Background: The shape of the head can be quite variable amongst different people. While often perceived as a smooth oblong shape, some people are not as blessed with such a smooth and symmetric skull. The skull can have a large number of asymmetries and deficiencies that may be of concern to the patient but unperceived by others due to coverage by hair.
One skull dimension is that of width. The width of the skull is composed of the temporal, parietal and upper forehead areas which is composed of a combination of bone and muscle. The width of the head can affect its appearance in short hair and can even affect how tight or loose hats and other head wear feel. While there is no exact number for ideal head circumference, the more practical issue is how it looks and feels.
Changing the width of the skull is often perceived as not being possible. But with today’s 3D implant design technology a wide variety of skull augmentation possibilities exist.
Case Study: This 65 year old male had been bothered his entire life by a head shape concern. He had trouble wearing hats and he had a noticeable asymmetry of his forehead. Since his hairline had receded a bit the forehead asymmetry became more apparent. The sides of his head were too narrow at the junction of the sides and top of the skull along the temporal lines. This caused a backward slope to his forehead which was most severe on his left side. Using a 3D CT scan, bilateral custom skull implants were designed to add volume and correct the asymmetry. It was very important that the front edge of the skull implants had a very feather edge so there was not a visible implant transition.
Under general anesthesia he has his custom skull implants inserted through 5 cm long incision at their back end. The implants had perfusion holes placed in them and were inserted in a rolled fashion. Once inserted they were unrolled, positioned and secured with a single 1.5mm microscrew per side.
Widening of the upper sides of the head can be successfully done through the use of custom skull implants. The implants will sit partially on bone and partially on the temporalis muscle fascia. They must be designed to have very thin edges all the way around the implant. With thicknesses of even 7mm, a total upper head width change of 15mms can make a very noticeable change.
1) Narrow head widths can make wearing hats difficult and can cause forehead asymmetry.
2) Paired custom skull implants can add width at the upper temporal and sides of the top of the head.
The fabrication of custom skull implants offers a major advance in the treatment of many aesthetic skull deformities. Historically skull augmentation had to be done using a long and complete coronal scalp incision and resultant scar for access and intraoperatively shaped bone cement materials. But today’s custom skull implants allow for the shaping of the implant to be done beforehand and the surgical incision needed to place it less in length.
But whether the surgical incision is small or long, the need to precisely place the implant remains the same. While custom skull implants have an exact fit due to their design, the surface of the skull most of the time is fairly convex and smooth. So even a custom skull implant can slide around and its exact fit may be uncertain.
One method to lessen the risk of a custom skull implant is to have a marking method placed into it. I have found that a simple vertical and horizontal line etched into the implant at its most central location helps provide orientation. The vertical or sagittal line makes sure that it’s anteroposterior placement is correct. The horizontal or coronal lines provides another method to check on the implant’s orientation. Both the horizontal and vertical line together, like a compass, help get the implant placed correctly as it slides around on the skull’s surface.
Once the custom skull implant is satisfactorily placed, it is secured with two small self-tapping 1.5mm titanium screws. They are placed on each side of the implant to prevent rotation. While I always place perfusion holes through any skull implants, which ultimately provides solid implant fixation, that is a process that takes weeks. The screws maintain implant position until then.
Even custom skull implants can create uncertainty as to their exact placement due to their being a long curved shaped implant on a smooth surface. Preoperative etched markings on the implant provide a simple but effective method of replicating on the patient the preoperatively designed skull implant placement.
Background: The shape of the skull can be almost as variable as each individual in many ways. But the one similar characteristic is that most skulls do have a smooth surface from the forehead to the back across the top. This is seen in many plain skull model examples where a smooth surface is usually evident.
But despite the depiction that a skull has a smooth surface, it does not always occur. For a variety of developmental reasons drive by sagittal suture and anterior and posterior fontanelle closure, the skull may develop a variety of surface irregularities. While across the top of the top of the skull the most common irregularity is a sagittal crest or ridge, generalized lumps and bumps may appear. The skull is otherwise of normal thickness but it just isn’t smooth.
