Interval cranioplasty with patient-specific implants and autogenous bone grafts--success and cost analysis

A Single Standard Polyvinyl Chloride 3D Skull Model to Create the Polymethyl Methacrylate Cranioplasty Flap: A Novel and Low-Cost Technique

BACKGROUND

 Although, cranioplasty is a commonly performed neurosurgical procedure worldwide, the cost of available cranioplasty implants is a major issue in a low-income country like India. The aims of this study were to introduce a novel and low-cost technique using a single standard three-dimensional (3D) skull model to guide the polymethyl methacrylate (PMMA) cranioplasty flap production and to evaluate the functional and cosmetic outcomes.

METHODS

 We retrospectively evaluated 47 cases of PMMA cranioplasty in the period from February 2019 to June 2022. A single standard 3D skull model was used to make the PMMA cranioplasty flaps. The overall cost of this PMMA implant was compared with that of other available cranioplasty implants. The functional and cosmetic outcomes were evaluated postoperatively.

RESULTS

 The mean age of our patients was 37.17 ± 13.83 years and the age range was 17 to 63 years. The primary cause of surgery was trauma in the majority of cases (n = 31, 65.96%). The mean operative time was 78.55 ± 19.82 minutes. The cosmetic results were very satisfying in 46 of 47 (97.87%) patients and moderately satisfying in 1 (2.12%) patient. Overall, there were three (6.38%) complications.

CONCLUSION

 Our technique provides excellent functional and cosmetic outcomes. The overall surgical cost of these PMMA implants was lower than that of the other available cranioplasty implants. This technique is currently the most cost-effective option for cranioplasty.

Patient-specific cranioplasty, by direct and indirect additive manufacturing of biopolymers and implantable materials

BACKGROUND

Autologous bones are traditionally used in surgical reconstruction of skullcap. Since patients' bones are often unavailable or cause of infections, implantable synthetic materials emerged as promising alternative. These can be shaped by different technologies, while 3D printing offers remarkable chances in terms of flexibility, accuracy, cost-saving and customizability.

METHODS

This study aims to evaluate strengths and limitations of the three main strategies that imply additive manufacturing for the implementation of cranial prosthesis: (i) direct printing of PLA (polylactic acid) skullcaps, mould casting of poly(methyl methacrylate) (PMMA) prosthesis using (ii) silicone mould manufactured from a 3D printed master, (iii) 3Dprinted TPU (thermoplastic polyurethane) mould.

RESULTS

All solutions achieved good geometric accuracy and excellent mechanical resistance. Direct printing of the PLA resulted in the fastest strategy, followed by PMMA casting in a silicone mould.

CONCLUSIONS

The use of silicone was overall more advantageous, due to lower costs and the possibility of sterilization by using autoclaving.

What is the Accuracy of PEEK Implants for Cranioplasty in Comparison to Their Patient Specific Surgical Plan?

PURPOSE

Patient specific virtual surgical planning is a useful tool in craniofacial reconstruction. The aim of this paper is to quantify the surgical accuracy of polyetheretherketone (PEEK) cranial implant placement by comparing a computer tomography (CT)-based plan with the measured postoperative position.

MATERIALS AND METHODS

This is a retrospective case series. All patients who presented for evaluation and management of cranial defects at the University Health Sciences Center at San Antonio from June 2018 to July 2021 were eligible for the study. For each patient, we assessed accuracy by comparing the planned PEEK implant position, defined by a 3-dimensional mesh, to the measured postoperative position at multiple mesh vertices. The primary outcome variable in our study is the root mean square error (RMSE) between the planned position and the actual position of the implant.

RESULTS

Twelve patients (7 men, 5 women, mean age: 25.6, median age: 30.5, range 6-74) were identified who underwent cranioplasty procedures with custom-made PEEK implants to reconstruct cranial defects. The RMSE of the vertex positions ranged between 0.66 and 3.1 millimeters (mm). Eleven of the twelve patients had an RMSE less than 2 mm. The Spearman rank-order correlation between the average error and the length and area of the implant were 0.59 (P = .04, significant) and 0.42 (P = .17, nonsignificant), respectively. The Pearson correlation between age and RMSE was -0.18 (P = .57), and not significant.

CONCLUSION

Patient specific implant planning can design and guide the implant placement with a typical accuracy within 2 mm. This level of accuracy suggests that we can place implants accurately enough to achieve good patient aesthetics. The quantitative analysis suggests that the key to accurate placement is understanding the number and spatial distribution of plates and fixation.

Preservation of Infraorbital Nerve in Orbital Floor and Maxillary Defect Reconstruction With Patient-Specific Three-Dimensional Implant: A Case Report

Reconstruction of orbitomaxillary defects poses many operative challenges because it requires consideration of cosmetic as well as functional elements: reestablishing facial symmetry while constituting the orbital volume and preserving involved neurovascular structures. The development of patient-specific polyetheretherketone implants have revolutionized complex craniofacial reconstruction due to its adaptability to anatomic constraints and accommodation of vital structures. Herein, we described 2 cases of orbitomaxillary reconstruction using PEEK implant with novel modifications to preserve the infraorbital nerve with optimal cosmetic outcomes and minimal postoperative morbidity.

Early experience with patient-specific low-cost 3D-printed polymethylmethacrylate cranioplasty implants in a lower-middle-income-country: Technical note and economic analysis

Background:

Polymethyl methacrylate (PMMA) cranioplasty, while widely prevalent, has limitations associated with freehand manual intraoperative molding. PMMA has been superseded by titanium or Polyetheretherketone implants, prefabricated commercially from preoperative CT scans, and boasting superior clinical and cosmetic outcomes. However, such services are extremely inaccessible and unaffordable in the lower-middle-income country (LMIC) settings. The study aims to describe, in detail, the process of making ultra-low-cost patient-specific PMMA cranioplasty implants with minimum resources using open-access software. We report the first such service from the public health-care system within Pakistan, a LMIC.

Methods:

Using open-source software, preoperative CT heads were used to prefabricate three-dimensional implants. Both implant and cranial defects were printed using polylactic acid (PLA) to assess the implant’s size and fit preoperatively. From the PLA implant, we fashioned a silicon mold that shapes the PMMA implant. Ten patients who underwent cranioplasty using our technique for various cranial defects with at least a 12-month follow-up were retrospectively reviewed. Clinical, cosmetic, and radiological outcomes were objectively assessed.

Results:

Etiology of injury was trauma (8), malignant MCA infarct (1), and arteriovenous fistula (1). We produced seven frontotemporal-parietal implants, one bifrontal, one frontal, and one frontoparietal. At 1 year, eight patients reported their cosmetic appearance comparable to before the defect. Radiological outcome was classified as “excellent” for eight patients. No postoperative complications were encountered, nor did any implant have to be removed. One patient’s implant involving the orbital ridge had an unsatisfactory cosmetic outcome and required revision surgery. The average cost per implant to the National Health Service was US$40.

