Cranial Implants Research Articles

An assessment of residual stresses and micro-structure during single point incremental forming of commercially pure titanium used in biomedical applications

Single point incremental forming (SPIF) is a branch of incremental sheet forming where a very small portion of the sheet is deformed plastically at any moment. The highly localized point deformation is done by a simple hemispherical tool, whose path is numerically monitored by a Computer numerical control (CNC) machine, performs this progressive extremely localized deformation. Since no die is required during forming, highly customized and user-oriented sheet metal products can be manufactured employing the process. SPIF can be readily employed in the manufacturing of customized orthopaedic implants and braces, e.g., cranial implants, ankle implants, elbow and knee support braces. The forming of these sheets through SPIF would results in the generation of residual stresses in the sheet metal. With time and other physical factors, these residual stresses would be relieved resulting in dimensional inaccuracy. This inaccuracy is highly detrimental in the case of implants and highly undesirable for supporting braces. The objective of this work is to investigate, experimentally, the state and magnitude of residual stresses on commercially pure titanium grade 2 by SPIF for biomedical applications. The important process parameters: forming angle and incremental step depth are used for this investigation in the present study. The X-ray diffraction technique was used for the experimental measurements of the residual stresses. Microstructural behaviour of the final product at different incremental step depth and forming angles are also observed by EBSD (Electron backscattered diffraction) technique. The experimental findings showed the formation of increased tensile residual stresseswith an increase in incremental step depth and steepness of forming angles.

Postoperative Imaging of Complications Following Cranial Implants

A wide range of neurosurgical implants, cranioplasty materials and catheters have been developed to treat a variety of intracranial disorders. Interpretation of postoperative imaging can be challenging and confounded by postoperative changes and implant-related complications. Review of recent literature suggested that there is a paucity of data on postoperative cranial implant-related complications.If not addressed appropriately in a timely manner, these complications may cause a delay in the patient’s treatment with subsequent prolongation of hospital stay. It is therefore paramount for clinicians and radiologists to be aware of the appearance of these implant-related complications on imaging during postoperative surveillance.

Animal Origin Bioactive Hydroxyapatite Thin Films Synthesized by RF-Magnetron Sputtering on 3D Printed Cranial Implants

Ti6Al4V cranial prostheses in the form of patterned meshes were 3D printed by selective laser melting in an argon environment; using a CO2 laser source and micron-sized Ti6Al4V powder as the starting material. The size and shape of prostheses were chosen based on actual computer tomography images of patient skull fractures supplied in the framework of a collaboration with a neurosurgery clinic. After optimizations of scanning speed and laser parameters, the printed material was defect-free (as shown by metallographic analyses) and chemically homogeneous, without elemental segregation or depletion. The prostheses were coated by radio-frequency magnetron sputtering (RF-MS) with a bioactive thin layer of hydroxyapatite using a bioceramic powder derived from biogenic resources (Bio-HA). Initially amorphous, the films were converted to fully-crystalline form by applying a post-deposition thermal-treatment at 500 °C/1 h in air. The X-ray diffraction structural investigations indicated the phase purity of the deposited films composed solely of a hexagonal hydroxyapatite-like compound. On the other hand, the Fourier transform infrared spectroscopic investigations revealed that the biological carbonatation of the bone mineral phase was well-replicated in the case of crystallized Bio-HA RF-MS implant coatings. The in vitro acellular assays, performed in both the fully inorganic Kokubo’s simulated body fluid and the biomimetic organic–inorganic McCoy’s 5A cell culture medium up to 21 days, emphasized both the good resistance to degradation and the biomineralization capacity of the films. Further in vitro tests conducted in SaOs-2 osteoblast-like cells showed a positive proliferation rate on the Bio-HA RF-MS coating along with a good adhesion developed on the biomaterial surface by elongated membrane protrusions.

Fully automating fine-optics manufacture - why so tough, and what are we doing?

