Upper Limb Adaptive Prostheses for Vocation and Recreation

Robert Radocy MS

Debra Latour OTD, MEd, OTR/L

Robert Radocy or an immediate family member serves as a paid consultant to or is an employee of Fillauer TRS Inc. Dr. Latour or an immediate family member serves as a paid consultant to or is an employee of Handspring, Liberating Technologies, Inc., and TRS Prosthetics.

ABSTRACT

Adaptive prostheses continue to evolve, expanding the choices for persons with a hand absence(s), enabling them to participate bilaterally and more competitively in challenging activities that can be vocationally, domestically, or recreationally oriented. Many adaptive prostheses and specially designed terminal devices provide multipurpose or crossover capability, offering reliable function and performance in unrelated activities. Multiple factors have created the stimulus for growth in this area of prosthetic technology, including changes in the Healthcare Common Procedure Coding System. In many cases adaptive components are more sophisticated, higher performance, nonanthropomorphic designs that emphasize function and biomechanics over appearance. Additionally, a growing variety of modern, quick-disconnect, vocationally oriented tools and domestic use implements are now available to meet patient needs. Also, a growing influence in individualized and custom designs is being created via computer-assisted design and additive manufacturing technologies leading to further innovations and more consumer-driven solutions. A broad array of sports and recreational adapters provide the opportunity for many persons with hand absence(s) to not only participate, but be competitive in activities ranging from archery to kayaking and weightlifting. Specific adaptive solutions for many activities are explored in detail.

Introduction

The term “activity specific” began to replace the general reference for sports and recreational prosthetic adaptations during the late 1990s.¹ Activity-specific or adaptive prostheses currently refer to a wide range of designs that serve vocational, domestic, and sports and recreation pursuits. Certain of these designs have evolved into true “crossover” devices, as consumers have successfully applied the technologies to activities beyond the original intention. The broadened “crossover” usage can help the justification for prescribing activity-specific designs. These types of devices can differ from traditional prostheses in a variety of ways. Replicating correct human hand or upper limb anatomical features is not the primary goal of these components. Rather, the design emphasis is on duplicating precise upper limb biomechanics and in many cases rigorous high-performance function. The adaptive prostheses are designed and constructed to enable the user to achieve higher levels of competency and performance in specific activities where traditional body-powered and/or myoelectric (externally powered) technologies do not perform well.

Early commercialized designs for activity-specific terminal devices such as the Hosmer Bowling Ball Adapter and Baseball Glove Adapter date back to the 1950s. Between the 1950s and the early 1980s development remained stagnant, except for a prosthetic golf TD that was built on a limited basis and sold by Robin-Aids of northern California.² In 1983 the TRS Super Sport Hand was introduced. Most commercially available, innovative activity-specific prosthetic adaptations were introduced in the 1990s. Around the turn of the new millennium the demand for quality, commercially built adaptive devices finally began to grow.

Published articles and educational textbooks on the topic of activityspecific-type prosthetic technology are somewhat limited but relevant literature exists.³^,⁴^,⁵^,⁶^,⁷^,⁸^,⁹^,¹⁰^,¹¹ It is not uncommon for an occupational therapist (OT) to fabricate an implement and attach it to a universal cuff to help people with upper limb absence to participate in meaningful activities. More often, the OT might collaborate with the prosthetist to help the person acquire a specific TD or adaptation to existing prosthetic technology. The activity-specific terminal device is typically static and attaches
to the forearm unit at the wrist. This technology often is robust, lightweight, and offers quick release. It typically does not require harnessing or cables and is low maintenance. The activity-specific prosthesis is often suspended with a pin-lock style of liner or a neoprene sleeve. This design configuration allows participation and improved performance during specific activities such as personal care tasks, cooking, woodworking and gardening, and diverse recreational activities.¹⁰

A multitude of forces and events have contributed to the development of adaptive prostheses. Beginning in the 1970s, individuals with physical challenges became more visible in the public and the public became more accustomed to seeing persons with prostheses taking on sports challenges such as snow skiing. The birth and growth of adaptive ski programs in the United States and abroad have significantly raised the exposure levels of those with a limb absence. Simultaneously, college educational programs began to progress in the disciplines of Physical Education, Adaptive Sports, and Therapeutic Recreation creating trained professionals with an academic focus on these topics. This influence has trended on a global level with the recommendations of the World Health Organization focusing of wellness, well-being, and preventing further disability.

