One of the areas we isolated for our summer intern as a “task of focus” was mold modification. Some technical education programs don’t put much focus on this subject because historically it has been the domain of the practitioner (more so in prosthetics than orthotics). This is changing rapidly, however. As practitioners become more involved in patient management and central fabrication becomes more prevalent, that old dividing line is shifting more toward the technician. Some have argued that this is a bad thing, using the rationale that since the practitioner consulted directly with the patient, the practitioner will know best what needs to be done to the mold. I can certainly see that point, but it is hard to expect a practitioner who has never been trained to work with his or her hands to make an artful mold. So I don’t think the answer is to have the practitioner modify the mold, but instead for the practitioner and technician to better communicate the desired results.

Of course it isn’t much more reasonable to expect technicians to make an artful mold when they haven’t been trained to do it. When I wanted to learn how to modify a mold, I sought out the best guy I could find and did everything I could to emulate the way he did it. He was an artist, and he taught me some fundamental rules about how to work with plaster. He made the nicest, strongest, and most attractive molds I had ever seen, and the technique is easy.

Rule #1: Smoothing the Mold

The first rule I learned was that the mold should be filed smooth before any plaster is added. Virtually all of the material you remove should be removed in the beginning. When you file a cast, look at the horizon, not the part of the mold that is facing up. By looking at the horizon, you can easily see the line you are filing. The contrast of the cast with the floor allows you to see a straight line much better than trying to look at the part of the cast that is facing up.

Also, always hold your file in a way that allows it to span across the high spots. Holding the file parallel to the cast (proximal to distal) allows the file to remove only the high spots. If you see file marks in the “valleys,” you are exacerbating the roping! Move the file in a spiral pattern and remember, pull a file for precision and push it for power.

Rule #2: Building Relief

Another fundamental rule is that half of the “relief ” you make on a mold comes from compressing the tissue surrounding a bony prominence; the other half comes from building up on the prominence itself. If you try to relieve a bony prominence just by building it up, you won’t effectively control motion and the prominence will still contact the plastic whenever the patient shifts in the device.

Rule #3: Saturate the Mold

Here is where the controversy starts.

Once the mold has been smoothed with a file and all the tissue compression is complete, it should be saturated. Most people work their molds with some moisture still present, and some people actually go out of their way to dry a mold before adding plaster. My way might sound crazy, but hear me out.

Have you ever noticed when you are trying to wet sand plaster, sometimes your buildups are much harder than the original material? This makes getting a smooth transition between the buildups and the original material difficult because the original plaster is softer than the buildups. This means the original material will sand away much faster than your buildups. The reason this happens is because when the buildup material is applied to a dry cast, the dry cast wicks the moisture out of the buildup, thereby increasing the plaster-to-water ratio. The higher the ratio of plaster to water, the harder the plaster will be. Subsequently, your buildups will be harder than the original material.

The method I use to bring these two materials into balance is to saturate the original mold in water. If the original mold is saturated, it won’t wick moisture from the buildup material. If you add material to a mold and you notice the buildup instantly becomes more dense, the mold isn’t saturated enough. If you use this technique, you don’t have to put vermiculite in your mold and your transitions will be as smooth as you want. This has the added benefit of keeping your buildups from falling off. Over the years I have seen some really crazy techniques for making buildups stick—adding Elmer’s glue, painting the mold with resin, and using plaster bandages for buildups. All of these may work on some level, but none of them will allow for a smooth transition and they all add a layer of avoidable effort.

With this process, you should allow the buildups to harden completely before final filing and sanding begins. You could argue that this takes more time, but it’s linear time, not “man hours.” It’s a bit like arguing that that it takes too long for a CAD carver to cut a mold. As long as it doesn’t increase the amount of work you have to do, it is irrelevant.

Exceptions Are the Rule

Over the years, we have spent a lot of time analyzing the process of modification, developing “algorithms” to help us understand what to do and when. Still, there are more exceptions than rules. Gone are the days of simply applying our standard matrix of modifications to every mold that comes in the door. You may use 1/4 inch on the medial malleoli, and 3/16 inch on the lateral for a starting point, but it is a guideline, not a rule. You must have an understanding of anatomy and pathology. You have to be able to imagine how the device is going to react to the patient’s inputs, and you have to be able to understand how the device will react to contact with the floor.

The next critical lesson is to keep it anatomical. The brace should be shaped like the patient. If the cast was taken properly, there really shouldn’t be much reason to change the overall shape. Humans, as a rule, are smooth. They are round, and they rarely have sharp edges. Our molds should reflect this. Sometimes we have to make mechanical changes to accommodate joints or flair the edges of the plastic, but the bulk of the brace should look human. The plantar surface of the foot, the areas around the malleoli, the shape of the thigh and around the knee—all of these shapes are dictated by the shape of the patient’s anatomy.

Accurately and comfortably translating the desired forces onto a patient’s anatomy is the foundation of modern O&P. How many times have you heard a patient say he or she had a thermoplastic brace once and it just didn’t feel right, and, subsequently, he or she never wants another one? It always makes me wonder what that first one looked like and whether the results could have been different if the mold had been more artfully modified.