Precision and ultra-precision surfaces are crucial for many products – quality optics, joint & cranial implants, turbine blades, and industrial moulds & dies, to name a few. Automation in this context is distinct from standard procedures in industry, where the identical sequence of operations can be repeated over and over again. Ultraprecision tolerances may be tens to hundreds of times tighter, and this is compounded by the hundreds of diverse substrate materials in use. Even with modern computer numerically controlled (CNC) machines, skilled craftspeople are needed to plan a process-chain for a new material or geometry. Processes working at these tight tolerances, fall short of being fully-deterministic, so repeated process-metrology iterations are required. Surface-correction loops may be automated, but expert assessment should be performed at each step to check for unexpected anomalies. The ultimate goal of importing a part, processing autonomously, and delivering a finished part to an “optical” specification with no human intervention, is still a long way off. This paper describes the challenge and why it is important. It then melds together process-monitoring, psychology, artificial intelligence and robotics, to take a far-sighted view of how the ultimate goal can be realised.

Impact Optimization of 3D‐Printed Poly(methyl methacrylate) for Cranial Implants

AbstractMaterial extrusion‐based additive manufacturing, also known as fused filament fabrication (FFF) or 3D printing facilitates the fabrication of cranial implants with different materials and complex internal structures. The impact behavior plays a key role in the designing process of cranial implants. Therefore, the performance of impact tests on novel implant materials is of utmost importance. This research focuses on investigating the dependency of the infill density and pattern on the impact properties of 3D‐printed poly(methyl methacrylate) (PMMA) sandwich specimens including internal rectilinear, gyroid, and 3D‐honeycomb (3D‐HC) structures. 3D‐HC structures show higher impact forces and dissipated energies as well as dynamic stiffness values compared to rectilinear and gyroid structures at the same infill density. 70% infill 3D‐HC and 100% infill rectilinear structures prove to be most promising. In addition, two different optimization techniques to further improve the impact properties of these specimens, namely a material and a topology optimization, are applied. Topology optimization shows promising results until first damage and material optimization regarding dissipated energies. However, both are not able to outperform the 3D‐HC pattern.

S9A-04 SESSION 9A: CRANIOPLASTY THE WORLD’S FIRST, BATTERY-POWERED, LOW-PROFILE INTER-CRANIAL DEVICE (LID) PROTOTYPE CAPABLE OF REMOTE MAPPING, RECORDING, AND TELEMETRY (MRT)

Introduction: Patients with medicine-resistant epilepsy undergo invasive brain mapping and craniotomy to identify a surgical focus compatible with surgery. This requires placement of cortical/depth electrodes and then a direct trans-scalp connection to an external computer being monitored during an epilepsy monitoring unit (EMU) admission, which costs up to $238,000 per stay. Thus, given the recent advances in wireless technology and customized cranial implants, our team sought to create, design, and build the world’s first low-profile intercranial device (LID) capable of providing all necessary data via remote brain mapping, recording, and telemetry (MRT). Methods: The housing platform for the functional prototype was constructed using patent-pending technology and a clear-colored housing implant made of poly-methyl methacrylate (PMMA). The wireless connection consists of Bluetooth 5.0 telemetry and a validated, data management system. There is an external wireless charger to allow the patient to charge it daily using a headphone-like apparatus. It contains an external data storage system for retrieval of critical brain data via electroencephalography (ECOG). There is a battery life indicator located on the mobile device app, which is installed on a cellular phone solely dedicated to this project. Data rate of wireless transfer is at 1 megabyte per second. Results: Based on our experience with the first-in-human, neuromodulation-encapsulated, cranial implant case (1), our team was again successful in creating the world’s first functional prototype named the LID MRT. Upon completion, it required the size dimensions most consistent with a standard hemi-craniectomy and fully functions with respect to its wireless charging and brain signal recording (confirmed via laboratory simulation). Also, there is a visible LED light for which changes color when activated and functioning properly. Conclusion: Our team has successfully created, designed, and built the world’s first functional prototype now referred to as the LID MRT. This game-changing device is self-contained within a clear-colored, cranial implant and has the potential to shift the entire paradigm surrounding implantable neurotechnologies. Furthermore, its biocompatible design will allow for safe, long-term placement thereby providing a human brain activity database of unprecedented size.

