and CPC as an alternative spacer resulted in a well-differentiated IM and increased IM progression by elevating BALP and OC levels in serum and by mediating expressions of TGF-β and VEGF at the tissue level. Estrogen-supplemented cement spacer has yielded promising findings between modified and alternative bone cement.

Radiopacity Enhancements in Polymeric Implant Biomaterials: A Comprehensive Literature Review

Polymers as biomaterials possess favorable properties, which include corrosion resistance, light weight, biocompatibility, ease of processing, low cost, and an ability to be easily tailored to meet specific applications. However, their inherent low X-ray attenuation, resulting from the low atomic numbers of their constituent elements, i.e., hydrogen (1), carbon (6), nitrogen (7), and oxygen (8), makes them difficult to visualize radiographically. Imparting radiopacity to radiolucent polymeric implants is necessary to enable noninvasive evaluation of implantable medical devices using conventional imaging methods. Numerous studies have undertaken this by blending various polymers with contrast agents consisting of heavy elements. The selection of an appropriate contrast agent is important, primarily to ensure that it does not cause detrimental effects to the relevant mechanical and physical properties of the polymer depending upon the intended application. Furthermore, its biocompatibility with adjacent tissues and its excretion from the body require thorough evaluation. We aimed to summarize the current knowledge on contrast agents incorporated into synthetic polymers in the context of implantable medical devices. While a single review was found that discussed radiopacity in polymeric biomaterials, the publication is outdated and does not address contemporary polymers employed in implant applications. Our review provides an up-to-date overview of contrast agents incorporated into synthetic medical polymers, encompassing both temporary and permanent implants. We expect that our results will significantly inform and guide the strategic selection of contrast agents, considering the specific requirements of implantable polymeric medical devices.

Management of metastatic bone disease of the pelvis: current concepts

PURPOSE

Metastatic disease of the pelvis is frequently associated with severe pain and impaired ambulatory function. Depending on the patient's characteristics, primary tumor, and metastatic pelvic disease, the treatment choice may be varied. This study aims to report on the current management options of metastatic pelvic disease.

METHODS

We comprehensively researched multiple databases and evaluated essential studies about current concepts of managing a metastatic bone disease of the pelvis, focusing on specific indications as well as on the result of treatment.

RESULTS

Pelvic metastases not in the periacetabular region can be managed with modification of weight-bearing, analgesics, bisphosphonates, chemotherapy and/or radiotherapy. Minimally invasive approaches include radiofrequency ablation, cryoablation, embolization, percutaneous osteoplasty, and percutaneous screw placement. Pathological or impending periacetabular fracture, excessive periacetabular bone defect, radioresistant tumor, and persistent debilitating pain despite non-surgical treatment and/or minimally invasive procedures can be managed with different surgical techniques. Overall, treatment can be divided into nonoperative, minimally invasive, and operative based on specific indications, the expectations of the patient and the lesion.

CONCLUSION

Different treatment modalities exist to manage metastatic pelvic bone disease. Decision-making for the most appropriate treatment should be made with a multidisciplinary approach based on a case-by-case basis.

Spinal medial branch nerve root block (MBNB) intervention compared to standard care-vertebroplasty (VP) for the treatment of painful osteoporotic vertebral fractures in frail, older hospitalised patients: a feasibility study

Our study aimed to assess the feasibility outcomes comparing spinal medial branch nerve root block intervention to standard care vertebroplasty for the treatment of painful osteoporotic vertebral fractures in frail, hospitalised older patients. We found the study to be feasible and now propose a clinical effectiveness, cost effectiveness and safety evaluation.

INTRODUCTION

Vertebroplasty (VP) is a key-hole procedure involving injection of bone cement into a fractured vertebral body, to reduce pain and increase vertebral body stability, although it is associated with a small risk of complications, particularly in frail, older hospitalised patients. Medial branch spinal nerve block (MBNB) may be an alternative treatment to alleviate pain symptoms, with less complications; however, no study has prospectively compared the clinical effectiveness, cost-effectiveness and safety of MBNB to VP, in frail, older hospitalised patients. The aim of our study was to conduct a 1st stage feasibility study, exploring recruitment, retention and several outcomes measures (means and SDs), together with qualitative interviews to assess participant and clinician views, to inform a definitive larger study.

METHODS

We conducted a two-arm feasibility randomised controlled trial with participants allocated to continue with routine surgical care-VP or MBNB treatment, with an embedded qualitative study. Data was collected at baseline, week 1, 4, and week 8.

RESULTS

Out of 40 eligible patients, 30 (75%) consented to take part in the study. The overall median time from randomisation to intervention was 3 days, IQR 1-7 days, 5 (1-7) days for VP and 2 (1-3) days for MBNB. Median (IQR) length of hospital stay for the VP group was 20 (8) days and for the MBNB 15(22) days. The proportion of completeness of outcome data collection at weeks 1, 4 and 8 was at least 77%: 14 (100%), 12 (85.7%) and 11(78.9%) for VP and 13 (100%), 12 (92.3%) and 10 (76.8%) for MBNB, respectively. There were no significant difference in the clinical outcomes or adverse events between the two groups.

DISCUSSION

Our study was feasible in achieving is target recruitment, participants adhered to the randomisation and at least 77% completeness of data at the 8 week end-point (target 75%). We now plan to conduct a definitive clinical effectiveness, cost effectiveness and safety outcome study, comparing VP to MBNB in frail, older patients hospitalised with an acute vertebral osteoporotic fracture.

New Research Progress of Modified Bone Cement Applied to Vertebroplasty

Percutaneous vertebroplasty and percutaneous kyphoplasty are effective methods to treat acute osteoporotic vertebral compression fractures that can quickly provide patients with pain relief, prevent further height loss of the vertebral body, and help correct kyphosis. Many clinical studies have investigated the characteristics of bone cement. Bone cement is a biomaterial injected into the vertebral body that must have good biocompatibility and biosafety. The optimization of the characteristics of bone cement has become of great interest. Bone cement can be mainly divided into 3 types: polymethyl methacrylate, calcium phosphate cement, and calcium sulfate cement. Each type of cement has its own advantages and disadvantages. In the past 10 years, the performance of bone cement has been greatly improved via different methods. The aim of our review is to provide an overview of the current progress in the types of modified bone cement and summarize the key clinical findings.

Effect of different bone cement distributions in percutaneous kyphoplasty on clinical outcomes for osteoporotic vertebral compression fractures: A retrospective study

Osteoporotic fractures and their complications are becoming increasingly harmful to the elderly. This study aimed to evaluate the clinical results of connected or unconnected bilateral cement after bilateral percutaneous kyphoplasty (PKP) in patients with osteoporotic vertebral compression fractures (OVCF). The clinical data of 217 patients with single-segment OVCF were retrospectively collected. Patients were allocated into 2 groups according to the bilateral bone cement in the vertebrae was connected or unconnected after surgery. The surgery-related indexes of the 2 groups were compared, including operation time; bone cement injection volume; contact situation between bone cement and the upper and lower endplates of the vertebral body; visual analogue scale (VAS) scores before surgery, 1 week and 1 year after surgery; Oswestry disability index (ODI) before surgery, 1 week and 1 year after surgery; local kyphosis angle (LKA) before surgery, 1 week and 1 year after surgery; postoperative vertebral body height at 1 week and 1 year after surgery; vertebral body height restoration rate (HRR) at 1 week and 1 year after surgery. The follow-up results of all patients were recorded. The postoperative VAS, ODI, vertebral body height, LKA and other indexes of the 2 groups were significantly improved compared with those before the operation (P < .05), and there was no significant difference between the 2 groups (P > .05). At the same time, there were no significant difference in vertebral body HRR and bone cement leakage rate between the 2 groups (P > .05). X-ray examination showed that 21 of 217 patients (21/217, 9.8%) had a refracture of the injured vertebral body, including 16 cases (16/121, 13.2%) in the unconnected group and 5 cases (5/96, 5.2%) in the connected group (P < .05). Adjacent vertebrae fractures occurred in 25 cases (25/217, 11.5%), while 19 cases (19/121, 15.7%) were in the unconnected group and 6 cases (6/96, 6.3%) were in the connected group (P < .05). PKP has a good therapeutic effect on OVCF no matter whether the bilateral bone cement is connected or not. However, if the bilateral cement inside the vertebra was connected, the risk of recollapse of the injured vertebrae and the new fracture of adjacent vertebrae could be reduced.

Application of machine learning in prediction of bone cement leakage during single-level thoracolumbar percutaneous vertebroplasty

BACKGROUND

In the elderly, osteoporotic vertebral compression fractures (OVCFs) of the thoracolumbar vertebra are common, and percutaneous vertebroplasty (PVP) is a common surgical method after fracture. Machine learning (ML) was used in this study to assist clinicians in preventing bone cement leakage during PVP surgery.

