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Posts Tagged ‘skull implants’

Scalp Tissue Expansion in Large Skull Implants

Sunday, March 20th, 2016

 

In skull implant surgery, the limiting factor in terms of the amount of augmentation obtained is the stretch of the scalp. With the use of 3D CT scans and computer designing, any size and shape of skull implant can be made. But just because it can be made does not mean that it can be safely inserted or avoid long-term complications. The key is adequate scalp tissue to accommodate the size of the implant and not over stretch the scalp tissue over time.

The exact size and dimensions of a skull implant that the scalp tissues can tolerate will vary amongst different patients. There is no absolute thickness number in millimeters that is the maximum for any patient. But I use a general rule that any skull implant thicker than about 10 to 12mms may make the scalp closure tight or raise concerns about tissue thinning long term.

For those patients that would like larger amounts of skull augmentation, the concept of increasing the amount of scalp tissue to accommodate the implant must be done. This is achieved through the historic and well known use a scalp tissue expander. But unlike how scalp tissue expanders are used for more typical cases of scalp reconstruction, there are some differences when used as a first stage preparation for larger skull implants.

First Stage Scalp Tissue Expander for Large Skull Implant Dr Barry Eppley IndianapolisThe amount of scalp expansion for skull implants is more limited and only needs to be enough to look just slightly beyond the amount of skull height that the patient aesthetically wants. This is usually no more than 125cc to 150cc for most patients. I prefer a long rectangular shaped tissue expander as it can be inserted through a small scalp incision.

Scalp Incision for Scalp Tissue Expander Placement Dr Barry Eppley IndianapolisThe scalp incision to insert the tissue expander show lie along the future location of the longer incision needed for the second stage skull implant insertion. This is placed on the side of the head in the posterior temporal area and no hair is removed in making and closing the incision. The incision length needs to be no greater than 4 to 5 cms. This keeps the incision way from the location of the overlying scalp expansion.

Port Location for Scalp Tissue Expander Dr Barry Eppley IndianapolisPatients will do their own at home scalp tissue expander inflations. The port of the expander is placed on the deep temporalis fascia just above the ear. This location makes it easy for the patient to locate it and see it to insert the needle for the saline inflations.

Usually the needed scalp tissue expander inflations are completed in four to six weeks after the expander placement. Because the amount of scalp expansion is not great, its detection is very minimal in women who wear their hair long.

Dr. Barry Eppley

Indianapolis, Indiana

Case Study – Custom Parasagittal Skull Implants

Wednesday, August 26th, 2015

Background: The top of the skull has the best aesthetic shape when it is a smooth convex curve from one temporal line to the other. This shape can be altered and is influenced by the original sagittal suture line which runs down the middle of the skull between the two original anterior and posterior fontanelles. While it should be smooth and unraised sagittal crest deformities can occur which can be argued are very minor variants of the well known sagittal craniosynostosis condition.

A sagittal crest can develop which appears as a prominent bony ridge down the middle. This can make the bony area between the temporal lines at the side and the midline of the skull (parasagittal area) appear depressed or too shallow. It is also possible that the height of the midline of the skull is normal but that the bony problem is that the parasagittal region is underdeveloped. Either way the top of the head does not have a convex shape and appears irregular in contour.

To create a more convex shape to the top of the head, it is necessary to determine whether sagittal crest reduction needs to be done or parasagittal augmentation is more appropriate.  Computer imaging from the frontal view is very helpful in this regard although there are limitations to it based on the length and density of one’s hair.

Case Study: This 24 year old male wanted to improve the shape of the top of his head. He felt that he had two grooves on each side of the middle of the skull running from front to back. While they were not big or severe they were bothersome to him. He felt that the height of the middle of his skull was fine and it was the sides along it that were too deep.

Parasagittal Skull Implant Designs Dr Barry Eppley IndianapolisParasagittal Skull Implant Thicknesses Dr Barry Eppley IndianapolisUsing a 3D CT scan custom parasagittal skull implants were designed to fill in the grooves. They were long and slender and spanned the traverse from the midline to the temporal region on both sides. With the aid of computer design the parasagittal depressions were filled up just to the level of making the temporal lines curve upward to the midline and nothing more.

parasagittal skull implantsPerforated Skull Implants Dr Barry Eppley IndianapolisScrew Fixation of Parasagittal Skull Implants Dr Barry Eppley IndianapolisUnder general anesthesia two small (3 cm) incisions were made at the posterior end of the parasagittal region near the back of the head. Subperiosteal tunnels were made and the implants inserted. Once positioned they were secured with a single 1.5mm self-tapping titanium screw.

Parasagittal grooves or depressions can be augmented to help create a more convex head shape across the top. Given their small size in many cases and the need for perfectly smooth edges that lay flush to the surrounding skull bone, a custom computer-designed implant approach is needed. This also allows the skull implants to be inserted through the smallest possible scalp incisions with assurance that they will create the best possible contour result.

