John Michael's Corner Welcome to the intersection of orthotics and prosthetics in cyberspace!
This month will highlight a regional Academy meeting, suggest additional videos for your professional library, and offer a clinical tip on a better way to create custom suspensions without using bulky and cumbersome Yates clamps. There is also a mini-case presentation of a collaborative fitting for a young man with an interscapular-thoracic amputation, and a final "Internet Resources" segment on MP3 audio files.

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Table of Contents
Great Plains Chapter AAOP Meeting

Only the Great Plains Chapter of the American Academy of Orthotists and Prosthetists would schedule scientific presentations that started at 7:30 AM , continued until 5PM, and have standing room only from start to finish. Such commitment to serious learning is typical of the ubiquitous work ethic in the Upper Midwest region served by this Chapter.

The program was a nice mix of local and national speakers who were medical and P&O professionals. Ramona Okamura CP from the University of Washington gave two very well organized presentations. The first was a systematic review of the physics behind the traditional upper limb harnessing taught in the schools, highlighted by practical explanations for why some of our cherished guidelines don't make much difference in actual clinical practice. Ramona's second talk briefly highlighted the conclusions from some of the seminal original research at UW investigating dynamic response feet and the mass distribution in prosthetic devices.

Most of these articles have been published in the Archives of Physical Medicine and Rehabilitation in recent years and Dr. Czerniecki is always one of the primary investigators. You can find citations and abstracts of thousands of P&O articles, including these, in the RECAL database maintained by the University of Strathclyde. For a very modest subscription fee, you can have unlimited access to these files at

RECAL citations include abstracts highlighting key points. All documents listed can also be ordered from the University of Strathclyde for a modest fee.

Key points Ramona summarized include the finding that all spring-loaded feet have a certain response frequency and amputee gait would be most energy-efficient if the spring frequency was congruent with their cadence. Another finding, supported by other researchers, is that simply making a prosthesis lighter has much less positive effect than being careful to insure that the mass is located more proximally in the structure. This supports the clinical impression that the use of more functional but heavier knee units, or the inclusion of torque absorbers and positional rotators in the knee region, rarely results in amputee complaints.

Collaborative Interscapular-Thoracic Fitting

IST level of ablation leaves only the chest wall on the involved side, making socket stabilization and control of an active prosthesis difficult. I recently enjoyed the privilege of working with Mike Truesdale, CP and his staff to assist in the fitting of a young man in his 20's who underwent an IST level amputation due to sarcoma at nine months of age. He was fitted with a fully body powered prosthesis as a child but soon abandoned it. Despite strong motivation to learn to use an active prosthesis at this time, both his level of loss and the long period without a prosthesis made this a particularly challenging undertaking.

When the entire arm and shoulder girdle has been ablated, use of externally powered components is usually the only practical approach available to offer active function. Preliminary EMG testing had identified two potential control sites. One was high on the posterior aspect or the torso where a remnant of the rhomboids may have remained. The other was located more anteriorly near the inferior border of the ribs and may have been part of the oblique abdominals. Because Bobby had powerful, highly mobile shoulder with good muscular development, use of a body powered elbow could not be ruled out. My role was to assist with the evaluation and diagnostic fitting of a range of plausible components and harness configurations to help Mike and his client determine the best way to proceed.

The MyoBoy is a lightweight myotester/trainer/troubleshooting unit, powered by a standard 9V battery, that is bundled with a very versatile software package allowing you to fit a virtual electronic prosthesis. We used the new Otto Bock "MyoBoy" as the primary evaluation tool to determine what type of myoelectric control would be most effective. The MyoBoy is a fantastic tool for such tasks because the bundled software allows you to quickly fit virtual versions of the full range of Otto Bock electronic terminal devices. It's the equivalent of having over $50,000 in electronic hands, Greifers, wrist rotators, and controllers in the facility for the client to try out. In addition, it has a number of very useful training, evaluation, and practice screens to aid in mastery of a myoelectric prosthesis.

