Correction of large (>25 cm(2)) cranial defects with "reinforced" hydroxyapatite cement: technique and complications

Research progress and perspective of metallic implant biomaterials for craniomaxillofacial surgeries

Craniomaxillofacial bone serves a variety of functions. However, the increasing number of cases of craniomaxillofacial bone injury and the use of selective rare implants make the treatment difficult, and the cure rate is low. If such a bone injury is not properly treated, it can lead to a slew of complications that can seriously disrupt a patient's daily life. For example, premature closure of cranial sutures or skull fractures can lead to increased intracranial pressure, which can lead to headaches, vomiting, and even brain hernia. At present, implant placement is one of the most common approaches to repair craniomaxillofacial bone injury or abnormal closure, especially with biomedical metallic implants. This review analyzes the research progress in the design and development of degradable and non-degradable metallic implants in craniomaxillofacial surgery. The mechanical properties, corrosion behaviours, as well as in vitro and in vivo performances of these materials are summarized. The challenges and future research directions of metallic biomaterials used in craniomaxillofacial surgery are also identified.

Utilization of carbonated calcium phosphate cement for contouring cranioplasty in patients with syndromic craniosynostosis

PURPOSE

Carbonated calcium phosphate (CCP) cement is an alloplastic material which has been increasingly utilized for cranioplasty reconstruction; however, there is a paucity of data investigating its use in patients with syndromic craniosynostosis. The purpose of this study was to characterize our institutional experience with CCP cement for secondary contouring cranioplasty in these patients to establish safety and aesthetic efficacy.

METHODS

Patients with syndromic craniosynostosis undergoing cranioplasty with CCP cement from 2009 to 2022 were retrospectively reviewed for prior medical and surgical history, cranioplasty size, cement usage, and postoperative complications. Aesthetic ratings of the forehead region were quantified using the Whitaker scoring system at three timepoints: preoperative (T1), < 6 months postoperative (T2), and > 1 year postoperative (T3).

RESULTS

Twenty-one patients were included. Age at surgery was 16.2 ± 2.8 years, forehead cranioplasty area was 135 ± 112 cm², and mass of cement was 17.2 ± 7.8 g. Patients were followed for 3.0 ± 3.1 years. Whitaker scores decreased from 1.9 ± 0.4 at T1 to 1.4 ± 0.5 at T2 (p = 0.005). Whitaker scores at T2 and T3 were not significantly different (p = 0.720). Two infectious complications (9.5%) were noted, one at 4.5 months postoperatively and the other at 23 months, both requiring operative removal of CCP cement.

CONCLUSION

Our results suggest that aesthetic forehead ratings improve after CCP contouring cranioplasty and that the improvement is sustained in medium-term follow-up. Complications were uncommon, suggesting that CCP is relatively safe though longer-term follow-up is needed before reaching definitive conclusions.

Rates of operative intervention for infection after synthetic or autologous cranioplasty: a National Readmissions Database analysis

OBJECTIVE

The aim of this study was to characterize the clinical utilization and associated charges of autologous bone flap (ABF) versus synthetic flap (SF) cranioplasty and to characterize the postoperative infection risk of SF versus ABF using the National Readmissions Database (NRD).

METHODS

The authors used the publicly available NRD to identify index hospitalizations from October 2015 to December 2018 involving elective ABF or SF cranioplasty after traumatic brain injury (TBI) or stroke. Subsequent readmissions were further characterized if patients underwent neurosurgical intervention for treatment of infection or suspected infection. Survey Cox proportional hazards models were used to assess risk of readmission.

RESULTS

An estimated 2295 SF and 2072 ABF cranioplasties were performed from October 2015 to December 2018 in the United States. While the total number of cranioplasty operations decreased during the study period, the proportion of cranioplasties utilizing SF increased (p < 0.001), particularly in male patients (p = 0.011) and those with TBI (vs stroke, p = 0.012). The median total hospital charge for SF cranioplasty was $31,200 more costly than ABF cranioplasty (p < 0.001). Of all first-time readmissions, 20% involved surgical treatment for infectious reasons. Overall, 122 SF patients (5.3%) underwent surgical treatment of infection compared with 70 ABF patients (3.4%) on readmission. After accounting for confounders using a multivariable Cox model, female patients (vs male, p = 0.003), those discharged nonroutinely (vs discharge to home or self-care, p < 0.001), and patients who underwent SF cranioplasty (vs ABF, p = 0.011) were more likely to be readmitted for reoperation. Patients undergoing cranioplasty during more recent years (e.g., 2018 vs 2015) were less likely to be readmitted for reoperation because of infection (p = 0.024).

CONCLUSIONS

SFs are increasingly replacing ABFs as the material of choice for cranioplasty, despite their association with increased hospital charges. Female sex, nonroutine discharge, and SF cranioplasty are associated with increased risk for reoperation after cranioplasty.

