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544 MOBILITY AIDS

BIBLIOGRAPHY

1.Ball K, Endoscopic Surgery. St. Louis: Mosby Year Book; 1997.

2.Holland P, The Fundamentals of Flexible Endoscopes, Biomedical Instrumentation and Technology. Association for the Advancement of Medical Instrumentation, p 343–348, Sep./ Oct. 2001.

3.Webster J G, ed. Minimally Invasive Medical Technology. Institute of Phys Publishing Ltd., 2001.

4.Spera G, The Next Wave in Minimally Invasive Surgery, Medical Device and Diagnostic Industry, Canon Communications, August 1998.

5.Gill B, Navigation Surgery Changing Medical Device Development, Medical Device and Diagnostic Industry, Canon Communications, December 2004.

6.Scuderi R G, Tria A J, eds., MIS of the Hip and the Knee: A Clinical Perspective; New York: Springer-Verlag, 2004.

7.Puskas J, et al. Clinical outcomes and angiographic patency in 125 consecutive off-pump coronary bypass patients. Heart Surg Forum May 1999;2(3):216–221.

8.Spera G, The kindest cut of all, Medical Device and Diagnostic Industry, Canon Communications, July 1998.

9.Technology Trends: Radiation System Could Be an Alternative to Surgery, Biomedical Instrumentation and Technology, Association for the Advancement of Medical Instrumentation, p. 18, January/February 2005.

10.Comarow A, Tiny holes, big surgery. U.S. News & World Report, July 22, 2002.

11.Bosch F, Wehrman U, Saeger H, Kirch W. Laparoscopic or open cholecystectomy: Clinical and economic considerations. Eur J Surg 2002;168(5):270–277.

12.Conseil d’evaluation des technologies de la sante du Quebec (CETS). The Costs of Conventional Cholecystectomy, Laparoscopic Cholecystectomy, and Biliary Lithotripsy. Montreal: CETS, 1993.

13.Oz M, Goldstein D, Minimally Invasive Cardiac Surgery. Humana Press; 1999.

See also ENDOSCOPES; GAMMA KNIFE; MICROSURGERY; STEREOTACTIC SURGERY; TISSUE ABLATION.

MOBILITY AIDS

RORY COOPER

ERIK WOLF

DIANE COLLINS

ELIANA CHAVEZ

JON PEARLMAN

AMOL KARMARKAR

ROSEMARIE COOPER

University of Pittsburgh

Pittsburgh, Pennsylvania

INTRODUCTION

The National Center for Health Statistics estimates that 12.4 million adults are unable to walk a quarter of a mile in the United States, and that 28.3 million adults have moderate mobility difficulty (1). Approximately 4 million Americans use wheelchairs, and about one-half of them use their wheelchairs as their primary means of mobility. About 1.25 million people wear a prosthetic limb due to injuries, birth anomalies, and disease. Once fatal injuries are now survivable due to advancing medical achieve-

ments, prolonging life spans, and the staggering growth in the aging population. Because of this growth, the population of individuals who use mobility aids is sure to grow in the coming decades.

The goal of issuing wheelchairs, prosthetics, walkers or rollators to individuals with mobility impairments independence remains the top priority when prescribing one of these devices, other main concerns include safety, not causing secondary injury (i.e., pressure sores, carpal tunnel syndrome, rotator cuff tear), and the physical design of the device (e.g., weight, size, ease of use). Research has shown that manual wheelchair users commonly report shoulder, elbow, wrist, and hand pain (2). Low back pain and fatigue are also common secondary ailments experience due to exposure of whole-body vibrations (3). Safety research shows that proper fitting and wheelchair skill can reduce injurious tips and fall in wheelchairs (4).

In order to fully maintain an active lifestyle, including recreational activities, participating in the community, and going to work, transportation for people with mobility impairments is essential. With the added technology that is necessary to allow people to use public or private transportation, added safety features must also be included to maintain the security of both the drivers and the passengers.

Besides performing normal activities of daily living, sports, and recreational activity are an important physical and psychosocial aspect of any human being. The case is no different with people who use assitive technology. With dramatic advances in technology, people with mobility impairments are able to go places and participate in activities that were once nearly impossible.

