Calcium Phosphate Cement Group Research Articles

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

BackgroundAs 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. MethodsThirty-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. ResultsSerum 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). ConclusionsThe 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.

Long-term efficacy of balloon-assisted endplate augmentation combined with transforaminal pedicle screw fixation in the treatment of thoracolumbar burst fractures

Objectives: To investigate the long-term efficacy of balloon assisted endplate reduction with vertebral augmentation combined with pedicle screw fixation in the treatment of thoracolumbar burst fractures, and to compare the clinical efficacy of calcium sulfate cement (CSC) and calcium phosphate cement(CPC). Methods: This study is a retrospective cohort study.The clinical data of 39 patients with thoracolumbar burst fractures admitted to Hefei Hospital Affiliated to Anhui Medical University from November 2013 to December 2017 were retrospectively analyzed.All patients were treated with pedicle screw reduction and fixation of the injured vertebra,balloon-assisted reduction of the collapsed endplate of the injured vertebra,and artificial bone vertebral body augmentation,and the follow-up time was >5 years.There were 24 males and 15 females,aged (42.9±13.3) years (range: 29 to 56 years).According to the Frankel spinal nerve dysfunction grading standard, there were 4 cases of grade C, 7 cases of grade D and 28 cases of grade E. There were 21 cases of CSC augmentation(CSC group) and 18 cases of CPC augmentation (CPC group). X-ray and CT were performed at 1 week, 1-, 2-, 5-year after surgery and at the last follow-up, and the imaging indicators were measured, including the injured vertebra anterior edge height ratio,the injured vertebra middle height ratio,the injured vertebra wedge angle,and the sagittal plane Cobb angle. The pain visual analogue scale (VAS) and the Oswestry disability index (ODI) was used for functional evaluation, nervous function was evaluated according to the Frankel spinal nerve dysfunction grading standard.Independent sample t test was used for inter-group comparison, and paired sample t test and repeated measure ANOVA were used for intra-group comparison. Results: All operative procedures were successfully completed, no spinal nerve function damage occurred. The postoperative imaging indexes of the patients were significantly improved compared with those before surgery (all P<0.01). The follow-up time of patients was (6.7±2.8)years (range: 5 to 9 years). Among the 11 patients with symptoms of neurological impairment before surgery, 9 patients completely recovered at the last follow-up, and 2 patients recovered from Frankel grade C to D. There were no significant differences in imaging indexes between the first week after surgery and the last follow-up in the CPC group (all P>0.05), while there were significant differences in imaging indexes between the CSC group and the last follow-up (all P<0.05). CPC group was superior to CSC group in frontal height ratio, middle height ratio, wedge angle variation and sagittal Cobb angle correction loss at 2 year, 5 year after surgery and the last follow-up, with statistical significance (all P<0.05). At the last follow-up, there were no differences in VAS and ODI between the two groups (all P>0.05). After absorption of CSC in the filling area, a hardened zone was formed around the area, and the central cavity remained without bone tissue filling. CPC absorption was very slow, and the CPC group was still filled satisfactorily at the last follow-up. Conclusions: Balloon assisted endplate reduction and vertebral augmentation combined with pedicle screw fixation through the injured vertebra have good long-term efficacy in the treatment of thoracolumbar burst fractures. Compared with CSC, CPC vertebral augmentation can better maintain the shape and spinal sequence of the injured vertebra in the long term, and can effectively reduce the collapse of the space above the injured vertebra.

Application value of calcium phosphate cement in complete cranial reconstructions of microvascular decompression craniectomies