Also published in the September 2011 edition of the O&P Edge. © 2011 O&P Edge

Our roles as technicians are, theoretically, pretty well defined. The practitioner has the clinical skills to understand each patient’s individual pathology and the experience to know what will best suit his or her lifestyle. The practitioner meets the end users, interviews them, reads their medical history, speaks with the referring physicians or therapists, and through all this investigation, comes to have a pretty good idea of the patients’ needs. Once the practitioner has a good idea of the parameters involved and the anticipated outcome, he or she generates a concise plan and then passes that information along to the technician. Then the technician has to take this data and overlay his or her understanding of the materials, designs, and components required to safely achieve the stated goals. Between the two of us—practitioner and technician—we are supposed to be able to work whatever magic needs to happen to help end users meet their orthotic needs. Most of the time this works pretty well, but sometimes the practitioner wants to do better, or the end user wants to do more, or the provider wants to do less, and we fail.

Over-Engineering vs Under-Engineering

Technicians frequently over-engineer a device. For years I was able to brag that I had never had a single prosthetic component I manufactured fail. Then I realized I had actually just admitted I had over-engineered the vast majority of what I had built. We are all guilty of developing a certain level of “scar tissue” in our design rationale. We have had similar devices, on similar patients, fail as a result of one parameter or another, and after a while we tend to play it safe. The problem is, of course, that when we play it safe, we can easily build a device that is substantially more stable than the circumstances require. This causes the device to be heavier or more restrictive than the patient demands. Then it gets put in the closet and is never used. Yes, the device may have worked, but in this situation we failed just the same.

Other times technicians under-engineer a part. This can be even more dangerous because the catastrophic failure of a part can expose the whole team to potential liability. Let’s face it, when people rely on the things we make to ambulate, the device’s failure can lead to serious injury! As much as we want to avoid this, we have to be aware of this balance. Even though it may seem necessary at times, we cannot let the potential for failure stop us from designing appropriate devices. If anything, we need to continue to explore newer, better designs and materials in an effort to move the industry forward.

The first trick to mitigating the risk of failure is to have a good understanding of all the materials we use. Whether we are dealing with metal, leather, plastic, or composites, we have to know the material’s limitations. Since most of the orthoses we make are essentially prototypes, it is very hard to use science to predict the outcome, so we have to rely on an innate understanding of how these materials will react in certain situations. With most materials we need to know the direction of the forces to be applied, the strain, tension, and shear forces they will have to deal with, and the environmental conditions they will operate in. We have to know which materials are appropriate for each design, and the only reason we know these things is because of the failures we have encountered.

Failure Analysis

The only way we can learn from the mistakes of the past is to communicate with each other. Technicians have to have a thorough understanding of all the parameters involved. How many times have you used “B”-sized joints on a 120-pound post-polio patient only to find the person in question is highly active and has a history of breaking joints? This is information practitioners frequently omit from the orthometry form, so as technicians, we have to be careful about interviewing practitioners to get any information we may need to make a decision about component selection. Ideally, the practitioner will specify these parameters, but if they do not, you need to be bold about acquiring this data! When a failure does occur, we need to debrief the whole team. Everyone needs to understand the failure and learn from it.

Things break. We know that and we can’t always see it coming. When they do break we need to know why! So failure analysis is critical. We need to know the circumstances involved in the incident, what the user was doing, how old the device is, if the device was under-engineered, and if the device was used beyond its original parameters. There is a science to failure, and each occurrence can tell us a great deal about how and why a design failed. Don’t just throw a broken part away! Stop and examine it! Most devices will give up their secrets pretty easily. Between a basic interview with the user and a visual analysis, you can usually see what went wrong. If the part in question was manufactured off site, it needs to go back to whoever made it; the manufacturer is the one who most needs to understand the failure!

One of the biggest design obstacles this industry faces is the lack of a central database for failures. With the advent of evidence-based practice, we can begin to develop a more fundamental view of the potential for failure. This is good, but if we have several hundred separate pools of “evidence,” the industry will be slow to react to the potential for a given design to fail. If this data could be collected and centralized, it would afford a much more uniform approach to the designs of tomorrow. There’s at least one repository for failed components operating today, but the availability of a U.S. repository with critical data about the failure—not only of components but also of finished devices—would go a long way to establishing some basic design criteria for the products we make and secure a more positive, and safer future for the people we serve.

Earl Nightingale said, “When we succeed, we party, and when we fail, we ponder.” Only through failure can we establish boundaries and build a foundation for the development of a better industry.

Also published in the July 2011 edition of the O&P Edge. © 2011 O&P Edge

For those who don’t know about TPE, it is basically a marriage of an olefin material (like polypropylene) and vulcanized rubber. It is a commonly used material in a lot of industries. The automotive industry uses it for the flexible skirting around bumpers and for suspension bushings, and it is used in the medical industry for things like catheters and other types of tubes. TPE is a great material because it offers the thermoplastic characteristics of polypropylene with rubber’s flexibility. This allows you to fabricate devices that are more bio-synergistic. Devices fabricated from TPE offer a broader window for control but will yield to overwhelming forces, making the device far more comfortable even when applying a substantial corrective force.

The patients we switched from a conventional polypropylene AFO to a TPE AFO instantly noted the increased comfort, and the patients we started out in a TPE AFO rarely complained of discomfort. In situations where our objective was to correct foot drop, the TPE AFO would easily accomplish this without having the normal range of motion (ROM) restrictions in the frontal or the transverse plane. By helping the patient to achieve a more normal ROM, compliance goes up, and stride length increases. Oxygen consumption should decrease as well.

Of course it begs the question, if this stuff is so great how come almost nobody uses it anymore? For starters, there is a bit of a learning curve involved in adopting this material.