METHODS

The clinical data of 374 patients with thoracolumbar OVCFs who underwent single-level PVP at The First People's Hospital of Chenzhou were chosen. It included 150 patients with bone cement leakage and 224 patients without it. We screened the feature variables using four ML methods and used the intersection to generate the prediction model. In addition, predictive models were used in the validation cohort.

RESULTS

The ML method was used to select five factors to create a Nomogram diagnostic model. The nomogram model's AUC was 0.646667, and its C value was 0.647. The calibration curves revealed a consistent relationship between nomogram predictions and actual probabilities. In 91 randomized samples, the AUC of this nomogram model was 0.7555116.

CONCLUSION

In this study, we invented a prediction model for bone cement leakage in single-segment PVP surgery, which can help doctors in performing better surgery with reduced risk.

Fabrication of Radio-Opaque and Macroporous Injectable Calcium Phosphate Cement

The aim of this work was the development of injectable radio-opaque and macroporous calcium phosphate cement (CPC) to be used as a bone substitute for the treatment of pathologic vertebral fractures. A CPC was first rendered radio-opaque by the incorporation of zirconium dioxide (ZrO₂). In order to create macroporosity, poly lactic-co-glycolic acid (PLGA) microspheres around 100 μm were homogeneously incorporated into the CPC as observed by scanning electron microscopy. Physicochemical analyses by X-ray diffraction and Fourier transform infrared spectroscopy confirmed the brushite phase of the cement. The mechanical properties of the CPC/PLGA cement containing 30% PLGA (wt/wt) were characterized by a compressive strength of 2 MPa and a Young's modulus of 1 GPa. The CPC/PLGA exhibited initial and final setting times of 7 and 12 min, respectively. Although the incorporation of PLGA microspheres increased the force necessary to inject the cement and decreased the percentage of injected mass as a function of time, the CPC/PLGA appeared fully injectable at 4 min. Moreover, in comparison with CPC, CPC/PLGA showed a full degradation in 6 weeks (with 100% mass loss), and this was associated with an acidification of the medium containing the CPC/PLGA sample (pH of 3.5 after 6 weeks). A cell viability test validated CPC/PLGA biocompatibility, and in vivo analyses using a bone defect assay in the caudal vertebrae of Wistar rats showed the good opacity of the CPC through the tail and a significant increased degradation of the CPC/PLGA cement a month after implantation. In conclusion, this injectable CPC scaffold appears to be an interesting material for bone substitution.

Innovation of Surgical Techniques for Screw Fixation in Patients with Osteoporotic Spine

Osteoporosis is a common disease in elderly populations and is a major public health problem worldwide. It is not uncommon for spine surgeons to perform spinal instrumented fusion surgeries for osteoporotic patients. However, in patients with severe osteoporosis, instrumented fusion may result in screw loosening, implant failure or nonunion because of a poor bone quality and decreased pedicle screw stability as well as increased graft subsidence risk. In addition, revision surgeries to correct failed instrumentation are becoming increasingly common in patients with osteoporosis. Therefore, techniques to enhance the fixation of pedicle screws are required in spinal surgeries for osteoporotic patients. To date, various instrumentation methods, such as a supplemental hook, sublaminar taping and sacral alar iliac screws, and modified screwing techniques have been available for reinforcing pedicle screw fixation. In addition, several materials, including polymethylmethacrylate and hydroxyapatite stick/granules, for insertion into prepared screw holes, can be used to enhance screw fixation. Many biomechanical tests support the effectiveness of these augmentation methods. We herein review the current therapeutic strategies for screw fixation and augmentation methods in the surgical treatment of patients with an osteoporotic spine.

Review of Biomechanical Studies and Finite Element Modeling of Sternal Closure Using Bio-Active Adhesives

The most common complication of median sternotomy surgery is sternum re-separation after sternal fixation, which leads to high rates of morbidity and mortality. The adhered sternal fixation technique comprises the wiring fixation technique and the use of bio-adhesives. Adhered sternal fixation techniques have not been extensively studied using finite element analysis, so mechanical testing studies and finite element analysis of sternal fixation will be presented in this review to find the optimum techniques for simulating sternal fixation with adhesives. The optimal wiring technique should enhance bone stability and limit sternal displacement. Bio-adhesives have been proposed to support sternal fixation, as wiring is prone to failure in cases of post-operative problems. The aim of this paper is to review and present the existing numerical and biomechanical sternal fixation studies by reviewing common sternal closure techniques, adhesives for sternal closure, biomechanical modeling of sternal fixation, and finite element modeling of sternal fixation systems. Investigating the physical behavior of 3D sternal fixation models by finite element analysis (FEA) will lower the expense of conducting clinical trials. This indicates that FEA studies of sternal fixation with adhesives are needed to analyze the efficiency of this sternal closure technique virtually.

Reinforcement of Percutaneous Pedicle Screw Fixation with Hydroxyapatite Granules in Patients with Osteoporotic Spine: Biomechanical Performance and Clinical Outcomes

In percutaneous pedicle screw (PPS) fixation of the osteoporotic spine, rigid screw fixation obtaining strong stabilization is important for achieving successful treatment outcomes. However, in patients with severe osteoporosis, it is difficult to obtain PPS fixation with sufficient stability. PPS fixation has potential disadvantages with respect to maintaining secure stabilization in comparison to conventional pedicle screw fixation. In PPS fixation, bone grafting to achieve posterior spine fusion is generally not applicable and transverse connectors between the rods cannot be used to reinforce the fixation. Various augmentation methods, including additional hooks, sublaminar bands, and hydroxyapatite (HA) sticks, are available for conventional pedicle screw fixation. On the other hand, there has been no established augmentation method for PPS fixation. Recently, we developed a novel augmentation technique for PPS fixation using HA granules. This technique allows the percutaneous insertion of HA granules into the screw hole along the guidewire prior to insertion of the PPS. We have used this augmentation technique for PPS fixation in various spine surgeries in patients with osteoporosis. In our previous studies, biomechanical analyses demonstrated that PPS fixation was significantly enhanced by augmentation with HA granules in the osteoporotic lumbar spine. Furthermore, augmentation with HA granules was considered to decrease the incidence of screw loosening and implant failure following PPS fixation in patients with osteoporotic spine. In this article, we describe the surgical procedures of the augmentation method using HA granules and summarize our data from the biomechanical analysis of augmentation for PPS fixation. We also review the surgical outcomes of PPS fixation with augmentation using HA granules.

The Biomechanical Properties of Cement-Augmented Pedicle Screws for Osteoporotic Spines

STUDY DESIGN

This is a broad, narrative review of the literature.

OBJECTIVE

In this review, we describe recent biomechanics studies on cement-augmented pedicle screws for osteoporotic spines to determine which factors influence the effect of cement augmentation.

METHODS

A search of Medline was performed, combining the search terms "pedicle screw" and ("augmentation" OR "cement"). Articles published in the past 5 years dealing with biomechanical testing were included.

RESULTS

Several factors have been identified to impact the effect of cement augmentation in osteoporotic spines. These include the type of augmentation material, the volume of injected cement, the timing of augmentation, the severity of osteoporosis, the design of the pedicle screw, and the specific augmenting technique, among others.

CONCLUSIONS

This review elaborates the biomechanics of cement-augmented pedicle screws, determines which factors influence the augmentation effect, and identifies the risk factors of cement leakage in osteoporotic bone, which might offer some guidance when using this technique in clinical practice. Further, we provide information about newly designed screws and recently developed augmentation materials that provide higher screw stability as well as fewer cement-related complications.

Nanostructured Zn-Substituted Monetite Based Material Induces Higher Bone Regeneration Than Anorganic Bovine Bone and β-Tricalcium Phosphate in Vertical Augmentation Model in Rabbit Calvaria

The capacity of a nanostructured multicomponent material composed of Zn-substituted monetite, amorphous calcium phosphate, hydroxyapatite and silica gel (MSi) to promote vertical bone augmentation was compared with anorganic bovine bone (ABB) and synthetic β-tricalcium phosphate (β-TCP). The relation between biological behavior and physicochemical properties of the materials was also studied. The in vivo study was conducted in a vertical bone augmentation model in rabbit calvaria for 10 weeks. Significant differences in the biological behavior of the materials were observed. MSi showed significantly higher bone regeneration (39%) than ABB and β-TCP (24%). The filled cylinder volume was similar in MSi (92%) and ABB (91%) and significantly lower in β-TCP (81%) implants. In addition, β-TCP showed the highest amount of non-osteointegrated particles (17%). MSi was superior to the control materials because it maintains the volume of the defect almost full, with the highest bone formation, the lowest number of remaining particles, which are almost fully osteointegrated and having the lowest amount of connective tissue. Besides, the bone formed was mature, with broad trabeculae, high vascularization and osteogenic activity. MSi resorbs gradually over time with an evident increment of the porosity and simultaneous colonization for vascularized new bone. In addition, the osteoinductive behavior of MSi material was evidenced.