Skull Reconstruction Using a Custom-Made, Three-Dimensional-Printed, Hydroxyapatite-Titanium Cranioplasty Implant: Largest Single-Center U.S. Experience

OBJECTIVE

Although several material options, both natural and synthetic, are available for cranioplasty, the rate of implant-related complications has remained high. A relatively novel, synthetic hydroxyapatite-titanium implant, which combines biocompatibility with biomechanical resilience, has been reported to reduce tissue inflammation, infection, and explantation rates, while delivering superior cosmetic results. However, despite such promising preliminary reports, clinical data supporting its use have remained scarce.

METHODS

All the patients who had undergone cranioplasty between 2019 and 2022 using this implant were identified from a prospectively maintained database. Medical records were retrospectively reviewed and the following variables recorded: demographic data, clinical data, radiologic findings, operative details, complications (implant-related and unrelated), and outcomes.

RESULTS

A total of 18 patients (12 men and 6 women), with a mean age of 39 years (range, 20-70 years), were identified. The indications for craniectomy were traumatic brain injury (n = 13; 72.2%), hemorrhagic stroke (n = 3; 16.7%), and ischemic stroke (n = 2; 11.1%). The median time to cranioplasty was 140 days (range, 51-1717 days). The median modified Rankin scale score before cranioplasty was 4 (range, 0-5). Cranioplasty was technically successful in all 18 patients. Minor postoperative complications, none related to the implant, were managed conservatively in 3 patients (16.6%), including a small intraparenchymal hematoma in 1, an extra-axial hematoma in 1, and a seizure in 1. Of these 3 patients, 1 (5.6%) died 1 week later of a suspected pulmonary embolism. No implant-related complications occurred after a median follow-up of 6 months (range, 1-38 months). All 17 survivors exhibited some degree of neurologic improvement. The cosmetic result was good or excellent for all patients.

CONCLUSIONS

Our experience, the largest in the United States, confirms the previously reported benefits associated with the use of 3-dimensional-printed hydroxyapatite-titanium cranioplasty implants.

Biomechanics of Additively Manufactured Metallic Scaffolds-A Review

This review paper is related to the biomechanics of additively manufactured (AM) metallic scaffolds, in particular titanium alloy Ti6Al4V scaffolds. This is because Ti6Al4V has been identified as an ideal candidate for AM metallic scaffolds. The factors that affect the scaffold technology are the design, the material used to build the scaffold, and the fabrication process. This review paper includes thus a discussion on the design of Ti6A4V scaffolds in relation to how their behavior is affected by their cell shapes and porosities. This is followed by a discussion on the post treatment and mechanical characterization including in-vitro and in-vivo biomechanical studies. A review and discussion are also presented on the ongoing efforts to develop predictive tools to derive the relationships between structure, processing, properties and performance of powder-bed additive manufacturing of metals. This is a challenge when developing process computational models because the problem involves multi-physics and is of multi-scale in nature. Advantages, limitations, and future trends in AM scaffolds are finally discussed. AM is considered at the forefront of Industry 4.0, the fourth industrial revolution. The market of scaffold technology will continue to boom because of the high demand for human tissue repair.

Graded Reconstruction Strategy Using a Multilayer Technique Without Lumbar Drainage After Endoscopic Endonasal Surgery

OBJECTIVE

Sellar reconstruction following endoscopic endonasal surgery (EES) requires modification based on the degree of cerebrospinal fluid (CSF) leak. For high-flow (grade II or III according to Esposito et al. 2007) intraoperative CSF leak, lumbar drainage (LD), in addition to the multilayer closing technique, is generally recommended. However, LD occasionally has complications including postpuncture headache, overdrainage symptoms, and increased length of stay. We retrospectively evaluated the outcome of our graded reconstruction strategy using a multilayer technique with a novel material, without LD, after EES.

METHODS

Ninety-seven patients who underwent EES with grade II or III intraoperative CSF leak between June 2020 and March 2021 were retrospectively reviewed. For grade II CSF leak, fibrin sealant and a nasoseptal flap were placed; for grade III CSF leak, a multilayer technique was used in combination with collagen matrix, an acellular dermal graft, injectable hydroxyapatite (HXA), and a nasoseptal flap. Postoperatively, routine LD was not performed.

RESULTS

This study included 48 (49.5%) grade II and 49 (50.5%) grade III CSF leaks. At follow-up (mean, 8.7 months), no patient showed postoperative CSF leak in either group. No HXA-associated complications occurred.

CONCLUSIONS

A graded surgical repair strategy after EES could avoid postoperative CSF leak. Combined use of injectable HXA and acellular dermal grafts for high-flow CSF leak can limit LD requirement without significant risks.

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.

Pharmaceutical electrospinning and 3D printing scaffold design for bone regeneration

Bone regenerative engineering provides a great platform for bone tissue regeneration covering cells, growth factors and other dynamic forces for fabricating scaffolds. Diversified biomaterials and their fabrication methods have emerged for fabricating patient specific bioactive scaffolds with controlled microstructures for bridging complex bone defects. The goal of this review is to summarize the points of scaffold design as well as applications for bone regeneration based on both electrospinning and 3D bioprinting. It first briefly introduces biological characteristics of bone regeneration and summarizes the applications of different types of material and the considerations for bone regeneration including polymers, ceramics, metals and composites. We then discuss electrospinning nanofibrous scaffold applied for the bone regenerative engineering with various properties, components and structures. Meanwhile, diverse design in the 3D bioprinting scaffolds for osteogenesis especially in the role of drug and bioactive factors delivery are assembled. Finally, we discuss challenges and future prospects in the development of electrospinning and 3D bioprinting for osteogenesis and prominent strategies and directions in future.