The O&P profession is famous for being slow to adopt new technology, and TPE is no exception. Since the material typically heats at a lower temperature than conventional polypropylene, one of the first problems people noted is that, when heated, the material quickly goes from a nice workable consistency to a stretchy, stinky, near-liquid mess. Of course, this only happens if you try to cheat by heating the material in an oven set at a steady 400 degrees. If you turn the oven down to 325 degrees and take the time to let the material heat more slowly, it is very workable and easy to handle.

When properly heated, TPE’s consistency is similar to polyethylene, and once it is formed it is very stable. It doesn’t tend to expand or contract in the presence of a foam liner, and it easily molds around even the deepest undercuts commonly found when a thermo-insertion joint is present. Back in the old days, when most of us were using gas or electric convection ovens, taking the time to drop the oven temperature down was a pain, but now that most of us have gone to infrared ovens, this happens pretty quickly, so there really isn’t a good excuse to cheat.

Another turnoff with TPE is the price. Selling at roughly four times the cost of polypropylene, it can be a hard sell in these troubling economic times. The upside is that the actual material cost of an AFO is usually not the dominant factor in the overall production expense, labor is. Since TPE is easy to form, cut, and grind, I think the labor time to fabricate a TPE AFO is actually a little less. This may not fully compensate for the greater material expense, but once you factor in comfort and ease of fit, I think the cost becomes less of a factor than you might think.

No material is perfect for everything, and TPE is no exception. Because it has a tendency to cold forge, or change with repeated impacts even when there isn’t any heat present, it can have some limitations. Typically, you would not want to use this material for a patient with severe frontal plane disorders such as ankle valgus or ankle varus because TPE is too yielding. But for sagittal plane disorders like foot drop, or transverse plane disorders like mild posterior tibial tendon dysfunction (PTTD), this material is perfect—it has just enough control to fix the problem without all the rigidity of a traditional polypropylene AFO.

TPE has one other trick up its sleeve. Like many acrylic plastics, it is hygroscopic. Basically, it slowly but surely absorbs water from the atmosphere. In its cold state, this isn’t really a problem, but when you put a sheet of old TPE in the oven, the heat can cause the water molecules to expand and form nasty-looking little bubbles in the sheet as it heats up. The bubbles generally appear well before the material is up to a high enough temperature to thermoform, and if you think the bubbles will disappear as it cools, think again. They are there to stay, and it can make for a pretty ugly piece of plastic. If you have old material, you have two choices. You can either throw it away and order new, or you can desiccate it.

The desiccation process is simple, but it takes a little time. We just put the TPE in the oven at about 200 degrees, leave it for a few hours and slowly ramp the temperature to 350 degrees. If you do this slowly enough, the water will evaporate without expanding to the point where it causes visible bubbling. Most suppliers ship TPE with a barrier film nowadays, so this is rarely a problem anymore unless it hangs around for quite a while. In Florida, where the humidity is frequently above 80 percent, it can be a struggle to store TPE for long periods, but with a little patience it is a problem we can work around.

If you have ever worn an orthosis, especially an AFO made from TPE, you will quickly notice the advantages. It’s easy to make shapes that are more aggressive and yet more comfortable than with other materials. Rather than rely on padding to add control pressure, you can actually make the device do all the work. It is thinner this way and fits better into the shoe, and it offers much better toughness than materials that are similarly flexible.

Every material we work with in this industry can be problematic on some level. But each material also presents us with an opportunity. I remember when acrylic resins were introduced—they were expensive, stinky, and a real pain to work with. But because they were inherently more rigid and a good bit stronger than the old polyester resins, we stuck with them, worked out the bugs, and never looked back. TPE demands the same basic approach. If we want to offer our patients the best possible sheet material for their particular circumstance, sometimes we have to work through the bugs.

Also published in the March 2011 edition of the O&P Edge. © 2011 O&P Edge

So when the Orthotic & Prosthetic Technological Association (OPTA) board of directors sat down to build this year’s technical education program for the 2010 American Orthotic & Prosthetic Association (AOPA) National Assembly (OPTA co-sponsored the tech ed. program), we decided to include hands-on workshops. The program was scheduled to be seven hours long. This sounds like a long time when you first sit down with a blank sheet of paper. In reality, however, it really isn’t an adequate amount of time to transmit enough information to make the trip worthwhile for most technicians. So how were we going to make sure the information we provided to those who did attend was valuable? If high-quality technical programming is the goal, then kinesthetics is the method of choice! The questions that remained were “What do we do?” and “How in the world do we do it?”

What? How?

Brad Mattear, MA, CFo, of O&P1 fame, answered the “What?” question for us. In some of our conversations, board members discussed thermoforming over foam models for AFOs. Five years ago, most technicians had never done this, but now it is becoming common practice. The problem with thermoforming over foam models is that there are a lot of different techniques being used—some science, some voodoo, but nothing conclusive that we could share with the world. We saw this as an opportunity not only to teach, but also to do what technicians do best—share.

We achieved the “How?” by assembling a working lab and testing a few of the more popular methods to figure out which one or ones had the most merit.

The hardest part of developing a hands-on education program is actually doing it! If this had happened in my lab, or any other lab for that matter, it would have been a piece of cake. I mean, we would have had to clean up a bit and maybe rent some chairs, but we would have had everything we needed and know right where everything was. A hotel conference room is a whole different story—no oven, no vacuum station, no scissors, nothing. We had to assemble everything! Granted, it would have to be a stripped down version of a lab, but we needed to have everything there, which meant we had to pack up and ship all of our equipment and tools across the country, reassemble everything, and make it work. We knew we wouldn’t have 220-volt electrical systems, dust collection, or even running water. Fortunately, this wasn’t our first traveling rodeo. Most OPTA board members have years of experience doing hands-on programming all over the country. Surprisingly, it almost always works. This was no exception.

