Temperature elevation during simulated polymethylmethacrylate (PMMA) cranioplasty in a cadaver model

Cranial Reconstruction for Infiltrative Meningioma Using 68Ga-DOTATATE Positron Emission Tomography/Computed Tomography and Individual Patient Solutions CaseDesigner®: A Case Series

BACKGROUND AND OBJECTIVES

Meningioma with bone involvement presents challenges for complete resection and cranial reconstruction. 68Ga-dodecanetetreaacetic acid tyrosine-3-octreotide (DOTATATE) positron emission tomography (PET)/computed tomography (CT) has emerged as an excellent modality for localizing invasive meningiomas because of molecular interaction with somatostatin receptor-2. We present a novel technique to design 3-dimensional-printed artificial cranioplasty, using combined fine-slice CT, MRI, and 68Ga-DOTATATE PET/CT with Individual Patient Solutions (IPS) CaseDesigner® software. This study's objective was to generate proof-of-concept work for a novel artificial cranioplasty protocol that combines customized cranial implant software and DOTATATE PET/CT.

METHODS

Three patients with invasive bone meningiomas were retrospectively identified. For each patient, the proposed protocol combines CT, MRI, and 68Ga-DOTATATE PET/CT imaging to generate a 3-dimensional cranial reconstruction within the Karl Leibinger Surgical (KLS) Martin-IPS CaseDesigner® software. Subsequently, the virtual rendering is used to manufacture a customized polyetheretherketone (PEEK) implant, along with a guiding component, which ensures precise delineation of surgical borders before craniectomy. Finally, cranioplasty with the customized implant is performed using standard techniques.

RESULTS

The described preoperative cranioplasty design protocol was performed for each patient. Tumor invasion was visualized using 68Ga-DOTATATE PET/CT. Patient 1 presented with a recurrent right frontal meningioma with invasion into anterior skull base. In this case, IPS CaseDesigner® was used to create a mirror image PEEK implant for the left orbit and affected cranium. Patients 2 and 3 had intraosseous meningiomas invading the frontal bone; customized PEEK implants were tailored to the side of the planned craniectomy for both patients and were successfully placed without complication. Postoperatively, all patients remained neurologically intact and were discharged without complications. In all patients, the PEEK implants exhibited appropriate cranial continuity and integrity.

CONCLUSION

68Ga-DOTATATE PET/CT has high sensitivity and specificity for detecting meningiomas during preoperative planning, particularly when the tumor involves bone. IPS CaseDesigner® demonstrates excellent utility for planning and constructing customized cranioplasties tailored to each patient for skull reconstruction.

Performance evolution of the Nano Boron nitride enhanced bone cement composites

Bone cement is a research hotspot and has been partially applied in the field of bone repair thanks to the good mechanical, physical and antibacterial properties. However, the easy wear and high temperature during curing characteristics would cause surrounding tissue necrosis, which seriously limits the wider application to some extent. In this work, the hexagonal boron nitride (h-BN) nano flakes were optimized to enhance the bone cement matrix (PMMA) via mechanical doping. The doping of h-BN into PMMA results in an improved mechanical (bending stress increased by 26%), thermal-conductivity (increased by 175% with the loading of 20 wt%), wear-resistance properties, in addition, the h-BN has no significant impact on cell activity. What's more, the co-modification of PMMA with h-BN and Vancomycin (Va) endows the bone cement composites with more persistent drug release characteristics. This comprehensive performance evolution evaluation provides a reference for the innovative application of modified bone cement.

Magnesium-Based Composite Calcium Phosphate Cement Promotes Osteogenesis and Angiogenesis for Minipig Vertebral Defect Regeneration

Calcium phosphate cement (CPC) is an injectable bone cement with excellent biocompatibility, widely used for filling bone defects of various shapes. However, its slow degradation, insufficient mechanical strength, and poor osteoinductivity limit its further clinical applications. In this study, we developed a novel composite magnesium-based calcium phosphate cement by integrating magnesium microspheres into PLGA fibers obtained through wet spinning and incorporating these fibers into CPC. The inclusion of magnesium-based PLGA fibers enhanced the compressive strength and degradation rate of CPC, with the degradation rate of the magnesium microspheres being controllable to allow for the sustained release of magnesium ions. In vitro experiments showed that magnesium-based CPC enhanced the proliferation and migration of MC3T3-E1 and HUVECs. Additionally, the magnesium-based composite CPC not only enhanced osteogenic differentiation of MC3T3-E1 cells but also promoted angiogenesis in HUVECs. In vivo experiments using a vertebral bone defect model in Bama miniature pigs showed that the magnesium-based composite CPC significantly increased new bone formation. Additionally, compared to the CPC group, this composite exhibited significantly higher levels of osteogenic and angiogenic markers, with no inflammation or necrosis observed in the heart, liver, or kidneys, indicating good biocompatibility. These results suggest that magnesium-based composite CPC, with its superior compressive strength, biodegradability, and ability to promote vascularized bone regeneration, holds promise as a minimally invasive injectable material for bone regeneration.