S9A-05 SESSION 9A: CRANIOPLASTY TRANS-CRANIOPLASTY ULTRASOUND (TCU) THROUGH CLEAR-COLORED IMPLANTS: A VALIDATED PHANTOM STUDY COMPARING IMAGES VIA ULTRASOUND, CT AND MRI

Introduction: Current methods of transcranial diagnostic ultrasound imaging are limited by the skull’s acoustic properties. Craniotomy, craniectomy and cranioplasty procedures present opportunities to circumvent these limitations by substituting autologous bone with synthetic cranial implants composed of sonolucent biomaterials. This study examined the potential to image the brain using trans-cranioplasty ultrasound (TCU) through a sonolucent cranial implant. Methods: A validated brain phantom was imaged using computer tomography (CT), magnetic resonance imaging (MRI), and ultrasound without an implant. Next, for experimental comparison, TCU was performed through a sonolucent implant composed of clear poly-methyl methacrylate (PMMA). Results: All imaging modalities successfully revealed elements of the brain phantom including the bilateral ventricular system, the falx cerebri, and a deep hyperdense mass representing a brain tumor or hematoma. Additionally, ultrasound images were captured which closely resembled axial images obtained with both CT and MRI. Conclusion: The results obtained in this first-ever, pre-clinical, phantom study suggest trans-cranioplasty ultrasound (TCU) is now a viable immediate and long-term diagnostic imaging modality deserving of further clinical investigation.

Adult Cranioplasty Reconstruction With Customized Cranial Implants: Does Radiation Therapy Affect Outcomes?

Adult Cranioplasty Reconstruction With Customized Cranial Implants: Does Radiation Therapy Affect Outcomes?

S16-02 SESSION 16: PLANNING/IMAGING – PART II TRANSLATION OF PATIENT UNIQUENESS AND TREATMENT PLAN INTO PRE-SURGICAL PLANNING OF CRANIOPLASTY SURGERY USING WEB ACCESS 3D MODEL-BASED ICT TOOLS

Introduction: Although cranioplasty is considered to be a frequent and straightforward procedure, studies have shown complication rate up to 34%. While cranioplasty with autogenous bone is still regarded as the gold standard to restore cranial vault integrity, there is currently no consensus for the optimal material in the management of cranial defects. Emerging manufacturing technologies and the development of new materials offer an wide range of solutions, yet one can assume that material is chosen in regard of price, lead time, reimbursement policy and medical institutions’ preferences, but rarely according to the initial indication and the expected outcomes for such procedure, which prevent patient-specific devices from achieving large-scale utilization despite their demonstrated superiority over off-the-shelf solutions. It is therefore necessary to promote new approaches, via the development of innovative ICT tools, integrating clinical support during the pre-surgical planning, translating clinical history, treatment plan and follow-up strategy into the design of patient-specific cranial implants to achieve better clinical outcome. Methods: To transform this paradigm nowadays established in cranioplasty surgery, the first open access 3D virtual model-based ICT tools for surgeon-manufacturer communication and pre-surgical planning, serving as patient-specific implant configurator in regard of patient and pathology specificities, has been developed for the management of complex clinical cases. Results: This tool successfully grants the surgeons, via the manipulation of 3D models, the ability to describe in a more natural way, the individual solutions to realize for the treatment of a particular patient. Additionally, the surgeon’s participation in the co-creation and approval processes of the solution is being facilitated by the specification of requirements on virtual models and the systematization of the design features. Along with it, the accumulated experience of the use of patient-specific implants (PSI) is used as a clinical decision support and as a learning tool to create added value not only for patients, but for surgeons and medical institutions as well. Conclusion: This newly developed 3D virtual model-based technology, set as surgeon-manufacturer communication for PSI order and configurator, ensures correct data interpretation, product safety and functionality while taking into account the specificity of one patient for whom the device is prescribed. Those will accelerate the shift of the surgical thought paradigm towards personalized approach and undoubtedly will help achieve better clinical outcome, shorten delivery time and drop the costs of the implants used to manage rare and complex clinical cases.

