Long-term results following titanium cranioplasty of large skull defects

On the RF safety of titanium mesh head implants in 7 T MRI systems: an investigation

PURPOSE

Patients undergoing craniofacial surgery for skull reconstruction may have titanium mesh implants. The safety risks related to 7 T MRI with these patients are not well understood. This study investigates the RF heating of titanium mesh head implants at 7 T.

METHODS

A simulation model for a 7 T birdcage head coil was developed and validated againstB 1 + $$ \left|{B}_1^{+}\right| $$ , 1 g-averaged specific absorption rate (SAR), and temperature measurements in the presence of a titanium mesh. Various mesh sizes and shapes at different angular positions were simulated to determine the worst-case scenario in a spherical phantom in addition to the effect of rounding the mesh edges. Full-wave electromagnetic and bioheat thermal simulations were conducted on anatomical human models.

RESULTS

Preliminary results indicate an increase in the local SAR near the meshes depending on the shape, size, and location. The maximum absolute temperatures in the head were, on average, around 38.2°C after 15 min of RF power exposure, corresponding to 3.2 W/kg whole-head SAR without a titanium mesh implant. The maximum absolute temperatures did not significantly change after introducing the titanium mesh implants, and the highest temperature was 38.4°C, observed near the cerebellum and the facial muscles. The maximum local increase in temperature was observed at the vicinity of the mesh as 2.8°C. Finally, it was shown that large mesh implants can negatively impactB 1 + $$ \left|{B}_1^{+}\right| $$ field.

CONCLUSIONS

Small rounded titanium mesh head implants can be generally safe for 7 T MRI scans under the standard guidelines. Avoiding sharp corners and edges may reduce the chances of RF safety risks.

Customized 3D-printed Poly ether ether ketone cranial implant for cranioplasty of skull defects

Cranioplasty become one of the common surgeries in the neurosurgical field. The complex configuration of the cranium makes the bone reconstruction of the skull defects a challenging procedure. While the patient's own bone flap is the best option, other materials such as titanium and Poly ether ether Ketone (PEEK) were used for cranioplasty when the autogenous flap of the patient is unavailable. Recently, customized 3D printing implants were developed for cranioplasty with favorable outcomes. In this study, we evaluated the outcome of customized 3-dimentional (3D)-printed PEEK implant cranioplasty for reconstructing skull defects, especially large ones. We report a series of 27 patients whose skull defects were reconstructed by a customized 3D-printed PEEK implants. Demographic data and postoperative clinical and imaging findings were reviewed. We analyzed the complications, clinical and aesthetic outcomes during mid-term follow-up. During the surgery, all the implants were perfectly fitted in the skull defect without any major modification. Aesthetic results were satisfactory in 74.1% of patients. 4 patients (14.8%) had complications, including 3 deep cranial infections (11.1%) and one extradural hematoma (3,7%). In 2 patients (7.4%), the implants were removed due to infection. Therefore, when autologous bone is unavailable or, in selected cases with large or complex skull defects, customized 3D-printed PEEK implants could be a proper option to reconstruct these defects.

Health-related quality of life following cranioplasty - a systematic review

Cranioplasty is a neurosurgical procedure that repairs a defect in the skull Coupled with the underlying pathology cranioplasty associated morbidity can have a large impact on patient quality of life, which is often poorly explored. The objective of this systematic review was to identify patient-reported outcomes evaluating health-related quality of life following cranioplasty. The review protocol was registered on PROSPERO (CRD42021251543) and a systematic review was conducted in accordance with the PRISMA statement. PubMed, Embase, CINAHL Plus, and the Cochrane databases were searched from inception to 1 May 2022. All studies reporting HRQoL following cranioplasty were included. Reporting was assessed using the ISOQOL checklist and risk of bias was assessed using the Newcastle-Ottawa Scale or the Johanna-Briggs Institute Scale, as appropriate. A total of 25 studies were included of which 20 were cross-sectional and 2 longitudinal. Most studies utilized study specific questionnaires and Likert scales to assess HRQoL. The studies found a significant improvement in physical functioning, social functioning, cosmetic outcome, and overall HRQoL following cranioplasty. Further longitudinal studies utilising validated measurement tools are required to better understand the effect of cranioplasty at a patient level.

Consensus on the prevention and repair of titanium mesh exposed wound after cranioplasty (2024 edition)

Titanium mesh exposure after cranioplasty is the most serious complication of this procedure. Although some clinical experience has been gradually accumulated over the years in the diagnosis and treatment of titanium mesh exposure, the treatment is often not standardized and it is difficult to achieve satisfactory repair results due to insufficient understanding of its pathogenesis and concurrent infections. To normalize the diagnosis and treatment of titanium mesh exposed wounds after cranioplasty and improve the therapeutic effect and the quality of life of patients, the Wound Repair Professional Committee of Chinese Medical Doctor Association organized an expert discussion based on the literature and current diagnosis and treatment status of titanium mesh exposed wounds after cranioplasty at home and abroad, and reached a consensus on the pathogenesis, preventive measures, and diagnosis and treatment strategies of titanium mesh exposed wounds after cranioplasty to provide reference for relevant clinicians.

Template Routed Patient-Specific Implant for 1-Stage Cranioplasty

BACKGROUND AND OBJECTIVES

Cranial reconstruction presents a significant challenge in cases involving pathologies with skull invasion, and various techniques have been used, including the intraoperative shaping of titanium mesh and the manual sculpting of bone cement serving as surrogates for the excised bone graft. In the context of prefabricated patient-specific implants (PSIs) for cranioplasty, precise surgical execution of craniotomies is paramount. This ensures optimal congruity between the implant and the defect created during the craniotomy, leading to a successful single-stage procedure encompassing both bone removal and reconstruction. This article presents a meticulous method for achieving such high-fidelity craniotomy and subsequent cranioplasty using PSIs in a single-stage surgery.

METHODS

The procedure was implemented for 2 cases of meningiomas with osseous invasion. Through meticulous preoperative planning, the craniotomy template and implant were designed using computer-assisted design and manufactured on a 3-dimensional printer using the patient's computed tomography scans. Intraoperative fabrication of sterile polymethyl methacrylate replicas was achieved through the creation of silicone molds and subsequent injection molding techniques. Predesignated screw holes facilitated neuronavigation-assisted positioning of the template, aligning it accurately with the target site using registration points. Mini-screws firmly secured the template to the skull. Guided by the template, a craniotomy router performed the bone resection. On completion, the implant was affixed into place using plates and screws.

RESULTS

This technique demonstrably facilitated a cost-effective, streamlined and precise application of prefabricated PSIs within a single-stage craniotomy-cranioplasty procedure. Subjective patient reports indicated high levels of satisfaction with the outcome.

CONCLUSION

The template routed patient-specific implant 1-stage cranioplasty technique refines previous approaches through precise template localization on the skull, enabling an accurate craniotomy to match a prefabricated PSI. This single-stage procedure rivals hand-shaped methods in aesthetics and compares with the outcomes of 2-stage PSI cranioplasties. Additional studies are needed to validate our results.

Assessing the radiofrequency shielding effect of titanium mesh on diffusion-weighted imaging: a comparative study of the twice-refocused spin-echo and Stejskal-Tanner sequences

This study compared twice-refocused spin-echo sequence (TRSE) and Stejskal-Tanner sequence (ST) to evaluate their respective effects on the image quality of magnetic resonance (MR) diffusion-weighted imaging in the presence of radiofrequency (RF) shielding effect of titanium mesh in cranioplasty. A 1.5-T MR scanner with a Head/Neck coil 20 channels and a phantom simulating the T2 and apparent diffusion coefficient (ADC) value of the human brain were used. Imaging was performed with and without titanium mesh placed on the phantom in TRSE and ST, and normalized absolute average deviation (NAAD), Dice similarity coefficient (DSC), and ADC values were calculated. The NAAD values were significantly lower for TRSE than for ST in the area below the titanium mesh, and the drop rates due to titanium mesh were 14.1% for TRSE and 9.8% for ST. The DSC values were significantly lower for TRSE than for ST. The ADC values were significantly higher for TRSE than for ST without titanium mesh. The ADC values showed no significant difference between TRSE and ST with titanium mesh. The ST had a lower RF shielding effect of titanium mesh than the TRSE.

