The brow bone area of the forehead is a frequent target for aesthetic change. Brow bone reduction is most commonly known undoubtably due to its higher profile association with facial feminization surgery. But brow bone reduction is also done for males with extremely strong brow bone prominences as well as for asymmetric brow bones due to differential amounts of sinus pneumatization between the two sides. Brow bone reduction techniques are done by either burring or bone flap removal/setback techniques.
Brow bone augmentation is performed less frequently than reduction and is dominated by males who desire a masculinizing change to the upper third of their face. Females with very flat foreheads may occasionally request it as part of an overall forehead augmentation as well. How to augment the brow bones is alloplastic in nature which fundamentally divides into bone cements and implant materials. While there are advantages and disadvantages to these approaches the custom brow bone implant is so much more effective than all other approaches that it is almost historic by comparison and has very limited uses today.
But whether it is brow bone reduction or augmentation, it is critical that the anatomy of this part of the forehead be understood, particularly as it relates to its topographic contours and shape. Study of many 3D CT scans permits great insights into its shape that plain x-rays or an external examination could never provide. The male brow bone is a good place to start since its features are more prominent and do differ from that of females. The brow bone is composed of two parts which can be artificially divided by a vertical line drawn up through the pupil externally or by a vertical line passing through the supraorbital nerve notch as seen on 3D CT scans. The raised/bulging brow bone located between these vertical lines is due to the underlying frontal sinus air cavity and only has a thin shell of overlying bone. This is why it can look just like the bone over the maxillary sinus below the eye which appears ‘moth-eaten’ which is a reflection of how thin the bone over the air space is.The brow bone that lies lateral to this line is solid frontal bone as the frontal sinus does not extend that far.
Because of the differing bony elements of the brow bone it has seven components along its course at the lower forehead between the two fronto-zygomatic sutures. These include the frontal sinus protrusions (#s 2 and 3), the glabellar hollow/concavity in the midline between them (#1), the paired solid lateral brow bones (#s 4 and 5) and the supra brow bone break where the brow bones blend into the forehead above it. (#6 and 7)
While female brow bones have the same components as men their overall prominences are less. The frontal sinus is less well pneumatized (developed) due to hormonal differences and this makes the degree of prominences less. (more flat)
While these anatomic considerations are important for both brow bone augmentation and reduction the complexity of the bone shape has its greatest relevance in brow bone implant designs. In male brow bone implants the four distinct mounds needs to be incorporated into the design. On the bone such an implant will make it look angry or that they are frowning, particularly when viewed by color thicknesss. This is the hallmark of the male brow bone implant design. This does not mean it will look angry when the soft tissue covers it but a slightly exaggerated anatomic design is needed for the desired masculinizing effect.
The same applies when it is a complete forehead implant that includes the br0w bones. With the complete forehead implant design consideration must be given to how pronounced the supra brow bone break will be and how much brow bone projection is needed beyond what the forehead projection above it is.
For females in which brow bone coverage is almost always part of an overall forehead augmentation, the brow bone augmentation part of the implant is smooth without any prominences. The thickest part of the implant is usually above the brow bones in an effort to create a rounder and less inclined forehead shape.
Dr. Barry Eppley