Q: Dr. Eppley, I want to have the flat spot on the back of my head built up. I understand that various materials can be used to do it but don’t know which one would be better. What are my options?
A: Bone cements in cranioplasty can be either polymethylmethacrylate (PMMA) or various calcium-containing materials. All of these materials are joint powders and liquids that are mixed in surgery to create a self-curing putty that offers enough set times to create the desired shape on the bone. The most ‘natural’ bone cement is that of the synthetic calcium compositions, of which the most common ones used are calcium phosphate-based also known as hydroxyapatites. (HA) They are natural to the bone because the inorganic mineral content of human bone is hydroxyapatite. Another calcium-containing bone cement is that of calcium carbonate, known commercially as Kryptonite. It offers superior biomechanical properties (less prone to fracture) than the calcium phosphate-based masterials but is no longer commercially available. Whether PMMA or HA is better for any cranioplasty is based on a variety of factors (cost, inlay vs onlay, size of incision) and not necessarily because one is more natural or more synthetic. There are different material properties for each type of bone cement and these must be considered also.
Dr. Barry Eppley