To investigate the application value of calcium phosphate cement (CPC) in repairing cranial defects during microvascular decompression (MVD) surgery via the retrosigmoid approach. A retrospective study was carried out on patients who underwent MVD. According to the two different cranial reconstruction methods, patients were divided into a titanium mesh (TM) group and a CPC group. We compared in the two groups the length of postoperative hospital stay, the incidence of postoperative cerebrospinal fluid (CSF) leakage, the number of patients with suspected postoperative intracranial infection who underwent lumbar puncture, the number of patients with a definitive etiologic diagnosis of intracranial infection, and the imaging evaluation of plastic shape satisfaction. Patients in the CPC group had an average hospital stay of 9.15±2.00 days, shorter than that in the TM group (10.69±2.86 days), P<0.001. In the TM group, the rate of plasticity satisfaction was 70/89 (78.65%), which was significantly lower than that in the CPC group (60/66, 90.91%), P=0.040. Among the patients with a definitive etiologic diagnosis of intracranial infection, there were eight cases in the TM group and one case in the CPC group, and the difference was statistically significant, P=0.049. CPC is another viable alternative for complete cranial reconstructions of microvascular decompression craniectomies. The use of CPC does not increase the incidence of postoperative complications, such as CSF leakage and intracranial infection, and can reduce the average length of hospital stay and the incidence of etiologic diagnosis of intracranial infection. Furthermore, the evaluation of the plastic shape is satisfactory.

Treatment of Critical Size Femoral Bone Defects with Biomimetic Hybrid Scaffolds of 3D Plotted Calcium Phosphate Cement and Mineralized Collagen Matrix.

To treat critical-size bone defects, composite materials and tissue-engineered bone grafts play important roles in bone repair materials. The purpose of this study was to investigate the bone regenerative potential of hybrid scaffolds consisting of macroporous calcium phosphate cement (CPC) and microporous mineralized collagen matrix (MCM). Hybrid scaffolds were synthetized by 3D plotting CPC and then filling with MCM (MCM-CPC group) and implanted into a 5 mm critical size femoral defect in rats. Defects left empty (control group) as well as defects treated with scaffolds made of CPC only (CPC group) and MCM only (MCM group) served as controls. Eight weeks after surgery, micro-computed tomography scans and histological analysis were performed to analyze the newly formed bone, the degree of defect healing and the activity of osteoclasts. Mechanical stability was tested by 3-point-bending of the explanted femora. Compared with the other groups, more newly formed bone was found within MCM-CPC scaffolds. The new bone tissue had a clamp-like structure which was fully connected to the hybrid scaffolds and thereby enhanced the biomechanical strength. Together, the biomimetic hybrid MCM-CPC scaffolds enhanced bone defect healing by improved osseointegration and their differentiated degradation provides spatial effects in the process of critical-bone defect healing.

Comparison of fibula strut and calcium phosphate cement augmentation of the medial buttress in 2-part proximal humerus fractures reconstruction: a biomechanical study.

Augmentation strategies for surgical fixation of proximal humerus fractures (PHF) are available to address their relatively high failure rate. The purpose of this study was to compare two medial-buttress augmentation strategies for PHF fixation. A two-part PHF model with loss of medial buttress was created in 16 synthetic bones. The PHFs were fixed with locking plates and either calcium phosphate cement (CPC) or fibula strut (FS) augmentation. After cadaveric validations, the fixation constructs were subjected to nondestructive axial compression tests, followed by a cyclic test. Construct stiffness and angular displacement of the humerus head were recorded. Humeral head angular displacement was statistically greater in the CPC group than in the FS group at the applied force of 300N and higher (p <0.05). Axial stiffness was statistically greater in the FS fixation group than in the CPC group at initial and final phases of cyclic loading protocol (p <0.05). In an osteoporotic cadaveric model of a 2-part PHF with loss of a medial buttress, locked plate constructs augmented with FS have a higher resistance to varus collapse compared to those augmented with CPC.

Selenium-modified calcium phosphate cement can accelerate bone regeneration of osteoporotic bone defect.