Conclusion:

Prefabricated patient-specific PMMA cranioplasty implants are cost-effective. A single surgeon can fashion them in a limited resource setting and provide personalized medicine with excellent clinical/cosmetic-radiological results. Our method produces patient-specific cranioplasty implants in an otherwise unaffordable LMIC setting.

Histological Processing of CAD/CAM Titanium Scaffold after Long-Term Failure in Cranioplasty

Cranioplasty is a frequently performed procedure after craniectomy and includes several techniques with different materials. Due to high overall complication rates, alloplastic implants are removed in many cases. Lack of implant material osseointegration is often assumed as a reason for failure, but no study has proven this in cranioplasty. This study histologically evaluates the osteointegration of a computer-aided design and computer-aided manufacturing (CAD/CAM) titanium scaffold with an open mesh structure used for cranioplasty. A CAD/CAM titanium scaffold was removed due to late soft tissue complications 7.6 years after cranioplasty. The histological analyses involved the preparation of non-decalcified slices from the scaffold’s inner and outer sides as well as a light-microscopic evaluation, including the quantification of the bone that had formed over the years. Within the scaffold pores, vital connective tissue with both blood vessels and nerves was found. Exclusive bone formation only occurred at the edges of the implant, covering 0.21% of the skin-facing outer surface area. The inner scaffold surface, facing towards the brain, did not show any mineralization at all. Although conventional alloplastic materials for cranioplasty reduce surgery time and provide good esthetic results while mechanically protecting the underlying structures, a lack of adequate stimuli could explain the limited bone formation found. CAD/CAM porous titanium scaffolds alone insufficiently osseointegrate in such large bone defects of the skull. Future research should investigate alternative routes that enable long-term osteointegration in order to reduce complication rates after cranioplasty. Opportunities could be found in mechano-biologically optimized scaffolds, material modifications, surface coatings, or other routes to sustain bone formation.

Patient specific Polymethyl methacrylate customised cranioplasty using 3D printed silicone moulds: Technical note

INTRODUCTION

Cranioplasty after decompressive craniectomy can be performed with several techniques and materials. With the common use of 3D printing, custom cranioplasty can be produced at affordable cost. Aim of this technical note is to describe our technique for producing patient specific Polymethyl methacrylate (PMMA) cranioplasty using 3D printed silicone moulds.

MATERIALS AND METHODS

We enrolled seven patients from January 2020 to June 2021 who required surgery for cranioplasty. The 3D printing was used to produce silicone moulds for defining the exact shape of the PMMA cranioplasty, according to the CT scan of the patient.

RESULTS

We performed seven procedures. The mean time of the surgery was 80 min. All cranioplasties perfectly matched the patient specific anatomy. No complications occurred.

CONCLUSIONS

Using 3D printed patient specific silicone moulds and PMMA resulted to be effective, with affordable costs and ensuring a good cosmetic result.

Efficacy of 3D-Printed Titanium Mesh-Type Patient-Specific Implant for Cranioplasty

Objective

Autologous bone grafting for cranioplasty is associated with a high infection rate and bone absorption. Synthetic implant materials for cranioplasty have been developed. In this study, we evaluated the efficacy of titanium mesh-type patient-specific implants (PSIs) for patients with skull defects using the dice similarity coefficient (DSC), clinical outcomes, and artifacts caused by implants.

Methods

This retrospective study included 40 patients who underwent cranioplasty with a titanium mesh PSI at our institution. Based on preoperative and postoperative computed tomography scans, we calculated DSC and artifacts.

Results

The calculated DSC of 40 patients was 0.75, and the noise was 13.89% higher in the region of interest (ROI) near the implanted side (average, 7.64 hounsfield unit [HU]±2.62) than in the normal bone (average, 6.72 HU±2.35). However, the image signal-to-noise ratio did not significantly differ between the ROI near the implanted side (4.77±1.78) and normal bone (4.97±1.88). The patients showed no significant perioperative complications that required a secondary operation.

Conclusion

Titanium mesh-type PSIs for cranioplasty have excellent DSC values with lower artifacts and complication rates.

Feasibility of Customised Polymethyl Methacrylate Implants Fabricated Using 3D Printed Flexible Moulds for Correction of Facial Skeletal Deformities

INTRODUCTION

Use of patient specific Polymethyl methacrylate (PMMA) implants for the reconstruction of cranial defects has become a standard practice with excellent long-term results. However, for the reconstruction of midface and mandibular osseous defects other alloplastic materials are preferred but their use is limited due to high cost. This is a report of our experience with the use of low-cost patient specific PMMA implants fabricated using 3D printed moulds in the reconstruction of osseous defects involving different areas of the facial skeleton not limited to cranium.

METHODS

The 25 consecutive patients with craniofacial osseous defects who underwent reconstruction using customized PMMA implants were analyzed. All PMMA implants were fabricated intraoperatively with the use of 3D printed flexible moulds or templates.

RESULTS

A total of 34 implants were used in 25 consecutive patients. Out of 34 implants 25 were used for midface and mandibular osseous defects. Most common etiology was post-traumatic deformity (n = 19) followed by tumor (n = 3), craniofacial anomalies (n = 2) and post-craniotomy (n = 1). One patient out of 25 (n = 1) had postoperative implant exposure. The follow-up was ranged from 3 to 19 months with an average of 12 months. The aesthetic outcome was found to be good to excellent with mean visual analogue score of 4.08.

CONCLUSIONS

Polymethyl methacrylate implants fabricated intraoperatively using 3D printed moulds provide accurate and precise reconstruction at an exceptionally low cost. PMMA has an excellent moulding property with low infection rates. As shown in our study its application may be easily extended to all areas of the craniofacial skeleton.

Factors predicting complications following cranioplasty

This study aimed to identify factors that predict complications following cranioplasty, by conducting a retrospective cohort study at a large tertiary care center. Electronic databases were searched to identify all patients who underwent cranioplasty at our institution. Baseline demographics, perioperative variables, and outcomes were extracted. Logistic regression analyses were conducted to identify factors associated with cranioplasty complications. Of the 92 included patients, 15 (16.3%) experienced one or more complications, with 11 (73.3%) experiencing complication within 30 days of cranioplasty. Patients aged ≤60 had decreased odds of all-cause complication (OR 0.058; 95% CI 0.008-0.434) and cranioplasty graft removal (OR 0.035; 95% CI 0.004-0.321) on multivariate analysis. Titanium mesh cranioplasties were associated with increased odds of all-cause complication (OR 19.776; 95% CI 1.021-382.901), and cranioplasty removal (OR 29.780; 95% CI 1.330-666.878). A longer craniectomy-cranioplasty interval was associated with increased odds of cranioplasty removal (OR 1.005; 95% CI 1.000-1.010). An initial craniectomy indication of cerebral infarction was associated with decreased odds of all-cause complication (OR 0.042; 95% CI 0.002-0.876) and cranioplasty removal (OR 0.032; 95% CI 0.001-0.766). Elderly patients may require more aggressive follow-up and antibiotic prophylaxis in the postoperative period following cranioplasty. Additionally, avoiding the use of titanium mesh cranioplasties and prolonged craniectomy-cranioplasty intervals may further reduce complications.