In recent years, wheelchairs, prosthetics, walkers, and rollators have been designed to be stronger, safer, lighter, more adjustable, and smarter than in the past, through the use of materials like titanium and carbon fiber, using advanced electronics, and so on. The technology of wheelchairs, prosthetics, walkers, and rollators has improved dramatically in the past 25 years due largely in part to the increased demand of consumers, their loved ones and others who assist consumers, and the people who recommend and issue these technology devices. The term"recommend’’ is used because it is crucial that these devices, especially wheelchairs and prosthetics, be issued by a team of professionals to provide the highest levels of independence and safety, and that this team is centered around the client. All of these components are important to the further development of the technology and, in turn, they may result in the increased independence of people with mobility impairments.

CLINICAL ASSESSMENT OF MOBILITY

The ultimate goal and outcome for a clinical assessment of mobility should drive toward a successful wheelchair, prosthetics, walker, or rollator recommendation that enhances the quality of life expectations and their effectiveness as reported by the consumer. Quality of life is specific to and defined by each person and/or family receiving clinical services. The consumer, their family, and care

givers, must be actively included in this process, as they will be most affected by the choice of the mobility aid. Also, people chose their mobility devices based on the features available that facilitate activities or address needs (5), and the clinician should be aware of the consumer preferences and the features of various devices.

The complexity of some of the mobility device components combined at times with involved disease processes can make it virtually impossible for a single clinician to act independently when recommending assistive technology. Therefore, involving an interdisciplinary team is recommended in the decision making process (6,7). This team, with the consumer as an involved member and a variety of rehabilitation professionals, includes a physiatrist or similarly trained physician who understands the importance of Assistive Technology, addresses medical issues and assists with mobility decisions; the Occupational or Physical Therapist with RESNA (www.resna.org) certified Assistive Technology Practitioner (ATP) credentials, who is the point person for evaluation and prescription; and the Rehabilitation Engineering (with RE Training and RET Credential) who is a technology expert with the ability to design– modify–tune devices, and who also understands the capabilities and applications of various technologies. Another important team partner is the Assistive Technology Supplier (ATS) or Certified Rehabilitation Supplier (CRTS, National Association of Rehabilitation Technology Suppliers, www.narts.org), who provides or manages demonstration equipment, does routine home and workplace assessments, and orders, assembles, and delivers the equipment. All team members involved in the mobility aid selection process should have knowledge about the technology available on the market. Peer reviewed journal articles (Assistive Technology, Archives of Physical Medicine and Rehabilitation, Journal of Rehabilitation Research and Development etc.), magazine articles and commercial database sources such as ABLEDATA (http://www.abledata.com/), or WheelchairNet (www.wheelchairnet.org) are good places to research devices or to direct consumers who want to inform and educate themselves.

Resources available to the team and its members includes a defined and dedicated space for demonstration equipment, assessments, and evaluations, access to common activities and tasks (e.g., ramps, curb cuts, bathroom, countertop), an electronic tracking system to follow clients

and their technology, assessment resources (e.g., pressure mapping, SMARTWheel, gait force plate, actigraph), IT

Resources (e.g., email, web, databases, medline, paging, cell, wireless), and the facilities–hospital commitment to continuing education.

A mechanism for Quality Measures for AT Clinics will provide valuable feedback on performance quality and areas in need of improvement. An important tool to measure patient satisfaction is the information gained through a satisfaction survey provided to every patient, in order to find out whether the goals and desired outcomes have been met. Feedback on performance quality is provided through tracking mechanism of primary clinician credentials (ATS, ATP, RET), dedicated staffing levels, continuing education (CEUs and CMEs), compliance with the commission on Accreditation of Rehabilitation Facilities (CARF) AT Clinic

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Accreditation, as well as tracking of continuous quality improvement.

Assessment

The occupational or physical therapist conducts the initial assessment process and obtains critical information about the consumer and their environment. This part usually involves a structured interview with the consumer and then a physical motor assessment. Establishing a medical diagnosis that requires the mobility aid is vital to assure no ongoing medical problems exist that are not being adequately addressed. To properly specify a mobility device, the intentions and abilities of the consumer must be ascertained (8,9). The intentions and abilities may include how people perform tasks, where the deficits are, and how mobility systems can compensate for the deficits to augment task performance. Some outcome tools that are clinically used to measure the functional impact of mobility aids are the QUEST, the FEW and the Wheelchair Skills Test (WST).

