Calcium-phosphate and polymethylmethacrylate cement in long-term outcome after kyphoplasty of painful osteoporotic vertebral fractures

Biodegradable poly(caprolactone fumarate) 3D printed scaffolds for segmental bone defects within the Masquelet technique

Segmental bone defects, often clinically treated with nondegradable poly(methylmethacrylate) (PMMA) in multistage surgeries, present a significant clinical challenge. Our study investigated the efficacy of 3D printed biodegradable polycaprolactone fumarate (PCLF)/PCL spacers in a one-stage surgical intervention for these defects, focusing on early bone regeneration influenced by spacer porosities. We compared nonporous PCLF/PCL and PMMA spacers, conventionally molded into cylinders, with porous PCLF/PCL spacers, 3D printed to structurally mimic segmental defects in rat femurs for a 4-week implantation study. Histological analysis, including tissue staining and immunohistochemistry with bone-specific antibodies, was conducted for histomorphometry evaluation. The PCLF/PCL spacers demonstrated compressive properties within 6 ± 0.5 MPa (strength) and 140 ± 15 MPa (modulus). Both porous PCLF/PCL and Nonporous PMMA formed collagen-rich membranes (PCLF/PCL: 92% ± 1.3%, PMMA: 86% ± 1.5%) similar to those induced in the Masquelet technique, indicating PCLF/PCL's potential for one-stage healing. Immunohistochemistry confirmed biomarkers for tissue regeneration, underscoring PCLF/PCL's regenerative capabilities. This research highlights PCLF/PCL scaffolds' ability to induce membrane formation in critical-sized segmental bone defects, supporting their use in one-stage surgery. Both solid and porous PCLF/PCL spacers showed adequate compressive properties, with the porous variants exhibiting BMP-2 expression and woven bone formation, akin to clinical standard PMMA. Notably, the early ossification of the membrane into the pores of porous scaffolds suggests potential for bone interlocking and regeneration, potentially eliminating the need for a second surgery required for PMMA spacers. The biocompatibility and biodegradability of PCLF/PCL make them promising alternatives for treating critical bone defects, especially in vulnerable patient groups.

Injectable and high-strength PLGA/CPC loaded ALN/MgO bone cement for bone regeneration by facilitating osteogenesis and inhibiting osteoclastogenesis in osteoporotic bone defects

Osteoporosis (OP) can result in slower bone regeneration than the normal condition due to the imbalance between osteogenesis and osteoclastogenesis, making osteoporotic bone defects healing a significant clinical challenge. Calcium phosphate cement (CPC) is a promising bone substitute material due to its good osteoinductive activity, however, the drawbacks such as fragility, slow degradation rate and incapability to control bone loss restrict its application in osteoporotic bone defects treatment. Currently, we developed the PLGA electrospun nanofiber sheets to carry alendronate (ALN) and magnesium oxide nanoparticle (nMgO) into CPC, therefore, to obtain a high-strength bone cement (C/AM-PL/C). The C/AM-PL/C bone cement had high mechanical strength, anti-washout ability, good injection performance and drug sustained release capacity. More importantly, the C/AM-PL/C cement promoted the osteogenic differentiation of bone marrow mesenchymal stem cells and neovascularization via the release of Mg2+ (from nMgO) and Ca2+ (during the degradation of CPC), and inhibited osteoclastogenesis via the release of ALN in vitro. Moreover, the injection of C/AM-PL/C cement significantly improved bone healing in an OP model with femur condyle defects in vivo. Altogether, the injectable C/AM-PL/C cement could facilitate osteoporotic bone regeneration, demonstrating its capacity as a promising candidate for treatment of osteoporotic bone defects.

Injectable, anti-collapse, adhesive, plastic and bioactive bone graft substitute promotes bone regeneration by moderating oxidative stress in osteoporotic bone defect

The treatment of osteoporotic bone defect remains a big clinical challenge because osteoporosis (OP) is associated with oxidative stress and high levels of reactive oxygen species (ROS), a condition detrimental for bone formation. Anti-oxidative nanomaterials such as selenium nanoparticles (SeNPs) have positive effect on osteogenesis owing to their pleiotropic pharmacological activity which can exert anti-oxidative stress functions to prevent bone loss and facilitate bone regeneration in OP. In the current study a strategy of one-pot method by introducing Poly (lactic acid-carbonate) (PDT) and β-Tricalcium Phosphate (β-TCP) with SeNPs, is developed to prepare an injectable, anti-collapse, shape-adaptive and adhesive bone graft substitute material (PDT-TCP-SE). The PDT-TCP-SE bone graft substitute exhibits sufficient adhesion in biological microenvironments and osteoinductive activity, angiogenic effect and anti-inflammatory as well as anti-oxidative effect in vitro and in vivo. Moreover, the PDT-TCP-SE can protect BMSCs from erastin-induced ferroptosis through the Sirt1/Nrf2/GPX4 antioxidant pathway, which, in together, demonstrated the bone graft substitute material as an emerging biomaterial with potential clinical application for the future treatment of osteoporotic bone defect. STATEMENT OF SIGNIFICANCE: Injectable, anti-collapse, adhesive, plastic and bioactive bone graft substitute was successfully synthesized. Incorporation of SeNPs with PDT into β-TCP regenerated new bone in-situ by moderating oxidative stress in osteoporotic bone defects area. The PDT-TCP-SE bone graft substitute reduced high ROS levels in osteoporotic bone defect microenvironment. The bone graft substitute could also moderate oxidative stress and inhibit ferroptosis via Sirt1/Nrf2/GPX4 pathway in vitro. Moreover, the PDT-TCP-SE bone graft substitute could alleviate the inflammatory environment and promote bone regeneration in osteoporotic bone defect in vivo. This biomaterial has the advantages of simple synthesis, biocompatibility, anti-collapse, injectable, and regulation of oxidative stress level, which has potential application value in bone tissue engineering.

A Toolbox of Bone Consolidation for the Interventional Radiologist

Bone consolidation is increasingly used in the treatment of both benign and malignant bone conditions. Percutaneous vertebroplasty, for example, has been shown to be useful in vertebral compression fractures in the VAPOUR trial which showed its superiority to placebo for pain reduction in the treatment of acute vertebral compressive fractures. Further tools have since been developed, such as kyphoplasty, spinal implants, and even developments in bone cements itself in attempt to improve outcome, such as chemotherapy-loaded cement or cement replacements such as radio-opaque silicon polymer. More importantly, bone fixation and its combination with cement have been increasingly performed to improve outcome. Interventional radiologists must first know the tools available, before they can best plan for their patients. This review article will focus on the tool box available for the modern interventional radiologist.