The Materials Utilized in Cranial Reconstruction: Past, Current, and Future

BACKGROUND

Cranioplasty (CP) is associated with high complication rates compared to other common neurosurgical procedures. Several graft materials are used for CP, which may contribute to the high complication rates, but data in the literature regarding the influence of graft material on post-CP outcomes are inconsistent making it difficult to determine if, when, and to what extent the graft material impacts the rate of perioperative complications. There is an increased demand to identify and develop superior graft materials.

OBJECTIVE

To review and compare the indications, risks, complications, and patient results associated with the use of different graft materials for cranial reconstructions.

DESIGN

A search through EBSCOhost was conducted using the keywords "craniectomy" or "decompressive craniectomy," "cranioplasty," and "materials." The search was limited to literature published in the English language from 2005 until the present. Ultimately, 69 articles were included in this review. Due to the heterogeneity of the study populations, results, statistical analyses, and collecting methods, no statistical analyses could be performed.

CONCLUSIONS

Several graft materials have been adapted for use in cranial reconstructions with inconsistent results making it unclear if or when one material may be indicated over others. Advances in computer-aided design have led to improved patient-specific implants, but the ideal graft material is still being sought after in ongoing research efforts. Reviewing materials currently available, as well as those in clinical trials, is important to identify the limitations associated with different implants and to guide future research.

Decision-Making in Adult Cranial Vault Reconstruction

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Define and classify different types of cranial defects 2. Compare both autologous and alloplastic options for reconstruction 3. Develop an optimal approach for cranial vault reconstruction in various clinical scenarios.

SUMMARY

Defects of the cranium result from various causes, including traumatic loss, neurosurgical intervention, skull tumors, and infection. Cranial vault reconstruction aims to restore both the structural integrity and surface morphology of the skull. To ensure a successful outcome, the choice of appropriate cranioplasty reconstruction will vary primarily based on the cause, location, and size of the defect. Other relevant factors that must be considered include adequacy of soft-tissue coverage, presence of infection, and previous or planned radiation therapy. This article presents an algorithm for the reconstruction of various cranial defects using both autologous and alloplastic techniques, with a comparison of their advantages and disadvantages.

A novel prefabricated patient-specific titanium cranioplasty: reconsideration from a traditional approach

OBJECTIVE

Patient-specific implants (PSI) for cranioplasty are expensive, and cost remains the limiting factor in low- to middle-income countries. The authors describe a novel, reproducible and cost-effective method of designing prefabricated titanium PSI cranioplasty.

METHODS

Ten patients from June 2018 to December 2020 were included in this retrospective study. A three-dimensional stereolithography model was made on a custom-built 3D printer with variable layer heights to produce efficient and accurate details. A certain amount of defect in the temporal region was left uncovered to avoid complications related to temporalis muscle dissection. The stereolithography model with a cranial defect was reconstructed with modelling wax. The wax model was scanned with a blue light visible scanner. The digital data was transferred to the milling machine (Jayon Surgical®, Kerala, India), where a 1-mm-thick sheet of titanium was milled according to the specifications. RFCC scoring system was used for assessing cosmetic outcome.

RESULTS

The mean duration of the surgery was 56.50 min, SD = 14.916 min (range 45-75 min). In 9/10 patients, the RFCC score was 4 points. No other complications were found at a minimum follow-up of 18 months in all patients. The cost per patient was approximately 30,000 INR or 400 US dollars. The average time required for us to get the PSI ready for surgery was about 15 days.

CONCLUSION

The authors demonstrate a novel, cost-effective and reproducible method of PSI using titanium for cranioplasty.

Security and reliability of CUSTOMBONE cranioplasties: A prospective multicentric study

BACKGROUND

Repairing bone defects generated by craniectomy is a major therapeutic challenge in terms of bone consolidation as well as functional and cognitive recovery. Furthermore, these surgical procedures are often grafted with complications such as infections, breaches, displacements and rejections leading to failure and thus explantation of the prosthesis.

OBJECTIVE

To evaluate cumulative explantation and infection rates following the implantation of a tailored cranioplasty CUSTOMBONE prosthesis made of porous hydroxyapatite. One hundred and ten consecutive patients requiring cranial reconstruction for a bone defect were prospectively included in a multicenter study constituted of 21 centres between December 2012 and July 2014. Follow-up lasted 2 years.

RESULTS

Mean age of patients included in the study was 42±15 years old (y.o), composed mainly by men (57.27%). Explantations of the CUSTOMBONE prosthesis were performed in 13/110 (11.8%) patients, significantly due to infections: 9/13 (69.2%) (p<0.0001), with 2 (15.4%) implant fracture, 1 (7.7%) skin defect and 1 (7.7%) following the mobilization of the implant. Cumulative explantation rates were successively 4.6% (SD 2.0), 7.4% (SD 2.5), 9.4% (SD 2.8) and 11.8% (SD 2.9%) at 2, 6, 12 and 24 months. Infections were identified in 16/110 (14.5%): 8/16 (50%) superficial and 8/16 (50%) deep. None of the following elements, whether demographic characteristics, indications, size, location of the implant, redo surgery, co-morbidities or medical history, were statistically identified as risk factors for prosthesis explantation or infection.

CONCLUSION

Our study provides relevant clinical evidence on the performance and safety of CUSTOMBONE prosthesis in cranial procedures. Complications that are difficulty incompressible mainly occur during the first 6 months, but can appear at a later stage (>1 year). Thus assiduous, regular and long-term surveillances are necessary.

Cranioplasty Using Customized 3-Dimensional-Printed Titanium Implants: An International Collaboration Effort to Improve Neurosurgical Care

BACKGROUND

Evolutions in cranioplasty have allowed for the creation of customized implants via advances in 3-dimensional (3D) printing technology, although the high cost associated with this technique presents a barrier for low-income countries. Through an international collaboration, our team in Da Nang, Vietnam is able to create low-cost, customized titanium implants for patients with skull defects. We discuss the details of our collaboration and present our experience with this procedure.

