Translucent Customized Cranial Implants Made of Clear Polymethylmethacrylate: An Early Outcome Analysis of 55 Consecutive Cranioplasty Cases

Neuroplastic Surgery Principles of Computerized Surgical Planning in Complex Cranioplasty Reconstruction

This article explores the evolution and implementation of three-dimensional (3D) models and Computerized Surgical Planning (CSP) for complex cranioplasty reconstruction and the advances in neuroplastic surgery principles for improved surgical outcomes. Over recent years, CSP has revolutionized the field by employing detailed medical imaging to enhance the accuracy and efficacy of 3D models and for the creation of customized cranial implants (CCIs). The study discusses the advancements of solid alloplastic implants to the future of implants with sophisticated and integrated neurotechnology to treat or enhance patient outcomes. CSP can be used to identify and mitigate complications that can occur within cranioplasty reconstruction and to create CCIs to address the postoperative challenge of temporal hollowing. Despite the promising advancements, the article acknowledges the current limitations of CSP, including cost and technological accessibility, and proposes future directions for research and development. The findings suggest that with further improvements in imaging, biomaterials, and manufacturing techniques, CSP in neuroplastic surgery and other specialties will continue to significantly enhance the precision and personalized care of cranioplasty reconstruction.

High-Density Porous Polyethylene Implant Cranioplasty: A Systematic Review of Outcomes

Porous polyethylene has been widely used in craniofacial reconstruction due to its biomechanical properties and ease of handling. The objective of this study was to perform a systematic review of the literature to summarize outcomes utilizing high-density porous polyethylene (HDPP) implants in cranioplasty. A literature search of PubMed, Cochrane Library, and Scopus databases was conducted to identify original studies with HDPP cranioplasty from inception to March 2023. Non-English articles, commentaries, absent indications or outcomes, and nonclinical studies were excluded. Data on patient demographics, indications, defect size and location, outcomes, and patient satisfaction were extracted. Summary statistics were calculated using weighted averages based on the available reported data. A total of 1089 patients involving 1104 cranioplasty procedures with HDPP were identified. Patients' mean age was 44.0 years (range 2 to 83 y). The mean follow-up duration was 32.0 months (range 2 wk to 8 y). Two studies comprising 17 patients (1.6%) included only pediatric patients. Alloplastic cranioplasty was required after treatment of cerebrovascular diseases (50.9%), tumor excision (32.0%), trauma (11.4%), trigeminal neuralgia/epilepsy (3.4%), and others such as abscesses/cysts (1.4%). The size of the defect ranged from 3 to 340 cm 2 . An overall postoperative complication rate of 2.3% was identified, especially in patients who had previously undergone surgery at the same site. When data were available, contour improvement and high patient satisfaction were reported in 98.8% and 98.3% of the patients. HDPP implants exhibit favorable outcomes for reconstruction of skull defects. Higher complication rates may be anticipated in secondary cranioplasty cases.

Functional ultrasound imaging of human brain activity through an acoustically transparent cranial window

Visualization of human brain activity is crucial for understanding normal and aberrant brain function. Currently available neural activity recording methods are highly invasive, have low sensitivity, and cannot be conducted outside of an operating room. Functional ultrasound imaging (fUSI) is an emerging technique that offers sensitive, large-scale, high-resolution neural imaging; however, fUSI cannot be performed through the adult human skull. Here, we used a polymeric skull replacement material to create an acoustic window compatible with fUSI to monitor adult human brain activity in a single individual. Using an in vitro cerebrovascular phantom to mimic brain vasculature and an in vivo rodent cranial defect model, first, we evaluated the fUSI signal intensity and signal-to-noise ratio through polymethyl methacrylate (PMMA) cranial implants of different thicknesses or a titanium mesh implant. We found that rat brain neural activity could be recorded with high sensitivity through a PMMA implant using a dedicated fUSI pulse sequence. We then designed a custom ultrasound-transparent cranial window implant for an adult patient undergoing reconstructive skull surgery after traumatic brain injury. We showed that fUSI could record brain activity in an awake human outside of the operating room. In a video game "connect the dots" task, we demonstrated mapping and decoding of task-modulated cortical activity in this individual. In a guitar-strumming task, we mapped additional task-specific cortical responses. Our proof-of-principle study shows that fUSI can be used as a high-resolution (200 μm) functional imaging modality for measuring adult human brain activity through an acoustically transparent cranial window.