Traumatic Fracture Treatment: Calcium Phosphate Bone Substitute Case-Control Study in Humerus, Radius, Tibia Fractures-Assessing Efficacy and Recovery Outcomes

To date, insufficient investigation has been carried out on the biocompatibility of synthetic bioactive bone substitute materials after traumatically induced bone fractures in clinical conditions. This study encompasses the safety, resorption, healing process, and complications of surgical treatment. Our current hypothesis posits that calcium phosphate-based bone substitutes could improve bone healing. In this retrospective case-control study, over 290 patients who underwent surgical treatment for acute fractures were examined. Bone defects were augmented with calcium phosphate-based bone substitute material (CP) in comparison to with empty defect treatment (ED) between 2011 and 2018. A novel scoring system for fracture healing was introduced to assess bone healing in up to six radiological follow-up examinations. Furthermore, demographic data, concomitant diseases, and complications were subjected to analysis. Data analysis disclosed significantly fewer postoperative complications in the CP group relative to the ED group (p < 0.001). The CP group revealed decreased risks of experiencing complications (p < 0.001), arthrosis (p = 0.01), and neurological diseases (p < 0.001). The fracture edge, the fracture gap, and the articular surface were definably enhanced. Osteosynthesis and general bone density demonstrated similarity (p > 0.05). Subgroup analysis focusing on patients aged 64 years and older revealed a diminished complication incidence within the CP group (p = 0.025). Notably, the application of CP bone substitute materials showed discernible benefits in geriatric patients, evident by decreased rates of pseudarthrosis (p = 0.059). Intermediate follow-up evaluations disclosed marked enhancements in fracture gap, edge, and articular surface conditions through the utilization of CP-based substitutes (p < 0.05). In conclusion, calcium phosphate-based bone substitute materials assert their clinical integrity by demonstrating safety in clinical applications. They substantiate an accelerated early osseous healing trajectory while concurrently decreasing the severity of complications within the bone substitute cohort. In vivo advantages were demonstrated for CP bone graft substitutes.

Injectable nanofiber-reinforced bone cement with controlled biodegradability for minimally-invasive bone regeneration

Injectable materials show their special merits in regeneration of damaged/degenerated bones in minimally-invasive approach. Injectable calcium phosphate bone cement (CPC) has attracted broad attention for its bioactivity, as compared to non-degradable polymethyl methacrylate cement. However, its brittleness, poor anti-washout property and uncontrollable biodegradability are the main challenges to limit its further clinical application mainly because of its stone-like dense structure and fragile inorganic-salt weakness. Herein, we developed a kind of injectable CPC bone cement with porous structure and improved robustness by incorporating poly(lactide-co-glycolic acid) (PLGA) nanofiber into CPC, with carboxymethyl cellulose (CMC) to offer good injectability as well as anti-wash-out capacity. Furthermore, the introduction of PLGA and CMC also enabled a formation of initial porous structure in the cements, where PLGA nanofiber endowed the cement with a dynamically controllable biodegradability which provided room for cell movement and bone ingrowth. Interestingly, the reinforced biodegradable cement afforded a sustainable provision of Ca²⁺ bioactive components, together with its porous structure, to improve synergistically new bone formation and osteo-integration in vivo by using a rat model of femur condyle defect. Further study on regenerative mechanisms indicated that the good minimally-invasive bone regeneration may come from the synergistic enhanced osteogenic effect of calcium ion enrichment and the improved revascularization capacity contributed from the porosity as well as the lactic acid released from PLGA nanofiber. These results indicate the injectable bone cement with high strength, anti-washout property and controllable biodegradability is a promising candidate for bone regeneration in a minimally-invasive approach.

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Poly (lactide-co-glycolide) nanofiber incorporation reinforces the brittle CPC bone cement.

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The introduction of carboxymethyl cellulose offers good injectability and anti-washout resistance.

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PLGA nanofiber controllable biodegradability dynamically creates potential pores for bone formation and ingrowth.

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The cement continuously releases Ca²⁺ and lactic acid to improve bone regeneration and revascularization efficacy.

Optimization of an Injectable, Resorbable, Bioactive Cement Able to Release the Anti-Osteoclastogenic Biomolecule ICOS-Fc for the Treatment of Osteoporotic Vertebral Compression Fractures

Vertebral compression fractures are typical of osteoporosis and their treatment can require the injection of a cement through a minimally invasive procedure to restore vertebral body height. This study reports the development of an injectable calcium sulphate-based composite cement able to stimulate bone regeneration while inhibiting osteoclast bone resorption. To this aim, different types of strontium-containing mesoporous glass particles (Sr-MBG) were added to calcium sulphate powder to impart a pro-osteogenic effect, and the influence of their size and textural features on the cement properties was investigated. Anti-osteoclastogenic properties were conferred by incorporating into poly(lactic-co-glycolic)acid (PLGA) nanoparticles, a recombinant protein able to inhibit osteoclast activity (i.e., ICOS-Fc). Radiopaque zirconia nanoparticles (ZrO₂) were also added to the formulation to visualize the cement injection under fluoroscopy. The measured cement setting times were suitable for the clinical practice, and static mechanical testing determined a compressive strength of ca. 8 MPa, comparable to that of human vertebral bodies. In vitro release experiments indicated a sustained release of ICOS-Fc and Sr²⁺ ions up to 28 days. Overall, the developed cement is promising for the treatment of vertebral compression fractures and has the potential to stimulate bone regeneration while releasing a biomolecule able to limit bone resorption.

In Vitro and In Vivo Evaluation of Injectable Strontium-Modified Calcium Phosphate Cement for Bone Defect Repair in Rats

Calcium phosphate cement (CPC) has been widely studied, but its lack of osteoinductivity and inadequate mechanical properties limit its application, while strontium is able to promote bone formation and inhibit bone resorption. In this study, different proportions of tristrontium silicate were introduced to create a novel strontium-modified calcium phosphate cement (SMPC). The physicochemical properties of SMPC and CPC were compared, and the microstructures of the bone cements were characterized with scanning electron microscopy assays. Then, the effect of SMPC on cell proliferation and differentiation was examined. Furthermore, local inflammatory response and osteogenesis after SMPC implantation were also confirmed in the study. Finally, a rat model of isolated vertebral defects was used to test the biomechanical properties of the cements. The results showed that SMPC has better injectability and a shorter setting time than CPC. Meanwhile, the addition of tristrontium silicate promoted the mechanical strength of calcium phosphate cement, and the compressive strength of 5% SMPC increased to 6.00 ± 0.74 MPa. However, this promotion effect gradually diminished with an increase in tristrontium silicate, which was also found in the rat model of isolated vertebral defects. Furthermore, SMPC showed a more preferential role in promoting cell proliferation and differentiation compared to CPC. Neither SMPC nor CPC showed significant inflammatory responses in vivo. Histological staining suggested that SMPCs were significantly better than CPC in promoting new bone regeneration. Importantly, this osteogenesis effect of SMPC was positively correlated with the ratio of tristrontium silicate. In conclusion, 5% SMPC is a promising substitute material for bone repair with excellent physicochemical properties and biological activity.

A Novel Calcium Phosphate-Based Nanocomposite for Augmentation of Cortical Bone Trajectory Screw Fixation

Purpose

To evaluate the effect of cement augmentation of cortical bone trajectory (CBT) screws using a novel calcium phosphate–based nanocomposite (CPN).

Material and Methods

CBT screws were placed into cadaveric lumbar vertebrae. Depending on the material used for augmentation, they were divided into the following three groups: CPN, polymethylmethacrylate (PMMA), and control. Radiological imaging was used to evaluate the cement dispersion. Biomechanical tests were conducted to measure the stability of CBT screws. A rat cranial defect model was used to evaluate biodegradation and osseointegration of the CPN.

Results

After cement augmentation, the CPN tended to disperse into the distal part of the screws, whereas PMMA remained limited to the proximal part of the screws (P < 0.05). As for cement morphology, the CPN tended to form a concentrated mass, whereas PMMA arranged itself as a scattered cement cloud, but the difference was not significant (P > 0.05). The axial pullout test showed that the average maximal pullout force (Fmax) of CPN-augmented CBT screws was similar to that of the PMMA group (CPN, 1639.56 ± 358.21 N vs PMMA, 1778.45 ± 399.83 N; P = 0.745) and was significantly greater than that of the control group (1019.01 ± 371.98 N; P < 0.05). The average torque value in the CPN group was higher than that in the control group (CPN, 1.51 ± 0.78 N∙m vs control, 0.97 ± 0.58 N∙m) and lower than that in the PMMA group (1.93 ± 0.81 N∙m), but there were no statistically significant differences (P > 0.05). The CPN could be biodegraded and gradually replaced by newly formed bone tissue after 12 weeks in a rat cranial defect model.

