Comparison of acrylic and titanium cranioplasty#

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

Background:

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 PMMA has been superseded by titanium or Polyetheretherketone implants, prefabricated commercially from preoperative CT scans, and boasting superior clinical and cosmetic outcomes.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

Methods:

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

Results:

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

Conclusion:

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

Materials Used in Cranial Reconstruction: A Systematic Review and Meta-Analysis

BACKGROUND

Cranioplasty is a common neurological procedure with complication rates ranging from 20% to 50%. It is hypothesized that the risks of various complications are impacted by which material is used for cranioplasty.

OBJECTIVE

To evaluate existing literature comparing rates of complications following cranioplasty using different materials including autologous bone, hydroxyapatite, methyl methacrylate (MMA), demineralized bone matrix, polyetheretherketone, titanium, or composite materials.

METHODS

PubMed/MEDLINE database was searched for relevant articles published between 2010 and 2020. After screening, 35 articles were included. Outcomes included infection, wound problems, poor cosmesis, overall complications, duration of surgery, and length of stay. For each outcome, a frequentist network meta-analysis was conducted to compare materials used.

RESULTS

The risk of infection was 1.62 times higher when MMA was used compared to autologous bone (RR 1.62, 95% CI 1.07 to 2.45). Length of stay following cranioplasty was on average 3.62 days shorter when titanium was used compared autologous bone (95% CI -6.26 to -0.98). The networks constructed for other outcomes demonstrated moderate to substantial between-study heterogeneity, wide confidence intervals, and no significant differences between materials.

CONCLUSIONS

The quality of existing literature on this topic is relatively poor, almost exclusively comprised of single-center retrospective studies. There is currently not strong enough evidence available to make comprehensive conclusions regarding the risk-profiles of various cranioplasty materials across multiple outcomes. Prospective randomized trials are necessary to confirm the significant results found in this analysis and to further elucidate the differential risks of various cranioplasty materials.

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.

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).

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

BACKGROUND

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

OBJECTIVE

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

DESIGN

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

CONCLUSIONS

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

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.

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.

Post-Cranioplasty Complications: Lessons From a Prospective Study Assessing Risk Factors

ABSTRACT

Complication rate related with cranioplasty is described as very high in most of relevant studies. The aim of our study was to try to identify possible factors, that could predict complications following cranioplasty. The authors hypothesized that some physical characteristics on the preoperative brain computed tomography (CT) scan can be predictive for complications.The authors carried out a prospective observational study. All patients were adults after decompressive craniectomy, planned for cranioplasty and had a brain CT scan the day before cranioplasty. Our data pool included demographics, reason of craniectomy, various radiological parameters, the time of cranioplasty after craniectomy, the type of cranioplasty bone flap, and the complications.Twenty-five patients were included in the study. The authors identified statistically significant correlation between time of cranioplasty after craniectomy and the complications, as well as between the type of cranioplasty implant and the complications. There was statistically significant correlation between complications and the distance of the free brain surface from the level of the largest skull defect dimension - free brain surface deformity (FBSD). Moreover, the correlation between FBSD and the time of cranioplasty was statistically significant.It seems that for adult patients with unilateral DC the shorter time interval between craniectomy and cranioplasty lowers the risk for complications. The risk seems to be decreased further, by using autologous bone flap. Low values of the FBSD increase the risk for complications. This risk factor can be avoided, by shortening the time between craniectomy and cranioplasty.

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.

Complications of cranioplasty following decompressive craniectomy for traumatic brain injury: systematic review and meta-analysis

BACKGROUND

Decompressive craniectomy (DC) is a common neurosurgical intervention for severe traumatic brain injury (TBI), as well as malignant stroke, malignancy and infection. DC necessitates subsequent cranioplasty. There are significant demographic differences between TBI and non-TBI patients undergoing cranioplasty, which may influence their relative risk profiles for infection, aseptic bone flap resorption (aBFR) and re-operation.

OBJECTIVE

Perform a meta-analysis to determine the relative infection, aBFR and re-operation risk profiles of TBI patients as compared to other indications for DC.

METHODS

A systematic review and meta-analysis was performed in accordance with the PRISMA guidelines. PubMed, MEDLINE, EMBASE and Google Scholar were searched until 26/11/2020. Studies detailing rates of infection, re-operation and/or aBFR in specific materials and the post-TBI population were included, while studies in paediatrics or craniosynostosis repair were excluded.

