John Michael's Corner Welcome to the intersection of orthotics and prosthetics in cyberspace!
This month will highlight the presentations from the "Surgical Advances" segment of the International Conference of Advanced Prosthetics, and suggest some excellent software for study of the human skeleton. There is also an update and some additional photos from the collaborative fitting for a young man with an interscapular-thoracic amputation initially presented last month.

Please feel free to leave your comments and suggestions regarding this information in our guest book. If you would like to be notified by e-mail whenever this corner is updated, please become a registered user of oandp.com.

Table of Contents
International Conference of Advanced Prosthetics (ICAP)

This conference, initiated by the folks at Flex-Foot and hosted in collaboration with the University of California Irvine and California State Dominguez Hills, was intended to highlight the most advanced concepts in surgery, prosthetics, and engineering. The standing room only attendance [as well as the hundreds who tried to register after the hotel lecture room capacity had been reached] indicated a very high level of interest in such a meeting.

The overwhelming consensus that I heard from attendees was that this meeting was an unqualified success and should be repeated in a few years to provide additional information about emerging technologies. In fact, a number of senior practitioners ranked the ICAP as “one of the best meetings ever attended” and we all left the conference feeling re-energized and very positive overall about the future of the field. Each month for the summer, this Corner will highlight a different session from this landmark meeting. As soon as some minor editing is completed, the entire proceedings will be available on NTSC videotape for purchase from the Flex-Foot site at www.flexfoot.com

The first morning focused on the surgical practices, particularly for primary amputations and reconstructive secondary procedures. For the most part, this was all familiar material to me since virtually all of the concepts had been presented or published previously. But, to the best of my knowledge, these concepts had never all been presented together at a single conference so this was an excellent opportunity to hear the best in surgical and clinical thinking.

ICAP Highlight: Osseointegration

Rickard Branemark, MD, MSc, PhD kicked off the morning’s sessions with an overview of the principles of osseointegration. This was followed by a very thorough and frank review of this initial series of 16 transfemoral amputees who have received bone implants allowing their prostheses to be attached directly to their skeletal anatomy. His father, Per Branemark, MD has been a pioneer in this area whose maxillofacial implant procedures have revolutionized the attachment of dental and facial restorations, and are now accepted worldwide as viable, mainstream techniques. Just a few decades ago, the naysayers in the prosthodontic world were decrying Professor Branemark’s work in this area as an “impossible dream”. But, 800,000 patients later, it is clear that his vision was a good one. He is now trying to adapt what he has learned from facial constructs to create a bone anchor for limb prostheses too.

This is what the external abutment looks like. It is screwed through the skin directly into a titanium implant that is anchored inside the end of the femur. According to Rickard Branemark, the key to secure biological fixation is to avoid the formation of fibrous tissue between the implant and bone. For this reason, they have developed a very detailed and painstaking rehabilitation procedure for their bone implant amputees. Thus far, they have restricted their candidates to only those most difficult cases who were repeatedly unsuccessful in using a conventional prosthetic device. The initial surgery to place the implant within the diaphyseal bone end requires a few weeks for healing. The titanium implant is initially covered fully with skin and fascia so the residuum heals much like any other amputation. At that point, a conventional socket and preparatory limb is fitted in the usual fashion. Six months later, once the bone has grown around and into the implant, a minor secondary procedure is done to attach the portion that protrudes through the skin called an “abutment”.

After many months of graduated weightbearing exercises, the fixation of the osseointegration implant is strong enough to have an external connector attached to the abutment. Nearly a year of progressive loading under the supervision of a physical therapist then begins. The first three months are restricted to direct axial loading only [during therapy], using a “thigh extension pylon” terminating at the level of the opposite knee. The amputee applies controlled weightbearing on a stool or exam table and gradually increases the amount of loading applied. In response to this graduated weightbearing, the bone density and security of the implant both increase over time.

The prosthetic limb is then attached to the connector with a metric hex key. When the bone shows sufficient density, limited weightbearing with a full-length prosthetic limb then begins. The amputee starts with touchdown, then partial weightbearing using dual crutches, then using one crutch, and so on - eventually progressing to full weightbearing without any balance aids.