Biomaterials in Craniomaxillofacial Reconstruction: Past, Present, and Future

ABSTRACT

Deformity and tissue loss involving the craniomaxillofacial region occurs frequently as a result of trauma, oncologic resection, or a congenital malformation. In order to maximize the patient's quality of life, reconstruction of the craniomaxillofacial skeleton must seek to restore aesthetics as well as function. Advances in diagnostic technology, surgical technique, instrumentation, and innovative biomaterials used have transformed the way reconstructive surgeons approach their patients' needs. From the advent of alloplastic reconstruction, surgeons have sought the ideal material for use in craniomaxillofacial surgery. Substances such as metals, ceramics, glasses, and more recently resorbable polymers and bioactive materials have all been utilized.While autologous bone has remained widely-favored and the gold standard, synthetic alternatives remain a necessity when autologous reconstruction is not readily available. Today, alloplastic material, autografting via microvascular tissue transfer, hormone and growth factor-induced bone formation, and computer-aided design and manufacturing of biocompatible implants represent only a fraction of a wide range of options used in the reconstruction of the craniomaxillofacial skeleton. We present a brief review of the materials used in the repair of deformities of the craniomaxillofacial skeleton as well as a look into the potential future direction of the field.

Complications of cranioplasty in relationship to traumatic brain injury: a systematic review and meta-analysis

Despite being a common procedure, cranioplasty (CP) is associated with a variety of serious, at times lethal, complications. This study explored the relationship between the initial injury leading to decompressive craniectomy (DC) and the rates and types of complications after subsequent CP. It specifically compared between traumatic brain injury (TBI) patients and patients undergoing CP after DC for other indications.A comprehensive search of PubMed, Scopus, and the Cochrane Library databases using PRISMA guidelines was performed to include case-control studies, cohorts, and clinical trials reporting complication data for CP after DC. Information about the patients' characteristics and the rates of overall and specific complications in TBI and non-TBI patients was extracted, summarized, and analyzed.A total of 59 studies, including the authors' institutional experience, encompassing 9264 patients (4671 TBI vs. 4593 non-TBI) met the inclusion criteria; this total also included 149 cases from our institutional series. The results of the analysis of the published series are shown both with and without our series 23 studies reported overall complications, 40 reported infections, 10 reported new-onset seizures, 13 reported bone flap resorption (BFR), 5 reported post-CP hydrocephalus, 10 reported intracranial hemorrhage (ICH), and 8 reported extra-axial fluid collections (EFC). TBI was associated with increased odds of BFR (odds ratio [OR] 1.76, p < 0.01) and infection (OR 1.38, p = 0.02). No difference was detected in the odds of overall complications, seizures, hydrocephalus, ICH, or EFC.Awareness of increased risks of BFR and infection after CP in TBI patients promotes the implementation of new strategies to prevent these complications especially in this category of patients.

Security and reliability of CUSTOMBONE cranioplasties: A prospective multicentric study

BACKGROUND

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

OBJECTIVE

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

RESULTS

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

CONCLUSION

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

Calcium Phosphate Cement "Space Fill-in" Augmentation in Autologous Cranioplasty for Large Cranial Defect: Additional Technical Consideration and Its Long-term Follow-up

In the skull tumor surgery that requires a large cranial reconstruction, economical one-time surgery is challenging. Calcium phosphate paste (CPC) alone is not applied in the large defect. Other plastic fill-in materials have each drawback. Ready-made implants are costly. The authors present additional technique of CPC cranioplasty combined with mainstay autologous grafts for a large cranial defect. The combination of split rib grafts was augmented by CPC. Tenons were placed for the stability of grafts. Our newly additional technique is that CPC is filled in the small adjacent spaces of autografts, not applied as the simple on-lay graft. We introduced this method to a 57-year-old gentleman with left parietal expansile skull tumor. The aesthetics of the patient has been satisfactory, and there were no complaints about pain in the graft site. In the follow-up period of 8 years, both autologous grafts and CPC were well maintained without marked resorption. This patient could work as a farmer in this period. Our methods fulfilled the requirements of aesthetics and in-situ plasticity for a larger cranial defect.

Use of Onlay Hydroxyapatite Cement for Secondary Cranioplasty

BACKGROUND

Children who undergo bi-fronto-orbital advancement (BFOA) frequently develop a contour deformity on the temporal and supra-orbital region, with an incidence reported as high as 55% and 75%, respectively. Up to 20% of patients may require correction. Hydroxyapatite cement (HAC) is a good alternative to autogenous tissue. The available literature on its use focusses on the reconstruction of bone defects, but little has been published on its efficacy and safety as an onlay graft over intact cranium.

