According to a recent report published in Circulation, obesity has increased during the last 2 decades, with 154.7 million Americans aged 20 years and older being reported as overweight or obese and 78.4 million as obese. Another report published by Jason T. Kahle, CPO, LPO and colleagues in 2008 revealed, from 1960 to 2008, the average weight increased from 160 pounds to 191 pounds for American men and from 140 pounds to 164 pounds for American women. Weight gain also afflicts the amputee population and has created new challenges for practitioners.
“If you remove the idea that the patient is going to use an artificial limb or brace and just look at obesity and the challenges that obese patients face, I think the challenges are similar between them with some added challenges for someone that uses assistive technology,” M. Jason Highsmith, PT, DPT, PhD, CP, FAAOP, assistant professor and co-director for the Center of Neuromusculoskeletal Research at the School of Physical Therapy & Rehabilitation Sciences from the University of South Florida Morsani College of Medicine, told O&P Business News. “With folks who are obese who don’t use the technology, you are talking about everything from a social stigma to increased health challenges in terms of higher likelihood of joint degeneration in earlier years than folks who are not obese, more cardiovascular diseases, some skin conditions and things like that. When you consider the patients who use assistive technology you start adding other problems, like fewer component options.”
Challenges in manufacturing
About 10 years ago, the standard for weight limits on lower limb prostheses was rated between 200 and 250 pounds. However, the standards have increased since then, and manufacturers now receive requests for weight limits even higher than the new standard.
“The testing standards for product testing were originally based on 220 pounds, but that is not adequate anymore,” Michael Link, CP, vice president of College Park, told O&P Business News. “Over the years [the requested weight limit] has been bumped up; most people want a weight limit of 250 pounds, then 275 pounds, then 300 pounds and now I think the desired weight limit is in the 300- to 325-pound range.”
In addition to ensuring a prosthesis is safe and functional, one of the biggest challenges in manufacturing is finding the right materials to use when making lower limb prostheses for obese patients. Although aluminum may be a good material for a patient of normal weight, it may not be durable enough for a heavier patient, so manufacturers may opt to use titanium or stainless steel instead, which is more durable but also more expensive.
“When you are looking at higher weight componentry you typically have to evaluate materials first,” Jeff Doddroe, new product development director at WillowWood, said. “Production can be similar, the process can be similar, but it is usually overall cost and time that can increase on the higher weight components.”
Components for obese patients are often not covered under warranty because they usually do not pass ISO testing standards, which is indiscriminate to the weight of different patients.
“[College Park has] a couple of designs where there is a heavy-duty version, but that is not a equitable solution because there is no reimbursement for overweight limit components,” Link said. “We could warranty to something higher, but we don’t think that is a safe approach so we are hitting the limits of what we can do as long as we want to continue to have the validation testing to back us up. There have been attempts to get coding for heavier weight feet, but it has been shot down so we are stuck without the ability to have a market that is willing to pay for the needs.”
According to Doddroe, research on prostheses for overweight and obese patients could help improve the design for lower limb prostheses.
“Right now all of our products we sell are tested to ISO standards and those standards are established up to 125 kilograms. Beyond that we have to extrapolate the loading conditions for those tests vs. relying on actual patient data that had been collected over the years,” he said. “So we extrapolate with a fair safety factor to compensate for the unknown. If the research was done and we had better information, I think the componentry could be better optimized.”
“That 500-pound person is equally as important as the person who is 120 pounds. That person deserves to get up and walk,” Kevin Carroll, MS, CP, FAAOP, vice president of prosthetics, Hanger Clinic, said. “It is a lot more difficult for us to build those types of prosthetic systems and to get that person up, but when we do it makes a big difference in their life. Often they are in a nursing home and if we can get them up and moving and walking they may be able to go home.”
Cardiovascular disease is a significant threat for obese amputees. In a study published in the Journal of Prosthetics and Orthotics in 2000, results identified four highly prevalent risk factors for cardiovascular disease in amputees, including high cholesterol, hypertension, diabetes and inactivity. Another study from the Quarterly Journal of Medicine published in 2008 showed insulin resistance, psychological stress and patients’ deviant behaviors “may have systematic consequences on the arterial system and may contribute to the increased cardiovascular morbidity” in traumatic leg amputees. Both proximal leg amputees and bilateral amputees also had a higher risk of cardiovascular disease compared with distal amputees and unilateral amputees, suggesting a link between extent of leg amputation and cardiovascular risk.
The excess weight obese patients carry also can affect their knees, hips and other joints and cause chronic osteoarthritis.
“At the knee there is about three to five times your body weight transmitted, particularly with activities such as going up and down the steps. In the hip it is about one to two times your body weight. For every 10 pounds of weight the patient accumulates in the hip, that can be at least 20 extra pounds across the joint and in the knee that could be as much as 30 to 50 pounds of stress across the joint,” Brian G. Evans, MD, vice chairman of orthopedic surgery at MedStar Georgetown University Hospital, told O&P Business News.