The prosthetic device is attached directly to the protruding abutment using a hex key, so there is no prosthetic socket or suspension needed. This eliminates all of the hassles inherent in socket use, including chafing, increased perspiration, problems from volumetric changes, and pistoning from inadequate suspension. At the present time, all upper and lower limb amputees with the Branemark procedure are using readily available components including the Otto Bock 3R80 rotary hydraulic knee, MyoBock hands and electrodes, and the Total Knee.

The result is a very secure connection to the prosthesis, including excellent rotary control and no pistoning. Alignment is reportedly sometimes tricky because the implant must be inserted in the orientation offering the greatest biological strength. This does not always coincide with the most biomechanically optimal position for the prosthetic knee, for example, so the use of various slide and angle adapters was shown. The abutment is deliberately designed to bend in the event of a serious fall, hopefully preventing injury to the bone or implant.

Dr. R. Branemark reported on a three-year follow-up of the initial 16 transfemoral patients who were the first to receive the implants. All had a history of dissatisfaction with conventional prostheses and all had skin problems, significant pain, or chronic suspension difficulties [often due to having very short residual limbs]. The majority had sustained the amputations due to trauma but two had diabetes and two were due to tumor removal.

Sagittal and coronal plane mobility is also superb, exceeding the capabilities of even the best available prosthetic socket. Five mechanical complications were observed during this period. Two abutments failed, one abutment screw failed, and one fixture failed following a fall but was salvaged by applying an internal clamp around the bone end.

Not surprisingly, infection was the most common complication. Fourteen superficial infections were noted as well as seven deep infections. All were treated with antibiotics but one case required reamputation at a higher level, one person developed a chronic infection, and five experienced loosening of the abutment. Three of these latter complications were resolved by repeating the surgery and placing new implants.

One of the diabetic amputees died while thirteen non-diabetics continue using the OI prostheses, although two now have chronic infections. Two of this original group do not use an OI prosthesis at this time. Overall, Dr. Branemark considers the usage rate of the OI prostheses to be 85% for this first group.

Based on the experience to date, Dr. R. Branemark suggested that unilateral amputees are the preferred candidates, although the first person to receive the procedure was a lady with very short bilateral transfemoral amputations. He also proposed these contraindications:

  1. Atypical skeletal anatomy, such as congenital absence or osteoporotic bone, as this would make the implant stability tenuous.
  2. Presence of systemic diseases such as Diabetes Mellitus or Peripheral Vascular Disease or chronic smoking. All of these factors compromise healing.
  3. Poor compliance, due to the intensive long-term therapy required if the bone is to withstand the forces of weightbearing and ambulation.

Obviously, this is a controversial procedure that is not yet perfected. Branemark noted that, based on the above criteria, less than 7% of all new amputees in Sweden would even be potential candidates for OI. But, it is also clear that this approach does hold great promise and could be extremely valuable in improving the quality of life for those amputees who “cannot be successfully fitted” using current technology. Despite the frequent complications, it appears that the majority of those who have volunteered to blaze this new trail consider it a good gamble and believe that they are better off than before the surgery.

It will be important to see these results published in a peer-reviewed journal, including longer follow-up with larger numbers. This is certainly groundbreaking work, and should be closely watched by anyone with an interest in amputee rehabilitation.

Video 2 (4.6M)
Patient connecting prosthesis to connector and demonstrating control of transfemoral prosthesis.

ICAP Highlight: Muscle-Preserving Transfermoral Amputation

Frank Gottschalk, MD presented an excellent update on his method to preserve as much muscle strength as possible in transfemoral amputation. This technique was accepted by the multinational, multidisciplinary invitees at the ISPO Consensus Conference on Amputation Surgery held a few years ago, and is described in more detail in the Proceedings of that Consensus Conference. Visit the ISPO web site to inquire about this publication at www.ispoweb.org.

Gottschalk advocates careful preservation of the entire adductor magnus, along with suturing the insertion directly to the end of the femur at the normal resting length of this muscle group. Dr. Gottschalk’s basic premise is that if the surgeon makes the extra effort to maintain the functioning muscles in their normal orientation and at their normal resting length, they will be biologically ready to offer maximum function. According to prosthetists who have fitted patients receiving this type of amputation, this translates clinically into much better voluntary control of the prosthesis by the amputee.