Translation of a spinal bone cement product from bench to bedside

Spinal acrylic bone cements (ABCs) are used clinically for percutaneous vertebroplasty (PVP) and kyphoplasty (PKP) to treat osteoporotic vertebral compression fractures. Product translation of spinal ABC products followed the design control processes including design verification and validation. The bench to bedside translation of the first Chinese spinal ABC product (Alliment®, namely Alliment Cement) approved by National Medical Products Administration of China was investigated and another commercial product served as the control (Osteopal®V, namely Osteopal V Cement). Results of non-clinical bench performance verification tests of compression, bending and monomer release showed that the newly marketed Alliment Cement is similar to the Osteopal V Cement with properties of both meeting the criteria specified by standards. The Alliment Cement demonstrated good biocompatibility during the 26 weeks’ bone implantation test. Porcine cadaver validation tests further revealed that the Alliment Cement satisfied the needs for both PVP and PKP procedures. A post-approval, retrospective clinical investigation further demonstrated the safety and efficacy of the Alliment Cement, with a significant reduction of pain and the improved stability of the fractured vertebral bodies. A successful translation of biomaterial medical products needs close collaborations among academia, industry, healthcare professionals and regulatory agencies.

•

Bench-to-bedside research of the first Chinese spinal acrylic bone cement product.

•Pre- & clinical investigations demonstrate the product's safety and efficacy.

•Translation of biomaterial medical products follows regulated processes.

En Bloc Resection for a Malignant Spine Tumor After Balloon Kyphoplasty: Histological Findings of a Retrieved Vertebral Body: A Case Report

CASE

A 45-year-old woman with severe back pain underwent percutaneous curettage and balloon kyphoplasty (BKP) of a lesion believed to be aneurysmal bone cyst. Three months after BKP, local recurrence was observed, and the histological diagnosis was revised to malignant tumor. Thus, we performed a total en bloc spondylectomy, and the L3 vertebral body was resected. She was reconstructed by titanium expandable cage, rod, and pedicle screws. We observed viable tumor cells and foreign body reaction adjacent to the polymethylmethacrylate cement, carrying no bone necrosis.

CONCLUSIONS

The long-term durability and safety of BKP for metastatic spine disease should be further clarified.

Comparison between vertebroplasty with high or low viscosity cement augmentation or kyphoplasty in cement leakage rate for patients with vertebral compression fracture: a systematic review and network meta-analysis

PURPOSE

This study aims to determine whether outcomes following vertebroplasty with high viscosity cement are superior to low viscosity cement and non-inferior to kyphoplasty in the setting of vertebral compression fractures.

METHODS

We searched for randomized controlled trials and cohort studies assessing cement leakage rate in adult patients with VCFs who underwent vertebroplasty with high (HVCV) or low viscosity cement (LVCV) augmentation, or kyphoplasty (KP) in PubMed, Embase, Ovid, The Cochrane Library, and Web of Science from inception up to December 2019. Two authors extracted data and appraised risk of bias. We performed pairwise meta-analyses in R to compare differences between three treatments and network meta-analysis using frequentist random-effects models for indirect comparison. We used P-score to rate the overall certainty of evidence. The primary outcome was cement leakage rate.

RESULTS

Five RCTs and eight cohort studies with 840 patients and a total of 1280 vertebral bodies were included in the systematic review and network meta-analysis. Compared to LVCV, the relative risk for cement leakage following HVCV and KP was 0.42 (95% CI 0.28-0.61) and 0.83 (95% CI 0.40-1.68), respectively. Our pooled results suggested that HVCV (P-score = 0.99) was better than KP (P-score = 0.36) in cement leakage rate.

CONCLUSIONS

The present network meta-analysis demonstrated that HVCV may be associated with lower risk of cement leakage among patients with VCFs as compared to other augmentation techniques. Future prospective studies will validate the findings of this analysis and further elucidate the risk of symptomatic cement leakage.

Resomer C212© in vertebroplasty or kyphoplasty: A feasibility study on artificial bones with biomechanical and thermal evaluation

BACKGROUND

Vertebroplasty and kyphoplasty are now well-established methods for treating compression fractures of vertebral bodies (AO type A) as well as vertebral body metastases [1, 2, 3]. However, polymethylmethacrylate (PMMA) augmented vertebrae show fractures of subsequent vertebral bodies due to the increased stability of the augmented vertebral body [4]. Resorbable cements are currently only used experimentally. Many commercially available resorbable calcium phosphate cements do not exhibit sufficient biomechanical stability to treat vertebral body fractures [5]. Resomer C212© (Evonik Industries AG, Essen, Germany) is a slow resorbable poly-ε-caprolactone that has low melting temperatures and good biomechanical properties.

OBJECTIVE

This is a feasibility study on how the poly-ε-caprolactone Resomer C212© can be used for kypho- or vertebroplasty, what temperatures are used in the argumentation and how differences in load capacity are measurable compared to conventional PMMA cement.

METHODS

23 Sawbones© blocks (7.5 Open Cell Foam, SKU: 1522-09, laminated on both sides, 4 × 4 × 2.9 cm, Sawbones, Vashon Island, USA) were divided into three groups: 7 without augmentation, 8 augmented with PMMA cement Traumacem V+© (DePuy Synthes, West Chester, USA) and 8 augmented with Resomer C212©. Temperature measurements were made in a 37∘C water bath centrally in the block and on the top and bottom plates. This was followed by a maximum load of up to 2000 N using a universal testing machine (Instron E 10000, Instron Industrial Products, Grove City, USA).

RESULTS

In the Resomer C212© test group, the maximum average increase in temperature was 4.15 ± 4.72∘C central, 0.3 ± 0.31∘C at the top and 0.78 ± 1.27∘C at the base. In the cement test group, the average increase in temperature was 9.80 ± 10.65∘C centrally in the test block, 1.50 ± 0.73∘C at the top plate and 1.42 ± 0.66∘C and the base plate. In the axial compression test, the 7 non-kyphoplasted test blocks showed a first loading peak on average at 275.23 ± 80.98 N, a rigidity of 238.47 ± 71.01 N/mm2. In the Traumacem V+© group, the mean peak load was 313.72 ± 46.26 N and rigidity was 353.45 ± 77.23 N/mm2. The Resomer C212© group achieved a peak load of 311.74 ± 52.05 N and a stiffness of 311.30 ± 126.63 N/mm2. A compression to 50% could not be seen in any test block under the load of 2000 N. At 2000 N, Traumacem V+©'s average height reduction was 9.26 ± 2.16 mm and Resomer C212© was 10.93 ± 0.81 mm.

CONCLUSIONS

It has been shown that the application of Resomer C212© in kyphoplasty or vertebroplasty is well feasible. Thermal analysis showed significantly lower temperatures and shorter temperature application in the Resomer C212© group. In the biomechanical load up to 2000 N no significant differences could be observed between the individual groups.

[Vertebroplasty and kyphoplasty : A critical statement]

BACKGROUND

Despite optimal drug-conservative therapy, a relevant percentage of patients with vertebral compression fractures (WKF) do not experience any relevant improvement in their pain symptoms. Vertebroplasty (VP) and kyphoplasty (KP) are described in the literature as percutaneous interventional procedures for the treatment of WKF.

OBJECTIVE

Assessment of the effectiveness of the VP and KP in the treatment of WKF and discussion of the procedures in the context of the current literature.

MATERIAL AND METHODS

Presentation of the fundamentals of VP and KP and their further developments. Description of indications and contraindications. Discussion of the current literature and recommendations of the individual professional associations.

RESULTS

In patients with vertebral compression fractures, VP or KP of the affected vertebral body leads to a pain reduction in more than 90% of cases. Clinically relevant complications occur in less than 1% of interventions.

CONCLUSION

VP and KP are a safe and effective method for treating painful WKF. Optimal patient selection improves the clinical outcome.

A Prospective Study on the Feasibility, Safety, and Efficacy of a Modified Technique to Augment the Strength of Pedicle Screw in Osteoporotic Spine Fixation

Study Design

Prospective case study.