Radiopaque and Biocompatible PMMA Bone Cement Triggered by Nano Tantalum Carbide and Its Osteogenic Performance

Poly(methyl methacrylate) (PMMA) bone cements have been widely used in orthopedics; thanks to their excellent mechanical properties, biocompatibility, and chemical stability. Barium sulfate and zirconia are usually added into PMMA bone cement to enhance the X-ray radiopacity, while the mechanical strength, radiopacity, and biocompatibility are not well improved. In this study, an insoluble and corrosion-resistant ceramic, tantalum carbide (TaC), was added into the PMMA bone cement as radiopacifies, significantly improving the mechanical, radiopaque, biocompatibility, and osteogenic performance of bone cement. The TaC-PMMA bone cement with varied TaC contents exhibits compressive strength over 100 MPa, higher than that of the commercial 30% BaSO4-PMMA bone cement. Intriguingly, when the TaC content reaches 20%, the radiopacity is equivalent to the commercial bone cement with 30% of BaSO4 in PMMA. The cytotoxicity and osteogenic performance indicate that the incorporation of TaC not only enhances the osteogenic properties of PMMA but also does not reduce cell viability. This study suggests that TaC could be a superior and multifunctional radio-pacifier for PMMA bone cement, offering a promising avenue for improving patient outcomes in orthopedic applications.

Demonstration of Cosmetic Improvement After Cranioplasty Using a Personalized 3D-Printed Mold for Creating Polymethylmethacrylate Implants With a Simplified Process

BACKGROUND

Although personalized polymethylmethacrylate (PMMA) implant production molds for cranioplasty are costly and time-consuming, they allow for better-quality implants. The researchers quantitatively tested the contribution of simplified, low-cost techniques to cosmetic improvement.

METHODS

PMMA prosthesis was placed in a 25-year-old male patient due to osteolysis in the bone flap removed after decompression surgery. A single-sided mold was three-dimensional (3D) printed before the surgery, and the prosthesis was produced during the surgery. In addition, the change in cranial asymmetry was evaluated using a 3D surface scanner after surgery.

RESULTS

The mold took half an hour to design and 5 hours to print. The mold cost about 2 dollars. The root means square (RMS) value measured to determine cranial asymmetry decreased from 5.4 mm to 2.8 mm postoperatively. The patient stated that he was pretty satisfied with the cosmetic result.

CONCLUSIONS

Simple design techniques developed can offer low-cost, fast-design alternative solutions with satisfactory cosmetic results for low-income countries and patients.

Incorporating the Antioxidant Fullerenol into Calcium Phosphate Bone Cements Increases Cellular Osteogenesis without Compromising Physical Cement Characteristics

Herein, fullerenol (Ful), a highly water-soluble derivative of C60 fullerene with demonstrated antioxidant activity, is incorporated into calcium phosphate cements (CPCs) to enhance their osteogenic ability. CPCs with added carboxymethyl cellulose/gelatin (CMC/Gel) are doped with biocompatible Ful particles at concentrations of 0.02, 0.04, and 0.1 wt v%-1 and evaluated for Ful-mediated mechanical performance, antioxidant activity, and in vitro cellular osteogenesis. CMC/gel cements with the highest Ful concentration decrease setting times due to increased hydrogen bonding from Ful's hydroxyl groups. In vitro studies of reactive oxygen species (ROS) scavenging with CMC/gel cements demonstrate potent antioxidant activity with Ful incorporation and cement scavenging capacity is highest for 0.02 and 0.04 wt v%-1 Ful. In vitro cytotoxicity studies reveal that 0.02 and 0.04 wt v%-1 Ful cements also protect cellular viability. Finally, increase of alkaline phosphatase (ALP) activity and expression of runt-related transcription factor 2 (Runx2) in MC3T3-E1 pre-osteoblast cells treated with low-dose Ful cements demonstrate Ful-mediated osteogenic differentiation. These results strongly indicate that the osteogenic abilities of Ful-loaded cements are correlated with their antioxidant activity levels. Overall, this study demonstrates exciting potential of Fullerenol as an antioxidant and proosteogenic additive for improving the performance of calcium phosphate cements in bone reconstruction procedures.

New Research Progress of Modified Bone Cement Applied to Vertebroplasty

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

The Use of 3D Printed Models for Surgical Simulation of Cranioplasty in Craniosynostosis as Training and Education

BACKGROUND

The advance in imaging techniques is useful for 3D models and printing leading to a real revolution in many surgical specialties, in particular, neurosurgery.