RESULTS

Twenty-six studies were included. There was no difference in relative risk of infection between TBI and non-TBI cohorts (RR 0.81, 95% CI 0.57-1.17), with insignificant heterogeneity (I² = 33%). TBI was a risk factor for aBFR (RR 1.54, 95% CI 1.25-1.89), with no significant heterogeneity (I² = 13%). TBI was a risk factor for re-operation in the autologous sub-group (RR 1.49, 95% CI 1.05-2.11) but not in the alloplastic sub-group (RR = 0.86, 95% CI 0.34-2.18). Heterogeneity was insignificant (I² = 11%).

CONCLUSION

TBI is a risk factor for aBFR and re-operation following cranioplasty. Use of an alloplastic graft for primary cranioplasty in these patients may partially mitigate this increased risk.

Complications following titanium cranioplasty compared with nontitanium implants cranioplasty: A systematic review and meta-analysis

Decompressive craniectomy is widely used to treat medically refractory intracranial hypertension. There were still few studies focusing on the complications between titanium cranioplasty with non-titanium materials cranioplasty. Our systematic review and meta-analysis aimed to assess the complications following titanium cranioplasty and to make a comparison with nontitanium materials. A systematic review was used to review titanium cranioplasty characters in recent articles. A systematic literature review and meta-analysis were performed by using PubMed/MEDLINE, Scopus, the Cochrane databases and Embase for studies reporting on cranioplasty procedures that compared complication outcomes between titanium with non-titanium materials. The final 15 studies met inclusion criteria and represented 2258 cranioplasty procedures (896 titanium, 1362 nontitanium materials). Overall complications included surgical site infection, hematoma, implant exposure, seizure, cerebrospinal fluid leak, imprecise fitting. Titanium cranioplasty was associated with a significant decrease in overall complications rate (OR, 0.72; P = 0.007), hematoma rate (OR, 0.31; P = 0.0003) and imprecise fitting rate (OR, 0.35; P = 0.04). However, it also suggested that titanium cranioplasty can be greatly increased implant exposure rate (OR, 4.11; P < 0.00001). Our results confirmed the advantages of titanium cranioplasty in reducing complications including hematoma, imprecise fitting, and also suggested that clinicians should pay more attention to postoperative implant exposure. With new synthetic materials emerging, it would also be interesting to study the cost-effect and functional outcomes associated with cranioplasty materials.

Alloplastic Cranioplasty Reconstruction: A Systematic Review Comparing Outcomes With Titanium Mesh, Polymethyl Methacrylate, Polyether Ether Ketone, and Norian Implants in 3591 Adult Patients

BACKGROUND

Acquired defects of the cranium represent a reconstructive challenge in patients with calvarial bone loss due to trauma, infection, neoplasia, congenital malformations, or other etiologies. The objective of this study was to compare postoperative rates of infection, local complications, and allograft failures following cranioplasty reconstruction using titanium mesh (Ti), polymethyl methacrylate (PMMA), polyether ether ketone (PEEK), and Norian implants in adult patients.

METHODS

This constitutes the first systematic review of available literature on 4 different methods of alloplastic cranioplasty reconstruction, including Ti, PMMA, PEEK, and Norian implants, using the Newcastle-Ottawa Quality Assessment Scale guidelines for article identification, screening, eligibility, and inclusion. Electronic literature search included Ovid MEDLINE/PubMed, EMBASE, Scopus, Google Scholar, and Cochrane Database. Pearson exact test was utilized at P < 0.05 level of significance (J.M.P. v11 Statistical Software).

RESULTS

A total of 53 studies and 3591 patients (mean age, 40.1 years) were included (Ti = 1429, PMMA = 1459, PEEK = 221, Norian = 482). Polymethyl methacrylate implants were associated with a significantly higher infection rate (7.95%, P = 0.0266) compared with all other implant types (6.05%). Polyether ether ketone implants were associated with a significantly higher local complication rate (17.19%, P = 0.0307, compared with 12.23% in all others) and the highest ultimate graft failure rate (8.60%, P = 0.0450) compared with all other implant types (5.52%).

CONCLUSIONS

This study qualifies as a preliminary analysis addressing the knowledge gap in rates of infection, local surgical complication, and graft failure in alloplastic cranioplasty reconstruction with different implant types in the adult population. Longer-term randomized trials are warranted to validate associations found in this study.