OBJECTIVES

To describe our institution's experience with HAC in the pediatric population.

METHODS

Retrospective chart review from 1998 to 2018 on all patients from the Craniofacial Unit at the Sydney Children's Hospital who had either coronal or metopic craniosynostosis and underwent BFOA and later in life required cranioplasty with HAC for contour repair.

FINDINGS

We have performed 166 BFOA and nineteen secondary cranioplasties for contour repair using onlay HAC. The mean age at the time of operation was 14 years. Bi-coronal craniosynostosis was most frequently associated with secondary cranioplasty and 37% had an associated syndrome. The mean volume of HAC used was 37 mL. There was only 1 patient who had a complication (5.3%) and required partial removal of allograft. The mean length of admission was 2 days. Mean follow up time of 22.4 months.

CONCLUSIONS

HAC represents a safe option when used correctly, with low rates of complication and satisfactory cosmetic outcomes.

Mechanical behaviour of composite calcium phosphate-titanium cranial implants: Effects of loading rate and design

Cranial implants are used to repair bone defects following neurosurgery or trauma. At present, there is a lack of data on their mechanical response, particularly in impact loading. The aim of the present study was to assess the mechanical response of a recently developed composite calcium phosphate-titanium (CaP-Ti) implant at quasi-static and impact loading rates. Two different designs were tested, referred to as Design 1 (D1) and Design 2 (D2). The titanium structures in the implant specimens were additively manufactured by a powder-bed fusion process and subsequently embedded in a self-setting CaP material. D1 was conceptually representative of the clinically used implants. In D2, the titanium structure was simplified in terms of geometry in order to facilitate the manufacturing. The mechanical response of the implants was evaluated in quasi-static compression, and in impact using a drop-tower. Similar peak loads were obtained for the two designs, at the two loading rates: 808 ± 29 N and 852 ± 34 for D1, and 840 ± 40 N and 814 ± 13 for D2. A strain rate dependency was demonstrated for both designs, with a higher stiffness in the impact test. Furthermore, the titanium in the implant fractured in the quasi-static test (to failure) but not in the impact test (to 5.75 J) for D1. For D2, the displacement at peak load was significantly lower in the impact test than in the quasi-static test. The main difference between the designs was seen in the quasi-static test results where the deformation zones, i.e. notches in the titanium structure between the CaP tiles, in D1 likely resulted in a localization of the deformation, compared to in D2 (which did not have deformation zones). In the impact test, the only significant difference between the designs was a higher maximum displacement of D2 than of D1. In comparison with other reported mechanical tests on osteoconductive ceramic-based cranial implants, the CaP-Ti implant demonstrates the highest reported strength in quasi-static compression. In conclusion, the titanium structure seems to make the CaP-Ti implant capable of cerebral protection in impact situations like the one tested in this study.

Reconstruction of Craniomaxillofacial Bone Defects With Customized Prosthesis of Hydroxyapatite/Epoxide Acrylate Maleic Compound Designed by Computer-Aided Technique

The purpose of this study is to evaluate the clinical technique of reconstruction of craniomaxillofacial bone defects by using hand-made customized prosthesis of hydroxyapatite (HA)/epoxide acrylate maleic (EAM) compound with computer-aided technique. Between 2008 and 2015, eleven patients underwent computed tomography, three-dimensional (3D) imaging and reconstruction surgery. These customized HA/EAM compound artificial implants were hand-made, guided by computer-aided solid 3D reconstruction models of pre-operation structures of the patients. The artificial implants had to match the bone loss area accurately and be fixed stable with titanium screws and titanium meshes. For all patients and their surgeons, the post-operative aesthetics and functionality of the prosthesis were satisfactory. Only one patient felt a prominent edge of the prosthesis, but without any discomfort. In this case, a small groove was observed through CT scan. During the follow-up period (6-87 months), none of the 11 patients experienced any other complications, nor did they need secondary operation for adjusting or removing the prosthesis. In conclusion, this reconstruction technique of craniomaxillofacial bone defects by using hand-made customized HA/EAM compound artificial implants can achieve ideal results in both appearance and functionality.

Complications after craniofacial reconstruction with calcium phosphate cements: a case report and review of the literature

Among different graft materials for craniofacial reconstruction, calcium phosphate cements have the advantages of alloplastic grafts and wide use. The authors report a case of foreign body reaction following frontal reconstruction with JectOS (an injectable calcium orthophosphate cement; Kasios) and reviewed the literature on complications of this material after craniofacial reconstruction from 2002 to 2017. Complications were categorized into two groups: immunologic reactions (consisting of seroma collection, chronic sinus mucosa swelling, and foreign body reaction) and non-immune events (infection, fragmentation, and ejection). It is wise to use calcium phosphate-based material only in selected cases with small defects, and long-term follow-up is needed to observe their consequences.