METHODS

We report on a clinical study on the use of 3D printed models to perform cranioplasty in patients with craniosynostosis. The participants were recruited from various medical institutions and were divided into two groups: Group A (n = 5) received traditional surgical education (including cadaveric specimens) but without using 3D printed models, while Group B (n = 5) received training using 3D printed models.

RESULTS

Group B surgeons had the opportunity to plan different techniques and to simulate the cranioplasty. Group B surgeons reported that models provided a realistic and controlled environment for practicing surgical techniques, allowed for repetitive practice, and helped in visualizing the anatomy and pathology of craniosynostosis.

CONCLUSION

3D printed models can provide a realistic and controlled environment for neurosurgeons to develop their surgical skills in a safe and efficient manner. The ability to practice on 3D printed models before performing the actual surgery on patients may potentially improve the surgeons' confidence and competence in performing complex craniosynostosis surgeries.

Characterisation of Selected Materials in Medical Applications

Tissue engineering is an interdisciplinary field of science that has developed very intensively in recent years. The first part of this review describes materials with medical and dental applications from the following groups: metals, polymers, ceramics, and composites. Both positive and negative sides of their application are presented from the point of view of medical application and mechanical properties. A variety of techniques for the manufacture of biomedical components are presented in this review. The main focus of this work is on additive manufacturing and 3D printing, as these modern techniques have been evaluated to be the best methods for the manufacture of medical and dental devices. The second part presents devices for skull bone reconstruction. The materials from which they are made and the possibilities offered by 3D printing in this field are also described. The last part concerns dental transitional implants (scaffolds) for guided bone regeneration, focusing on polylactide-hydroxyapatite nanocomposite due to its unique properties. This section summarises the current knowledge of scaffolds, focusing on the material, mechanical and biological requirements, the effects of these devices on the human body, and their great potential for applications.

A new technique for preparing cadavers using PMMA: Rat and mouse example

BACKGROUND

Polymethyl methacrylate is a member of the acrylic polymer family with superior optical properties. It is used in dentistry, hospital incubators, lenses, and various surgical fields, especially orthopedics. In this preliminary study, we aimed to prepare cadavers using the industrial form of polymethyl methacrylate.

METHODS

The new technique consists of fixation, washing, purification, impregnation, and polymerization. For the study, two whole rat bodies, two rat front legs and two rat hind legs, one half rat body, two whole mouse bodies, and all internal organs were used. Wistar albino rats and BALB/c mice were used. After the cadaver samples were fixed and washed, they were passed through an alcohol series starting from 50%, completing the purification process. In the next step, a solution was prepared by mixing 100 ml of Thinner into 1000 ml of a mixture containing styrene, methyl methacrylate, and Co(II)2-ethyl hexanoate. The samples were immersed in the solution under negative pressure (from 10 mmHg to 400 mmHg), allowing the samples to absorb the solution thoroughly. They were then treated with methyl ethyl ketone peroxide and the polymerization step was terminated.

RESULTS

The cadaver samples obtained using polymer were hard, they maintained the given shape, and showed a relatively transparent quality. The production of these materials took 35 days, excluding fixation. The tissue samples were odorless in the process after polymerization. Also, there was no decay in the samples after the production stage and they could be stored under room conditions.

CONCLUSION

This study determined that cadavers could be prepared using polymethyl methacrylate and methyl ethyl ketone peroxide. The polymer used here cost about $5. The cadavers can be safely exhibited in room conditions for five years without requiring special conditions like pools or cold storage. Further research should compare this technique with the plastination technique in terms of texture, color, weight, application time, and cost.

Biomechanical Evaluation of Patient-Specific Polymethylmethacrylate Cranial Implants for Virtual Surgical Planning: An In-Vitro Study

Cranioplasty with freehand-molded polymethylmethacrylate implants is based on decades of experience and is still frequently used in clinical practice. However, data confirming the fracture toughness and standard biomechanical tests are rare. This study aimed to determine the amount of force that could be applied to virtually planned, template-molded, patient-specific implants (n = 10) with an implant thickness of 3 mm, used in the treatment of a temporoparietal skull defect (91.87 cm2), until the implant cracks and finally breaks. Furthermore, the influence of the weight and porosity of the implant on its force resistance was investigated. The primary outcome showed that a high force was required to break the implant (mean and standard deviation 1484.6 ± 167.7 N), and this was very strongly correlated with implant weight (Pearson’s correlation coefficient 0.97; p < 0.001). Secondary outcomes were force application at the implant’s first, second, and third crack. Only a moderate correlation could be found between fracture force and the volume of porosities (Pearson’s correlation coefficient 0.59; p = 0.073). The present study demonstrates that an implant thickness of 3 mm for a temporoparietal skull defect can withstand sufficient force to protect the brain. Greater implant weight and, thus, higher material content increases thickness, resulting in more resistance. Porosities that occur during the described workflow do not seem to reduce resistance. Therefore, precise knowledge of the fracture force of polymethylmethacrylate cranial implants provides insight into brain injury prevention and serves as a reference for the virtual design process.

