TPS Archives

Reprints From The Professional Skier

Spring 1998 - "Embrace New Advances In Technology" by Bob Emerson and Matthew Albuquerque

This article is reprinted from The Professional Skier. All copyrights apply. Please see our copyright and disclaimer notice page.

There are some people for whom a familiarity with the new equipment in their chosen field merely earns them the label of "gearhead." There are others, however, whose success ultimately hinges on their knowledge of equipment. As an adaptive ski instructor, you fall into the latter category.

Helping adaptive students achieve their full potential requires an awareness of available technology and the ability to modify equipment to suit the individual skier's needs. This can be a daunting task due to constant advances in the field of adaptive equipment technology. Daunting perhaps, but not impossible. When working with adaptive students, remember that refinements are a way of life-and a way of skiing.

Although general adaptive technology addresses an array of disabilities, this article focuses on developments in equipment for skiers with transtibial (below the knee) amputations, addressing suspension systems and braces that can be used in conjunction with prosthetics. For those who would like more information, there exists within the adaptive community a network of orthotists and prosthetists who can provide professional advice on equipment modification and new technology.

Strengthening Ties That Bind

One of the most important parts of an artificial limb is its suspension, the part of the prosthesis that is attached to the skier. Some of the finest advances in adaptive skiing equipment have occurred recently in prosthesis interfacing, i.e., the point at which the skier's limb joins the prosthesis.

New interfacing technology helps provide suspension and added comfort for its wearer. One example of this is the new Alpha Locking Liner, which features a gel system that protects the limb where it makes contact within the socket of the prosthesis. This and several other new liners buffer external forces, decrease shear forces, and ultimately provide better shock absorption thanks to innovative gel materials that not only cushion the limb but provide a gummy surface that practically adheres the prosthesis to the wearer's skin.

Although it is constantly being refined, interfacing technology sometimes requires additional suspension once the weight and leverages of the prosthesis are changed by attaching ski equipment to the prosthesis. You can help enhance the fit of the prosthesis by adding a neoprene or latex suspension sleeve, an elastic device designed to slide over and cling to both the prosthesis and the skier's thigh. For more demanding activities such as racing, you can outfit a skier with a waist belt to transfer the weight of the ski, boot, and binding from the residual limb to the waist. A suspension sleeve and a waist belt can be used in conjunction with a standard "walking" prosthesis (photo 1), but if further enhancement is necessary, the next step might be to look into what is called a sport-specific prosthesis, a subject discussed later in this article.

Photo 1: The prosthesis on the right side of the photo features both a waist belt and a suspension sleeve. The waist belt supports the blue and white strap reaching from the waist to the ankle. The suspension sleeve is the gray material covering the knee area of the prosthesis.

For ski schools, the need to carry adaptive equipment will depend on the number of adaptive skiers the program hosts each year. If the school deals with only a handful of students per season, the bare essentials in this case would include a suspension sleeve and a standard waist belt. (Since a new student might arrive for class with nothing more than a locking device to hold the prosthesis to the residual limb, a suspension sleeve and a waist belt would be two invaluable pieces of equipment to have around.) However, if the school has an adaptive program that serves a significant number of adaptive skiers each year, it might be wise for management to work with regional orthotists and prosthetists to set up an ongoing program for modifying student equipment.

Braces Upgrade Componentry

Suspension sleeves and waist belts work well for individuals who use walking prosthetics and ski infrequently. However, when dealing with students who plan to make skiing part of their routine, you should be aware of the benefits of a custom-made orthotic brace system that attaches to the thigh and transfers the weight of the ski, boot, and binding to the upper part of the body.

In the past, leg braces promoted an upright stance that diminished the disabled skier's ability to perform subtle pressure-control movements. Today, advancements in materials have contributed to the development of lightweight and resilient braces that allow the skier to flex forward in the ski boot, thus placing his or her weight more forward on the ski. These new braces allow disabled skiers to more closely imitate the movements of their non-disabled counterparts.

In addition to improving weight distribution, new brace technology can stabilize a skier's anatomical knee and provide extra support to an amputee wearing a transtibial walking prosthesis. With the help of multi-axial knee hinges that imitate the movements of an anatomical knee, the latest braces bridge the skier's residual leg and the prosthesis to provide enhanced strength and rigidity on either side of the joint. A certified orthotist can easily modify the braces to suit and improve an individual's stance and stability.

The effort to stabilize the knee joint through brace design is ongoing, and the variety of manufacturers offering this technology are constantly working on its refinement. When selecting a brace, the skier needs to consider his or her level of activity and the range of activities he or she expects to perform. If the individual decides to use a brace, it is important to have the skier consult with a professional who deals with prosthetics or orthotics to help find the brace that works best for his or her level of skill.

