RESEARCH - Electronic knee in first patient provides wealth of data

[Guest guest]

Electronic knee in first patient provides wealth of data

Rheumawire

Feb 25, 2005

Zosia Chustecka

Washington DC - The first patient implanted with an " electronic knee " is

providing data that will be invaluable for improving orthopedic care in the

future, but it has already led the surgeon involved in developing the device

to change the advice he gives to patients after knee-replacement surgery. " I

allow my patients to do a lot more much sooner, " says Dr Clifford Colwell

(Shiley Center for Orthopedic Research and Education [sCORE] at Scripps

Clinic, La Jolla, CA). " I also urge them to get a bicycle, because we have

shown that cycling results in a lot less force being placed on the knee than

walking. "

The device has also provided information on how the forces in the knee

change when the patient wears a knee brace or orthotics placed in the shoe,

and although the data are preliminary and from only 1 patient, Colwell is

dismissive of both devices. The knee brace alters the forces only in the

very short term, he says: " After an hour or 2, the muscles adapt and the

brace doesn't unload anywhere near as much as the manufacturers say. " As for

orthotics placed in the shoe, which are promoted for patients with knee

osteoarthritis, " if you're trying to change the forces in the knee with one

of these, you're wasting your time. "

Colwell was speaking at the American Academy of Orthopaedic Surgeons 2005

meeting, at an official media briefing; the new device was also presented in

poster session in the scientific exhibition of the meeting.

The E-knee

Nicknamed the E-knee, the novel device is exactly like a standard

knee-replacement implant, with 1 differencethe sophisticated electronics in

the stem, including an antenna that transmits information on the forces that

the knee is being subjected to. It's the result of a 13-year collaboration

between the Scripps researchers and several companiesDepuy (Warsaw, IN) for

the implant, NK Biotechnology (Minneapolis, MN) for the transducers, and

Microstrain (Williston, VT) for the electronics. When the device was ready

for implantation into a patient, there were plenty of volunteers, research

fellow Dr Shantanu Patil (SCORE) told rheumawire, even though the patient

would stand to gain nothing extra from having this devicethe benefits all

lie in the future, for the patients who will eventually get better care as a

result of the information that is collected.

The patient who received the first E-knee was Jerry Ward, an active retired

engineer with severe arthritis, who had already had a previous knee

replacement in his other knee, as well as a total hip replacement (both

carried out by Colwell). He was chosen because of his physical build, his

active lifestyle, and his willingness to contribute to advancing orthopedic

care, Colwell commented. The E-knee was implanted a year ago.

In a video, Ward describes himself as a " lab rat " and says the prospect of

taking part in this experiment was " very intriguing to me. . . . I do

understand what they are trying to do and I'm sympathetic to it, anyone who

has 3 implants should know something about them, and this offers me a way of

finding outit offers a window on a new world. "

The E-knee offers, for the first time, information on the forces that are at

work in the knee during different activitieseg, walking, climbing stairs,

etc. " This is something that we could only guess at before, using

mathematical models, " Colwell explained. He was surprised by how much these

models overestimated the forces involved. For instance, the computer models

calculated that climbing stairs generated high peaks reaching 5.4 times the

patient's body weight, while walking was 3.1 times, whereas the E-knee has

shown that the actual forces involved are 2.5 times body weight for climbing

stairs and 2.2 times while walking.

" We now have a means of knowing exactly where stress is being placed on the

knee every time the patient engages in any type of activity, " says Colwell.

He believes that this information will lead, eventually, to improvements in

the design of knee implants and can foresee implants being customized to the

specific needs of certain patients. " For example, we could end up with 1

type of knee for golfers and another for skiers. " As people are living

longer and are more active in their twilight years, there are increasing

demands being made on these devices, and " we need to ensure that the

implants we are fitting can cope with these demands, and also that they

survive. " At present, a knee implant is expected to last around 14 to 17

years, he added. His team plans to implant another 6 E-knees into a range of

patients, including some who are younger and some who are overweight. The

device is being produced for research purposes only; it will never be

commercially available.

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org