Customized cost-effective polymethylmethacrylate cranioplasty: a cosmetic comparison with other low-cost methods of cranioplasty

BACKGROUND

Intraoperative hand-moulded cranioplasty and polymethylmethacrylate (PMMA) prostheses made from bone impressions are economical but the cosmetic results are less than satisfactory. Commercially available customized prostheses perform better but are prohibitively expensive. We evaluate the performance of a locally developed, low-cost customized PMMA cranioplasty prosthesis.

OBJECTIVE

To compare the cosmetic outcome of 3 types of PMMA cranioplasty as well as with objective measurements on postoperative CT scans METHODS: This study includes 70 patients who underwent cranioplasty between March 2016 and June 2020. In this period, patients had their cranioplasty prostheses made by intra-operative hand moulding (HM), by using the removed bone as a template and making a bone impression (BI) or by 3D printing the prosthesis based on a CT scan. Cosmetic outcomes were assessed by the patient and the operating surgeon on an 8-point scale. The degree of measured anthropometric asymmetry was measured on a postoperative CT scan and correlated with the cosmetic outcome.

RESULTS

Our locally produced 3D-printed cranioplasty prostheses showed a statistically better performance in cosmetic scores when compared to the HM and BI (p value < 0.001). CT anthropometric measurements significantly correlated with cosmetic outcome (p value 0.01) CONCLUSION: Our 3D cranioplasty prostheses had better cosmetic outcomes than HM and BI prostheses, and our technique is able to produce them at 10% of the cost of the currently available commercial customized prostheses.

Low-Cost Customized Cranioplasty with Polymethyl Methacrylate Using 3D Printer Generated Mold: An Institutional Experience and Review of Literature

Background Cranioplasty is performed to repair skull defects and to restore normal skull anatomy. Optimal reconstruction remains a topic of debate. Autologous bone flap is the standard option but it may not be available due to traumatic bone fractures, bone infection, and resorption. In this article, the authors presented their experience with prefabrication of precise and low-cost polymethyl methacrylate (PMMA) mold using three-dimensional (3D) digital printing.

Materials and Methods A total of 30 patients underwent cranioplasty between March 2017 and September 2019 at Sawai Man Singh Medical College Jaipur, India. Preoperative data included diagnosis for which decompressive craniectomy was done and Glasgow coma scale score. Intraoperative data included operating time. Postoperative data included cosmetic outcome in the form of cranial contour and margins, complications such as infection, seroma, implant failure, wound dehiscence, and hematoma.

Results Patient age at cranioplasty ranged from 12 to 63 years with a mean age of 36.7 years. The mean operating time was 151.6 minutes (range 130–190 minutes). The mean follow-up period was 8 months (range 6–13 months). Postoperative wound dehiscence developed in one case (3.3%). Cranial contour and approximation of the margins were excellent and aesthetic appearance improved in all patients.

Conclusion Low-cost PMMA implant made by digital 3D printer mold is associated with reconstruction of the deformed skull contour giving satisfactory results to the patient and his family members, at a low cost compared with other commercially available implants. This technique could be a breakthrough in cranioplasty.

Interventional Techniques for Bone and Musculoskeletal Soft Tissue Tumors: Current Practices and Future Directions - Part II. Stabilization

Percutaneous image-guided oncologic interventions have rapidly evolved over the last two decades as an independent strategy or used within a first-, second-, or even third-line strategy in the treatment of musculoskeletal (MSK) tumors. Abundant mostly nonrandomized publications have described the safety, efficacy, and reproducibility of implementing percutaneous therapies both with curative and palliative intent. In this article, we continue to share our experience in bone and MSK soft tissue interventions focusing on stabilization and combined ablation and stabilization. We propose a pathway and explore future directions of image-guided interventional oncology related to skeletal disease. We reflect on the advantages and limitations of each technique and offer guidance and pearls to improve outcomes. Representing patterns from our practices, we demonstrate the role of collaborative working within a multidisciplinary team, ideally within a dedicated tumor treatment center, to deliver patient-specific therapy plans that are value based and favored by patients when given the choice.

A systematic review of cranioplasty material toxicity in human subjects

PURPOSE

Local and systemic toxic reactions to implanted materials can result in morbidities. However, little is reported about cranioplasty implants. Therefore, we performed a systematic review on the toxicity of different materials used for cranioplasty implants.

MATERIALS AND METHODS

A systematic search was conducted by browsing the Pubmed, Embase, and Cochrane Library databases. All human studies that identified toxic (aseptic) reactions to any types of material used as cranioplasty implants or onplants, published up to January 1, 2019, were included in the review.