The MyoBoy software allowed Bobby to practice controlling an assortment of virtual electronic hands and Greifers while the gain settings were adjusted and the electrode placement and orientation was systematically varied. By the time Friday's session ended, we had determined that it was very difficult for Bobby to co-contract reliably or to modulate his EMG signals and differentiate between a slow, gentle and a hard, fast contraction. This meant that the two most common mode-switching strategies would not work well for him at this time.

In addition, his sites fatigued quickly and his control deteriorated to the point that he could not vary the rate of his EMG signal. This made proportional control of very limited value as well.

Among other features, the MyoBoy software allows the amputee to control a virtual electronic hand, Greifer, and wrist using single or dual site electrodes. Since Bobby had been practicing with a myotester for several weeks to improve his EMG control, and because he had never used his remnant muscles because his amputation occurred at such a young age, we felt it was doubtful that his control would improve dramatically in the near term. He was marginally able to control a two-site digital hand but did the best by far using the Electronic Voluntary Opening mode of the SensorHand.

In this type of "cookie crusher" control, any signal from a single EMG site opened the hand fully and relaxation closed the hand. And, although the SensorHand closes with only 10 Nm of initial force in this mode, the AutoGrasp feature means that this hand will self-adjust the grip if an object starts to slip by incrementally increasing the grip force. This made effective grasp very easy for Bobby to achieve and reduced the need to use visual cuing. In addition, should Bobby's EMG control become more refined over time, changing a $15 Coding Plug in the SensorHand would convert the arm to proportional single site control - using the same socket, electrode, elbow, and suspension. If he develops the skill over time to use this VarioControl mode, the speed of hand opening would be proportional to how quickly the myo signal was generated, and the speed and force of closing would be proportional to the speed of relaxation. No other available components offer this latter option.

The SensorHand uses small coding plugs [indicated by arrow] to allow the prosthetist to quickly change the control strategies from EMG to switch, from single site to dual site myoelectric control, and from constant speed to proportional control – making it particularly well suited for difficult fittings. Added functions, including the unique AutoGrasp feature, make this one of the easiest electronic terminal devices for the amputee to use. Saturday's morning session focused on fitting a SensorHand with EVO control and an Ergo Elbow flexed by contralateral scapular abduction. Following the German harnessing method depicted in the Otto Bock Upper Limb Compendium, we verified that Bobby could achieve full elbow flexion as well as reliably lock and unlock the body powered elbow without activating the terminal device. His control of the SensorHand using EVO control improved steadily and he was soon able to demonstrate simultaneous, independent control of grasp and elbow flexion.

Harness depicted here provides simultaneous, independent body powered control of elbow flexion, elbow locking, and terminal device operation. When an electronic terminal device is used, the gray strap running obliquely across the back is not needed. Harness depicted here provides simultaneous, independent body powered control of elbow flexion, elbow locking, and terminal device operation. When an electronic terminal device is used, the gray strap running obliquely across the back is not needed.
When elbow control is independent of terminal device control, it is not necessary to lock the elbow to achieve functional grasp and release. This concept is sometimes referred to as the "Glimscher Test", and it makes use of the prosthesis quicker and easier than if the more traditional sequential control is offered. With either the Utah Arm or typical "fair lead" body powered elbows, the terminal device will not operate until the elbow is locked. Such sequential control requires more patience and more concentration than when simultaneous control is offered.

The ErgoArm elbow-forearm set-up makes fitting a hybrid prosthesis much easier for both prosthetist and amputee. All electronic controls and the battery power source plug into the inside of the turntable and exit at the wrist. The unique Automatic Forearm Balance can be set to completely offset the perceived weight during flexion of the terminal device and/or rotator, making both harnessing and active flexion much easier. As might be anticipated, the biggest drawback to the use of a body powered elbow was that Bobby had to use his full range of contralateral scapular motion in order to achieve full elbow flexion. [Remember, at this level of loss the entire involved scapula has been removed so biscapular excursion is lost.] As clinicians, we need to be very cautious about using body powered solutions when the client is barely able to achieve full operation.