Bending shape memory behaviours of carbon fibre reinforced polyurethane-type shape memory polymer composites under relatively small deformation: Characterisation and computational simulation

Shape memory polyurethanes (SMPU) have been of great interest in biomedical applications because of their unique ability to recover a primary shape by external actuation. This advantage can allow for easy suture and minimum tissue damage caused by surgery. Since SMPU suffer from low stiffness and low strength, carbon fibres have been widely used to reinforce SMPU, and their shape memory properties have been investigated using thermomechanical tensile tests. In reality, however, bending situations are more common than tensile situations, such as human skulls. In this study, carbon fibre reinforced SMPU (CF/SMPU) composites were studied as promising cranial implants that can offer shape memory properties, shape flexibility and high strength. First, the basic properties of pristine SMPU and CF/SMPU composites were characterised, including glass transition temperature (Tg), the viscosity of SMPU, the morphology of CF/SMPU, and their tensile and flexural mechanical properties. Then, a new method using rheometer was developed to study the shape memory behaviours of SMPU and CF/SMPU with three-point bending under relatively small deformations (≤1%), including flexural stress during programming and cooling, and bending recovery force during shape recovery. Finally, due to the invisibility of recovery process that was conducted in an enclosed temperature-controlling chamber of rheometer, the finite element method (FEM) was used to simulate the bending recovery test. The results showed carbon fibres significantly enhanced the mechanical properties (Young's modulus and flexural modulus) of SMPU. In terms of bending shape recovery, compared to pristine SMPU, CF/SMPU composites obtained substantially higher flexural stress during programming and cooling processes, and larger, more stable recovery force during recovery. The FEM results consolidated the peak recovery force of SMPU and the continuously growing recovery force of CF/SMPU as the temperature increased. Our findings on the improved mechanical and shape memory properties can provide a solid foundation for the potential applications of CF/SMPU composites as cranial implants.

Evaluation of Structural and Biomechanical Characterization of Implant for Cranial Restoration

The objective this research was to investigate the biomechanical properties of various structures and thicknesses of implants for cranial restoration. A three-dimensional (3D) printing (3DP) technique has been applied in factories for several decades, but it was only recently introduced to the dental field less than 10 years ago. The structures of pre-shaped cranial mesh implants are critical factors for clinical applications. Many previous studies used finite element models to investigate for implants, but few examined a 3D model for pre-shaped cranial mesh implants with different structures and thicknesses. 3D cranial models were reconstructed using computer tomography to simulate preshaped cranial mesh implants under physical impacts. Data indicated that the stress significantly decreased when implants with greater thicknesses were used. Moreover, the implant with a circular structure created a relatively smaller stress that was approximately 7% lower compared to the implant with a triangular structure. As described above, the results of the present study demonstrate that 3DP-Ti is a reliable material of implants for cranial restoration.

Cost-Effective Technique of Fabrication of Polymethyl Methacrylate Based Cranial Implant Using Three-Dimensional Printed Moulds and Wax Elimination Technique

Cranioplasty is one of the oldest known neurosurgical procedure performed. Many materials have been used for cranioplasty since ages. Polymethyl methacrylate (PMMA) has become the workhorse for fabrication of cranial implants since World War II in cases where autologous bone is not available or cannot be harvested. The aim of the present study is to present author's experience in the management of cranioplasty using acrylic implants fabricated using 2 different techniques. The author conducted a retrospective analysis of patients with extensive skull defects undergoing acrylic cranioplasties between October 2016 and January 2018. The surgical results were classified based on surgical time, blood loss, and the 3 scales of patient satisfaction, improvement of facial symmetry, and need for additional surgery along with the rate of wound complications. Thirty patients underwent cranioplasty with PMMA-based implants, whether fabricated using alginate impression technique (56.67%) or fabricated using 3-dimensional (3D) printed patient-specific moulds (43.33%). Complications included infection (13.3%). The authors considered the craniofacial aesthetics based on patient satisfaction excellent (69%) with the degree of improvement of craniofacial symmetry satisfactory (92.3%), and 1 patient requiring resurgery in alginate impression technique fabricated implants. The author recommends a unique technique for fabrication of PMMA-based implants using 3D printed moulds to achieve a better fitting implant and highly cosmetic outcome for cranioplasty at affordable cost.