Patient-Specific Titanium-Reinforced Calcium Phosphate Implant for the Repair and Healing of Complex Cranial Defects

BACKGROUND

The reconstruction of complex cranial defects is challenging and is associated with a high complication rate. The development of a patient-specific, titanium-reinforced, calcium phosphate-based (CaP-Ti) implant with bone regenerative properties has previously been described in 2 case studies with the hypothesis that the implant may improve clinical outcome.

OBJECTIVE

To identify whether the introduction of CaP-Ti implant has the potential to improve clinical outcome.

METHODS

A retrospective review of all patients having undergone CaP-Ti cranioplasty was conducted. Comprehensive clinical data were collected from the hospital computer database and patient records. Bone formation and osseointegration were analyzed in a single retrieval specimen.

RESULTS

Fifty patients, with 52 cranial defects, met the inclusion criteria. The patient cohort displayed a previous failure rate of 64% (32/50) with autologous bone, alloplastic materials, or both. At a median follow-up time of 25 months, the explantation rate due to either early postoperative infection or persistent wound dehiscence was 1.9% (1/53) or 3.8% (2/53), respectively. Surgical intervention with local wound revision was required in 2 patients without the need of implant removal. One patient had a brain tumor recurrence, and the implant was explanted 31 months after implantation. Histologic examination showed that the entire implant was partly yet evenly transformed into vascularized compact bone.

CONCLUSION

In the present study the CaP-Ti implant appears to have improved the clinical outcomes in a cohort of patients with a high rate of previous cranioplasty failures. The bone regenerative effect may in particular have an impact on the long-term success rate of the implant.

Bioinspired Collagen Scaffolds in Cranial Bone Regeneration: From Bedside to Bench

Calvarial defects are common reconstructive dilemmas secondary to a variety of etiologies including traumatic brain injury, cerebrovascular disease, oncologic resection, and congenital anomalies. Reconstruction of the calvarium is generally undertaken for the purposes of cerebral protection, contour restoration for psychosocial well-being, and normalization of neurological dysfunction frequently found in patients with massive cranial defects. Current methods for reconstruction using autologous grafts, allogeneic grafts, or alloplastic materials have significant drawbacks that are unique to each material. The combination of wide medical relevance and the need for a better clinical solution render defects of the cranial skeleton an ideal target for development of regenerative strategies focused on calvarial bone. With the improved understanding of the instructive properties of tissue-specific extracellular matrices and the advent of precise nanoscale modulation in materials science, strategies in regenerative medicine have shifted in paradigm. Previously considered to be simple carriers of stem cells and growth factors, increasing evidence exists for differential materials directing lineage specific differentiation of progenitor cells and tissue regeneration. In this work, we review the clinical challenges for calvarial reconstruction, the anatomy and physiology of bone, and extracellular matrix-inspired, collagen-based materials that have been tested for in vivo cranial defect healing.

Autogenous Bone Reconstruction of Large Secondary Skull Defects

BACKGROUND

The authors sought to ascertain the upper limits of secondary skull defect size amenable to autogenous reconstructions and to examine outcomes of a surgical series. Published data for autogenous and alloplastic skull reconstructions were also examined to explore associations that might guide treatment.

METHODS

A retrospective review of autogenously reconstructed secondary skull defects was undertaken. A structured literature review was also performed to assess potential differences in reported outcomes between autogenous bone and synthetic alloplastic skull reconstructions. Weighted risks were calculated for statistical testing.

RESULTS

Ninety-six patients underwent autogenous skull reconstruction for an average defect size of 93 cm (range, 4 to 506 cm) at a mean age of 12.9 years. The mean operative time was 3.4 hours, 2 percent required allogeneic blood transfusions, and the average length of stay was less than 3 days. The mean length of follow-up was 28 months. There were no postoperative infections requiring surgery, but one patient underwent secondary grafting for partial bone resorption. An analysis of 34 studies revealed that complications, infections, and reoperations were more commonly reported with alloplastic than with autogenous reconstructions (relative risk, 1.57, 4.8, and 1.48, respectively).

CONCLUSIONS

Autogenous reconstructions are feasible, with minimal associated morbidity, for patients with skull defect sizes as large as 500 cm. A structured literature review suggests that autogenous bone reconstructions are associated with lower reported infection, complication, and reoperation rates compared with synthetic alloplasts. Based on these findings, surgeons might consider using autogenous reconstructions even for larger skull defects.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Titanium cranioplasty in children and adolescents

Full thickness calvarial defects present considerable challenges to reconstructive surgeons. In paediatric cases, the use of biomaterials as a substrate for cranioplasty rather than autologous bone is controversial. Alloplastic cranioplasty in adults is supported by several large case series however long term outcome of biomaterial use in paediatric cases is limited. Retrospective seven year analysis of departmental database and clinical records identified 22 patients aged under 18 who had undergone 23 custom made titanium cranioplasties by a single surgeon using the same technique. Data including patient demographics, reason for craniectomy and complications experienced following surgery was obtained. The mean age at operation was 12 years 9 months. The mean defect size was 44.3 cm(2). No significant complications related to the cranioplasty were recorded in the early post operative period or during long term review (average follow up 4 years 6 months). No cranioplasty implant required removal. This retrospective case series shows that custom made patient specific titanium cranioplasty is a viable alternative to autologous bone as a reconstructive material in paediatric patients under specific circumstances.