The purpose is to observe whether local administration with selenium (Se) can enhance the efficacy of calcium phosphate cement (CPC) in the treatment of osteoporotic bone defects. Thirty ovariectomized (OVX) rats with two defects were generated and randomly allocated into the following graft study groups: (1) OVX group (n = 10), (2) CPC group (n = 10); and (3) Se-CPC group (n = 10). Then, these selenium-modified calcium phosphate cement (Se-CPC) scaffolds were implanted into the femoral epiphysis bone defect model of OVX rats for 12 weeks. Micro-CT, history, western blot and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis were used to observe the therapeutic effect and to explore the possible mechanism. Micro-CT and histological analysis evaluation showed that the Se-CPC group presented the strongest effect on bone regeneration and bone mineralization when compared with the CPC group and the OVX group. Protein expressions showed that the oxidative stress protein expressions, such as SOD2 and GPX1 of the Se-CPC group, are significantly higher than those of the OVX group and the CPC group, while Se-CPC remarkably reduced the expression of CAT. RT-qPCR analysis showed that the Se-CPC group displayed more OPG than the OVX and CPC groups (p < 0.05), while Se-CPC exhibited less RANKL than the OVX and CPC groups (p < 0.05). Our current study demonstrated that Se-CPC is a scheme for rapid repair of femoral condylar defects, and these effects may be achieved by inhibiting local oxidative stress and through OPG/RANKL signaling pathway.

Bioactive Glass Modified Calcium Phosphate Cement with Improved Bioactive Properties: A Potential Material for Dental Pulp-Capping Approaches

Direct pulp capping (DPC) is one of the treatment plans for deep caries with mechanical pulp exposure that can replace invasive treatments. This study aimed to assess the apatite-forming ability and solubility of a calcium phosphate cement (CPC) modified with bioactive glass (BG) as a potential bioactive material for DPC.Three different biomaterials including CPC, BG, and CPC/BG composite were used in this study. For bioactivity evaluation, specimens were immersed in simulated body fluid (SBF) for 5 time periods (3, 7, 14, 21 and 28 days). The samples were analyzed by SEM, EDS and XRD to confirm the formation of hydroxyapatite. The solubility was calculated by measuring the initial and final mass according to the ISO 6876 specifications.According to the results of this study, SEM observations and XRD analysis revealed higher formation of hydroxyapatite crystals in the CPC/BG Group and also at the shorter time than those in the CPC and BG groups. Concerning solubility, the CPC group showed the most solubility after 7 days and the BG group showed the lowest one. At this time the difference between CPC and BG groups was statistically meaningful (p value=0.003). After 30 days the CPC/BG group exhibited the lowest solubility value. At the day 30, the CPC and BG groups showed significant difference in their solubility (p value=0.04).).Based on the results, addition of BG to CPC improved bioactivity properties of CPC material and did not affect its solubility adversely. The CPC/BG composite seems to be a promising material for DPC. Further in vivo studies are needed to prove its clinical success.

Combined use of calcium phosphate cement, mesenchymal stem cells and platelet-rich plasma for bone regeneration in critical-size defect of the femoral condyle in mini-pigs.

Aim: To investigate the outcome of autologous bone marrow mesenchymal stem cells (BMMSCs) and platelet-rich plasma in combination with calcium phosphate cement (CPC) scaffold to reconstruct femoral critical bone defects in mini-pigs. Materials & methods: Scanning electron microscopy, micro-computed tomography evaluation and quantitative histological assessment were used. Results & conclusion: BMMSCs were attached to the CPC scaffold after 7 days of culture and decreased the residual CPC material in each group at 12 weeks compared with 6 weeks. The newly formed bone area was higher in the CPC+SC+P group than in the CPC group at each time point (all p < 0.05). The strategy of CPC combined with BMMSCs and platelet-rich plasma might be an effective method to repair bone defects.

Guided bone tissue regeneration using a hollow calcium phosphate based implant in a critical size rabbit radius defect

Long bone fractures are common and sometimes difficult to treat. Autologous bone (AB), bovine bone and calcium phosphates are used to stimulate bone growth with varying results. In the present study, a calcium phosphate cement (CPC) that previously showed promising grafting capabilities was evaluated for the first time in a long bone defect. A radius defect of 20 mm was created in 20 rabbits. The defect was filled by either a hollow CPC implant that had been manufactured as a replica of a rabbit radius through indirect 3D printing, or by particulate AB as control. Defect filling and bone formation was evaluated after 12 weeks by combining micro computed tomography (μCT) and scoring of 3D images, together with histomorphometry and histology. The μCT and histomorphometric evaluations showed a similar amount of filling of the defect (combining graft and bone) between the CPC and AB group, but the scoring of 3D images showed that the filling in the CPC group was significantly larger. Histologically the AB graft could not be distinguished from the new bone. The AB treated defects were found to be composed of more bone than the CPC group, including reorganised cancellous and cortical bone. Both the CPC and AB material was associated with new bone formation, also in the middle of the defect, which could result in closing of the otherwise critically sized gap. This study shows the potential for an indirectly 3D printed implant in guided bone regeneration in critically sized long bone defects.