This year’s technical education program was special because it was the first time we really focused on learning from each other rather than just imparting information. The subject of thermoforming over foam models is so new and mysterious that none of us has all the answers; in fact, we barely have any of the answers! So we didn’t just want to preach from the front of the room—we wanted the attendees on their feet, talking with one another and sharing. It is through this type of interaction that we learn the most.

The program began with a great presentation on lab safety by Don Pierson, CO, CPed, of Arizona AFO, Mesa, and then, to make sure we covered all our bases, Peter Panuncialman, president of Windy City Fabricators, Chicago, Illinois, gave an overview of various prosthetic fabrication techniques. We then moved on to the main lecture. To make sure we all developed an understanding of the physics behind thermoforming over a foam model, we asked Gary Bedard, CO, FAAOP, from Becker Orthopedic, Troy, Michigan, to explain exactly what we were up against. He took the complex science of thermoforming and distilled it into a very useful set of parameters.

Once the lecture was over, it was time to get down to business. We were glad to be able to pull in the talents of Jim Williams and Ed Fry. Jim is the go-to technical guy from SPS, Alpharetta, Georgia, and co-owner of Peaster & Williams Central Fab, Cumming, Georgia; Ed is a team leader at Hanger Prosthetics & Orthotics’ Orlando, Florida, fabrication site, where he pulls plastic on foam models all day every day, so they have both developed some very workable techniques for getting this done. Last but not least, I scoured the web to find a technique that was popular yet seemed like it would be an unlikely answer to the problem at hand.

Education In Action

The object of this exercise was to end up with a conclusive technique for thermoforming over a foam model, so we had five exact copies of a scanned mold cut from the same four-pound foam. (Three were for use; two were cut as extras, just in case.) Then we cut five sheets of the plastic from a single sheet of 3/16-inch polypropylene. The sheets were cut in the same direction and in the same size. Participants heated the material to the same temperature and applied the same vacuum force to all the pulls. The only thing that changed was the set-up—each pull used a slightly different set-up technique and a different interface.

The first was pulled with a single pantyhose covered with a PVA bag. The bag was then perforated to allow vacuum to flow through it. This technique was first described to me several years ago and is very fast to set up. You need to be careful to smooth out the PVA bag, which can sometimes be difficult because, as most of you know, those things aren’t designed to go around an AFO mold. All in all, it worked well. The surface wasn’t as nice as what we would traditionally expect, but considering the makeshift nature of our lab, most would have called it a success.

The second process was even more simplistic: one moistened layer of cotton stockinette followed by one moistened layer of Nyglass stockinette. The finish was pretty smooth, and it worked quite well. I don’t know if the glass content has any effect, or if it is just the surface texture that imparts a smooth surface, but either way, it left a finish most technicians would characterize as acceptable.

The third process was one I have known about for years and have been skeptical about for almost as long. It involves applying two pantyhose to the mold and then spraying the outer hose with a generous coat of 77 spray glue. A healthy coat of talcum powder is then applied over that. While I have used this technique for years to keep small areas of stockinette from sticking in a pull, such as over a Tamarack joint or a pad, the idea of using this for a large area sounds improbable. Needless to say, this was the only real failure of the three techniques tried that day. The stockinette welded to the plastic and could not be removed. While this provides a consistent surface texture, it is very rough and will absorb whatever fluids it comes in contact with. Not good.

After each of these pulls, we cut off the finished part and measured them to see if there was any obvious discrepancy with the supplied mold shape, and there was. The downside of pulling over a foam model is the obvious difference in the cooling rate of the inner and outer aspects of the material. We have known for years that slowing down the cooling rate of the inside of the plastic causes the plastic to curl in. This happens when we pull over a foam liner and was obvious in all of the finished products. Each exhibited a similar rate of part instability once de-molded. While we did find several successful techniques for achieving a smooth inner surface, we clearly don’t have all the answers yet.

All in all, we discovered two things. First, we need to do a lot more research about this emerging technology, and second, we as technicians need a lot more opportunities to gather and share ideas. Both of these discoveries exemplify the challenges that our changing profession faces. As with every challenge we have encountered, I am certain that both will be met.

Also published in the December 2010 edition of the O&P Edge. © 2010 O&P Edge

When it comes right down to it, it only takes three things to make a great orthosis: a great cast, accurate measurements, and clear instructions.

If I don’t have a great cast, I can still make a brace—not a great brace, but a brace nonetheless. I’ve wrapped a few casts over the years, and not all of them were “great.” I realize that this is going to happen. Sometimes the patient is uncooperative, sometimes the casting environment is less than ideal, and sometimes it’s just an off day. It’s not the end of the world. I have learned to make corrections that will allow me to still net a positive end product. Sometimes, however, the difficulties are too great to overcome.

In the central fabrication business, we see everything from the best of the best to the completely unusable. The vast majority are somewhere in between. The key point to remember is that the people who send us the best casts also tend to enjoy the lowest redo rates. I tell orthotists all the time: “Your job is to take a perfect cast, and my job is not to screw it up!” The closer the original mold is to the desired shape and angulations of the finished product, the less I have to guess at it. If I have to make gross angular adjustments or move tissue around to normalize the shape, I have to make some substantial assumptions. The biggest assumption is that the shape of the limb is “normal.” The fact of the matter is that people with normal physiology rarely come to see an orthotist.