Conclusion

The biocompatible CPN could be a valuable augmentation material to enhance CBT screw stability.

Different Associated Aspects That Influence Complication Rates on Clinical PKP Surgery Using Smart Medical Big Data

Osteoporotic vertebral compression fractures are on the rise in modern society due to the aging population, and this often results in painful symptoms and kyphotic abnormalities in patients. Bone cement was injected into the vertebral body to reinforce the vertebral body and restore most of the damaged vertebrae's natural height. Percutaneous kyphoplasty is the name given to this type of procedure (PKP). Bone cement leakage has been linked to several problems, according to the research. Neurological problems might arise if bone cement leaks into the spinal canal or the nerve root canal during surgery. As a result, PKP surgeons must now deal with the issue of reducing bone cement leakage. Using smart medical big data, this paper examines a sample of PKP operations and then examines different associated aspects that influence complication rates in order to better advice clinical PKP surgery use. There were 172 vertebral bodies in total in 72 patients receiving PKP surgery at a Chinese hospital that were examined by smart medical big data for vertebral degeneration and fusion. Bone cement leakage and variations in preoperative average anterior vertebral column height, preoperative Cobb angle, and the volume of injected bone cement were considered when dividing the patients into leakage and nonleakage groups; then, we figure out what is causing the bone cement to leak. Five patients experienced lung-related problems out of the 18 vertebral bodies with bone cement leaking that were selected for study. That leakage rate was 10.5%. The differences between the two groups in terms of vertebral compression and bone cement injection were statistically significant based on a single-factor analysis. Bone cement leakage in PKP surgery has been linked to the amount of bone cement injected and whether the vertebral body's peripheral wall was injured, according to multivariate analysis. Lung-related problems are more common in patients with a prior history of illness. Osteoporotic vertebral compression fractures can be successfully treated with percutaneous kyphoplasty. An important risk factor for bone cement extravasation in PKP surgery is the amount of bone cement injected, as well as its viscosity and whether damage to the vertebral body's peripheral wall has occurred.

INTRAVERTEBRAL EXPANDABLE IMPLANTS IN THORACOLUMBAR VERTEBRAL COMPRESSION FRACTURES

Current scientific evidence enhances the importance of the anatomic restauration of vertebral bodies with compression fractures aiming, as with other human body joints, to obtain a biomechanic and functional spine as close as the one prior to the fracture as possible. We consider that anatomic reduction of these fractures is only completely possible using intravertebral expandable implants, restoring vertebral endplate morphology, and enabling a more adequate intervertebral disc healing. This enables avoiding disc and osteodegenerative changes to that vertebral segment and its adjacent levels, as well as the anterior overload of adjacent vertebral bodies in older adults - a consequence of post-traumatic vertebral flattening - thus minimizing the risk of adjacent vertebral fractures. The ability of vertebral body fracture reduction and height maintenance over time and its percutaneous transpedicular application make the intra-vertebral expandable implants a very attractive option for treating these fractures. The authors show the direct and indirect reduction concepts of vertebral fractures, review the biomechanics, characteristics and indications of intravertebral expandable implants and present a suggestion for updating the algorithm for the surgical treatment of vertebral compression fractures which includes the use of intravertebral expandable implants. Level of Evidence V, Expert Opinion.

Antibiotic-loaded bone cement combined with vacuum sealing drainage to treat deep sternal wound infection following cardiac surgery: the first case report

Background

Deep sternal wound infection (DSWI) is a rare but serious complication after median sternotomy, and treatment success depends mainly on surgical experience. Here we first present a case of a patient successfully treated for antibiotic-loaded bone cement (ALBC) combined with vacuum sealing drainage (VSD) of DSWI.

Case presentation

This case report presented a patient who underwent open heart surgery, and suffered postoperatively from a DSWI associated with enterococcus cloacae. Focus debridement combined with ALBC filling and VSD was conducted in stage I. Appropriate antibiotics were started according to sensitivity to be continued for 2 weeks until the inflammatory markers decreased to normal. One month after the surgery, patient’s wound was almost healed and was discharged from hospital with a drainage tube. Two months after the stage I surgery procedure, the major step was removing the previous ALBC, and extensive debridement in stage II. The patient fully recovered without further surgical treatment.

Conclusions

The results of this case suggest that ALBC combined with VSD may be a viable and safe option for deep sternal wound reconstruction.

Stentoplasty with Resorbable Calcium Salt Bone Void Fillers for the Treatment of Vertebral Compression Fracture: Evaluation After 3 Years

Purpose

The aim of the study is to investigate the clinical and radiological outcomes of vertebral compression fractures treated by stentoplasty with resorbable calcium salt bone void fillers compared with balloon kyphoplasty (BKP).

Methods

This prospective study included patients with fresh mono-thoracolumbar vertebral compression fractures. Patients enrolled were randomly divided into three groups. The patients in group A underwent stentoplasty with calcium sulfate/calcium phosphate (CSCP) composite filler and patients in group B with hydroxyapatite/collagen (HAP/COL) composite filler, while patients in group C underwent BKP with polymethylmethacrylate (PMMA). The clinical outcome was evaluated with visual analogue pain scale (VAS) and Oswestry disability score (ODI). The radiological results were evaluated with anterior height (AH) and Cobb angle of vertebral body. Computed tomography (CT) was used to assess osteogenesis effect.

Results

Each group included 14 patients. The VAS, ODI, Cobb angle and AH were statistically improved compared with preoperative and there was no significant difference between the three groups. However, the AH in group A and group B at 1-year follow-up presented slight loss compared with 1 day after surgery. CT results suggested both group A and group B presented obvious bone trabecula formation and variations of CT value.

Conclusion

The stentoplasty with resorbable calcium salt bone void fillers demonstrated clinical outcomes similar to traditional BKP for vertebral compression fractures. Both HAP/COL and CSCP performed certain osteogenesis. However, stentoplasty with studied fillers showed slight loss of AH within 1 year after surgery.

Tough and injectable fiber reinforced calcium phosphate cement as an alternative to polymethylmethacrylate cement for vertebral augmentation: a biomechanical study

Vertebral compression fractures (VCFs) are a very common problem among the elderly, which ultimately result in severe pain and a drastically reduced quality of life. An effective treatment for VCFs is the minimally invasive augmentation of the damaged vertebrae through vertebroplasty and/or kyphoplasty. These surgical procedures treat the affected vertebrae by injection of poly(methyl methacrylate) cement (PMMA) into the vertebral body. However, clinical use of PMMA cement is associated with major drawbacks. Bioceramic cements such as injectable calcium phosphate cements (CPC) exhibit a superior osteocompatibility over PMMA cements, but are too brittle for load-bearing applications. Here, we evaluated the handling and mechanical properties of a recently developed CPC formulation containing both poly(vinyl alcohol) (PVA) fibers and carboxymethyl cellulose (CMC) as an alternative to PMMA cement for vertebro- and kyphoplasty. Our results demonstrate that the addition of CMC rendered fiber-reinforced CPC injectable without negatively affecting its mechanical properties. Further, an ex vivo mechanical analysis clearly showed that extravasation of PVA fiber-reinforced CPC with CMC into trabecular bone was limited as compared to PMMA. Finally, we observed that the ex vivo biomechanical performance of vertebrae treated with CMC and PVA fibers was similar to PMMA-treated vertebrae. The obtained data suggests that PVA fiber-reinforced CPCs with CMC possesses adequate handling, mechanical and structural characteristics for vertebro- and kyphoplasty procedures. These data pave the way for future preclinical studies on the feasibility of treating vertebral compression fractures using PVA fiber-reinforced CPC with CMC.