Is Three-Dimensional Virtual Planning in Cranial Reconstruction for Advanced Cutaneous Squamous Cell Carcinoma of the Skull a Feasible Option?

BACKGROUND

Cutaneous squamous cell carcinoma (cSCC) is a common type of malignant skin disorder. An uncommon feature is local bony invasion, as can rarely be seen in lesions on the scalp. The optimal treatment strategy in these rare cases is still under debate.

OBJECTIVE

The aim of this case report is to present a 1-stage three-dimensional planned surgical resection and reconstruction of a cSCC with bony invasion into the scalp and to discuss the alternative options and potential pitfalls.

MATERIALS AND METHODS

A patient diagnosed with rT4N0M0 cSCC of the scalp underwent a cranial resection and reconstruction in 1 stage. With the use of computer-assisted design and computer-assisted manufacturing a patient-specific implant (PSI) of poly (ether ether ketone) was manufactured. After the PSI was inserted, it was covered with a latissimus dorsi muscle and a split-thickness skin graft.

RESULTS

Intraoperatively the resection template generated an accurate resection and accurate and fast placement of the PSI. The reconstruction had a clinical satisfactory esthetic result, but was hampered by the development of a small wound dehiscence was observed over the postoperative course.

CONCLUSION

Three-dimensional planned resection and reconstruction for composite defects of the skull after resection of a cSCC of the scalp with bony invasion may lead to an accurate and predictable resection and accurate and fast placement of the PSI. However, patient specific characteristics should be considered to assess potential risks and benefits before opting for this one-stage treatment strategy.

Association between metal hypersensitivity and implant failure in patients who underwent titanium cranioplasty

OBJECTIVE

Digitally designed titanium plates are commonly used for the reconstruction of craniofacial defects, although implant exposure (referred to as failure) is one of the major complications. Metal hypersensitivities have been suggested as possible causes of implant failure of orthopedic, intravascular, gynecological, and dental devices, yet there has been no consensus on the requirement for allergy screening before cranioplasty.

METHODS

In this study, the authors prospectively investigated the prevalence of metal hypersensitivity in patients for whom cranioplasty is planned and assess its relationship with titanium implant failure (exposure).

RESULTS

Based on records from 207 included patients, 39.61% of patients showed hypersensitivity to at least one kind of metal. Approximately one-quarter (25.12%) of patients had multiple metal allergies. Co, Cd, and Zn were the 3 most frequently identified metal hypersensitivities. No allergy to titanium was detected in this study. The overall incidence of cranioplasty implant failure was 5.31% (11 of 207). Patients showing hypersensitivities to more than 3 kinds of metal had higher risks of titanium plate exposure.

CONCLUSIONS

Based on their findings, the authors suggest that routine allergy screening be performed before titanium plate cranioplasty. For patients with hypersensitivities to more than 3 metals, alternative materials, such as polyetheretherketone, should be considered for cranioplasty.

Effect of Pressure, Post-Pressing Time, and Polymerization Cycle on the Degree of Conversion of Thermoactivated Acrylic Resin

Herein, the effect of different post-pressing times and pressure in two cycles of polymerization on the degree of conversion (DC) of thermally activated acrylic resin (TRRA) is analyzed to optimize the polymerization of this material. After post-pressing for 0, 6, or 12 h, polymerization was performed with or without a pressure of 60 psi (0.41 MPa) in a short (4 h) or a long (11 h) cycle, totaling 12 groups. To determine the DC, PMMA specimens were analyzed by Fourier transform infrared spectroscopy. The influence of each factor alone on the DC was studied by experimental planning. The statistical tests used were three-way ANOVA, t-test, Tukey's test, and Levene's test, with a margin of error of 5%. Two groups prepared with post-pressing times of 12 h had the lowest DC (p < 0.001). Post-pressing times of 0 and 6 h did not yield statistically different results. Pressure increased the DC in only one group (long cycle +12 h, p=0.001). The short cycle resulted in a higher DC than the long cycle in 2 groups (with pressure +0 h, p=0.002; without pressure +6 h, p=0.015), while the long cycle yielded a statistically higher DC in only one group (with pressure +12 h, p < 0.001). The polymerization showed satisfactory DC in all 12 groups. Small differences found among the specimens indicate that the pressure, post-pressing time, and polymerization cycles herein were not influential factors for the DC of PMMA.

