We’ve come a long way, baby. From the archetypal wooden leg of assailing pirates to the sci-fi wonder of the Six Million Dollar Man, the art of prostheses has found a middle ground where functionality meets just the right mix of technological genius. Such are the wonders of today’s prosthetic appendages that athletes not only compete in elite sports such as triathlons and track and field races, they set world records. Today’s prosthetics are lighter weight, more agile and more personal, with such features as tattoos.

But still the industry that addresses amputations remains somewhat of a mystery to many. For example, how prevalent is amputation in our more advanced culture? What are the clinical considerations for treating patients with amputations? And just where does mobility equipment fit into the equation?

To find the answers to these questions and more, Mobility Management went directly to the experts.

Amputations on the Rise

Believe it or not, amputations are actually more prevalent in today’s society than in years past. The reason? Chalk another one up to the obesity epidemic.

“Right now, in the U.S., about 50 percent of all amputations are due to vascular problems,” says Scott Cummings, past president of the American Academy of Orthotists and Prosthetists, a member of the Amputee Coalition’s scientific and medical advisory committee and a certified prosthetist at Next Step O&P in Manchester, N.H. “And most of those are related to diabetes. We have an obesity epidemic in this country, and with it are projections to have an increase in diabetes-related amputations.”

Of course there are other reasons for amputations, Cummings says. The other two main categories are traumatic injury (think war-time injuries and car accidents) and congenital defects.

According to the Amputee Coalition, a Knoxville, Tenn.-based national nonprofit organization that provides education, support and advocacy for limb loss, nearly 2 million people in the United States have limb loss. Vascular diseases such as diabetes and peripheral arterial disease account for 54 percent of those amputations, and trauma accounts for 45 percent.

Constructing the Prosthetic

The time between suture removal after surgery to remove a limb to the time of a prosthetic fitting is generally three to six weeks. The first prosthesis or socket (the part that the residual limb fits into) is prefabricated and then fitted to the patient.

“The new amputee can’t tolerate full weight bearing because he hasn’t healed up enough,” Cummings explains. “The concept with the custom fitted is there’s a lot of swelling in the residual limb, and the residual limb isn’t going to be full weight bearing so that the fit doesn’t have to be as perfect for the first several weeks. And so, some doctors and prosthetists feel it’s more important to get them up right away and get them walking with something.”

That something is called an IPOP or immediate post-op prosthesis or preparatory prosthesis.

After a few weeks — after the swelling has gone down, drains have been removed and the dressings are reduced — the prosthetist can get a better idea of the bony anatomy of the residual limb. At that point, the prosthetist will take a negative impression of the limb to make a custom socket, also called the definitive socket.

The size and shape of the residual limb will change dramatically over the first 18 months after amputation because of muscle atrophy. Therefore, the prosthetist will need to replace the socket to accommodate those changes.

“When somebody has a residual limb, there is an element of almost shaping, for lack of a better word, that has to happen,” explains Allison Gurwitz, OTR/L, ATP, at University of Maryland Medical System’s Kernan Orthopaedics and Rehabilitation in Baltimore, Md. “A lot of times there’s a lot of fine tuning and revisions to the prosthesis to make sure it’s fitting properly.”

The user’s improvement with the use of the prosthesis could also mean that a better fit is needed.

“These people are getting more active, more weight bearing, more wearing time, and we expect the fit will need to be better as they progress functionally,” he says. “So it’s important to maintain a really good fit.”

A good indication that a new socket is needed is that the patient is “thumping” around on the prosthesis, Cummings says. In fact, the prosthetist might do three sockets in the first two years. Then the fittings can be reduced to every three years and sometimes longer.

Oftentimes, a wheelchair is critical aft er surgery, especially for people with diabetes.

“If I have an amputation of one leg because of vascular disease or diabetes, the other leg is at what we consider a very high risk for a future amputation. I think like 50 percent of people have their other leg amputated within five years. So you’re trying to do everything and anything to preserve that other leg,” says Maria Lucas, PT, DPT, the clinical coordinator of the Amputee Program and coordinator for Professional Development and Education at MossRehab Hospital in Elkins Park, Pa. “I generally don’t recommend that the patients hop around or use a walker any more than they absolutely need to. They should use their wheelchair for the majority of their mobility until they get their prosthesis in order to preserve the other limb.”

Of course, Lucas says, that wouldn’t apply to someone with a traumatic amputation because the other limb is not at risk.

The other thing to keep in mind is that oft entimes at the in-patient rehab level, the patient and team might not be ready to make a determination of whether someone will need a wheelchair for the long term,
Gurwitz says.

