What Is The Best Way To Fill In A Forehead Burr Hole and Built Up The Brow Ridges At The Same At The Same Time?
Q: Dr. Eppley, I want to get a forehead burr hole filled from a previous craniotomy that I had done. If you used hydroxyapatite (HA) material, would the HA be applied directly on the burr hole coming to direct contact with the dura? Would a mesh and screws be also used?
In addition, I want to get my brow ridges built up as they are a little flat for a guy. Do you favor having the the eyebrow implants custom-made or would you make them during the surgery? Can’t HA cause a necrosis of the surrounding tissue during curing? What would be the advantage of using HA for the eyebrow ridge implant over medpor, PEET, or any other existing material?
A: In answer to your questions:
1) When reconstructing/filling in burr holes, it is first necessary to dissect the soft tissue/scar from both around the hole and the bone edges to identify clearly the bony margins. This scar tissue directly lies over the dura so the material does not lie in direct contact to the dura. Even if it did, however, this would be of no consequence or concern. Because they can be some ballooning of the scar/dura into the burrhole, it can occasionally be necessary to push this tissue down so the bone edges of the hole are exposed. This is done with a small piece of titanium mesh (no screws) whose edges grip the bone to keep it in place.
2) I am not sure where you get the impression that any cranioplasty material, HA or even PMMA, can cause any tissue necrosis during curing. HA is a completely cold curing material that has no exothermic reaction during setting. Even PMMA, which does have an exothermic reaction during curing, is very mild and never exceeds 110 degrees F. The actual temperature at which tissue damage could occur is at 142 degrees F and above. Decades ago the original PMMAs had high cure temperatures but those versions no longer exist. This has never been an issues with HAs and, when they were introduced in the mid 1990s, that was one of their big advantages over PMMA, a neutral set temperature.
Brow ride augmentation can be done nearly 10 different ways, largely depending on what material is being used. In the right hands, they all can be effectively done from an aesthetic standpoint. What one has to look at then is the material’s biology, what is the process to place them and the cost to do it. The most biologically compatible material is HA because it is composed of the inorganic content of bone, calcium phosphate. This bone will bond directly to it and may even get a small amount of bone ingrowth. It is also the easiest to place and mold into a desired shape. All other typical synthetic facial implant materials, such as silicone, Medpor and Gore-tex, must be hand carved at the time of surgery from a block of material. While this is very doable, it adds to surgical time and the they must be screwed into place for stability. Materials such as HTR and PEET must be made beforehand off of a 3-D skeletal model. Between the costs of the model and the fabrication of the implants, this could easily add up to $10,000 in cost to the surgery. That would be acceptable if there was some overwhelming biologic advantage to the these materials, but there is not.
Dr. Barry Eppley