METHODS

We conducted a retrospective review of 35 patients who underwent cranioplasty using custom-made titanium implants. The molding and implant making processes were performed by our neurosurgeons using a 3D printer donated by the United Kingdom-based nongovernmental organization Facing the World. We obtained demographic and preoperative data (reason for skull defect, location, surface area measurement of defect) and postoperative data (complications, cosmetic outcome, and patient satisfaction).

RESULTS

The median patient age was 27 years (range, 16-60 years). Primary indications for craniectomy included traumatic brain injury from motor vehicle accident (77.1%), cerebrovascular disease (11.4%), implant failure following previous cranioplasty (5.7%), and fall (5.7%). Postoperatively, all implants were found to have an excellent fit; at 6-month follow-up, none of the implants required removal. Complications included 4 postoperative hematomas and 1 surgical site infection. All the patients had improved aesthetic appearance and high satisfaction.

CONCLUSIONS

Cranioplasty using customized titanium implants yields excellent results for patients with skull defects, demonstrating the practicality of this technique for cranioplasty in low-income countries. Our experience highlights the importance of ongoing international collaboration to improve neurosurgical care in these countries.

Patient-Specific Three-Dimensional Printing Guide for Single-Stage Skull Bone Tumor Surgery: Novel Software Workflow with Manufacturing of Prefabricated Jigs for Bone Resection and Reconstruction

OBJECTIVE

To describe a novel system workflow to design and manufacture patient-specific three-dimensional (3D) printing jigs for single-stage skull bone tumor excision and reconstruction and to present surgical outcomes of 14 patients.

METHODS

A specific computer-aided design/computer-aided manufacturing software and hardware system was set up, including a virtual surgical planning subsystem and a 3D printing-associated manufacturing subsystem. Computed tomography data of the patient's skull were used for 3D rendering of the skull and tumor. The output of patient-specific designing included a 3D printing guide for tumor resection and a 3D printing model of the bone defect after tumor excision. A polymethyl methacrylate implant was fabricated preoperatively and used for repair.

RESULTS

The specific 3D printing guide was used to design intraoperative jigs and implants for 14 patients (age range, 1-72 years) with skull bone tumors. In all cases, the cutting jig allowed precise excision of tumor and bone, and implants were exact fits for the defects created. All operative results were successful, without intraoperative or postoperative complications. Postoperative computed tomography scans were obtained for analysis. Postoperative 3D measurement of the skull symmetry index (cranial vault asymmetry index) showed significant improvement of head contour after surgery.

CONCLUSIONS

The computer-aided design/computer-aided manufacturing system described allows definitive preoperative planning and fabrication for treatment of skull bone tumors. Apparent benefits of the method include more accurate determination of surgical margins and better oncological outcomes.

Three-dimensional (3D) synthetic printing for the manufacture of non-biodegradable models, tools and implants used in surgery: a review of current methods

The advent of three-dimensional (3D) printing in the 1980s ushered in a new era of manufacturing. Original 3D printers were large, expensive and difficult to operate, but recent advances in 3D printer technologies have drastically increased the accessibility of these machines such that individual surgical departments can now afford their own 3D printers. As adoption of 3D printing technology has increased within the medical industry so too has the number of 3D printable materials. Selection of the appropriate printer and material for a given application can be a daunting task for any clinician. This review seeks to describe the benefits and drawbacks of different 3D printing technologies and the materials used therein. Commercially available printers using fused deposition modelling or fused filament fabrication technology and relatively inexpensive thermoplastic materials have enabled rapid manufacture of anatomic models and intraoperative tools as well as implant prototyping. Titanium alloys remain the gold-standard material for various implants used in the fixation of craniofacial or extremity fractures, but polymers and ceramics are showing increasing promise for these types of applications. An understanding of these materials and their compatibility with various 3D printers is essential for application of this technology in a healthcare setting.

Implicit and explicit finite element models predict the mechanical response of calcium phosphate-titanium cranial implants

The structural integrity of cranial implants is of great clinical importance, as they aim to provide cerebral protection after neurosurgery or trauma. With the increased use of patient-specific implants, the mechanical response of each implant cannot be characterized experimentally in a practical way. However, computational models provide an excellent possibility for efficiently predicting the mechanical response of patient-specific implants. This study developed finite element models (FEMs) of titanium-reinforced calcium phosphate (CaP-Ti) implants. The models were validated with previously obtained experimental data for two different CaP-Ti implant designs (D1 and D2), in which generically shaped implant specimens were loaded in compression at either quasi-static (1 mm/min) or impact (5 kg, 1.52 m/s) loading rates. The FEMs showed agreement with experimental data in the force-displacement response for both implant designs. The implicit FEMs predicted the peak load with an underestimation for D1 (9%) and an overestimation for D2 (11%). Furthermore, the shape of the force-displacement curves were well predicted. In the explicit FEMs, the first part of the force-displacement response showed 5% difference for D1 and 2% difference for D2, with respect to the experimentally derived peak loads. The explicit FEMs efficiently predicted the maximum displacements with 1% and 4% difference for D1 and D2, respectively. Compared to the CaP-Ti implant, an average parietal cranial bone FEM showed a stiffer response, greater energy absorption and less deformation under the same impact conditions. The framework developed for modelling the CaP-Ti implants has a potential for modelling CaP materials in other composite implants in future studies since it only used literature based input and matched boundary conditions. Furthermore, the developed FEMs make an important contribution to future evaluations of patient-specific CaP-Ti cranial implant designs in various loading scenarios.

Rapid high-fidelity contour shaping of titanium mesh implants for cranioplasty defects using patient-specific molds created with low-cost 3D printing: A case series

Background:

Cranioplasty is a neurosurgical procedure to repair skull defects. Sometimes, the patients’ bone flap cannot be used for various reasons. Alternatives include a custom polyether ether ketone (PEEK) implant or titanium mesh; both incur an additional cost. We present a technique that uses a 3D printer to create a patient- specific 3D model used to mold a titanium mesh preoperatively.

Case Description:

We included three patients whose bone flap could not be used. We collected the patients’ demographics, cost, and time data for implants and the 3D printer. The patients’ computed tomography DICOM images were used for 3D reconstruction of the cranial defect. A 3D printer (Flashforge, CA) was used to print a custom mold of the defect, which was used to shape the titanium mesh. All patients had excellent cosmetic results with no complications. The time required to print a 3D model was ~ 6 h and 45 min for preoperative shaping of the titanium implant. The intraoperative molding (IOM) of a titanium mesh needed an average of 60 min additional operative room time which incurred $4000. The average cost for PEEK and flat titanium mesh is $12,600 and $6750. Our method resulted in $4000 and $5500 cost reduction in comparison to flat mesh with IOM and PEEK implant.

Conclusion:

3D printing technology can create a custom model to shape a titanium mesh preoperatively for cranioplasty. It can result in excellent cosmetic results and significant cost reduction in comparison to other cranioplasty options.