Mobility Equipment Matters

Although a person with an amputation is generally given a manual wheelchair initially, not all of these patients stay in one.

Generally if a prosthetist is meeting with an amputee, it’s because that person is itching to get out of a wheelchair.

“I’ll be evaluating a person with an amputation, and I’ll ask, ‘What are your goals?’ And they’re sitting there in the wheelchair, and they’ll tap on the handrails and say, ‘I want to get out of this wheelchair,’” Cummings says. “Their life before the amputation didn’t include the use of a wheelchair, so they’re trying to get back to how they were before.”

Still there is a fair number of people who opt to use both a prosthesis and a wheelchair, especially when they are still building strength, balance, stability and endurance with the prosthesis.

Cummings says it’s not uncommon for an amputee to take a wheelchair to a shopping mall to use between stores, but get up and walk the short distances between the aisles, for example.

“I will tell you that there’s a difference between the average below-the-knee amputee and the average above-the-knee amputee in the amount of energy expenditure to walk, resulting in the below-the-knee level having a better chance of being ambulatory than the above-the-knee amputees,” he says.

That has a lot to do with the fact that much more energy is needed to use an above-the-knee prosthesis. For that reason, Cummings says it’s more common for above-the-knee amputees to decide to use a wheelchair.

Among patients with traumatic amputations or blast-related amputations, that practice holds true. Dr. Heather L. Asthagiri, staff physician in the Physical Medicine and Rehabilitation Services Department of Orthopaedics and Rehabilitation at Walter Reed National Military Medical Center in Bethesda, Md., says usually patients with bilateral lower-extremity and proximate bilateral lower-extremity amputations are more likely to use a wheelchair.

On the other end of the spectrum are elderly patients with comorbidities. Lucas says these patients are far more likely to continue to use a wheelchair even after being fitted with a prosthesis, which has a lot to do with energy expenditure.

“The vast majority of people with amputation are elderly patients with vascular disease and diabetes, so most of them are in their 60s or 70s. A lot of them will need the wheelchair for the times when they don’t have their prosthesis on. They wake up in the middle of the night and have to go to the bathroom; they’d use the wheelchair,” Lucas says.

A wheelchair is also used by people who have cardiac problems and underlying renal disease and diabetes, she says.

“In reality, sometimes you’ll find patients that they’ve always said they really want to walk, but when they get down to it, it’s much more difficult. There’s definitely a significant increase in energy demand to walk with a prosthesis vs. not having a prosthesis,” Lucas says. “If you lay that on top of them being medically sick and having cardiac problems, a lot of times, although they want to walk, they’re limited somewhat by their endurance.”

Gurwitz says the wheelchair can play an important role in energy conservation. Yes, a person might have the energy to use a prosthesis, but will that same person still have energy left to take a shower?

Gurwitz says there are a variety of considerations to determine whether someone will need a wheelchair long term. These factors include:

• Age
• Comorbidities/medical history
• Cardiovascular tolerance
• Skin integrity and circulation (Is the patient at risk for wound development with the prosthesis?)
• Upper-body strength
• Condition or strength of the intact leg
• Fitness level
• Body weight and body type.

For example, “if somebody is morbidly obese, they just may not have as easy an ability to be mobile in general,” Gurwitz explains.

Anatomy of the Chair

When fitting someone into a wheelchair, there are several important clinical considerations that are different for people with amputations versus those with other mobility conditions.

For starters, center of gravity is a major issue, especially for bilateral lower-limb amputations.

“If you amputate someone’s leg, that moves the center of gravity higher, and that can be a problem in a wheelchair,” says Cummings, who frequently sees anti-tip bars installed to prevent tipping. “If you remove 20 percent of their body weight at their legs, now the center of gravity instead of being down near the hips is up closer to their chest wall. That makes them more tippy, especially going up a hill.”

Gurwitz likens the experience to sitting on an exercise ball. If you have too much weight behind the ball, the body will tip backward, and if you have too much weight on the front of the ball, the body will fall forward. She says to think of the wheels of the wheelchair as the ball. To give someone stability, you have to position them just right to prevent that tipping.

The usual method for adjusting center of gravity for amputees is to move the axle plates on the chair, Gurwitz says, and some wheelchairs even come with something called an amputee axle that extends the back of the chair to put the wheels farther back.

Gurwitz says that when she’s fitting an amputee into a manual chair, she looks mostly at the ultralightweight variety. Weight of the chair is definitely a consideration, but mostly she’s looking for the adjustability of that axle. Gurwitz says most of the ultralightweight chairs can be adjusted up and down as well as forward and backward, and that allows her to get the right adjustment for center of gravity.