Sometimes You Make Do

Despite recent advances in adaptive technology, purchasing or procuring new equipment is not always an option for your students. Therefore, you must exercise resourcefulness by modifying an existing prosthesis to optimize the skier's physical performance. One of the least expensive and most common adaptations involves coupling a transtibial prosthesis with a regular ski boot.

Since the "foot" of a standard walking prosthesis is aligned at approximately a 90-degree angle to its "ankle," a transtibial adaptive skier automatically has a problem: the average ski boot has a forward lean built into its design. A simple solution to this problem is to put a wedge in the heel section of the boot to angle the prosthesis forward as it rests inside the boot. A wedge can be a simple adaptation made from dense foam, compact cardboard, or wood - any material that can be shaped easily and that will offer firm support.

Wedging allows the skier's weight to be directed over the ball of the prosthetic foot (photos 2 and 3). The alteration may cause the skier's body to be slightly shorter on the side opposite the prosthesis, but this can be corrected by placing a lift under the corresponding boot to balance the overall stance.

Depending on the need, you can adjust the skier's stance in the ski boot with either a heel wedge or a full-length lift. The best way to determine if the wedge is the right size is to ask the skier if he or she feels a height discrepancy between one leg and the other.

When fitting a ski boot to a prosthesis, make sure there is solid contact with the boot's shin and calf sections. If the space between the boot and prosthesis is too great, you can make up the difference by wrapping the prosthesis tightly with a towel (or any firm cloth material that is handy) and duct tape before having the skier insert it into the boot. When the prosthesis fits snugly inside the boot, the skier's weight can be more evenly centered over the skis.

After you've made all the alterations, the final test is to observe the combination of the prosthesis, the boot, and the ski working together in the snow. Once the skier is out on the hill, it is vital that you make sure his or her skis are tracking properly.

The alignment of the prosthesis may create an insufficient or perhaps excessive amount of canting, and this should be evident in a straight run. If this is the case, the student will be able to feet the ski pull on the inside edge or turn out on the outside edge, depending on the mis-alignment of the ski. Along these lines, canting problems will also be evident from a quick look at the skier's tracks in the snow.

The easiest way to adjust the canting for an adaptive skier is to outfit the skier in boots with a built-in canting adjustment. By doing so, you can adjust the canting just as you would for a non-adaptive skier.

Get Specific

For an individual who plans to spend a lot of time on the hill, or who even plans to do some ski racing, the recommended upgrade in equipment shifts from the aforementioned alterations for a walking prosthesis to the purchase of a sport-specific prosthesis.

To cite an example of how prosthetic upgrades progress, we can refer to a client who started his skiing career using a suspension sleeve on a walking prosthesis modified with a heel wedge placed inside a standard boot. Although the individual skied only three or four times a year, on those few occasions he always had the feeling he was going to come out of his prosthesis while skiing. Adding a waist belt dramatically bolstered the skier's confidence on the hill, and his skiing skills increased accordingly. If the same skier wants to ski more days per year, improve his skills, and even engage in competition, the next step will be to fit him with a sport-specific prosthesis.

Sport-specific prosthetics provide an easy, albeit more costly, way to avoid the majority of adjustments and alterations and to attain a more permanent solution to many standard adaptive problems. Taking into account alignment considerations, the sport-specific prosthesis is made-to-order, fits into a regular ski boot, and incorporates precisely crafted dimensions that typically preclude problems involving canting, wedge use, and boot fit. Such a prosthesis can be customized for flex to allow both the artificial and the regular limb to respond in kind, helping to provide equal weight distribution over both skis.

Conclusion

Any article discussing orthotic and prosthetic devices and their uses can cover only a fraction of the information currently available. If you want the scope on the latest equipment to help your students, you can talk to orthotists and prosthetists who have spent years dealing with the equipment and who know where that equipment is headed.

And when you need advice on making equipment modifications to accommodate students' needs, these again are the professionals to consult. Getting a certified orthotist or prosthetist involved in your teaching program can be highly beneficial for instructors and students.

Bob Emerson is a prosthetics practitioner assistant and a former member of the U.S. Disabled Ski Team (1985-91) who competed in the 1988 Paralympics in Calgary. He is currently working on a bachelor's degree in prosthetics. For more information on the subject, Emerson can be reached by e-mail at NexStep@juno.com.

Matthew Albuquerque is a certified orthotist and prosthetist and is the owner of Next Step Orthotics and Prosthetics in Bedford, New Hampshire.