Additional necessary information includes type of insurance, method of transportation, and physical capabilities. Also, if the consumer has been using a chair, historical information about their current chair should be addressed, including problems they are having. The mobility device chosen should also be compatible with the public and/or private transportation options available to the consumer, such as a bus, car, or van. The regularity of the surface, its firmness and stability are important, when, for example, recommending a wheelchair in determining the tire size, drive wheel location, and wheel diameter. The performance of a wheelchair is often dictated by the need to negotiate grades, as well as height transitions, such as thresholds and curbs. The clearance widths in the environment will determine the overall dimensions of the wheelchair. The climates the chair will be operated in, and the need to be able to operate in snow, rain, changing humidity and temperature levels, and other weather conditions, are important considerations as well.

A physical–motor assessment of strength, range of motion, coordination, balance, posture, tone, contractures, endurance, sitting posture, cognition, perception, and external orthoses is an important first step to obtain a basic understanding of an individual’s capacity to perform different activities. The history likely provided significant insight related to their physical abilities. To verify this, a physical examination should focus on aspects of the consumer that (1) help justify the mobility aid, (2) help determine the most appropriate mobility aid, and (3) assure that medical issues are appropriately addressed.

Once the examination documents the need, or potential lack of need for the mobility device the remainder of the examination can focus on the appropriate technology. This is best assessed by giving the consumer the opportunity to try equipment to determine how functional and safe they maneuver/operate the device within the clinical space. During this part of the assessment, the consumer and family must be informed of the positive and negative characteristics of devices and services. The team needs to educate the consumer or family to participate in

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choosing the device that will meet their needs (Locus of Control) and assure the provision of follow-up services.

The in-home evaluation conducted by the ATS verifies that the device is compatible and will fit within the home environment of the consumer; that may also included recreational and work environment. Once the appropriateness of a device is established, final measurements are taken. For many people, a few simple measurements can be used to determine the proper dimensions for a wheelchair (10). Body measurements are typically made with the consumer in the seated position. A Rehabilitation Technology Supplier, therapist, or other member of the rehabilitation team often completes this.

MANUAL WHEELCHAIRS

When most individuals think of manual wheelchairs they envision the boxy, steel framed, standard wheelchairs commonly seen at airports and shopping malls. These wheelchairs may be acceptable for transport of short distances, but are good for little else. Their heavy weight and complete lack of adjustability makes them poor choices for anyone using a manual wheelchair for an extended period of time.

The development of the lightweight and ultralight wheelchairs evolved in the late 1970s with a select few, extremely motivated, manual wheelchair users choosing to perform modifications on their own wheelchairs to make them faster and easier to propel (11). After these initial steps the demand became far greater for lightweight, adjustable wheelchairs and several companies were created to meet that need.

Research conducted on the new lightweight and then ultralight manual wheelchairs have quantitatively shown the benefits over the heavier, nonadjustable standard style wheelchairs. Cooper et al. (12) reported that when subjected to the fatigue tests described in the ANSI/RESNA standards, ultralight manual wheelchairs were 2.3 times more cost effective than lightweight wheelchairs and 3.4 times more cost effective than depot style wheelchairs.

The benefits of lightweight and ultralight manual wheelchairs do not end with higher cost efficiency and longevity. They are also crucial in preserving the upper extremities of their users. Because of the constant use of the upper extremities by manual wheelchair users, they tend to experience secondary injuries such as joint pain, repetitive strain injury, and nerve damage (2). Compared to standard and lightweight wheelchairs, the ultralight

wheelchairs have two very distinct advantages when attempting to prevent secondary injury in manual wheelchair users: the primary advantage is the lower weight (Fig. 1).

Standard style wheelchairs tend to be greater than 36 lb(16 kg), while lightweight wheelchairs tend to be30–34 lb(14 þ 18 kg) and ultralight wheelchairs 20– 30 lb(9–14 kg). The second advantage presented by the ultralight wheelchairs is adjustability. Lightweight wheelchairs do have some adjustability, but not to the extent of an ultralight wheelchair. Masse et al. (13) showed that moving the horizontal axle position toward the front of the wheelchair and moving the seat downward created a more efficient position for wheelchair propulsion and resulted in less exertion without loss of speed. Although some studies have been conducted to asses the importance of wheelchair setup in reducing upper extremity injury in manual wheelchair users, the solution has not been clearly defined. However, what is certain is that the adjustability and weight of manual wheelchairs are crucial parameters when selecting a wheelchair for a user that will be propelling for extended periods of time.