Complications with PMMA compared with other materials used in cranioplasty: a systematic review and meta-analysis

Polymethyl methacrylate (PMMA) has been considered a suitable material for cranioplasty. However, no consensus has been reached concerning the best material for cranioplasty with regard to minimizing complications. Thus, this systematic review and meta-analysis aimed to compare the complication rates of PMMA with those of autologous bone and titanium mesh. This review was registered with PROSPERO (CRD42016042725). Systematic searches were conducted on PubMed/MEDLINE, Scopus, and Web of Science. The focus question was, "Do PMMA prostheses used in cranioplasty have complications rates similar to those of autologous bone and titanium mesh?" A meta-analysis of complication rates was performed on the basis of dichotomous outcomes assessed by risk ratio (RR) with corresponding 95% confidence intervals (CI). From 1014 data sources, 11 articles were selected according to eligibility criteria. These articles involved 1,256 individuals and 1,278 cranioplasties using autologous bone (n = 408), PMMA (n = 379), or titanium (n = 151). The follow-up period ranged from 63 days to 54.3 months. No difference was observed between the complication rates of PMMA and autologous bone (p = 0.94; RR, 0.98; 95%CI, 0.54-1.75) or between PMMA and titanium (p = 0.38; RR, 1.59; 95%CI, 0.57-4.48). Sub-analysis of the reasons for craniotomy (trauma/non-trauma) was conducted, which revealed no significant difference (p = 0.91; RR, 0.95; 95%CI, 0.37-2.42). The meta-analysis indicated that the use of PMMA yields complication rates that are near those of autologous bone and titanium mesh.

Reconstruction of Large Calvarial Defects Using Titanium Mesh Versus Autologous Split Thickness Calvarial Bone Grafts: A Comprehensive Comparative Evaluation of the Two Major Cranioplasty Techniques

Background

Both alloplastic 3-D dynamic titanium mesh implants and Autogenous split calvarial cortico-cancellous bone grafts have been extensively used for cranial defect reconstruction. Whether either method is procedurally, cosmetically or therapeutically superior to the other, has rarely been studied or evaluated.

Aim

The aim of the study was to objectively examine, assess, evaluate and compare the procedural ease, convenience, safety and versatility of cranioplasty performed using titanium mesh implants versus split calvarial grafts and to compare the intra- and post-operative complications encountered, and the cosmetic and therapeutic outcomes achieved using these two cranioplasty techniques.

Material and Methods

A retrospective analysis was carried out on 40 patients with large post-craniectomy defects, who underwent cranioplasty between 2012 and 2016. Twenty patients underwent cranioplasty with titanium mesh implants and 20 with split calvarial cortico-cancellous bone grafts. Post-operative follow-up ranged from 1 to 5 years and the patients were observed (clinically as well as by means of radiographs and CT scans) for cosmetic, functional and neurological improvements.

Results

Titanium mesh cranioplasty afforded more benefits, such as a shorter operating time, ease in manipulation, absence of donor-site morbidity, usefulness in previously infected or compromised recipient sites, absence of the risk of graft resorption or rejection, and a ready means to aspirate any post-operative epidural collection through its mesh structure. It also compared favorably when the cranial defects were large, owing to its, so to speak, limitless supply viz a viz, the relative paucity of harvestable split calvarial bone autograft.

Conclusion

Both modalities have their pros and cons. Split calvarial grafting is the more physiologic and less expensive option, useful for small- to medium-sized defects, while titanium mesh is the safer, more versatile, reliable and often preferred option, particularly when the cranial defects are large and also in severe head injury patients in whom harvesting calvarial bone could further compromise the already traumatized calvarium with possible stress fractures, further endangering its vital contents.

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.

Cranioplasty of Large Cranial Defects With Porous Polyethylene Implants

BACKGROUND

Reconstruction of cranial defects due to trauma or other causes has been carried out since ages with a wide variety of materials. The aim of reconstruction was mainly to restore cosmesis and protect the brain from further injury. However, recent studies have shown that cranioplasty not only improves the cerebral blood flow but also leads to improvement of cognitive functions. The materials used include autologous bone, allogeneic bone, xenografts, and alloplasts. The search for an ideal material continues. The authors present their experience with cranioplasty using prefabricated porous polyethylene implants.