Much of this presentation was focused on evidence from the literature to support these postulates. Jaeger published an article in Clinical Orthopaedics and Related Research in 1995 showing a gradual loss of 40-60% of the original muscle mass when they were allowed to retract, rather than being anchored to the bone end. Presumably this is due, at least in part, to disuse atrophy since such excessively mobile muscles are unable to stabilize the femur directly and therefore cannot be exercised effectively. Gottschalk concluded by noting that his technique is often suitable for dysvascular individuals, contrary to what might be expected, because the preservation of the tendinous junction of the adductor magnus provides sufficiently strong tissue to anchor that muscle mass securely to the distal femur.

ICAP Highlight: Distal End Bearing

Dr. Jan Ertl reviewed the surgical technique originally developed by his grandfather and advocated by his father for many decades. Although some surgeons have done the Ertl bone-bridge procedure selectively, as a reconstructive technique at the time of revision surgery, Dr. Ertl argues that this should be a primary amputation technique. Based on his experience, he feels that the extra surgical time required to connect the distal fibula and tibia with a periostal flap is justified by the long-term improvement in the quality of the transtibial residuum that results.

He also noted that it is only necessary to remove about 1.5 centimeters of bone to create the necessary flaps, so the criticism that this unduly shortens the residual limb is unfounded. Dr. Ertl also advocates periostal capping of the end of the femur as he feels this will retain the normal closed environment of the diaphyseal bone, in contrast to the standard approach of leaving the medullary canal open.

Jan Stokosa, CP then discussed the specifics of a prosthetic fitting protocol designed to maximize the benefits of the Ertl procedure. The overall goal is to gradually load the bone bridge until it is strong enough to withstand full end loading. If it is loaded too early or too aggressively, it can be broken. If it is not loaded sufficiently, it will never attain full strength and will gradually become osteoporotic.

Jan also highlighted the need to accommodate the functioning muscles in the socket design for these patients. For transtibial cases, he often uses a flexible material at the proximal posterior wall [in the popliteal area] to better accommodate the mass of the gastroc-soleus remnants.

When I practiced in Chicago in the 1970’s and 1980s, I saw a handful of amputees who had their surgery performed by Dr. Janos Ertl from Hinsdale, Illinois [Jan Ertl’s father]. To this day, they stand out in my mind as among the very best prosthetic candidates I have ever cared for.

Exoskeletal prosthesis from the 1980s for a transfemoral amputee with an Ertl procedure. Note the muscular bulk of this residual limb, and the use of a one-ply sock in addition to suction suspension but without any auxiliary suspension such as
a Silesian belt Those with a transtibial Ertl gradually developed nearly 100% distal end bearing capabilities over time. This allowed me to gradually increase the distal end loading with successively thicker and denser end pads, and to correspondingly decrease the amount of proximal loading over a period of months. In essence, they functioned biomechanically as if they had a Syme ankle disarticulation but without the problems associated with the bulky contours in the ankle region. One gentleman in particular was a 300-pound farmer who regularly lifted heavy bales of hay and other barnyard paraphernalia. Without the ability to comfortably load the distal end of his residual limb, he could never have sustained the activity level that he needed to operate his farm on his own.

I have fitted one transfemoral amputee who had the Ertl procedure, and he too could comfortably tolerate significant end bearing in his socket. More importantly, his muscular tone was phenomenol, which provided excellent control over the prosthetic leg. In fact, although he could wear a full suction suspended socket, he preferred to use a thin cotton sock to absorb some of the perspiration and shear stresses inherent in socket use. But, he had no problem maintaining secure suspension despite the presence of this wicking material between his skin and the socket. From hindsight, I am now convinced that he used muscle suspension to supplement the suction suspension, but in any event it was physically impossible to pull the prosthesis off his residual limb without releasing the one-way suction valve.

ICAP Highlight: Stump Lengthenings

Stuart Green, MD presented a very entertaining review of the history of the Ilizarov method for surgical lengthening of the limbs, with a special focus on the prosthetic applications. As you may know, Dr. Ilizarov is a Russion surgeon with a clinic in the remote Siberian area. Partly due to the lack of modern prosthetic and orthotic care under the Soviet system, he was forced to find another way to treat leg length discrepancies and similar problems. Over many decades, Dr. Ilizarov developed the principles of gradually distracting the bone [about 1 millimeter per day] so both hard and soft tissues gradually remodel and the limb is lengthened or the angulation improved.