Subgaleal drains may be associated with decreased infection following autologous cranioplasty: a retrospective analysis

BACKGROUND

Autologous bone is often the first choice in cranioplasty following a decompressive craniectomy. However, infection is a common complication, with reported rates up to 25%. While the incidence and management of infection are well documented, the risk factors associated with infection remain less clear. The current study aims to identify predictors of infection risk following autologous cranioplasty.

METHODS

A retrospective analysis was conducted on patients who underwent decompressive craniectomy and cranioplasty using cryopreserved autologous bone flaps between 2010 and 2020. Patient demographics and factors related to both surgeries and infection rates were recorded from patient records. Logistic regressions were conducted to determine which factors were implicated in the development of infection.

RESULTS

In our cohort, 126 patients underwent autologous cranioplasty. A total of 10 patients (7.9%) developed an infection following reconstruction, with half resulting in implant failure. We did not identify any significant risk factors for infection. Regression analysis identified placement of subgaleal drain following cranioplasty as a protective factor against the development of infection (OR: 0.16, p = 0.007). On average, drains remained in for 3 days, with no difference between the length of drains for those with infection vs. those without (p = 0.757).

CONCLUSIONS

The current study demonstrates an infection rate of 7.9% in patients who receive an autologous cranioplasty following decompressive craniectomy, which is consistent with previous data. Half (4%) of patients who experienced an infection ultimately required removal of the implant. While it is common practice for neurosurgeons to use drains to prevent hematomas and fluid collections, we found that subgaleal drain placement following cranioplasty was associated with decreased infection, thus demonstrating another benefit of a commonly used tool.

Interfaces between Cranial Bone and AISI 304 Steel after Long-Term Implantation: A Case Study of Cranial Screws

Interfaces between AISI 304 stainless steel screws and cranial bone were investigated after long-term implantation lasting for 42 years. Samples containing the interface regions were analyzed using state-of-the-art analytical techniques including secondary ion mass, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopies. Local samples for scanning transmission electron microscopy were cut from the interface regions using the focused ion beam technique. A chemical composition across the interface was recorded in length scales covering micrometric and nanometric resolutions and relevant differences were found between peri-implant and the distant cranial bone, indicating generally younger bone tissue in the peri-implant area. Furthermore, the energy dispersive spectroscopy revealed an 80 nm thick steel surface layer enriched by oxygen suggesting that the AISI 304 material undergoes a corrosion attack. The attack is associated with transport of metallic ions, namely, ferrous and ferric iron, into the bone layer adjacent to the implant. The results comply with an anticipated interplay between released iron ions and osteoclast proliferation. The interplay gives rise to an autocatalytic process in which the iron ions stimulate the osteoclast activity while a formation of fresh bone resorption sites boosts the corrosion process through interactions between acidic osteoclast extracellular compartments and the implant surface. The autocatalytic process thus may account for an accelerated turnover of the peri-implant bone.

The Applicability of Polyetheretherketone and Titanium Mesh in Cranioplasty: A Retrospective Comparative Analysis

OBJECTIVE

To compare the clinical application effect and safety of polyetheretherketone (PEEK) and titanium mesh (TM) in cranioplasty.

METHODS

Four-year retrospective comparison of patients (96 cases) undergoing synthetic cranioplasty with PEEK or TM. The patients were divided into the PEEK group (24 cases) and the TM group (72 cases) according to the implants, and the patient demographics, general conditions before the operation, postoperative complications, length of postoperative hospital stay, total costs, satisfaction with shaping and long-term complications were compared between the 2 groups.

RESULTS

Patients in the PEEK group were younger than those in the TM group (P=0.019). Hospitalization costs were significantly higher in the PEEK group than in the TM group (P<0.001). The incidence of postoperative subcutaneous effusion was 33% in the PEEK group and 6.9% in the TM group, which suggests that patients in the PEEK group had a higher risk of postoperative subcutaneous effusion (P=0.001). There was no significant difference in the incidence of long-term complications and cosmetic satisfaction between the 2 groups at 4 years postoperatively.

CONCLUSIONS

In this study, both titanium mesh and PEEK are reliable implants for cranioplasty. Titanium mesh is widely used in cranioplasty due to its cost-effective performance. PEEK has gradually gained recognition due to the characteristics of the material and surgical procedure, but the price needs to be further reduced, and attention should be paid to the occurrence and treatment of early postoperative subcutaneous effusion.

Intra-operative extracorporeal irradiation of tumour-invaded craniotomy bone flap in meningioma: a case series

BACKGROUND

Extracorporeal irradiation of tumorous calvaria (EITC) can be performed to restore function and form of the skull after resection of bone-invasive meningioma. We sought to examine the rate of tumour recurrence and other selected outcomes in patients undergoing meningioma resection and EITC.

METHODS

Retrospective single-centre study of adult patients undergoing meningioma resection and EITC between January 2015 and November 2022 at a tertiary neurosurgical centre. Patient demographics, surgery data, tumour data, use of adjuvant therapy, surgical complications, and tumour recurrences were collected.

RESULTS

Eighteen patients with 11 (61%) CNS WHO grade 1, 6 (33%) grade 2, and 1 (6%) grade 3 meningiomas were included. Median follow-up was 42 months (range 3-88). Five (28%) patients had a recurrence, but none were associated with the bone flap. Two (11%) wound infections requiring explant surgery occurred. Six (33%) patients required a further operation. Two operations were for recurrences, one was for infection, one was a washout and wound exploration but no evidence of infection was found, one patient requested the removal of a small titanium implant, and one patient required a ventriculoperitoneal shunt for a persistent CSF collection. There were no cases of bone flap resorption and cosmetic outcome was not routinely recorded.

CONCLUSION

EITC is feasible and fast to perform with good outcomes and cost-effectiveness compared to other reconstructive methods. We observed similar recurrence rates and lower infection rates requiring explant compared to the largest series of cranioplasty in meningioma. Cosmetic outcome is universally under-reported and should be reported in future studies.

Impact of Titanium Skull Plate on Transcranial Magnetic Stimulation: Analysis of Induced Electric Fields

BACKGROUND

Implanted titanium skull plates (TSPs) in cranioplasty are used to replace or reconstruct areas of the skull that have been damaged or removed due to trauma, surgery, or other medical conditions. However, the presence of a TSP in the head may influence the distribution of the electric field induced during transcranial magnetic stimulation (TMS) procedures. The purpose of this study was to determine how the presence of TSP would interfere with TMS-induced cortical electric fields.

METHODS

The TMS with a figure-of-eight coil was applied to a realistic head model with TSPs. The distribution of the induced electric field in head tissues was calculated by employing the impedance method, and the results were compared with that of a normal head without TSP.

RESULTS

Simulation results show that the distribution of the induced electric field has changed greatly for the head model with TSP. The maximum value of the induced electric field in head tissues was present under one of the circular coil wings rather than in the tissues beneath the junction of the two wings of the Fo8 coil.

CONCLUSIONS

The induced electric field in deep brain regions was increased for the head model with TSP, which could potentially lead to deep brain stimulation. Since the presence of metallic TSP can greatly influence the distribution of the induced electric field in TMS applications, it is important to adjust the treatment scheme when considering TMS for individuals with cranial titanium plates.