MATERIALS AND METHODS

Patients requiring cranioplasty for reconstruction of large sized (more than 15 cm in any 1 dimension) cranial defects were selected. Three patients were men and 2 were women. The age group of the patient ranged from 18 to 58 years. Preformed Biopore Hemisphere was used in every patient for cranial reconstruction.

RESULTS

No complications were seen in our patients. One patient who had undergone titanium cranioplasty previously showed remarkable improvement in cognitive functions.

CONCLUSION

Porous polyethylene prefabricated implants are a good restorative material for reconstruction of large cranial defects.

Complications of skull reconstruction after decompressive craniectomy

INTRODUCTION

Decompressive craniectomy can be a life-saving procedure. Later reconstruction of the skull using the stored bone flap ("cranioplasty") is often associated with complications. These complications require new procedures and often result in the reconstruction of the skull using an expensive patient-specific cranial implant.

PATIENTS & METHODS

All adult patients who underwent cranioplasty after decompressive craniectomy in the last 10 years in our center were included (74 patients). Bone flap size, duration of the procedure, age, and other clinical parameters were included in our analysis.

RESULTS

29.7% of our patients who received in the first place an autologous cranioplasty developed a complication which necessitated removal of the bone flap and the implantation of a custom-made implant. Descriptive statistics demonstrate a significantly higher amount of complications in younger patients (20-40 years, p = 0.027). We also saw a trend toward lower complications when bone flaps were stored according to a biobank protocol (p = 0.075).

CONCLUSIONS

Cranioplasty using the stored bone flap after decompressive craniectomy is associated with a high percentage of complications. Selecting patients at risk could possibly indicate cases where an immediate custom-made implant technique would be required.

Polymethylmethacrylate imbedded with antibiotics cranioplasty: An infection solution for moderate and large defects reconstruction?

Background:

In cases where autologous bone graft reconstruction is not possible (such as comminuted fractures, bone graft reabsorption, or infection) and the use of synthetic material is required, polymethylmethacrylate (PMMA) use is a safe and efficient solution. Studies comparing the incidence of postoperative complications between autologous and synthetic cranioplasty are heterogeneous, not allowing a conclusion of which is the best material for skull defects reconstruction. Current medical literature lacks prospective well-delineated studies with long-term follow-up that analyze the impact of antibiotic use in PMMA cranial reconstruction of moderate and large defects.

Methods:

A prospective series of patients, who underwent cranioplasty reconstruction with PMMA impregnated with antibiotic, were followed for 2 years. Authors collected data regarding demographic status, clinical conditions, surgical information, and its complications.

Results:

A total of 58 patients completed full follow-up with a mean group age of 40 years and a male predominance (77%). Major complications that required surgical management were identified in 5 patients, and 10 patients evolved with minor complications. Postoperative surgical site infection incidence was 3.2%.

Conclusion:

The infection rate in patients submitted to PMMA flap cranioplasty impregnated with antibiotic is significantly inferior comparing to the data described in medical literature. A lower infection incidence impacts secondary endpoints such as minimizing surgical morbidity, mortality, hospitalization period, and, consequently, costs.

Warfare-related secondary anterior cranioplasty

BACKGROUND

Anterior cranial bone defects secondary to global war cranial defects pose a unique reconstructive challenge. The objective of this study was to evaluate the outcomes of alloplastic reconstructions of cranial bone with titanium mesh and fat graft after warfare-related cranial trauma.

PATIENTS AND METHODS

Thirty-five patients at the plastic and reconstructive surgery ward of our hospital underwent anterior cranioplasty with titanium mesh with or without fat grafts from lower abdominal wall. Inclusion criteria were anterior cranial bone defect due to warfare injuries, the mean age of these patients was 31 years (range, 23-48 years). Ninety-five percent were male, and 5% were female. Average follow-up was 12 months. Fat grafts were used to help obliterate endocranial dead spaces.

RESULTS

Twenty-five patients (71%) had more than 0.5 cm dead space under cranial defects, and we used fat graft under the titanium mesh. The majority groups of patients (80%) were injured as a result of previous explosive device blasts with or without neurosurgical procedures in the past. The average patient age was 31 years, and 95% of patients were male. The mean anterior cranial defect size was 6 cm × 8 cm, and there were no wound infection or flap necrosis after operations.

