Prosthetists and orthotists: An evolution from mechanic to clinician

Abstract

Fifty years ago, the International Society for Prosthetics and Orthotics was founded in recognition that this unique niche in rehabilitation would benefit from multidisciplinary interactions between specialists in engineering, therapy, and medicine.Since then, field evolved from having a craft orientation toward a technology and clinical specialty. This anniversary provides an opportunity to look back on advances in prosthetics and orthotics, and the clear impact they have had on changing the skills needed by the prosthetist/orthotist as new technology and techniques have emerged. The balance has clearly shifted from mechanical skills to clinical care. The training and skills of the prosthetist/orthotist remain unique and valued in the rehabilitation team, and the primary motivation remains the same as it has been since the creation of the International Society for Prosthetics and Orthotics: the application of external devices where they are suitable to address the many varied needs of persons with disability. This historical perspective puts into context why and how the profession has changed, while also reinforcing that it is the goals set for restoring patient functions that best defines what it is to be a prosthetist/orthotist, not the means we use.

What prosthetists/orthotists do and why the society was created

This year we are celebrating the 50th anniversary of the formation of the International Society for Prosthetics and Orthotics (ISPO). This milestone provides the impetus for this look back at both what has changed in prosthetics and orthotics (P&O) and a reflection on why it has changed. With this historical perspective, one can see more clearly the primary motivations that have defined P&O as a profession.At their core, prosthetists and orthotists have always been restorers of function, but historically they have often been thought of or confused with being mere purveyors of a broad selection of body supports. The “limb and brace shop,” as it was referred to commonly, was easily conflated with the local shoe store—a place to buy the right size device. There was respect for the craftmanship needed, apparent in the leather, wood, and metal work applied. However, the work of the prosthetist/orthotist has always been guided by something much more important and difficult than just crafting something fitting to wear and has always required much more than the obvious mechanical skills.

The essential work of a prosthetist/orthotist has always been to provide some ability that is missing, lost, or traumatically taken from a person. Fulfilling the functional needs of the unique patient was a necessity, the raisons d’être for the special skills of this field. The needs and wants of the unique person with disability guided construction of the devices that were created. Just as every patient was different, the orthotic and prosthetic devices created were also individualized. Today, we refer to these needs generally as desired outcomes. Through the provision of a prosthesis or orthosis, prosthetists/orthotists try to positively impact many facets of disability: among these are pain, posture, appearance, mobility, and self-efficacy. What may have been casually observed to be an effort to “fit” the patient with a generic object was actually the application of considerable creativity and the skills needed to enable specific improvements for a very complex and physically altered body. Even many of the medical professionals who sought assistance from prosthetists/orthotists did not always realize that the true nature of P&O services involved more than simply fitting a device.

In 1970, a group of physicians, surgeons, therapists, engineers, and prosthetists/orthotists, inspired by the shared experience of compassionately caring for generations ravaged by world wars, poliomyelitis, and thalidomide, established ISPO. They recognized the need to advance P&O as a distinct clinical rehabilitation profession and area of medical science. ISPO came into being as a vehicle that embodied a specific desire to address the challenges they shared, and to bring together the many disciplines needed to restore the person with disability in the unique ways facilitated by a prosthesis or orthosis.

Evolution and revolution

In any field of endeavor, evolution and revolution exist side-by-side, one does not obviate the other. They are different channels of the same river, one flowing consistently, almost imperceptible in movement, and the other tumbling through dramatic cascades. The evolution is best observed downstream where we can assess the flow for how it is forever renewed but seemingly little changed. The revolution grabs our attention at a dramatic point and makes us think that everything has changed in an instant, but downstream we see how that tumultuous channel rejoins the flow. It is a tributary, not a replacement of the whole. One can observe the transitions of P&O throughout the 50-year history of ISPO and recognize the gentle flow of change, but also that there have been several revolutions just in this era. These have had a profound impact on the once core skills applied by prosthetists/orthotists.