Patient Satisfaction and Radiologic Assessability After Treatment of Complex Skull Defects With a Custom-Made Cranioplasty From a Thin Titanium Sheet

OBJECTIVE

The cosmetically good coverage of skull defects is a challenge in neurosurgical clinics. In addition, the skull treated with implants and the underlying structures must remain radiologically assessable. In this examination, the postoperative courses of patients after implantation of CranioTop is described. Digital x-ray, computed tomography, and magnetic resonance images after implantation of CranioTop were evaluated with regard to their assessability.

MATERIALS AND METHODS

Between 2018 and 2020, 23 titanium cranioplasties (CranioTop) were implanted to 21 patients. The intraoperative handling, the accuracy of fit, the healing process, the cosmetic result and the physical condition of the patients were examined. In addition, digital x-rays, magnetic resonance imaging, and computed tomography scans of the cranium supplied with CranioTop were examined.

RESULTS

The evaluation showed good to very good results regarding patients' satisfaction. There were no severe complications; thirteen patients found the cosmetic result very good; 8 patients assessed the cosmetic result as good. Because of the low thickness and density of the CranioTop plastic there was only low formation of radial stripe artifacts (streaking) and susceptibility artifacts. The assessment of digital x-ray, computed tomography, and magnetic resonance imaging images is possible after implantation of CranioTop.

CONCLUSION

The patients treated with CranioTop showed a high level of satisfaction with regard to the cosmetic result and their physical condition. Furthermore, the cranium supplied with CranioTop remains well assessable in radiologic imaging with only slight limitations in magnetic resonance imaging.

Transcranioplasty Ultrasonography Through a Sonolucent Prosthesis: A Review of Feasibility, Safety, and Benefits

Data on the effectiveness of transcranioplasty ultrasonography through sonolucent cranioplasty (SC) are new and heterogeneous. We performed the first systematic literature review on SC. Ovid Embase, Ovid Medline, and Web of Science Core Collection were systematically searched and published full text articles detailing new use of SC for the purpose of neuroimaging were critically appraised and extracted. Of 16 eligible studies, 6 reported preclinical research and 12 reported clinical experiences encompassing 189 total patients with SC. The cohort age ranged from teens to 80s and was 60% (113/189) female. Sonolucent materials in clinical use are clear PMMA (polymethylmethacrylate), opaque PMMA, polyetheretherketone, and polyolefin. Overall indications included hydrocephalus (20%, 37/189), tumor (15%, 29/189), posterior fossa decompression (14%, 26/189), traumatic brain injury (11%, 20/189), bypass (27%, 52/189), intracerebral hemorrhage (4%, 7/189), ischemic stroke (3%, 5/189), aneurysm and subarachnoid hemorrhage (3%, 5/189), subdural hematoma (2%, 4/189), and vasculitis and other bone revisions (2%, 4/189). Complications described in the entire cohort included revision or delayed scalp healing (3%, 6/189), wound infection (3%, 5/189), epidural hematoma (2%, 3/189), cerebrospinal fluid leaks (1%, 2/189), new seizure (1%, 2/189), and oncologic relapse with subsequent prosthesis removal (<1%, 1/189). Most studies utilized linear or phased array ultrasound transducers at 3-12 MHz. Sources of artifact on sonographic imaging included prosthesis curvature, pneumocephalus, plating system, and dural sealant. Reported findings were mainly qualitative. We, therefore, suggest that future studies should collect quantitative measurement data during transcranioplasty ultrasonography to validate imaging techniques.

