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Posts Tagged ‘hydroxyapatite cement’

Skull Augmentation in Young Children with Plagiocephaly

Thursday, November 12th, 2015

plagioccephalyPlagiocephaly is a term used for a broad collection of congenital skull deformities that involve a general twisting or rotation of the skull base. This is most commonly seen as flattening on one side of the back of the head with compensatory changes anteriorly to the forehead and face. When diagnosed early skull molding therapies with helmets can be very effective in lessening the head shape deformity. But if not treated within the first year of life, the success of cranial molding therapy decreases significantly.

Unlike more severe skull deformities like craniosynostosis, plagicephaly is not generally viewed as severe enough in many cases to warrant major intracranial surgery through bone removal and reshaping. Flat areas on the back of the head are viewed as ‘cosmetic’ with no medical indication for surgical intervention…as viewed from the typical craniofacial surgical perspective. Certainly it is hard if not impossible to justify a major operation with a long scalp scar and need for blood trasnfusions to correct a mild to moderate occipital skull shape problem in a young child.

It is common in my practice to correct a wide variety of skull shape issues in adult with ‘aesthetic craniofacial’ techniques. This essentially means two fundamental approaches that differ from traditional craniofacial surgery methods…a very limited scalp scar and correction of the deficient skull with onlay bone cement methods. This requires experience in working with a variety of alloplastic cranioplasty materials and doing so with limited incisional access. This has proven to be a very effective approach with good skull contour improvements.

hydroxyapatite cement skull contouring dr barry eppley indianapolisThere is no reason that such a limited incisional skull contouring procedure can not be safely and effectively applied to young children with plagiocephaly skull concerns. The key component to this approach is the type of contouring material (bone cement) that is used. A bone cement material like hydroxypatite cement, while synthetic, has a highly osteoconductive surface and allows bone to bond directly to it. (does not develop a scar interface like a truly synthetic material would) While never being resorbed and replaced by actual bone, it is extremely well tolerated and will allow any remaining skull growth to be unimpeded. (At three to four years of age, the skull has undergone over 70% of eventual skull size anyway) Thus the skull contouring effect achieved will be maintained as the child continues to grow.

Having done a small series of hydroxyapatite cement skull augmentations in children (under age 5) for flat spots on the back of the head, it is an effective procedure with a very quick recovery. Most scalp incisions have been less than 5 to 6 cms in length. It is a challenge to work with bone cements through such a small opening but years of experience with the material have helped tremendously.  For the very motivated parent(s), treatment of mild to moderate plagiocephaly can be vey safely done at a young age.

Dr. Barry Eppley

Indianapolis, Indiana

Case Study: Skull Reshaping for Occipital Plagiocephaly in a Child

Thursday, April 3rd, 2014

 

Background: Occipital plagiocephaly is a well known benign skull deformity that causes a rather classic flat spot on the back of the head. It is frequently present at birth due to the positioning of the neonate head in the womb. It can also be caused by positioning of the baby during sleep causing a constant pressure force on one side of the back of the head. Regardless of the cause, occipital plagiocephaly can be improved by positioning techniques early after birth or molding helmet therapy in the first year of life.

Flat back of the Head Dr Barry Eppley IndianapolisBut once occipital plagiocephaly persists beyond one year of age, there are no external methods that can create a significant correction. Cranial vault remodeling can be done but the extent of this surgery makes it only justified in the most severe cases. Otherwise, flat spots on the back of the head must be endured to perhaps be dealt with as an adult if its appearance is a concern.

Skull augmentations in adults are not infrequently done for a variety of shape issues from the forehead to the back of the head by onlay cranioplasty methods. Through scalp incisions of various lengths and locations, different bone cement materials can be applied and shaped to change the skull contours in the treated area. Most commonly, the bone cement material is PMMA (acrylic) due to its lower cost and easy shaping in tight spaces.

Case Study: This 4 year-old male child had a moderately flat right occiput. On examination it could be seen that he had many of the typical findings for occipital plagiocephaly with some contralateral skull flaring/widening and a more forward position on the flattened. The parents were concerned with his degree of skull deformity and wanted to see it improved before he was much older and potentially subject to peer criticism.

Mimix Hydroxyapatite Bone Cement Skull Augmentation Dr Barry Eppley IndianapolisHydroxyapatite Bone Cement Occipital Augmentation Dr Barry Eppley IndianapolisUnder general anesthesia in the prone position, an incision was made above the back of the head but just across the top with no temporal extensions. The entire skull bone on the back of the head was exposed between the ears. Using hydroxyapatite cement (Mimix bone cement), the entire right occiput was augmented with the material in a putty form and shaped to match the opposite site and allowed to set. Once firm the incision was closed with resorbable sutures. No drain was used.