Cranioplasty in Oman: Retrospective review of cases from the National Craniofacial Center 2012-2022

Objectives

Cranioplasty is a complex craniofacial and neurosurgical procedure that aims to reinstate the architecture of the cranial vault and elevate both its aesthetic and neurological function. Several reconstructive materials have been thoroughly explored in the search for the optimal solution for cranioplasty. This study aimed to evaluate different material used for cranial reconstruction in Oman.

Methods

This retrospective study included all patients who had had cranioplasty procedures performed at Khoula Hospital, Muscat, Oman, from 2012 to 2022. Demographic information, the characteristics of the cranial defect and any complications that occurred post-operatively were analysed.

Results

A total of 47 patients were included in this study. The most common cause of cranial defects was craniectomy following traumatic head injury (70.2%) along with excision of fibrous dysplasia (10.6%). The most frequently utilised material for cranial repair was autologous bone grafts (n = 28), followed by polyetheretherketone (PEEK; n = 14). Interestingly, the replacement of bone grafts from previous craniectomy showed a notably high resorption rate (71.4%), in contrast to split calvarial grafts (0%) and other types of bone grafts (14.3%). Additionally, delayed graft infection was observed in 3.6% of the bone graft group and 7.1% of the PEEK group.

Conclusion

Patient-specific alloplastic implants such as PEEK have gained popularity for large and complex cranioplasty, as they provide excellent aesthetic outcomes and leave no donor site morbidity. In contrast, bone grafts remain the gold standard for small to medium-sized cranial defects.

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.

The potential role of mechanotransduction in the management of pediatric calvarial bone flap repair

Pediatric patients suffering traumatic brain injuries may require a decompressive craniectomy to accommodate brain swelling by removing a portion of the skull. Once the brain swelling subsides, the preserved calvarial bone flap is ideally replaced as an autograft during a cranioplasty to restore protection of the brain, as it can reintegrate and grow with the patient during immature skeletal development. However, pediatric patients exhibit a high prevalence of calvarial bone flap resorption post-cranioplasty, causing functional and cosmetic morbidity. This review examines possible solutions for mitigating pediatric calvarial bone flap resorption by delineating methods of stimulating mechanosensitive cell populations with mechanical forces. Mechanotransduction plays a critical role in three main cell types involved with calvarial bone repair, including mesenchymal stem cells, osteoblasts, and dural cells, through mechanisms that could be exploited to promote osteogenesis. In particular, physiologically relevant mechanical forces, including substrate deformation, external forces, and ultrasound, can be used as tools to stimulate bone repair in both in vitro and in vivo systems. Ultimately, combating pediatric calvarial flap resorption may require a combinatorial approach using both cell therapy and bioengineering strategies.

Nondestructive and high-resolution monitoring of inflammation-type skull defects regeneration on adult zebrafish with optical coherence tomography

Optimized animal models and effective imaging techniques are exceedingly important to study cranial defects in bone loss due to chronic inflammation. In this study, the assessment procedure on a zebrafish inflammation-type skull defects model was monitored in vivo with spectral-domain optical coherence tomography (SD-OCT), and the efficacy of etidronate disodium in bone regeneration was assessed. An acute skull defect injury model was established in adult zebrafish using a stereotaxic craniotomy device. SD-OCT imaging was performed immediately following the mechanical injury. Both SD-OCT and immunohistochemistry results demonstrated an increase in inflammation-induced skull destruction within 5 days, which was confirmed by pathological experiments.

Late Frontal Bone Reconstruction Using Three-Dimensional Printed Models for Titanium Mesh Customization: A Case Series

BACKGROUND

The convex frontal bone is covered by thin skin, rendering its reconstruction cosmetically challenging. Customized alloplastic implants provide better contouring than autologous bone, yet their high cost and availability limit their application. We assess customized titanium mesh implants precontoured using patient-specific three-dimensional (3D) printed models for late frontal cranioplasty.

METHODS

We retrospectively analyzed the prospectively collected cases of unilateral frontal titanium mesh cranioplasty with 3D printing-assisted preplanning from 2017 to 2019. We used two 3D-printed patient-specific skull models for preoperative planning: a mirrored normal model for implant contouring and a defect model for edge trimming and fixation planning. The endoscope was used in 4 cases for percutaneous mesh fixation. We documented postoperative complications. We assessed the reconstruction symmetry clinically, and radiologically on postoperative computed tomography.

RESULTS

Fifteen patients were included. The duration after previous surgery ranged from 8 to 24 months. Four patients developed complications, which were managed conservatively. Favorable cosmetic outcomes were achieved in all patients.

CONCLUSIONS

Precontouring of titanium mesh implants using in-house 3D-printed models could optimize cosmetic and surgical outcomes in late frontal cranioplasty. Preoperative planning could permit minimal access surgery, which could be aided by the endoscope in select cases.

A 2-Year Prospective Study of Complication Rates After Cranioplasty: Is 8 Weeks' Interval Associated with Increased Complications?

BACKGROUND

The commonly observed complications after cranioplasty include infections, intracranial hemorrhage, and seizures. The timing of cranioplasty after decompressive craniectomy (DC) is still under debate, with literature available for both early and delayed cranioplasties. The objectives of this study were to note the overall complication rates and more specifically compare complications between 2 different time intervals.

METHODS

This was a 24-month, single-center, prospective study. Since timing is the most debated variable, the study cohort was divided into 2 groups (≤8 weeks and >8 weeks). Furthermore, other variables such as age, gender, etiology of DC, neurologic condition, and blood loss were correlated with complications.

RESULTS

A total of 104 cases were analyzed. Two thirds were traumatic etiology. The mean and median DC-cranioplasty intervals were 11.3 weeks (range 4-52 weeks) and 9 weeks, respectively. Seven complications (6.7%) were observed in 6 patients. There was no statistical difference observed between any of the variables and complications.

CONCLUSIONS

We observed that performing cranioplasty within 8 weeks of the initial DC surgery is safe and noninferior to cranioplasty performed after 8 weeks. Therefore if the general condition of the patient is satisfactory, we are of the opinion that an interval of 6-8 weeks from the primary DC is safe and a reasonable time frame for performing cranioplasty.

Expanding Our Role in Headache Management: A Systematic Review and Algorithmic Approach to Surgical Management of Postcraniotomy Headache

BACKGROUND

Chronic postcraniotomy headache (PCH) is common and debilitating. Unfortunately, the literature on this topic is sparse without clear management algorithms. Possible etiologies of PCH include nerve injury and/or entrapment, hardware, dural adhesions, or musculoskeletal injury. The purpose of this study was to present the results of both a systematic review of the literature and a single-center case series, both of which informed the development of a novel treatment algorithm that may be applied to this patient population.

METHODS

Using Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, we performed a systematic review of the literature, identifying articles describing the surgical management of PCH. A retrospective chart review was performed to identify patients who met the criteria for PCH treated at our institution. A patient's history and physical examination determined the etiology and management, and pain severity scores were the primary outcome measured.

RESULTS

Nineteen articles encompassing 131 patients described surgical management techniques for PCH. 83 patients (63.3%) had complete resolution of pain (χ2 = 52.1, P < 0.0001). At our institution, 19 patients underwent surgical management for PCH. A significant reduction in pain scores from 7.57 to 2.16 (P < 0.001) was demonstrated, and 84 percent of patients achieved complete or significant pain reduction.

CONCLUSIONS

Through a literature review and our own case series, we demonstrate that surgical management of PCH can achieve remarkable results. Plastic surgeons, with their expanding role in treating migraine and headaches, are well suited to manage these patients. We present an algorithmic approach to simplify the management of this common and debilitating condition.

