- Institute of Neurology and Neurosurgery, Hospital Zambrano Hellion, Tec Salud, Monterrey, Nuevo León, México
- Tecnológico de Monterrey School of Medicine and Health Sciences, Monterrey, Nuevo León, México
- Dentistry Lab Olazarán and Associates, Monterrey, Nuevo León, México
Dentistry Lab Olazarán and Associates, Monterrey, Nuevo León, México
DOI:10.4103/2152-7806.119535Copyright: © 2013 Caro-Osoria E This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Caro-Osorio E, la Garza-Ramos RD, Sergio R. Martínez-Sánchez, Félix Olazarán-Salinas. Cranioplasty with polymethylmethacrylate prostheses fabricated by hand using original bone flaps: Technical note and surgical outcomes. Surg Neurol Int 08-Oct-2013;4:136
How to cite this URL: Caro-Osorio E, la Garza-Ramos RD, Sergio R. Martínez-Sánchez, Félix Olazarán-Salinas. Cranioplasty with polymethylmethacrylate prostheses fabricated by hand using original bone flaps: Technical note and surgical outcomes. Surg Neurol Int 08-Oct-2013;4:136. Available from: http://sni.wpengine.com/surgicalint_articles/cranioplasty-with-polymethylmethacrylate-prostheses-fabricated-by-hand-using-original-bone-flaps-technical-note-and-surgical-outcomes/
Background:Decompressive craniectomies (DC) mandate future cranioplasties, accounting for the large array of biomaterials for this purpose. Polymethylmethacrylate (PMMA) is a very reliable thermoplastic that can be prefabricated or even molded intraoperatively to create an adequate prosthesis. Preformed PMMA implants made by hand have been superseded by newer 3-D printed implants, but this is accompanied by higher costs and timing issues, apart from having limited availability in developing and third-world countries.
Methods:A total of 26 patients were operated over a span of 11 years. A total of 26 custom hand-made PMMA prostheses were fabricated using original bone flaps with the aid of a prosthodontist, in a process that took approximately 70 minutes for each implant. The result was an exact duplication of the patient's bone flap.
Results:Of the 26 patients who underwent cranioplasty, the majority of patients were males, with a mean age of 39.2 years and traumatic brain injury as main indication for DC. After a mean interval of 2.4 months, all 26 patients underwent a cranioplasty and prosthesis placement. Only two patients (7.6%) suffered from direct cranioplasty-related complications after a median follow-up of 10.4 months. Median Glasgow Outcome Scale scores improved significantly from 3 to 4 after cranioplasty (P = 0.008).
Conclusion:Prefabrication of custom PMMA prostheses by hand when original bone flaps are available is an excellent alternative to newer 3-D printing techniques, because it is relatively cheaper, less time consuming, and offers excellent results in terms of anatomical reconstruction and improvement of neurological function in long-term follow-ups.
Keywords: Cranioplasty, decompressive craniectomy, prosthesis, polymethylmethacrylate
Cranioplasty is defined as the surgical repair of acquired defects or congenital deformities of the cranium. It is performed mainly for anatomical reconstruction, brain protection, and cosmetics, but evidence has shown that there is also improvement of brain physiology and patient self-esteem.[
Nowadays, DCs are the most common neurosurgical procedures requiring a future cranioplasty and they are usually performed after severe head trauma or severe cerebrovascular events. Performing a cranioplasty and thus reconstructing the skull after a DC poses a challenge to neurosurgeons, plastic reconstructive surgeons, and maxillofacial surgeons since the procedure often comprises very large skull defects, postoperative infections (due to foreign material implantation), subdural or epidural accumulations, seizures, postoperative hemorrhage, cerebrospinal fluid (CSF) leaks, and/or neurological deficits.[
Materials utilized for cranial reconstruction include bone, auto/allografts, distinct biomaterials, and even osteoinductive growth factors.[
Prefabrication of PMMA prostheses by hand has been used since the 1970s employing various procedures,[
The purposes of this paper are to describe a technique to fabricate PMMA prostheses by hand using original bone flaps, and at the same time describe the surgical outcomes of this procedure. We also intend to demonstrate that these prostheses are a relatively nonexpensive, cosmetically and functionally acceptable alternative to newer 3-D printers.
Between the years 2002 and 2013, a total of 26 patients underwent DC and subsequent cranioplasty with preformed PMMA prostheses made by hand. Patients in whom own bone flaps were not available were excluded. Patients’ records were thoroughly reviewed for data extraction. Patient age, sex, indication for initial DC, size of DC, interval time between DC and cranioplasty, duration of surgery, postoperative complications, follow up time and Glasgow Outcome Scale scores (GOSs) at the time of cranioplasty and at last follow-up visit were reviewed.
At the time of initial DC, the removed bone flaps were thoroughly irrigated with saline solution, cleaned from tissue debris and stored in a conventional refrigerator at the hospital laboratory. The custom PMMA prostheses were fabricated with the aid of a prosthodontist.