Occipital Cranioplasty in Child Dr Barry Eppley IndianapolisOnlay cranioplasty in children is as straightforward as it is in adults. The one difference is that choice of cranioplasty material should be as biocompatible to the skull bone as possible which makes the obvious choice of an hydroxyapatite cement. At the bone cement interface, bone will bond directly to the material without any fibrous capsule between them. While the density of hydroxyapatite does not permit bone ingrowth or replacement, bone growth can be expected along the edges of the material and to some extent over the top of it as the child grows. The material will be carried outward as the skull grows through endocranial absorption and ectocranial deposition.

While the decision to undergo skull reshaping in children for a flat back of the head can be viewed as controversial by some, that is a personal decision for parents to make about the need for surgical improvement in their child. From a plastic surgery standpoint, the onlay cranioplasty procedure is safe and effective and has few drawbacks other than a fine line scar in the scalp to perform it.

Case Highlights:

1) Occipital plagiocephaly can be treated at any age by an onlay cranioplasty skull reshaping technique.

2) The cranioplasty material of choice in children are non-resorbable hydroxyapatite cements.

3) Hydroxyapatite cements are the most biocompatible cranioplasty material and will grow with the skull bone as it expands outward.

Dr. Barry Eppley

Indianapolis, Indiana

Case Study: Forehead Reconstruction with Hydroxyapatite Cement

Friday, September 28th, 2012

 

Background: Loss of the frontal or forehead bone can occur for a variety of reasons, usually from depressed fractures or loss of a craniotomy flap from infection. With removal of the protective bone cover, the brain and its dural covering sit directly up against the skin not only creating an obvious depression but pulsating with each heartbeat. Forehead reconstruction carries the highest aesthetic demands of any skull defect because it is the most visible in a non-hair bearing area and may involve the brow bone and brow ridge area.

There are almost a dozen methods of forehead skull reconstruction from split-thickness cranial bone grafts to computer-generated custom implant pieces. When skillfully done, any of these reconstructive methods will work satisfactorily. Their various advantages and disadvantages change based on the size of the forehead defect. The larger the bone defect becomes the more a synthetic approach becomes an appealing option.

One well established synthetic cranioplasty material for reconstructive use is hydroxyapatite. Consisting of the inorganic mineral content of natural bone, it is highly biocompatible although it does not get replaced by bone. It ends up creating a dense firm bone-like material that blends smoothly into the surrounding bone edges. It does not have the same strength as the normal double cortical layer skull bone but is strong enough to be an adequate skull substitute.

Besides the aesthetics of forehead skull defects, it is the only skull area which is contiguous with the air-filled frontal sinus cavity. This is a potential source of contamination and is a frequent source of forehead infections if a tissue layer is not created between it and the bone reconstruction material.

Case Study: This 13 year-old teen age boy was involved in a motor vehicle accident and sustained a severely depressed frontal forehead fracture and a large laceration down the center of his forehead. This required an urgent neurosurgical procedure with bone removal and repair of the dura. After three months of healing, he was left with a large depressed central forehead area (10 cm x 6 cm) that extended from the scalp down to the brows with a well healed vertical forehead scar. A 3-D CT scan shows the size of the defect and its involvement with the brow area and the frontal sinus.

Under general anesthesia, the forehead bony defect was accessed through his existing vertical scar from the scalp down to the area between the brows. The skin was lifting off of the dura and the surrounding bone edges. Near the brow area, the frontal sinus cavity was encountered as a 2cm x 2cm hole above the level of the dura.

The frontal sinus was clean and healthy with normal mucosal lining. A large pericranial tissue patch was sutured around all edges to create a thick tissue partition between the frontal sinus and the reconstruction site.

After the pericranial patch was placed, a floor was created for the reconstruction using titanium mesh. Thin 1mm titanium mesh was cut just larger than the bone defect and its edges were slipped under the defect to become a self-locking floor. This not only provided a containment method for the hydroxyapatite cement but keep the dural pulsations off of the hardening reconstruction.

Using a well known hydroxyapatite cement (Mimx, Biomet Microfixation, Jacksonville, FL), the activating liquid and calcium hydroxyapatite powder were mixed together into a putty consistency. This was then poured into the bone defect and molded into shape, recreating the lost brow bone area and the forehead above it.  The forehead skin was then closed and scalp scar removed prior to its closure in the hair area.

His surgery was done as an outpatient and he went home the same day. His head dressing was removed the next day and his sutures in the scalp removed ten days later. He had a smooth forehead result right with elimination of the forehead depression and the dural pulsations.

Case Highlights:

1) Reconstruction of the bony forehead can be done by a variety of techniques and hydroxyapatite is a well established cranioplasty material for full-thickness skull defects.