Calcium Phosphate Cement Causes Nucleus Pulposus Cell Degeneration through the ERK Signaling Pathway

While calcium phosphate cement (CPC) is recognized as one of the most likely substitutes for the conventional Polymethylmethacrylate (PMMA), there are very few studies about its intradiscal leakage consequences. Herein, the goal of our study was to examine the effect of CPC particles on the ERK (extracellular regulatory kinase) pathway in human nucleus pulposus cell (HNPC) degeneration. Different concentrations of CPC particles (0.00‰, 0.01‰, 0.05‰, 0.1‰ v/v) were added to human nucleus pulposus cell cultures. After 10 days of treatment, HNPC biological behaviors and degeneration degree were analyzed by CCK-8 assay, crystal violet staining, flow cytometer and western blot. The effect of CPC on the ERK pathway was also analyzed by western blot. After activating the ERK path by overexpressing Ras, HNPCs’ biological behaviors and degeneration degree were analyzed again. We found that CPC particles had a negative effect on human nucleus pulposus cells (HNPCs), which are mainly reflected in cell growth and the cell cycle. After activation of the ERK signaling pathway, the negative effects of CPC on cell growth and the cell cycle were significantly reduced and the degeneration degree of HNPCs was reversed. CPC particles can probably block the activation of the ERK pathway, thus causing the HNPCs’ degeneration.

Osteogenesis enhancement of silk fibroin/ α-TCP cement by N-acetyl cysteine through Wnt/β-catenin signaling pathway in vivo and vitro

High brittleness and lack osteogenesis are two major limitations of calcium phosphate cement (CPC) in application in bone defect reconstruction. Here we prepared a composite calcium phosphate cement by mixing N-acetyl cysteine loaded silk fibroin solution with α-tricalcium phosphate. In vitro cytology experiment revealed that SF-NAC/α-TCP could significantly increase the activity of exocrine ALP and up-regulated expression of bone-related genes. However, NAC up-regulated gene expression could be significantly suppressed by DKK1. We propose that NAC functioning as osteogenic factor by activating the Wnt/β-catenin signaling pathway may be the possible mechanism of up-regulation of osteogenic genes. Bone regeneration in vivo shown in a rat femur defect was enhanced by the addition of NAC in SF/α-TCP. In addition, the combination intensity of cement-bone interface was improved. The combination SF-NAC/α-TCP might be developed into a promising tool for bone tissue repair in the clinic.

Preparation and cytocompatibility of a novel bismuth aluminate/calcium phosphate cement with high radiopacity

In a minimally invasive surgery, using a bone cement being radiologically detectable is vital to the success of the procedure and avoiding cement leakage in the early stage. The radiopacity of calcium phosphate cement (CPC) is inadequate, thus limiting its clinic application in this area. In this work, bismuth aluminate (BiA) was employed as a radiopaque agent for CPC. The influences of BiA on physicochemical, radiopaque and in vitro biocompatible properties of CPC were investigated. With the increasing content of BiA, the setting time and the compressive strength of CPC were augmented, while the injectability of the cement pastes was reduced. The radiopacity of CPC was significantly improved by adding more than 6 wt.% BiA. CPC specimens with less than 12 wt.% BiA showed good cellular affinity. Moreover, the CPC containing 6 and 9 wt.% BiA promoted the cell growth and ALP activity of mouse bone marrow mesenchymal stem cells when compared with the control. On the basis of its improved radiopacity and cytocompatibility, the radiopaque CPC with 6 ~ 9 wt.% BiA is expected to be a potential substitute for bone defect restoration via minimally invasive surgery. CPC with bismuth aluminate reveals better radiopacity and cell affinity along with proper physicochemical properties.

Is vertebral body stenting in combination with CaP cement superior to kyphoplasty?

PURPOSE

In the evolution of the minimally invasive treatment of vertebral compression fractures, vertebral body stenting (VBS) was developed to reduce intraoperative and secondary loss of vertebral height. Particularly in combination with the usage of biodegradable cement, the influence of VBS on the rate of intraoperative complications and long-term outcome is unclear. The purpose of this study was to investigate the differences between balloon kyphoplasty (BKP) and VBS regarding their long-term clinical and radiological outcome in combination with calcium phosphate (CaP) application instead of polymethyl methacrylate (PMMA).

METHODS

This retrospective study included 49 patients with fresh mono-segmental thoracolumbar fractures without neurological signs treated with VBS or BKP and CaP cement (Calcibone). The outcome was evaluated with the visual analogue pain scale (VAS), the Oswestry disability score (ODI), and radiologically assessed.

RESULTS

In the course of the radiological follow-up, the VBS group showed statistically significant less vertebral height loss than the BKP group. However, with respect to VAS and ODI scores there were no statistically significant differences between the VBS and BKP group in the clinical follow-up. The rate of cement leakage was comparable in both groups.

CONCLUSIONS

Both techniques facilitated good clinical results in combination with absorbable cement augmentation. In particular, the VBS enabled us to benefit from the advantages of the resorbable isothermic CaP cement with an improved radiological outcome in the long term compared to BKP. However, there was a mentionable loss of reduction in the follow-up in both groups compared to previously published data with PMMA cement. These slides can be retrieved under Electronic Supplementary Material.

A REVIEW ON BIOMECHANICAL ASPECTS OF VERTEBROPLASTY AND KYPHOPLASTY USING FINITE ELEMENT MODELING-BASED METHODS

The vertebroplasty (VP) and kyphoplasty (KP) are two minimally invasive surgeries using cement augmentation to treat the osteoporotic vertebrae in elderlies in order to relieve pain and prevent the continuation of microfractures. Biomechanists have always tried to assess the mechanical behavior of vertebrae after cement augmentation by using both the experimental and theoretical methods such as finite element modeling (FEM).

In this study, 31 related articles using FEM in analyzing the VP and KP have been reviewed. This study included two main categories of spinal load distribution and tension in vertebrae after the VP and KP operations. This could be obtained by conducting FEM on the whole spine or other sectors of it such as intervertebral disc (IVD) or end plates (EPs). This study also referred to articles predicting the probability of adjacent fractures following VP and KP. The most common software employed in FEM was ABAQUS, applied for static and dynamic loads’ analyses.

It was found that most of the reviewed articles adopted reverse engineering techniques by converting 2D computed tomography (CT) scan images into 3D reconstructed models. The material properties were generally taken from the literature. In more than 80% of studies, the model geometry was based on CT data of the spine. Almost 45% of the studies have attempted to compare the simulated vertebra after augmentation with experimental results taken from the literature (5% of the reviewed articles) or their own experimental tests (40% of the reviewed articles).

Osteointegration and Resorption of Intravertebral and Extravertebral Calcium Phosphate Cement

STUDY DESIGN

Eleven patients with painful osteoporotic vertebral fractures who underwent kyphoplasty using calcium phosphate (CaP) cement were followed up for 1 week, 1, 2, and 3 years in a monocentric, nonrandomized, noncontrolled retrospective trial.

OBJECTIVE

This study investigates long-term radiomorphologic features of intraosseous CaP cement implants and of extraosseous CaP cement leakages for up to 3 years after implantation by kyphoplasty.

SUMMARY OF BACKGROUND DATA

Kyphoplasty is frequently used for the treatment of painful osteoporotic fractures. Of the materials available, CaP is frequently used as a filling material. Resorption of this material is frequently observed, although clinical outcome is comparable with other cements.