While there are undoubtably many people who do not have a perfectly smooth skull to the touch, the presence of hair provides a visual camouflage of it and makes it tolerable. But in the male who shaves his head or lacks hair coverage, the skull irregularities can be quite visible and aesthetically distressing.
Case Study: This 35 year-old male had gone from long time usage of a hair prosthesis to that of a shaved head look. In so doing he was now aware and very conscious of how the surface of his head looked. He described it as being uneven, irregular and with high spots throughout. A 3D CT scan conformed that this was due to the bony shape of the skull. His goal was to have a smooth more rounded head shape across the top. This was designed to be accomplished by making a thin skull cap implant to cover the entire top from front to back staying along the temporal lines at the sides.
Under general anesthesia, a curved posterior scalp incision was made that was less long (wide) than the implant. Subperiosteal undermining was done over the entire scalp where the implant was to be located. The implant was inserted through the incision in a partially folded fashion and positioned. Prior to placement multiple perfusion holes were made through the implant. After placement absolute stability was assured with two small titanium screws.
A skull cap implant is a slightly different skull augmentation implant in that it is designed to create a smoother skull but not necessarily a larger or more augmented one. Because it is a thin implant (in this case 6mm maximal projection at highest point) it can be inserted through a relatively small scalp incision. Because it is placed partially folded it is critical that one makes sure that the edges of the implant are laying completely flat prior to closure. Thin implant edges can easily remain folded and are hard to detect by feel and impossible to see through a limited scalp incision.
1) The normally smooth surface of the skull can in some people be very lumpy which can be visible in the bald or shaved head male.
2) A thin custom made skull implant placed over the lumpy part of the skull can create a smoother scalp surface and feel.
3) A thin custom made skull cap implant can be placed through a relatively small scalp incision.
The use of 3D CT scanning and sophisticated imaging manipulation software has now made it possible to design specific implants for the face and skull for aesthetic augmentation/contouring and reconstructive purposes. This helps fill a growing need for patients who aesthetic and reconstructive requirements exceed what standard off-the-shelf implants can provide. The creation of these custom implants is possible because of a collaborative relationship between Implantech, the largest US manufacturer of facial implants located in California, and Medical Modeling a high tech engineering firm located in Colorado.
While the surgeion helps determine a patient’s need for custom implants and surgically places them, their design and fabrication occurs as a result of a working relationship between the doctor, Implantech and Medical Modeling. It is important that the patient understands how this relationship works as well as that of the implant design process. Having done many custom facial and skull implants over the past several years, many questions and issues has arisen in this design and fabrication process. Based on these experiences and knowledge, I have created a list of the most common issues that are important for patients to understand before they begin the custom implant process.
THE FINAL DESIGN OF THE CUSTOM IMPLANT IS ONLY AS GOOD AS THE CT SCAN FROM WHICH IT IS MADE. A very specifically taken 3D CT scan is first required. These are high resolution CT scan slices (0.1mm) that does not require IV contrast to be done. The doctor will usually order the scan at a facility of your choice and provide them with the protocol so that is it done properly. In some cases patients may already have a 3D CT scan in which case it will be verified with Medical Modeling that it is of adequate quality.
A CUSTOM IMPLANT’S DESIGN IS AS MUCH ART AS IT IS SCIENCE. While the computer software and the engineer that drives it can make any design, it has no innate knowledge as to what it’s aesthetic result will be or how it will look on the patient. Computer software does a terrific job of optimizing the implant’s fit to the bone, making the size and shape of the implant that is desired and ensuring optimal symmetry between two sides of the face or skull. This is a bone-based software that as of yet can not calculate the influence of the overlying soft tissue changes that the implant’s design will create. Thus while the custom implant is computer designed there is no guarantee that it will create the patient’s desired aesthetic result.