In the 1980s and into the early 1990s, the entrance into the prosthetic industry by two entrepreneurs, who themselves were individuals with upper limb absence, led to the creation of viable commercialized businesses oriented toward manufacturing and selling “standardized” activity-specific prosthetic components. The designs of Therapeutic Recreation Systems (TRS Inc. now Fillauer TRS, Inc.) were primarily oriented toward adaptive sports and recreation technology, while Texas Assistive Devices (TAD) targeted the design and development of specialized hand tool attachments and domestic-use implements. These technologies were designed to enhance the functional capabilities of the prosthesis user, allowing them to be more competitive in two-handed tasks and believing that there was no need to be limited by current prosthetic technology.

In addition, the benefits and values of sports and recreation in the rehabilitation program have continued to be recognized. The healthful benefits of physical activity are well-known for persons without limb absence and seem to be even more relevant for people with limb absence. Numerous authors have associated positive self-esteem with participation in sports and other meaningful recreational pursuits. Wearing and using a prosthesis affords the person with upper limb absence the opportunity to participate in such pursuits, and to perform to their best ability. These factors directly influence one’s self-identity, self-esteem, and self-concept. Murray found that to prosthesis users, the prosthesis may be more than a tool, and that with mastery, it may correlate with self-identity.¹² He suggested that the valued personal identities and the self-management of patients’ ability status should be a priority for the health professionals involved in prosthesis users’ medical care and personal development.

The evolution, growth, and popularity of national disabled sports organizations such as Disabled Sports USA and Adaptive Sports USA (now merged as Move United), the National Amputee Golf Association, and Physically Challenged Bowhunters of America, and many other organizations, have also fueled the interest in these adaptive prosthetic technologies. The creation of specialized competitions and “Games” for the physically challenged athlete all have contributed to the growth and interest in activity-specific prostheses. The development of the Paralympics in the late 1980s gave credence to the overall challenged athletic movement and increased interest in activity-specific or adaptive prosthetic technologies. The allowance for use of an upper extremity prosthesis in all the Paralympic sports still does not exist. Potentially, in the future, “classes” of competition will be created to eliminate this restriction for certain physically challenged athletes, allowing them to perform at even higher levels, using prosthetic technology.

Improved representation and exposure for athletes with upper limb absence and peer role models via national organizations such as the Amputee Coalition, the Challenged Athletes Foundation (CAF), and others has helped to expand information and communications between prosthetic users interested in sports pursuits and new adaptive technologies. The general explosion of communications, information, and data via the internet and social media have opened and created interest in new prosthetic technologies.

The demands placed upon the military’s rehabilitation hospitals such as Walter Reed in Washington, DC, Brooks Army Medical Center (BAMC) in San Antonio, Texas, and Balboa Naval Hospital in San Diego, CA, by young, strong, but physically traumatized soldiers returning from the wars in Iraq and Afghanistan have played an important role in driving the development of new and innovative prosthetic designs. These military facilities have created state-of-the-art programs that have actively integrated sports reconditioning, for the first time, into our soldiers’ comprehensive rehabilitation.

Insurance companies and vocational rehabilitation agencies have begun to realize the health values and psychological benefits of adaptive prosthetic technologies in the insured’s rehabilitation scheme. Reimbursement for the provision of activity-specific or adaptive upper extremity prosthetic technology has expanded and improved but is still not adequate to meet the needs of those with limb absence. Insurance companies appear to see value in prosthetic technology that allow functional outcomes in personal care, home management, community access, and vocational activities. While many of these same companies incentivize members with access to gym clubs and weight loss programs, they do not pay for recreational devices that would enable the person to participate. Some activity-specific recreational devices offer “crossover” functions so that the user may access recreation and/or sports endeavors as well as
functional tasks that require similar biomechanics. For example, a device used for bicycling may also be used to grasp the handles of a shopping cart, a stroller, lawnmower, or snow-blow, and thus enhance the functional envelope of the technology. Table 1 depicts specific devices that offer cross over functions.