In vivo study of strontium-doped calcium phosphate cement for biological properties

OBJECTIVE To evaluate the biocompatibility and osteogenic effect of new calcium phosphate cement (CPC) in vivo and to provide experimental basis for its further clinical application. METHODS Thirty New Zealand white rabbits were randomly divided into four groups: CPC group, CPC+Bio-Oss group, Bio-Oss group and blank control group. Bone defect models of 6 mm in diameter and 7 mm in depth were made on the lateral condyle of bilateral hind legs of the rabbits. CPC, Bio-Oss and CPC+Bio-Oss mixture were implanted into the bone defect according to the group, and the mass ratio of CPC and Bio-Oss was 4 ∶ 1. The experimental animals were sacrificed the 4th, 12th and 24th week after operation. The tissue around the bone defect was taken for histological evaluation by H&E staining. Bone ingrowth fraction (BIF) was calculated. The expression of BMP-2 and COL-Ⅰ was detected by immunohis- tochemical staining by calculating the mean optical density (MOD) of the positive area the 4th week after operation, and the bone healing of each group was evaluated at different time points. The measurement data were analyzed by one-way ANOVA and LSD test was used for multiple comparison of the differences between the means by SPSS 19.0. P < 0.05 was considered to be statistically significant. RESULTS The results of H&E staining showed that the BIF values of CPC group, CPC + Bio-Oss group and Bio-Oss group were significantly higher than those of blank control group at the same time point (P < 0.01). The BIF values of CPC group were lower than those of Bio-Oss group and CPC + Bio-Oss group (P < 0.01). There was no significant difference between CPC + Bio-Oss group and Bio-Oss group. Immunohistochemical staining showed that the MOD values of BMP-2 and COL-Ⅰ in CPC group were higher than those in blank control group, but lower than those in Bio-Oss group and CPC+Bio-Oss group (P < 0.01). There was no significant difference between BMP-2 and COL-Ⅰ in CPC+Bio-Oss group and Bio-Oss group. CONCLUSION The new calcium phosphate cement has good biocompatibility and can promote early osteogenesis with stable and long-term effect.

Ridge Alterations following Socket Preservation Using a Collagen Membrane in Dogs.

Background The healing process following tooth extraction results in alveolar ridge resorption. The dimensional changes may complicate the subsequent implant procedure. Socket preservation using absorbable collagen membranes or a combination of membranes with calcium phosphate cement (CPC) particles might ensure that the alveolar ridge retains a suitable morphology for implant placement. Objective To evaluate the quality and quantity of new bone regenerated after application of either collagen membranes alone covering the sockets or a combination of membranes with CPC particles added into the sockets in dogs. Materials and Methods. Six dogs were included in this study. The mandibular premolars were extracted. For each hemimandible, three premolar extraction sites were randomly assigned to one of the following treatments: a covering collagen membrane, CPC with a covering collagen membrane, and a socket left empty. Cone-beam computed tomography (CBCT) measurements, polyfluorochrome sequential labeling, and histological assessments were performed to investigate the healing ability and repair processes within a 6-month observation period. Results Buccal bone height in the membrane group was significantly higher than that in the membrane+CPC and blank groups at 4 and 6 months after extraction. The mineral apposition rate over 2-4 months and the alizarin red-stained area in the membrane group were significantly higher than those in the other two groups. Histological analysis after 6 months of healing showed significantly higher amounts of newly formed bone in the membrane group than in the other groups. Conclusion Extraction sites treated with collagen barrier membranes showed better protection than sites not covered with membranes. And the buccal bone wall of the socket was well preserved by collagen membrane without extra CPC materials. Socket preservation using absorbable membranes alone yielded better quality and quantity of regenerated bone inside the socket site.