A window to the brain: ultrasound imaging of human neural activity through a permanent acoustic window

Recording human brain activity is crucial for understanding normal and aberrant brain function. However, available recording methods are either highly invasive or have relatively low sensitivity. Functional ultrasound imaging (fUSI) is an emerging technique that offers sensitive, large-scale, high-resolution neural imaging. However, fUSI cannot be performed through adult human skull. Here, we use a polymeric skull replacement material to create an acoustic window allowing ultrasound to monitor brain activity in fully intact adult humans. We design the window through experiments in phantoms and rodents, then implement it in a participant undergoing reconstructive skull surgery. Subsequently, we demonstrate fully non-invasive mapping and decoding of cortical responses to finger movement, marking the first instance of high-resolution (200 μm) and large-scale (50 mmx38 mm) brain imaging through a permanent acoustic window.

Establishing proof of concept for sonolucent cranioplasty and point of care ultrasound imaging after posterior fossa decompression for Chiari malformation

BACKGROUND

Evaluation after posterior fossa decompression for Chiari malformation can require repeated imaging, particularly with persistent symptoms. Typically, CT or MRI is used. However, CT carries radiation risk and MRI is costly. Ultrasound is an inexpensive, radiation-free, point-of-care modality that has, thus far, been limited by intact skull and traditional cranioplasty materials. Ultrasound also allows for imaging in different head positions and body postures, which may lend insight into cause for persistent symptoms despite adequate decompression on traditional neutral static CT or MRI. We evaluate safety and feasibility of ultrasound as a post-operative imaging modality in patients reconstructed with sonolucent cranioplasty during posterior fossa decompression for Chiari malformation.

METHODS

Outcomes were analyzed for 26 consecutive patients treated with a Chiari-specific sonolucent cranioplasty. This included infection, need for revision, CSF leak, and pseudomeningocele. Ultrasound was performed point-of-care in the outpatient clinic by the neurosurgery team to assess feasibility.

RESULTS

In eight months mean follow up, there were no surgical site infections or revisions with this novel sonolucent cranioplasty. Posterior fossa anatomy was discernable via transcutaneous ultrasound obtained point-of-care in the clinic setting at follow up visits.

CONCLUSION

We demonstrate proof of concept for ultrasound as a post-operative imaging modality after posterior fossa decompression for Chiari malformation. With further investigation, ultrasound may prove to serve as an alternative to CT and MRI in this patient population, or as an adjunct to provide positional and dynamic information. Use of sonolucent cranioplasty is safe. This technique deserves further study.

Application of mesenchymal stem cell sheet for regeneration of craniomaxillofacial bone defects

Bone defects are among the most common damages in human medicine. Due to limitations and challenges in the area of bone healing, the research field has turned into a hot topic discipline with direct clinical outcomes. Among several available modalities, scaffold-free cell sheet technology has opened novel avenues to yield efficient osteogenesis. It is suggested that the intact matrix secreted from cells can provide a unique microenvironment for the acceleration of osteoangiogenesis. To the best of our knowledge, cell sheet technology (CST) has been investigated in terms of several skeletal defects with promising outcomes. Here, we highlighted some recent advances associated with the application of CST for the recovery of craniomaxillofacial (CMF) in various preclinical settings. The regenerative properties of both single-layer and multilayer CST were assessed regarding fabrication methods and applications. It has been indicated that different forms of cell sheets are available for CMF engineering like those used for other hard tissues. By tackling current challenges, CST is touted as an effective and alternative therapeutic option for CMF bone regeneration.

Sonolucent Cranioplasty in Extracranial to Intracranial Bypass Surgery: Early Multicenter Experience of 44 Cases

BACKGROUND

The new sonolucent cranioplasty implant (clear polymethyl methacrylate, PMMA) adds functionality besides surgical reconstruction. One possible application uses the transcranioplasty ultrasound (TCUS) technique after PMMA cranioplasty to assess graft patency of extracranial-intracranial (EC-IC) bypass procedures.

OBJECTIVE

To report our early multicenter experience.

METHODS

This is a multicenter analysis of consecutive EC-IC bypass patients from 5 US centers (2019-2022) with closure postbypass using PMMA implant.