Importantly in 2009 Healthcare Common Procedure Coding System (HCPCS) revised numerous upper extremity L Codes via the Durable Medical Equipment Coding System (DMECS), creating Code: L6704: Terminal Device, Sport/Recreational/Work Attachment. Any Material, Any Size that provided coverage and reimbursement for terminal devices designed for specialized work and sports and recreational activities. Creating this code was an important step for HCPCS in recognizing the importance and value of activity-specific or adaptive prosthetic technology in the overall rehabilitation spectrum for persons with an upper extremity limb absence.

TABLE 1 Activity-Specific Devices With Crossover Function

Device	Action	TRS Design Use	Crossover Function
Criterium series	Grasps handles with small to medium diameter Pivot allows steering, improved control	Biking (road and flat land)	Pushing/pulling Sweeping/raking Steering
Dragon	Aperture in device absorbs forces and captures cylindrical handles Loosely interacts with objects Allows freedom of movement	Martial arts	Home management Property management Climbing Steering
Helix	Molded, high-performance, polyurethane. “DNA” helical shape replicates holding action of the hand in the control of short or long cylindrical handles grips. Unique strength and flexibility “feels” like the hand and forearm with “reflexive,” energy capture, storage, and release action	Especially useful in any activity-specific task that uses long handles or “sticks” like lacrosse, hockey (ice, street, field)	Vocational-avocational prosthetic device Especially useful in any activity-specific task that uses long handles, such as rakes, shovels, as well as smaller garden tools, water hose control Many undiscovered uses
ISHI and F˜ISHI	Adjustable grasp Secure, stable with strap	Archery, fishing	Grooming Holding handled objects
Multi-D	Adjustable grasp Secure, stable with strap Larger More robust	Multipurpose	Home management Yard work Holding larger handled objects Fishing (salt water)
Raptor	High strength, “large *#7” shaped titanium lifting and supporting terminal device with replaceable, protective tip for cushion and nonmarring applications and greater friction control over surfaces. Unique pivot action increases versatility in lifting, supporting, climbing, etc.	Indoor and outdoor rock and gym climbing	Heavy-duty lifting and transport and loading tasks Handling/lifting veneer woods, panels, or similar
Swinger	Loosely interfaces with objects Allows freedom of movement	Gymnastics	Carrying Climbing Steering Fishing
Adapted with permission from Fillauer TRS, Inc. TRS High Performance Prosthetics Product Catalog. TRS Prosthetics, January 2019. https:www.trsprosthetics.com/wp-content/uploads/2019/01/Web-Catalog-JANUARY2019.pdf.

Another factor related to the growth and popularity of activity-specific prosthetics is cost and affordability. Bionic technology appears to have captured the attention of the media and public. However, the reality for some users of such prostheses is that their higher cost is associated with lower performance and less reliability, and they may be neither affordable nor provide practical solutions to daily demands. Bionic-electric prostheses are not capable of reliable performance in most sports pursuits or in certain vocational activities with demanding bimanual skill requirements. Activity-specific technologies are far more affordable and have a much higher level of reliable function and performance for targeted activities than electric prostheses. The adaptive prosthesis can, however, compliment and augment the capability of externally powered prostheses that might otherwise be used in inappropriate environments or for inadvisable tasks. The activity-specific prosthesis is robust and well-suited to physical, functionally demanding vocational and avocational pursuits, while the bionic or myo-electric limb can be complimentary and complete other important user functions where dexterity or appearance may be indicated.