Negative Pressure Wound Therapy With Chymotrypsin Irrigation: A Maximal Implant Retention Procedure Treating the Exposure/Infection of Titanium Mesh in Cranioplasty

This preliminary study aims to investigate the effects of a maximal implant retention procedure. The authors retrospectively reviewed the use of negative pressure wound therapy with chymotrypsin irrigation treating implant infection/exposure in titanium mesh cranioplasty by comparing patients with titanium mesh totally retained, partially removed, or totally removed according to the evaluation during the surgery. Negative pressure wound therapy with chymotrypsin irrigation was applied 5 days after the surgery. The negative pressure was set at -125 to -150 mmHg. A total of 21 patients were included, 4 patients treated with titanium mesh totally removed; 3 patients treated with titanium mesh partially removed; and 14 patients treated with U-shape debridement with titanium mesh preserved completely. However, 1 patient in the U-shape group required a second debridement to remove all implant. Negative pressure wound therapy with chymotrypsin irrigation is a novel procedure and could be used to treat implant-related infection without the exchange of implant.

Parameterized design and fabrication of porous bone scaffolds for the repair of cranial defects

In bone tissue engineering, the structure of a scaffold is very important for cell growth and bone regeneration. It is better to make the scaffold resemble the native cancellous bone because natural cancellous bone can promote scaffold revascularization, which then accelerates cell proliferation. This study presents a parameterized design and fabrication method for cranial scaffold construction. A native human cranial sample was first scanned using micro computed tomography (CT), followed by 3D reconstruction, after which the internal structure of the bone trabecula was created. Based on an extracted negative bone trabecula model, the design components of "cavity", "connecting pipe" and "spatial framework" were proposed to describe the scaffold model. Then, by using the parameterized component model and an assembly and deformation algorithm, the bionic scaffold was designed. Its porous distribution, connection, porosity and area size were easily controlled. Finally, a biomaterial scaffold case was fabricated using a gelcasting process, and cell culture testing was performed in vitro to verify the scaffold's biocompatibility. The results show that the scaffold can promote cell growth and that cells accumulate in the form of a mass within three days.

Presentation and short-term evaluation of an all-in-one patient-specific implant for cranial reconstruction: A randomized controlled trial

Cranial reconstruction after bone graft harvesting remains a challenge. A patient-specific implant (PSI) to guide harvesting and reconstruction was evaluated and compared with the use of a free-hand procedure with calcium phosphate cement (C). Patients were randomized to either the PSI or C group. The outcome was measured clinically and radiographically as the primary endpoint. Secondary endpoints were ease of application, patient and surgeon satisfaction, and the complication rate. Twenty patients were randomized to the PSI (n=10) and C (n=10) groups. Two PSI patients were switched to the cement group due to a poor fit of the PSI. There was a non-significant trend towards more successful outcomes in the PSI group. Two PSI patients presented palpable screws, and one cement patient had a palpable dimple. Cone beam computed tomography showed a significantly lower median volume discrepancy in the PSI group (P<0.0001). The total surgical manipulation time was significantly higher in the PSI group. At 10 days postoperative, three PSI and two C patients presented with minor postoperative complications. There was no significant difference in patient or surgeon satisfaction. PSIs are a reliable alternative to cement. This PSI is novel as it also serves as a guide for harvesting the bone blocks required for reconstructive purposes.

Comparative Cost-Effectiveness of Cranioplasty Implants

Purpose

The aim of this study was to compare operative duration and total hospital costs incurred for patients undergoing elective cranioplasty with a variety of materials, including manually shaped autogenous bone graft and titanium mesh, custom patient-specific titanium mesh, polymethyl methacrylate (PMMA) acrylic, and polyetheretherketone (PEEK) implants.

Methods

A single-centre retrospective chart review was used. Patient demographics, defect characteristics, total operative time, and length of hospital stay were obtained. Total costs were sourced from Sunnybrook and standardized to the 2014 to 2015 year. Bivariate and age-controlled multivariate analyses were performed with (n = 119) and without (n = 101) outliers.

Results

When outliers were removed, an age-controlled analysis revealed that autogenous implants resulted in an operative time of 178 ± 37 minutes longer than manually shaped titanium implants (P < .01). The average cost of cranioplasty was CAD$18 335 ± CAD$10 265 for manually shaped titanium implants, CAD$31 956 ± CAD$31 206 for custom patient-specific titanium implants, CAD$20 786 ± CAD$13 075 for PMMA, CAD$14 291 ± CAD$5562 for autogenous implants, and CAD$27 379 ± CAD$4945 for PEEK implants (P = .013). When outliers were removed, cranioplasty with PMMA and PEEK incurred greater costs, CAD$4442 ± CAD$2100 and CAD$13 372 ± CAD$2728, respectively, more than manually shaped titanium implants (P < .01).

Conclusions

Manually shaped titanium mesh is the most cost-effective implant choice for small cranial defects. Large unknown defects and frontal paranasal sinus defects are most effectively treated with autogenous bone or titanium mesh. Despite prolonged operative duration and inpatient admission, total costs were not significantly increased. Both PMMA and PEEK implants were significantly more costly, which may be a result of higher complications necessitating reoperation.

Amorphous Silicon Oxynitrophosphide-Coated Implants Boost Angiogenic Activity of Endothelial Cells

Lack of osteointegration is a major cause of aseptic loosening and failure of implants used in bone replacement. Implants coated with angiogenic biomaterials can improve osteointegration and potentially reduce these complications. Silicon- and phosphorus-based materials have been shown to upregulate expression of angiogenic factors and improve endothelial cell functions. In the present study, we hypothesize that implants coated with amorphous silica-based coatings in the form of silicon oxynitrophosphide (SiONP) by using plasma-enhanced chemical vapor deposition (PECVD) technique could enhance human umbilical vein endothelial cell angiogenic properties in vitro. The tested groups were: glass coverslip (GCS), tissue culture plate, SiON, SiONP1 (O: 7.3 at %), and SiONP2 (O: 14.2 at %) implants. The SiONP2 composition demonstrated 3.5-fold more fibronectin deposition than the GCS (p < 0.001). The SiONP2 group also presented a significant improvement in the capillary tubule length and thickness compared with the other groups (p < 0.01). At 24 h, we observed at least a twofold upregulation of vascular endothelial growth factor A, hypoxia-inducible factor-1α, angiopoietin-1, and nesprin-2, more evident in the SiONP1 and SiONP2 groups. In conclusion, the studied amorphous silica-coated implants, especially the SiONP2 composition, could enhance the endothelial cell angiogenic properties in vitro and may induce faster osteointegration and healing. Impact Statement In this study, we report for the first time the significant enhancement of human umbilical vein endothelial cell angiogenic properties (in vitro) by the amorphous silica-based coatings in the form of silicon oxynitrophosphide (SiONP). The SiONP2 demonstrated 3.5-fold more fibronectin deposition than the glass coverslip and presented a significant improvement in the capillary tubule length and thickness. At 24 h, SiONP reported twofold upregulation of vascular endothelial growth factor A, hypoxia-inducible factor-1α, angiopoietin-1, and nesprin-2. The studied amorphous silica-coated implants enhance the endothelial cell angiogenic properties in vitro and may induce faster osteointegration and healing.