Computer-Aided Design and Computer-Aided Manufacturing Hydroxyapatite/Epoxide Acrylate Maleic Compound Construction for Craniomaxillofacial Bone Defects

The aim of this study was to investigate the use of computer-aided design and computer-aided manufacturing hydroxyapatite (HA)/epoxide acrylate maleic (EAM) compound construction artificial implants for craniomaxillofacial bone defects. Computed tomography, computer-aided design/computer-aided manufacturing and three-dimensional reconstruction, as well as rapid prototyping were performed in 12 patients between 2008 and 2013. The customized HA/EAM compound artificial implants were manufactured through selective laser sintering using a rapid prototyping machine into the exact geometric shapes of the defect. The HA/EAM compound artificial implants were then implanted during surgical reconstruction. Color-coded superimpositions demonstrated the discrepancy between the virtual plan and achieved results using Geomagic Studio. As a result, the HA/EAM compound artificial bone implants were perfectly matched with the facial areas that needed reconstruction. The postoperative aesthetic and functional results were satisfactory. The color-coded superimpositions demonstrated good consistency between the virtual plan and achieved results. The three-dimensional maximum deviation is 2.12 ± 0.65  mm and the three-dimensional mean deviation is 0.27 ± 0.07  mm. No facial nerve weakness or pain was observed at the follow-up examinations. Only 1 implant had to be removed 2 months after the surgery owing to severe local infection. No other complication was noted during the follow-up period. In conclusion, computer-aided, individually fabricated HA/EAM compound construction artificial implant was a good craniomaxillofacial surgical technique that yielded improved aesthetic results and functional recovery after reconstruction.

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

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

Hydrogels That Allow and Facilitate Bone Repair, Remodeling, and Regeneration

Bone defects can originate from a variety of causes, including trauma, cancer, congenital deformity, and surgical reconstruction. Success of the current "gold standard" treatment (i.e., autologous bone grafts) is greatly influenced by insufficient or inappropriate bone stock. There is thus a critical need for the development of new, engineered materials for bone repair. This review describes the use of natural and synthetic hydrogels as scaffolds for bone tissue engineering. We discuss many of the advantages that hydrogels offer as bone repair materials, including their potential for osteoconductivity, biodegradability, controlled growth factor release, and cell encapsulation. We also discuss the use of hydrogels in composite devices with metals, ceramics, or polymers. These composites are useful because of the low mechanical moduli of hydrogels. Finally, the potential for thermosetting and photo-cross-linked hydrogels as three-dimensionally (3D) printed, patient-specific devices is highlighted. Three-dimensional printing enables controlled spatial distribution of scaffold materials, cells, and growth factors. Hydrogels, especially natural hydrogels present in bone matrix, have great potential to augment existing bone tissue engineering devices for the treatment of critical size bone defects.

Skull Reconstruction with Custom Made Three-Dimensional Titanium Implant

Background

Source material used to fill calvarial defects includes autologous bones and synthetic alternatives. While autologous bone is preferable to synthetic material, autologous reconstruction is not always feasible due to defect size, unacceptable donor-site morbidity, and other issues. Today, advanced three-dimensional (3D) printing techniques allow for fabrication of titanium implants customized to the exact need of individual patients with calvarial defects. In this report, we present three cases of calvarial reconstructions using 3D-printed porous titanium implants.

Methods

From 2013 through 2014, three calvarial defects were repaired using custommade 3D porous titanium implants. The defects were due either to traumatic subdural hematoma or to meningioma and were located in parieto-occipital, fronto-temporo-parietal, and parieto-temporal areas. The implants were prepared using individual 3D computed tomography (CT) data, Mimics software, and an electron beam melting machine. For each patient, several designs of the implant were evaluated against 3D-printed skull models. All three cases had a custom-made 3D porous titanium implant laid on the defect and rigid fixation was done with 8 mm screws.

Results

The custom-made 3D implants fit each patient's skull defect precisely without any dead space. The operative site healed without any specific complications. Postoperative CTs revealed the implants to be in correct position.

Conclusion

An autologous graft is not a feasible option in the reconstruction of large calvarial defects. Ideally, synthetic materials for calvarial reconstruction should be easily applicable, durable, and strong. In these aspects, a 3D titanium implant can be an optimal source material in calvarial reconstruction.

Simultaneous cranioplasty and subdural-peritoneal shunting for contralateral symptomatic subdural hygroma following decompressive craniectomy

BACKGROUND

Contralateral subdural hygroma caused by decompressive craniectomy tends to combine with external cerebral herniation, causing neurological deficits.

MATERIAL AND METHODS

Nine patients who underwent one-stage, simultaneous cranioplasty and contralateral subdural-peritoneal shunting were included in this study. Clinical outcome was assessed by Glasgow Outcome Scale as well as Glasgow Coma Scale, muscle power scoring system, and complications.