Prosthetic Interfaces and Limb Design

Activity-specific prostheses are typically used in either high-force/stress or high-performance environments and therefore require a socket (interface) design and construction that is extremely comfortable, while providing high levels
of pressure tolerance and exceptional suspension. The prosthesis is typically constructed using light-weight carbon fiber or equivalent materials and special bonding resins that provide high strength. Other chapters of this Atlas concentrate specifically on aspects of prosthetic design and fabrication. The relevant, important factors to emphasize are secure suspension, adjustable compression, residual limb comfort under both static and dynamic loads, range of motion (ROM), physical weight, structural strength, and prosthesis length and alignment.

Suspension

Depending upon the limb morphology there are currently a variety of options to achieve a secure prosthetic suspension. The prosthetic platform could start with a well-designed self-suspending socket that enhances comfort with a partial liner or custom-fabricated silicone or polymer liner which at a minimum encompasses the medial and lateral epicondyles and olecranon. Locking liners should always control for longitudinal stretch in an upper extremity socket if secure suspension is to be maintained. Suction suspension can also augment prosthetic stability and security. A short residual limb prosthesis can be enhanced for load bearing by extending the rear brim of the socket to distribute load to the back of the humerus. Socket security can be augmented with REVO-LIMB type technology that uses BOA tension system mechanisms as illustrated by two current adjustable compression socket designs (Figures 1 and 2). Socket design can pattern any number of proven technologies, such as TRAC,¹³ ACCI,¹⁴ HI-FI,¹⁵ or variants thereof depending upon the patient’s needs and requirements. Suspension technology continues to evolve.

Load Bearing and Comfort

The socket should be tested under both static and dynamic loads on the patient to ensure that no painful pressure “pinpoints” exist that will make the socket intolerable under dynamic load. While liners can help cushion load, they will not take the place of a properly modified socket that creates secure suspension but still provides for the movement of the olecranon and condyles throughout complete elbow-forearm flexion ROM. A professionally designed socket should provide enough comfort and security for the patient to conduct a “pull-up” or “push-up” without creating debilitating pain in the socket.

FIGURE 1 A and B, Clinical photographs of self-suspending forearm prosthesis incorporating BOA technology fabricated by Chris Baschuk, CPO, of Handspring and illustrating a removable cover and a rear compression plate that captures the olecranon. (Courtesy of Fillauer TRS, Inc.)

Physical Weight and Structural Strength

While lighter is not always better, a lower weight prosthesis is typically preferred provided strength is not sacrificed. Materials such as woven carbon fiber or its equivalent fabricated with appropriate, compatible high-strength resins in both the socket and forearm of the prosthesis should provide a reliable limb for use in almost any activity. Materials and resins continue to evolve to improve socket integrity. Additive manufacturing technologies are beginning to play a role in custom socket and prosthesis construction. In certain cases, these prostheses can provide a reliable outcome for certain individuals and activities. However, at this point in its history and development, this is somewhat “unknown territory,” and caution is a good prescription regarding relying on such prostheses for
high-performance activities until the reliability and structural integrity of such materials in definitive prostheses have been substantiated. Advances in additive manufacturing and new materials technology, applied by trained, certified prosthetic professionals, may ultimately compliment or replace existing techniques and technology for fabricating prostheses.

FIGURE 2 A and B, Clinical photographs of forearm prosthesis illustrating BOA technology with and without cover by Dave Rotter CPO, Dave Rotter Prosthetics, LTD, that captures the short forearm with flexible cable-controlled brims that tension together supporting the medial and lateral epicondyles. (Courtesy of Fillauer TRS, Inc.)

FIGURE 3 Clinical photograph of short sports swimming prosthesis using Hi-Fi technology built by Randy Alley of Biodesigns, Inc. (Courtesy of Fillauer TRS, Inc.)

Prosthesis Length

The length of the prosthesis may not necessarily need to conform to the normal limb. There are certain load control and biofeedback benefits to the user that can be achieved by shortening the overall length of the prosthesis and either bring the TD closer to the remnant limb as in this custom, swimming prosthesis (Figure 3) or using the shortened prosthesis as a more stable platform for a high-performance flexible TD connector such as this trans-humeral golf prosthesis design (Figure 4).

