Progress Through Synergy
One significant move forward occurred during the 1990s with the conception of the NovaCare Upper Extremity Prosthetic Program led by John Miguelez (J.M. Miguelez, personal communication, 2008). This marked the first formal group of practitioners united for the common purpose of specializing in and advancing upper limb prosthetics. Though most of their developments were proprietary in nature, it was the first time a sizable group of prosthetists looked beyond the brim when designing the socket. The program’s synergy helped catalyze upper limb prosthetic development. This program, acquired by the merger with Hanger at the turn of the millennium, still pushes the art of upper limb prosthetics and in a more public way, allowing the field to grow from their collective experience.
As the 20th century came to close, more oral presentations focused on anatomical socket design. Most of these presentations were exclusive to the University of New Brunswick MyoElectric Controls/Powered Prosthetics Symposium (MEC). In the absence of abundant written information, the MEC Conference, which commenced in 1972, provided the primary global forum for upper limb knowledge exchange and debate. Frame socket concepts for the shoulder levels were discussed formally by Miguelez and were noted or illustrated by many others in the 1999 MEC Conference.35
Alley at the 2002 MEC Conference ushered in a new era with the first comprehensive look at the effects of the anatomically contoured and controlled sockets at the transradial, transhumeral, and shoulder levels.19 Alley built upon the work of his predecessors and added significant emphasis on the biomechanics of socket design. Since that time, a renewed focus on socket design has resulted in many professional journals and books publishing progressive techniques in upper limb socket design.20,26,33,34
Socket Design as a Result of Material Science
As socket designs have evolved, so have prosthetic materials. Early prosthetists touted how well wood sockets could be shaped to mirror the residual limb. Discussion of the benefits of specific force distribution of lower limb applications was common in pre-1900 prosthetic text. The widespread use of measurements yielded to the more exacting duplication of residual limb contours through plaster impressions. Wood and leather succumbed to aluminum and laminates.7–12 Most important to socket design was the wide acceptance of thermoplastics. Thermoforming yielded more contoured sockets. Transparent materials allowed for critical analysis of socket dynamics beyond the proximal brim and essentially reduced the “bench time” of the prosthetist working wood and leather and increased the clinical time.36–39 Sockets became more flexible and comfortable. Additionally, more flexible materials allowed the prosthetist to be more anatomically conscious as the more aggressive contours enhanced stability while at the same time maintaining ease of donning. Plastics flexibility, the differing shore values of silicones and urethanes, and the understanding of composite lamination and construction materials continue to drive upper limb prosthetic socket design today.40–44
Current Perspective—Socket Design as a Result of Thinking and Experience
The field of Orthotics and Prosthetics has enjoyed significant advances in the last 25 years. As our field pushes further into research and development endeavors, we have begun to find ourselves focusing on specified interests of practice. Evidence of this is clearly seen in the formation and promotion of specialty societies within the American Academy of Orthotists and Prosthetists. Our field is entering a time reminiscent to the era that medicine navigated nearly a century ago.
Between 1916 and 1930 most of the current 24 medical specialties were conceived and developed. Whether for reasons of specific focus on systems of the body, particular ways of thinking, or the use of technology, medical specialties have given rise to medical advances that were only possible with such a focused approach. By the mid 20th century, medicine was no longer a profession where being a generalist was an option.45
Today subspecialties are readily seen in orthotic practices. Within large practices there are individuals who focus their professional endeavors on trauma and fracture management, pediatric orthotics, spinal deformities and trauma, cervical trauma management, and pediatric cranial deformities. Each of these focused endeavors requires a unique skill set to maximize patient care and outcomes.
The emerging specialty of upper limb prosthetics and focused therapy was highlighted by Atkins and Alley46 in 2002. Furthermore the need for synergy, clinical debate and professional relationships in our efforts will assure that upper limb prosthetics is not overshadowed by the increasing numbers of lower limb loss.
TODAY’S UNIQUE UPPER LIMB LOSS DEMOGRAPHIC CHALLENGE
Many challenges exist when treating individuals with upper limb loss. Aside from the physiological, sociological, psychological issues, the relatively small size of this patient group has meant that general prosthetists are often unfamiliar and/or inexperienced with the highly complicated fitting needs of this group. There is a 30:1 lower limb to upper limb patient ratio when one averages the adjusted numbers, Dillingham et al.47 found in their review of the epidemiology of limb loss in the United States. This ratio is a conservative estimate, based upon the most common levels fit—Symes to hip disarticulation and wrist disarticulation to shoulder disarticulation. This lopsided ratio is the crux of what prosthetists call the “upper limb dilemma,” whereby the most challenging cases are dispersed among practitioners who see such cases rarely and have fewer opportunities to hone their upper limbs skills, much less keep apprised of new devices, fitting techniques or therapy.