Biomechanical performance of cranial implants with different thicknesses and material properties: A finite element study

This study investigated the effect of implant thickness and material on deformation and stress distribution within different components of cranial implant assemblies. Using the finite element method, two cranial implants, differing in size and shape, and thicknesses (1, 2, 3 and 4 mm, respectively), were simulated under three loading scenarios. The implant assembly model included the detailed geometries of the mini-plates and micro-screws and was simulated using a sub-modeling approach. Statistical assessments based on the Design of Experiment methodology and on multiple regression analysis revealed that peak stresses in the components are influenced primarily by implant thickness, while the effect of implant material is secondary. On the contrary, the implant deflection is influenced predominantly by implant material followed by implant thickness. The highest values of deformation under a 50 N load were observed in the thinnest (1 mm) Polymethyl Methacrylate implant (Small defect: 0.296 mm; Large defect: 0.390 mm). The thinnest Polymethyl Methacrylate and Polyether Ether Ketone implants also generated stresses in the implants that can potentially breach the materials' yield limit. In terms of stress distribution, the change of implant thickness had a more significant impact on the implant performance than the change of Young's modulus of the implant material. The results indicated that the stresses are concentrated in the locations of fixation; therefore, the detailed models of mini-plates and micro-screws implemented in the finite element simulation provided a better insight into the mechanical performance of the implant-skull system.

Refinement of a chronic cranial window implant in the rat for longitudinal in vivo two\u2013photon fluorescence microscopy of neurovascular function

Longitudinal studies using two–photon fluorescence microscopy (TPFM) are critical for facilitating cellular scale imaging of brain morphology and function. Studies have been conducted in the mouse due to their relatively higher transparency and long term patency of a chronic cranial window. Increasing availability of transgenic rat models, and the range of established behavioural paradigms, necessitates development of a chronic preparation for the rat. However, surgical craniotomies in the rat present challenges due to craniotomy closure by wound healing and diminished image quality due to inflammation, restricting most rat TPFM experiments to acute preparations. Long-term patency is enabled by employing sterile surgical technique, minimization of trauma with precise tissue handling during surgery, judicious selection of the size and placement of the craniotomy, diligent monitoring of animal physiology and support throughout the surgery, and modification of the home cage for long-term preservation of cranial implants. Immunohistochemical analysis employing the glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule-1 (Iba-1) showed activation and recruitment of astrocytes and microglia/macrophages directly inferior to the cranial window at one week after surgery, with more diffuse response in deeper cortical layers at two weeks, and amelioration around four weeks post craniotomy. TPFM was conducted up to 14 weeks post craniotomy, reaching cortical depths of 400 µm to 600 µm at most time-points. The rate of signal decay with increasing depth and maximum cortical depth attained had greater variation between individual rats at a single time-point than within a rat across time.

Sonolucent Cranial Implants: Cadaveric Study and Clinical Findings Supporting Diagnostic and Therapeutic Transcranioplasty Ultrasound.

Background:Previously, sonographic evaluation of the intracranial contents was limited to intraoperative use following bone flap removal, with placement of the probe directly on the cortical surface or through a transsulcal tubular retractor. Cranioplasty with sonolucent implants may represent a postoperative window into the brain by allowing ultrasound to serve as a novel bedside imaging modality. The potential sonolucency of various commonly used cranial implant types was examined in this study.Methods:A 3-phase study was comprised of cadaveric evaluation of transcranioplasty ultrasound (TCU) with cranioplasty implants of varying materials, intraoperative TCU during right-sided cranioplasty with clear implant made of poly-methyl-methacrylate (PMMA), and bedside TCU on postoperative day 5 after cranioplasty.Results:The TCU through clear PMMA, polyether-ether-ketone, and opaque PMMA cranial implants revealed implant sonoluceny, in contrast to autologous bone and porous-polyethylene. Intraoperative ultrasound via the clear PMMA implant in a single patient revealed recognizable ventricular anatomy. Furthermore, postoperative bedside ultrasound in the same patient revealed comparable ventricular anatomy and a small epidural fluid collection corresponding to that visualized on an axial computed tomography scan.Conclusion:Sonolucent cranial implants, such as those made of clear PMMA, hold great promise for enhanced diagnostic and therapeutic applications previously limited by cranial bone. Furthermore, as functional cranial implants are manufactured with implantable devices housed within clear PMMA, the possibility of utilizing ultrasound for real-time surveillance of intracranial pathology becomes much more feasible.