Loading necrostatin-1 composite bone cement inhibits necroptosis of bone tissue in rabbit.

Bone necrosis after injecting of polymethylmethacrylate (PMMA) bone cement will lead to re-fracture of bone tissue. As a new type of necrosis, there is little research related to the necroptosis of surrounding bone tissue near the bone cement. The purpose of our study was to (i) investigate the presence of necroptosis in vivo and, (ii) established as a new type of bone cement containing PMMA, calcium phosphate cement (CPC) and Necrostatin-1 (Nec-1) to inhibit necroptosis of bone tissue. A total of 12 Japanese rabbits were used to establish the animal model and randomly divided into 4 groups signed as a control group, PMMA group, PMMA–CPC group and PMMA–CPC–Nec-1 group, respectively. We used scanning electron microscope to observe the structure of the samples, used HE staining to detect the necrosis, and used western blotting as well as ELISA test to examine the iconic molecule receptor interacting protein kinase-3 (RIP 3) protein and tumor necrosis factor α (TNF-α). After analyzing the results of our study, we found that the structure in both PMMA bone cement group and composite bone cement group was damaged and there was an evidence of necrosis, but it was absent in control group. Through molecule detection, the RIP 3 protein expression was decreased in PMMA–CPC–Nec-1 (P < 0.05). TNF-α expression was increased in bone cement groups with and without CPC (P < 0.05), but was inhibited in PMMA–CPC–Nec-1 group. We have concluded that the necroptosis could be confirmed in bone tissue necrosis induced by TNF-α after bone cement injection and also could be inhibited by composite bone cement with Nec-1.

Case-control study on self-setting calcium phosphate cement and allograft for Sanders II-IV fractures of calcaneus

To compare clinical results of Sanders II-IV fractures of calcaneus treated by self-setting calcium phosphate cement and allograft with locking reconstruction bone plate internal fixation. From March 2012 to December 2015, 48 patients with Sanders II-IV fractures of calcaneus were treated by open reduction and internal fixation through L-shape incision, bone grafting were performed on reserved bone defect of calcaneal fracture. The patients were divided into self-setting calcium phosphate cement and allograft group according to different materials. Twenty-eight patients in self-setting calcium phosphate cement group, including 23 males and 5 females aged from 22 to 52 years old with an average of (34.46±7.33) years old; 8 cases were type II, 11 cases were type III and 7 cases were type IV according to Sanders classification. Twenty patients in allograft group, including 17 males and 3 females aged from 24 to 55 years old with an average of(36.40±7.93) years old; 6 cases were type II, 7 cases were type III and 9 cases were type IV according to Sanders classification. Postoperative wound complications, Böhler angle before and after operation and 12 months, Maryland functional score were evaluated. All patients obtained bone union, and were followed up from 12 to 42 months with an average of 25 months. There were no statistical significance in Böhler angle and Manyland score before and after operation and 12 months between two groups. Five patients occurred wound complications in allograft group and 2 cases occurred wound complications in self-setting calcium phosphate cement and allograft group. Both of open reduction bone grafting and reconstructive plate internal fixation have good effective results for calcaneal fracture. Compared with allograft, self-setting calcium phosphate cement, which has no rejection response and less complications, has equal effects for calcaneal fracture and deserves to be popularized.

Effect of modified compound calcium phosphate cement on the differentiation and osteogenesis of bone mesenchymal stem cells