Purpose

Osteoporotic spine fixation by pedicle screw instrumentation is complicated by screw loosening, migration, or pullout with rates of up to 62% documented in the literature. Contemporary solutions have not adequately addressed these complications. We propose a modified surgical technique of cement augmentation with bicortical pedicle screw fixation to address the issue related to implant failure in osteoporotic spine.

Overview of Literature

Zindrick and his colleagues described a “windshield wiper” effect owing to the shift of center of rotation to the distal tip of the screw in the bicortical purchase of screws. An increase in pullout strength from 119% to 250% with polymethyl methacrylate augmentation has been documented in the literature. This technique has not been described in the literature.

Methods

A prospective study was conducted with 40 patients who underwent surgery by the modified technique. Intraoperative and postoperative complications directly related to the procedure were assessed. Improvement in pain and functional status were assessed. Follow-up radiographs were assessed to check for appreciable screw migration, loosening, or pullout.

Results

This technique was used in inserting 364 screws in 40 patients. We did not encounter any difficulty in inserting the screws. A total of 19 screws failed to breach the anterior cortex owing to an error in measurement. There were no complications during the procedure in any of the patients, and the postoperative period was uneventful. The mean follow-up period was 18 months. There were two patients in whom proximal junctional failure with kyphosis was noted during follow-up, who were surgically managed by extension of the fixation levels.

Conclusions

Bicortical fixation with cement augmentation is a technically feasible, safe, and effective technique to augment the strength of pedicle screws in osteoporotic spine fixation. It has the potential to be established as a standard of care in osteoporotic spine fixation.

Biomechanical evaluation of calcium phosphate-based nanocomposite versus polymethylmethacrylate cement for percutaneous kyphoplasty

BACKGROUND CONTEXT

Polymethylmethacrylate (PMMA) is the most commonly used filling material when performing percutaneous kyphoplasty (PKP) for the treatment of osteoporotic vertebral compression fractures. However, there are some inherent and unavoidable drawbacks with the clinical use of PMMA. PMMA bone cement tends to leak during injection, which can lead to injury of the spinal nerves and spinal cord. Moreover, the mechanical strength of PMMA-augmented vertebral bodies is extraordinary and this high level of mechanical strength might predispose to adjacent vertebral fractures. A novel biodegradable calcium phosphate-based nanocomposite (CPN) for PKP augmentation has recently been developed to potentially avoid these issues.

PURPOSE

By comparison with PMMA, the leakage characteristics, biomechanical properties, and dispersion of CPN were evaluated when used for PKP.

STUDY DESIGN

Biomechanical evaluation and studies on the dispersion and anti-leakage properties of CPN and PMMA cements were performed and compared using cadaveric vertebral fracture model, sheep vertebral fracture model, and simulated rigid foam model.

METHODS

Sheep vertebral bodies were decalcified by ethylenediaminetetraacetic acid disodium salt (EDTA-Na₂) to simulate osteoporosis in vitro. After compression to create wedge-shaped fractures using a self-designed fracture creation tool, human cadaveric vertebrae and decalcified sheep vertebrae were augmented by PKP. In addition, three L5 vertebral bodies from human cadavers were used in a contrast vertebroplasty (VP) augmentation experiment. Occurrence of cement leakage was observed and compared between CPN and PMMA during the process of vertebral augmentation. Open-cell rigid foam model (Sawbones#1522-507) was used to create a simulated leakage model for the evaluation of the leakage characteristics of CPN and PMMA with different viscosities. The augmentation effects of CPN and PMMA were evaluated in human cadaveric and decalcified sheep vertebral models and then compared to the results from solid rigid foam model (Sawbones#1522-23). The dispersion abilities of CPN and PMMA were evaluated via three methods as follows. The dispersion volume and dispersion ratio were calculated by three-dimensional reconstruction using human vertebral body CT scans; the ratio of cement area to injection volume was calculated from three-dimensional sections of micro-CT scans of a sheep vertebra; and the micro-CT images of cement dispersion in open-cell rigid foam model (Sawbones#1522-507) were compared between CPN and PMMA. This study was funded by the National Natural Science Foundation of China (No. 81622032, 190,000 dollars and No. 51672184, 90,600 dollars), Principal Project of Natural Science Research of Jiangsu Higher Education Institutions (No. 17KJA180011, 22,000 dollars), and Jiangsu Innovation and Entrepreneurship Program (146,000 dollars).

RESULTS

There was no significant difference in vertebral height between CPN and PMMA during PKP augmentation and both cements restored the vertebral height after augmentation. In PKP augmentation experiment, posterior wall cement leakage occurred in 75% of human vertebrae augmented with PMMA; however, no leakage occurred in human vertebrae augmented with CPN. Anterior leakage occurred in all vertebrae augmented by PMMA, while in only 75% of vertebra augmented by CPN. Furthermore, CPN and PMMA had completely different leakage patterns in the simulated rigid foam model whether administered at the same injection speed or under the same injection force, suggesting that CPN has anti-leakage characteristics. The augmentation in human cadaveric vertebrae was lower with CPN compared to PMMA (1,668±816 N vs. 2,212±813 N, p=.459, respectively), but this difference was not significant. The augmentation force in sheep vertebral bodies reached 1,393±433 N when augmented with PMMA, but 1,108±284 N when augmented with CPN. The dispersion of CPN was better, and the dispersion volume and ratio were greater, with CPN than with PMMA. Imaging of the open-cell rigid foam model showed completely different dispersion modes for CPN and PMMA. After injection, the PMMA cement formed a contracted clump in the open-cell rigid foam model. However, the CPN cement extended many antennae outward, appearing to spread to the surrounding area. The surface areas of the CPN cement blocks with different liquid-to-solid ratios were significantly larger than the surface area of the PMMA cement in the open-cell rigid foam model (p<.05).

CONCLUSIONS

CPN has anti-leakage properties, which might be related to its high viscosity and viscoplasticity. CPN had a slightly lower augmentation force than PMMA when used in cadaveric vertebrae, decalcified sheep vertebrae, and in the standard rigid foam model. However, CPN diffused more easily into cancellous bone than did PMMA and encapsulated bone tissue during the dispersion process. The excellent dispersion of CPN generated better interdigitation with cancellous bone, which may be why the augmentation effect of CPN is similar to that of PMMA.

CLINICAL SIGNIFICANCE

Biodegradable CPN is a potential alternative to PMMA cement in PKP surgery, in which CPN is likely to reduce the cement leakage during the surgery and avoid the post-surgery complications caused by excessive strengths and nondegradability of PMMA cement.

Enhancing percutaneous pedicle screw fixation with hydroxyapatite granules: A biomechanical study using an osteoporotic bone model

Introduction

Percutaneous pedicle screw (PPS) can provide internal fixation of the thoracolumbar spine through a minimally invasive surgical procedure. PPS fixation has been widely used to treat various spinal diseases. Rigid fixation of PPS is essential for managing osteoporotic spine in order to prevent the risks of screw loosening and implant failure. We recently developed a novel augmentation method using hydroxyapatite (HA) granules for PPS fixation. The aim of this study was to evaluate the strength and stiffness of PPS fixation augmented with HA granules using an osteoporotic bone model.

Methods

Screws were inserted into uniform synthetic bone (sawbones) with and without augmentation. The uniaxial pullout strength and insertion torque of the screws were evaluated. In addition, each screw underwent cyclic toggling under incrementally increasing physiological loads until 2 mm of screwhead displacement occurred. The maximal pullout strength (N), maximal insertion torque (N·cm), number of toggle cycles and maximal load (N) required to achieve 2-mm screwhead displacement were compared between the screws with and without augmentation.

Results

The maximal pullout strength was significantly stronger for screws with augmentation than for those without augmentation (302 ± 19 N vs. 254 ± 17 N, p < 0.05). In addition, the maximal insertion torque was significantly increased in screws with augmentation compared to those without augmentation (48 ± 4 N·cm vs. 26 ± 5 N·cm, p < 0.05). Furthermore, the number of toggle cycles and the maximal load required to reach 2 mm of displacement were significantly greater in screws with augmentation than in those without augmentation (106 ± 9 vs. 52 ± 10 cycles; 152 ± 4 N vs. 124 ± 5 N, p < 0.05).

Conclusions

Augmentation using HA granules significantly enhanced the rigidity of PPS fixation in the osteoporotic bone model. The present study suggested that novel augmentation with HA granules may be a useful technique for PPS fixation in patients with osteoporotic spine.