Another technique that has seen positive functional outcomes is to attach a musical instrument prosthetic accessory directly to a roll-on locking liner (Figure 5). The intimate fit of this type of liner magnified by its compliance enhances “sensitivity” and control over the musical instrument accessory. The musical adapter is much closer to the end of the limb in this design. The feedback and “feel” that are created are not inhibited, mitigated, or shielded by the outer shell of a prosthesis. Higher levels of sensation can be experienced between the instrument and the musician.

FIGURE 4 Clinical photograph of forearm prosthesis illustrating trans-humeral golf prosthesis. (Courtesy of Fillauer TRS, Inc.)

Alignment

Specific activities such as archery or weightlifting can dictate that prosthesis alignment be factored into the design to achieve optimal performance. End weight-bearing and balance are directly impacted by the degree to which the forearm of the prosthesis is “preflexed” from the socket. The wrist mounting angle also impacts load bearing and can impact performance. Typically, a more neutrally aligned prosthesis (minimal preflexion) should be considered for better performance in sports activities where a significant amount of gross motor motion is occurring or to help the stabilization and control of heavy loads placed upon the prosthesis, such as in weight training, archery, kayaking, etc. A more neutral socket to forearm alignment will help facilitate a greater ROM and more comfort and better control for the user.

FIGURE 5 A and B, Clinical photographs of forearm Roll-On Locking Liner with Guitar Pick Adapter. (Courtesy of Deb Latour, Med, OTR/L.)

Activity-Specific (Vocational-Domestic) Technology

Direct prosthetic tool and implement technology is far from being a new idea. In medieval periods certain well-to-do knights and royalty, who had lost a limb, were fitted with a creative prosthesis equipped with an integral dagger, sword, or eating implement.¹⁶ In the 21st century the concept has experienced a rebirth, and the validity and viability of such designs continues to grow. TAD has engineered direct tool and implement attachment to an art form, continually expanding on the number of tool and implement options that are available (Figures 6 and 7). The initial inspiration in developing adaptive prosthetic components arose from a passion for cooking and frustration with being unable to adeptly handle carving knives. Voluntary opening split-hook prostheses could not capably or safely handle chef’s knives and other cooking utensils and implements. In response, the field began to develop a line of highly functional adaptive tools. These devices were complimented by
the evolution of a novel product called the N-Abler, developed TAD in the early 1990s. The N-Abler was a multifunction wrist interface that connected the tools and implements into the prosthesis. The N-Abler allowed for precise flexion and rotation of the “tool” in ways not possible before. The N-Abler technology has now evolved into a family of five-function wrists. These wrist components have created the opportunity for persons to accomplish activities that they could not competently complete before. These technologies are particularly beneficial to persons missing both hands or presenting with partial hands bilaterally. The TAD adaptive components make the individual’s work efforts more productive, expending less energy, and improving efficiency. The therapeutic results and benefits of these successful accomplishments include improved independence, self-esteem, and quality of life.

FIGURE 6 Clinical photograph of forearm prosthesis illustrating Texas Assistive Device’s (TAD) working tool attachments. (Courtesy of TAD.)

FIGURE 7 Clinical photograph illustrating Texas Assistive Device’s (TAD) domestic use prosthetic adaptations. (Courtesy of TAD.)

Activity-Specific (Avocational) Adaptive, Sports, and Recreational Technology

The interest in prosthetic sports and recreation, adaptive terminal devices has grown significantly since the beginning of the 21st century. The diverse designs provide people with hand absence better access to sports, and in many instances, a solid platform from which to compete with two-handed peers. The key to achieving competitive, high-performance capability in sports and recreation is an emphasis and focus on designing prostheses that replicate the natural biomechanics required to perform an activity. In many cases this is achieved by providing improved ROM of the forearm and wrist well beyond the single plane or biplanar motion that traditional prosthetic construction and wrist systems provide. Additionally, greater emphasis has been placed upon generating and capturing externally developed energy during the activity’s execution and transferring that energy through the torso into the upper extremities and down into and through the prosthesis and terminal device. Capturing the natural “back swing” energy created by the mass and momentum of a golf club during a golf swing, or a baseball bat during a bat swing, then controlling it through the swing cycle and releasing that energy at the appropriate time not only enhances the performance of the activity but provides the prosthetic user with a continual, intimate, biofeedback that can help to improve control over the activity.