BackgroundThe aim of this study is to evaluate the effect of self-invented compound calcium phosphate cement upon the proliferation and osteogenesis of bone mesenchymal stem cells (BMSCs).MethodsFour groups including traditional calcium phosphate cement, modified calcium phosphate cement, modified calcium phosphate cement plus bone morphogenetic protein (BMP), and control groups were established. The cell proliferation curve was delineated by MTT. The activity of BMSCs to synthesize alkaline phosphatase (AKP) was evaluated. The growth and invasion of BMSCs were observed. The expression levels of aggrecan, collagen I, collagen II, AKP, and OSX messenger RNA (mRNA) were measured by using RT-PCR.ResultsCompared with other groups, the BMSCs in the modified calcium phosphate cement group presented with loose microstructure and the BMSCs closely attached to the vector margin. At 7 days after co-culture, the expression of AKP in the modified calcium phosphate cement plus BMP group was significantly upregulated compared with those in other groups. In the modified calcium phosphate cement group, the BMSCs properly proliferated on the surface of bone cement and invaded into the cement space. At 10 days, the expression levels of aggrecan, collagen I, collagen II, AKP, and OSX mRNA in the modified calcium phosphate cement and modified calcium phosphate cement plus BMP groups were significantly upregulated than those in other groups.ConclusionsModified compound calcium phosphate cement possesses excellent biocompatibility and osteogenic induction ability. Loose microstructure and large pore size create a favorable environment for BMSCs proliferation and vascular invasion, as an ideal vector for releasing BMP cytokines to mediate the differentiation and osteogenesis of BMSCs.

Modification of calcium phosphate cement with poly (γ-glutamic acid) and its strontium salt for kyphoplasty application

To meet the requirements of minimally invasive surgical treatments for osteoporotic vertebral compression fracture, various strategies have been proposed to enhance the properties of calcium phosphate cement (CPC). Here, a new strategy was developed by incorporating poly (γ-glutamic acid) (γ-PGA) and its strontium salt into the formulation of alpha tricalcium phosphate (α-TCP)-based CPC. Effects of γ-PGA on the injectability, cohesion, setting times, mechanical compressive strengths and cytocompatibility were systematically studied. Results showed that the injectability, cohesion and setting times were considerably improved by introducing γ-PGA into the CPC. Moreover, after setting for 7days, the compressive strengths increased from 14.6±1.4MPa for pure CPC to 35.3±1.7MPa for CPC with 8.9wt% γ-PGA and further to 61.2±5.4MPa for CPC with 8.9wt% γ-PGA combined with its strontium salt. In vitro osteoblast proliferation tests showed that the group of CPC modified by γ-PGA and its strontium salt had better cytocompatibility than the pure CPC group. All results suggest that optimal properties were obtained for the cement with 8.9wt% γ-PGA added to its solid phases and using strontium salt as the reactive liquid phase, making it as a promising candidate for application in kyphoplasty.

An injectable, biodegradable calcium phosphate cement containing poly lactic-co-glycolic acid as a bone substitute in ex vivo human vertebral compression fracture and rabbit bone defect models

ABSTRACTPurpose/Aim of the study: To evaluate the biomechanical characteristics and biocompatibility of an injectable, biodegradable calcium phosphate cement (CPC) containing poly lactic-co-glycolic acid (PLGA). Materials and methods: A vertebral compression fracture model was established using 20 human cadaveric vertebrae (T11-L3) divided into CPC/PLGA composite versus PMMA groups for biomechanical testing. In addition, 35 New Zealand rabbits were used to evaluate biodegradability and osteoconductive properties of CPC/PLGA using a bone defect model. In vitro cytotoxicity was evaluated by culturing with L929 cells. Results: The CPC/PLGA composite effectively restored vertebral biomechanical properties. Compared with controls, the maximum load and compression strength of the CPC/PLGA group were lower, and stiffness was lower after kyphoplasty (all p <.05). Degradation was much slower in the control CPC compared with CPC/PLGA group. The bone tissue percentage in the CPC/PLGA group (44.9 ± 23.7%) was significantly higher compared with control CPC group (25.7 ± 10.9%) (p <.05). The viability of cells cultured on CPC/PLGA was greater than 70% compared with the blanks. Conclusions: Our biodegradable CPC/PLGA composite showed good biomechanical properties, cytocompatibility, and osteoconductivity and may represent an ideal bone substitute for future applications.