The bone flap was inspected and the burr holes filled with methylmethacrylate (MMA; Codman Cranioplastic, Type 1-Slow Set, Johnson and Johnson, Raynham, MA) in a power-to-liquid ratio of 2:1. Thin areas of the bony flap were augmented with MMA to increase thickness to 2-3 mm. The C-Silicone (Speedex Putty, Coltène/Whaledent, Altstatten, Switzerland) was put over the working table in a sufficient amount to cover the internal surface of the bony flap, and was then mixed with the Universal Activator (Speedex Universal Activator, Coltène/Whaledent, Altstatten, Switzerland) for 2 minutes. The internal surface of the bony flap was covered with petroleum jelly body lotion and placed over the mixture and an impression was made in 5 minutes (the C-Silicone should not surpass the lateral borders of the bony flap). The same process was repeated for the external surface of the bony flap [
Surgical technique for prosthesis placement
The PMMA prosthesis is sterilized with plasma prior to surgery. Under general anesthesia, the scalp is reopened and dissected from the dura. The defect's borders are freed from any adjacent tissue. The temporal muscle is dissected and freed from the skin flap. To reattach it, several small holes (3 mm) are made on the PMMA prosthesis, and fixed with Nylon sutures [
The Mann–Whitney U Test was used to compare median GOSs. The results were considered significant when the P value was < 0.05. Descriptive results are presented as the mean ± SD when applicable. All data were analyzed using the statistical analysis add-on for Microsoft Excel for Mac (Microsoft, 2011).
A total of 26 PMMA prostheses were fabricated and consequently a total of 26 cranioplasties were performed between the years 2002 and 2013 [
The median time between the initial DC and cranioplasty was 2.4 months, and during this time the prostheses were fabricated. Mean fabrication time for each prosthesis with this technique was 70 minutes, with a cost of US$800. Mean surgical time for prosthesis placement was 2.6 ± 0.6 hours. After a median follow-up time of 10.4 months, only two patients (7.6%) presented with cranioplasty-related complications: One epidural hematoma and one surgical infection. The first patient presented with the hematoma 2 days after surgery and required drainage; there was no need for prosthesis removal. The second patient presented with surgical infection in the form of an epidural collection 4 months after cranioplasty, which required debridement, lavage, and PMMA prosthesis removal. Two months later, the defect was reconstructed with a titanium mesh. Fortunately, both patients did well on follow-up visits. Although not a direct cranioplasty complication, another two patients (7.6%) presented with temporal muscle atrophy, which is a widely known complication, not only of DCs[
We measured the GOSs of patients at the time of cranioplasty and found a median score of 3. This score improved significantly after the cranioplasty and was found to be 4 at last follow-up (P = 0.008).
Patient satisfaction was assessed on follow-up visits. Out of the 26 patients, 24 (92.4%) felt comfortable with their aesthetic result, and did not inquire about a second operation for cosmetic improvement [
The cranioplasty technique is itself an art, and the persistence of neurosurgical procedures and trauma has nourished this expanding field. Early cranioplasties date back to 3000 BC,[
Autogenous bone has been historically preferred over alloplastic materials to reconstruct the cranium, due to allegedly better mechanical, biologic, and immunologic properties.[
When autogenous bone is not available, alloplastic materials are required. It is agreed that the ideal implant material should have the following characteristics: It must fit the cranial defect and achieve complete closure, be biocompatible, inert, nonthermal conducting, radio-transparent, nonmagnetic, lightweight, rigid, simple to shape, easily applicable, and inexpensive.[
PMMA has the advantages of being inert, radio-transparent, nonmagnetic, simple to shape, relatively inexpensive and with adequate mechanical properties.[
Prefabrication of PMMA implants can be done in two ways: By hand or with CAD/CAM techniques. Hand-fabrication is cheaper and less time-consuming than using 3-D computed tomography data from a patient and a 3-D printer to fabricate the prosthesis,[
The technique described in this paper uses C-silicone, which is a very easy-to-use and moldable impression material. Total manufacturing time was less than 2 hours, and the prosthesis had a cost of US$800. Three-dimensional printed prostheses, in contrast, take more than 8 hours to manufacture[
One of the most interesting benefits of cranioplasty is the improvement of neurologic function, which was proven on this paper with the significant improvement of the GOSs from 3 to 4 (P = 0.008) from the time of cranioplasty to last follow-up visit. The improvement of neurologic function is attributed to changes in brain physiology, particularly improvements on cerebral blood flow, cerebrovascular reserve capacity, and even cerebral glucose metabolism.[
Complications related to PMMA implants present in 9.2-23% of patients, with infection being the most common and feared with a rate of 9.2-19%, because most of the time it requires reoperation and implant removal.[
Timing of cranioplasty is still controversial, with evidence showing either a slight decrease in infection rate when performed early (within 3 months of craniectomy) or no particular advantage of early versus delayed surgical repair.[
The drawbacks of the method described in this paper are that (1) The original bone flap must be available (in the case of skull fractures, large bone fragments can still be joined together for prosthesis fabrication); (2) PMMA is not incorporated into and vascularized by contiguous bone (compared with autologous bone); and (3) It initially requires the aid of a posthodontist or technician, but the technique is easy to learn and can be carried out by neurosurgeons alone.
In most cases when a DC is done, the large bone flap is available and it is up to the neurosurgeon to decide what to do with it. In larger tertiary-care hospitals or first-world countries, bone flaps may be disposed of in favor of using CAD/CAM techniques for prosthesis fabrication. In other settings, the bone may be stored in a freezer for later use or used to fabricate an exact duplication with the technique described herein.
Hand-fabrication of PMMA prostheses is an excellent alternative to CAD/CAM prostheses when original bone flaps are available. The use of impression materials to duplicate the patient's bone flap is a cheap and safe way to reconstruct the cranium when time and cost are an important limitation. Infection, being the most feared complication of allograft implants, has a very low rate with the technique described in this paper. The benefits of cranioplasty on neurologic function are also validated. This technique has proven to be safe and has yielded excellent results.
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