CONCLUSION

We recommend this procedure (titanium mesh with or without fat graft) for warfare injured cranial defects in secondary anterior cranial reconstructions. Fat grafts eliminates dead space and reduce secondary complications.

Cranioplasty of Hemispherical Defects Using High Impact Methylmethacrylic Plate

Decompressive craniectomy is the most common neurosurgical procedure performed in today's scenario, usually posttrauma or a cerebrovascular event. Cranioplasty is the repair of a cranial defect or deformation. In the last decade, there has been an increase in the number of cranioplasties performed because of an increase in the number of decompressive craniectomies. Although the main purpose of cranioplasty is to protect the brain and restore aesthetics, it has been proved beyond doubt that there is also an improvement in function and patient self-esteem.Reconstructing the skull after a decompressive craniectomy is a challenge because of the size and contour of the defect, the projection of the brain outside in many cases, and the attendant risks of infection, hematoma, seizures, and CSF leak. In the last few decades, an enormous array of biomaterials has been used for cranioplasty, but there is no consensus on the best material. Each has its own advantages and disadvantages. Polymethylmethacrylate has been used for cranioplasty since the World War II and is still the most widely used reconstructive material.

MATERIALS AND METHODS

Patients requiring reconstruction of hemispherical cranial defects were taken up for the study. An impression of the defect was taken over the skin using impression compound first and then silicone impression material. The model was trimmed to size, and an acrylic plate was made from High Impact Acrylic. Under general anesthesia, the acrylic plate was fixed to the margins of the defect using titanium plates and screws. Suction drain was placed and the wound closed with Vicryl Rapid. All patients were followed up for 2 years to note any postoperative complications and change in neurological status. There were 12 male patients and 3 female patients. Age of the patients ranged between 8 and 55 years.

RESULTS

All patients were happy with the aesthetic results. There were no complications in all our patients. A few patients showed dramatic improvement in their neurological status.

CONCLUSION

High Impact Acrylic is an excellent restorative material for reconstructing large sized cranial defects.

Factors influencing the outcome (GOS) in reconstructive cranioplasty

After performing a decompressive craniectomy, a cranioplastic surgery is usually warranted. The complications of this reconstructive procedure may differ from the initial operation. The authors of this study report on their experience to define patient-specific and procedural risk factors for possible complications following cranioplasty influencing the outcome (Glasgow Outcome Scale (GOS)), mobility, shunt dependency, and seizures. A retrospective analysis of 263 patients of all ages and both sexes who had undergone cranioplasty after craniectomy for traumatic brain injury (including chronic subdural hematoma), subarachnoidal hemorrhage (including intracerebral hemorrhage), ischemic stroke, and tumor surgery in one single center in 12 years from January 2000 to March 2012 has been carried out. A multiple logistic regression analysis was performed to identify potential risk factors (age, gender, used cranioplasty material, initial diagnosis, clipped or coil-embolized subarachnoidal hemorrhage (SAH) patients, time interval, complications especially hydrocephalus and seizures, mobility) upon the prognosis described as a dichotomized Glasgow Outcome Scale. Two hundred forty-eight patients met the study criteria. The overall complication rate after cranioplastic surgery was 18.5% (46 patients). Complications included: surgical site infection, epidural hematoma, hydrocephalus with or without former SAH, and new-onset seizures. Logistic regression analysis identified significant correlation between a low GOS (2 or 3) and postoperative seizures (OR 2.37, CI 1.35-4.18, p < 0.05), shunt-depending hydrocephalus (OR 5.83, CI 3.06-11.11, p < 0.05), and age between 51 and 70 years (OR 2.4, 95% CI 1.09-5.29, p = 0.029). However, gender, time interval between craniectomy and cranioplasty, initial diagnosis, and used cranioplasty material had no significant influence on post-cranioplasty complications as surgical site infections, hematoma, wound healing disturbance, seizures, or hydrocephalus. Evaluation of treatment modality in aneurysmal SAH clip vs. coil showed no significant relation to postoperative complications either. Complications after cranioplastic surgery are a common problem, as prognostic factors could identify a shunt-depending hydrocephalus and epilepsia to develop a major deficit after cranioplastic surgery (GOS 2 or 3). We detected a significant extra risk of people between the age of 51 and 70 years to end up in GOS level 2 or 3.