CUSTOM IMPLANTS CAN BE MADE WITH SYNTHETIC IMPLANTS/METAL HARDWARE IN PLACE. Patients may often have existing cosmetic implants/materials or metal hardware around the craniofacial area in which the implant is to be positioned. These implants/materials can be digitally removed if needed and do not prevent implants from being designed over their ‘ghost’ location. Often the size and location of existing implants is helpful in making the new custom implant design as the effect of what is already there provides a template for what needs to be changed.
THE CUSTOM IMPLANT DESIGN PROCESS EXISTS BETWEEN THE DOCTOR AND THE MANUFACTURER. While Medical Modeling and Implantech design and manufacture the custom implants, they work exclusively with doctors and not patients. They are not permitted to work directly with patients or have contact with them as dictated by the regulations of the US FDA. (Food and Drug Administration) Custom implants are prescription devices designed and made for one specific patient under the guidance of the doctor not the patient.
PATIENT DO HAVE THE OPPORTUNITY TO PARTICIPATE IN THE CUSTOM IMPLANT DESIGN PROCESS. Understandably patients are interested in how the custom implant will look and may feel that have a lot to contribute to how it is designed. Dr. Eppley encourages patient input into the implant’s design and in the end requires a patient’s final approval before it is sent to be made. Since patient’s are not allowed to participate in the actual online design sessions with the engineers, Dr. Eppley will take the patient’s suggestions/input into these sessions and share the PDF file of that design with the patients afterwards.
THERE IS A LIMITED NUMBER OF CUSTOM IMPLANT DESIGN SESSIONS THAT ARE ALLOWED. Because there are costs associated with the design process, there are not unlimited design sessions/changes that can be done. One is permitted three (3) design sessions/modifications that are included in the base cost of a custom implant. While further design sessions can be done, there will be additional costs to do so.
THE TIME PERIOD FROM 3D CT SCAN TO SURGERY FOR A CUSTOM IMPLANT IS SIX WEEKS. From the time the doctor receives the 3D CT scan until the custom implant arrives at the surgery center/hospital in sterile packaging is usually around six weeks. In some cases the design and manufacturing process can be shortened and expedited but it is a colloborative process in which haste should be avoided if possible.
THE FINAL DESIGN OF A CUSTOM IMPLANT MUST BE FINALIZED TWO WEEKS BEFORE SURGERY. Once a surgery date is established, the design of a custom implant must be completed well in advance to permit its manufacture, proper sterilization/packaging and shipping. No changes in the implant’s design are possible within this two week window without incurring a change in the date of surgery as well as adding additional costs.
PATIENTS CAN NOT INSPECT THEIR CUSTOM IMPLANTS BEFORE SURGERY.Custom implants arrive at the surgical facility in multilayer sterile packaging. It can not be removed from this packaging to be held or evaluated by the patient right before surgery as this will make it unsterile and unusable for surgical implantation. The confidence level in the custom implant must come from a review of the PDF design files before manufacture.
REVISIONS OF CUSTOM IMPLANTS IS A NEW CUSTOM IMPLANT. While computer designed custom skull and facial implants have an over 90% patient satisfaction rate in Dr. Eppley’s extensive experience, they do not always produce an ideal aesthetic result. As stated previously any computer designed implant is done based on a prediction or belief in what its impact will be on the final aesthetic appearance. This is where it pays to have your custom implant done by a surgeon who has a lot of experience in doing them. It takes this experience to appreciate how changing the bone affects the outside of the face or skull and an appreciation of how the greater surface areas of custom implants influence the aesthetic result. In rare cases a patient may want a new or redesigned custom implant, while this would be a revisional surgery it is a new custom implant from a manufacturer’s perspective.
Unlike facial implants, the use of skull implants for aesthetic head reshaping has a very short history. While the use of facial implants dates back more than five decades in plastic surgery, skull implants have been done for just a few years. It has not been that skull implants are radically different or more complex to perform, it is just that there are no preformed skull implants currently available. With facial implants, there are dozens of different preformed options for the nose, cheek, orbital rim, chin and jaw angle areas.
Until preformed standard size skull implants become available for certain head shape concerns, they will have to be custom made custom for each patient based on their specific anatomy from a 3D CT scan. As custom skull implants are becoming more used due to improved manufacturing technology, there is still little public awareness about them. Here are some things you may not know about custom made and manufactured skull implants.