RESULTS

Postoperative computed tomography scans demonstrated completely resolved subdural hygroma and reversed midline shifts, indicating excellent outcome. Among these 9 patients, 4 patients (44%) had improved GOS following the proposed surgery. Four out of 4 patients with lethargy became alert and orientated following surgical intervention. Muscle strength improved significantly 5 months after surgery in 7 out of 7 patients with weakness. Two out of 9 patients presented with drowsiness due to hydrocephalus at an average time of 65 days after surgery. Double gradient shunting is useful to eliminate the respective hydrocephalus and contralateral subdural hygroma.

CONCLUSION

The described surgical technique is effective in treating symptomatic contralateral subdural hygroma following decompressive craniectomy and is associated with an excellent structural and functional outcome. However, subdural-peritoneal shunting plus cranioplasty thoroughly resolves the subdural hygroma collection, which might deteriorate the cerebrospinal fluid circulation, leading to hydrocephalus.

Predictors of infections following cranioplasty: a retrospective review of a large single center study

Introduction. The variables that predispose to postcranioplasty infections are poorly described in the literature. We formulated a multivariate model that predicts the risk of infection in patients undergoing cranioplasty. Method. Retrospective review of all patients who underwent cranioplasty following craniectomy from January, 2000, to December, 2011. Tested predictors were age, sex, diabetic status, hypertensive status, reason for craniectomy, urgency status of craniectomy, location of cranioplasty, reoperation for hematoma, hydrocephalus postcranioplasty, and material type. A multivariate logistic regression analysis was performed. Results. Three hundred forty-eight patients met the study criteria. Infection rate was 26.43% (92/348). Of these cases with infection, 56.52% (52/92) were superficial (supragaleal), 43.48% (40/92) were deep (subgaleal), and 31.52% (29/92) were present in both the supragaleal and subgaleal spaces. The predominant pathogen was coagulase-negative staphylococcus (30.43%) followed by methicillin-resistant Staphylococcus aureus (22.83%) and methicillin-sensitive Staphylococcus aureus (15.22%). Approximately 15.22% of all cultures were polymicrobial. Multivariate analysis revealed convex craniectomy, hemorrhagic stroke, and hydrocephalus to be associated with an increased risk of infection (OR = 14.41; P < 0.05, OR = 4.33; P < 0.05, OR = 1.90; P = 0.054, resp.). Conclusion. Many of the risk factors for infection after cranioplasty are modifiable. Recognition and prevention of the risk factors would help decrease the infection's rate.

Histopathology of subcutaneously preserved autologous bone flap after decompressive craniectomy: a prospective study

BACKGROUND

Limited reports are available regarding the viability of subcutaneously preserved autologous bone flaps after decompressive craniectomy. The present study was undertaken to evaluate the histopathological changes in these autologous bone flaps.

METHODS

Between January 2011 and July 2012, 50 patients were prospectively studied at the time of cranioplasty. Bone flap retrieved from the abdominal wall was subjected to histopathological examination to look for mononuclear cell infiltration into the Haversian system, presence of osteocytes, osteoblastic activity, angiogenesis and new bone formation. Microbiological culture of bone specimens was also done.

RESULTS

Of the 50 patients, there were 40 cases of trauma, 6 of aneurysmal bleed, 2 of tumor, and a single case of intracerebral hemorrhage and middle cerebral artery infarct, respectively. Mean age of the patients was 35.8 years (range, 10-64 years). Histopathological examination revealed the presence of osteocytes in 86 %, which indicates the viability of bone flaps. Osteoblastic activity was noted in 38 % and angiogenesis in 14 % of bone flaps, respectively. New bone formation was found in 6 %, and all had underlying osteoblastic activity. No significant correlation was found between the presence of osteocytes, osteoblasts, angiogenesis and duration of preservation of bone flaps. Acinetobacter species were cultured in a single patient. However, there was no evidence of clinical infection.

CONCLUSIONS

Subcutaneously preserved bone flap in the anterior abdominal wall remains viable and retains its osteogenic potential, and it is a simple, cost-effective option for storage of bone flaps during decompressive craniotomy. It has a negligible infection rate.

Intraoperative fabrication of patient-specific moulded implants for skull reconstruction: single-centre experience of 28 cases

BACKGROUND

Intraoperatively fabricated polymethylmethacrylate (PMMA) implants based on computer-designed moulds were used to improve cosmetic results after hard tissue replacement. To assess the implant's cosmetic and functional results we performed both subjective and objective assessments.

METHODS

This retrospective analysis was performed using a cohort of 28 patients who received PMMA implants between February 2009 and March 2012. The cosmetic and functional results were assessed using a patient questionnaire. Furthermore an objective volumetric subtraction score (0-100) was applied and implant thickness, as well as gaps and tiers, were measured.