Another recent addition to manual wheelchairs has been suspension elements, such as springs or dampeners to reduce the amounts of vibration transmitted to manual wheelchair users. During a normal day of activity for a wheelchair user, they encounter bumps, oscillations, and other obstacles that may subject them to whole-body vibration levels that are considered harmful. VanSickle et al. (3) demonstrated that when propelling over certain obstacles, vibrations experienced at the seat of the wheelchair and the head of the user exceed the safety levels prescribed by the ISO 2631-1 Standard for evaluation of human exposure to whole-body vibration (14). Wheelchair companies have attempted to reduce the amounts of transmitted vibration by adding suspension to manual wheelchairs. Research has been done to evaluate effectiveness of suspension at reducing vibration. Results show that on average, suspension does reduce the vibration levels, however, the designs are not yet optimally effective and may not be as effective based on the orientation of the suspension elements (15,16).

POWERED ASSIST WHEELCHAIRS

Often, people using manual wheelchairs are required to transition to using powered wheelchairs or are at a level of capacity where they must choose between the two. This may be because of increased amounts of upper extremity

Figure 1. (a) Standard, (b) lightweight, and (c) ultralight wheelchairs.

pain, or the progression of a disease such as Multiple Sclerosis or Muscular Dystrophy. Recently, the development of Pushrim Activated Power Assist Wheelchairs (PAPAWs) has provided an alternative for these users. The PAPAW works through the use of a battery and a motor mounted directly into the wheel. The motor provides a supplement to the user so that very little force input from the user will still afford normal momentum. Transitioning from a manual wheelchair to a powered wheelchair may be difficult both physically and psychologically for some people. Users may not want to modify their homes or their cars to accommodate a powered wheelchair and may be used to providing their own mobility. Although the PAPAW provides a good intermediate wheelchair for users who may still benefit from a manual wheelchair, but do not have the strength or stamina, it also has its disadvantages. The added weight of the motor driven wheels dramatically increases the overall weight of the wheelchair and can also be difficult for users during transfers. Additionally, algorithms for the control of the PAPAWs are not yet refined and can lead to difficulty propelling the wheelchair.

POWERED WHEELCHAIRS

Powered wheelchairs represent devices that can provide an incredible amount of independence for individuals who may have extremely limited physical function. Perhaps even more than manual wheelchairs, having the proper elements and setup of a power wheelchair is vital. The lifestyle of the user, the activities in which they would like to participate, the environments to which they will be subjected, and ability level have all contribute to the correct prescription of a powered wheelchair. Many adjustments can be made to any particular powered wheelchair to specifically fit the needs of the user. Seating systems, cushions, added assistive technology to name a few. This section will focus on the characteristics that differentiate certain powered wheelchairs from one another (Fig. 2).

Powered wheelchairs come in three drive wheel setups: front, mid, and rear wheel. Each of these setups has different advantages and shortcomings. Powered wheelchair users are each unique and have specific requirements for their activities of daily living, such as maneuverability, obstacle climbing, or driving long distances. Mid-wheel

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drive wheelchairs tend to provide greater maneuverability because the drive wheels are located directly beneath the user’s center of mass. Front-wheel drive wheelchairs are often associated with greater obstacle climbing ability. Rear-wheel drive powered wheelchairs are good for speed and outdoor travel, but may not provide the maneuverability or stability for some users. The different wheelchair setups provide the means for users to achieve their goals.

For the user, the joystick is probably the most important part of the powered wheelchair. However the standard displacement joystick is not acceptable for all users. Current technologies have allowed almost any user to operate a powered wheelchair as well as other assistive technologies, such as computers. Even the smallest abilities of the user can be translated to powered wheelchair mobility such as foot control, head control, finger control, tongue control and so on.

Like manual wheelchairs, powered wheelchairs also have different classifications. Medicare defines powered wheelchairs in three major categories: Standard weight frame powered wheelchair (K0010), Standard weight framed powered wheelchair with programmable control parameters for speed adjustment, tremor dampening, acceleration control and braking (K0011), other motorized powered wheelchair base (K0014) (17). Pearlman et al. (18) recently conducted a study examining the reliability and safety of standard weight frame powered wheelchairs. Of the 12 wheelchairs tested, only 3 passed the Impact and Fatigue section of the ANSI/RESNA Standards (19,20). Medicare has recently proposed to stop funding these powered wheelchairs, recommending the addition of a programmable controller that would place it in the second category (K0011). However, this may not be acceptable since the problems exist mainly with the drive train or the frame of the wheelchair and these parameters would not change. In order to adequately serve the interests of powered wheelchair users, the frames, drive trains, and control systems all need to perform within the standards put forward by ANSI/RESNA.