Cranioplasty outcomes and associated complications: A single-centre observational study

INTRODUCTION

The resurgence of decompressive craniectomy has led to recent published reviews of the safety of cranioplasties. To date there is a wide range of reported mortality and morbidity. This observational study reports the outcomes of the cranioplasty operations from a single centre and evaluates the factors involved in their management.

METHODS

A retrospective search of all theatre logs was performed for the years 2006-2013 inclusive. 88 operations were documented as 'Cranioplasty'. Data collection include patient demographics, type of cranioplasty used, time lapse between decompression and cranioplasty, seniority of the operating surgeon(s), antibiotic regimen and complications. Outcomes were recorded at the three-month follow-up.

RESULTS

The overall complication rate was 6.8%. The mean patient age was 36.2 years. 52.2% of patients had decompressive craniectomy for trauma, 11.3% had infectious pathology, 9% had subarachnoid haemorrhage, 9% had tumour with bone infiltration and 3.4% had stroke. 55.7% of patients had cranioplasty within 6 months of craniectomy. 61.3% of cranioplasties were with autologous bone, 20.4% titanium, 10.2% acrylic and 7.9% polyetheretherketone (PEEK). Significant complications included one case of infection, two cases of subgaleal haematoma and one extradural collection. No deaths were noted. No correlation was found between infection and the use of drains. 68.6% of cases were done by either a senior surgeon or a supervised registrar. There was an observable difference in complication rates in relation to the seniority and experience of the operator. However, patient numbers and complications were insufficient to achieve statistical significance. Strict antimicrobial prescribing was observed.

CONCLUSION

Some potentially preventable complications have been addressed with a resulting rate of complications lower than other published reports. We use two standard adjuncts: the presence of a senior surgeon and strict antimicrobial regimens. We believe that our results could be transferrable to other units by following similar guidelines.

Evolution of cranioplasty techniques in neurosurgery: historical review, pediatric considerations, and current trends

Cranial bone repair is one of the oldest neurosurgical practices. Reconstructing the natural contours of the skull has challenged the ingenuity of surgeons from antiquity to the present day. Given the continuous improvement of neurosurgical and emergency care over the past century, more patients survive such head injuries, thus necessitating more than ever before a simple, safe, and durable means of correcting skull defects. In response, numerous techniques and materials have been devised as the art of cranioplasty has progressed. Although the goals of cranioplasty remain the same, the evolution of techniques and diversity of materials used serves as testimony to the complexity of this task. This paper highlights the evolution of these materials and techniques, with a particular focus on the implications for managing pediatric calvarial repair and emerging trends within the field.

Clinical outcomes in cranioplasty: risk factors and choice of reconstructive material

BACKGROUND

Continuing advances in cranioplasty have enabled repair of increasingly complicated cranial defects. However, the optimal materials and approaches for particular clinical scenarios remain unclear. This study examines outcomes following cranioplasty for a variety of indications in patients treated with alloplastic material, autogenous tissue, or a combination of both.

METHODS THE AUTHORS CONDUCTED

a retrospective analysis on 180 patients who had 195 cranioplasties performed between 1993 and 2010.

RESULTS

Materials used for cranioplasty included alloplastic for 42.6 percent (83 of 195), autologous for 19.0 percent (37 of 195), and both combined for 38.5 percent (75 of 195). Mean defect size was 70.5 cm. A subset of patients had undergone previous irradiation (12.2 percent; 22 of 180) or had preoperative infections (30.6 percent; 55 of 180). The most common complication was postoperative infection (15.9 percent; 31 of 195). Factors that significantly predisposed to complications included preoperative radiation, previous infection, and frontal location. Preoperative radiation was the strongest predictor of having any postoperative complications, with an adjusted odds ratio of 6.91 (p < 0.005). Irradiated patients (OR, 7.96; p < 0.05) and patients undergoing frontal cranioplasties (OR, 2.83; p < 0.05) were more likely to require repeated operation. Preoperative infection predisposed patients to exposure of hardware in alloplastic reconstructions (OR, 3.13; p < 0.05).

CONCLUSIONS

Despite the evolution of cranioplasty techniques and materials, complications are not uncommon. The choice of reconstructive material may modify the risk of developing postoperative complications but appears less important than the clinical history in affecting outcome.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, III.