An experimental study on a slow-release complex with rifampicin-polylactic-co-glycolic acid-calcium phosphate cement

To prepare the slow-release complex with rifampicin (RFP)-polylactic-co-glycolic acid (PLGA)-calcium phosphate cement (CPC) (RFP-PLGA-CPC complex), and to study its physical and chemical properties and drug release properties in vitro. The emulsification-solvent evaporation method was adopted to prepare rifampicin polylactic acid-glycolic acid (RFP-PLGA) slow-release microspheres, which were divided into 3 groups: a calcium phosphate bone cement group (CPC group), a CPC embedded with RFP group (RFP-CPC group), and a PLGA slow-release microspheres carrying RFP and the self-curing CPC group (RFP- PLGA-CPC complex group). The solidification time and porosity of materials were determined. The drug release experiments in vitro were carried out to observe the compressive strength, the change of section morphology before and after drug release. The CPC group showed the shortest solidification time, while the RFP-PLGA-CPC complex group had the longest one. There was statistical difference in the porosity between the CPC group and the RFP-CPC group (P<0.05); Compared to the RFP-PLGA-CPC complex group, the porosity in the CPC group and the RFP-CPC group were significantly changed (both P<0.01). There was significant difference in the compressive strength between the RFP- PLGA-CPC complex group and the CPC group (P<0.01), while there was significant difference in the compressive strength between the RFP-CPC group and the CPC group (3 days: P<0.05; 30 and 60 days: P<0.01). The change of the compressive strength in the CPC was not significant in the whole process of degradation. The sizes of PLGA microspheres were uniform, with the particle size between 100-150 μm. The microspheres were spheres or spheroids, and their surface was smooth without the attached impurities. There was no significant change in the section gap in the CPC group after soaking for 3 to 60 days. The microstructure change in the RFP-CPC group was small, and the cross section was formed by small particles. The pores of section in the RFP-PLGA-CPC complex group increased obviously, and PLGA microspheres gradually disappeared until the 60th day when there were only empty cavities left. The RFP-PLGA-CPC complex group had no obvious drugs sudden release, and the cumulative drug release rate was nearly 95% in the 60 days. The linear fitting was conducted for the drug release behavior of the complex, which was in accordance with zero order kinetics equation F=0.168×t. The porosity of RFP-PLGA-CPC complex is significantly higher than that of CPC, and it can keep slow release of the effective anti-tuberculosis drugs and maintain a certain mechanical strength for a long time.

The promotion of bone tissue regeneration by BMP2-derived peptide P24-loaded calcium phosphate cement microspheres

Calcium phosphate cement (CPC) scaffolds have been widely used as bone graft substitutes, but their clinical application is restricted by the undesirable osteoinductivity and slow degradability. We developed new CPC microspheres loaded with bone morphogenetic protein-2 (BMP-2)-derived peptide P24 (P24/CPC). The BMP2-derived peptide P24 was evenly pasted with CPC microspheres, which maintained the bioactivity of BMP-2. We evaluated the effect of the P24/CPC microspheres on osteogenesis and examined the underlying mechanism in vitro and in vivo. The in vitro studies showed that the bioactivity of P24 was preserved in the P24/CPC microspheres and the P24 release duration lasted up to 39 days. The P24/CPC microspheres with different proportions of P24 (2% and 4%) induced high proliferation of bone marrow stromal cells (BMSCs) and well supported cell adhesion on the sphere surfaces. Furthermore, the cells exhibited higher alkaline phosphatase activity and higher expression of osteogenic-specific genes (OCN and Runx2) in 4% P24/CPC than in the CPC and control groups (P<0.05). Therefore, these findings indicated the enhanced osteoblastic differentiation of BMSCs on P24/CPC microspheres. In vivo osteoinductive studies revealed that the degrees of ectopic osteogenesis in the dorsal muscle pocket of rat were significantly higher in the P24/CPC microspheres than in the CPC microspheres. Finally, the CPC or P24/CPC microspheres were implanted into rabbit femoral condyle defects and P24/CPC serial groups were observed for 4, 8, and 12 weeks. Computed tomography (CT) and histological and histomorphological studies proved that P24/CPC microspheres were biocompatible, bioabsorbable, and osteoinductive. In conclusion, this study demonstrated that P24/CPC microspheres can enhance osteogenesis in vitro and promote bone regeneration in vivo. Furthermore, our results confirmed that BMP2-derived peptide P24 can have a beneficial effect on the bone-generating properties of CPC microspheres, suggesting that P24/CPC microspheres are strong potential bone graft substitutes in bone tissue engineering.

