Once again in the summer of 2008, the Institute of Biomedical Engineering hosted the MEC symposium; the foremost international conference on all aspects of the design and application of Upper Limb prosthetics. It was held in New Brunswick Canada, and it saw some of the leading research in Upper Limb prosthetics as well as some of the latest products and techniques.
This field is changing rapidly. The contributing factors to this change are varied and numerous, but the underlying reason is a coming together of two decades of advances in technology and techniques in other fields that the prosthetics industry can now exploit. This “parasitization,” as Jon Kuniholm described at MEC'08, is the reusing of ideas and methods made practical and affordable by the investment of other industries for the benefit of artificial limbs. For example; the life and power of batteries that can now be fitted to a hand is considerable, compared with those only a few years ago. The investment to develop this technology comes from the computer and mobile phone industries, and this investment dwarfs the current levels of direct investment within the field. Thus, new prostheses currently being marketed are the result of many years of effort and investment from government and private finance sources, with little directed purposely towards prosthetics.
MEC's theme this time was “Measuring Success,” and papers were presented to illuminate this theme. In addition to the free papers, the conference held two workshops to encourage standards within in the industry. The first workshop aimed to encourage the standardization of electronic communication between prosthetic components. With the proliferation of microprocessor-controlled prosthetics systems, there is a real danger that without a standard, prosthetic devices from different manufacturers will not be able to work together—and so clinicians will not be able to offer the full range of prosthetic components on the market. Ultimately, users are the ones that will suffer. It is clear that the technologies that have succeeded in recent years have done so as a result of open standards within their field, rather than tight constraints imposed by a single manufacturer attempting to control the market. It is worth reflecting that the current leading computer manufacturers did not exist in the 1970s, and few of those companies that did exist then are still operational in 2009. Similarly, the Internet's success has much to do with its open format; attempts to control it have been counter-productive. Thus, the workshop aimed to facilitate similar openness in prosthetics.
Assessment of prosthetics use and outcomes also requires some standardization if we are to communicate results clearly to our colleagues. Hence, the second workshop, and the main theme of MEC'08. Carola van Dijk and Wendy Hill described the effort directed towards the measurement of function within the clinical setting. The critical aspect in this process is being to be able to objectively measure their effect of fitting a prosthesis on aspects of the users' lives from the function of their device to the way it makes the person feel in using the device.
The Upper Limb Prosthetics Outcome Measures Group (ULPOM) is attempting to create a consensus. Starting at the previous MEC and progressing through other workshops, a professional group has been formed and is addressing this problem using the World Health Organization's ICF model as a framework for definitions and approach. Wendy Hill outlined their progress.
The research arena also needs objective measures of the effect of new prosthetic devices. Many are familiar with the techniques of motion tracking for measuring aspects of gait. Advances in the measurement techniques mean that similar methods are becoming possible with upper limb and hand motion. Thomas Bertels showed one way to measure the changes in motions created by the provision of a wrist that flexes. This allows a change in the alignment of a prosthetic hand, potentially making it a more effective manipulator.
Novel prosthesis designs were not neglected, with Dick Plettenberg, Murray Maitland, Immanuel Gaiser and Andrea Cutti showing ideas as diverse as children's passive hand designs, a lightweight shoulder device, and the investigation of new grasping geometries. While the latter is currently only used within the laboratory, it is not until we can observe such devices being used by limb-absent persons that it will be possible to measure the effectiveness of providing such extra motions. Thus, we will be able to see if it is worth the effort and expense to develop and fit such devices. The INAIL device is a light and fast shoulder that has the potential to make placing the hand in an effective position possible. Maitland, in contrast, is seeking to redesign the gripping surfaces of a body-powered device to make body-powered devices easier to use, accommodating a wider range of shapes.
Kengo Ohnishi from Japan showed a systematic method to investigate the factors that are important in the creation of a myoelectric control channel.
MEC is also a conference about clinical practice, and Chris Lake's retrospective on partial hand technology and how these devices have been fitted was a welcome addition. Partial hands are one of the areas that have expanded in recent years as motors, electronics and batteries developed for completely different applications have advanced sufficiently to allow powered partial hands to be more easily manufactured and deployed.
One aspect of a maturing field is that there comes a time when the pioneers disappear. Since the previous MEC in 2005, two such pioneers from the UK have died. I would like to take this opportunity to mark their passing and the debt we owe to those that went before us. The two men's backgrounds and careers were very different, but both were bound by a desire to improve prosthetic limbs. While they developed their ideas in the 1960s and ‘70s, much of their work remains important and applicable with modern technology.
In the 1960s Jim Nightingale was a control engineer who had an interest in the analysis of systems that could not be analyzed simply. Such a system was a prosthesis being controlled by myoelectric signals. With the assistance of his graduate students, he investigated ways to control a hand with more than one motion. At the time, hands were limited to on/off signals and one active joint. It was clear that a person could not control many motions individually, so detailed management was left to an electronic controller and the user gave it simple instructions upon which it acted. The controller could then judge the appropriate action based on other information gathered about the target object and its surroundings. This control became known as the “Southampton Hand,” after the University where he was professor and group leader. Later these ideas were extended to the rest of the arm. In the mid-1980s a version of this controller was manufactured using an early microprocessor system. It was used by limb-absent individuals in the field, possibly the first-ever application of this technology to a hand in the field.
This form of control is based on the context of the device; such ideas are now being explored in many other fields and used for the control of legs as well as arms. Nightingale's group explored numerous other ideas in engineering, including functional electrical stimulation, where ideas of feedback and context based control were applied to paralyzed limbs.
At about the same time as Nightingale was looking at the control of limbs from the perspective of electromyographic input, David Simpson at the Princess Margaret Rose Hospital in Edinburgh was concerned with the idea of controlling gas-powered arms with multiple axes of motion as simply as possible.
Simpson's insight was that feedback, if it is to be returned to the operator, has to be appropriate for the task—so noises or vibrations to convey the idea of where a limb is in space simply cannot easily be learned by an average operator. Instead, Simpson linked the motion of the command input to the motion of the controlled joint in a simple, direct, unambiguous mapping. The result transferred the proprioception of the intact input movement to the movement of the output. This became known as Extended Physiological Proprioception (EPP), an idea that spread more widely to different centers of prosthetic application and research. EPP remains the only feedback method that sends information back to the operator and has been successfully applied to prosthetics. In recent years, with the increasing number of degrees of freedom that can be created for prosthetic limbs, there is an even stronger need for easy and practical control of these extra motions. EPP has the potential to assist in this.
As the director of the Edinburgh Unit for the disabled, Simpson was also responsible for the continued research in many activities related to rehabilitation. His successors have continued this path and the Touch Bionics i-LIMB hand is a product that emerged from Edinburgh; it is doubtful if it would have done so without Simpson's pioneer work two decades before.
Both men represent the leading edge of prosthetics research in Europe during the 1960s and ‘70s. Their work paralleled each other, with both men retiring in the 1980s while continuing connections with their work. In a sad coincidence, they died within a week of each other in the spring of 2006. Their successors acknowledge the debt they owe to these pioneers.
President's Research Chair
University of New Brunswick