Dural Reconstruction With Autologous Rectus Fascia: A New Technique for Addressing Large-Sized Defects During Cranioplasty.

Patients requiring cranioplasty reconstruction with customized cranial implants may unexpectedly present with cerebrospinal fluid (CSF) leaks and durotomies following previous neurosurgical procedures. As such, multiple factors influence the type of dural reconstruction chosen at this time, which are essential for achieving long-term success. Overall, the most common material used for duraplasty is currently an "off-the-shelf" xenograft construct. However, some believe that they are not suitable for large-sized defects and accompany a higher incident of complications. Therefore, based on our success and experience with scalp augmentation using rectus fascia grafts, the authors herein present our preliminary experience with duraplasty using autologous rectus fascia grafts (ARFGs). A retrospective review of our database, consisting of 437 cranial reconstructions from 2012 to 2017, was performed under institutional review board approval. Selection criteria included all adult patients (n = 6) requiring dural reconstruction (duraplasty) with ARF grafting for an active CFS leak with concomitant skull defect. Cadaver study and patient illustrations are also presented to demonstrate clinical applicability. All outcomes, including complications, were reviewed and are presented here. A total of 6 patients underwent autologous duraplasty with either unilateral or bilateral ARFGs. All patients (6/6) of large-sized (>3 cm) defect repair with ARFGs were indicated for repair of secondary CSF leaks following previous craniotomy by neurosurgery. To date, none have demonstrated recurrent leaking and/or dura-related complications. At this time, all 6 patients were reconstructed using customized cranial implants with a mean follow-up of 10 months. Based on our preliminary experience presented here, the use of rectus fascia grafts for autologous dural reconstruction appears to be both safe and reliable. This new technique adds another tool to the neurosurgical armamentarium by reducing the additional risk of "off-the-shelf" dural substitutes.

Cranioplasty after craniectomy in pediatric patients-a systematic review.

Complications following cranioplasty with either autografts or cranial implants are commonly reported in pediatric patients. However, data regarding cranioplasty strategies, complications and long-term outcomes are not well described. This study systematically reviews the literature for an overview of current cranioplasty practice in children. A systematic review of articles published from inception to July 2018 was performed. Studies were included if they reported the specific use of cranioplasty materials following craniectomy in patients younger than 18 years of age, and had a minimum follow-up of at least 1 year. Twenty-four manuscripts, describing a total of 864 cranioplasty procedures, met the inclusion criteria. The age of patients in this aggregate ranged from 1 month to 20 years and the weighted average was 8.0 years. The follow-up ranged from 0.4 months to 18 years and had a weighted average of 40.4 months. Autologous bone grafts were used in 484 cases (56.0%). Resorption, infection and/or hydrocephalus were the most frequently mentioned complications. In this aggregate group, 61 patients needed a revision cranioplasty. However, in 6/13 (46%) papers studying autologous cranioplasties, no data was provided on resorption, infection and revision cranioplasty rates. Cranial implants were used in 380 cases (44.0%), with custom-made porous hydroxyapatite being the most commonly used material (100/380, 26.3%). Infection and migration/fracturing/loosening were the most frequently documented complications. Eleven revision cranioplasties were reported. Again, no data was reported on infection and revision cranioplasty rates, in 7/16 (44%) and 9/16 (56%) of papers, respectively. Our systematic review illuminates that whether autografts or cranial implants are used, postcranioplasty complications are quite common. Beyond this, the existing literature does not contain well documented and comparable outcome parameters, suggesting that prospective, long-term multicenter cohort studies are needed to be able to optimize cranioplasty strategies in children who will undergo cranioplasty following craniectomy.

