Should A Cranioplasty Material Be Placed Above Or Below The Periosteum?
Q: Dr. Eppley, regarding the skull augmentation will the bone cement be set beneath the periosteum. Could that involve any risk of “osteolysis”? Could the bone cement be put on the periosteum instead? Thanks!
A: Your question is an interesting one and is only relevant based on the type of cranioplasty material that may be used. When using any of the hydroxyapatite (HA) formulations, you definitely want to be under the periosteum for two good reasons. First, the material does bond directly to bone with no risk of osteolysis and you want to take advantage of this biologic benefit. Secondly, if HA materials do not bond to the bone they will ultimately be unstable and may likely shift position afterwards and develop fractures or fragmentation of the materials at their feather edges. When it comes to poly methylmethacrylate (PMMA) cranioplasty material, this can be placed on top of the periosteum and will set up and will likely not shift or fragment afterwards particularly if microscrew anchorage is used. PMMA materials, unlike HA, do have a known and low risk of settling into the bone a little bit and are what you refer to as ‘osteolysis’. But this is not a particularly progressive process and is self-limiting. Conversely, I have greater concerns for its effects on the overlying scalp and tissue thinning. Therefore I think it more important to provide as much barrier between the material and the overlying scalp tissues as possible and would recommend staying beneath the periosteum for this important long-term reason.
Dr. Barry Eppley