Modeling Methods in Craniofacial Virtual Surgical Planning

Despite the widespread use of virtual surgical planning (VSP), few papers describe the modeling methods used to generate the digital simulations that underpin VSP. This paper aims to review the modeling methods that are currently available for use in VSP and the implications of their use in clinical practice. A literature review was undertaken of the two broad categories of modeling techniques; contour-based planning-namely mirroring from the contralateral side, templating from a normative database, and extrapolation from surrounding landmarks-and occlusal-based planning (OBP). The indications for each modeling method were discussed, including mandibular/maxillary reconstruction, pediatric craniofacial surgery, and orthognathic, as well as the limitations to the accuracy of modeling types. Unilateral defects of the upper/midface, wherein contour accuracy is paramount, are best reconstructed using mirroring methods, whereas bilateral defects-or cases with asymmetry due to craniofacial dysmorphology-are most suited to normative-data-based methods. Cases involving resection of the alveolar margin, in which functional occlusion is the primary outcome are best managed with OBP. Similarly, orthognathic surgery typically uses OBP, although complex cases involving asymmetry, such as clefts, may benefit from a combination of OBP and normative data methods. The choice of modeling methods is, therefore, largely driven by the defect type and the goals of reconstruction.

Titanium Versus Autologous Bone-Based Cranioplasty: A Systematic Review and Meta-Analysis

At present, there is no gold standard when looking at reconstructive evidence for cranioplasty with the use of autologous bone as well as other synthetic materials. Titanium has been considered recently as a good option due to its unique properties such as strength and biocompatibility. Numerous studies have previously compared titanium with autologous bone for cranioplasty yet no meta-analysis has been performed within the literature to provide guidelines for craniofacial surgeons. A systematic review and meta-analysis were performed as per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A search of electronic information was conducted to identify all comparative studies of autologous bone vs. titanium implants in cranioplasty following a craniectomy. The primary outcomes were measured as re-operation rates and cosmesis, the secondary outcome measures included the incidence of complications, for example, bone resorption and infection. Five studies were selected, enrolling 323 cases. A high reoperation rate (p > 0.007) was seen in autologous cranioplasty using bone due to the significantly high resorption rate reported in this group. Cosmetic outcomes demonstrated no significant difference between the two groups examined. Finally, costs and infection rates (p > 0.18) were found to be comparable. Overall, titanium implants used in cranioplasty offer lower re-operation rates in comparison to autologous bone grafts whilst there was no major increase in adverse outcomes such as postoperative cost or rates.

Comparison of Infection Rates Following Immediate and Delayed Cranioplasty for Postcraniotomy Surgical Site Infections: Results of a Meta-Analysis

Postoperative surgical site infections (SSIs) in neurosurgery are rare. However, they pose a formidable challenge to the treating neurosurgeon and substantially worsen patient outcomes. These infections require prompt intervention in the form of débridement, including removal of craniotomy bone. Reconstruction of the craniotomy defect can be performed along with the débridement or can be performed at a later time. Although there have been concerns about performing cranioplasty at the same time as débridement, recent studies have advocated performance of cranioplasty at the same time as the débridement, as it avoids the morbidity associated with having a craniectomy defect and avoids the need for another surgical procedure. We conducted a literature review and meta-analysis to examine the data on immediate cranioplasties and delayed cranioplasties performed for postcraniotomy SSIs. We analyzed 15 articles with a total of 353 patients. Our analysis revealed that the pooled proportion of treatment failure was 10.4% (95% confidence interval [CI] 5.9%-17.8%) when an immediate cranioplasty was done and 16.1% (95% CI 7.2%-32.1%) when delayed cranioplasty was done. The pooled proportion of treatment failure was 12% (95% CI 5.9%-22.9%) when the same bone was used for cranioplasty and was 8% (95% CI 3%-20%) when prosthetic material such as titanium was used for cranial vault reconstruction. Thus, the rate of treatment failure was less when an immediate single-stage cranioplasty was done compared with a delayed cranioplasty following SSIs.

The cost of a plastic surgery team assisting with cranioplasty

OBJECTIVES

Cranioplasty is a commonly performed neurosurgical procedure that restores cranial anatomy. While plastic surgeons are commonly involved with cranioplasties, the cost of performing a cranioplasty with neurosurgery alone (N) vs. neurosurgery and plastic surgery (N + P) is unknown.

METHODS

A single-center, multi-surgeon, retrospective cohort study was undertaken on all cranioplasties performed from 2012 to 22. The primary exposure variable of interest was operating team, comparing N vs. N + P. Cost data was inflation-adjusted to January 2022 using Healthcare Producer Price Index as calculated by the US Bureau of Labor Statistics.

RESULTS

186 patients (105 N vs. 81 N + P) underwent cranioplasties. The N + P group has a significantly longer length-of-stay (LOS) 4.5 ± 1.6days, vs. 6.0 ± 1.3days (p < 0.001), but no significant difference in reoperation, readmission, sepsis, or wound breakdown. N was significantly less expensive than N + P during both the initial cranioplasty cost ($36,739 ± $4592 vs. $41,129 ± $4374, p 0.014) and total cranioplasty costs including reoperations ($38,849 ± $5017 vs. $53,134 ± $6912, p < 0.001). Univariable analysis (threshold p = 0.20) was performed to justify inclusion into a multivariable regression model. Multivariable analysis for initial cranioplasty cost showed that sepsis (p = 0.024) and LOS (p = 0.003) were the dominant cost contributors compared to surgeon type (p = 0.200). However, surgeon type (N vs. N + P) was the only significant factor (p = 0.011) for total cost including revisions.

CONCLUSIONS

Higher costs to N + P involvement without obvious change in outcomes were found in patients undergoing cranioplasty. Although other factors are more significant for the initial cranioplasty cost (sepsis, LOS), surgeon type proved the independent dominant factor for total cranioplasty costs, including revisions.

Clinical and patient-reported outcome after patient-specific 3D printer-assisted cranioplasty

Various cranioplasty techniques exist for the reconstruction of cranial bone defects. Patient-specific implants can be produced in-house using a recently developed 3D printer-assisted cranioplasty technique. However, the resulting cosmetic outcomes from the patient's perspective are underreported. With our case series, we aim to present the clinical outcome, morbidity rate, patient-reported cosmetic results, and cost-effectiveness of patient-specific3D printer-assisted cranioplasty technique. This is a consecutive retrospective case series of adult patients undergoing cranioplasty using the patient-specific 3D printer-assisted technique. As primary endpoint, the functional outcome based on modified Rankin scale (mRS) at discharge and follow-up was assessed. A prospective telephone survey was conducted to collect and provide patient-reported outcomes. Thirty-one patients underwent patient-specific 3D printer-assisted cranioplasty, mostly to reconstruct frontotemporoparietal (61.3%) and frontotemporal defects with orbital involvement (19.4%). Good functional outcome (mRS ≤ 2) at discharge and during the last follow-up was achieved in 54.8% (n = 17) and 58.1% (n = 18) patients. Overall, the rate of clinically relevant surgery-related complications was 35.5% (n = 11). Postoperative epidural hematoma/collection (16.1%) and infections (12.9%) were the most frequent complications. Permanent morbidity occurred in one patient (3.2%) with postoperative acute ipsilateral vision loss after frontotemporal cranioplasty with orbital involvement. No surgery-related mortality occurred. The mean patient-reported cosmetic satisfaction score was 7.8 ± 1.5, with 80% of patients reporting satisfying or very satisfying cosmetic results. No significant differences were seen between the different defect localization regarding the cosmetic outcome. The mean manufacturing costs of a patient-specific 3D printer-assisted implant ranged from 748 to 1129 USD. Based on our case series, patient-specific 3D printer-assisted cranioplasty is cost-effective and leads to satisfying cosmetic results, especially in large defects and/or defects with complex geometry.