METHODS

Kyphoplasty utilizing CaP cement was performed in 11 patients with painful osteoporotic vertebral fractures. All patients received a pharmacological antiosteoporosis treatment consisting of calcium, vitamin D, and a standard dose of oral bisphosphonates. Radiomorphologic measurements, pain, and mobility were assessed.

RESULTS

Intraosseous and extraosseous CaP cement volumes decreased significantly over 3 years. However, vertebral stability as determined by a constant vertebral body height and the sagittal index was not impaired. Pain improved significantly 2 years after implantation and the mobility scores 1 year after kyphoplasty at least until the third year.

CONCLUSIONS

Intravertebral CaP cement implants are resorbed slowly over time without jeopardizing stability and clinical outcomes most likely because of a slowly progressing osseous replacement. Extraosseous CaP cement material because of leakages during the kyphoplasty procedure is almost completely resorbed as early as 2 years after the leakage occurred. Therefore, CaP cement is an important alternative to PMMA-based cement materials utilized for kyphoplasty of osteoporotic vertebral fractures.

Preparation and characterisation of an innovative injectable calcium sulphate based bone cement for vertebroplasty application

Spine-Ghost: a novel injectable resorbable cement containing mesoporous bioactive glass and a radiopaque glass-ceramic phase in a calcium sulphate matrix.

Dislodgement and gastrointestinal tract penetration of bone cement used for spinal reconstruction after lumbosacral vertebral tumor excision: A case report

INTRODUCTION

Polymethylmethacrylate (PMMA) cement is useful for spinal reconstruction, but can cause complications including new vertebral fractures, neurological disorders and pulmonary embolism. We report a case in PMMA cement used for spinal reconstruction after tumor curettage dislodged and penetrated the gastrointestinal tract.

DIAGNOSES

The patient was diagnosed with a retroperitoneal extragonadal germ cell tumor at age 27 years. After chemotherapy and tumor resection, the tumor remained. It gradually increased in size and infiltrated lumbosacral vertebrae, causing him to present at age 35 years with increased low back pain. Image findings showed bone destruction in the vertebral bodies accompanied by neoplastic lesions. The left and right common iliac arteries and inferior vena cava were enclosed in the tumor on the anterior side of the vertebral bodies. Lumbosacral bone tumor due to direct extragonadal germ cell tumor infiltration was diagnosed. A 2-step operation was planned; first, fixation of the posterior side of the vertebral bodies, followed by tumor resection using an anterior transperitoneal approach, and spinal reconstruction using PMMA cement. After surgery, the PMMA cement gradually dislodged towards the anterior side and, 2 years 9 months after surgery, it had penetrated the retroperitoneum. The patient subsequently developed nausea and abdominal pain and was readmitted to hospital. The diagnosis was intestinal blockage with dislodged PMMA cement, and an operation was performed to remove the cement present in the small intestine. There was strong intra-abdominal adhesion, the peritoneum between the vertebral bodies and intestine could not be identified, and no additional treatment for vertebral body defects could be performed. After surgery, gastrointestinal symptoms resolved.

CONCLUSION

Although this was a rare case, when using bone cement for vertebral body reconstruction, the way of anchoring for the cement must be thoroughly planned to assure no cement dislodgement can occur.

First-time systematic postoperative clinical assessment of a minimally invasive approach for lumbar ventrolateral vertebroplasty in the large animal model sheep

BACKGROUND CONTEXT

Large animal models are highly recommended for meaningful preclinical studies, including the optimization of cement augmentation for vertebral body defects by vertebroplasty/kyphoplasty.

PURPOSE

The aim of this study was to perform a systematic characterization of a strictly minimally invasive in vivo large animal model for lumbar ventrolateral vertebroplasty.

STUDY DESIGN/ SETTING

This is a prospective experimental animal study.

METHODS

Lumbar defects (diameter 5 mm; depth approximately 14 mm) were created by a ventrolateral percutaneous approach in aged, osteopenic, female sheep (40 Merino sheep; 6-9 years; 68-110 kg). L1 remained untouched, L2 was left with an empty defect, and L3 carried a defect injected with a brushite-forming calcium phosphate cement (CPC). Trauma/functional impairment, surgical techniques (including drill sleeve and working canula with stop), reproducibility, bone defects, cement filling, and functional cement augmentation were documented by intraoperative incision-to-suture time and X-ray, postoperative trauma/impairment scores, and ex vivo osteodensitometry, microcomputed tomography (CT), histology, static/fluorescence histomorphometry, and biomechanical testing.

RESULTS

Minimally invasive vertebroplasty resulted in short operation times (28±2 minutes; mean±standard error of the mean) and X-ray exposure (1.59±0.12 minutes), very limited local trauma (score 0.00±0.00 at 24 hours), short postoperative recovery (2.95±0.29 hours), and rapid decrease of the postoperative impairment score to 0 (3.28±0.36 hours). Reproducible defect creation and cement filling were documented by intraoperative X-ray and ex vivo conventional/micro-CT. Vertebral cement augmentation and osteoconductivity of the CPC was verified by osteodensitometry (CPC>control), micro-CT (CPC>control and empty defect), histology/static histomorphometry (CPC>control and empty defect), fluorescence histomorphometry (CPC>control; all p<.05 for 3 and 9 months), and compressive strength measurements (CPC numerically higher than control; 102% for 3 months and 110% for 9 months).

CONCLUSIONS

This first-time systematic clinical assessment of a minimally invasive, ventrolateral, lumbar vertebroplasty model in aged, osteopenic sheep resulted in short operation times, rapid postoperative recovery, and high experimental reproducibility. This model represents an optimal basis for standardized evaluation of future studies on vertebral augmentation with resorbable and osteoconductive CPC.

[Kyphoplasty-Vertebroplasty. A critical assessment]

CLINICAL ISSUE

Painful vertebral compression fractures.

STANDARD TREATMENT

Analgesia.

TREATMENT INNOVATIONS

Osteoplastic procedures, such as kyphoplasty and vertebroplasty.

DIAGNOSTIC WORKUP

Anamnestic and radiological associations of clinical complaints with the radiomorphological findings of vertebral compression fractures are required for an adequate consideration to assess whether an osteoplastic procedure should be carried out. A computed tomography (CT) scan allows a reliable judgement whether an osteoplastic procedure is technically feasible and promising to improve the local vertebral fracture-associated pain.

PERFORMANCE

Prospective controlled trials have demonstrated a satisfactory improvement of back pain associated with vertebral fractures and parameters of quality of life by osteoplastic interventions.

ACHIEVEMENTS

No prospective, truly sham-controlled blind trials are currently available which demonstrate an advantage of osteoplastic interventions compared to standard pain treatment; however, the currently published prospective controlled trials show a satisfactory pain reduction by osteoplastic interventions, such as kyphoplasty and vertebroplasty.

PRACTICAL RECOMMENDATIONS

Painful vertebral fractures and progressive loss of vertebral height of compression fractures should be evaluated in an interdisciplinary team consisting of radiologists, spinal surgeons and internists to assess whether an osteoplastic procedure is technically feasible and promising to improve local pain and immobility associated with vertebral fractures.

What's new in vertebral cementoplasty?

Vertebral cementoplasty is a well-known mini-invasive treatment to obtain pain relief in patients affected by vertebral porotic fractures, primary or secondary spine lesions and spine trauma through intrametameric cement injection. Two major categories of treatment are included within the term vertebral cementoplasty: the first is vertebroplasty in which a simple cement injection in the vertebral body is performed; the second is assisted technique in which a device is positioned inside the metamer before the cement injection to restore vertebral height and allow a better cement distribution, reducing the kyphotic deformity of the spine, trying to obtain an almost normal spine biomechanics. We will describe the most advanced techniques and indications of vertebral cementoplasty, having recently expanded the field of applications to not only patients with porotic fractures but also spine tumours and trauma.