In fact, when making adjustments to the chair, Gurwitz oft en considers the difference in seat height. She might, for example, make the back of the seat lower than the front of the seat so that the seat is sloped to give the user a better biomechanical advantage. For someone who has had a stroke and an amputation and might only have the use of one hand and one foot, she might also consider hemi height so that the seat is low enough for the person to push with the foot and propel with the hand.

Of course, there are drawbacks to these adjustments. For one, a low seat height could interfere with transferring.

“Things that are low are tougher to get up from than things that are higher,” Gurwitz says.

Also, the unfortunate side effect of moving the axle plates is that doing so can interfere with the patient’s ability to propel the chair.

“If I’m a bilateral and my center mass is too far posterior and I have to move the axle plates back to accommodate for that, what it really does is it makes propelling a little bit harder because now the actual handrims are more behind you. So you’re going to have to reach back for the arms to selfpropel,” Lucas says. “Then they also oftentimes have a lot of shoulder problems because they’re diabetic and they’re very at risk for rotator cuff injuries.”

For power wheelchairs, adjustments have a lot to do with whether the chair is rear-wheel, front-wheel or mid-wheel drive. And because the seating system is sliding along the base, “a couple of inches can make a tremendous difference to find that stability,” Gurwitz says.

Power chairs are not often prescribed for people with amputations.

“I have gotten power wheelchairs for people with amputations — it’s obviously a case by case basis — but it’s usually because there’s something that is preventing them from being a functional manual wheelchair user, even with that ultralightweight adjustable frame,” Gurwitz explains.

She describes a patient who was 6 feet tall and weighed more than 400 pounds. Gurwitz says this woman didn’t have the stamina needed to propel a manual chair.

“What I actually did was I had her push a wheelchair around in a loop … and timed it. And I basically went to the insurance company and said, ‘That is not a functional amount of time to be able to go that amount of feet,’” Gurwitz says.

For patients with comorbidities such as stroke or cardiac issues or those with an upper-extremity amputation in addition to a lower extremity amputation, a power chair might be the right call.

A Positioning Plan

The prosthesis can affect a wheelchair’s seating and positioning.

“We need to take into consideration whether they’re going to have a prosthesis on or off; that might affect the seat cushion decision,” Gurwitz says.

For example, one of the most important wheelchair additions, especially for new amputees, is an elevated legrest to prevent the residual limb from hanging, especially if the patient will not be wearing the prosthesis in the chair.

“Fluid builds up in there, and it can cause swelling,” Cummings says. “So the legrest is actually elevated, and sometimes an extension between the seat and the elevated legrest is utilized to help hold that leg up horizontal with the floor.”

Lucas says it’s extremely important to install a limb support to prevent knee contractures. If the knee gets bent in a flexed position, it will no longer fully straighten, she explains.

“Many of the legrests don’t accommodate for that because even if they lift the legrest all the way, their knee will still be partially bent when they rest it on there. So we recommend that they use a stump support… The problem we run into is that once the insurance pays for a stump support, they don’t want to pay for a regular footplate,” Lucas says. “So sometimes you just have to adjust — make a regular elevating legrest and make some modifications to it to support the limb with the knee in extension when they don’t have their prosthesis on.”

When considering the seating system, Lucas says the seating surface, as with most wheelchair users, plays an important role for amputees. “It’s not as critical as say someone who is spinal cord (injured) because obviously the person with an amputation has no paralysis. So they’re moving around; they’re doing weight shift s all the time.”

However, there are some types of amputations that require a little more TLC, namely hip disarticulation amputations.

“That means that their limb is actually disarticulated at the level of their hip joint and all that remains is their pelvis on that side,” Lucas says. “What that really does is make their seating surface unequal, and so you’ll have to modify the seating surface in some way to make their pelvis sit level — that way you don’t develop any kind of scoliosis of their spine.”

At Walter Reed, Asthagiri says a rigid backrest is frequently ordered for wheelchairs, specifically because “posture is often affected with very proximal lower-extremity amputations.”

Another consideration that is somewhat unique among blast-related amputations is the need for multiple surgeries, which can affect seating needs.

“Our wounded warriors are oft en revisiting the surgical suite for heterotopic ossification (development of bone in abnormal areas) removal, which if in the pelvic/sitting area, can change cushion needs,” Asthagiri says.

Also Gurwitz says a specialty back cushion can be helpful to aid with the adjustment of center of gravity.

“Maybe I’m going to mount it a little bit in front of the back handles as opposed to flush just so that their body weight is more in front to give them a little bit more center of gravity,” she explains.