The use of a scalp tissue expander is a critical first step in the large skull implant augmentation patient. Since the scalp is a tightly adherent soft tissue envelope that surrounds all five sides of the skull it has a limited ability to stretch to accommodate an expanded cranial contour using an implant underneath it. While scalp stretch is highly variable amongst patients there are multiple external indicators that can indicate how much to little it can be stretched. (skin pigment, hair type) But when it is determined that a first stage scalp stretch is needed a scalp expander device is used. While much of its use is done technically the same as in reconstructive surgery there are some differences in how it is applied in aesthetic skull augmentation surgery.
To review these scalp expander concepts for this application let’s review incision location, then typeof expander used, the rate and end fill of the device as well as its subsequent removal at the time of implant replacement.
The greatest volume in large skull implants is often centered more towards the back of the head. Thus scalp expanders are placed with the patients under general anesthesia in the prone position. No hair is shaved or removed for the procedure, it is parted along the horizontal line of scalp incision which is typically at or slightly above the nuchal ridge of the occipital bone. In longer hair it is parted into twi ponytails laid out above and below the incision line.
The scalp incision is made between the hair, paralleling the exit of the hair shafts from the scalp. This is almost always at a severe angle downward so the skin incision is quite beveled to avoid injuring hair bulbs. Its length is quite limited as scalp expanders are essentially deflated balloons and can pass easily through quite small incisions. Plus you want to make the incision small in length since it is close to but not over onto the soon to be expanded scalp area. It is always an irregular non-non-straight line. Through this incision long dissecting instruments are used to elevate (release) the scalp from the bone to form the pocket.
The scalp expander chosen is always round, typically14cms in diameter with a maximum fill of 550ccs. (although the needed fill volume needed is half that amount) It is a remote fill port as a tube that extends from the base implant. It becomes very obvious that the diameter of the expander is at least 3x bigger than the scalp incision used to place it.
In placing the expander it is rolled into a burrito shape which pass easily through the much smaller incision. Once the rolled expander is fully inside the scalp incision it is digitally unrolled so that it lays completely flat. The remote port will be sticking out which is then passed to a location under the scalp usually above the right ear for easy patient access after surgery for the inflations. A small amount of implant fill (10 to 20ccs) is done through the port prior to closure.
The scalp incision is closed in two layers with resorbable suture. No drain is use. The hair is combed back into a single ponytail and a light head dressing is applied which is removed the following day. One can shower the next day and wash their hair 72 hours after the surgery.
Adding volume to the expander is not started until 7 to 10 days after the surgery.The fluid fill regimen is 10cc every 2 to 3 days until the expander reaches at least that of the volume of the designed custom skull implant. As most larger custom skull implants are 200cc+ volume, the end goal is a 250cc fill for every patient. It is easy to see that it would take a minimum of two and a half months to complete this amount of expander fill which is why the second stage implant replacement surgery is scheduled 3 months after the placement of the tissue expander.
Having the tissue expander in and doing the injection fills has little discomfort. In the beginning and until about 2/3s of the way through the process the expander replicates to some degree that of what the implant will do as seen in a female with good hair coverage. As the expander gets more fill it assumes it natural shape (round) which is not the shape of the eventual skull augmentation. But most patients like its appearance anyway.
Because the full volume (250ccs) is way under the maximal fill volume of the expander (550cc) it will eventually feel a bit like a water bed on the head. You will feel the fluid moving back and forth, a strange but not uncomfortable experience. Nonetheless most patients are anxious and happy to tradeoff the expander for the firm bone-like feel of the custom skull implant.
Dr. Barry Eppley
World-Renowned Plastic Surgeon