CONTROVERSIES ON VERTEBROPLASTY AND KYPHOPLASTY FOR VERTEBRAL COMPRESSION FRACTURES

Vertebroplasty and kyphoplasty are widely used for osteoporotic and cancer-related vertebral compression fractures refractory to medical treatment. Many aspects of these procedures have been extensively discussed in the literature during the last few years. In this article, we perform a critical appraisal of current evidence on effectiveness and ongoing controversies regarding surgical technique, indications and contraindications, clinical outcomes and potential complications of these procedures.

Reinforcement Strategies for Load-Bearing Calcium Phosphate Biocements

Calcium phosphate biocements based on calcium phosphate chemistry are well-established biomaterials for the repair of non-load bearing bone defects due to the brittle nature and low flexural strength of such cements. This article features reinforcement strategies of biocements based on various intrinsic or extrinsic material modifications to improve their strength and toughness. Altering particle size distribution in conjunction with using liquefiers reduces the amount of cement liquid necessary for cement paste preparation. This in turn decreases cement porosity and increases the mechanical performance, but does not change the brittle nature of the cements. The use of fibers may lead to a reinforcement of the matrix with a toughness increase of up to two orders of magnitude, but restricts at the same time cement injection for minimal invasive application techniques. A novel promising approach is the concept of dual-setting cements, in which a second hydrogel phase is simultaneously formed during setting, leading to more ductile cement–hydrogel composites with largely unaffected application properties.

Is thoracolumbar fascia injury the cause of residual back pain after percutaneous vertebroplasty? A prospective cohort study

Some patients with osteoporotic vertebral compression fractures still suffer from back pain after percutaneous vertebroplasty. We have found that osteoporotic vertebral compression fractures with thoracolumbar fascia injury are common and that thoracolumbar fascia injury may account for the residual pain after percutaneous vertebroplasty.

PURPOSE

Osteoporotic vertebral compression fractures are successfully treated with percutaneous vertebroplasty (PVP). However, some patients still suffer from back pain after the procedure. We hypothesized that there is a relationship between thoracolumbar (TL) fascia injury and residual postoperative pain.

METHODS

This prospective study included 133 elderly patients (age range 55 - 92 years) with osteoporotic vertebral compression fractures treated with PVP from February 2010 to March 2012 in our hospital. The patients were divided into two groups based on the presence of TL fascia injury. A visual analog scale (VAS) and the Chinese modified Oswestry Disability Index were used to evaluate the pain before and after PVP.

RESULTS

The mean VAS score and the Chinese modified Oswestry Disability Index in the patients with TL fascia injury were reduced from 9.11 ± 0.76 to 6.4 ± 1.1 and 73.93 ± 1.46% to 44.6 ± 3.1%, respectively, and in the patients without TL fascia injury from 9.26 ± 0.82 to 8.0 ± 1.3 and 73.96 ± 1.38% to 51.7 ± 1.8%, respectively. Pain and disability were reduced more in patients without TL fascia injury than in those with TL fascia injury (both p < 0.05).

CONCLUSIONS

There may be a relationship between TL fascia injury and residual back pain after PVP.

Controversial issues in kyphoplasty and vertebroplasty in malignant vertebral fractures

BACKGROUND

Kyphoplasty (KP) and vertebroplasty (VP) have been successfully employed in the treatment of pathological vertebral fractures.

METHODS

A critical review of the medical literature was performed and controversial issues were analyzed.

RESULTS

Evidence supports KP as the treatment of choice to control fracture pain and the possible restoration of sagittal balance, provided that no overt instability or myelopathy is present, the fracture is painful and other pain generators have been excluded, and positive radiological findings are present. Unilateral procedures yield similar results to bilateral ones and should be pursued whenever feasible. Biopsy should be routinely performed and 3 to 4 levels may be augmented in a single operation. Higher cement filling appears to yield better results. Radiotherapy is complementary with KP and VP but must be individualized.

CONCLUSIONS

In cases of painful cancer fractures, if overt instability or myelopathy is not present, unilateral KP should be pursued, whenever feasible, followed by radiotherapy. The technological advances in hardware and biomaterials, as well as combining KP with other modalities, will help ensure a safe and more effective procedure. Address.

Nanocomposite bone scaffolds based on biodegradable polymers and hydroxyapatite

In tissue engineering, development of an osteoconductive construct that integrates with host tissue remains a challenge. In this work, the effect of bone-like minerals on maturation of pre-osteoblast cells was investigated using polymer-mineral scaffolds composed of poly(propylene fumarate)-co-poly(caprolactone) (PPF-co-PCL) and nano-sized hydroxyapatite (HA). The HA of varying concentrations was added to an injectable formulation of PPF-co-PCL and the change in thermal and mechanical properties of the scaffolds was evaluated. No change in onset of degradation temperature was observed due to the addition of HA, however compressive and tensile moduli of copolymer changed significantly when HA amounts were increased in composite formulation. The change in mechanical properties of copolymer was found to correlate well to HA concentration in the constructs. Electron microscopy revealed mineral nucleation and a change in surface morphology and the presence of calcium and phosphate on surfaces was confirmed using energy dispersive X-ray analysis. To characterize the effect of mineral on attachment and maturation of pre-osteoblasts, W20-17 cells were seeded on HA/copolymer composites. We demonstrated that cells attached more to the surface of HA containing copolymers and their proliferation rate was significantly increased. Thus, these findings suggest that HA/PPF-co-PCL composite scaffolds are capable of inducing maturation of pre-osteoblasts and have the potential for use as scaffold in bone tissue engineering.

In situ osteoblast mineralization mediates post-injection mechanical properties of osteoconductive material

The objective of this study was to understand the temporal relationship between in situ generated calcium content (mineralization) and the mechanical properties of an injectable orthobiologic bone-filler material. Murine derived osteoblast progenitor cells were differentiated using osteogenic factors and encapsulated within an injectable polycaprolactone nanofiber-collagen composite scaffold (PN-COL +osteo) to evaluate the effect of mineralization on the mechanical properties of the PN-COL scaffold. A comprehensive study was conducted using both an experimental and a predictive analytical mechanical analysis for mechanical property assessment as well as an extensive in vitro biological analysis for in situ mineralization. Cell proliferation was evaluated using a PicoGreen dsDNA quantification assay and in situ mineralization was analyzed using both an alkaline phosphatase (ALP) assay and an Alizarin Red stain-based assay. Mineralized matrix formation was further evaluated using energy dispersive x-ray spectroscopy (EDS) and visualized using SEM and histological analyses. Compressive mechanical properties of the PN-COL scaffolds were determined using a confined compression stress-relaxation protocol and the obtained data was fit to the standard linear solid viscoelastic material mathematical model to demonstrate a relationship between increased in situ mineralization and the mechanical properties of the PN-COL scaffold. Cell proliferation was constant over the 21 day period. ALP activity and calcium concentration significantly increased at day 14 and 21 as compared to PN-COL -osteo with undifferentiated osteoblast progenitor cells. Furthermore, at day 21 EDS, SEM and von Kossa histological staining confirmed mineralized matrix formation within the PN-COL scaffolds. After 21 days, compressive modulus, peak stress, and equilibrium stress demonstrate significant increases of 3.4-fold, 3.3-fold, and 4.0-fold respectively due to in situ mineralization. Viscoelastic parameters calculated through the standard linear solid mathematical model fit to the stress-relaxation data also indicate improved mechanical properties after in situ mineralization. This investigation clearly demonstrates that in situ mineralization can increase the mechanical properties of an injectable orthobiologic scaffold and can possibly guide the design of an effective osteoconductive injectable material.