Ultra-High-Molecular-Weight Polyethylene Merlon Shape: Novel Fixation of Artificial Bone for Cranioplasty

BACKGROUND

Cranioplasty is a surgical procedure widely performed for repairing cranial defects caused by external decompression surgery for cerebrovascular disease or traumatic brain injury. We devised a new cranioplasty method using artificial bone made up of ultra-high molecular-weight polyethylene, with serrated wings on the edge. We named this newly designed artificial bone as Merlon shape.

OBJECTIVE

To describe our initial experience with the Merlon shape and evaluate its usefulness and safety in cranioplasty.

METHODS

The serrated wings of the Merlon shape were preoperatively designed for solid fixation and improving cosmetic results by reducing the thickness of the artificial bone. We evaluated 25 patients who underwent cranioplasty with the Merlon shape between December 2018 and December 2021. The causes of bone defects in these patients (male: 9, female: 16; median age: 62 years) were subarachnoid hemorrhage (n = 14), cerebral infarction (n = 8), and traumatic brain injury (n = 3).

RESULTS

There were no postoperative adverse events such as infection, bone resorption, implant exposure, or graft sinking in 24 patients during an average follow-up period of 19 months. One patient experienced acute epidural hemorrhage and required reoperation.

CONCLUSION

This is the first report on the use of the ultra-high molecular-weight polyethylene Merlon shape. Our initial 4-year case series showed good outcomes with this method.

Evaluation of bacterial attachment on mineralized collagen scaffolds and addition of manuka honey to increase mesenchymal stem cell osteogenesis

The design of biomaterials to regenerate bone is likely to increasingly require modifications that reduce bacterial attachment and biofilm formation as infection during wound regeneration can significantly impede tissue repair and typically requires surgical intervention to restart the healing process. Further, much research on infection prevention in bone biomaterials has focused on modeling of non-resorbable metal alloy materials, whereas an expanding direction of bone regeneration has focused on development of bioresorbable materials. This represents a need for the prevention and understanding of infection in resorbable biomaterials. Here, we investigate the ability of a mineralized collagen biomaterial to natively resist infection and examine how the addition of manuka honey, previously identified as an antimicrobial agent, affects gram positive and negative bacterial colonization and mesenchymal stem cell osteogenesis and vasculature formation. We incorporate manuka honey into these scaffolds via either direct fabrication into the scaffold microarchitecture or via soaking the scaffold in a solution of manuka honey after fabrication. Direct incorporation results in a change in the surface characteristics and porosity of mineralized collagen scaffolds. Soaking scaffolds in honey concentrations higher than 10% had significant negative effects on mesenchymal stem cell metabolic activity. Soaking or incorporating 5% honey had no impact on endothelial cell tube formation. Although solutions of 5% honey reduced metabolic activity of mesenchymal stem cells, MSC-seeded scaffolds displayed increased calcium and phosphorous mineral formation, osteoprotegerin release, and alkaline phosphatase activity. Bacteria cultured on mineralized collagen scaffolds demonstrated surfaces covered in bacteria and no method of preventing infection, and using 10 times the minimal inhibitory concentration of antibiotics did not completely kill bacteria within the mineralized collagen scaffolds, indicating bioresorbable scaffold materials may act to shield bacteria from antibiotics. The addition of 5% manuka honey to scaffolds was not sufficient to prevent P. aeruginosa attachment or consistently reduce the activity of methicillin resistant staphylococcus aureus, and concentrations above 7% manuka honey are likely necessary to impact MRSA. Together, our results suggest bioresorbable scaffolds may create an environment conducive to bacterial growth, and potential trade-offs exist for the incorporation of low levels of honey in scaffolds to increase osteogenic potential of osteoprogenitors while high-levels of honey may be sufficient to reduce gram positive or negative bacteria activity but at the cost of reduced osteogenesis.

Can magnetic resonance imaging after cranioplasty using titanium mesh detect brain tumors?

This study determined the dependence of the concentration and position of contrast-enhanced tumors on the radio frequency (RF)-shielding effect of titanium mesh using the contrast-to-noise ratio (CNR) in magnetic resonance imaging (MRI). A phantom was constructed by filling a plastic container with manganese chloride tetrahydrate and agar. Four cellophane cylindrical containers were arranged from the end of the plastic container, and the brain tumor model was filled with gadobutrol diluted with NaCl, with molarity values of 0.2-1.0 mmol/L. The titanium mesh board was set on the left side of the phantom. Images were acquired using a 1.5-T MRI as well as two-dimensional spin-echo (2D SE) and three-dimensional fast spoiled gradient echo (3D FSPGR) sequences. CNR was calculated using the signal intensity values of the tumor model, surrounding area of the brain model, and background noise. Furthermore, the fractional change in CNR was calculated using values of CNR with and without the mesh. Moreover, a profile of CNR was created. The fractional change in CNR decreased at the brain tumor positions present near the mesh and at a contrast medium concentration of approximately ≤ 0.5 mmol/L in 2D SE and ≤ 0.25 mmol/L in 3D FSPGR. According to the CNR profiles, directly under the mesh, almost all contrast concentrations in 2D SE was unrecognizable; however, at a concentration of ≥ 0.5 mmol/L in 3D FSPGR was recognizable.

Outcomes of Mesh Cranioplasty in Scalp-Free Tissue Reconstruction: A Systematic Review and Meta-Analysis

OBJECTIVE

To systematically review the literature to determine the prevalence and risk of the free flap and postoperative complications in scalp-free tissue reconstruction with synthetic mesh cranioplasty.

DATA SOURCES

Search strategies created with a medical librarian were implemented using multiple databases in May 2021.

REVIEW METHODS

Two reviewers independently performed the review, data extraction, and quality assessment. Cohort studies of patients with scalp-free tissue reconstruction with or without mesh cranioplasty were included. Studies that did not report whether mesh was used or did not separate outcomes by mesh use were excluded. The primary outcomes were free flap failure and postoperative complications. A random-effects model was used for the meta-analysis to estimate prevalence and prevalence ratios (PRs).

RESULTS

A total of 28 studies and 440 cases of scalp-free tissue reconstruction were included. The pooled prevalence of free flap failures and postoperative complications in patients with mesh cranioplasty was estimated at 7% (95% confidence interval [CI], 3%-17%; p = .85, I²  = 0%) and 21% (95% CI, 14%-31%; p = .44, I²  = 0%), respectively. In a subgroup analysis, mesh cranioplasty was not associated with a significantly increased risk of free flap failure or postoperative complications when compared to cases without mesh cranioplasty; pooled PR 1.21 (95% CI, 0.50-2.88; p = .90, I²  = 0%) for free flap failure and PR 1.85 (95% CI, 0.89-3.85; p = .28, I²  = 19) for postoperative complications.

CONCLUSION

Synthetic mesh cranioplasty does not significantly increase the risk of free flap compromise or postoperative complications. A higher prevalence of postoperative recipient site complications was observed in patients with mesh cranioplasty.

Post-traumatic hydrocephalus may be associated with autologous cranioplasty failure, independent of ventriculoperitoneal shunt placement: a retrospective analysis

PURPOSE

Decompressive craniectomy (DC) is a common procedure used for the treatment of intracranial hypertension. Once brain swelling has subsided, a cranioplasty is performed to restore cosmesis and protection to the brain. While using the patient's autologous bone flap is often the first choice in cranioplasty, this procedure is frequently complicated by bone flap resorption and infection. This study seeks to identify predictors of autologous cranioplasty failure.

METHODS

A retrospective analysis was conducted on patients who underwent decompressive craniectomy and autologous cranioplasty. Patient demographics and factors related to both surgeries and failure rates were recorded from patient records. Logistic regressions were conducted to determine which factors were implicated in autologous cranioplasty failure.