Computer-Aided-Design/Computer-Aided-Manufacturing Titanium Cranioplasty in a Child: Critical Appraisal

Large skull bone defects of the cranial vault can result from various reasons. Reconstruction of these defects is performed for protective and aesthetic reasons but is also required for adequate intracranial homeostasis. Computer-aided-design/computer-aided-manufacturing (CAD/CAM) patient-specific skull implants have become the most valuable alternative to the traditional methods of reconstruction and a growing number of publications is dealing with this topic in adults. Literature related to the application of these implants in pediatric cranioplasty is, however, still scarce.The authors present a case of a 9-year-old boy, where cranioplasty using a CAD/CAM additive manufactured titanium implant led to improvement of symptoms attributed to cerebrospinal fluid circulation problems and intracranial homeostasis disbalance. The authors further reflect on what the role of cranioplasty should be in the therapeutic treatment plan.

A Retrospective Comparative Analysis of Titanium Mesh and Custom Implants for Cranioplasty

BACKGROUND

Autologous bone removed during craniectomy is often the material of choice in cranioplasty procedures. However, when the patient's own bone is not appropriate (infection and resorption), an alloplastic graft must be utilized. Common options include titanium mesh and polyetheretherketone (PEEK)-based custom flaps. Often, neurosurgeons must decide whether to use a titanium or custom implant, with limited direction from the literature.

OBJECTIVE

To compare surgical outcomes of synthetic cranioplasties performed with titanium or vs custom implants.

METHODS

Ten-year retrospective comparison of patients undergoing synthetic cranioplasty with titanium or custom implants.

RESULTS

A total of 82 patients were identified for review, 61 (74.4%) receiving titanium cranioplasty and 21 (25.6%) receiving custom implants. Baseline demographics and comorbidities of the 2 groups did not differ significantly, although multiple surgical characteristics did (size of defect, indication for craniotomy) and were controlled for via a 2:1 mesh-to-custom propensity matching scheme in which 36 titanium cranioplasty patients were compared to 18 custom implant patients. The cranioplasty infection rate of the custom group (27.8%) was significantly greater (P = .005) than that of the titanium group (0.0%). None of the other differences in measured complications reached significance. Discomfort, a common cause of reoperation in the titanium group, did not result in reoperation in any of the patients receiving custom implants.

CONCLUSION

Infection rates are higher among patients receiving custom implants compared to those receiving titanium meshes. The latter should be informed of potential postsurgical discomfort, which can be managed nonsurgically and is not associated with return to the operating room.

Polymethyl Methacrylate in Patient-Specific Implants: Description of a New Three-Dimension Technique

Polymethyl methacrylate (PMMA), an easily moldable and economical synthetic resin, has been used since the 1940s. In addition, PMMA has good mechanical properties and is one of the most biocompatible alloplastic materials currently available. The PMMA can serve as a spacer and as a delivery vehicle for antibiotics. Prior studies have indicated that no significant differences in infection rates exist between autologous and acrylic cranioplasty. Although inexpensive, the free-hand cranioplasty technique often yields unsatisfactory cosmetic results. In the present study, the application of a recently developed, economic modality for the perioperative application, and molding of PMMA to ensure a precise fit in 16 patients using computer-aided design, computer-aided manufacturing, and rapid prototyping was described.The mean defect size was 102.0 ± 26.4 cm. The mean volume of PMMA required to perform the cranioplasty procedure was 51 mL. The cost of PMMA was approximately 6 Euro (&OV0556;) per mL. The costs of fabricating the implants varied from 119.8 &OV0556; to 1632.0 &OV0556; with a mean of 326.4 &OV0556; ± 371.6. None of the implants required removal during the follow-up period.

Retrospective Chronologic Computed Tomography Analysis of Bone Flap Fusion and Resorption After Craniotomy and Autologous Cryopreserved Cranioplasty

BACKGROUND

In open brain surgery, fixation of the bone flap is the final procedure. The bone flaps then fuse naturally. The objective of this study was to investigate the chronological process of bone fusion after craniotomy and autologous cranioplasty.

METHODS

Retrospective data were collected from patients who underwent craniotomy or cranioplasty after August 2004 and had at least 1 computed tomography (CT) scan at 3 months postsurgery. The patients were divided into a craniotomy group and a cranioplasty group. Head CT scans were analyzed to evaluate bone fusion and resorption.

RESULTS

Records from 978 patients who underwent craniotomy or cranioplasty between September 2004 and November 2015 were reviewed; 369 patients were eligible for the final analysis (craniotomy, n = 276; cranioplasty, n = 93). The mean cryopreservation period for the bone flap in the cranioplasty group was 49.3 days. The mean patient age was 51.4 ± 18.1 years in the craniotomy group and 51.6 ± 17.1 years in the cranioplasty group. Head CT scans showed bone fusion rates of 76.6% in the craniotomy group and 53.3% in the cranioplasty group at 6 months postsurgery (P = 0.015) and 78.6% and 78.1%, respectively, at 1 year postsurgery (P = 0.951). There was also a significant difference in the bone flap resorption rate between the 2 groups.

CONCLUSIONS

Bone flap fusion rates after craniotomy and cranioplasty were significantly different before 12 months, but not significantly different thereafter. Bone resorption occurred more frequently in the cranioplasty group over time.

Three-Dimensionally Printed Hyperelastic Bone Scaffolds Accelerate Bone Regeneration in Critical-Size Calvarial Bone Defects

BACKGROUND

Autologous bone grafts remain the gold standard for craniofacial reconstruction despite limitations of donor-site availability and morbidity. A myriad of commercial bone substitutes and allografts are available, yet no product has gained widespread use because of inferior clinical outcomes. The ideal bone substitute is both osteoconductive and osteoinductive. Craniofacial reconstruction often involves irregular three-dimensional defects, which may benefit from malleable or customizable substrates. "Hyperelastic Bone" is a three-dimensionally printed synthetic scaffold, composed of 90% by weight hydroxyapatite and 10% by weight poly(lactic-co-glycolic acid), with inherent bioactivity and porosity to allow for tissue integration. This study examines the capacity of Hyperelastic Bone for bone regeneration in a critical-size calvarial defect.