RESULTS

Forty-four patients (median age 53 years, 68.2% females) were included. The most common indication for bypass was Moyamoya disease/syndrome (77.3%), and superficial temporal artery to middle cerebral artery bypass was the most common procedure (79.5%). Pretreatment modified Rankin Scales of 0 and 1 to 2 were noted in 11.4% and 59.1% of patients, respectively. Intraoperative imaging for bypass patency involved a combination of modalities; Doppler was the most used modality (90.9%) followed by indocyanine green and catheter angiography (86.4% and 61.4%, respectively). Qualitative TCUS assessment of graft patency was feasible in all cases. Postoperative inpatient TCUS confirmation of bypass patency was recorded in 56.8% of the cases, and outpatient TCUS surveillance was recorded in 47.7%. There were no cases of bypass failure necessitating retreatment. Similarly, no implant-related complications were encountered in the cohort. Major complications requiring additional surgery occurred in 2 patients (4.6%) including epidural hematoma requiring evacuation (2.3%) and postoperative surgical site infection (2.3%) that was believed to be unrelated to the implant.

CONCLUSION

This multicenter study supports safety and feasibility of using sonolucent PMMA implant in EC-IC bypass surgery with the goal of monitoring bypass patency using TCUS.

First Experience With Postoperative Transcranial Ultrasound Through Sonolucent Burr Hole Covers in Adult Hydrocephalus Patients

BACKGROUND

Managing patients with hydrocephalus and cerebrospinal fluid (CSF) disorders requires repeated head imaging. In adults, it is typically computed tomography (CT) or less commonly magnetic resonance imaging (MRI). However, CT poses cumulative radiation risks and MRI is costly. Ultrasound is a radiation-free, relatively inexpensive, and optionally point-of-care alternative, but is prohibited by very limited windows through an intact skull.

OBJECTIVE

To describe our initial experience with transcutaneous transcranial ultrasound through sonolucent burr hole covers in postoperative hydrocephalus and CSF disorder patients.

METHODS

Using cohort study design, infection and revision rates were compared between patients who underwent sonolucent burr hole cover placement during new ventriculoperitoneal shunt placement and endoscopic third ventriculostomy over the 1-year study time period and controls from the period 1 year before. Postoperatively, trans-burr hole ultrasound was performed in the clinic, at bedside inpatient, and in the radiology suite to assess ventricular anatomy.

RESULTS

Thirty-seven patients with sonolucent burr hole cover were compared with 57 historical control patients. There was no statistically significant difference in infection rates between the sonolucent burr hole cover group (1/37, 2.7%) and the control group (0/57, P = .394). Revision rates were 13.5% vs 15.8% (P = 1.000), but no revisions were related to the burr hole or cranial hardware.

CONCLUSION

Trans-burr hole ultrasound is feasible for gross evaluation of ventricular caliber postoperatively in patients with sonolucent burr hole covers. There was no increase in infection rate or revision rate. This imaging technique may serve as an alternative to CT and MRI in the management of select patients with hydrocephalus and CSF disorders.

Neuroimaging through Sonolucent Cranioplasty: A Systematic Scoping Review Protocol

Cranioplasty is a neurosurgical procedure in which the skull bone is repaired after craniectomy. Recently, studies have suggested that sonolucent synthetic materials are safe and useful for cranioplasty. Sonolucent cranioplasty (SC) implants provide unprecedented opportunity in adult neurosurgery to monitor neuroanatomy, assess hemodynamics, view devices located within the implant, and conduct focused ultrasound treatments. Current research on SC includes proof-of-concept cadaveric studies, patient-related safety and feasibility studies, and case series demonstrating transcranioplasty ultrasonography (TCUS). The purpose of this protocol is to investigate the current literature on SC use and outcomes in TCUS. We will perform a systematic literature search following PRISMA-ScR guidelines. The search will be conducted using Ovid Embase, Ovid Medline, and Web of Science Core Collection databases. Titles, abstracts, and full texts will be screened. Joanna Briggs Institute critical appraisal tools will be utilized. Data extraction points will include subject characteristics, SC implant characteristics, ultrasound characteristics, and sonographic findings. These findings will provide a comprehensive review of the literature on sonolucent cranioplasty and directions for future research.