Percutaneous Vertebral Body Augmentations: The State of Art

Osteoporotic compression fractures of the vertebral body can result in pain and long-term morbidity, including spinal deformity, with increased risk of mortality resulting from associated complications. Conservative management includes opioids and other analgesics, bed rest, and a back brace. For patients with severe and disabling pain, vertebral augmentation (vertebroplasty and kyphoplasty) is often considered, with these procedures endorsed by multiple professional societies, and provides immediate structural support, and stabilizes and reinforces the weakened bone structure. The purpose of this article is to review the vertebral biomechanics, indications and contraindications, and techniques of performing successful vertebral augmentation.

Polymerization kinetics stability, volumetric changes, apatite precipitation, strontium release and fatigue of novel bone composites for vertebroplasty

PURPOSE

The aim was to determine effects of diluent monomer and monocalcium phosphate monohydrate (MCPM) on polymerization kinetics and volumetric stability, apatite precipitation, strontium release and fatigue of novel dual-paste composites for vertebroplasty.

MATERIALS AND METHODS

Polypropylene (PPGDMA) or triethylene (TEGDMA) glycol dimethacrylates (25 wt%) diluents were combined with urethane dimethacrylate (70 wt%) and hydroxyethyl methacrylate (5 wt%). 70 wt% filler containing glass particles, glass fibers (20 wt%) and polylysine (5 wt%) was added. Benzoyl peroxide and MCPM (10 or 20 wt%) or N-tolyglycine glycidyl methacrylate and tristrontium phosphate (15 wt%) were included to give initiator or activator pastes. Commercial PMMA (Simplex) and bone composite (Cortoss) were used for comparison. ATR-FTIR was used to determine thermal activated polymerization kinetics of initiator pastes at 50-80°C. Paste stability, following storage at 4-37°C, was assessed visually or through mixed paste polymerization kinetics at 25°C. Polymerization shrinkage and heat generation were calculated from final monomer conversions. Subsequent expansion and surface apatite precipitation in simulated body fluid (SBF) were assessed gravimetrically and via SEM. Strontium release into water was assessed using ICP-MS. Biaxial flexural strength (BFS) and fatigue properties were determined at 37°C after 4 weeks in SBF.

RESULTS

Polymerization profiles all exhibited an inhibition time before polymerization as predicted by free radical polymerization mechanisms. Initiator paste inhibition times and maximum reaction rates were described well by Arrhenius plots. Plot extrapolation, however, underestimated lower temperature paste stability. Replacement of TEGDMA by PPGDMA, enhanced paste stability, final monomer conversion, water-sorption induced expansion and strontium release but reduced polymerization shrinkage and heat generation. Increasing MCPM level enhanced volume expansion, surface apatite precipitation and strontium release. Although the experimental composite flexural strengths were lower compared to those of commercially available Simplex, the extrapolated low load fatigue lives of all materials were comparable.

CONCLUSIONS

Increased inhibition times at high temperature give longer predicted shelf-life whilst stability of mixed paste inhibition times is important for consistent clinical application. Increased volumetric stability, strontium release and apatite formation should encourage bone integration. Replacing TEGDMA by PPGDMA and increasing MCPM could therefore increase suitability of the above novel bone composites for vertebroplasty. Long fatigue lives of the composites may also ensure long-term durability of the materials.

Distribution Pattern Making Sense: Patients Achieve Rapider Pain Relief with Confluent Rather Than Separated Bilateral Cement in Percutaneous Kyphoplasty for Osteoporotic Vertebral Compression Fractures

BACKGROUND

It has been reported the distribution of bone cement in percutaneous kyphoplasty (PKP) has an impact on the curative effect. No studies have compared between confluent and separated cement pattern of bilateral bone cement in PKP for patients with osteoporotic vertebral compression fractures.

METHODS

Between 2010 and 2016, 1341 patients were enrolled and divided into 2 groups. Group A (n = 723), bilateral cement was confluent; Group B (n = 618), bilateral cement was separated. The visual analogue scale (VAS), Oswestry Disability Index (ODI), anterior vertebral height (AVH), and local kyphotic angle (LKA) were obtained preoperatively, 2 days after surgery, and at the final follow-up to assess the functional and radiographic efficacy of the surgery.

RESULTS

The VAS, ODI, AVH, and LKA 2 days after operation and at the final follow-up were significantly improved compared with the preoperative for both groups (P < 0.05). There existed no significant difference between groups at various time point in ODI, AVH, and LKA (P > 0.05). Group A showed better VAS than group B 2 days after surgery (1.91 ± 0.98 vs. 2.35 ± 0.78, P < 0.001), also with better pre-postoperative VAS change (6.23 ± 0.76 vs. 5.75 ± 1.02, P < 0.001). Multiple linear regression for pain relief degree revealed group A (P < 0.001), older age (P < 0.001), and more cement volume (P < 0.001) contribute to rapid improvement of back pain. The cement leakage rate was 3.7% in group A and 2.9% in group B, with no significant difference (P = 0.405).

CONCLUSIONS

Patients achieved rapider pain relief with confluent rather than separated bilateral bone cement pattern in PKP for osteoporotic vertebral compression fracture.

Vertebral Fragility Fractures (VFF)-Who, when and how to operate

Vertebral Fragility Fractures (VFF) are common and lead to pain, long term disability and increased mortality. Most patients will have mild to moderate pain symptoms and can be managed conservatively. However, patients with severe pain who have minimal or no pain relief with potent analgesia, or who only achieve adequate pain relief with high doses of morphine based analgesia which results in significant adverse events, should be considered for vertebral augmentation. Ideally, for vertebral augmentation, patients should present within four months of the fracture (onset of acute pain) and have at least 3 weeks of failure of conservative treatment although early intervention may be more appropriate for hospitalised patients, who tend to be older, more frail and likely to be less tolerant to the adverse effects of conservative treatment. The Cardiovascular and Interventional Radiological Society of Europe (CIRSE) recommends Percutaneous Vertebroplasty as the first line surgical augmentation technique for VFF in older people, which has been shown to improve pain symptoms, allow early restoration of functional mobility and may reduce the risk of further vertebral collapse. CIRSE recommends percutaneous Balloon Kyphoplasty as second line treatment in VFF, although the optimal indication is for acute traumatic vertebral fractures (less than 7-10 days) in younger people. Assessment and treatment of underlying osteoporosis is important to reduce the risk of further fractures in older people with VFF.

Percutaneous osteoplasty for extraspinal metastases

As an extension of percutaneous vertebroplasty (PVP), percutaneous osteoplasty (POP) refers broadly to percutaneous bone cement injected into various parts of the body and narrowly to cement injected into extraspinal bone lesions. POP mainly includes such surgeries as percutaneous sacroplasty, percutaneous acetabuloplasty, percutaneous femoral osteoplasty, and percutaneous iliac osteoplasty (Figure 1). Currently, POP is a positive and an effective treatment for extraspinal bone lesions in that it can rapidly relieve pain, effectively prevent pathological fractures, and partially inactivate tumors, with few complications. The aim of this review is to detail the POP techniques and report their safety and efficacy in the treatment of extraspinal metastases.

Percutaneous upper extremity fracture fixation using a novel glass-based adhesive

Objective

To develop a surgical technique for percutaneous upper extremity fracture fixation using a novel glass-based adhesive.

Methods

Three intact upper extremity cadaveric specimens with undisturbed soft tissues were obtained. Two were used to model a wrist fracture, and the third to model a proximal humerus fracture. Fractures were produced using a small osteotome in a percutaneous fashion. Banna Bone Adhesive (BBA) was delivered to the fracture site percutaneously using a 16 gauge needle under bi-planar fluoroscopic guidance. After setting of the adhesive, the specimens were dissected to qualitatively assess BBA delivery and placement.

Results

The adhesive could readily be delivered through the 16 gauge needle with an appropriate amount of pressure applied to the syringe. Using the fluoroscope, the adhesive could be seen to flow into the fracture site with minimal extravagation into the surrounding soft tissues. Successful bonding of the fracture fragments was observed.

Conclusions

Percutaneous delivery of BBA into a fracture of the distal radius and proximal humerus may be a feasible fracture fixation technique. Biomechanical testing and animal model testing are required to further develop this procedure.

Adjustable Polyurethane Foam as Filling Material for a Novel Spondyloplasty: Biomechanics and Biocompatibility

OBJECTIVE

To investigate the biomechanics and biocompatibility of polyurethane (PU) foam with adjustable stiffness as a filling material for a novel spondyloplasty that is designed to reduce the risk of postoperative adjacent level fractures.

METHODS

Sixty individual porcine lumbar vertebrae were randomly split into 4 groups: A, B, C, and D. Group A served as unmodified vertebral body controls. Groups B, C, and D consisted of hollowed vertebral bodies. Vertebrae of groups C and D were filled with adjustable PU foams of different stiffness. The compressive strength and stiffness of vertebrae from groups A-D were recorded and analyzed. 3T3 mouse fibroblasts were cultured with preformed PU foams for 4 days to test biocompatibility.

