Technique for methyl methacrylate cranioplasty to optimize cosmetic outcome

Next-generation personalized cranioplasty treatment

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

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.

A Customized Technique of Cranioplasty for Patients with Large Skull Defects: A Technical Note

OBJECTIVE

In our technical note, we have presented a technique of cranioplasty for large skull defects.

METHODS

A thin-slice computed tomography scan is performed. A model of the skull is constructed using a desktop 3-dimensional printer from the computed tomography scan. The skull model is filled with towels of soft cotton and inserted in a sterile thin plastic bag. The implant is molded intraoperatively on the skull model under sterile conditions. After surgical exposure of the skull defect, the implant is inserted and fixed using miniplates and miniscrews. The technique was used in 6 patients and described in 2 representative cases.

RESULTS

The required time and cost are significantly lower than those for other techniques used for preoperative manufacture of implants. No technique-related complications occurred. The radiological and cosmetic results were satisfactory. In the present case series, no early or delayed complications occurred.

CONCLUSION

The presented technique is simple, safe, and time- and cost-effective. The technique and results are reproducible.

Accuracy Assessment of Molded, Patient-Specific Polymethylmethacrylate Craniofacial Implants Compared to Their 3D Printed Originals

The use of patient-specific implants (PSIs) in craniofacial surgery is often limited due to a lack of expertise and/or production costs. Therefore, a simple and cost-efficient template-based fabrication workflow has been developed to overcome these disadvantages. The aim of this study is to assess the accuracy of PSIs made from their original templates. For a representative cranial defect (CRD) and a temporo-orbital defect (TOD), ten PSIs were made from polymethylmethacrylate (PMMA) using computer-aided design (CAD) and three-dimensional (3D) printing technology. These customized implants were measured and compared with their original 3D printed templates. The implants for the CRD revealed a root mean square (RMS) value ranging from 1.128 to 0.469 mm with a median RMS (Q1 to Q3) of 0.574 (0.528 to 0.701) mm. Those for the TOD revealed an RMS value ranging from 1.079 to 0.630 mm with a median RMS (Q1 to Q3) of 0.843 (0.635 to 0.943) mm. This study demonstrates that a highly precise duplication of PSIs can be achieved using this template-molding workflow. Thus, virtually planned implants can be accurately transferred into haptic PSIs. This workflow appears to offer a sophisticated solution for craniofacial reconstruction and continues to prove itself in daily clinical practice.

Craniofacial Reconstruction by a Cost-Efficient Template-Based Process Using 3D Printing

Craniofacial defects often result in aesthetic and functional deficits, which affect the patient’s psyche and wellbeing. Patient-specific implants remain the optimal solution, but their use is limited or impractical due to their high costs. This article describes a fast and cost-efficient workflow of in-house manufactured patient-specific implants for craniofacial reconstruction and cranioplasty. As a proof of concept, we present a case of reconstruction of a craniofacial defect with involvement of the supraorbital rim. The following hybrid manufacturing process combines additive manufacturing with silicone molding and an intraoperative, manual fabrication process. A computer-aided design template is 3D printed from thermoplastics by a fused deposition modeling 3D printer and then silicone molded manually. After sterilization of the patient-specific mold, it is used intraoperatively to produce an implant from polymethylmethacrylate. Due to the combination of these 2 straightforward processes, the procedure can be kept very simple, and no advanced equipment is needed, resulting in minimal financial expenses. The whole fabrication of the mold is performed within approximately 2 hours depending on the template’s size and volume. This reliable technique is easy to adopt and suitable for every health facility, especially those with limited financial resources in less privileged countries, enabling many more patients to profit from patient-specific treatment.

Cranioplasty with autogenous bone flaps cryopreserved in povidone iodine: a long-term follow-up study