Highlights:

1) Parasagittal skull deficiencies can occur due to either a high sagittal crest, low parasagittal areas or both.

2) Correction of low parasagittal areas of the skull is done by augmnetation to bring them closer to the level of the sagittal crest.

3) Custom parasagittal skull implants are the most accurate and least invasive method to augment long slender skull deficiencies.

Dr. Barry Eppley

Indianapolis, Indiana

Small Sagittal Skull Implants

Sunday, April 26th, 2015

 

While the skull is often envisioned as a perfectly smooth oval shape, it often isn’t. Due to how the cranial sutures fuse and intervening bones form, the surface of the skull is often irregular. Such irregularities often occur along the suture lines due to their early activity during development and closure right after birth. They are frequent sites of  high spots, bumps and dips and indentations.

The sagittal suture is the longest of the cranial sutures due to its midline longitudinal course from the upper forehead to the top of the back of the head. Its midline position gives it a visible form in both the front and profile views. Any abnormalities along the fused suture line is most easily seen in the short haired or shaved headed male. One such sagittal deformity is a dip that appears between the front and back portions of the sagittal suture line. This is usually due to higher bone formation that occurs around the areas of the former front and back soft spots (fontanelles) as they initially fused together.

Sagittal Skull Implant Dr Barry Eppley IndianapolisCorrection of this sagittal skull dip can be done by filling in between the raised front and back skull areas. This can be done by using a linear shaped skull implant that sits in the dip. Such a small and unusually shaped skull implant can be made from various materials including silicone elastomer. They can be designed from measurements, an elastomer moulage or even from a 3D CT scan of the patient.

sagittal skull implant indianapolis indianaThis small linear implant can be placed under local or IV sedation through a small 2.5 cm scalp incision. It is inserted after making a very precise midline pocket that does not extend beyond the length of the implant. Small perfusion holes are placed in the implant to allow for tissue ingrowth and long-term stabilization.

Skull augmentation can be done for a diverse group of skull defects even those as small as the sagittal dip.

Dr. Barry Eppley

Indianapolis, Indiana

Technical Strategies – Perfusion Holes in Skull Implants

Sunday, March 15th, 2015

Aesthetic cranioplasty often involves the coverage of large skull areas with alloplastic material. Whether it be PMMA or hydroxyapatite cements or with today’s custom 3D generated silicone implants, a fairly large amount of material can serve as a solid interface between the overlying scalp and the underlying cranial bone. As the scalp has an excellent blood supply through major arterial pedicles, the placement of such skull implants do not pose any vascular compromise to the scalp tissues in general or to hair growth in particular.

But there are risks to consider in the use of larger skull implants such as scalp tissue adherence and the development of seromas (fluid collections) after surgery. It is easy to see how these might occur since the scalp normally sticks back down to bone and seals its lymphatic channels by such healing. Any implant material, however, creates a surrounding capsule to which the scalp sticks but the capsule itself does not adhere to the material as firmly as natural scalp tissue sticks to bone. The capsule itself can also be a source of chronic fluid egress particularly in secondary surgery where an established capsule exists.

Cranioplasty Pefusion Holes Dr Barry Eppley IndianapolisWhile the development of these skull implant issues are rare in my experience, there is a simple intraoperative manuever to help their prevention. The placement of many small holes through the material, known as perfusion holes, can help re-establish a fibrovascular connection between the scalp and the underlying skull bone. The more holes that are placed the more small connections that are made. In solid PMMA bone cement 2mm holes are made with a handpiece and burr. It is only necessary to go through the material and not into the bone. But there is no harm in doing so if the outer cortex of the bone is penetrated.

Skull Implant Perfusion Holes Dr Barry Eppley IndianapolisIn custom silicone skull implants these perfusion holes are made with a 2mm or 3mm skin punch. This is easy and quick to do. How many perfusion holes to make is not precisely known but more is probably better than less.

The placement of perfusion holes in aesthetic skull implants, in addition to recreating a vascular connection, also serves to have a quilting effect. With the tissue ingrowth through the holes, a small soft tissue ‘anchor’ is created. This in effect takes a large subcapsular space around the implant and turns it into many smaller compartments. This serves not only to anchor the overlying scalp to the implant but also can have a seroma prevention effect.

Dr. Barry Eppley

Indianapolis, Indiana


Dr. Barry EppleyDr. Barry Eppley

Dr. Barry Eppley is an extensively trained plastic and cosmetic surgeon with more than 20 years of surgical experience. He is both a licensed physician and dentist as well as double board-certified in both Plastic and Reconstructive Surgery and Oral and Maxillofacial Surgery. This training allows him to perform the most complex surgical procedures from cosmetic changes to the face and body to craniofacial surgery. Dr. Eppley has made extensive contributions to plastic surgery starting with the development of several advanced surgical techniques. He is a revered author, lecturer and educator in the field of plastic and cosmetic surgery.

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