Background: Many areas of the face and the body can be augmented for aesthetic purposes. While the skull is not usually perceived as also be able to be enlarged, it can be done as well. The tightness of the overlying scalp is more restrictive than other body areas so there are limits as to how much skull augmentation can be done.
The implant materials used for aesthetic or onlay skull augmentation are either bone cements or custom made implants. Each can be effective but in larger surface area augmentations a custom implant becomes more effective with far less risk of contour irregularities or edge transition issues. The use of a custom skull implant becomes particularly advantageous when it become necessary to replace a medically or aesthetically compromised large bone cement cranioplasty.
Case Study: This 35 year-old Asian male had previously been through a large PMMA bone cement skull augmentation procedure that went from the brow bones back to the bottom of the occiput. It provided a good amount of the desired augmentation (a little strong in the forehead) and had no obvious palpable edges. But he did develop a chronic infection that had been controlled for some time with oral antibiotics. As a result it became necessary to have it replaced. A 3D CT scan shows the extent of the cranioplasty. It makes the bone cement look very irregular and not smooth which it actually was not, this is just imaging artefact.
A new large custom skull implant was designed using the outline of the indwelling PMMA bone cement. The forehead was reduced in thickness as the patient requested. The largest area of augmentation was in the occipital region of almost 25mms. Due its large size over a long convex surface, it was designed to be placed in two pieces.
Under general anesthesia and using his existing coronal incision, his PMMA bone cement cranioplasty was removed in three large pieces. It was rigidly fixed to the skull and no fluid or purulence was found. A slime layer was present on both its outer and inner surfaces consistent with a chronic infection. The bone and overlying underside of the scalp was thoroughly debrided and washed. The two-piece custom implant was reassembled on the patient’ skull and screwed in place with a perfect fit. The overlying scalp closure was tight but could still be competently closed in two layers.
When adequate scalp space exists from a prior implant, a large custom skull implant can be accommodated. This is relevant when the need to replace an existing onlay cranioplasty exists and a full coronal incision is present. This permits a lot of scalp mobility although pericranial releases may be needed due to the development of an implant capsular scar.
Highlights:
1) Large skull augmentations cover the forehead in front and go back to the occipital area on the back of the head.
2) The use of bone cements as a cranioplasty method over a large skull surface area is prone to irregularities and a non-smooth contour.
3) A custom skull implant is the best way to cover large skull areas and be a superior replacement for a prior alloplastic augmentation cranioplasty.
Dr. Barry Eppley
Indianapolis, Indiana