RESULTS

In our cohort, 127 patients underwent autologous cranioplasty. Overall, 18 (14.2%) patients experienced autologous cranioplasty failure. Regression analysis identified development of post-traumatic hydrocephalus (PTH) following DC (OR: 3.26, p = 0.043), presence of neurological deficits following DC (OR: 4.88, p = 0.025), and reoperation prior to CP (OR 3.0, p = 0.049) as significant predictors of autologous cranioplasty failure. Of the 16 patients who developed PTH following DC, 9 received a VP shunt. The rate of flap failure was similar across the 9 PTH patients who received a shunt and the 7 PTH patients who did not receive a shunt (33% vs. 57% failure rate, respectively, p = 0.341).

CONCLUSION

Autologous cranioplasty is a reasonably successful procedure with a flap failure rate of 14.2%. We identified PTH, persistent neurological deficits, and reoperation prior to cranioplasty as significant predictors of autologous cranioplasty failure. Interestingly, the presence of VP shunt did not impact the odds of flap failure.

Next-generation personalized cranioplasty treatment

Decompressive craniectomy (DC) is a surgical procedure, that is followed by cranioplasty surgery. DC is usually performed to treat patients with traumatic brain injury, intracranial hemorrhage, cerebral infarction, brain edema, skull fractures, etc. In many published clinical case studies and systematic reviews, cranioplasty surgery is reported to restore cranial symmetry with good cosmetic outcomes and neurophysiologically relevant functional outcomes in hundreds of patients. In this review article, we present a number of key issues related to the manufacturing of patient-specific implants, clinical complications, cosmetic outcomes, and newer alternative therapies. While discussing alternative therapeutic treatments for cranioplasty, biomolecules and cellular-based approaches have been emphasized. The current clinical practices in the restoration of cranial defects involve 3D printing to produce patient-specific prefabricated cranial implants, that provide better cosmetic outcomes. Regardless of the advancements in image processing and 3D printing, the complete clinical procedure is time-consuming and requires significant costs. To reduce manual intervention and to address unmet clinical demands, it has been highlighted that automated implant fabrication by data-driven methods can accelerate the design and manufacturing of patient-specific cranial implants. The data-driven approaches, encompassing artificial intelligence (machine learning/deep learning) and E-platforms, such as publicly accessible clinical databases will lead to the development of the next generation of patient-specific cranial implants, which can provide predictable clinical outcomes. STATEMENT OF SIGNIFICANCE: Cranioplasty is performed to reconstruct cranial defects of patients who have undergone decompressive craniectomy. Cranioplasty surgery improves the aesthetic and functional outcomes of those patients. To meet the clinical demands of cranioplasty surgery, accelerated designing and manufacturing of 3D cranial implants are required. This review provides an overview of biomaterial implants and bone flap manufacturing methods for cranioplasty surgery. In addition, tissue engineering and regenerative medicine-based approaches to reduce clinical complications are also highlighted. The potential use of data-driven computer applications and data-driven artificial intelligence-based approaches are emphasized to accelerate the clinical protocols of cranioplasty treatment with less manual intervention and shorter intraoperative time.

Paradigm Shift in Materials for Skull Reconstruction Facilitated by Science and Technological Integration

The surgical repair of a bone deficiency in the skull caused by a prior procedure or accident is known as cranioplasty. There are various types of cranioplasties, but the majority entail raising the scalp and reshaping the skull using either the original piece of bone from the skull or a specially molded graft created from Titanium (plate or mesh), artificial bone in place of, a stable biomaterial (prefabricated customized implant to match the exact contour and shape of the skull). Cranioplasty, one of the oldest surgical treatments for cranial abnormalities, has undergone several changes throughout the years to discover the best material to improve patient outcomes. Various materials have been utilized in cranioplasty throughout history. As biomedical technology progresses, surgeons will have access to new materials. There is still no agreement on the optimum material, and research into biologic and nonbiologic alternatives is ongoing in the hopes of finding the finest reconstruction material. The materials and techniques used in cranioplasty are covered in this article.

Single-stage cranioplasty with customized polyetheretherketone implant after tumor resection using virtual reality and augmented reality for precise implant customization and placement: illustrative case

BACKGROUND

Cranioplasties are routinely performed to restore cosmesis and to protect intracranial contents after trauma, resection of tumors, or other pathologies. Traditionally done as a second-stage procedure, new single-stage cranioplasty protocols have been developed to minimize recovery periods, decrease complications, and improve patient satisfaction. These protocols, however, still require the use of larger than planned implants or use larger than ideal incisions to accommodate three-dimensional (3D) templates, which may not be optimal in regions with complex bony anatomy.

OBSERVATIONS

A 50-year-old woman with a painful and progressively enlarging hemangioma of the left frontal bone underwent a single-stage resection followed by custom cranioplasty using a new extended reality (XR)-based workflow. Excellent cosmetic results, decreased operative time, and a feasible workflow were achieved.

LESSONS

The use of an XR-based visualization platform allows the surgeon to treat lesions and perform custom cranioplasties in one session while avoiding common pitfalls of current single-stage workflows, such as increased operative times for tailoring implants, as well as minimizing the use of 3D overlay models, which may not appropriately conform to complex regional bony anatomy intraoperatively.

Treatment options for critical size defects - Comparison of different materials in a calvaria split model in sheep

Bone defects of the craniofacial skeleton are often associated with aesthetic and functional impairment as well as loss of protection to intra- and extracranial structures. Solid titanium plates and individually adapted bone cements have been the materials of choice, but may lead to foreign-body reactions and insufficient osseointegration. In contrast, porous scaffolds are thought to exhibit osteoconductive properties to support bone ingrowth. Here, we analyse in critical size defects of the calvaria in sheep whether different bone replacement materials may overcome those remaining challenges. In a critical size defect model, bilateral 20 × 20 × 5-mm craniectomies were performed on either side of the sagittal sinus in 24 adult female blackheaded sheep. Bony defects were randomised to one of five different bone replacement materials (BRMs): titanium scaffold, biodegradable poly(d,l-lactic acid) calcium carbonate scaffold (PDLLA/CC), polyethylene 1 (0.71 mm mean pore size) or 2 (0.515 mm mean pore size) scaffolds and polymethyl methacrylate (PMMA)-based bone cement block. Empty controls (n = 3) served as references. To evaluate bone growth over time, three different fluorochromes were administered at different time points. At 3, 6 and 12 months after surgery, animals were sacrificed and the BRMs and surrounding bone analysed by micro-CT and histomorphometry. The empty control group verified that the calvaria defect in this study was a reliable critical size defect model. Bone formation in vivo was detectable in all BRMs after 12 months by micro-CT and histomorphometric analysis, except for the non-porous PMMA group. A maximum of bone formation was detected in the 12-months group for titanium and PDLLA/CC. Bone formation in PDLLA/CC starts to increase rapidly between 6 and 12 months, as the BRM resorbs over time. Contact between bone and BRM influenced bone formation inside the BRM. Empty controls exhibited bone formation solely at the periphery. Overall, porous BRMs offered bone integration to different extent over 12 months in the tested calvaria defect model. Titanium and PDLLA/CC scaffolds showed remarkable osseointegration properties by micro-CT and histomorphometric analysis. PDLLA/CC scaffolds degraded over time without major residues. Pore size influenced bone ingrowth in polyethylene, emphasising the importance of porous scaffold structure.