Comparative review of vertebroplasty and kyphoplasty

The aim of this review is to compare the effectiveness of percutaneous vertebroplasty and kyphoplasty to treat pain and improve functional outcome from vertebral fractures secondary to osteoporosis and tumor conditions. In 2009, two open randomized controlled trials published in the New England Journal of Medicine questioned the value of vertebroplasty in treating vertebral compression fractures. Nevertheless, the practice of physicians treating these conditions has barely changed. The objective of this review is to try to clarify the most important issues, based on our own experience and the reported evidence about both techniques, and to guide towards the most appropriate choice of treatment of vertebral fractures, although many questions still remain unanswered.

Controversial issues in kyphoplasty and vertebroplasty in osteoporotic vertebral fractures

Kyphoplasty (KP) and vertebroplasty (VP) have been successfully employed for many years for the treatment of osteoporotic vertebral fractures. The purpose of this review is to resolve the controversial issues raised by the two randomized trials that claimed no difference between VP and SHAM procedure. In particular we compare nonsurgical management (NSM) and KP and VP, in terms of clinical parameters (pain, disability, quality of life, and new fractures), cost-effectiveness, radiological variables (kyphosis correction and vertebral height restoration), and VP versus KP for cement extravasation and complications profile. Cement types and optimal filling are analyzed and technological innovations are presented. Finally unipedicular/bipedicular techniques are compared. Conclusion. VP and KP are superior to NSM in clinical and radiological parameters and probably more cost-effective. KP is superior to VP in sagittal balance improvement and cement leaking. Complications are rare but serious adverse events have been described, so caution should be exerted. Unilateral procedures should be pursued whenever feasible. Upcoming randomized trials (CEEP, OSTEO-6, STIC-2, and VERTOS IV) will provide the missing link.

Demineralization after balloon kyphoplasty with calcium phosphate cement: a histological evaluation in ten patients

PURPOSE

Balloon kyphoplasty (BKP) with calcium phosphate cement (CPC) is increasingly being used for spinal surgery in younger patients. In routinely performed follow-up CT scans we observed considerable areas of demineralization in CPC processed vertebrae in several patients. To rule out infections or inflammations histological examinations were planned for these patients.

METHODS

Ten patients (23-54 years; six men) with significant demineralization areas in CT scans after CPC balloon kyphoplasty were selected. Punch biopsies from these areas were taken in local anesthesia using a biopsy needle. One half of the specimen was decalcified and embedded in paraffin, and sections were examined histologically using hematoxylin and eosin, Van Gieson, and trichrome staining. The second half of the specimen was cast directly in methyl methacrylate and sections were examined by Paragon and von Kossa/Safranin staining. Stained slides were viewed under light microscopy.

RESULTS

Bone-punch specimens were taken at 17.5 months (mean) after BKP with CPC. In most cases, the cement was well surrounded by newly formed lamellar bone with very tight connections between the cement and new bone. Unmineralized areas were observed sporadically at the cement surface and adjacent to the implant. There were no pronounced signs of inflammation or osteolysis of adjacent bone. No complications were observed during or following patients' biopsy procedures.

CONCLUSIONS

CPC demonstrated good biocompatibility and osseointegration in clinical use, with no evidence of inflammation or osteonecrosis. Demineralized areas in CT scans could be a result of remodeling of the cancellous bone in vertebral bodies.

Kyphopasty and vertebroplasty

Vertebroplasty and balloon kyphoplasty are percutaneous techniques performed under radioscopic control. They were initially developed for tumoral and osteoporotic lesions; indications were later extended to traumatology for the treatment of pure compression fracture. They are an interesting alternative to conventional procedures, which are often very demanding. The benefit of these minimally invasive techniques has been demonstrated in terms of alleviation of pain, functional improvement and reduction in both morbidity and costs for society. The principle of kyphoplasty is to restore vertebral body anatomy gently and progressively by inflating balloons and then reinforcing the anterior column of the vertebra with cement. In vertebroplasty, cement is introduced directly under pressure, without prior balloon inflation. Both techniques can be associated to minimally invasive osteosynthesis in certain indications. In our own practice, we preferably use acrylic cement, for its biomechanical properties and resistance to compression stress. We use calcium phosphate cement in young patients, but only associated to percutaneous osteosynthesis due to the risk of secondary correction loss. The evolution of these techniques depends on improving personnel radioprotection and developing new systems of vertebral expansion.

Adverse prognostic factors and optimal intervention time for kyphoplasty/vertebroplasty in osteoporotic fractures

Introduction. While evidence supports the efficacy of vertebral augmentation (kyphoplasty and vertebroplasty) for the treatment of osteoporotic fractures, randomized trials disputed the value of vertebroplasty. The aim of this analysis is to determine the subset of patients that may not benefit from surgical intervention and find the optimal intervention time. Methods. 27 prospective multiple-arm studies with cohorts of more than 20 patients were included in this meta-analysis. We hereby report the results from the metaregression and subset analysis of those trials reporting on treatment of osteoporotic fractures with kyphoplasty and/or vertebroplasty. Results. Early intervention (first 7 weeks after fracture) yielded more pain relief. However, spontaneous recovery was encountered in hyperacute fractures (less than 2 weeks old). Patients suffering from thoracic fractures or severely deformed vertebrae tended to report inferior results. We also attempted to formulate a treatment algorithm. Conclusion. Intervention in the hyperacute period should not be pursued, while augmentation after 7 weeks yields less consistent results. In cases of thoracic fractures and significant vertebral collapse, surgeons or interventional radiologists may resort earlier to operation and be less conservative, although those parameters need to be addressed in future randomized trials.

Biomechanical evaluation of an injectable and biodegradable copolymer P(PF-co-CL) in a cadaveric vertebral body defect model

A novel biodegradable copolymer, poly(propylene fumarate-co-caprolactone) [P(PF-co-CL)], has been developed in our laboratory as an injectable scaffold for bone defect repair. In the current study, we evaluated the ability of P(PF-co-CL) to reconstitute the load-bearing capacity of vertebral bodies with lytic lesions. Forty vertebral bodies from four fresh-frozen cadaveric thoracolumbar spines were used for this study. They were randomly divided into four groups: intact vertebral body (intact control), simulated defect without treatment (negative control), defect treated with P(PF-co-CL) (copolymer group), and defect treated with poly(methyl methacrylate) (PMMA group). Simulated metastatic lytic defects were made by removing a central core of the trabecular bone in each vertebral body with an approximate volume of 25% through an access hole in the side of the vertebrae. Defects were then filled by injecting either P(PF-co-CL) or PMMA in situ crosslinkable formulations. After the spines were imaged with quantitative computerized tomography, single vertebral body segments were harvested for mechanical testing. Specimens were compressed until failure or to 25% reduction in body height and ultimate strength and elastic modulus of each specimen were then calculated from the force-displacement data. The average failure strength of the copolymer group was 1.83 times stronger than the untreated negative group and it closely matched the intact vertebral bodies (intact control). The PMMA-treated vertebrae, however, had a failure strength 1.64 times larger compared with the intact control. The elastic modulus followed the same trend. This modulus mismatch between PMMA-treated vertebrae and the host vertebrae could potentially induce a fracture cascade and degenerative changes in adjacent intervertebral discs. In contrast, P(PF-co-CL) restored the mechanical properties of the treated segments similar to the normal, intact, vertebrae. Therefore, P(PF-co-CL) may be a suitable alternative to PMMA for vertebroplasty treatment of vertebral bodies with lytic defects.