While I’m divulging my secrets, here’s another one. I don’t need measurements. That’s right folks, you heard me correctly: I don’t need measurements because I don’t have to fit the brace—but orthotists do! Most technicians will be happy to guess at it if you want them to, but when an orthotist has to walk into the fitting room, those measurements take on a whole new meaning. Let’s face it—if I have accurate measurements, I can do a better job of dialing in the fundamentals such as knee center, thigh circumference, and foot length. All these things can ruin a brace if I get them wrong, but if I’ve been given a great cast, this usually is not an issue.

Charcot Restraint Orthoses (CROs) are a perfect example. These devices are generally built for people with some history of volume fluctuation and, similar to prostheses, they are usually total contact. Depending on the time when the cast is taken and the length of time required to fabricate the device, there can be a significant volume change in the affected limb. So you cast the limb, we fabricate the device, you fit the device, and I get the call.

“This CRO is too tight.” Or, “This CRO is too loose. What did you guys do?” I ask, “How does the patient compare to the original measurements?” The answer? “We don’t take measurements; we just go by the cast.”

The fact of the matter is, we rarely add or remove a lot of material during modification, and certainly not the amount it would take to make a gross difference. So how do you know what led to an ill-fitting device? The short answer is, without measurements, you can’t. Not only can we not tell whether the patient changed or not, we also cannot tell whether we over-modified the mold. So what do you do? Do you re-fabricate the device only to find at the next fitting that the patient has once again changed volume? Do you try to adjust the device and instruct the patient on how to regulate his or her volume? Accurate measurements make it instantly apparent where the problem is and provide a clear course of action to correct it.

Last but not least, if you want an orthosis that not only fits but functions and meets the patient’s needs, you have to tell me what you want! I’m still stunned by how many casts I get with just a business card stapled on the side of it. No notes, no nothing. Don’t get me wrong. Having to stop what I’m doing to call a practitioner and get fabrication instructions doesn’t bother me at all. On the contrary, talking to my friends in the business is one of my favorite parts of my job. The problem is that in the time it takes for the device to go through your in-house systems and travel to our facility, there is a good chance you will have forgotten a lot of the critical details about your interaction with the patient and about the subtle nuances you discovered during that interaction, and that means a lost opportunity. It’s easy to miss a critical detail, and having to remake an orthosis because a minor detail was forgotten not only wastes your time and money, it also wastes your patient’s time and money.

I realize that sometimes we can get caught up in the business of selling orthoses and prostheses, but really, our job is to change lives—to do everything in our power to help our customers realize the greatest possible increase in their quality of life. To meet that mandate, we all have to do our best. We have to slow down, understand our patient’s needs, take some notes, take as good a cast as we possibly can, and take accurate measurements—in short, live up to our own image of what we would want from someone in our profession.

So remember, unless you are a magician capable of fixing whatever I throw at you, realize that I probably can’t fix whatever you throw at me.

Also published in the September 2010 edition of the O&P Edge. © 2010 O&P Edge

Tony Wickman, CTPO

It’s been said that America’s favorite color is shiny, and I agree.

Pre-preg is great. Really, it’s a wonderful material—high strength-to-weight ratio, easy to engineer, highly repeatable—but there’s just one problem…it’s ugly! The usual method of using a cloth wick and a breather layer to remove excess resin during the curing process leaves a dull, abrasive finish that just isn’t what we are used to in this industry. Usually, your only options are either to be okay with ugly or do a lot of post-production work to make it pretty. Some people sand the material smooth and spray it with a coating, and some actually laminate over it to achieve a nicer finish. Both of these methods work but require investing a lot of extra time. I was never really satisfied with either of these options, so my team kept working to figure out some way to get a really nice finish on our pre-preg components without having to do any of the crazy, time-consuming things I’ve seen people try to make this stuff acceptable to the consumer. I mean, let’s face it—it can be an amazing material, but if it’s ugly, we can’t sell it. After a lot of trying, we finally got the solution down.

An outer layer of polyethylene is applied over the layup.

The fix actually came from some early problem solving. When we first started to work with this material, everyone said that the water in the plaster molds was a major problem for the pre-preg, so a lot of people suggested using dental plaster, extra hardeners, or all kinds of voodoo fixes that would help maintain the strength of the mold while it was being subjected to the extensive drying cycles. Most of this came from the idea that the experts were using PVA bags as their inner surface! PVA is smooth and easy to apply, but it’s water permeable! If water was the problem, why on earth would we use a permeable barrier? We fixed the problem by using a very thin polyethylene inner layer. It’s cheap, easy to apply, allows us to use the same plaster mold material we use for all our other molds, and no matter how wet the mold is, it never interferes with the pre-preg! One byproduct of this technique was that the inner surfaces of the devices we fabricated were beautiful! Their outsides, however, were not that nice looking. We tried PVA, we tried silicone, and we did have some success, but we just couldn’t get the outside to look like the inside.

The obvious answer was to use a polyethylene layer on the outside as well, but it wasn’t that simple. Pulling an inner layer of polyethylene is easy—you just use a separator (a fabricating hose) to wick the air out—but if we used a fabricating hose between the inner and outer layers, it left a texture on the inside of the outer piece of plastic, which then transferred to the outside of our pre-preg. If we didn’t use a separator, the material cooled in random patterns and wasn’t smooth.