METHODS

Eight-millimeter calvarial defects in adult male Sprague-Dawley rats were treated with three-dimensionally printed Hyperelastic Bone, three-dimensionally printed Fluffy-poly(lactic-co-glycolic acid) without hydroxyapatite, autologous bone (positive control), or left untreated (negative control). Animals were euthanized at 8 or 12 weeks postoperatively and specimens were analyzed for new bone formation by cone beam computed tomography, micro-computed tomography, and histology.

RESULTS

The mineralized bone volume-to-total tissue volume fractions for the Hyperelastic Bone cohort at 8 and 12 weeks were 74.2 percent and 64.5 percent of positive control bone volume/total tissue, respectively (p = 0.04). Fluffy-poly(lactic-co-glycolic acid) demonstrated little bone formation, similar to the negative control. Histologic analysis of Hyperelastic Bone scaffolds revealed fibrous tissue at 8 weeks, and new bone formation surrounding the scaffold struts by 12 weeks.

CONCLUSION

Findings from our study suggest that Hyperelastic Bone grafts are effective for bone regeneration, with significant potential for clinical translation.

Workflow for Pediatric Midface and Orbital Reconstruction With a Patient-Specific Autogenous Bone Graft

Extensive midface and orbital reconstruction is challenging, especially in a pediatric population. A 13-year-old patient was diagnosed with fibrous dysplasia of the midface, which required complete resection of the zygomatic bone and orbital floor. The authors present a complete midface and orbital reconstruction, using a patient-specific autologous bone graft, in a growing pediatric patient. Postoperative analysis showed a symmetric orbital floor and good clinical outcome. After 12 months of follow up, no bone resorption was observed. Patient-specific autologous bone grafts have a clear role in the treatment algorithm of patients with large skull bone defects, with emphasis on the pediatric patient. The advantages can be even greater in a pediatric population, because they can benefit more from the minimal invasive approach. Furthermore, this technique allows single-stage complex reconstructive surgeries with a decreased operating time.

Additively manufactured versus conventionally pressed cranioplasty implants: An accuracy comparison

This article compared the accuracy of producing patient-specific cranioplasty implants using four different approaches. Benchmark geometry was designed to represent a cranium and a defect added simulating a craniectomy. An ‘ideal’ contour reconstruction was calculated and compared against reconstructions resulting from the four approaches –‘conventional’, ‘semi-digital’, ‘digital – non-automated’ and ‘digital – semi-automated’. The ‘conventional’ approach relied on hand carving a reconstruction, turning this into a press tool, and pressing titanium sheet. This approach is common in the UK National Health Service. The ‘semi-digital’ approach removed the hand-carving element. Both of the ‘digital’ approaches utilised additive manufacturing to produce the end-use implant. The geometries were designed using a non-specialised computer-aided design software and a semi-automated cranioplasty implant-specific computer-aided design software. It was found that all plates were clinically acceptable and that the digitally designed and additive manufacturing plates were as accurate as the conventional implants. There were no significant differences between the additive manufacturing plates designed using non-specialised computer-aided design software and those designed using the semi-automated tool. The semi-automated software and additive manufacturing production process were capable of producing cranioplasty implants of similar accuracy to multi-purpose software and additive manufacturing, and both were more accurate than handmade implants. The difference was not of clinical significance, demonstrating that the accuracy of additive manufacturing cranioplasty implants meets current best practice.

Cranioplasty with a low-cost customized polymethylmethacrylate implant using a desktop 3D printer

OBJECTIVE

Cranioplasty implants should be widely available, low in cost, and customized or easy to mold during surgery. Although autologous bone remains the first choice for repair, it cannot always be used due to infection, fragmentation, bone resorption, or other causes, which led to use of synthetic alternatives. The most frequently used allogenic material for cranial reconstructions with long-term results is polymethylmethacrylate (PMMA). Three-dimensional printing technology has allowed the production of increasingly popular customized, prefabricated implants. The authors describe their method and experience with a customized PMMA prosthesis using a precise and reliable low-cost implant that can be customized at any institution with open-source or low-cost software and desktop 3D printers.

METHODS

A review of 22 consecutive patients undergoing CT-based, low-cost, customized PMMA cranioplasty over a 1-year period at a university teaching hospital was performed. Preoperative data included patient sex and age; CT modeling parameters, including the surface area of the implant (defect); reason for craniectomy; date(s) of injury and/or resections; the complexity of the defect; and associated comorbidities. Postoperative data included morbiditiy and complications, such as implant exposure, infection, hematoma, seroma, implant failure, and seizures; the cost of the implant; and cosmetic outcome.

RESULTS

Indications for the primary craniectomy were traumatic brain injury (16, 73%), tumor resection (3, 14%), infection (1, 4%), and vascular (2, 9%). The median interval between previous surgery and PMMA cranioplasty was 12 months. The operation time ranged from 90 to 150 minutes (mean 126 minutes). The average cranial defect measured 65.16 cm2 (range 29.31-131.06 cm2). During the recovery period, there was no sign of infection, implant rejection, or wound dehiscence, and none of the implants had to be removed over a follow-up ranging from 1 to 6 months. The aesthetic appearance of all patients was significantly improved, and the implant fit was excellent.

CONCLUSIONS

The use of a customized PMMA was associated with excellent patient, family, and surgeon satisfaction at follow-up at a fraction of the cost associated with commercially available implants. This technique could be an attractive option to all patients undergoing cranioplasty.

The effect of manufacturing techniques on custom-made titanium cranioplasty plates: A pilot study

OBJECTIVE

This study investigated the effect of varying techniques on the surface characteristics of pressed titanium cranioplasty plates, commonly manufactured in laboratory practice. The aim was to highlight the variety of techniques currently used, assess these methods of manufacture and produce manufacturing recommendations.

METHODS

A questionnaire identified manufacturing methods commonly used by maxillofacial prosthetists. The plate surfaces were examined using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectrometry. The surface differences and titanium compositions were statistically analysed.

RESULTS

Bead blasting with aluminium oxide (Al₂O₃) showed a significant decrease (p < 0.001) in titanium surface composition, replaced by a large aluminium content. Trimming tool choice had a significant impact (p = 0.001) on surface contamination by smoothing wheel material deposition; however passivation and anodising techniques had no significant effect (p = 0.293 and p = 0.257, respectively) on the surface composition or roughness of titanium samples.

CONCLUSIONS

A large range of manufacturing techniques of titanium cranioplasty plates was confirmed and significant differences were found. Amongst other recommendations, bead blasting with Al₂O₃ is not recommended for commercially pure titanium implant surface finishing due to aluminium contamination. The recommendations outlined will minimise manufacturing time, reduce risk of complication (thus costs) and unify methods to enable a safe, reliable treatment.

