Polymethylmethacrylate (PMMA) is presently the alloplastic material of choice for cranioplasties. It provides adequate neuroprotection despite a propensity for infection and extrusion. Medpor (porous polyethylene) is an alternate choice. It offers many advantages over PMMA but its strength characteristics are poorly defined.

In this pilot study, we evaluated the neuroprotective properties of PMMA, Medpor, and autologous bone following impact testing. Three groups of New Zealand white rabbits (PMMA, Medpor, and autologous bone) underwent a cranioplasty with titanium miniplate fixation. A sham group had no cranioplasty. Eight weeks later, an impact was delivered to center of each cranioplasty. A gross and histologic evaluation followed.

Both Medpor and PMMA were stronger than bone flap. Brain injury patterns were consistent regardless of the cranioplasty material or force of impact. Lack of fracture/dislodgement generally resulted in no obvious brain injury. Cranioplasty disruption always resulted in brain injury.

An ideal alloplast should be at least as strong as native bone flap. Based upon this pilot study the Medpor cranioplasty provides sufficient neuroprotection, the degree of which consistently surpasses native bone. In light of its advantages over other materials, porous polyethylene should be considered as a first line alloplastic material in the cranioplasty setting.