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Posts Tagged ‘injectable cranioplasty’

Case Study – Funnel Insertion Technique for Injectable Occipital Cranioplasty

Monday, July 13th, 2015

 

Background: Flat spots on the back of the head or one-sided occipital flatness is not rare. While the back of the head is typically round, it is prone to numerous indentations and irregularities from in utero and neonatal influences. Since the back of the head is exposed to greater eternal pressures than the rest of the head combined, occipital deformations such as flat spots are not uncommon.

Correction of occipital defects or indentations can be done by a variety of bone augmentation techniques. The key differences are in what material is used and how it us introduced. Having performed many skull augmentations over the years there is no question that the single best method is a custom skull implant placed through a low occipital incision. But there still is a role in the patient for other forms of skull augmentation, particularly in unilateral occipital plagiocephaly. (flatness on one side)

Case Study: This 42 year-old male had always been bothered by a flat area on the back of his head. This had been there since he was a child. His mother said it happened because he laid on that side of his head since he was born and always turned back to it. It bothered him to the point that he would always wear a hat to hide it.

Minimal Incision Occipital Cranioplasty Dr Barry Eppley IndianapolisFunnel Insertion Cranioplasty Dr Barry Eppley IndianapolisUnder general anesthesia in the prone position, a 4 cm horizontal incision was made near the area of occipital flatness. Wide subperiosteal dissection was done to develop a pocket into and around the area of skull flatness. Using a funnel insertion device, 60 grams of PMMA was introduced through the incision into the subperiosteal pocket. The incision was temporarily stapled closed and the material in its putty form was shaped externally until it set into a hardened state.  The incision was then unstapled and all edges checked for smoothness. Then the incision was closed with dissolveable sutures.

Funnerl Insertion Cranioplasty result back view Dr Barry Eppley IndianapolisFunnel Insertion Cranioplasty result oblique view Dr Barry Eppley IndianapolisHis results showed a much improved shape of the back of the head that was more symmetric. There is no truly injectable cranioplasty or skull augmentation method in the truest sense of the injectable concept. (through a small needle with no incision) But PMMA cranioplasty material can be ‘injected’ (introduced) through a small incision and shaped by external manual molding. The funnel device is exactly that used for the insertion of implants in breast augmentation. Identical to a confectioner’s funnel for icing, PMMA bone cement can be used to aid into scalp pockets developed by subperiosteal instrument manipulation.

Highlights:

1) Smaller back of the head corrections for flat spots can be done by a near injectable bone cement technique. (injectable occipital cranioplasty)

2) This type of injectable cranioplasty requires a small incision and the bone cement is inserted through a funnel apparatus. This should not be confuse with a purely injection technique like that used for facial soft tissue fillers.

3) An injectable occipital cranioplasty requires shaping of the material as it sets from the outside through scalp molding.

Dr. Barry Eppley

Indianapolis, Indiana

Kryptonite Bone Cement – A Potential Injectable Cranioplasty Method

Monday, July 26th, 2010

Cranioplasty is done for making contouring changes to the cranial vault, which is defined as the skull, forehead and brow bones. Common causes for the need for cranioplasty are congenital deformities (after primary reconstruction), neurosurgical bone flaps, and traumatic injuries. When done for these reasons an open approach is always used as there is usually a pre-existing scalp scar/incision from a prior procedure. This makes it very easy to apply the traditional synthetic cranioplasty materials such as PMMA (acrylic) and HA. (hydroxyapatite)

 

However, some skull shape problems may be relatively small or may not be associated with any pre-existing incision for access. When balancing the trade-off of a new scalp scar versus keeping the existing skull concern, many patients (particularly men) would consider the scar as more undesireable. Cranioplasty would be more appealing in this circumstance if the cranioplasty material would  be able to be delivered from small and remote incisions. In essence, a cranioplasty material that could be delivered by an injection process.

 

The current craniplasty materials are far from ideal to be delivered through any form of remote access. PMMA, polymethylmethacrylate, is an initial liquid which can be delivered through a tube but it is very runny on delivery and sets up with a very high heat from an exothermic reaction. The numerous forms of hydroxyapatite (e.g., Mimx) create an initial viscous slurry which has no material flow at all. This makes it not only undeliverable by injection but its sensitivity to fluids and its easy fragmentation on setting make external digital molding unpredictable.

 

Kryptonite, the newest FDA-approved cranioplasty material offers some real promise as an injectable skull-shaping technique. It is a bone cement that is created through the combination of a calcium carbonate powder and two fatty acid liquid derivatives from castor oil. When combined together this makes a final hardened material that is porous and adhesive with bone-like properties. While this is as favorable to bone as any of the other cranioplasty materials, its physical features in the set-up process make it potentially useful to be delivered by an injection method.

 

Once the three ingredients are mixed, a very flowable liquid is created. During the intial polymerization process (up to 4 minutes), the material can be loaded into a syringe. Once in the syringe, it remains in a thick but flowable liquid phase up to 8 minutes are mixing. This provides the opportunity for delivery by injection. Once it passes the 8 minute time period, it enters a sticky taffy phase where it becomes very adhesive and is no longer injectable. A moldable phase will exist then up to 25 minutes in which further shaping can be done.

 

To pass the injectable cranioplasty test, it first must have enough flow to be delivered through a small enough tube that has sufficient length. A true injection method  is delivered percutaneously through a needle that is no larger than an 18 gauge. But that is not the type of injection to which I refer when being used for cranioplasty. Because instruments must be used to develop the subperiosteal pocket, either through an endoscopic or blind technique, one or two small remote incisions (less than 1 inch) would be used. Therefore the internal diameter of the injection method can be larger. But how large does it need to be? (or how small can be that it still works) In bench top testing, I have determined that it flows very nicely through an internal diameter of 2.7mms. (8 French catheter) This makes it possible to use long catheters for remote access. Some material will be lost in the tube during delivery which is 1cc per 13cm of length at 2.7mms diameter. Most injectable cranioplasties will not need more than 5 or 6cms of tube length for delivery. The indwelling .5cc of material can be pushed through with a saline fluid bolus behind it.

 

The other injectable consideration is can the material be effectively molded by external manipulation. Is it able to be pushed around and molded into fine edges without fracture or separation of the material? In testing on a pig’s head (from the butcher), Kryptonite was injected and externally molded to the back of the skull from an anterior incision. On dissection after setting, it was adherent to the bone, did not stick to the overlying soft tissue and had nicely contoured edges. Its sticky taffy phase which is between 5 and 15 minutes after mixing gives it a texture which really molds and shapes well.

 

Kryptonite bone cement appears to offer physical properties that would make it the first truly injectable cranioplasty material. Its use in this manner is for partial-thickness contour deformities of the skull and forehead.       

  

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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