So the trick became pulling a very thin layer of polyethylene over the polyethylene inner layer without using any kind of wicking layer that would leave a pattern on the inside of the outer layer. We tried a few different parting agents until we finally settled on Liquid Wrench® Dry Lubricant with Cerflon. It is designed to go on wet and then dry out, leaving a layer of Cerflon (a combination of PTFE and boron nitride) behind. This effectively stops the layers of plastic from sticking together and still gives a very smooth surface.

The finished layup is shown under vacuum.

At this point, you might be wondering how we made up for the volume of the pre-preg material between the two layers of plastic since we didn’t allow for that in forming the outer layer of plastic. The answer is simple: we didn’t. We just cut the outer layer a few centimeters beyond our intended trim lines, layed up our pre-preg, and then applied the outer layer of plastic over the pre-preg material. By adding a few layers of fabricating hose over the outer layer of plastic and covering that with a PVA bag to act as our vacuum vessel, we could pull an effective amount of vacuum, and as the material ramped up to temperature, it “reformed” to fit the mold.

The process is simple: Modify the mold as standard. Add one layer of fabricating hose and pull a uniform layer of polyethylene over the entire mold. If no liner is to be used, then 1/16 in. is fine; if you plan to use a liner, you can pull a layer consistent with the thickness of liner you will use (1/8 in. liner = 1/8 in. polyethylene, for example). Sand down any seams that may get in the way, spray with the Liquid Wrench dry lubricant, and let it dry. A quick buff of the lubricant, and you’re ready for your next layer of polyethylene. For this layer, 1/16 in. is fine, and feel free to stretch it as thin as you can. Remove the entire outer layer. Trim this outer layer to extend just a few centimeters beyond your desired trim lines and discard the remainder of the second layer.

The finished pre-preg is smooth and shiny, inside and out.

Now, just lay up your pre-preg in the predetermined pattern directly on top of the first layer of plastic and then apply the second layer over that. You still need to be concerned with removing as much excess resin as possible, so apply a few layers of smooth wicking agent to the outside of the entire mold and then apply a PVA bag to the outside of that. Apply vacuum as usual, and the layup will be de-bulked. Use a slightly longer ramping time to ensure that you evacuate as much resin as possible, then give it a short heat cycle to ensure the best curing of the final piece. The result is a component that is strong and attractive, with no postproduction effort required.

Also published in the May 2010 edition of the O&P Edge. © 2010 O&P Edge

Update – August 17, 2010

I created a pre-preg PTB brace, utilizing the techniques outlined above. The orthosis was super lightweight with really good axial loading capabilities.

PTB brace utilizing our pre-preg 'should be patented' process.

Tony Wickman, CTPO

I’ve been thinking for the past decade that the technician’s role has been evolving from an entry-level point of ascension into a viable career. In the past, technicians tried to become practitioners and only remained technicians if something got in the way. However, as technology progresses and consumers become more demanding, our role will ultimately call for more knowledge and competence. In fact, it’s now becoming too difficult for one person to serve as both practitioner and technician. The two roles have become distinct and similarly difficult. Each has its own challenges. In short, they’re separate but equal.

Currently, the highest credential the industry affords a technician is ABC registration, which was developed as an entry-level credential for individuals who had attended a technical-education program. It has blossomed into an all-inclusive credential that is available to any technician with a high school diploma, who has graduated from an accredited technical program or has two years experience in each discipline, and has passed the day-long technician exam. This model served well for many years. Registration was valued because most registered technicians earned more than their non-credentialed counterparts, and it indicated that a technician was serious about his or her work. Registered technicians were seen as more of an asset to their employer and were generally rewarded as such.

In 1997, ABC began to require continuing education for registered technicians in a model that basically mirrored the requirements for other credentialed individuals. This move was lauded by most of us involved in the process because we all wanted the same thing: an increase in the stature of the technician’s role. The end of the first MCE cycle revealed something startling: about one-third of previously credentialed individuals failed to meet the new requirements and therefore lost their registration status. Since that time, the number of individuals seeking credentialing has declined; this attrition continues to this day.

Why are technicians no longer seeking this credential? I have asked this of technicians nationwide over the past year. Most technicians don’t understand the importance of credentialing as a career move or as a protective measure for the industry. The remaining technicians simply don’t care because it doesn’t directly impact their job. In my opinion, both of these points have some merit, but both are ultimately wrong.

Credentialing is a gateway to opportunity. If you aren’t credentialed, you have no voice in the field. No one knows you exist, and subsequently you don’t matter. You can’t join most of the industry’s most prestigious organizations, you don’t get on the mailing lists for continuing education, and you don’t get to help steer the ship. Why be a part of an industry that controls you without the opportunity to help shape the direction it goes?

Though some people do their work just to get by, most of us are in this industry because we care about our customers. We want to help people live as actively as technology will afford, and we want the devices we manufacture to afford patients the maximum possible increase in their quality of life. How can we achieve these goals without credentialing and continuing education?

We can’t just blame technicians. The whole landscape of this industry has changed. Providers are paying less, materials are more expensive, paperwork eats more of our time, and regulatory changes make it more difficult to get the available technology to the people who need it. For a lot of people, the expense of credentialing is just too great in time and money, and the return on investment isn’t there. More and more, the act of credentialing and continuing education is becoming altruistic. Most do it simply because they feel a strong desire to climb whatever mountain is put in front of them. That has to change.

