American Orthotic & Prosthetic Association Assembly 2005

As noted previously, the 2005 Assembly in Las Vegas was the best-attended AOPA national meeting in history. Due to the concurrent session structure, only those talks I was able to attend are highlighted here.

Scientific Sessions - Part Three

One of the best attended, and one of the most interesting sessions, was the one on Future Trends in Technology. Several of these speakers were new to P&O programs but provided very intriguing insights into what the coming decades may reveal.

Kim DeRoy, RPT elaborated on some of the plans OSSUR has to integrate several technological advances into "bionic" limbs of the future. Their vision is that osseointegrated connection to bone will replace today's sockets & suspensions while directly neural control will provide direct operation of multifunctional, powered components much more easily than today's crude control of simple, passive components.

Homayoon Kazerooni PhD reported on several projects from his team at the University of California, Berkeley that are directly related to O&P needs. For example, his researchers previously developed a type of "power glove" that has been successfully commercialized to permit workers to safely handle very heavy objects in industrial settings. He showed video of workers stacking heavy materials while wearing a slightly bulky mitten-like device that was connected to a powered robotic arm.

Based on this success, Professor Kazerooni is now conducting DARPA-funded research at four sites to develop a powered orthosis that soldiers can wear to enable them to walk long distances carrying very heavy loads without fatigue. He emphasized the practical value of having complex software if it results in a final product that is easy to use, an approach that has obvious implications for P&O designers. The Berkeley Lower Extremities Exoskeleton or BLEEX project has created a 31 pound backpack-based system that includes a battery and a self-storing HKAFO with powered joints that is now being commercialized for lifting jobs. He showed very impressive video clips of a soldier running smoothly across rugged terrain while wearing the BLEEX and carrying a 150 pound pack on his back.

David M. Gardiner PhD then reviewed some of the implications of his basic science studies of urodeles, a type of salamander that is th only vertebrate animal who can regenerate full body parts. This research suggests that all animals use the same mechanism to grow body parts as an embryo, so he is hopeful that this work will ultimately generalize to humans. Currently, researchers suspect that one key will be to get regeneration to start by making a blastoma cell.

In urodeles, blastomas arise within 1 millimeter of cells at the margins of amputations. Usually, an incision heals itself but Dr. Gardiner has demonstrated that routing nerves to the wound in the antero-posterior direction results in generation of an additional limb. This suggests that all of the information required to grow a completely functional limb must be contained within the blastoma cell. He also noted that salamander scars quickly mature into absolutely normal skin, yet another potentially valuable offshoot of his amphibian research if the same process can be induced in human subjects.

Richard O'Donnell MD from the University of California San Francisco reviewed the seminal work done by Brannemark in Sweden investigating the feasibility of direct skeletal attachment of limb prostheses. He suggests that 1990-1995 can be viewed as the "learning years" where the Scandinavian surgeons worked out the practical aspects of the operation and therapy clinically while 1996-1999 could be considered the "refinement era" where the protocol was tested and modified based on increasing experience. Since 2000, a multicenter, prospective study has been underway to determine if these results can be replicated or improved upon.

Dr. O'Donnell noted that it would be extremely difficult to replicate the European studies in the USA due to our more restrictive Federal laws, so his research is taking another tack. Favorable results from spring-loaded internal prosthetic constructs have been shown to result from increased bone hypertrophy, so this mechanism may be applicable to protruding abutments as well. Animal studies with goats are currently in progress in the USA to validate whether or not this approach seems to have merit as a precursor to applying for FDA permission to begin human trials.

Darrell Christiensen CO gave a fascinating lecture on a thoracic orthosis for treating pectus excavatum that he has helped develop at USC-SF. Although the condition is usually benign, it tends to worsen during the teen years due to rapid bone growth and about 2 percent of all cases require surgical correction, which is expensive and carries some risk. In an effort to avoid surgical complications and costs, German researchers tried to create a vacuum device but it only resulted in slight correction of the deformity.

Darrell's team has developed a treatment that involves much less extensive surgery to implant a high tech magnet under the sternum. Another high strength magnet with reversed pole is incorporated into a custom anterior thermoplastic shell. An FDA investigational exemption application is currently pending so they can document whether the magnetic field is of sufficient strength to significantly correct the deformity. If this approach proves effective, it would represent a new way for orthotists to assist in the management of this disorder.

John Mogford MD presented an overview of the recent multimillion dollar DARPA grant that is funding several centers to simultaneously work on improving the function and appearance of limb prostheses over the next few years. He explained that DARPA is focusing primarily on the upper limb since there is a strong need for better function of these devices. The ambitious goal of this grant is to fully replicate the human arm in a way that it can be neurally controlled and is FDA approvable. To encourage rapid commercialization of the results, the focus is on further development of current state-of-the-art technology to make it stronger, more versatile, and more useful clinically.

This increase in government funding for prosthetic research is another example of the positive spin-offs from the military's decision to contract out the care for returning veterans injured in the Middle East to the private sector and providing a mandate to provide them with state-of-the-art care. The positive results from the best technology we have to offer have both impressed Congress enough to allocate additional funds as well as educated researchers such as Dr. Mogford about the limitations of today's best. Even if the DARPA project falls short of its lofty goals, it is highly likely that the result will be much improved technology and care for our patients in coming years.