RESULTS

Nineteen studies were identified. Collectively, 36 patients endured some type of toxic reaction to an implanted material. Eleven studies presented several types of toxicity for PMMA cranioplasties in several tissue types. One article highlighted the risk of neurotoxicity for PMMA cranioplasty. Three articles presented toxic reactions to calcium phosphate and titanium implants. Three additional articles presented toxic reactions to PEEK, polypropylene-polyester, and polyethylene.

CONCLUSION

All materials currently used for cranioplasty showed occasional toxicity and morbidities. Therefore, none can be considered completely biologically inert. We found that aseptic inflammatory reactions have been underreported in the literature due to a high incidence of infections with questionable evidence.

Improved Bone Regeneration in Rabbit Bone Defects Using 3D Printed Composite Scaffolds Functionalized with Osteoinductive Factors

Large critical size bone defects are complicated to treat, and in many cases, autografts become a challenge due to size and availability. In such situations, a synthetic bone implant that can be patient-specifically designed and fabricated with control over parameters such as porosity, rigidity, and osteogenic cues can act as a potential synthetic bone substitute. In this study, we produced photocuring composite resins with poly(trimethylene carbonate) containing high ratios of bioactive ceramics and printed porous 3D composite scaffolds to be used as bone grafts. To enhance the overall surface area available for cell infiltration, the scaffolds were also filled with a macroporous cryogel. Furthermore, the scaffolds were functionalized with osteoactive factors: bone morphogenetic protein and zoledronic acid. The scaffolds were evaluated in vitro for biocompatibility and for functionality in vivo in critical bone defects (∼8 mm) in two clinically relevant rabbit models. These studies included a smaller study in rabbit tibia and a larger study in the rabbit cranium. It was observed that the bioactive molecule-functionalized 3D printed porous composite scaffolds provide an excellent conductive surface inducing higher bone formation and improved defect healing in both critical size long bones and cranial defects. Our findings provide strong evidence in favor of these composites as next generation synthetic bone substitutes.

Acrylic Bone Cements Modified with Graphene Oxide: Mechanical, Physical, and Antibacterial Properties

Bacterial infections are a common complication after total joint replacements (TJRs), the treatment of which is usually based on the application of antibiotic-loaded cements; however, owing to the increase in antibiotic-resistant microorganisms, the possibility of studying new antibacterial agents in acrylic bone cements (ABCs) is open. In this study, the antibacterial effect of formulations of ABCs loaded with graphene oxide (GO) between 0 and 0.5 wt.% was evaluated against Gram-positive bacteria: Bacillus cereus and Staphylococcus aureus, and Gram-negative ones: Salmonella enterica and Escherichia coli. It was found that the effect of GO was dependent on the concentration and type of bacteria: GO loadings ≥0.2 wt.% presented total inhibition of Gram-negative bacteria, while GO loadings ≥0.3 wt.% was necessary to achieve the same effect with Gram-positives bacteria. Additionally, the evaluation of some physical and mechanical properties showed that the presence of GO in cement formulations increased wettability by 17%, reduced maximum temperature during polymerization by 19%, increased setting time by 40%, and increased compressive and flexural mechanical properties by up to 17%, all of which are desirable behaviors in ABCs. The formulation of ABC loading with 0.3 wt.% GO showed great potential for use as a bone cement with antibacterial properties.

Low-Cost Customized Cranioplasty with Polymethyl Methacrylate Using 3D Printer Generated Mold: An Institutional Experience and Review of Literature

Background Cranioplasty is performed to repair skull defects and to restore normal skull anatomy. Optimal reconstruction remains a topic of debate. Autologous bone flap is the standard option but it may not be available due to traumatic bone fractures, bone infection, and resorption. The authors present their experience with prefabrication of precise and low-cost polymethyl methacrylate (PMMA) mold using three-dimensional (3D) digital printing.

Methods A total of 30 patients underwent cranioplasty between March 2017 and September 2019 at Sawai Man Singh Medical College Jaipur, India. Preoperative data included diagnosis for which decompressive craniectomy was done and Glasgow coma scale score was observed. Intraoperative data included operating time. Postoperative data included cosmetic outcome in the form of cranial contour and margins, complications such as infection, seroma, implant failure, wound dehiscence, and hematoma.

Results Patient age at cranioplasty ranged from 12 to 63 years with a mean age of 36.7 years. The mean operating time was 151.6 minutes (range 130–190 minutes). The mean follow-up period was 8 months (range 6–13 months). Postoperative wound dehiscence developed in one case (3.3%). Cranial contour and approximation of the margins were excellent and aesthetic appearance improved in all patients.