2) Forehead reconstruction which extends down into the brow area must take into account the frontal sinus and have a plan to keep it separate from any implanted material.

3) The properties of hydroxyapatite in a full-thickness skull defect needs reinforcement or a floor to add both strength and a containment method for the material.

Dr. Barry Eppley

Indianapolis, Indiana

Reconstruction of Skull Defects with Synthetic Materials

Monday, May 25th, 2009

Defects of the outer skull produces indentations and depressions in the scalp or forehead. Skull deformities can be caused by a variety of sources including craniotomy surgery, fractures, and muscle atrophy (if in the temporal region) While hair can cover many of these issues, some patients will seek reconstruction of these cosmetic defects.

Building back out the skull bone, also known as cranioplasty, has been done for over a hundred years. Many materials have been used to onlay onto or over the defect including natural and synthetic bone, ceramics, calcium phosphate cements, and metallic plates and meshes. Which one is best is really a function of the surgeon’s expertise and experience and not so much what type of material is used as they all can be made to work.

In most small to moderately-large cranial defects that are not full-thickness, I prefer hydroxyapatite cements (HAC) or PMMA (poly methylmethacrylate) Both are liquid and powder mixtures that are turned into a slurry which can be molded to all margins. HAC is a bit trickier to work with but in a young patient may be better in the long-run as it is does allow for some tissue ingrowth through its fissures and cracks. PMMA is easier to work with and is quite fracture-resistant. It is also much less expensive which can be a significant advantage if one is paying out of pocket. In either case, I always put some powdered antibiotics into the mixtures for a slow release after surgery.

In large full-thickness cranial defects, I have used computer-generated implants made of a porous material known as HTR. (hard tissue replacement) These are usually used in cases of loss of a craniotomy flap or for the immediate replacement of a skull bone tumor. The exactness of the computer imaging and modeling is quite impressive although most cases still require some minor modifications during surgery. The great benefit of HTR implants is that they allow for a lot of fibrovascular ingrowth which makes them resistant and/or treatable to infections should they develop. Bone ingrowth, while theoretically appealing, is usually of no practical significance due to the high fracture resistance of the material. When facing complex cranial defects, particularly of the forehead, cranial HTR implants have a long track history of clinical success.

Reconstruction of cranial defects is a highly successful procedure that can be done with a variety of materials. Synthetic bone substitute materials such as HAC and HTR produce very consistent results in experienced hands. These materials should be used with caution if there is predicted difficulty with scalp closure, if the patient has been irradiated or has a past history of osteoradionecrosis, or there has been an active or recent history of bone infection.

 Dr. Barry Eppley

Indianapolis, Indiana

Forehead Augmentation With Synthetic Materials

Wednesday, December 10th, 2008

Reshaping the forehead is an uncommon patient request. While the plastic surgery techniques to do so are well known and not new, the need to do forehead contouring is not. Most commonly, forehead reshaping is done on patients who had a congenital skull deformity (e.g., craniosynostosis) or a frontal skull deformity secondary to trauma or after a neurosurgery craniotomy procedure. The cosmetic reasons would be to soften prominent brow ridges or to smooth out some forehead irregularities.

The treatment of forehead irregularities can theoretically be done by either burring down bone or adding a synthetic material to it. In reality, burring down bone on the skull is a limited procedure and can never make as big a difference as one would think. The brow ridges can be burred down but the limiting factor is the underlying frontal sinus. If the overlying frontal sinus bone is thin, then very little bone can actually be taken. Above the brow ridges, burring down forehead bone is very effective for small raised areas that are easily identifiable but is less effective at reducing large surface areas of bone.

Filling in or adding to the forehead bone is a much easier and effective procedure. The real question in forehead augmentation is what material to use. Traditional PMMA (polymethylmethacrylate) has been around for a long time and has the advantages of a very low cost, high resistance to impact forces, and ease of intraoperative contouring. Its main disadvantage is that some patients over time can develop some low-grade reactions to it and it may get loose, become infected or the overlying forehead skin may thin, although these issues are fairly low risk. Newer ‘more natural’ materials such as hydroxyapatite cements (HA) have been available over the past 10 years. HA offers the advantage of being a more natural, less synthetic material as its structure more closely resembles that of bone. Its disadvantages are that it is considerably more expensive, has a low resistance to impact (easily shatters), and is a bit tricker for the plastic surgeon to use. The advantages and disadvantages for HA vs. PMMA must be considered and weighed on an individual case basis.

Regardless of the material used, synthetic forehead augmentation usually requires an open scalp incision which, because of its length, is a significant consideration in a cosmetic procedure. (particularly for men) Endoscopic or limited scalp incisions may be able to be used in small areas of augmentation in carefully selected cases.

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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