The well-documented rejection of body powered prostheses by high level amputees is due in large part, in my opinion, to the frustration that usually follows when control of a prosthesis is a struggle. My experience suggests that it is more productive in the long run to find a control method that is easier for the amputee to master. Based on that philosophy, we decided to create a different diagnostic arm for comparison purposes.

Saturday afternoon we fit Bobby with a servo-controlled Utah system using the same test socket. It quickly became clear that he could operate the electronic elbow with much less effort than the body powered one. Hand control was not as good as with the EVO mode of the SensorHand, but with some practice and fine-tuning of the U2 ServoControl potentiometers this gradually improved. By the time the afternoon session ended, we were all in agreement with Bobby that he would require an externally powered elbow for his definitive design.

The Utah ServoPro control is particularly advantageous for higher level amputees since it requires zero excursion. Because it is a force-based sensor, it is often possible to harness it very loosely. This increases amputee comfort and allows a greater range of motion without inadvertent activation of the electronic components. Even though he could demonstrate successful operation of the Ergo Elbow, he had barely enough unilateral excursion available and had to strain to make it work. With the electric elbow, in contrast, his harnessing could be simplified so that the contralateral arm was no longer encumbered in any way. The dual benefits of easier operation and a full work envelope for the uninvolved upper limb made the electric elbow clearly the best option for Bobby. This also provided a concrete functional justification for use of the electric elbow that could be easily documented for his insurance company.

Bobby returned on Sunday to practice using the Utah 2 Arm and to allow us to try some additional harness variants. By Sunday afternoon, we were unanimous in our decision to proceed with definitive fitting using servo control of the Utah 2. Bobby was very enthusiastic by this time, and we felt it was important to complete the definitive fitting in a timely fashion, so he will probably start with servo control of the hand even though this is a sequential system and does not utilize SensorHand with AutoGrasp capabilities. But, having only one control motion and no electrodes at this time will make it easier to learn to control the arm as well as to avoid the potential hassles of maintaining electrode contact when there is no residual limb remnant to stabilize the socket.

Bobby will continue practicing to improve his control over the two potential myosites, and wiring channels will be incorporated into the carbon fiber frame of his definitive socket just in case. If he develops sufficiently precise control in the future, his U2 Servo prosthesis can be converted to provide single or dual site proportional EMG hand control at that time by fitting a new inner socket with appropriate electrode mounts. Attaching a SensorHand at that time, combined with a special modified wiring harness from Motion Control, would offer the benefits of AutoGrasp too.

Recommended Resources

One of the recurrent struggles in prosthetic rehabilitation is to find a therapist with extensive post-licensing training and experience in working with amputees who can really help the novice master their artificial limb. Outside of selected regional rehabilitation centers, such expertise is often simply unavailable and the local therapists wind up doing the best they can with this specialized population.

Video resources to help in working with upper limb amputees were featured last month. Fortunately, videos to help in the training of lower limb amputees are also available. TherEd Resource is having a sale on all of their amputee resource videos, including the excellent series by Bob and Ann Gailey providing step-by-step instruction in gait training for the lower limb amputee. You can check them out or take advantage of the half-off sale prices at

Although it looks dated because it was taped a couple of decades ago, the video co-produced by Otto Bock and the forerunner of the Century College P&O program in Minnesota remains the single best source for information about learning to use hip disarticulation and transpelvic prostheses. The fundamental concepts have not changed, and the section on gait training is well done, so this is still a very useful addition to your professional library. It is available to rehabilitation professionals at no charge from Otto Bock USA in Minneapolis. They can be contacted at to request a copy.

What if your facility donated these videos to your local therapy department? Making continuing education readily available for self-study might be far more effective than continuing to grumble that majority of therapy schools don't prepare their graduates to offer amputee gait training!

Clinical Tip

Forget about Yates clamps! Anyone who has struggled to use Yates clamps to create a custom harness or Silesion belt knows how frustrating they can be to use. They are difficult to open with one hand, don't always hold the straps securely when tension is applied, and the black rubber pads harden with age and often leave ugly black skid marks on the fabric webbing.

