The forehead has a variety of shapes that do differ based on gender. Men will tend to have flatter fuller foreheads with more prominent brow bones (supraorbital ridges) while women’s foreheads will usually be softer, less full, and with flatter brow bones that tend to angle off into the temporal region. Whether it be by a congenital deformity (such as craniosynostosis), frontal tumor resection (craniotomy flap) or from prior contouring purposes (FFS, facial feminization surgery), there are rare instances when one desires to have a fuller or more prominent brow definition restored.
Brow bone augmentation (BBA) is one form of forehead reshaping that can be done. Using synthetic materials as a building material, the bone can be ‘thickened’ and recontoured to alter how the brow looks. Since the eyebrow and the upper part of the eyelid is affected by its underlying bony support, such changes can produce subtle to dramatic differences.
One of the key issues of brow bone augmentation is which material to use. Currently, hydroxyapatite (HA) and acrylic (PMMA) are the only two moldeable materials of choice. Your own bone is usually not a good option since you have to harvest it and how it survives as an onlay is unpredictable. Both HA and PMMA have their advocates but I have gotten good results with both. Either one can do the job. PMMA is much cheaper from a material cost standpoint and is very hard once it sets, being hard if not harder than natural bone. HA is much more expensive, a little harder to work with, and is more fragile to impact. But it is closer to the mineral of natural bone so it has greater compatibility and less risk of long-term body reaction concerns.
There is also the option of a synthetic implant carved out of silicone or polyethylene. (Medpor) This requires a greater degree of skill and time to get all the edges flat and flush with the surrounding bone. It is easy to see how an edge step-off can be felt through the skin unless it is done perfectly. Feathering edges and blending into the surrounding bone is much more assured with the moldable materials.
The other important consideration of BBA is access. For the most part, an open scalp approach provides the best vision and control of the shape. But this is understandably problematic for most men unless they have a pre-existing scalp scar to use. For most women, this is not a significant issue as a hairline (pretrichial) approach can be done and that scar can really be quite fine and unnoticeable. I know this from a lot of experience with pretrichial (hairline) browlift procedures done for cosmetic purposes.
A non-open scalp approach (endoscopic) can be used in select cases of forehead augmentation. When it is the central or more upper parts of the forehead that are being augmented, the endoscopic approach using PMMA as an injectable material can be done. PMMA can be injected and pushed around as a congealed putty and shaped by external molding through the forehead skin. HA is a quite different material and its handling properties do not permit anything but an open approach scalp approach. But working down at the brow area, which is a very low point for endoscopic visualization, is even difficult with PMMA. Therefore, I would advocate an open approach for any amount of brow bone build-up.