Bone graft substitutes currently available in orthopaedic practice: the evidence for their use

We reviewed 59 bone graft substitutes marketed by 17 companies currently available for implantation in the United Kingdom, with the aim of assessing the peer-reviewed literature to facilitate informed decision-making regarding their use in clinical practice. After critical analysis of the literature, only 22 products (37%) had any clinical data. Norian SRS (Synthes), Vitoss (Orthovita), Cortoss (Orthovita) and Alpha-BSM (Etex) had Level I evidence. We question the need for so many different products, especially with limited published clinical evidence for their efficacy, and conclude that there is a considerable need for further prospective randomised trials to facilitate informed decision-making with regard to the use of current and future bone graft substitutes in clinical practice.

Balloon kyphoplasty in patients with osteoporotic vertebral compression fractures

Balloon kyphoplasty (BKP) is a minimally invasive surgical procedure indicated for treatment of painful vertebral compression fractures. During BKP, cannulae are placed percutaneously into the vertebral body, allowing insertion of inflatable balloons. Inflating the balloons partially restores vertebral body height, compacts the bone and creates a cavity for placement of bone cement after balloon removal. Placement of the cement reduces and stabilizes the fracture. BKP differs from vertebroplasty in that it aims to restore vertebral height and reduce kyphotic deformity. Case reports and observational studies have consistently shown that BKP significantly reduces pain, increases mobility and functional capacity and improves quality of life for up to 3 years. Clinically significant adverse events have been rarely reported. These findings were confirmed in randomized and nonrandomized prospective controlled studies. The objective of this review is to describe the surgical procedures involved in BKP and to review the evidence supporting its use.

Differential blood contamination levels and powder-liquid ratios can affect the compressive strength of calcium phosphate cement (CPC): a study using a transpedicular vertebroplasty model

PURPOSE

Calcium phosphate cement (CPC) is a potentially useful alternative to polymethylmethacrylate (PMMA) for transpedicular injection into osteoporotic vertebral fractures. Unlike PMMA, CPC is both biocompatible and osteoconductive without producing heat from polymerization, but it has lower compressive strength compared to PMMA. This in vitro model experiment analyzed how different CPC powder-liquid ratios (P/L ratios) and injection methods may minimize blood contamination in the CPC and, thereby its reduction in compressive strength.

METHODS

(1) CPC of different P/L ratios of 4.0, 3.5, and 3.2 was equally mixed with different amounts of freshly obtained human venous blood, producing cylindrically shaped CPC samples. (2) Using a transpedicular vertebroplasty model containing blood in the bottom, CPC pastes of different P/L ratios were injected with the nozzle of an injection gun affixed either to the bottom (Bottom method) or to the top of the container (Top method). All cylindrical CPC samples thus obtained were immersed in simulated body fluid and then underwent compressive strength tests at 3 h-7 days post-immersion.

RESULTS

In CPC equally mixed with blood, lower P/L ratios and a larger amount of blood contamination reduced compressive strength more significantly. Of the two methods of CPC injection, the 'Bottom method' produced significantly greater compressive strength values than the 'Top method'.

CONCLUSIONS

When performing CPC-assisted vertebroplasty, a greater load bearing-support can be obtained by injecting CPC paste of a high P/L ratio of 4.0 into the deepest part of the space inside the vertebral body to minimize blood contamination.

Synthesis of spherical calcium phosphate particles for dental and orthopedic applications

Calcium phosphate materials have been used increasingly in the past 40 years as bone graft substitutes in the dental and orthopedic fields. Accordingly, numerous fabrication methods have been proposed and used. However, the controlled production of spherical calcium phosphate particles remains a challenge. Since such particles are essential for the synthesis of pastes and cements delivered into the host bone by minimally-invasive approaches, the aim of the present document is to review their synthesis and applications. For that purpose, production methods were classified according to the used reagents (solutions, slurries, pastes, powders), dispersion media (gas, liquid, solid), dispersion tools (nozzle, propeller, sieve, mold), particle diameters of the end product (from 10 nm to 10 mm), and calcium phosphate phases. Low-temperature calcium phosphates such as monetite, brushite or octacalcium phosphate, as well as high-temperature calcium phosphates, such as hydroxyapatite, β-tricalcium phosphate or tetracalcium phosphate, were considered. More than a dozen production methods and over hundred scientific publications were discussed.

Intervertebral disc viability after burst fractures of the thoracic and lumbar spine treated with pedicle screw fixation and direct end-plate restoration

BACKGROUND CONTEXT

Controversies persist for the best treatment of burst fractures of the thoracolumbar spine. Anterior corpectomy and discectomy followed by reconstruction with intervertebral cage and posterior fixation, for example, are based mainly on the widespread assumption that intervertebral discs involved in burst-type fractures, typically, do not survive the traumatic event and will degenerate irrevocably.

PURPOSE

To evaluate whether intervertebral discs, located adjacent to traumatic burst fractures and treated with pedicle screw fixation and direct end-plate restoration, survive the traumatic event or irrevocably progress to severe disc degeneration.

STUDY DESIGN

Prospective trial.

PATIENT SAMPLE

Twenty adult patients with traumatic burst fractures of the thoracolumbar spine and treated with pedicle screw fixation and direct end-plate reduction were included.

OUTCOME MEASURES

Disc degeneration according to the Pfirrmann classification.

METHODS

Magnetic resonance imaging scans were obtained preoperatively, 1 month after surgery and 1 month after pedicle screw removal 12 to 18 months after index surgery. Degeneration of the intervertebral discs adjacent to the fracture was assessed using the Pfirrmann classification. Grade 1/2/3 was defined as mild-to-moderate degeneration of the intervertebral disc (MDID), whereas Grade 4/5 was defined as severe-to-endstage degeneration of the intervertebral disc (SDID). Repeated measure analysis was performed to detect significant differences between MDID and SDID scores.

RESULTS

A total of 19 patients (38 discs) were fully documented and available for study. All discs showed MDID preoperatively, and while five discs (13%) progressed to SDID at 12 to 18 months posttrauma, the other discs did not show progression of degeneration.

CONCLUSIONS

Intervertebral discs adjacent to traumatic burst fractures treated with pedicle screw instrumentation and direct end-plate restoration do not routinely seem to progress to severe degeneration at 12 to 18 months postinjury.

Nanocrystalline hydroxyapatite facilitates bone apposition to polymethylmethacrylate: histological investigation using a sheep model

Polymethylmethacrylate (PMMA) is the most commonly used bone void filler for vertebral augmentation in osteoporotic fracture. It provides mechanical stability and immediate pain relief; however, PMMA is not osteointegrated and is separated from the surrounding bone tissue by a thin fibrous layer. The aim of this study was to investigate the effect of nanocrystalline hydroxyapatite (HA) on osteointegration of PMMA in a sheep model. A composite material, consisting of PMMA and nanocrystalline HA (70:30, v/v), was implanted in one distal femur, with pure PMMA in the other femur as a control. Three and 6 months after implantation, the distal femora were histologically investigated. All composite implants exhibited a tight junction to the surrounding bone tissue, with minimal bone ingrowth into the outer surface of the implant. In comparison, with use of the control implants, we observed an overall bone resorption around pure PMMA, with fibrous connective tissue encapsulating the implant. These results suggest that nanocrystalline HA enables osteointegration of PMMA in bone tissue, which might alter the biomechanical characteristics of the osteoporotic vertebral body after augmentation.