Force and thickness prediction with FEA of the cranial implants manufactured through SPIF

Single point incremental forming is a process which is primarily used for prototyping, small series production and unique parts. This procedure shows a high potential in the development of complex shape parts where the time of the execution does not play an important role. Among the applications of this process are the execution of various medical prostheses, such as: knee prostheses and cranial implants. The aim of this paper is to determine the forces which take place during the manufacture process of an cranial implant, as well as the thinning of the material through the help of finite element analysis. After the numerical simulation, from the results obtained it is possible to observe the behaviour of the material at different forces which appear during the deformation process. In addition, in this paper will be presented considerations about the thinning of the material used for the cranial implant.

Cranioplasties following craniectomies in children-a multicenter, retrospective cohort study.

Complications following pediatric cranioplasty after craniectomy with either autologous bone flaps or cranial implants are reported to be common, particularly bone flap resorption. However, only sparse data are available regarding cranioplasty strategies, complications, and outcomes. This manuscript describes a Canadian-Dutch multicenter pediatric cohort study with autografts and cranial implant cranioplasties following craniectomies for a variety of indications. The study included all children (< 18years) who underwent craniectomy and subsequent cranioplasty surgeries from 2008 to 2014 (with a minimum of 1-year follow-up) at four academic hospitals with a dedicated pediatric neurosurgical service. Data were collected regarding initial diagnosis, age, time interval between craniectomy and cranioplasty, bone flap storage method, type of cranioplasty for initial procedure (and redo if applicable), and the postoperative outcome including surgical site infection, wound breakdowns, bone flap resorption, and inadequate fit/disfigurement. Sixty-four patients (46 males, average age 9.7 ± 5.5years) were eligible for inclusion, with mean follow-up of 82.3 ± 31.2months after craniectomy. Forty cranioplasties (62.5%) used autologous bone re-implant, 23 (57.5%) of which showed resorption. On average, resorption was documented at 434days (range 62-2796days) after reimplantation. In 20 cases, a revision cranioplasty was needed. In 24 of the post-craniectomy cases (37.5%), a cranial implant was used with one of ten different implant types. Implant loosening prompted a complete revision cranioplasty in 2 cases (8.3%). Cranial implants were associated with low morbidity and lower reoperation dates compared to the autologous cranioplasties. The most prominent finding in this multicenter cohort study was that bone flap resorption in children remains a common and widespread problem following craniectomy. Cranioplasty strategies varied between centers and evolved over time within centers. Cranial implants were associated with low morbidity and low reoperation rates. Still, longer term and prospective multicenter cohort studies are needed to optimize cranioplasty strategies in children after craniectomies.

Cranioplasty with Porous Hydroxyapatite Custom-Made Bone Flap: Results from a Multicenter Study Enrolling 149 Patients Over 15 Years

Despite the mixed evidence regarding the effect of decompressive craniectomy in terms of outcome, a tremendous increase in related reports has been observed in the last years. Cranioplasty plays a key role in restoring function and anatomy of the cranial vault. Considering that cranioplasty is not exempt from risks, the identification of the safest technique becomes crucial to achieve better patients' recovery. Porous hydroxyapatite (PHA) has received growing attention for its potential in bony integration. Here we report a multicenter prospective follow-up analysis of 149 patients who underwent cranioplasty with PHA prostheses. In particular, we focus on the incidence of adverse events and implant removal. From January 2001 to December 2015 we conducted a prospective multicenter study of 149 patients who underwent cranioplasty with custom-made PHA flaps after decompressive craniectomy for several reasons. The endpoints were the incidence of adverse events after cranioplasty and of related implant removal. 66 patients (44%) were treated within 6 months from decompression, and only 2 patients had a bifrontal bilateral reconstruction. Of those, 25 patients reported complications (16.8%), and 9 of them (6% of the whole case series) required removal of the prosthesis. The only significant factor predicting cranioplasty removal was a previous infection. Hydroxyapatite for cranial implants is fully comparable to other heterologous materials. It has a biologic potential of bony integration. The risk of explants seems to be significantly higher in second-line patients, data not shown in previous studies.