Automated Implant Resizing for Single-Stage Cranioplasty

Patient-specific customized cranial implants (CCIs) are designed to fill the bony voids in the cranial and craniofacial skeleton. The current clinical approach during single-stage cranioplasty involves a surgeon modifying an oversized CCI to fit a patient's skull defect. The manual process, however, can be imprecise and time-consuming. This paper presents an automated surgical workflow with a robotic workstation for intraoperative CCI modification that provides higher resizing accuracy compared to the manual approach. We proposed a 2-scan method for intraoperative patient-to-CT registration using reattachable fiducial markers to address the registration issue caused by the clinical draping requirement. First, the draped defected skull was 3D scanned and registered to the CT space using our proposed 2-scan registration method. Next, our algorithm generates a robot cutting toolpath based on the 3D defect model. The robot then performs automatic 3D scanning to localize the implant and resizes the implant to match the cranial defect. We evaluated the implant resizing accuracy of the proposed paradigm against the resizing accuracy of the manual approach by an expert surgeon on two plastic skulls and two cadavers. The evaluation results showed that our system was able to decrease the bone gap distance by more than 60% and 30% on plastic skulls and cadavers respectively compared to the manual approach, indicating lower risk of post-surgical complication and better aesthetic restoration.

Nanoparticle-Mediated Angiotensin-(1-9) Drug Delivery for the Treatment of Cardiac Hypertrophy

Ang-(1-9) peptide is a bioactive vasodilator peptide that prevents cardiomyocyte hypertrophy in vitro and in vivo as well as lowers blood pressure and pathological cardiovascular remodeling; however, it has a reduced half-life in circulation, requiring a suitable carrier for its delivery. In this work, hybrid nanoparticles composed of polymeric nanoparticles (pNPs) based on Eudragit^® E/Alginate (EE/Alg), and gold nanospheres (AuNS), were developed to evaluate their encapsulation capacity and release of Ang-(1-9) under different experimental conditions. Hybrid pNPs were characterized by dynamic light scattering, zeta potential, transmission and scanning electron microscopy, size distribution, and concentration by nanoparticle tracking analysis. Nanometric pNPs, with good polydispersity index and colloidally stable, produced high association efficiency of Ang-(1-9) and controlled release. Finally, the treatment of neonatal cardiomyocytes in culture with EE/Alg/AuNS 2% + Ang-(1-9) 20% pNPs decreased the area and perimeter, demonstrating efficacy in preventing norepinephrine-induced cardiomyocyte hypertrophy. On the other hand, the incorporation of AuNS did not cause negative effects either on the cytotoxicity or on the association capacity of Ang-(1-9), suggesting that the hybrid carrier EE/Alg/AuNS pNPs could be used for the delivery of Ang-(1-9) in the treatment of cardiovascular hypertrophy.

Load-Bearing Capacity and Design Advantages of a Custom-Made, Thin Pure-Titanium Cranioplasty (CranioTop)

BACKGROUND

Adequate and stable coverage of cranial contour and continuity defects of any origin is a common challenge in neurosurgical clinics. This study presents the results of investigations concerning the mechanical load-bearing capacity and design advantages of custom-made implants made from a thin, pure-titanium sheet (CranioTop) (CLinstruments, Attendorn, Germany) for covering complex cranial defects.

METHODS

In 9 test series, the stability of three differently shaped and sized thin titanium sheet implants was tested using vertical, uniaxial compression with 3 different compression stamps, to investigate the behaviour of these implants in relation to punctiform as well as planar forces.

RESULTS

All 9 model implants showed elastic behavior in the synchronously recorded force/displacement diagrams at an impression of up to 2 mm. The forces at 2 mm deformation were between 170.1 and 702.7 Newton.

CONCLUSION

Cranioplasty using CranioTop is a stable procedure for covering skull defects, even those of large dimensions. An added advantage is the significant reduction in effort required to prepare the area of the bone margins compared to other current techniques of cranioplasty.