Reconstruction of large cranial defects with poly-methyl-methacrylate (PMMA) using a rapid prototyping model and a new technique for intraoperative implant modeling.
BACKGROUND
Reconstruction of large cranial defects after craniectomy can be accomplished by free-hand poly-methyl-methacrylate (PMMA) or industrially manufactured implants. The free-hand technique often does not achieve satisfactory cosmetic results but is inexpensive. In an attempt to combine the accuracy of specifically manufactured implants with low cost of PMMA.


METHODS
Forty-six consecutive patients with large skull defects after trauma or infection were retrospectively analyzed. The defects were reconstructed using computer-aided design/computer-aided manufacturing (CAD/CAM) techniques. The computer file was imported into a rapid prototyping (RP) machine to produce an acrylonitrile-butadiene-styrene model (ABS) of the patient's bony head. The gas-sterilized model was used as a template for the intraoperative modeling of the PMMA cranioplasty. Thus, not the PMMA implant was generated by CAD/CAM technique but the model of the patients head to easily form a well-fitting implant. Cosmetic outcome was rated on a six-tiered scale by the patients after a minimum follow-up of three months.


RESULTS
The mean size of the defect was 74.36cm2. The implants fitted well in all patients. Seven patients had a postoperative complication and underwent reoperation. Mean follow-up period was 41 months (range 2-91 months). Results were excellent in 42, good in three and not satisfactory in one patient. Costs per implant were approximately 550 Euros.


CONCLUSIONS
PMMA implants fabricated in-house by direct molding using a bio-model of the patients bony head are easily produced, fit properly and are inexpensive compared to cranial implants fabricated with other RP or milling techniques.
Clinical Department of Neurosurgery, Innsbruck Medical University, Innsbruck, Austria. Electronic address: claudia.unterhofer@uki.at.
Claudia
C
Unterhofer
Clinical Department of Neurosurgery, Innsbruck Medical University, Innsbruck, Austria. Electronic address: christoph.wipplinger@tirol-kliniken.at.
Christoph
C
Wipplinger
Clinical Department of Radiology, Innsbruck Medical University, Innsbruck, Austria. Electronic address: michael.verius@tirol-kliniken.at.
Michael
M
Verius
Clinical Department of Radiology, Innsbruck Medical University, Innsbruck, Austria. Electronic address: wolfgang.recheis@tirol-kliniken.at.
Wolfgang
W
Recheis
Clinical Department of Neurosurgery, Innsbruck Medical University, Innsbruck, Austria. Electronic address: claudius.thome@tirol-kliniken.at.
Claudius
C
Thomé
Clinical Department of Neurosurgery, Innsbruck Medical University, Innsbruck, Austria. Electronic address: martin.ortler@tirol-kliniken.at.
Martin
M
Ortler
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D017076:Computer-Aided Design; D003399:Craniotomy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D019904:Polymethyl Methacrylate; D011183:Postoperative Complications / Q000209:etiology / Q000601:surgery; D019736:Prostheses and Implants; D011474:Prosthesis Design; D019651:Plastic Surgery Procedures / Q000379:methods*; D012086:Reoperation; D055815:Young Adult
D019904:Polymethyl Methacrylate
Cranioplasty; Poly-methyl-methacrylate (PMMA); Rapid prototyping; Stereolithography