Some challenges for obese patients may not seem significant, when in fact they are. For example, obese patients do not have the same flexibility as patients of a normal weight, which makes it difficult for them to bend over and put on a prosthesis or orthosis, according to Carroll. This problem can be addressed by having someone help the patient put the prosthesis on, but it would be ideal for the patient be able to do that independently so they can live without a caregiver if they choose.
The most important thing for patients who are overweight or obese to do is to lose weight and live a healthy lifestyle, which will expand the options for knee joints and prosthetic feet and legs.
“The simple fact is if obese patients lose weight it is going to be less metabolically taxing for them to move around, to walk, to transfer and all of those things,” Highsmith said. “Second, patients will probably gain access to more component choices that may be better suited for them, as well as general health benefits, which are innumerable.”
According to Evans, losing weight will also help reduce much of the joint pain obese patients experience.
“The patient needs to be advised their body weight is significantly contributing to the pain and the difficulty they have walking and moving,” Evans said. “If you have patients who are much earlier in the arthritic process, losing weight can have a profound impact on how their joints feel and how freely they can move. Once the joint is already to some extent bone on bone or markedly degenerated, weight loss becomes a little less of a positive benefit from a joint perspective, but if they have surgery it can dramatically improve their ability to rehabilitate and then their functional ability after the surgery will be much better.”
Challenges in young patients
Children with lower limb prostheses also experience limited mobility that can affect their health, and finding the right component may be difficult if they are overweight or obese, particularly because they are still growing.
“Children who weigh more than 100 pounds have fewer component options available to them and may require more frequent repairs to their prosthesis due to the extra strain on the components,” Nicole Soltys, CP, clinical coordinator at the Rehabilitation Institute of Chicago Prosthetics & Orthotics Clinical Center, told O&P Business News. “The component industry has developed some knees and feet with higher weight limits for adult patients, but there haven’t been many changes in pediatric components. Most pediatric components carry a weight limit of 100 pounds and a few component lines go up to 132 pounds.”
It may be difficult to fit a comfortable and stable prosthesis for patients with excessive soft tissue, which can inhibit exercise. The same is true in children who require an orthosis, according to Janet Marshall, CPO, of Shriners Hospital for Children, Tampa, Fla. Children with spina bifida are particularly at risk for obesity due to their condition, which confines them to a wheelchair for most of their lives.
“Between the ages of 2 to 8 are the potential years for active walking with the aid of bracing whether it is solid AFOs or up to RGOs, depending on their level of diagnosis,” Marshall told O&P Business News.
However, children who need orthotic support require help from family members or caregivers to apply the orthosis, a walker or canes and physical therapy to instruct proper usage, making orthosis wear challenging and compliance low.
“Due to the stresses that surface from the child resisting this inconvenience, or the family needing to devote extra time for successfully promoting the usage of the braces, often the walking becomes more than can be managed,” Marshall said. “This usually takes place in early adolescence. The change that then occurs is to not walk, stay in the wheelchair for the freedom it allows, and only pursue sedentary activities. The end result is weight gain with no end in sight to reverse the cycle.”
According to Soltys, not only can prosthetists work with the patient’s physician to make a referral to a nutritionist to help balance diet and physical activity, but there are also other resources and programs available to the general public to help maintain a healthy lifestyle.
“As prosthetists, we want all of our patients to live happy, healthy lives,” Soltys said. “Each day, we see firsthand the devastating effects of diabetes, peripheral vascular disease and heart disease in our adult patients. As we enable our pediatric patients to take their first steps, we want to help ensure that their future does not include diabetes and cardiovascular disease.”
Research on obese amputees has not kept pace with this growing patient population, but Highsmith doesn’t think they comprise a disproportionate number of O&P patients.
“I don’t think there has been an overwhelming response to [obese amputees], although it is an increasing problem,” he said. “I think the weight limits [in prosthetics] are increasing a little bit, but I think there is only so much that can be done in a short amount of time. There is probably also not a large demographic of obese amputees. The majority of patients probably fit in another weight category and so [researchers are] probably aiming to where the larger number of people are.”
Highsmith believes future meetings and symposia should help show the problem is more significant than researchers believe, whereas Carroll believes research on new, stronger but lighter materials is warranted for obese patients.
“Heavier-set individuals deserve care and as care providers we are obligated to look after these individuals,” Carroll said. “As a result of that obligation we have to continue to research ways to provide the best and most appropriate quality care to this population.”
Practitioners can rely on one another when they have questions about different component choices and experiences with patients who are overweight or obese.
“We have had colleagues reach out [through a listserv] and ask if we have experience with someone of a certain amputation level that weighs a certain amount,” Highsmith said. “Folks will respond they have had experience with a certain amount of weight, or a certain type of prosthesis worked well on this type of patient and so forth. Networking is a good way to get some immediate feedback.” — by Casey Tingle
Disclosure: Link is employed by College Park. Doddroe is employed by WillowWood. Carroll, Evans, Highsmith, Marshall and Soltys have no relevant financial disclosures.