Dr. Green was one of the original US surgeons to meet with Ilizarov and to publish and help popularize his concepts in the non-Soviet world. He showed a series of upper and lower limb cases where lengthening had been useful in improving the leverage for very short residual limbs. He also reviewed the limitations in this procedure, which is not a panacea, but is now an accepted method for reconstructive techniques across the globe.

ICAP Commentary

The proposals and techniques discussed in this first session of the ICAP meeting seemed to me both familiar and sensible. The underlying theme was that the amputating surgeon has a very important responsibility to create the most functionally useful residual limb possible. Clearly, all the speakers were intimately involved with amputee rehabilitation and therefore advocates of techniques that promise to ultimately improve the quality of life for their patients.

However, none of this information was truly new and many of the techniques were in use decades ago. And yet, these simple concepts are still rarely followed by the majority of general surgeons who actually perform most of the amputations in the USA. Many reasons have been given for the lack of acceptance of such proposals, including the time limitations imposed by today’s Managed Cost Organizations. Another criticism has been the lack of any convincing objective outcomes studies documenting the superiority of one technique over another, despite enthusiasm based on anecdotal reports.

I don’t really know how to hasten the wider dissemination of these ideas beyond continuing to educate all who will listen about the promise of such efforts. And, of course, we prosthetists will continue to overcome as many of the limitations in less-than-optimal residual limbs as we can by using our clinical skills and available technological advances.

It may just be that progress takes time and I am too impatient. But, I can’t help but yearn for the day when every amputee I see has been treated with such surgical finesse that he or she has the best possible chance to benefit from the use of an artificial limb. I hope we find the way and the will to make this happen…

Anterior view of diagnostic prosthesis showing location of the single EMG site [marked by white self-stick Velcro square] used to provide independent opening and closing of the SensorHand. Collaborative Interscapular-Thoracic Fitting: Update

Last month’s Corner introduced a young man with an IST amputation who is interested in using an active prosthesis. Over the past month, Mike Truesdale CP has created a revised test socket and Bobby has continued to practice with the SensorHand to see if he can improve his myoelectric control capabilities.

Bobby has decided that he clearly prefers the AutoGrasp and other capabilities of the SensorHand, so this will be the terminal device in his definitive prosthesis. The folks at Motion Control are currently making up a one-of-a-kind circuit that will permit Bobby to use the Servo control for elbow flexion, extension, and lock - while using a single site EMG signal to operate the SensorHand independently.

Posterior view of diagnostic prosthesis. Note use of an axilla loop for activation of the Servo control for elbow flexion and extension. This was later changed to a less confining cross-chest control strap with no loss in control specificity. The advantage of the cross-chest strap is that the contralateral shoulder is then unencumbered by the prosthetic harness, facilitating bimanual activities. If EMG control proves successful long term, changing one coding plug can upgrade the single site myocontrol from the initial “cookie crusher” logic to dual-mode proportional opening and closing based on the speed of the muscle contraction and relaxation respectively. On the other hand, if maintaining electrode contact throughout the day or muscle fatigue should become problematic, it will be readily possible to revert back to Servo switch control of both elbow and hand in the future without the need to replace the socket or even to change the harnessing.

Anatomy Software

There are a number of good, low-cost software packages out there to help clinicians review the human anatomy or to provide illustrations for presentations and publications. I recently found a $29 program from England at www.primalpictures.com that has some of the most exquisite skeletal photos I have ever seen. You can easily cut and paste the illustrations into your lectures or papers, and it has some very nice interactive features. For example, you can click on a particular bone and color-coded muscle origins and insertions will appear.

The Interactive Skeleton is also available in a more versatile Instructor’s Version. I would recommend that all P&O faculty take a look at this software, and that all clinicians with an interest in this area consider purchasing the basic version.

Three dimensional attributes of the skeletal anatomy are very easy to visualize thanks to the excellent image quality on this CD-ROM based software. Clicking on the image [such as this knee joint] highlights the muscle, ligament, and tendon attachments in blue. Moving the curser over each highlighted area calls up a dialog with more information about each structure.