RESULTS

Patients mainly judged their cosmetic result as "good". Two of the 28 patients found their cosmetic result unfavourable. The functional result and stability was mainly judged to be good. Measurements of implant thickness showed a very high correlation with the thickness of the contralateral bone. Volumetric subtraction led to a median quality of 80 on a scale from 0 to 100. Median gaps around the margins of the implant were 1.5 mm parietally, 1.7 mm frontally and 3.5 mm fronto-orbitally, and median tiers were 1.2 mm, 0 mm and 0 mm respectively. The overall rate of surgical revisions was 10.7 % (three patients). Two patients suffered from wound healing disturbances (7.1 %). The overall complication rate was comparable to other reports in the literature.

CONCLUSIONS

Implantation of intraoperatively fabricated patient-specific moulded implants is a cost-effective and safe technique leading to good clinical results with a low complication rate.

Three-layered osteodural plasty for severe anterior skull base and facial injuries. Report of eleven cases

BACKGROUND AND PURPOSE

The upper cranial trauma of high force and wide area of application leads to fractures of calvaria, the skull base, and the viscerocranium. The aim of the study was to present eleven patients treated for severe anterior skull base and facial defects by means of three-layered osteodural plasty.

MATERIALS AND METHODS

The operative tactics consisted of bicoronal incision, bifrontal craniotomy, closure of the dura mater damage with a pericranium, reconstruction of bone defects with autologous bone grafts and plasty with anteriorly pedicled pericranial flap on the supratrochlear and supraorbital vessels.

RESULTS

During follow-up, which lasted 2-7 years, none of the patients developed any early or late postoperative complications.

CONCLUSIONS

The three-layer osteodural plasty of severe anterior skull base injuries with the use of autologous bone grafts for the reconstruction of craniofacial skeleton resulted in a good final functional, morphological and aesthetic outcome in all patients.

Inflammatory cell response to calcium phosphate biomaterial particles: an overview

Bone is a metabolically active and highly organized tissue consisting of a mineral phase of hydroxyapatite (HA) and amorphous calcium phosphate (CaP) crystals deposited in an organic matrix. One objective of bone tissue engineering is to mimic the chemical and structural properties of this complex tissue. CaP ceramics, such as sintered HA and beta-tricalcium phosphate, are widely used as bone substitutes or prosthesis coatings because of their osteoconductive properties. These ceramic interactions with tissues induce a cell response that can be different according to the composition of the material. In this review, we discuss inflammatory cell responses to CaP materials to provide a comprehensive overview of mechanisms governing the integration or loosening of implants, which remains a major concern in tissue engineering. A focus on the effects of the functionalization of CaP biomaterials highlights potential ways to increase tissue integration and limit rejection processes.

Verifying three-dimensional skull model reconstruction using cranial index of symmetry

BACKGROUND

Difficulty exists in scalp adaptation for cranioplasty with customized computer-assisted design/manufacturing (CAD/CAM) implant in situations of excessive wound tension and sub-cranioplasty dead space. To solve this clinical problem, the CAD/CAM technique should include algorithms to reconstruct a depressed contour to cover the skull defect. Satisfactory CAM-derived alloplastic implants are based on highly accurate three-dimensional (3-D) CAD modeling. Thus, it is quite important to establish a symmetrically regular CAD/CAM reconstruction prior to depressing the contour. The purpose of this study is to verify the aesthetic outcomes of CAD models with regular contours using cranial index of symmetry (CIS).

MATERIALS AND METHODS

From January 2011 to June 2012, decompressive craniectomy (DC) was performed for 15 consecutive patients in our institute. 3-D CAD models of skull defects were reconstructed using commercial software. These models were checked in terms of symmetry by CIS scores.

RESULTS

CIS scores of CAD reconstructions were 99.24±0.004% (range 98.47-99.84). CIS scores of these CAD models were statistically significantly greater than 95%, identical to 99.5%, but lower than 99.6% (p<0.001, p = 0.064, p = 0.021 respectively, Wilcoxon matched pairs signed rank test). These data evidenced the highly accurate symmetry of these CAD models with regular contours.

CONCLUSIONS

CIS calculation is beneficial to assess aesthetic outcomes of CAD-reconstructed skulls in terms of cranial symmetry. This enables further accurate CAD models and CAM cranial implants with depressed contours, which are essential in patients with difficult scalp adaptation.

A new custom made bioceramic implant for the repair of large and complex craniofacial bone defects

INTRODUCTION

Neurosurgery and Maxillofacial Surgery Departments of Limoges University Hospital Centre have developed a new concept of a custom made ceramic implant in hydroxyapatite (HA) for the reconstruction of large and complex craniofacial bone defects (more than 25 cm(2)).

MATERIALS AND METHODS

The manufacturing process of the implants used a stereolithography technique that produces implants with three-dimensional shapes derived directly from the scan file of the patient's skull without moulding or machining. Eight patients received 8 implants between 2005 and 2008.

RESULTS

The surgical procedure is simple and fast. The post-operative follow-up was 12 months. No major complications (infection or fracture of the implant) were observed. The cosmetic result was considered satisfactory by both patients and surgeons.

CONCLUSIONS

These new implants are well suited for reconstruction of large craniofacial bone defects (greater than 25 cm(2)) in adults and children over 8 years.