Conclusion Low-cost PMMA implant made by digital 3D printer mold is associated with reconstruction of the deformed skull contour giving satisfactory results to the patient and his family members, at a low cost compared with other commercially available implants. This technique could be a breakthrough in cranioplasty.

Biomechanical strength comparison of pedicle screw augmentation using poly-dicalcium phosphate dihydrate (P-DCPD) and polymethylmethacrylate (PMMA) cements

STUDY DESIGN

A basic science, hypothesis-driven experimental study of the biomechanics of two bone cements in their ability to augment pedicle screws in bone foam.

OBJECTIVE

The purpose of our study was to compare the pullout and torque resistance of conventional pedicle screws (CPS) augmented with either polymethylmethacrylate (PMMA) or poly-dicalcium phosphate dihydrate (P-DCPD) cement in polyurethane foam blocks mimicking osteoporotic bone. P-DCPD cement has attractive safety characteristics such as non-exothermic curing and drug-eluting capacity. PMMA cement lacks these safety features yet is the current standard in pedicle screw augmentation.

METHODS

Standardized low-density polyurethane open-cell foam blocks were instrumented with conventional pedicle screws and categorized into three groups of six each. Group 1 was the control group and no cement was used. Groups 2 and 3 were augmented with PMMA and P-DCPD, respectively. An Instron machine applied an axial load to failure at a rate of 2 mm/min for 3 min and a torsional load to failure at a rate of 1°/s. Failure was defined by an evident drop in the load after maximum value.

RESULTS

Maximal pullout load for PMMA and P-DCPD was significantly greater than control (p < 0.0001). Interestingly, there was no significant difference in the pullout load to failure for the PMMA and P-DCPD groups. Analysis showed significant difference in torsional resistance between PMMA and P-DCPD, with PMMA having greater resistance (p = 0.00436).

CONCLUSIONS

No difference was observed between PMMA and P-DCPD in pullout load to failure conducted in low-density open-cell, rigid foam blocks. Although a significant difference did exist in our torque analysis, the clinical significance of such a load on a native spine is questionable. Further investigation is warranted for this promising compound that seems to be comparable in pullout resistance to PMMA and offers attractive safety features.

LEVEL OF EVIDENCE

Basic science, not applicable.

Classification of the Residual Cranial Defects and Selection of Reconstruction Materials

The cranial defects are complex in nature and are due to various causes. Therefore, there is a need for a common term of reference to these defects. This requirement stood as a prime reason for proposing a classification system for cranial defects. The classification is based on 2 decades of experience in cranioplasty. This efficient and simple way of representation would fill the existing lacunae for a systematic communication on cranial defects. Over the ages the evolution of reconstruction and grafting had undergone a massive progress. Therefore, it is essential to enumerate all available graft and bio-materials for restoring the cranial defects. The aetiology for these defects, age and sex of the patient, site and size of the defect, associated systemic conditions, cost factor, and operator's choice are the factors that play key role in the selection of the reconstructive material. This article discusses on these factors in cranioplasty. High success rate with excellent function and cosmetic outcome in using a variety of materials, as shared in this article. The advantages of autografts cannot be matched by any existing alloplast. However, in case of larger defects, for a better cosmetic outcome and to reduce the donor site morbidity, alloplasts are the most widely preferred material of choice.

Low-cost customized cranioplasty using a 3D digital printing model: a case report

Background

Cranial defects usually occur after trauma, neurosurgical procedures like decompressive craniotomy, tumour resections, infection and congenital defects. The purpose of cranial vault repair is to protect the underlying brain tissue, to reduce any localized pain and patient anxiety, and improve cranial aesthetics. Cranioplasty is a frequent neurosurgical procedure achieved with the aid of cranial prosthesis made from materials such as: titanium, autologous bone, ceramics and polymers. Prosthesis production is often costly and requires complex intraoperative processes. Implant customized manufacturing for craniopathies allows for a precise and anatomical reconstruction in a shorter operating time compared to other conventional techniques. We present a simple, low-cost method for prosthesis manufacturing that ensures surgical success.

Case presentation

Two patients with cranial defects are presented to describe the three-dimensional (3D) printing technique for cranial reconstruction. A digital prosthesis model is designed and manufactured with the aid of a 3D computed tomography. Both the data of large sized cranial defects and the prosthesis are transferred to a 3D printer to obtain a physical model in poly-lactic acid which is then used in a laboratory to cast the final customised prosthesis in polymethyl methacrylate (PMMA).

Conclusions

A precise compliance of the prosthesis to the osseous defect was achieved. At the 6 month postoperative follow-up no complications were observed i.e. rejection, toxicity, local or systemic infection, and the aesthetic change was very significant and satisfactory. Customized 3D PMMA prosthesis offers cost advantages, a great aesthetic result, reduced operating time and good biocompatibility.