The first session on the final day of the Assembly dealt with Innovations in Lower Limb Prosthetics and opened with Matt Henderson sharing his experience with a primary amputation in 2001 after multiple failed limb salvage attempts. His amputation was a modified Ertl type but there were numerous complications that limited his weight bearing potential and resulted in a distal bursa. He underwent revision surgery by Ertl himself in 2004 and reports being non-weight bearing for 8 weeks but able to run on his transtibial prosthesis at 12 weeks. He stressed the importance of finding a surgeon with sufficient experience with the Ertl method to perform the surgery properly.

Marlo Ortiz CP(m) then reviewed the key principles of his approach to hip disarticulation fittings, which is based on his success with the MAS® socket. Marlo prefers to use the half-socket described by Littig et al. He believes that the supra-illiac to medial ramus dimension is a critical aspect in stabilizing this design on the patient's pelvis and corrects the positive model to this dimension as measured by calipers.

The preferred impression is a non-weight bearing technique using pliable tubing to define the supra-illiac region at the waist. One hand molds the anterior aspect of the cast to determine the mounting surface for the anterior hip joint while the other hand carefully defines the ischial-ramal complex medially. A series of test socket fittings are performed until comfort, control, and suspension have been optimized.

Marlo generally uses the Littig Strut to provide increased hip and knee flexion during swing phase in combination with a dynamic response foot. The hip joint is placed more laterally than usual with the femoral pylon adducted to place the knee and foot so that the patient can walk with a narrow base. The knee joint is initially more triggered than usual with the final alignment determined by iterative walking trials.

The finished socket is a flexible interior half-shell on the amputated side encircled by a lightweight and rigid carbon fiber frame. Suspension is provided by a semi-flexible thermoplastic lateral shell connected to the socket by the strap arrangement as presented in Littig's article. Marlo showed video clips of several patients who demonstrated good ability to load the Strut and displayed little or no tendency to vault when walking.

Kevin Carroll MS, CP concluded this session with a nice review of the highlights of his management of a young man who sustained bilateral transfemoral and unilateral upper limb traumatic amputations at age fifteen. Kevin followed the traditional pathway of providing stubby prostheses that were gradually lengthened as the young man's balance and strength improved. Donning was a special challenge but video clips showed that this patient can pull into his full suction sockets using a synthetic pull bag. He does this from a kneeling position, bracing his prosthetic arm against a chair for balance. At present, he is a community ambulator with three prostheses who does not use any balance aids.

The final session I attended was on Stance Control Orthoses. Kelly Clark CO opened the session with a very thorough update of the SCO Matrix originally developed for the Academy sessions a few years ago. In view of the number of advances in this area, this was a very timely presentation that emphasized the growing range of patients who can potentially benefit from stance control components.

The next three talks were all by members of the research team at the Mayo Clinic in Rochester, MN. Kathie Bernhardt, BS presented the results of a patient survey she had conducted with 20 subjects who wore stance control KAFOs. The results generally confirmed clinical consensus, reinforcing the impression from prior studies that weight of the device or limitations in cosmetic appearance are NOT major factors in the rejection of KAFOs. On the contrary, it seems that a lack of useful function is a much more serious problem; if the function is good enough, patients will accept necessary compromises in other design aspects.

Steven E. Irby MS then reviewed the biomechanics of the microprocessor-controlled stance control knee joint that Mayo has developed, which is called the SensorWalk and is being distributed by Otto Bock. One of the primary advantages of this component is that it can be unlocked under load and therefore can accommodate knee flexion contractures of up to 30 degrees. It also carries a 300 pound weight limit making it the highest rated knee component of this type. Steve pointed out that half of the patients in their study were not candidates for then-available SCOs due to weight restrictions, muscle strength requirements, and similar clinical factors.

Kenton R. Kaufman, PhD, PE presented gait laboratory data from patients using the SensorWalk demonstrating the same range of improvement in energy efficiency as with Horton's SCOKJ®: significantly better than any locked knee component but nowhere near as efficient as a normal limb. Ken stressed the clinical importance of designs that will release under load as well as stabilize the knee regardless of the flexion angle.

This session concluded with a case presentation by Gary Bedard CO, who reviewed potential substitutes for quadriceps weakness such as increasing lordosis or genu recurvatum. He showed the results Kel Bergmann achieved with a Marine who had his entire quadriceps muscle group surgically removed following severe battlefield wounds. As would be expected, this gentlemen did very well with a UTX KAFO because his involved side hip strength and range of motion were essentially normal. Gary commented that this patient could immediately walk on level surfaces and vary his cadence but required training and some practice to learn how to walk down slopes. By allowing his ankle to dorsiflex farther than normal, he was able to release the knee joint during descents.

Reader Comments: Read all user comments Sr. Jhn Michael ¿Sería posible acceder a la protésica de miembro superior en español? Muy interesantes los artículos y gracias por enviarme The O&P Edge. Saludos cordiales. Omar Di Santo O.P. - Omar di Santo   1/18/2006 Re: Sr. Jhn Michael Sr. di Santo- I would be very pleased to post a Spanish language text on upper limb prostheses but I have not found a source for one thus far. It was only through the generosity of the late Dr. Sidney Fishman that the lower limb volumes c... read more - John Michael   1/18/2006