Saturday, May 28, 2022

Best Knee Unit to use?

Dear Colleagues:

This is yet another subject of controversy. Clearly another major knee

seminar is needed to discuss

“Which Knee to Use When,

and What Knees Would We Like to see Developed.”

It seems to be good bet to use a knee with a SNS hydraulic unit when and if

you can. However, we don’t get the benefit of 4 bar geometry for toe

clearance and higher center of virtual rotation-

There is one endoskeletal knee frame built by USMC and sold by Mauch

(Flex-Mauch) which has a SNS unit in it. This frame has considerable

limitations I am told.

In the last 3 years, I have asked manufacturers why they haven’t come out

with an improved 4 bar knee with a SNS unit. The consistent answer has been

“difficult engineering problems”

It has now come to my attention that Sujatha Srinivasan , while a graduate

student at the University of Toledo (OHIO), has developed a 4 bar knee with a

SNS unit. This was done under the guidance of

Dr. Steven Kramer a UT professor of Mechanical Industrial Engineering

and in conjunction with Vern Swanson, a creative prosthetist and President

of Swanson Regional Orthotic and Prosthetic Research Center

(an amputee himself).

It is my understanding that more research dollars may be needed to truly

bring this knee unit to market. It is also a possibility that this important

contribution may be languishing for lack of continued focus by the patent

holders. Sujatha is not currently involved in its continuing development

because of possible conflict of interest with her current employer.

I would like to recommend that we, as prosthetists, give our support and

encouragement to Sujatha Srinivasan, Vern Swanson, and Steven Kramer,

to continue with the development of this promising knee.

What I would ALSO like to see, is a weight-activated-stance-control

four-bar knee for patients who, for reasons of funding, activity level, or

need for reducing componentry weight, would prohibit the use of a SNS unit.

Engineering students-Prosthetist Engineers, this is another opportunity.

BTW, My awareness of this new knee comes from an article in the UT Alumni

Magazine. It was given to me by a local colleague who received it from one of

his clients. It seems like something we should have seen in one of our



Mark Benveniste CP

VA Med. Ctr. Houston TX


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