Even worse, Yates clamps hold the harness so far away from the body that - once you have stitched the cross points down and removed the clamps - the final harness is always puckered and doesn't lay on the body the same as it did during the fitting. And, since Yates clamps are from the animal harnessing industry, they don't carry a very positive connotation when you bring a handful into the fitting room.

Hemostats being used as temporary clamps. Johann Streckfuss from Duderstadt, Germany showed me a much better way to accomplish these tasks: use small hemostats as temporary clamps. A half dozen 4.5 inch hemostats fit nicely in the breast pocket of your lab coat, clamp fabric and elastic webbing securely, and allow the straps to remain in full contact with the skin so the final result is just as perfectly routed as the temporary version.

Since they are stainless steel, they never discolor the webbing or deteriorate with age. Hemostats are also a breeze to clamp and unclamp with one hand, and are available with either curved or straight jaws. And, they hold the straps so securely that the amputee can try out the harness or suspension belt in your lab under dynamic load conditions so you can verify that the tensions are optimal or make any necessary fine adjustments prior to going to the sewing machine.

I use hemostats with straight jaws that are readily available from Radio Shack by catalog order, on the Web, or in retail stores in major shopping centers throughout North America. And they cost less than $5 each!

Internet Resources: MP3 Blues Music

The "Internet Resources" section will appear from time to time in this Corner, but this month's has nothing to do with prosthetic or orthotic practice per se. So, if you are solely interested in clinical information, skip this part!

The explosion in information and resources available at little or no cost on the Internet is phenomenal. The amazingly fast evolution of compressed music files in an excellent example.

During my travels, I often find myself sitting in an airplane, taxi, or hotel room trying to relax. For years, I carried a case full of CD's of my favorite music and a bulky player. A few year's ago, I stopped lugging the player because my laptop had had one built in. Thanks to today's MP3 technology, I don't need to schlep either the CDs or a player any more.

Freeware from WINAMP includes an electronic equalizer, MP3 player, and jukebox. It will also play streaming audio from the Internet. MP3 files are compressed versions of CD audio files that store easily on your hard drive and can be played back using MP3 Player software. My favorite player is Winamp, which is a free download at

Another good freebie is the Windows Media Player that is bundled with Window 98 or free from

If you want to listen to some MP3 files to see if you like the sound quality, you can use your search engine to find some of the many MP3 sites. Or, use your browser to go to my Internet Radio Station and listen to some electrified blues tunes at:

You can listen to any of the songs for free, click on the links to download free MP3 files from any artist you like, or just listen to each song in the list sequentially by clicking on the Low Fi or Hi Fi radio buttons. If you really like what you hear, you can also buy a CD directly from the performers for about half the cost of a commercially promoted disk. And, the Digital Audio Music CDs include MP3 versions of each song as well as standard versions that play through any conventional CD player.

There are commercially available portable MP3 players for $300 and up but I have never tried them since you can play the files for free on any computer with a sound card. I do sometimes play MP3s on the palm computer that I use to keep track of my appointments, tasks, calendar and contact information. To my ear, the sound through headphones on the Casiopeia E-105 is almost as good as it is on a full sized laptop or desktop. And, with a $20 adapter from K-Mart, I can broadcast the files through the FM radio in any automobile so I'm not stuck listening to commercials or fading reception on a long drive.

To convert your own CD tunes into MP3 files, you will need a piece of software called a "ripper", which reads the audio CD in your computer's player and automatically converts the contents into files stored on your hard drive. I currently use shareware called Audiograbber [available from] but please try out the free version before buying any shareware, to verify that it works well with your particular computer and CD player.

You can see why MP3 files have become so popular: they are versatile, convenient, and portable. Of course, like the cassette recorders that preceded them, MP3 technology can also be used to distribute illegal copies of commercial songs. In my view, that is wrong because it cheats the performers out of just compensation for their creative efforts. It is also clearly illegal.

The key is be certain that you make MP3 copies only from CDs that you own, and that you use them only for your personal listening pleasure. Of course, the thousands of free MP3 files on the Web posted by performers are also legitimate, and offer new artists the chance to reach a wider audience.

Happy listening……