Craniofacial Reconstruction by a Cost-Efficient Template-Based Process Using 3D Printing

Craniofacial defects often result in aesthetic and functional deficits, which affect the patient’s psyche and wellbeing. Patient-specific implants remain the optimal solution, but their use is limited or impractical due to their high costs. This article describes a fast and cost-efficient workflow of in-house manufactured patient-specific implants for craniofacial reconstruction and cranioplasty. As a proof of concept, we present a case of reconstruction of a craniofacial defect with involvement of the supraorbital rim. The following hybrid manufacturing process combines additive manufacturing with silicone molding and an intraoperative, manual fabrication process. A computer-aided design template is 3D printed from thermoplastics by a fused deposition modeling 3D printer and then silicone molded manually. After sterilization of the patient-specific mold, it is used intraoperatively to produce an implant from polymethylmethacrylate. Due to the combination of these 2 straightforward processes, the procedure can be kept very simple, and no advanced equipment is needed, resulting in minimal financial expenses. The whole fabrication of the mold is performed within approximately 2 hours depending on the template’s size and volume. This reliable technique is easy to adopt and suitable for every health facility, especially those with limited financial resources in less privileged countries, enabling many more patients to profit from patient-specific treatment.

Patient-specific polymethylmethacrylate prostheses for secondary reconstruction of large calvarial defects: A retrospective feasibility study of a new intraoperative moulding device for cranioplasty

PURPOSE

The aim of this study was to review a new template-based technique for intraoperative patient-specific cranioplasty manufacturing (PSCM) with polymethylmethacrylate (PMMA) to cover large calvarial defects.

MATERIAL AND METHODS

A polypropylene foil thermoformed on a three-dimensional reprint of the calvarial defect was used as an intraoperative moulding device for PMMA between August 2012 and December 2015. Surgical and radiological data were retrospectively reviewed, and a patient questionnaire was used to assess functional and cosmetic outcome (numeric rating scale, Odom's criteria).

RESULTS

Seventeen patients (mean age 42.2 ± 14.5 years) received PSCM. Operating time averaged 130 ± 34 min, and the approximate blood loss was 293 ± 185 ml. Volumetric analysis revealed a lower implant volume compared to index bone (mean 66.5 vs. 72 cm³, p = 0.513), the mean difference in thickness being the lowest in the posterior parietal and pterional (0.4-0.7 mm) and the highest in the anterior-superior frontal area (1.8 mm). Cosmetic satisfaction averaged 9 ± 1.5, with 70.6% of patients judging the overall result as excellent or good and 29.4% as satisfactory. Mean follow-up was 19.5 ± 13.3 months, with an overall complication rate of 17.6%, including 11.8% surgical site infections (SSIs) and one implant removal.

CONCLUSIONS

Intraoperative PSCM using PMMA moulded on a thermoformed polypropylene foil leads to satisfactory outcomes. It is a safe technique with complication rates comparable but not superior to those of other alloplastic techniques, but the device has considerable production costs.

The feasibility of producing patient-specific acrylic cranioplasty implants with a low-cost 3D printer

OBJECT Commercially available, preformed patient-specific cranioplasty implants are anatomically accurate but costly. Acrylic bone cement is a commonly used alternative. However, the manual shaping of the bone cement is difficult and may not lead to a satisfactory implant in some cases. The object of this study was to determine the feasibility of fabricating molds using a commercial low-cost 3D printer for the purpose of producing patient-specific acrylic cranioplasty implants. METHODS Using data from a high-resolution brain CT scan of a patient with a calvarial defect posthemicraniectomy, a skull phantom and a mold were generated with computer software and fabricated with the 3D printer using the fused deposition modeling method. The mold was used as a template to shape the acrylic implant, which was formed via a polymerization reaction. The resulting implant was fitted to the skull phantom and the cranial index of symmetry was determined. RESULTS The skull phantom and mold were successfully fabricated with the 3D printer. The application of acrylic bone cement to the mold was simple and straightforward. The resulting implant did not require further adjustment or drilling prior to being fitted to the skull phantom. The cranial index of symmetry was 96.2% (the cranial index of symmetry is 100% for a perfectly symmetrical skull). CONCLUSIONS This study showed that it is feasible to produce patient-specific acrylic cranioplasty implants with a low-cost 3D printer. Further studies are required to determine applicability in the clinical setting. This promising technique has the potential to bring personalized medicine to more patients around the world.

