Prosthetic Knees

Two new variations using contemporary prosthetic knee technology caught my eye. The first is an interesting-looking polycentric knee with pneumatic swing phase control from Otto Bock. Available in both knee disarticulation and familiar pyramid-connection versions, this latest hybrid design is a bit reminiscent of the children's polycentric knee they introduced last year. It is restricted to Red Class loading not to exceed 75 k or 165 pounds so that will limit applicability in the USA.

The second knee of note was the prototype shown at the Biedemann-Motech booth. This is a microprocessor-controlled hydraulic knee offering both stance and swing phase control, using a magneto-rheologic fluid cylinder from the Lord Corporation in place of a conventional hydraulic damper. The patient models walked well, both on level ground as well as down slopes and stairs. In a brief presentation about the knee, Herr Bidermann noted that it has integrated knee angle and forces sensors but said that the resistance pattern differs from that of the C-Leg.

The Bidermann knee seems to be similar to a virtual Total Knee in that it is programmed to lock the knee hydraulically for a few microseconds at Initial Contact, whereas the C-Leg has a fixed yielding rate making it more like a virtual SNS knee. One other distinction is that the Bidermann knee has all the sensors inside the frame so it may be used with any available ankle-foot mechanism while the C-Leg is restricted to four alternatives from Otto Bock.

As the Blatchford distributor in Germany, Bidermann also showed the Endolite Adaptive Knee but this microprocessor-controlled SNS knee still seems to be in the pre-production phase. The external appearance is sleeker than it was at the ISPO meeting in Amsterdam, so hopefully this will become a commercially available alternative one of these days. In any event, it now seems quite clear that the first decade of this millennium will be characterized by the release of a flurry of microprocessor-controlled lower limb and upper limb devices, reminiscent of the explosion of dynamic response feet 15 years ago.

College Park introduced the use of prefab cast-walkers with their foot attached underneath so non-amputees could get a "feel" for how their foot worked by walking on a pair. This has been popular with attendees over the years, so Flex-Foot and others now have similar psuedo-transtibial prostheses available.

At the Bidermann booth, I saw the next logical extension of this trend: a psuedo-knee disarticulation prosthesis to allow trial walking with prosthetic knees too. Actually, it is simply an adaptation of the historic "bent knee" design that has been used for centuries when advanced prosthetic care is unavailable.

Reader Comments: Read all user comments hydraulic knee joint In the past I have worn KAFO's because of instability of my joints due to having a rare connective tissue disorder. These were custom made, and of the 'cosmetic' plastic style. This year I had major spinal surgery that led to damage to ... read more - Fiona   6/15/2005 Re: hydraulic knee joint Without knowing a great deal more about the details of your physical condition, it will not be possible to make any detailed recommendations, although there are a number of developments in KAFO design in the past decade or so, including the... read more - John Michael   10/22/2005 Re: hydraulic knee joint hi i am mohanagandhi,Prosthetist Orthotist ,doing my practice in india (Hyderabad,my Mobile Numbers 9885349838,9885454003,9440054332) i got what u r aiming for ,that is u need some external assistance device which can help you to push... read more - G.Mohanagandhi   10/22/2005 polycentric knee joints Hi, I'm trying to find information about reverse engineering of a polycentric knee joint for above knee amputees. I'm trying to take the centrode first and then build the bar system around it. Does anyone know if this has been tried before ... read more - R. Vegter   5/27/2005 Re: polycentric knee joints Although I'm not an engineer, I believe this is an interative process. Some years ago, Professor Radcliffe demonstrated a simple program he had written that allowed him to specify different link geometries which produced animations of the ... read more - John Michael   5/31/2005 virtual prototyping of human limbs using reverse engineering I am mechanical engineer and am a Lecturer at BIRLA INSTITUTE OF TECHNOLOGY RANCHI .I am doing my phd in the area of reverse engineering for the development and protyping human limbs which would be an aid for the surgeons as well as the doc... read more - Richa pandey   9/2/2003 Basics of CAD in regards to socket design for trans-femoral amputees Hi! I'm a college senior(Mechanical Engineering) in India, and am planning to do my Master's in Biomechanics. Could you suggest me a few good web-sites and other related material to understand the basics of mechanics for lower-extremity pro... read more - Manish Virmani   1/9/2003 Re: Basics of CAD in regards to socket design for trans-femoral amputees This is a complex area that is not discussed in any depth on the web, to the best of my knowledge. There are a number of texts that provide entry-level information on both biomechanics and socket design concepts. You're probably best advi... read more - John Michael   1/9/2003 trans-tibial amputee orthoses Hi, I am a physiotherapist working in Australia. I have a patient case study to perform on a 67 year old female with sero-positive RA for 50 years who had a trans-tibial amputation due to gangrene. A) What prosthesis would be BEST su... read more - Melissa McSwan   4/30/2001 Re: trans-tibial amputee orthoses orthosis u approch donjoy company based at US for prosthesis u prefer to go with the folowing components ,1.fixed ankle joint ,2.sach foot,2.silicone suspension sleeve 3.graplite pylon - G.Mohanagandhi   10/22/2005 amputee cyclists Hi - I am looking for information on the different types of prosthetic limbs (trans-tibial and trans-femoral) being used by amputee cyclists. The various knee and other components involved interest me, as do the alterations being made to th... read more - Jennie Jackson   3/18/2001 mountain climber amputee Hello, I hope you can help me; my son is looking for the name of a man who, he believes, climbed Mount McKinley and is a double amputee. He has an assignment to write about someone who has overcome adversity and he had seen a documentar... read more - P. Mayes   3/2/2001 Re: mountain climber amputee You may have already gotten your answer (it is probably too late anyway), but I think the person you are asking about is Ed Hommer. He wrote a book about his life called "The Hill". He also has a web page at www.everestquest.com, which ha... read more - Tim Griffith   6/14/2002 Can you help me? hi sir, I'm from Türkey (Adapazar ) and I'm a student in univercity as you know Adapazar saw an earthquake last year and we can not find books as well as before it my teacher gave me a duty about "electro- and magneto- rheologic fluid... read more - Tolga Ozturk   2/14/2001 Procedure code language John, Give me more time to send you the document as I am taking the L-code course next week. thanks , rick - Rick Lehneis   8/30/2000 Procedure codes & Network or Organization Registration John, May Lehneis O & P also be listed as an organization or network as Actra Has? I have sent a HCFA Orthotic language proposal to David Schultz which is now near complete. Would you care to view it's content and advise me? Thanks, Rick Le... read more - lehneis   8/7/2000