Osteoblast and Bacterial Culture from Cryopreserved Skull Flap after Craniectomy: Laboratory Study

Objective

Cranioplasty using a cryopreserved skull flap is a wide spread practice. The most well-known complications of cranioplasty are postoperative surgical infections and bone flap resorption. In order to find biological evidence of cryopreserved cranioplasty, we investigated microorganism contamination of cryopreserved skulls and cultured osteoblasts from cryopreserved skulls.

Methods

Cryopreserved skull flaps of expired patients stored in a bone bank were used. Cryopreserved skulls were packaged in a plastic bag and wrapped with cotton cloth twice. After being crushed by a hammer, cancellous bone between the inner and outer table was obtained. The cancellous bone chips were thawed in a water bath of 30°C rapidly. After this, osteoblast culture and general microorganism culture were executed. Osteoblast cultures were done for 3 weeks. Microorganism cultures were done for 72 hours.

Results

A total of 47 cryopreserved skull flaps obtained from craniectomy was enrolled. Of the sample, 11 people were women, and the average age of patients was 55.8 years. Twenty four people had traumatic brain injuries, and 23 people had vascular diseases. Among the patients with traumatic brain injuries, two had fracture compound comminuted depressed. The duration of cryopreservation was, on average, 83.2 months (9 to 161 months). No cultured osteoblast was observed. No microorganisms were cultured.

Conclusion

In this study, neither microorganisms nor osteoblasts were cultured. The biological validity of cryopreserved skulls cranioplasty was considered low. However, the usage of cryopreserved skulls for cranioplasty is worthy of further investigation in the aspect of cost-effectiveness and risk-benefit of post-cranioplasty infection.

Review of Cranioplasty after Decompressive Craniectomy

Cranioplasty is an in evitable operation conducted after decompressive craniectomy (DC). The primary goals of cranioplasty after DC are to protect the brain, achieve a natural appearance and prevent sinking skin flap syndrome (or syndrome of the trephined). Furthermore, restoring patients' functional outcome and supplementing external defects helps patients improve their self-esteem. Although early cranioplasty is preferred in recent year, optimal timing for cranioplasty remains a controversial topic. Autologous bone flaps are the most ideal substitute for cranioplasty. Complications associated with cranioplasty are also variable, however, post-surgical infection is most common. Many new materials and techniques for cranioplasty are introduced. Cost-benefit analysis of these new materials and techniques can result in different outcomes from different healthcare systems.

Evolution of design considerations in complex craniofacial reconstruction using patient-specific implants

Previously published evidence has established major clinical benefits from using computer-aided design, computer-aided manufacturing, and additive manufacturing to produce patient-specific devices. These include cutting guides, drilling guides, positioning guides, and implants. However, custom devices produced using these methods are still not in routine use, particularly by the UK National Health Service. Oft-cited reasons for this slow uptake include the following: a higher up-front cost than conventionally fabricated devices, material-choice uncertainty, and a lack of long-term follow-up due to their relatively recent introduction. This article identifies a further gap in current knowledge – that of design rules, or key specification considerations for complex computer-aided design/computer-aided manufacturing/additive manufacturing devices. This research begins to address the gap by combining a detailed review of the literature with first-hand experience of interdisciplinary collaboration on five craniofacial patient case studies. In each patient case, bony lesions in the orbito-temporal region were segmented, excised, and reconstructed in the virtual environment. Three cases translated these digital plans into theatre via polymer surgical guides. Four cases utilised additive manufacturing to fabricate titanium implants. One implant was machined from polyether ether ketone. From the literature, articles with relevant abstracts were analysed to extract design considerations. In all, 19 frequently recurring design considerations were extracted from previous publications. Nine new design considerations were extracted from the case studies – on the basis of subjective clinical evaluation. These were synthesised to produce a design considerations framework to assist clinicians with prescribing and design engineers with modelling. Promising avenues for further research are proposed.

3D-printing techniques in a medical setting: a systematic literature review

BACKGROUND

Three-dimensional (3D) printing has numerous applications and has gained much interest in the medical world. The constantly improving quality of 3D-printing applications has contributed to their increased use on patients. This paper summarizes the literature on surgical 3D-printing applications used on patients, with a focus on reported clinical and economic outcomes.

METHODS

Three major literature databases were screened for case series (more than three cases described in the same study) and trials of surgical applications of 3D printing in humans.

RESULTS

227 surgical papers were analyzed and summarized using an evidence table. The papers described the use of 3D printing for surgical guides, anatomical models, and custom implants. 3D printing is used in multiple surgical domains, such as orthopedics, maxillofacial surgery, cranial surgery, and spinal surgery. In general, the advantages of 3D-printed parts are said to include reduced surgical time, improved medical outcome, and decreased radiation exposure. The costs of printing and additional scans generally increase the overall cost of the procedure.

CONCLUSION

3D printing is well integrated in surgical practice and research. Applications vary from anatomical models mainly intended for surgical planning to surgical guides and implants. Our research suggests that there are several advantages to 3D-printed applications, but that further research is needed to determine whether the increased intervention costs can be balanced with the observable advantages of this new technology. There is a need for a formal cost-effectiveness analysis.

Low Incidence of Bone Flap Resorption After Native Bone Cranioplasty in Adults

OBJECTIVE

Cranioplasty via use of the patient's autologous bone is performed often after craniectomy procedures. Bone resorption remains a matter of concern in patients with native bone cranioplasty. The objective of this study was to evaluate the rate of native bone resorption in adults and review associated factors that may increase the risk of resorption.

METHODS

This is a single-center retrospective cohort study that assessed consecutive patients who had cranioplasty via use of the patient's native bone flap. A total of 114 patients were identified. Electronic medical records were reviewed for demographic and operative data.

RESULTS

The mean age was 51.2 years. The main indications for initial craniectomy included subarachnoid hemorrhage (SAH) in 50.9%, intracerebral hemorrhage in 17.5%, ischemic stroke in 14.9%, and trauma in 13.2% of patients. Mean interval between craniectomy and cranioplasty was 6 months. Mean follow-up after cranioplasty was 25 months. Bone resorption occurred in 3 patients (2.7%): at 6 months in a 30-year-old woman who presented with SAH followed by decompressive craniectomy and cranioplasty 3.5 months later; at 19 months in a 67-year-old female patient who presented with intracerebral hemorrhage followed by decompressive craniectomy and cranioplasty 6 months later; and at 9 months in a 50-year-old man who presented with SAH followed by craniectomy for clip ligation and cranioplasty 3 months later. Two of these patients underwent replacement of the native flap with synthetic material.

CONCLUSIONS

The rate of autologous bone flap resorption in adult patients undergoing cranioplasty is low even after a mean interval for cranioplasty of 6 months.

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.