OBJECTIVE The aim of this study was to investigate the long-term therapeutic efficacy of cranioplasty with autogenous bone flaps cryopreserved in povidone iodine and explore the risk factors for bone resorption. METHODS Clinical data and follow-up results of 188 patients (with 211 bone flaps) who underwent cranioplasty with autogenous bone flaps cryopreserved in povidone-iodine were retrospectively analyzed. Bone flap resorption was classified into 3 types according to CT features, including bone flap thinning (Type I), reduced bone density (Type II), and osteolysis within the flaps (Type III). The extent of bone flap resorption was graded as mild, moderate, or severe. RESULTS Short-term postoperative complications included subcutaneous or extradural seroma collection in 19 flaps (9.0%), epidural hematoma in 16 flaps (7.6%), and infection in 8 flaps (3.8%). Eight patients whose flaps became infected and had to be removed and 2 patients who died within 2 years were excluded from the follow-up analysis. For the remaining 178 patients and 201 flaps, the follow-up duration was 24-122 months (mean 63.1 months). In 93 (46.3%) of these 201 flaps, CT demonstrated bone resorption, which was classified as Type I in 55 flaps (59.1%), Type II in 11 (11.8%), and Type III in 27 (29.0%). The severity of bone resorption was graded as follows: no bone resorption in 108 (53.7%) of 201 flaps, mild resorption in 66 (32.8%), moderate resorption in 15 (7.5%), and severe resorption in 12 (6.0%). The incidence of moderate or severe resorption was higher in Type III than in Type I (p = 0.0008). The grading of bone flap resorption was associated with the locations of bone flaps (p = 0.0210) and fragmentation (flaps broken into 2 or 3 fragments) (p = 0.0009). The incidence of bone flap collapse due to bone resorption was higher in patients who underwent ventriculoperitoneal (VP) shunt implantation than in those who did not (p = 0.0091). CONCLUSIONS Because of the low incidence rates of infection and severe bone resorption, the authors conclude that cranioplasty with autogenous bone flaps cryopreserved in povidone-iodine solution is safe and effective. The changes characteristic of bone flap resorption became visible on CT scans about 2 months after cranioplasty and tended to stabilize at about 18 months postoperatively. The bone resorption of autogenous bone flap may be classified into 3 types. The rates of moderate and severe resorption were much higher in Type III than in Type I. The grade of bone flap resorption was associated with bone flap locations. Fragmented bone flaps or those implanted in patients treated with VP shunts may have a higher incidence of bone flap collapse due to bone resorption.

In Situ Cranioplasty Technique for Immediate Calvarial Reconstruction to Optimize Cosmesis

OBJECTIVE

One of the goals of calvarial reconstruction after craniectomy is optimization of cosmesis. A simple technique for intraoperative generation of an implant based on the patient's native skull contour for immediate skull reconstruction after craniectomy is described.

METHODS

In this technique, a titanium mesh is molded to the contour of the skull in situ and temporarily secured to the calvarium before the craniectomy. After the definitive portion of the procedure, the implant is resecured using the predrilled holes in the skull.

RESULTS

In situ titanium cranioplasties are easily contoured to the patient's native skull before, and resecured after, craniectomy. Postoperative cosmesis is excellent.

CONCLUSIONS

In selected cases, this technique for in situ cranioplasty before craniectomy generates an implant that mimics the patient's calvarium and results in excellent cosmetic outcomes.

The feasibility of producing patient-specific acrylic cranioplasty implants with a low-cost 3D printer

OBJECT Commercially available, preformed patient-specific cranioplasty implants are anatomically accurate but costly. Acrylic bone cement is a commonly used alternative. However, the manual shaping of the bone cement is difficult and may not lead to a satisfactory implant in some cases. The object of this study was to determine the feasibility of fabricating molds using a commercial low-cost 3D printer for the purpose of producing patient-specific acrylic cranioplasty implants. METHODS Using data from a high-resolution brain CT scan of a patient with a calvarial defect posthemicraniectomy, a skull phantom and a mold were generated with computer software and fabricated with the 3D printer using the fused deposition modeling method. The mold was used as a template to shape the acrylic implant, which was formed via a polymerization reaction. The resulting implant was fitted to the skull phantom and the cranial index of symmetry was determined. RESULTS The skull phantom and mold were successfully fabricated with the 3D printer. The application of acrylic bone cement to the mold was simple and straightforward. The resulting implant did not require further adjustment or drilling prior to being fitted to the skull phantom. The cranial index of symmetry was 96.2% (the cranial index of symmetry is 100% for a perfectly symmetrical skull). CONCLUSIONS This study showed that it is feasible to produce patient-specific acrylic cranioplasty implants with a low-cost 3D printer. Further studies are required to determine applicability in the clinical setting. This promising technique has the potential to bring personalized medicine to more patients around the world.

Biodegradable Mineralized Collagen Plug for the Reconstruction of Craniotomy Burr-Holes: A Report of Three Cases

Objectives

In this case report, we describe the design, fabrication and clinical outcomes of a novel bioresorbable, mineralized collagen burr-hole plug for the reconstruction of craniotomy burr-holes.

Methods

Mineralized collagen burr-hole plugs were fabricated via a biomimetic mineralization process. The biomimetic mineralized collagen has a similar chemical composition and microstructure to natural bone tissue, thereby possessing good biocompatibility and osteoconductivity. The mineralized collagen burr-hole plugs were implanted into three patients, and clinical outcomes were evaluated at one-year follow-ups.

Results

All bone defects healed very well using the mineralized collagen burr-hole plugs, and there were no adverse reactions at the surgical sites.

Conclusions

The clinical outcomes indicated that the mineralized collagen was effective for reconstructing burr-holes in the skull after craniotomy.