RESULTS

The strength and stiffness of the hollowed groups were lower than in group A. However, the differences were not statistically significant between group A and group C (P > 0.05), and were obviously different between group A and group B or group D (P < 0.01 and <0.05, respectively). Moreover, the strength and stiffness after filling foams in group C or group D were significantly greater than in group B (P < 0.01 and <0.05, respectively). Live/dead staining of 3T3 cells confirmed the biocompatibility of the PU foam.

CONCLUSIONS

The new PU foam shows adaptability regarding its stiffness and excellent cytocompatibility in vitro. The results support the clinical translation of the new PU foams as augmentation material in the development of a novel spondyloplasty.

Biomechanical effects of different vertebral heights after augmentation of osteoporotic vertebral compression fracture: a three-dimensional finite element analysis

Background

Clinical results have shown that different vertebral heights have been restored post-augmentation of osteoporotic vertebral compression fractures (OVCFs) and the treatment results are consistent. However, no significant results regarding biomechanical effects post-augmentation have been found with different types of vertebral deformity or vertebral heights by biomechanical analysis. Therefore, the present study aimed to investigate the biomechanical effects between different vertebral heights of OVCFs before and after augmentation using three-dimensional finite element analysis.

Methods

Four patients with OVCFs of T12 underwent computed tomography (CT) of the T11-L1 levels. The CT images were reconstructed as simulated three-dimensional finite-element models of the T11-L1 levels (before and after the T12 vertebra was augmented with cement). Four different kinds of vertebral height models included Genant semi-quantitative grades 0, 1, 2, and 3, which simulated unilateral augmentation. These models were assumed to represent vertical compression and flexion, left flexion, and right flexion loads, and the von Mises stresses of the T12 vertebral body were assessed under different vertebral heights before and after bone cement augmentation.

Results

Data showed that the von Mises stresses significantly increased under four loads of OVCFs of the T12 vertebral body before the operation from grade 0 to grade 3 vertebral heights. The maximum stress of grade 3 vertebral height pre-augmentation was produced at approximately 200%, and at more than 200% for grade 0. The von Mises stresses were significantly different between different vertebral heights preoperatively. The von Mises stresses of the T12 vertebral body significantly decreased in four different loads and at different vertebral body heights (grades 0–3) after augmentation. There was no significant difference between the von Mises stresses of grade 0, 1, and 3 vertebral heights postoperatively. The von Mises stress significantly decreased between pre-augmentation and post-augmentation in T12 OVCF models of grade 0–3 vertebral heights.

Conclusion

Vertebral augmentation can sufficiently reduce von Mises stresses at different heights of OVCFs of the vertebral body, although this technique does not completely restore vertebral height to the anatomical criteria.

Bone substitutes: a review of their characteristics, clinical use, and perspectives for large bone defects management

Bone replacement might have been practiced for centuries with various materials of natural origin, but had rarely met success until the late 19th century. Nowadays, many different bone substitutes can be used. They can be either derived from biological products such as demineralized bone matrix, platelet-rich plasma, hydroxyapatite, adjunction of growth factors (like bone morphogenetic protein) or synthetic such as calcium sulfate, tri-calcium phosphate ceramics, bioactive glasses, or polymer-based substitutes. All these substitutes are not suitable for every clinical use, and they have to be chosen selectively depending on their purpose. Thus, this review aims to highlight the principal characteristics of the most commonly used bone substitutes and to give some directions concerning their clinical use, as spine fusion, open-wedge tibial osteotomy, long bone fracture, oral and maxillofacial surgery, or periodontal treatments. However, the main limitations to bone substitutes use remain the management of large defects and the lack of vascularization in their central part, which is likely to appear following their utilization. In the field of bone tissue engineering, developing porous synthetic substitutes able to support a faster and a wider vascularization within their structure seems to be a promising way of research.

Prophylactic vertebroplasty procedure applied with a resorbable bone cement can decrease the fracture risk of sandwich vertebrae: long-term evaluation of clinical outcomes

A sandwich vertebra is formed after multiple osteoporotic vertebral fractures treated by percutaneous vertebroplasty, which has a risk of developing new fractures. The purpose of our study was to (i) investigate the occurrence of new fractures in sandwich vertebra after cement augmentation procedures and to (ii) evaluate the clinical outcomes after prophylactic vertebral reinforcement applied with resorbable bone cement.

From June 2011 to 2014, we analysed 55 patients with at least one sandwich vertebrae and treated with percutaneous vertebroplasty. Eighteen patients were treated by prophylactic vertebroplasty with a resorbable bone cement to strengthen the sandwich vertebrae as the prevention group. The others were the non-prevention group. All patients were examined by spinal radiographs within 1 day, 6 months, 12 months, 24 months and thereafter.

The incidence of sandwich vertebra is 8.25% (55/667) in our study. Most sandwich vertebrae (69.01%, 49/71) are distributed in the thoracic–lumbar junction. There are 24 sandwich vertebrae (18 patients) and 47 sandwich vertebrae (37 patients) in either prevention group or non-prevention group, respectively. No significant difference is found between age, sex, body mass index, bone mineral density, cement disk leakage, sandwich vertebrae distribution or Cobb angle in the two groups. In the follow-up, 8 out of 37 (21.6%) patients (with eight sandwich vertebrae) developed new fractures in non-prevention’ group, whereas no new fractures were detected in the prevention group. Neither Cobb angle nor vertebral compression rate showed significant change in the prevention group during the follow-up. However, in the non-prevention group, we found that Cobb angle increased and vertebral height lost significantly (P < 0.05).

Prophylactic vertebroplasty procedure applied with resorbable bone cement could decrease the rate of new fractures of sandwich vertebrae.

Depression of the Thoracolumbar Posterior Vertebral Body on the Estimation of Cement Leakage in Vertebroplasty and Kyphoplasty Operations

Background:

The cross-section of thoracolumbar vertebral body is kidney-shaped with depressed posterior boundary. The anterior wall of the vertebral canal is separated from the posterior wall of the vertebral body on the lateral X-ray image. This study was designed to determine the sagittal distance between the anterior border of the vertebral canal and the posterior border of the vertebral body (DBCV) and to analyze the potential role of DBCV in the estimation of cement leakage during percutaneous vertebroplasty (PVP) or percutaneous kyphoplasty (PKP).

Methods:

We retrospectively recruited 233 patients who had osteoporotic vertebral compression fractures and were treated with PVP or PKP. Computed tomography images of T11–L2 normal vertebrae were measured to obtain DBCV. The distance from cement to the posterior wall of the vertebral body (DCPW) of thoracolumbar vertebrae was measured from C-arm images. The selected vertebrae were divided into two groups according to DCPW, with the fracture levels, fracture grades and leakage rates of the two groups compared. A relative operating characteristic (ROC) curve was applied to determine whether the DCPW difference can be used to estimate the degree of cement leakage. The data were processed by statistical software SPSS version 21.0 using independent sample t-test and Chi-square tests.

Results:

The maximum DBCV was 6.40 mm and the average DBCV was 3.74 ± 0.95 mm. DBCV appeared to be longer in males than in females, but the difference was not statistically significant. The average DCPW of type-B leakage vertebrae (2.59 ± 1.20 mm) was shorter than that of other vertebrae (7.83 ± 2.38 mm, P < 0.001). The leakage rate of group DCPW ≤6.40 mm was lower than that of group DCPW >6.40 mm for type-C and type-S, but much higher for type-B. ROC curve revealed that DCPW only has a predictive value for type-B leakage (area under the curve: 0.98, 95% confidence interval: 0.95–0.99, P < 0.001), and when the cut-off value was 4.05 mm, the diagnostic sensitivity and the specificity were 94.87% and 93.02%, respectively.

Conclusions:

Depression of the thoracolumbar posterior vertebral body may be informative for the estimation of cement location on C-arm images. To reduce type-B leakage, DCPW should be made longer than DBCV on C-arm images for safety during PVP or PKP.

Decreased extrusion of calcium phosphate cement versus high viscosity PMMA cement into spongious bone marrow-an ex vivo and in vivo study in sheep vertebrae

BACKGROUND CONTEXT

Vertebroplasty or kyphoplasty of osteoporotic vertebral fractures bears the risk of pulmonary cement embolism (3.5%-23%) caused by leakage of commonly applied acrylic polymethylmethacrylate (PMMA) cement to spongious bone marrow or outside of the vertebrae. Ultraviscous cement and specific augmentation systems have been developed to reduce such adverse effects. Rapidly setting, resorbable, physiological calcium phosphate cement (CPC) may also represent a suitable alternative.