Digital Mapping of a Massive Skull-Base Ameloblastoma with Intracranial Extension, Resection, and Reconstruction Using 3D Templates and Molds: Descriptive Case Report and Review

Radical surgery is the mainstay for the treatment of recurrent ameloblastomas; however, it leads to large, complex defects. In this case report, we present an innovative technique of digitally aided resection and reconstruction. A massive histologically confirmed acanthomatous ameloblastoma of the skull-base was digitally mapped with the help of three-dimensional (3D) computed tomography and a custom resection template was fabricated. Digital resection of the skull-base tumor with intracranial extension was done virtually and the resultant defect was reconstructed to create an anatomical replica of the contralateral unaffected side. The tumor was successfully resected with adequate margins guided by the resection template to avoid injury to adjacent vital structures. Subsequent reconstruction was performed by first adapting polymethyl methacrylate bone cement into a series of custom-made 3D molds. Once set, this bone cement served as a reconstructive implant to bridge the ablative defect. The implant offered a precise fit and was secured to healthy adjacent bone using titanium microplates. We present a 6-month follow-up of the case with satisfactory aesthetic results. 3D printing technology has the potential to revolutionize the arena of craniofacial resection with excellent cosmesis and no donor site morbidity if applied appropriately as described here.

Customized alloplastic cranioplasty of large bone defects by 3D-printed prefabricated mold template after posttraumatic decompressive craniectomy: A technical note

Background

Manufacturing of customized three-dimensional (3D)-printed cranioplastic implant after decompressive craniectomy has been introduced to overcome the difficulties of intraoperative implant molding. The authors present and discuss the technique, which consists of the prefabrication of silicone implant mold using additive manufacturing, also known as 3D printing, and polymethyl methacrylate (PMMA) implant casting.

Methods

To reconstruct a large bone defect sustained after decompressive craniectomy due to traumatic brain injury (TBI), a 3D-printed prefabricated mold template was used to create a customized PMMA implant for cranial vault repair in five consecutive patients.

Results

A superb restoration of the symmetrical contours and curvature of the cranium was achieved in all patients. The outcome was clinically and cosmetically favorable in all of them.

Conclusion

Customized alloplastic cranioplasty using 3D-printed prefabricated mold for casting PMMA implant is easy to perform technique for the restoration of cranial vault after a decompressive craniectomy following moderate-to-severe TBI. It is a valuable and modern technique to advance manufacturing of personalized prefabricated cranioplastic implants used for the reconstruction of large skull defects having complex geometry. It is a safe and cost-effective procedure having an excellent cosmetic outcome, which may considerably decrease expenses and time needed for cranial reconstructive surgery.

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.

Comparison of the Surgical Outcomes of Cranioplasty Using Titanium, Customized Polymethylmethacrylate, and Liquid Polymethylmethacrylate in Maharaj Nakhon Chiang Mai Hospital, Thailand

ABSTRACT

Cranioplasty is a standard procedure used to restore skull defects after craniectomy. Many different materials are used in cranioplasty. The study aim was to compare the surgical outcomes of cranioplasty using different materials: liquid polymethylmethacrylate (PMMA), customized PMMA, and titanium. The authors retrospectively reviewed the outcomes of cranioplasty performed from 2016 to 2021. Data collection included patient characteristics and complications, including postoperative infection, hematoma, implant exposure, and subgaleal cerebrospinal fluid collection. Eighty-five patients received cranioplasty with different materials: titanium, 14; customized PMMA, 31; and liquid PMMA, 40. There were no significant differences in the basic patient characteristics among the 3 cranioplasty groups except for lower age in the customized PMMA group. There were no significant differences between superficial and deep infections, implant exposure, postoperative hematoma, or seizure. However, subgaleal cerebrospinal fluid collection was more common in the liquid PMMA group than in the customized PMMA group (P = 0.02). This study showed that good outcomes were achieved by cranioplasty performed with different materials (titanium, customized PMMA, and liquid PMMA).

Occipital cranioplasty using customized titanium prosthesis yields successful outcome in association with foramen magnum decompression in dogs suffering by Chiari-like malformation

OBJECTIVE

To describe the use of a customized 3-D-printed titanium prosthesis as adjunctive treatment for foramen magnum decompression (FMD) in dogs with Chiari-like malformation (CM) and syringomyelia (SM).

ANIMALS

8 dogs with clinical signs and MRI findings of CM-SM.

PROCEDURES

3-D reconstruction of CT images of the head was used to simulate an occipital craniectomy and design the prosthesis. FMD was performed, and the prosthesis was implanted. Follow-up was performed 1, 6, and 12 months later, and clinical status was scored. Repeated MRI images were compared to identify changes involving the neural structures, particularly the syrinx.

RESULTS

All prostheses were easily positioned based on the preoperative 3-D models, with no complications. At 12 months after surgery, 3 dogs were free of previous medications, 4 were still receiving steroid medications but at lower doses, and 1 was occasionally receiving acupuncture. MRI of 5 dogs 6 to 20 months after surgery revealed resolution of SM (n = 1), reduced size of SM (3), or worse SM (1). All dogs showed an increase in size of the caudal cranial fossa. Dogs with a longer presurgical duration of the clinical signs and wider syrinx generally had worse outcomes than other dogs.

CLINICAL RELEVANCE

Findings suggested that use of customized 3-D-printed titanium prosthesis and associated FMD can represent an adjunctive option to medically treated dogs with CM-SM. Although the small number of cases precludes definitive conclusions, early surgical treatment, particularly in dogs with a small syrinx, could ensure better long-term outcomes, as previously suggested.

Reconstruction of the Occipital and Parietal Congenital Defect with 3D Custom-Made Titanium Prosthesis: A Case Report with Four and a Half Years of Follow-Up and a Brief Review of Literature

Management of patients with congenital skull defects requires a multidisciplinary approach. Considering the defect's location and size, brain protection, and the cosmetic outcome makes such reconstructions challenging. Due to limited resemblance to skull contour and donor site morbidity of autogenous bone grafts, alloplastic materials are widely used for skull reconstructions. Titanium alloys have proper strength values, low infection rates, favorable osseointegration property, and excellent marginal adaptability when manufactured by computer-aided design (CAD) and computer-aided manufacturing (CAM). A 13-year-old female patient presented with congenital defects at the superior third of occipital bone and posterior thirds of the bilateral parietal bones. On CT scan, the exact size and shape of the defect were determined. Using CAD/CAM, a 3D virtual model of the prosthesis was designed and then printed with titanium alloy (TiAl6V4) via additive manufacturing method. The prosthesis was placed on the defect in a total surgery time of only 90 minutes. On 4.5 years of follow-up, the contour of the skull was ideal and the skin over the defect and neurologic status was intact. Due to their biocompatibility and rigidity, custom-made titanium prostheses are promising options for reconstructing complex skull defects.

Cranioplasty

Calvarial defects are commonly encountered after neurosurgical procedures, trauma, and ablative procedures of advanced head neck cancers. The goals of cranioplasty are to provide a protective barrier for the intracranial contents, to restore form, and prevent syndrome of the trephined. Autologous and alloplastic techniques are available, each with their advantages and drawbacks. A multitude of materials are available for cranioplasty, and proper timing of reconstruction with attention to the overlying skin envelope is important in minimizing complications.

Contemporary Review on Craniectomy and Cranioplasty; Part 2: Material Selection and Plate Manufacture

ABSTRACT

Cranioplasty materials include metals (ie, titanium); ceramics (ie, hydroxyapatite); polymers (ie, poly-methyl-metha-acrylate [PMMA]); and plastics (ie, polyether ether ketone). This paper aims to review their advantages and drawbacks. No ideal material currently exist, however, titanium implants are universally agreed to have lower infection rates than those reported for hydroxyapatite and PMMA implants; thus justifying their current wide use. These implants can be manufactured conventionally from medical grade titanium alloy Ti64 (titanium-aluminum-vanadium) in the form of plates ranging in thickness from 0.5 to 0.7 mm thick, or following the computer-aided design/manufacture principle. Surface finish of these implants is best achieved by electroplating.