Custom Skull Implants Have Made Cosmetic Head Reshaping Possible. What really separates skull from facial implants from an implant standpoint is their size. Covering broad areas of the skull (e.g., back of the head) creates an implant that would be equivalent to over 20 or more chin implants. Getting such an implant to fit well is much more difficult than smaller facial implants and the margin of error is actually much less because of its size. The custom design and manufacturing of a skull implant makes their use much more predictable for any skull area.
A 3D CT Scan Is Needed To Make Custom Skull Implants. Whether it is done by an actual model or on the computer screen, only a high resolution 3D CT scan of the skull can be used. The scan has to be done using .1mm slices and not the standard 3mm or 1mm slices normally taken. A regular axial or coronal head CT scan will not work nor will an MRI. Today 3D CT scanning is widely available, quick and easy to do acan be done for a few hundred dollars.
The Computer Only Designs What The Surgeon Tells It To Do. While computers and their software have remarkable capabilities, they do not yet know how to create a specific look for any patient. In designing skull implants, it is important to remember that the computer has no innate knowledge of what the size and shape the implant needs to be for what the patient wants to be. The surgeon must work with the design engineer to create the amount of skull surface area (shape) and thicknesses of the implant to create what is believed to cause the ultimate aesthetic outcome. The computer design process will make sure the implants fit the bone perfectly, compensate for any skull asymmetries, have a smooth outer surface and will minimize any edge transitions.
The Limiting Factor In Skull Implants Is The Overlying Scalp. Unlike facial implants, skull implants must carefully consider the tolerance of the overlying scalp tissue to stretch and accommodate it. Facial implants rarely have his consideration because they are smaller and the facial tissues have greater elasticity. The size of skull implants and the tightness of the scalp stretched over a large convex bony surface makes its design of critical consideration. Knowing how large and thick a skull implant can be is a matter of the surgeon’s experience. When the need for large skull implants exist, a first-stage scalp expansion may need to be considered.
Incisional Access Is Of Critical Importance In Custom Skull Implants. With large implants, the need to preserve hair follicles and to not create an additional aesthetic problem (scalp scar), the location and length of scalp incisions is critical. Despite most skull implant sizes they can be placed through relatively small incision in many cases because they are flexible. The implants can also be sectioned into two pieces and ‘reassembled’ once inserted if need be.
The concept of 3D printing of human replacement parts has been all over the medical and scientific news over the past few years. While each news release seems like it is revolutionary and new, most are the natural evolution of the refinement of 3D CT scanning and the ability to manufacture custom replacement parts from these images from various synthetic materials. This is of specific relevance to the skull and face where their complex anatomy make shaping natural tissues to fit difficult and often lacking inadequate donor volume to do so.
I have performed custom skull and facial reconstructions made of either HTR polymer or titanium for over twenty years…and custom silicone skull and facial implants for aesthetic enhancements over the past three years. As good as these synthetic reconstructions have been, there is always room for improvements and further technical advancements.
One of these has been in the evolution of improved materials for custom implant fabrication with the use of the polymeric material PEEK. (polyetheretherketone) This is a colorless organic thermoplastic polymer from the polyaryletherketone (PAEK) family. This material has excellent mechanical properties with a Young’s modulus of 3.6 GPa and a tensile strength of around 90 to 100 MPa. It is resistant to breakdown (melting) up to temperatures as high as over 340 degrees C (650 degrees F) In addition to resistance to thermal degradation, it is also highly resistant to breakdown by a wet environment or organic enzymes.
Custom implants made from PEKK were first FDA-approved in 2013 for cranial reconstructions and just recently approved in 2014 for facial reconstructive parts. (OsteoFab, Oxford Performance Materials) Through their processes it is possible to print patient-specific implants from either 3D CT or MRI scans. The implants are 3D printed and combined with laser sintering manufacturing technology and proprietary OXPEKK powder formulation to print skull and facial implants. These implants are biocompatible, mechanically similar to bone, radiolucent, and osteoconductive.