PURPOSE

This study aimed to compare the intravertebral extrusion of CPC and PMMA cement in an ex vivo and in vivo study in sheep.

STUDY DESIGN/SETTING

A prospective experimental animal study was carried out.

METHODS

Defects (diameter 5 mm; 15 mm depth) were created by a ventrolateral percutaneous approach in lumbar vertebrae of female Merino sheep (2-4 years) either ex vivo (n=17) or in vivo (n=6), and injected with: (1) CPC (L3); (2) CPC reinforced with 10% poly(l-lactide-co-glycolide) (PLGA) fibers (L4); or (3) PMMA cement (L5; Kyphon HV-R). Controls were untouched (L1) or empty defects (L2). The effects of the cement injections were assessed in vivo by blood gas analysis and ex vivo by computed tomography (CT), micro-CT (voxel size: 67 µm), histology, and biomechanical testing.

RESULTS

Following ex vivo injection, micro-CT documented significantly increased extrusion of PMMA cement in comparison to CPC (+/- fibers) starting at a distance of 1 mm from the edge of the defect (confirmed by histology); this was also demonstrated by micro-CT following in vivo cement injection. In addition, blood gas analysis showed consistently significantly lower values for the fraction of oxygenized hemoglobin/total hemoglobin (FO₂Hb) in the arterial blood until 25 minutes following injection of the PMMA cement (p ≤ .05 vs. CPC; 7, 15 minutes). Biomechanical testing following ex vivo injection showed significantly lower compressive strength and Young modulus than untouched controls for the empty defect (40% and 34% reduction, respectively) and all three cement-injected defects (21%-27% and 29%-32% reduction, respectively), without significant differences among the cements.

CONCLUSIONS

Because of comparable compressive strength, but significantly lower cement extrusion into spongious bone marrow than PMMA cement, physiological CPC (+/- PLGA fibers) may represent an attractive alternative to PMMA for vertebroplasty or kyphoplasty of osteoporotic vertebral fractures to reduce the frequency or severity of adverse effects.

Biocompatibility of calcium phosphate bone cement with optimised mechanical properties: an in vivo study

This work establishes the in vivo performance of modified calcium phosphate bone cements for vertebroplasty of spinal fractures using a lapine model. A non-modified calcium phosphate bone cement and collagen-calcium phosphate bone cements composites with enhanced mechanical properties, utilising either bovine collagen or collagen from a marine sponge, were compared to a commercial poly(methyl methacrylate) cement. Conical cement samples (8 mm height × 4 mm base diameter) were press-fit into distal femoral condyle defects in New Zealand White rabbits and assessed after 5 and 10 weeks. Bone apposition and tartrate-resistant acid phosphatase activity around cements were assessed. All implants were well tolerated, but bone apposition was higher on calcium phosphate bone cements than on poly(methyl methacrylate) cement. Incorporation of collagen showed no evidence of inflammatory or immune reactions. Presence of positive tartrate-resistant acid phosphatase staining within cracks formed in calcium phosphate bone cements suggested active osteoclasts were present within the implants and were actively remodelling within the cements. Bone growth was also observed within these cracks. These findings confirm the biological advantages of calcium phosphate bone cements over poly(methyl methacrylate) and, coupled with previous work on enhancement of mechanical properties through collagen incorporation, suggest collagen-calcium phosphate bone cement composite may offer an alternative to calcium phosphate bone cements in applications where low setting times and higher mechanical stability are important.

A PRELIMINARY IN VITRO BIOMECHANICAL EVALUATION OF PROPHYLACTIC CEMENT AUGMENTATION OF THE THORACOLUMBAR VERTEBRAE

In this paper, the biomechanical effectiveness of prophylactic augmentation in preventing fracture was investigated. In vitro biomechanical tests were performed to assess which factors make prophylactic augmentation effective/ineffective in reducing fracture risk. Nondestructive and destructive in vitro tests were performed on isolated osteoporotic vertebrae. Five sets of three-adjacent-vertebrae were tested. The central vertebra of each triplet was tested in the natural condition (control) non-destructively (axial-compression, torsion) and destructively (axial-compression). The two adjacent vertebrae were first tested nondestructively (axial-compression, torsion) pre-augmentation; prophylactic augmentation (uni- or bi-pedicular access) was then performed delivering 5.04[Formula: see text]mL to 8.44[Formula: see text]mL of acrylic cement by means of a customized device; quality of augmentation was CT-assessed; the augmented vertebrae were re-tested nondestructively (axial-compression, torsion), and eventually loaded to failure (axial-compression). Vertebral stiffness was correlated with the first-failure, but not with ultimate failure. The force and work to ultimate failure in prophylactic-augmented vertebrae was consistently larger than in the controls. However, in some cases the first-failure force and work in the augmented vertebrae were lower than for the controls. To investigate the reasons for such unpredictable results, the correlation with augmentation quality was analyzed. Some augmentation parameters seemed more correlated with mechanical outcome (statistically not-significant due to the limited sample size): uni-pedicular access resulted in a single cement mass, which tended to increase the force and work to first- and ultimate failure. The specimens with the highest strength and toughness also had: at least 25% cement filling, cement mass shifted anteriorly, and cement-endplate contact. These findings seem to confirm that prophylactic augmentation may aid reducing the risk of fracture. However, inadequate augmentation may have detrimental consequences. This study suggests that, to improve the strength of the augmented vertebrae, more attention should be dedicated to the quality of augmentation in terms of amount and position of the injected cement.

[Vertebroplasty--state of the art]

BACKGROUND

Percutaneous vertebroplasty (PVP) using PMMA (polymethyl methacrylate) was first described in 1987 by Gallibert and Deramond for the treatment of vertebral body instability in patients with aggressive forms of vertebral hemangioma. Other types of painful osteolytic bone lesions, such as osteoporotic vertebral fractures and vertebral metastasis are in the meantime more commonly treated using this method.

METHODICAL INNOVATIONS

Within the last few years, this technique has become widely accepted and it is proposed for osteolytic bone lesions in areas that are more difficult to approach surgically, e.g., the pelvis and sacrum.

EFFICACY

Rapid pain relief and resulting stability have conferred an important role upon osteoplasty especially in palliative tumor-treatment for patients with shortened expected life spans. In addition, combined treatment of painful osteolytic metastases with image-guided thermoablation and percutaneous cement injection has been shown to be a safe palliative modality in the therapy of nonresectable tumors.

The Biomechanical Properties of Pedicle Screw Fixation Combined With Trajectory Bone Cement Augmentation in Osteoporotic Vertebrae

STUDY DESIGN

The biomechanics of pedicle screw fixation combined with trajectory cement augmentation with various filling volumes were measured by pull-out, periodic antibending, and compression fatigue tests.

OBJECTIVE

To investigate the biomechanical properties of the pedicle screw fixation combined with trajectory bone cement (polymethylmethacrylate) augmentation in osteoporotic vertebrae and to explore the optimum filling volume of the bone cement.

SUMMARY OF BACKGROUND DATA

Pedicle screw fixation is considered to be the most effective posterior fixation method. The decrease of the bone mineral density apparently increases the fixation failure risk caused by screw loosening and displacement. Trajectory bone cement augmentation has been confirmed to be an effective method to increase the bone intensity and could markedly increase the stability of the fixation interface.

METHODS

Sixteen elderly cadaveric 1-5 lumbar vertebral specimens were diagnosed with osteoporosis. The left and right vertebral pedicles were alternatively randomized for treatment in all groups, with the contralateral pedicles as control. The study groups included: group A (pedicle screw fixation with full trajectory bone cement augmentation), group B (75% filling), group C (50% filling), and group D (25% filling). Finally, the bone cement leakage and dispersion were assessed and the mechanical testing was conducted.

RESULTS

The bone cement was well dispersed around the pedicle screw. The augmented bone intensity, pull-out strength, periodic loading times, and compression fatigue performance were markedly higher than those of the control groups. With the increase in trajectory bone cement, the leakage was also increased (P<0.05). The pull-out strength of the pedicle screw was increased with an increase in bone mineral density and trajectory bone cement. It peaked at 75% filling, with the largest power consumption.

CONCLUSIONS

The optimal filling volume of the bone cement was 75% of the trajectory volume (about 1.03 mL). The use of excessive bone cement did not increase the fixation intensity but increased the risk of leakage.