Consumer involvement in the development of activity-specific prostheses has been paramount to the success and growth of technology in this segment of the upper extremity prosthetics market and led to vast increases in persons with a hand absence using
a prosthesis in a wider range of physical challenges. The Mill’s Rebound TD and Hoopster TD, both for basketball play, were both conceived by consumers. TRS took those initial concepts and refined them into producible products with standardized, reproduceable manufacturing practices. The Black Iron Master (BIM) resulted from the request of a semipro body builder,¹⁷ who had lost his hand in an auto accident. The BIM provided the technology and generated the confidence that the individual needed to return to competitive weightlifting and win a world title in bench pressing, competing against able-bodied peers. The Swinger was designed in cooperation with a child and her father over a year timeframe, allowing her to perform inspiring feats on the uneven parallel bars, again competing with able-bodied peers. The Freestyle Swimming TD concept evolved directly from a Canadian Prosthetist’s patented design. The diverse climbing TDs were codeveloped with input and testing by two well-known, one-armed climbers. The KAHUNA was requested and created for the Navy’s Balboa Rehabilitation. Both the HAMMERHEAD and LAMPREY GUN TURRET were created at the request of personnel from Walter Reed Hospital. The value of such collaboration is difficult to measure but without it most likely the development of these products, that have proved so inspirational and valuable to hundreds of physically challenged athletes, may never have occurred.

Murray¹⁸ explored factors about the social meanings of prostheses use, and particularly sought perceptions of prosthetic limb users. His findings revealed several themes such as actual prosthesis use, social rituals, user perceptions of social isolation, reactions of others, social implications of concealment or disclosure, and perceptions or experiences about social and intimate relationships. Factors that influence adjustment and successful rehabilitation were early prosthetic fitting, prosthetic satisfaction associated with increased self-esteem, increased social integration and absence of emotional challenges, and the need for individual expression including social expression, person-first language, societal acceptance, and personalizing the appearance of the prosthesis.

Preprosthetic Exercise

Preprosthetic conditioning or exercise without a prosthesis can be valuable to the person with a hand absence, especially in cases where traumatic injury or burn has created sensitive skin surfaces or scar tissue that cannot tolerate the potential shear forces created by a prosthesis. Exercise straps and elastomer exercise bands, custom harnesses supported by triceps cuff suspension techniques (Figure 8), or type harness systems can provide the ability to exercise in a wide ROM through most body zones, challenging atrophied muscles and stiffened joints. The CARTER CUFF is an example of one of the first commercialized exercise technologies developed specifically for those with a hand absence who are interested in higher performance resistance exercise training without a prosthesis. The TRS SWIM FIN is a kit system that does not involve a prosthesis and has been successfully applied by therapists for resistance exercise conditioning during pool therapy. Providing additional resistance to the affected limb helps improve the shoulder ROM and strengthen shoulder and arm musculature without the aggravation and load bearing of a prosthesis.

FIGURE 8 Clinical photograph illustrating trans-radial exercise harness. (Courtesy of Fillauer TRS, Inc.)

Preprosthetic exercise can help prepare an individual for the therapeutically valuable exercise that resistance training with a prosthesis can provide. Therapists and prosthetists often may collaborate to prepare the individual to tolerate wearing the prosthesis and use it independently for daily activities using prosthesis simulator technology. In this way, the individual can become accustomed to the weight and length of the device, the feeling of the socket and the harness, and the functional workings of the components.¹⁹ TRS developed a prosthesis simulator that offers access to both body-powered and static activity-specific devices.

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