The Recent Revolution in the Design and Manufacture of Cranial Implants: Modern Advancements and Future Directions

Large format (i.e., >25 cm) cranioplasty is a challenging procedure not only from a cosmesis standpoint, but also in terms of ensuring that the patient's brain will be well-protected from direct trauma. Until recently, when a patient's own cranial flap was unavailable, these goals were unattainable. Recent advances in implant computer-aided design and 3-dimensional (3-D) printing are leveraging other advances in regenerative medicine. It is now possible to 3-D-print patient-specific implants from a variety of polymer, ceramic, or metal components. A skull template may be used to design the external shape of an implant that will become well integrated in the skull, while also providing beneficial distribution of mechanical force in the event of trauma. Furthermore, an internal pore geometry can be utilized to facilitate the seeding of banked allograft cells. Implants may be cultured in a bioreactor along with recombinant growth factors to produce implants coated with bone progenitor cells and extracellular matrix that appear to the body as a graft, albeit a tissue-engineered graft. The growth factors would be left behind in the bioreactor and the graft would resorb as new host bone invades the space and is remodeled into strong bone. As we describe in this review, such advancements will lead to optimal replacement of cranial defects that are both patient-specific and regenerative.

Cranioplasty for large-sized calvarial defects in the pediatric population: a review

Large-sized calvarial defects in pediatric patients pose a reconstructive challenge because of children's unique physiology, developing anatomy, and dynamic growth. We review the current literature and outcomes with autologous and alloplastic cranioplasty in the pediatric population.

Effect of bone material properties on effective region in screw-bone model: an experimental and finite element study

Background

There have been numerous studies conducted to investigate the pullout force of pedicle screws in bone with different material properties. However, fewer studies have investigated the region of effect (RoE), stress distribution and contour pattern of the cancellous bone surrounding the pedicle screw.

Methods

Screw pullout experiments were performed from two different foams and the corresponding reaction force was documented for the validation of a computational pedicle screw-foam model based on finite element (FE) methods. After validation, pullout simulations were performed on screw-bone models, with different bone material properties to model three different age groups (<50, 50–75 and >75 years old). At maximum pullout force, the stress distribution and average magnitude of Von Mises stress were documented in the cancellous bone along the distance beyond the outer perimeter pedicle screw. The radius and volume of the RoE were predicted based on the stress distribution.

Results

The screw pullout strengths and the load–displacement curves were comparable between the numerical simulation and experimental tests. The stress distribution of the simulated screw-bone vertebral unit showed that the radius and volume of the RoE varied with the bone material properties. The radii were 4.73 mm, 5.06 mm and 5.4 mm for bone properties of ages >75, 75 > ages >50 and ages <50 years old, respectively, and the corresponding volumes of the RoE were 6.67 mm³, 7.35 mm³ and 8.07 mm³, respectively.

Conclusions

This study demonstrated that there existed a circular effective region surrounding the pedicle screw for stabilization and that this region was sensitive to the bone material characteristics of cancellous bone. The proper amount of injection cement for augmentation could be estimated based on the RoE in the treatment of osteoporosis patients to avoid leakage in spine surgery.

Customized cranioplasty implants using three-dimensional printers and polymethyl-methacrylate casting

Objective

The prefabrication of customized cranioplastic implants has been introduced to overcome the difficulties of intra-operative implant molding. The authors present a new technique, which consists of the prefabrication of implant molds using three-dimensional (3D) printers and polymethyl-methacrylate (PMMA) casting.

Methods

A total of 16 patients with large skull defects (>100 cm²) underwent cranioplasty between November 2009 and April 2011. For unilateral cranial defects, 3D images of the skull were obtained from preoperative axial 1-mm spiral computed tomography (CT) scans. The image of the implant was generated by a digital subtraction mirror-imaging process using the normal side of the cranium as a model. For bilateral cranial defects, precraniectomy routine spiral CT scan data were merged with postcraniectomy 3D CT images following a smoothing process. Prefabrication of the mold was performed by the 3D printer. Intraoperatively, the PMMA implant was created with the prefabricated mold, and fit into the cranial defect.

Results

The median operation time was 184.36±26.07 minutes. Postoperative CT scans showed excellent restoration of the symmetrical contours and curvature of the cranium in all cases. The median follow-up period was 23 months (range, 14-28 months). Postoperative infection was developed in one case (6.2%) who had an open wound defect previously.

Conclusion

Customized cranioplasty PMMA implants using 3D printer may be a useful technique for the reconstruction of various cranial defects.

Using rapid prototyping molds to create patient specific polymethylmethacrylate implants in cranioplasty

Cranioplasty is a commonly performed procedure. Outcomes can be improved by the use of patient specific implants, however, high costs limit their accessibility. This paper presents a low cost alternative technique to create patient specific polymethylmethacrylate (PMMA) implants using rapid prototyped mold template. We used available patient's CT-scans, one dataset without craniotomy and one with craniotomy, for computer-assisted design of a 3D mold template, which itself can be brought into the operating room and be used for fast and easy building of a PMMA implant. We applied our solution to three patients with positive outcomes and no complications.