Page 86 - Clinical relevance of current materials for cranial implants

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Chapter 4
ABSTRACT
Background: In 2001, a 27-year-old man was diagnosed with a meningioma with skull bone involvement. A craniectomy was performed and a CMW-3 poly(methyl methacrylate) cranioplasty was manually manufactured to reconstruct the remaining cranial defect. In 2016, he complained about progressive neurologic impairment. A CT- scan revealed that the cranioplasty had fractured into four dislocated pieces. Removal was indicated and during the same operation a poly(ether ether ketone) patient- specific implant was inserted.
Materials and Methods: The fractured cranioplasty was compared to freshly prepared CMW-3 specimens to determine whether the material properties had changed during 15 years in vivo. Gel permeation chromatography, micro-computed tomography, and flexural strength tests were performed. The fracture itself was analyzed using finite element analysis.
Results: The polydispersity index and molecular weight were not significantly different for the fractured cranioplasty and CMW-3. The fractured cranioplasty contained a total porosity of 10.7%, CMW-3 cured at atmospheric pressure 4.1%, and 0.06% when it is cured at 2.2 bar. The flexural strength of the CMW-3 cured at 2.2 bar was significantly higher than both the fractured cranioplasty and CMW-3 cured at atmospheric pressure. Finite element analysis showed stress of 12.2 MPa under a load of 100 N on a weak spot.
Conclusion: This ex vivo study shows that CMW-3 after 15 years in vivo was not influenced in molecular weight or flexural strength. However, the design of the implant and the handling of the poly(methyl methacrylate) seem important factors to improve mechanical properties of cranial reconstructions.