Local Application of Strontium in a Calcium Phosphate Cement System Accelerates Healing of Soft Tissue Tendon Grafts in Anterior Cruciate Ligament Reconstruction

Background: Healing of soft tissue tendon grafts within the bone tunnel in anterior cruciate ligament (ACL) reconstruction is known to be slower than that of bone–patellar tendon–bone grafts. There are attempts to accelerate healing of the graft within the bone tunnel. One of the methods is the use of strontium-enriched calcium phosphate cement (Sr-CPC). Early results in animal studies have been encouraging, although it is not known whether the accelerated healing was solely caused by the effect of strontium within the cement or by the calcium phosphate cement (CPC) itself. Hypothesis: There would be differences between Sr-CPC and conventional CPC in terms of the effect on healing of soft tissue tendon grafts within the bone tunnels in ACL reconstruction. Study Design: Controlled laboratory study. Methods: A total of 30 single-bundle ACL reconstruction procedures were performed in 15 rabbits with the use of an Achilles tendon allograft. The graft on the left limb was coated with Sr-CPC, while that on the right limb was coated with CPC. Three animals each were sacrificed for histological and histomorphometric analyses at 3, 6, 9, 12, and 24 weeks after surgery. Results: In the Sr-CPC group, early formation of Sharpey fibers was present at 6 weeks after surgery, while early remodeling of a graft-fibrocartilage-bone junction was noted at 12 weeks. In the CPC group, early formation of Sharpey fibers was only found at 9 to 12 weeks after surgery. At 24 weeks, a direct enthesis was found in both groups. According to the histomorphometric score, graft healing in the Sr-CPC group took place 3 weeks faster than that in the CPC group at and before 12 weeks; however, there was no difference between the groups at 24 weeks. Conclusion: The local application of strontium in a CPC system leads to accelerated graft healing within the bone tunnels. Clinical Relevance: The use of Sr-CPC to enhance graft-bone healing may improve the clinical results of ACL reconstruction using soft tissue tendon grafts.

Comparison of three calcium phosphate bone graft substitutes from biomechanical, histological, and crystallographic perspectives using a rat posterolateral lumbar fusion model

This study evaluated the effectiveness of three calcium phosphate bone graft substitutes with different chemical compositions on spinal fusion using a rat posterolateral lumbar fusion model. Specifically, two recently developed non-dispersive tetracalcium phosphate/dicalcium phosphate anhydrous-based calcium phosphate cements (CPCs), namely a CPC consisting of equimolar amounts of the two compounds (nd-CPC) and a CPC consisting of a two-fold greater amount of dicalcium phosphate anhydrous (DCP-rich CPC), were compared with a commercial calcium phosphate bone graft (c-CPG) consisting of hydroxyapatite (60%) and β-tricalcium phosphate (40%). Single-level posterolateral lumbar fusion was performed at the L4–L5 vertebrae in fifteen adult rats (n=5 for each group). Spinal fusion was evaluated with radiographs, manual palpation, mechanical testing, micro-CT, and histology 8weeks post-surgery. In particular, the crystallographic phases in the three substitutes were identified before and 8weeks after their implantation. Manual palpation revealed stable constructs in nearly all of the spine specimens. The stiffness and bending load of fused spines in the two CPC groups were comparable to those in the c-CPG group. The radiographs specifically revealed implant resorption and bone remodeling in the DCP-rich CPC group. Analysis of 3D micro-CT images revealed that the bone volume ratio in the DCP-rich CPC group was significantly greater than those in the nd-CPC and c-CPG groups. Histology showed that the DCP-rich CPC group exhibited the highest degree of bone regeneration and osseointegration. Notably, DCP-rich CPC led to a pronounced phase transformation, generating the greatest amount of poorly crystalline apatite among the three groups, which together with adequate resorption may explain the aforementioned positive findings. We therefore conclude that of the bone graft substitutes considered, DCP-rich CPC has the greatest potential to be used in spinal fusion.