Technique for methyl methacrylate cranioplasty to optimize cosmetic outcome

BACKGROUND

Cranioplasty aims to reconstruct skull defects from fractures, decompressive craniectomies, tumors, and congenital anomalies in a cosmetically acceptable manner. We present a technique in methyl methacrylate cranioplasty that gives excellent cosmetic results by maintaining patient's calvarial curvature.

METHOD

Cranioplasty material is placed into a plastic bag and packed inside the defect. Wire mesh cut larger than the defect is held in position to take the exact skull curvature. Once solid, the implant is fixed in position using titanium plates and mini-screws.

CONCLUSION

This is a simple, inexpensive method of achieving the most cosmetically desired cranioplasty results.

Proposal for establishment of the UK Cranial Reconstruction Registry (UKCRR)

BACKGROUND

The increasing utilisation of decompressive craniectomy for traumatic brain injury and stroke has led to an increase in the number of cranioplasties undertaken. Cranioplasty is also undertaken following excision of tumours originating from or invading the skull vault, removal of bone flaps due to post-operative infection, and decompressive craniectomy for the management of rarer causes of brain oedema and/or refractory intracranial hypertension. The existing literature which mainly consists of single-centre, retrospective studies, shows a significant variation in practice patterns and a wide range of morbidity. There also exists a need to measure the outcome as perceived by the patients themselves with patient reported outcome measures (PROMs; functional outcome, quality of life, satisfaction with cosmesis). In the UK, the concept of long-term surveillance of neurosurgical implants is well established with the UK shunt registry. Based on this background, we propose to establish the UK Cranial Reconstruction Registry (UKCRR).

AIM

The overarching aim of the UKCRR is to collect high-quality data about cranioplasties undertaken across the UK and Ireland in order to improve outcomes for patients.

METHODS

Any patient undergoing reconstruction of the skull vault with autologous bone, titanium, or synthetic material in participating units will be eligible for inclusion. Data will be submitted directly by participating units to the Outcome Registry Intervention and Operation Network secure platform. A Steering Committee will be responsible for overseeing the strategic direction and running of the UKCRR.

OUTCOME MEASURES

These will include re-operation due to a cranioplasty-related issue, surgical site infection, re-admission due to a cranioplasty-related issue, unplanned post-operative escalation of care, adverse events, length of stay in admitting unit, destination at discharge from admitting unit, mortality at discharge from admitting unit, neurological status and PROMs during routine follow-up.

CONCLUSION

The UKCRR will be an important pillar in the ongoing efforts to optimise the outcomes of patients undergoing cranioplasty.

Seven years of cranioplasty in a regional neurosurgical centre

INTRODUCTION

In recent years craniectomy has been widely used in the management of traumatic brain injury and ischaemic stroke. The objective of this study was to evaluate the indications, techniques and outcomes for patients undergoing cranioplasty over a recent 7-year period in a geographically distinct population.

MATERIALS AND METHODS

An observational study was performed retrospectively, with review of case records from 2004 to 2011. Demographic, clinical and outcome data were collected, and complications were classified as major and minor. A multi-variant analysis was performed to identify patient and management factors that influenced outcome.

RESULTS

Data were collected on a total of 87 cranioplasty patients with a median age of 42 and a mean follow-up time of 3 years and 10 months. The main indications for craniectomy were trauma (46%), infection (19%) intracranial haemorrhage (15%), tumour (13%) and ischaemic stroke (6%). Eight percent of patients had a synchronous craniectomy and cranioplasty, 14% had cranioplasty within 3 months of craniectomy, 21% within 3-6 months, 35% within 6-12 months, 14% over 1 year and 8% over 2 years later. The most frequently implanted cranioplasty material was titanium (53%), followed by autologous bone (26%) and acrylic (15%). Administration of prophylactic antibiotics was recorded in 97% of cases. Major complications occurred in 20% of patients, including 2 deaths (2%), 5 extradural haemorrhages (6%) and 9 infections (10%). A further 10% of cases experienced minor or cosmetic complications.

CONCLUSIONS

Cranioplasty is often considered as a low-risk procedure following craniectomy. In our cohort, a 20% risk of major complications, including death, was identified. These findings contribute to the literature, emphasising that cranioplasty is a high-risk procedure. Whilst compelling reasons may guide the undertaking of craniectomy, it is essential that consideration is given to the significant subsequent risks of cranioplasty.