Evolution: mechanic, technologist, clinician

At the time ISPO was founded, it was still commonplace for the skilled artisans working in P&O to beat aluminum panels and bend bar stock, carve wooden sockets and knees and feet, and forge steel into custom articulations. Mechanical skills were considered a key measure of the mettle of the prosthetist/orthotist, appreciated for creating from raw materials, if necessary, exactly the device required.

Mastery of mechanical skills was essential then, but with time, increases in the application of technology in P&O have slowly altered the balance away from the use of mechanical skills and toward the use of clinical skills. The outcomes of the patient beyond their strictly mechanical needs should be considered equally by the prosthetist/orthotist. However, one should be cautious to not overly discount the usefulness of mechanical ability for contemporary prosthetists/orthotists. Complex biomechanical goals of force transmission and motion control must be interfaced mechanically with the organic form in creation of the physical embodiment of the prosthesis or orthosis.

As new technologies are introduced it has required prosthetists/orthotists to continually renew their knowledge and skills in order to be competent clinicians. They must be expert technologists with the acumen to appropriately match the form and function of available components with the patient. It has been said that in truly useful devices, form follows function. This refers to how the shape and performance of what is created is defined in part by what it is meant to accomplish. This is certainly evidenced in the mostly custom devices created by prosthetists/orthotists to match a patient’s unique needs. Yet, the provision of the physical technology does not completely define the role of the prosthetist/orthotist. To be successful technologists they must also have clinical training with skills such as those needed to evaluate muscle strength, range of motion, rehabilitation potential, and socioeconomic considerations. The prosthetist/orthotist is providing clinical care along a continuum, from the first evaluation of a patient’s health condition and needs, to follow-up assessment of long-term outcomes.

What is seen in contemporary P&O practice is not a wholesale replacement of the mechanical skills of the prosthetist/orthotist through mass production and electronics, but rather an overlay of understanding of new technologies and the additional clinical skills that are now integrated toward the ever-constant goal of maximizing function for patients.

Revolution: materials

Materials science has fundamentally altered the work of the prosthetist/orthotist. In 1984, I was part of the last class of prosthetists in my university to be formally taught how to use lead solder wire profiles as circumference and profile templates for carving out a block of willow wood to create a prosthetic socket. Even then, it was presented as an oddity, a tidbit of knowledge just in case there was call for that skill to care for a particularly old prosthesis. Soon after I entered practice, I was taught the method of creating contoured sockets from an aluminum sheet. In the decades preceding, these once core skills had already been replaced by widespread adoption of truly revolutionary ways of creating the interface: thermosetting resins and resin transfer molding techniques for composite sockets and drape molding of thermoplastics. While, since the genesis of the field, very functional prostheses had been fabricated using the old methods, the reasons for adopting new technologies involved more than just the alleviation of physically demanding labor and mechanical skills. They were innovations intended to enhance function in a myriad of ways. For example, thinner socket walls using the new techniques could be strong while being less obtrusive or damaging under clothes, a significant improvement for the patient. ¹

Motivated by the goal of improved patient outcomes, the prosthetist/orthotist adapted their skills to use these revolutionary materials. With new techniques, interfaces were easier to fabricate and easier to control as one could replicate a device from a rectified positive plaster of Paris model that could be incrementally improved. Wax-formed check sockets, subsequently improved with transparent thermoplastic, enabled visual inspection of the contact areas of the interface, leading to greater emphasis on precision of the interface fit and improved comfort for the user. Total contact sockets became the standard of care, alleviating the distension of unsupported tissue present in the older plug-fit socket designs.^2,3 The total surface bearing (TSB) transtibial socket design sought to disperse stresses from weight bearing through the amputated limb even more effectively. ⁴

Further addressing fit, thermoplastics requiring vacuum forming techniques were used to provide flexible interfaces which were in marked contrast to the static and often rigid supporting surfaces of earlier sockets. ⁵ The Icelandic-New York (ISNY) socket used this idea of a flexible interface contained by a fenestrated supporting shell. ⁶ The search for optimal interfaces led to creation of even more interfaces with elastomeric silicon, urethane, and thermoplastic all being added to the armamentarium of the prosthetist within a few years.