We need to make technical credentialing and continuing education less expensive, and we need to make it mandatory. Several ideas have been put forward to meet these needs. The move to an Internet-based exam has been proposed, and I think it’s a good idea. Initially, I wondered how we’d test hand skills over the Internet. In industries as varied as personal exercise training and massage therapy, though, this has been the norm for years. Current technician testing doesn’t include hand-skills testing anyway; at least, it doesn’t include standards for quality or attractiveness—they’re too subjective. We instead test for all the other information and skills required to ensure minimum competency.

I know, I know—mandating credentialing as a component of accreditation is a real can of worms. But think about it—if credentialing was mandatory for accreditation, it would get done. How many times have you not done good things just because you lacked momentum to do them? If you had to do it, you would, and you would benefit from it. Just think about it—that’s all I’m asking.

I realize these ideas will not appeal to everyone, but I hope they will be provocative and spur some of you to develop better solutions, because there is more to do. If you like these ideas or hate them, tell me so we can consider your point of view. If you don’t speak up now, you may not have another chance. This is a fork in the road, not a dead end—we have to go one way or the other.

Also published in the March 2010 edition of the O&P Edge. © 2010 O&P Edge

Tony Wickman, CTPO

Metal orthoses are simple to fabricate. I once visited a brace shop in Port Au Prince, Haiti, which was staffed entirely by people who were deaf mute. They made crude but very effective orthoses with little more than an anvil, a drill press, and a lot of files. They made their own rivets out of discarded nails, used cold-rolled steel for the bands and bars, and just filed the ends of the bars to create joints. It’s becoming less and less common to see even basic metalworking tools in most facilities these days, so a lot of technicians become frustrated by metal work. Though metal orthoses are simple to fabricate, some specialized tooling is needed to make the job easy and efficient. They also require practice. It’s hard to get really good at something you do twice a year with half the tools you need.

One of the primary reasons metal orthoses are used is that they’re really rugged. Even today, with modern thermoplastics and composites at our disposal, just the phrase “rugged orthosis” conjures images of Mel Gibson in the Mad Max movies wearing his old Pope Klenzack AFO with the joints on backward. This is one Hollywood image that is rooted in reality. These designs have long been favored by hard-working farmers, factory workers, and heavy-equipment operators. However, they can also be made to be quite light. Using lightweight aluminum and thin-gauge bands, you can produce devices whose weight, with the shoe factored in, compares to some thermoplastic designs.

Metal braces also offer a level of torsional rigidity that can’t be matched. When you’re trying to reduce genu varum or genu valgum, that rigidity allows the device to resist medial or lateral loads very well, even when there is a rotational element. If your primary pathological force is in the sagittal plane, such as a knee-flexion contracture or hyperextension, a conventional metal device is a great way to manage those forces. The inherent shape of the mechanical structure is normally a dual parallelogram. This shape allows the device to resist forces in every plane with a very small cross section. That means we get a lot of strength from a fairly small mass, and the patients get a lot of control without a lot of weight.

Metal orthoses usually offer a very small contact surface. This can be a disadvantage in cases with tissue damage or where tissue requires a broad, low-pressure contact force. A lot of people don’t need that, especially in warmer climates! If the patient has good tissue and the forces required for correction can be limited to a small area, then a metal orthosis can work well. Even in cases in which the contact patch has to be increased, this can often be done with a leather lacer. Less contact means less heat build up, less opportunity for impingement, and more comfort.

Metal orthoses are normally attached to a shoe, which presents its own set of pluses and minuses. Frequently, (especially with KAFO patients) the foot may not actually be involved in the pathology. If, for instance, the device is intended simply to correct genu varum, involving the foot could be counter-productive. When a thermoplastic foot cup is used, the patient will lose some ankle motion, inversion/eversion, and proprioception. These are all important mechanisms for normal locomotion. The attachment of the device to a shoe will maintain a lot of these factors as “normal.” Attaching the device to the shoe might limit footwear choices, even when a split stirrup is used, but the use of a plastic foot cup does not imply an unlimited choice of shoe options. Lastly, having a visible stirrup can be perceived as less cosmetically acceptable for some wearers, but for many the increased comfort and function are more than enough to offset this.

Of course, we get to use a lot of different materials in this industry, and just about all of them have a demographic to which they can be appropriately applied. Whether it is the comfort and control of thermoplastics, the low mass and high strength of composites, or the open, rugged designs of conventional metal, there is something for everyone.

Also published in the November 2009 issue of the O&P Edge. © 2009 O&P Edge

Tony Wickman, CTPO

When I started out as an orthotic technician over 25 years ago, I believed you should always flatten the plantar surface of an AFO mold. That’s what I was taught because it was the conventional wisdom of the day. Then I had the opportunity to work with a group of physical therapy students. I felt secure in talking with the students about my techniques, because I thought I was applying the best we had to offer to the science of rehabilitation.

The students toured the lab and remarked that we were doing some amazing stuff, until they saw how we were modifying our molds. One of the students posed a question, “Why do you flatten the bottom of the foot when you modify the mold?” I answered that we were building mechanical devices, and that flat surface was our foundation. Wasn’t it?

After that, I started to question my fundamental beliefs on how to build a quality device. I was fortunate to have spent my first few years as a technician with some visionary orthotists, and what they taught me made sense, but at this point, I started to think we might be overlooking a very important part in the process, the part where modifications are made so that a device will become an extension of the patient. I noticed when we make arch supports, we never flatten the plantar surface. On the contrary, arch supports mirror the plantar surface. So what’s the difference between making an arch support and an AFO? Why would we think an arch support should take advantage of the curvatures of the plantar surface, but the bottom of an AFO or other orthoses should be flat?

