By Shalmali Pal
After amputation patients and practitioners tend to focus on the affected side. But the intact limb, or “sound side,” is also worth watching as long-term shifts occur in weight distribution between limbs during gait. This stress can often lead to knee osteoarthritis (OA) in the intact limb.
A March 2005 study in the Archives of Physical Medicine & Rehabilitation found that knee OA in war veterans who had undergone transtibial amputation was more than six times more prevalent on the intact side than in the amputated limb.
A proper prosthetic fit is paramount for mitigating OA to the intact limb. Misalignment of the prosthesis can create an artificial leg length discrepancy, which can stress the intact-side knee joint, said Michael Carroll, BSPO, an O&P resident at Hanger Prosthetics & Orthotics in Oklahoma City.
Another risk factor for OA is overuse of the contralateral limb. Patients who aren’t properly trained to use prostheses will often put all their weight on the contralateral side. This problem occurs most often in younger amputees, said Scott Sabolich, CP, of Scott Sabolich Prosthetics & Research in Oklahoma City.
“These [amputees] do a lot of hopping; they do a lot of full load-weighted torquing of the [sound side] ankle or knee,” he explained. “Over time, you’ll see that sound-side knee is often completely shot, the ankle has gone completely flat into eversion, and the arch is on the floor because the foot is overloaded.”
So how can the prosthesis be optimized to reduce potential damage to the intact limb? Carroll and Sabolich agreed that device fit tops the list.
At Hanger, they rely on a check socket system. If the patient is able to walk with the check socket on, Carroll takes the opportunity to assess the gait, looking for vaulting or other gait abnormalities.
“We look to make sure what we’ve done on the prosthetic side isn’t going to negatively impact the contralateral side,” he said.
While that perfect fit can be achieved in the office, maintaining it once the patient leaves is just as important, Sabolich said.
“What happens when the patient walks out the door with that prosthesis, and over time, he gains five pounds?” Sabolich said. “Now, all the pressure points are not going to measure the same. Then the problems start. No one educates patients on how to keep track of the fit. A person can really only go up or down two percent of their body weight before major changes to the prosthesis are required.”
A properly fit prosthesis should benefit both limbs, he added. When patients takes off their prosthesis on one side and the shoe on the other side, there should be no redness, demarcations, blisters, sores, or pain on either side, Sabolich said.
As long as the there is an intimate fit and strong suction between the residual limb and the device, the weight of the prosthesis is less of an issue, even for older amputees, Carroll said. The weight of the device is more a matter of patient perception, i.e., the prosthetic side “feels” heavier than the intact side because manipulation doesn’t come naturally.
For that, Carroll and Sabolich also agreed that amputees must undergo training on two fronts: Using their prosthetic limb and avoiding misuse of the intact limb. Sabolich said traditional physical therapy may not be enough.
“We recommend amputee gait therapy, but people don’t really go through that. They just go through PT and rehab. Often, they don’t even wear the prosthesis while doing PT,” Sabolich said.
Amputee gait training also allows practitioners to ensure prosthetic alignment is maintained dynamically.
“We have the textbook definition of appropriate rotation of the foot, but once the patient starts to use the prosthesis, we might discover that alignment isn’t right for him,” Carroll said.
Sabolich recommended the practitioner pretend the patient has no extremities at all.
“Watch the head, torso, and pelvis,” he said. “We want [those parts] in a straight line. Does that patient walk like a nonamputee? If he doesn’t, how can we fix the prosthesis to make that happen?”