Revolution: modularization

The advent of modular components in the 1960s began a transition that allowed prostheses and orthoses to be constructed from mass-produced parts. ⁷ This also initiated what has probably been the biggest shift in the application of mechanical skills for the prosthetist/orthotist. No longer making all the elements of the device, prosthetists/orthotists were now assembling components. The prosthetist/orthotist became a consumer of technology, applying components to address the needs of their patients, while still pursuing the same goal of restoring function. The decreased time and effort required to create a device provided greater opportunity for prosthetists/orthotists to focus on other aspects of P&O care, such as the design of the interface to the patient and functional improvements. Prosthetic socket designs and plastic orthosis shells evolved quickly as a result. These innovations in practice brought about initiatives to train prosthetists/orthotists to be foremost a clinician who can evaluate patient functional needs and match those needs to commercial technologies.

Important clinical advancements were also facilitated by the adoption of modular components and a change from exoskeletal to endoskeletal constructions for prostheses. ⁸ Interchangeability of components promoted quick and easy experimentation with the latest available technology. For example, one could purchase knee units with different mechanisms for swing or stance control, and swap them in and out of the prosthesis at will. Alignment, a key facet determining dynamic function with a prosthesis, could easily be tuned to a fine degree in a matter of seconds. Realignment was previously a significantly more time-consuming process. Complicated devices like reciprocating gait orthoses (RGOs) were standardized as kits and made broadly available. ⁹ Centralized fabrication services have also been part of the evolution of prosthetists/orthotists moving away from the artisanal tradition of making everything themselves, by providing the labor for making custom devices only defined and measured, but not fabricated, by the clinician.

Availability of entirely prefabricated devices was first widely accepted for orthoses, but prefabricated prostheses are now found in certain applications as well. This is the natural extension of modularizing components and an extreme example of removing the creation of physical structures from the hands of the prosthetist/orthotist. How this revolution actually impacts the need for orthotists and prosthetists to have socket rectification skills is still unknown, as these devices are not yet considered standard of care. However, 30 years ago, many professionals similarly worried that Computer-Aided Design and Manufacturing (CAD/CAM) techniques would supplant the need for individual prosthetist/orthotist’s skills and lead to pharmacy-based ordering of computer-made devices. The skill set evolved for those who could wield a computer mouse as well as a rasp, but the result has not been the loss of our professional standing nor a reduction in the need for skilled prosthetists/orthotists. CAD/CAM has simply come to be used as a new tool by the same clinicians to fabricate the same devices they would have previously modified from plaster. ¹⁰

Revolution: functionality

A significant period in the development of the technology of P&O came with new startups that created dynamic elastic response prosthetic foot technologies that fundamentally improved patient function and satisfaction. Changing the prosthetic foot had an immediate and notable impact that exceeded what was achieved using previous technology. As the Kobe Steel Intelligent Knee first demonstrated at the 1989 ISPO World Congress, microprocessor control of knee function would prove a revolution that in time would become the standard of care. The same impactful change is evident in the current generation of composite dynamic orthoses, with gait improvements that have exceeded what orthotists achieved previously. ¹¹ These are all examples where the application of advanced technology provided functional improvements that the prosthetist/orthotist sought, but required new skills and training to evolve beyond traditional mechanical skills alone.

What may come?

What may come in the development of skills of the prosthetist/orthotist in the next 50 years? In an era where ubiquitous consumer technologies become obsolete in a few years, it becomes difficult to see far into a future of P&O abundant with more technology. We already see the use of connected mobile devices with apps that wirelessly convey new and helpful information about prostheses and orthoses to the clinician and patient. Can we assume P&O will change at the rate of the technological change generally? There will surely be revolutionary leaps ahead that we can hardly imagine today, and these will drive change. However, this is not our only path into the future. One might also predict that an increased emphasis on clinical science and quantifiable outcomes may dampen rapid changes in the profession. Science, unlike consumer demand, builds upon successes and failures that may take years or decades to recognize for what they represent to the advancement of knowledge. For changes built upon evidence, health technologies will evolve like biological systems, where generations of small changes can pass before species are transformed in an obvious way. Changes we might foresee in this way may not seem very ambitious to the futurist, but the past has shown that slow evolution can also be impactful.

