Top Articles

Aesthetic augmentation of the skull can be done on any of its five surfaces using a custom implant approach. Based on a 3D skull CT scan virtually any implant can be designed within the limits of how much the scalp can stretch to accommodate it. While the design possibilities are considerable there are no established guidelines to do so based on the relative short period of time the technology has been available for patient use. There is no transferable knowledge from 3D reconstructive skull implants as designing an implant to fill a cranial defect is not remotely the same as how to aesthetically enhance an intact skull surface.

Having done many aesthetic skull implants there are some basic design considerations that are important for a pleasing and natural looking result. The best way to lilustrate these concepts is to look at custom skull implant designs that didn’t work out well that needed to be replaced. (patients which came to me with skull implants made from other surgeons seeking replacements)

One of the over riding principles of custom skull implant design is that they must cover a much broader surface of the skull that one would initially think. The skull is essentially composed of convex surfaces of which each side blends into at least two or three of the other surfaces. In other words the skull shape is very connected and the base diameter of the implant must reflect this understanding of how the skull is shaped. 

Rarely should a skull implant design involve just one surface. If it does it will end up looking like an unnatural prominence on the skull like a small bowl or hat. Look at this female crown of the skull implant design which failed to incorporate this basic concept. The first thing that jumps out about it is that it is too small. Or to put it dimensionally the projection of the implant is excessive for its base diameter. This can be seen in every angle in which it is viewed. Broader surface area coverage is needed so that it appears as if it is merely an addition to the natural shape of the skull. 

In essence the more projection a skull implant has the more surface area it needs to cover. Looks at this much better design as its replacement. The maximum projection of the skull implant is 25% more but its surface area is doubled and has a much more natural shape to it as it fits over the skull.

Another key element in custom skull implant design is edging. There should be a smooth transition between the implant and the bone. All around the perimeter of the implant it should have a designed feather edge. Despite the thickness of the scalp the eventual shrink wrap soft tissue healing effect around the implant will make even a 1mm edge palpable and clearly visible in the shaved head patient.

The proper skull implant edge should be maximally tapered around its entire footprint. Sometimes in the manufacture of a skull implant a designed feather edge may still have a bit of blunt edge to it as part of the fabrication process. This must be checked for carefully prior to placement and, if seen, shaved down with a scalpel into a feather edge.

Another common error with custom skull implants is in how to manage them if their volumetric effect is inadequate. What you don’t want to do is to try and add some other material on top of them for an added volume effect. It is one thing to try and fill in a small contour issue but when a considerable size change is needed, placing a material on top of a skull implant has a high propensity to create an undesired shape effect. Thick pieces of ePTFE (Goretex) may seem an easy method to ‘top off’ a skull implant, and may even look adequate during surgery, but will inevitably create an undesired contour/shape. The assured method of achieving a larger skull augmentation effect that is smooth is to make a new custom skull implant that has the new shape features designed into it.

Dr. Barry Eppley

Indianapolis, Indiana

Top Articles