Not long after that encounter with the physical therapy student, I had the opportunity to work with another visionary, a physical therapist and author, who was teaching a class on Neuro-Developmental Treatment (NDT) at that same physical therapy school. She had a test subject for the NDT class and needed a volunteer to fabricate an AFO. Naturally, our lab was offered and I worked one on one with her, and she helped me understand the intricacies of the foot: its bones, nerves, tendons and vascular structures, and how each of these components have their own set of needs. After working with her, I was convinced that technicians must see the foot as the foundation of an orthoses, not the floor! I knew I had to learn more about pedorthics, tone inhibition and neuro-developmental techniques if I wanted to create bio-mechanical devices, devices that fit properly, as well as focus on the specific pathology without causing any collateral damage.

This level of knowledge is beyond the standard education for technicians, but if I am modifying a mold, it’s my responsibility to know about physiology, neurology, and pressure mapping. Every patient who needs a brace has a pathology. Seldom are those pathologies purely orthopedic, there are typically underlying vascular or neuropathic disorders as well. There is no orthopedic solution for a neurological problem.

Technicians need to be aware of this when building a device, and practitioners need to be aware of this when taking a cast. If the cast is taken weight bearing, on a flat surface, much of the plantar data disappears. When a cast can be taken on a foam block, semi weight bearing, or even hand manipulated, that cast takes on a whole new level of function. The surfaces of the foot become much more natural and the load pressures can be more accurately distributed. Neurological inputs can be reduced and deep-tissue weight-bearing techniques can be utilized, and the brace can better fit the patient. One of the issues with casting a patient on a flat surface or flattening the bottom of a mold is that the device created from that mold can cause collateral damage, by creating excessive pressure on at risk tissue, or exacerbating existing problems and putting the surrounding tissues at risk.

No matter the casting technique, I can make a device, but it may not function properly, and it will certainly be less comfortable for the patient. I see these issues most frequently with neuropathic (CROW) walkers and pediatric devices. I’ve worked with many practitioners to help them change their casting technique for these devices, and by doing so, they are seeing better results with their patients.

I believe a technician’s role is to understand and interpret the orthotist’s vision for the patient and make that vision a reality. I also believe the practitioner and technician should work together as a team to make a device that will assist the patient in the best manner possible. If I don’t have an understanding of the nerve structures on the foot, then it’s probable that I won’t make a properly functioning device. Orthoses are not “widgets” that come off an assembly line, they are custom-made bio-mechanical devices that help improve the quality of life for the people who use them.

In order to increase the overall caliber of the rehab team, I suggest that you learn as much as you can about pedorthics, tone inhibition, and neuro-developmental technique. The manipulation of the surfaces of the foot is the foundation of a good lower limb orthosis and these specialized disciplines will give you a good foundation upon which to build your skills.

Tony Wickman, CTPO

I discovered that a couple of techs had little stops or V-shaped blocks, but for the most part, these devices were kind of sloppy holding fixtures. I was pretty sure that with a little ingenuity we could do better.

I knew we wanted to hold the molds rigidly, and ideally, to bolt them down. The problems were that (1) each mold is a little different, and (2) we’d have to embed a nut in the mold. Anything with a nut in it would need a holding fixture to keep the nuts flat and square—otherwise, they’d break the mold when we tightened them. And the nut would have to be submerged below the actual surface of the mold so we could flatten the mold’s bottom without hitting the nut.

Basically, we needed an adjustable holding fixture that would allow us to drop the nuts into the wet plaster cast and hold them in the correct alignment. It would have to be easy to make because we’d need a lot of them.

What we came up with was a flat piece of band stock that was 1.5 in. by 14 in. long (long enough to span a bio-foam box), with slots milled down the center for adjusting the spacing of two nuts. We used ¼-20 zinc T-nuts (they’re cheap and really bite into the plaster) with small plastic standoffs through which the bolts could pass to allow us to actually submerge the T-nuts.

How to Do It

Pass a ¼-20 zinc bolt through the metal plate, drop a plastic standoff onto the bolt, then secure the T-nut to the bolt. When you snug the T-nut down, it pinches the standoff and the plate together and holds everything tight (figure 1). Set one nut dead center into the deepest part of the heel and one in the met heads, then snug them down.

Prepare the mold as usual, then pour wet plaster into it. While the plaster slurry is still wet, drop the jig (nut-side down) into it and let it harden (figure 2). Once it hardens, spin out the bolts and use pliers to pull out the standoffs.

Next, flatten the bottom of the mold; you’ll hold on to the nuts with another jig. Take a 24-in.-long piece of ½-in. by 1½-in. aluminum and mill two slots into it. Match these slots to those in the pouring jig exactly so you can line them up. Then mill the holding jig down so you can slide it into the pipe mandrels you use to hold other molds. To give yourself more options, flatten the jig’s sides so the jig can be held in a vice, and drill mounting holes in case you decide to mount it permanently to a bench. Buy some ¼-20 knobs that you can tighten by hand to allow for quick connection of the mold to the jig (figure 3).

This process is fast, simple, and highly effective. With a small investment in time and tooling, you can turn one of the more difficult, time-consuming tasks in your production line into a positive revenue generator that meshes well with the rest of your production, and you have a cool new tool!

This article was originally published in the September 2009 issue of the O&P Edge © 2009 O&P Edge