As the profession seeks to continually advance the functional potential of those in need, skills to implement and interpret outcome measures that emphasize the holistic impact of P&O devices will also be important areas of development for P&O skills. The term patient outcomes is often used as if there exists a single thing called outcomes, but in reality the outcomes of any patient are many faceted. ¹² There is the patient’s essential perspective, “How am I doing?.” The prosthetist/orthotist has their own point of view, “Have we achieved all the function we can?” There are also perspectives of biomechanical efficiency and activities of daily living to consider. A new skill for prosthetists and orthotists will be to learn valid ways to both elucidate each perspective and subsequently integrate them into a holistic view of patient outcomes. Galileo Galilei is attributed with the quote, “Measure what is measurable and make measurable what is not so.” This is a worthy goal for improving all facets of function. Advancement in other disciplines has already been greatly impacted by instrumentation and laboratory testing for evaluation and diagnosis. Cardiologists have improved patient outcomes while evolving care with technology for ever-more precise evaluation: the stethoscope, electrocardiogram, Holter monitor, echocardiogram, and now machine learning–driven diagnostic software. We are already seeing the introduction of P&O-focused clinical instrumentation needed to quantify the impact of our devices to the point of making functional optimization based on science. From improved measurement and analysis, P&O care will become more precise and controlled. One such aspect is in dynamic alignment where it has been shown that with straightforward measurement of the kinetics of gait it is possible to systematically improve the gait of persons post-stroke using an ankle foot orthosis,^13,14 as well as persons post-amputation using a prosthesis.^15,16

The tenet that “less is more” is a statement of the inherent value in finding efficient solutions. In P&O, increased technology has usually meant greater complexity in the devices made, but there may be developments that require more skills and sophistication that result in a simpler prosthesis or orthosis. Some will posit that osseointegration of a prosthesis fits into this category as it completely eliminates the socket made by the prosthetist as a point of discomfort for the patient. Perhaps prosthetists will benefit from better understanding of bone physiology and infection control at the skin interface. Other interests will point to three-dimensional (3D) printing as also belonging to this concept because fully functional prostheses and orthoses can be achieved with simpler, lighter, and bespoke engineered structures; integrating desired functionality into the device’s structure instead of assembling it from modular components. The result is simpler for both the provider and the user. The prosthetist/orthotist will need new skills to successfully interact with such highly sophisticated engineering. It should be noted that neither osseointegrated prostheses nor 3D printing can be considered new ideas as both were successfully demonstrated decades ago,^17,18 reinforcing the potentially slow pace of adoption, even of revolutionary ideas with great promise.

Perhaps the greatest unsolved problem in interfaces for P&O is the means to communicate with both the afferent and efferent nervous systems.^19–21 To truly replace lost function to the greatest level, we must seek to interface with the whole person, allowing them to sense the environment in a natural way and to directly control motion of their body through volitional thought. P&O skills could someday require competency in use of neurological interfaces that will adapt artificial sensation and motor units to the intact nervous system.

The commonality of these exciting future advancements in P&O is that they all in some way reflect an expectation of the continuously increasing level of functional outcomes that could and will be achieved for those who are served by the profession.

Conclusion

The work of the prosthetist/orthotist when ISPO turns 100 will naturally be evolved further, but will no doubt be quite recognizable to us celebrating this 50th anniversary: a profession dedicated to restoring function through mechanical skills, the application of technology, and clinical care of the individual. To quote a personal mentor and colleague, Professor Arthur F.T. Mak, “P&O is the most clinical of all bioengineering disciplines.” Prosthetists and orthotists roles will likely further blur the boundaries of medicine and engineering as they evolve and continue to play a unique and vital role in the spectrum of rehabilitation sciences.