The second challenge relates to the expected growth in lower limb loss in this country. A rigorous analysis by Ziegler-Graham et al.48 predicts that the prevalence of limb loss in the United States will more than double from the 2005 figure of 1.6 million to 3.6 million in the coming decades. Broken down further—1 out of 190 Americans live with limb loss today. By 2050, that number will approach 1 out of 100. An aging population and increasing rates of obesity and vascular disease are driving this increase. Assuming that the incidence of upper limb loss remains steady, upper limb patients will represent an even smaller proportion of those with limb loss. If US upper limb cases decrease, a trend Heckathorne noted in his 2001 invited talk at the ISPO World Conference in Glasgow Scotland, these patients will have an even tougher time finding a general prosthetist with any experience fitting upper limb cases (C. Heckathorne, personal communication, 2008). Heckathorne used world census data to show generally declining or static populations in most of the more developed countries and significantly increasing populations in the less developed countries. He speculated that the future of upper limb prosthetics was in the less developed countries because of the shift of manufacturing and industrialized farming to those countries, generally less safe industrial environments, greater likelihood of major armed conflicts, and fewer medical resources to save injured limbs.
The third demographic challenge—the number of qualified prosthetists in the coming years, further complicates the upper limb scenario. In 2006, a workforce demand study was performed for the National Commission on Orthotic and Prosthetic Education and the American Orthotic and Prosthetic Association.49 A 0.5% net growth in certified orthotists and prosthetists is expected through 2010. After 2010 through 2030, a growth rate between 1.45% and 2.4%, depending on the addition of two new schools, is expected. Unfortunately, this modest influx of new practitioners will be erased by the projected 3.33 attrition rate. Clearly, these demographic forces are setting the stage for some very busy lower limb practices, in which individuals with upper limb loss could truly be lost in the crowd of lower limb patients and increasing numbers of serious vascular cases.48
The concept of more anatomically appropriate socket designs took root long ago. Generations of prosthetists have dreamed and experimented, just as we do today. Interestingly, the early concepts of Pare to address lower limb weakness and paralysis resemble the modern day endeavors of prepreg laminations to address the same presentations (Figure 6). Although Pare did not have access to these aerospace materials, he did not let that stop the conceptual thought process. Similarly, the professionals who followed him continued to fine-tune prosthetic devices and fitting techniques, at times getting a boost from 20th century industrial advances. Rising numbers of amputees during wartime also spurred growth in the prosthetic field and demand for new improved devices and sockets. With the emergence of transparent plastics and thermoplastics for intimate contouring, the dreams of our prosthetic pioneers are within reach.
As material science advanced the upper limb prosthetist was able to return to fitting challenges with new ideas. Socket design advanced almost simultaneously with material science. One such patient population to benefit has been the individual presenting with shoulder disarticulation level limb loss. Case in point—a continuous socket design (Figure 7) allows for the introduction of effective lateral loading of the thorax by connecting bilateral shoulder. The patient reports several significant benefits with this design in contrast to previous discontinuous frame designs. These include easier donning and doffing secondary to a significantly more stable structure, an appreciable increase in ease of inhalation with the elimination of anteroposterior harnessing, and a reduction of the patients perceived weight by at least one-half that of the discontinuous shoulder frames. This flexible yet structurally sound socket design was not possible until our understanding of composite science allowed such conception and execution.
As always in times of great scientific innovation and experimentation, the challenge is to capture those concepts for posterity and to share ongoing discoveries with other professionals in the field so that all may benefit and the pace of improvement is accelerated. Currently, the entire field of Orthotics and Prosthetics suffers from a lack of written documentation. This puts current and emerging advancements at risk. Often, significant breakthroughs arise from the insights a professional gains from others. Spoken history can be lost for good, whereas written history endures to inspire future generations, who may, like us, return to the same challenges with new technology and materials at their disposal. The American Academy of Orthotists and Prosthetists Upper Limb Prosthetic Society is newly committed to enhancing communication between all upper limb specialists. This synergy promises to nurture further advances, perhaps helping today’s upper limb professionals accomplish in a decade or two what took previous generations a century to realize.
As we push the specialty of upper limb prosthetics forward, perspective is important. We must remember who came before us—for both respect and knowledge. Words of a 12th century theologian and author come to mind. This phrase is often associated with Sir Isaac Newton in a letter he wrote in 1676. Interestingly the phrase goes back even further to John of Salisbury who was known to further his work through a significant knowledge of what was done previously.
“We are like dwarfs sitting on the shoulders of giants. We see more, and things that are more distant, than they did, not because our sight is superior or because we are taller than they, but because they raise us up, and by their great stature add to ours.”50
The author thank the following individuals: Terry Supan, CPO, FAAOP, FISPO, for his influence and sharing of his upper limb knowledge during my prosthetic residency at Southern Illinois University in 1995–96; Tom Andrew, CP, FAAOP, for introducing me to more progressive thoughts in the treatment of individuals with upper limb loss during my attendance of the 1997 Utah Arm Course; John Miguelez, CP, FAAOP, for his ongoing friendship and clinical mentorship since 1998; Randy Alley, CP, FAAOP, for his passion for the biomechanics and his questioning why we do what we do, which ultimately makes us better clinicians. The author is grateful to Julie Lake for her literary review and editing.
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Keywords:© 2008 American Academy of Orthotists & Prosthetists
upper limb; prosthesis; prosthetic socket; evolution of socket design; prosthetic material science; upper limb prosthetic specialist