Contemporary Review on Craniectomy and Cranioplasty; Part 1: Decompressive Craniectomy

ABSTRACT

This paper aims to review clinical benefits of decompressive craniectomy (DC) in both adult and paediatric populations; its indications and factors contributing to its postoperative success. The Glasgow Outcome Scale and the Modified Rankin Scale are the most commonly used scales to assess the long-term outcome in patients post DC. In adult traumatic brain injury patients, 2 randomized clinical trials were carried out; DECRA (Decompressive Craniectomy in Diffuse Traumatic Brain Injury) and RESCUEicp (Randomised Evaluation of Surgery with Craniectomy for Uncontrollable Elevation of inter cranial pressure) employing collectively 555 patients. Despite the differences in these trials, their initial results affirm DC can lead to reduced mortality and more favorable outcomes. In ischemic stroke adult patients, different clinical trials of HAMLET (Dutch trial of Hemicraniectomy after middle cerebral artery infarction with life-threatening Edema), DESTINY (German trial of Decompressive Surgery for the treatment of Malignant Infarct of the Middle Cerebral Artery), and DECIMAL (French trial of Decompressive Craniectomy in Malignant Middle Cerebral Artery Infarcts) suggested that DC improves survival compared with best medical management, but with an increased proportion of treated individuals surviving with moderate or severe disability. With regard to the size of bone to be removed, the larger the defect the better the results with a minimum diameter of 11 to 12 cm of bone flap. Cranioplasty timing varies and ranges from 6 weeks to more than 12 months post DC, depending on completion of medical treatment, clinical recovery, resolution of any infection, and an evaluation of soft tissues at the defect site.

A Staged Approach for Contouring of Temporal Deformities Using Porous Polyethylene and Lipofilling

ABSTRACT

Many studies evaluated the effectiveness of a single reconstructive material during temporal cranioplasty, or in comparison to the outcome of another material. To our knowledge, no previous study evaluated a staged combination of reconstruction modalities during temporal cranioplasty. In a prospective interventional study, the authors combined high-density porous polyethylene (HDPP) implant insertion (stage I) with a following lipofilling session (stage II) in 8 patients scheduled for temporal cranioplasties. This two-staged approach was evaluated 6 months after each stage independently. The patients' satisfaction as regards the aesthetic outcome was evaluated through a 5-points Likert scale by the patients themselves. For every individual patient, this psychometric analysis was repeated by medical staff from other departments. Statistical analysis of the patients and medical staff satisfaction scores showed a statistically significant increase after the addition of lipofilling session (stage II) if compared to implant insertion only (stage I). Clinically, this outcome was maintained in a long-term follow-up ranged from 1 - 8 years. Nevertheless, 2 patients needed one more lipofilling session to obtain their satisfaction as regards the final aesthetic outcome. No other complications were recorded in this study. In conclusion, combining alloplastic and autogenous reconstruction modalities in a staged approach can suffice the reconstruction requirements for such temporal defects. After a long follow-up period, the insertion of high-density porous polyethylene implant with the addition of a following lipofilling session showed more evaluators' satisfaction in terms of the final aesthetic outcome.

Complications of Cranioplasty in Relation to Material: Systematic Review, Network Meta-Analysis and Meta-Regression

BACKGROUND

Cranioplasty is a ubiquitous neurosurgical procedure consisting of reconstruction of a pre-existing calvarial defect. Many materials are available, including polymethylmethacrylate in hand-moulded (hPMMA) and prefabricated (pPMMA) form, hydroxyapatite (HA), polyetheretherketone (PEEK) and titanium (Ti).

OBJECTIVE

To perform a network meta-analysis (NMA) to assess the relationship between materials and complications of cranioplasty.

METHODS

PubMed/MEDLINE, Google Scholar, EMBASE, Scopus, and The Cochrane Library were searched from January 1, 1990 to February 14, 2021. Studies detailing rates of any of infections, implant exposure, or revision surgery were included. A frequentist NMA was performed for each complication. Risk ratios (RRs) with 95% CIs were calculated for each material pair.

RESULTS

A total of 3620 abstracts were screened and 31 full papers were included. Surgical revision was reported in 18 studies and occurred in 316/2032 cases (14%; 95% CI 11-17). PEEK had the lowest risk of re-operation with a rate of 8/157 (5%; 95% CI 0-11) in 5 studies, superior to autografts (RR 0.20; 95% CI 0.07-0.57), hPMMA (RR 0.20; 95% CI 0.07-0.60), Ti (RR 0.39; 95% CI 0.17-0.92), and pPMMA (RR 0.14; 95% CI 0.04-0.51). Revision rate was 131/684 (19%; 95% CI 13-25; 10 studies) in autografts, 61/317 (18%; 95%CI 9-28; 7 studies) in hPMMA, 84/599 (13%; 95% CI 7-19; 11 studies) in Ti, 7/59 (9%; 95% CI 1-23; 3 studies) in pPMMA, and 25/216 (12%; 95% CI 4-24; 4 studies) in HA. Infection occurred in 463/4667 (8%; 95% CI 6-11) and implant exposure in 120/1651 (6%; 95% CI 4-9).

CONCLUSION

PEEK appears to have the lowest risk of cranioplasty revision, but further research is required to determine the optimal material.

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.

Three-dimensional Gradient-echo is Effective in Suppressing Radiofrequency Shielding by a Titanium Mesh

PURPOSE

To determine which sequence for frequently used general contrast-enhanced brain MRI shows the least radiofrequency shielding effect of a titanium mesh in cranioplasty using a phantom.

METHODS

A 1.5T MRI scanner was used. Frequently used general 2D and 3D spin-echo sequences (SE) and T1 spoiled gradient echo sequences (GRE) used for MRI in clinical settings were adopted in this study. A titanium mesh was placed above a cubic phantom containing manganese chloride tetrahydrate and sodium chloride. The signal attenuation ratio and normalized absolute average deviation (NAAD) were calculated. Moreover, the flip angle (FA) dependency in SE and area of excitation dependency in 3D sequences were analyzed using NAAD.

RESULTS

The signal attenuation ratio at the position nearest to the titanium mesh for 2D SE was 71.8% larger than that at the position nearest to the titanium mesh for 3D GRE. With regard to NAAD, 3D GRE showed the highest values among the sequences. When FA was increased, radiofrequency shielding effect was improved. There were no significant differences between the narrow and wide area of excitation. 3D GRE showed the least radiofrequency shielding effect, and it was considered as the optimal sequence for MRI in the presence of a titanium mesh.

CONCLUSION

3D GRE shows the least radiofrequency shielding effect of a titanium mesh after cranioplasty among frequently used general sequences for contrast-enhanced brain MRI.

Design and Additive Manufacturing of a Biomimetic Customized Cranial Implant Based on Voronoi Diagram

Reconstruction of cranial defects is an arduous task for craniomaxillofacial surgeons. Additive manufacturing (AM) or three-dimensional (3D) printing of titanium patient-specific implants (PSIs) made its way into cranioplasty, improving the clinical outcomes in complex surgical procedures. There has been a significant interest within the medical community in redesigning implants based on natural analogies. This paper proposes a workflow to create a biomimetic patient-specific cranial prosthesis with an interconnected strut macrostructure mimicking bone trabeculae. The method implements an interactive generative design approach based on the Voronoi diagram or tessellations. Furthermore, the quasi-self-supporting fabrication feasibility of the biomimetic, lightweight titanium cranial prosthesis design is assessed using Selective Laser Melting (SLM) technology.

Modified Cranioplasty and Latissimus Dorsi Flap for an Exophytic Invasive Brain Tumor

ABSTRACT

We describe the clinical case of a 62-year-old man with an atypical grade II meningioma, invading bone and scalp, and present a step-by-step video description of a modified technique for cranioplasty and scalp reconstruction with latissimus dorsi flap. By using this technique, we aim to minimize the space between the dura and the flap, which would decrease the risk of fluid collections and infections.