PEKK craniofacial implants offer several advantages over the traditional use of metal materials such as titanium or stainless steel. They have reduced weight, do not ever corrode, can be tailored to meet complex shapes with great precision and differing biomechanical loading properties. They also have a density and stiffness similar to bone and are radiolucent. (do not cause scan scatter) Some evidence also indicates that it has osteoconductive properties.
PEKK craniofacial implants is just one example in a long line of 3D printed biomedical advances. This technology and material allows complex craniofacial cases to be treated in a more precise manner that is ultimately more cost effective. While the actual implant(s) is not inexpensive, the savings in operative time and expense, need for donor site harvest and the high likelihood of subsequent revisional surgeries justifies the up front fabrication costs.
Background: Skull shape deformities are not typically perceived as an aesthetic problem. But just because they are not common does not mean they are not just as significant to someone who has it nor that they can not be improved satisfactorily. There are a wide range of aesthetic skull deformities that affect its entire length from the forehead back to where the neck muscles attach to the bottom end of the skull.
One of the most common aesthetic skull deformities is that of the flat back of the head. Occurring from either in utero or neonatal positioning the back of the head can suffer a non-neurologic deformation, ending up with a variety of flattened shapes. This flattening may or may not be associated with compensatory widening of the parietal bones creating flaring or widening in the back with the flat spot in between the two sides. (known as brachycephaly) While this can occur in anyone under the right circumstances, the Asian population is particularly prone to occipital flattening. This may be due to inherent development patterns in which front to back skull growth is naturally shorter.
While to the uninformed, flatness on the back of the head may be perceived as trivial and easily covered by hair. Nothing is further from the truth to someone who has it. I have heard many stories from patients abut the time and effort they put into styling their hair to camouflage it or from men who constantly wear hats to keep it covered. For some men what was once something they could feel, losing their hair begins a process of exposure of their flat back of the head and can serve as tbe the stimulus to seek a surgical solution.
Case Study: This 42 year-old Asian male had always been bothered by the flat spot on the back of his head. He routinuely spent time with gel products making his hair stand up in the back for camouflage. The flatness of the back of his head could be seen in a 3D CT scan with a severe drop-off from the top of the skull down. From this scan, a custom silicone implant was designed to cover the flat area with a central thickness of 8mms. He also had occipital asymmetry with the right side having a greater degree of flatness in which the design compensated by more material on that side.
Under general anesthesia, he was turned into the padded prone position. A horizontal 4.5cm incision was made low in the occipital hairline just below the nuchal ridge. Dissection was done down to the bone and wide subperiosteal undermining was done with long curved dissectors beyond where the implant edges would be in a 270 degree radius from the incision. The implant was prepared by making multiple ‘perfusion holes’ through it with a 3mm dermal punch. It was then folded for insertion, unfolded once inside, positioned and then secured with a single 1.5mm self-tapping screw at its lower edge.
The effects of the implant were immediate and no edge-transitions could be felt. The incision was closed in two layers with small resorbable sutures for the skin. He had some mild pain the first night but took no narcotic medications after the first 24 hours. He looked very ‘non-surgical’ the next day.
Having performed occipital augmentation with various materials, there is no question that using a custom silicone implant is the simplest approach. By its prefabricated design and the smooth silicone material, it is also the most assured way to avoid any palpable edge transitions of the implant to the bone. The placement of perforating perfusion holes allows for multiple points of fibrous fixation that will ensure that the implant will never move or migrate despite its smooth surface. Such holes also prevent any flexing of the implant in an area like the back of the head where it encounters frequent pressure when laying. (although this is more likely to happen in a non-custom implant that does not have a perfect fit.
1) Augmentation for the flat back of the head can provide a significant aesthetic improvement.
2) A custom occipital implant made from the patient’s 3D CT provides the most accurate fit for the flat back of the head.
3) A custom implant can be placed through a low horizontal skin incision at the base of the neck, which may be particularly advantageous in men,
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.