Cement Calcaneoplasty: An Innovative Method for Treating Nonunion in Calcaneal Insufficiency Fracture

Insufficiency type stress fractures are common in older patients with osteoporosis. Persistent pain after nonunion of these fractures can be disabling, with the management options often limited. We aimed to assess the suitability of fluoroscopic-guided injection of bone cement into a persistently symptomatic nonuniting calcaneal insufficiency fracture. To the best of our knowledge, this technique has not previously been described in the published data. After local subcutaneous anesthesia, the midpoint of the fracture site was accessed by trocar insertion under radiographic guidance, and bone cement was injected directly into the site. A preprocedure visual analog scale pain score of 90 of 100 was recorded. This had improved to 0 of 100 at the 12-month follow-up point after the procedure. The aim of the present case report was to raise awareness of percutaneous calcaneoplasty, which we believe to be a safe and well-tolerated technique for the management of osteoporotic insufficiency fracture of the calcaneus. We propose that this technique be considered when conservative methods aimed at promoting fracture healing have failed.

Pullout performance comparison of pedicle screws based on cement application and design parameters

Pedicle screws are the main fixation devices for certain surgeries. Pedicle screw loosening is a common problem especially for osteoporotic incidents. Cannulated screws with cement augmentation are widely used for that kind of cases. Dual lead dual cored pedicle screw has already given promising pullout values without augmentation. This study concentrates on the usage of dual lead dual core with cement augmentation as an alternative to cannulated and standard pedicle screws with cement augmentation. Five groups (dual lead dual core, normal pedicle screw and cannulated pedicle screw with augmentation, normal pedicle screw, dual lead dual cored pedicle screw) were designed for this study. Healthy bovine vertebrae and synthetic polyurethane foams (grade 20) were used as embedding test medium. Test samples were prepared in accordance with surgical guidelines and ASTM F543 standard testing protocols. Pullout tests were conducted with Instron 3300 testing frame. Load versus displacement values were recorded and maximum pullout loads were stated. The dual lead dual cored pedicle screw with poly-methyl methacrylate augmentation exhibited the highest pullout values, while dual lead dual cored pedicle screw demonstrated similar pullout strength as cannulated pedicle screw and normal pedicle screw with poly-methyl methacrylate augmentation. The dual lead dual cored pedicle screw with poly-methyl methacrylate augmentation can be used for osteoporotic and/or severe osteoporotic patients according to its promising results on animal cadaver and synthetic foams.

Calcium phosphate scaffolds combined with bone morphogenetic proteins or mesenchymal stem cells in bone tissue engineering

Objective:

The purpose of this study was to review the current status of calcium phosphate (CaP) scaffolds combined with bone morphogenetic proteins (BMPs) or mesenchymal stem cells (MSCs) in the field of bone tissue engineering (BTE).

Date Sources:

Data cited in this review were obtained primarily from PubMed and Medline in publications from 1979 to 2014, with highly regarded older publications also included. The terms BTE, CaP, BMPs, and MSC were used for the literature search.

Study Selection:

Reviews focused on relevant aspects and original articles reporting in vitro and/or in vivo results concerning the efficiency of CaP/BMPs or CaP/MSCs composites were retrieved, reviewed, analyzed, and summarized.

Results:

An ideal BTE product contains three elements: Scaffold, growth factors, and stem cells. CaP-based scaffolds are popular because of their outstanding biocompatibility, bioactivity, and osteoconductivity. However, they lack stiffness and osteoinductivity. To solve this problem, composite scaffolds of CaP with BMPs have been developed. New bone formation by CaP/BMP composites can reach levels similar to those of autografts. CaP scaffolds are compatible with MSCs and CaP/MSC composites exhibit excellent osteogenesis and stiffness. In addition, a CaP/MSC/BMP scaffold can repair bone defects more effectively than an autograft.

Conclusions:

Novel BTE products possess remarkable osteoconduction and osteoinduction capacities, and exhibit balanced degradation with osteogenesis. Further work should yield safe, viable, and efficient materials for the repair of bone lesions.

Electrospun Nanofibrous P(DLLA-CL) Balloons as Calcium Phosphate Cement Filled Containers for Bone Repair: in Vitro and in Vivo Studies

The spinal surgeon community has expressed significant interest in applying calcium phosphate cement (CPC) for the treatment of vertebral compression fractures (VCFs) and minimizing its disadvantages, such as its water-induced collapsibility and poor mechanical properties, limiting its clinical use. In this work, novel biodegradable electrospun nanofibrous poly(d,l-lactic acid-ϵ-caprolactone) balloons (ENPBs) were prepared, and the separation, pressure, degradation, and new bone formation behaviors of the ENPBs when used as CPC-filled containers in vitro and in vivo were systematically analyzed and compared. CPC could be separated from surrounding bone tissues by ENPBs in vitro and in vivo. ENPB-CPCs (ENPBs serving as CPC-filled containers) exerted pressure on the surrounding bone microenvironment, which was enough to crush trabecular bone. Compared with the CPC implantation, ENPB-CPCs delayed the degradation of CPC (i.e., its water-induced collapsilibity). Finally, possible mechanisms behind the in vivo effects caused by ENPB-CPCs implanted into rabbit thighbones and pig vertebrae were proposed. This work suggests that ENPBs can be potentially applied as CPC-filled containers in vivo and provides an experimental basis for the clinical application of ENPBs for the treatment of VCFs. In addition, this work will be of benefit to the development of polymer-based medical implants in the future.

Bone Graft Substitute Provides Metaphyseal Fixation for a Stemless Humeral Implant

Stemless humeral fixation has become an alternative to traditional total shoulder arthroplasty, but metaphyseal fixation may be compromised by the quality of the trabecular bone that diminishes with age and disease, and augmentation of the fixation may be desirable. The authors hypothesized that a bone graft substitute (BGS) could achieve initial fixation comparable to polymethylmethacrylate (PMMA) bone cement. Fifteen fresh-frozen human male humerii were randomly implanted using a stemless humeral prosthesis, and metaphyseal fixation was augmented with either high-viscosity PMMA bone cement (PMMA group) or a magnesium-based injectable BGS (OsteoCrete; Bone Solutions Inc, Dallas, Texas) (OC group). Both groups were compared with a control group with no augmentation. Initial stiffness, failure load, failure displacement, failure cycle, and total work were compared among groups. The PMMA and OC groups showed markedly higher failure loads, failure displacements, and failure cycles than the control group (P<.01). There were no statistically significant differences in initial stiffness, failure load, failure displacement, failure cycle, or total work between the PMMA and OC groups. The biomechanical properties of magnesium-based BGS fixation compared favorably with PMMA bone cement in the fixation of stemless humeral prostheses and may provide sufficient initial fixation for this clinical application. Future work will investigate the long-term remodeling characteristics and bone quality at the prosthetic-bone interface in an in vivo model to evaluate the clinical efficacy of this approach.

The biomechanics of pedicle screw augmentation with cement

BACKGROUND CONTEXT

A persistent challenge in spine surgery is improving screw fixation in patients with poor bone quality. Augmenting pedicle screw fixation with cement appears to be a promising approach.

PURPOSE

The purpose of this study was to survey the literature and assess the previous biomechanical studies on pedicle screw augmentation with cement to provide in-depth discussions of the biomechanical benefits of multiple parameters in screw augmentation.

STUDY DESIGN/SETTING

This is a systematic literature review.

METHODS

A search of Medline was performed, combining search terms of pedicle screw, augmentation, vertebroplasty, kyphoplasty, polymethylmethacrylate, calcium phosphate, or calcium sulfate. The retrieved articles and their references were reviewed, and articles dealing with biomechanical testing were included in this article.

RESULTS

Polymethylmethacrylate is an effective material for enhancing pedicle screw fixation in both osteoporosis and revision spine surgery models. Several other calcium ceramics also appear promising, although further work is needed in material development. Although fenestrated screw delivery appears to have some benefits, it results in similar screw fixation to prefilling the cement with a solid screw. Some differences in screw biomechanics were noted with varying cement volume and curing time, and some benefits from a kyphoplasty approach over a vertebroplasty approach have been noted. Additionally, in cadaveric models, cemented-augmented screws were able to be removed, albeit at higher extraction torques, without catastrophic damage to the vertebral body. However, there is a risk of cement extravasation leading to potentially neurological or cardiovascular complications with cement use. A major limitation of these reviewed studies is that biomechanical tests were generally performed at screw implantation or after a limited cyclic loading cycle; thus, the results may not be entirely clinically applicable. This is particularly true in the case of the bioactive calcium ceramics, as these biomechanical studies would not have measured the effects of osseointegration.

CONCLUSIONS

Polymethylmethacrylate and various calcium ceramics appear promising for the augmentation of pedicle screw fixation biomechanically in both osteoporosis and revision spine surgery models. Further translational studies should be performed, and the results summarized in this review will need to be correlated with the clinical outcomes.