WALKERS AND ROLLATORS

Some individuals may have the ability to ambulate, however, they may get tired very easily or have visual

Figure 2. (a) Front-, (b) mid-, and (c) rear-wheel drive powered wheelchairs.

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Figure 3. Robotic walker for users with visual impairments.

impairment problems that may result in a fall and injury. Fuller (21) reported that 33% of community-dwelling elderly people and 60% of nursing home residents fall each year. Walkers and rollators represent useful assistive technology devices for these individuals by lending support and weight relief during mobility. They may have zero, two, or four wheels and possibly have hand brakes. They may also contain a small area for sitting if the user becomes fatigued or a basket for carrying items for the user.

Some elderly persons, in addition to having mobility impairment, also have a visual impairment. Recent research has investigated a new robotic walker (Fig. 3) that through the use of sonar and infrared (IR) sensors can detect obstacles as well as provide guidance along a preprogrammed path (i.e., maneuvering around an assisted living home) (22).

SPORTS AND RECREATION DEVICES

As quality of life receives more attention, sports and recreational activities have become more important to individuals with disabilities. Sport and recreational activity participation provides many benefits to individuals with disabilities. Physical activity reduces or slows down the development of cardiovascular disease as well as modifies risk factors including high blood pressure, blood lipid levels, insulin resistance, and obesity (23). In addition, the development of muscular strength and joint flexibility gained through regular exercise improves the ability to perform activities of daily living (24). Regular exercise may help reduce clinical depression and days spent as an in-patient in a hospital, and may improve social interactions and prolong life expectancy (25). With the positive benefits of sports, exercise, and recreational activities in mind, the purpose of this section is to describe some of the more popular sports played by individual with disabilities.

Wheelchair Basketball

Wheelchair users who play basketball may have various diagnoses, such as paraplegia, cerebral palsy, amputations, post-polio syndrome, or a disabling injury. Participants are not required to use a wheelchair for their primary means of mobility or in their activities of daily living. Prior to the actual game, persons who want to play basketball must have their player classification level determined by a qualified referee. To equalize the capability of each team, the classification levels of the competitors are matched (26).

Whether players play zone or person-to-person basketball, the basic rules apply to both. Because different players have varying degrees of disability, rules have been developed that all players need to abide by. Keep firmly seated in the wheelchair at all times. A player may not use a functional leg or leg stump for physical advantage. An infraction of this rule constitutes a physical advantage foul (27).

Wheelchair basketball is similar to an everyday wheelchair, but incorporates features that enhance maneuverability (Fig. 4). Basketball wheelchairs are lightweight to allow for speed, acceleration and quick braking. The wheelchair must have four wheels. Two large, rear wheels and two front casters. The front casters are 2 in. (50 mm) in diameter and typically made from hard plastics, similar to the material used to make inline skate wheels. The rear wheels must be larger than or equal to 26 in. (338 mm) in diameter. The rear wheels must have handrims. Basketball wheelchairs use spoke guards made of high impact plastic. These guards cover the rear wheel spokes to prevent wheel damage and illegal ramming and picking. The spoke guards provide several benefits: First, spoke guards can be used to pick up the ball from the floor. Using a hand, the player pushes the ball against the spoke guard and rolls it onto their lap, Second, spoke guards protect hands and fingers from injury when reaching for the ball near another player’s rear wheel. Third, they provide space to identify team affiliations and sponsor names. Camber is an important feature of basketball wheelchair as well. Camber is defined as"the angle of the main wheel to the vertical’’, or as a situation in which"the spacing between the top

Figure 4. Players competing in a friendly game of wheelchair basketball.

points of the wheels may be less than the spacing between the bottom points’’. Increasing camber slightly reduces the height of the seat, while it proportionally increases the wheelbase, which corresponds to the width of the wheelchair. In the same way, with negative camber, the center of gravity of the occupied wheelchair moves backward. From a practical point of view, increased wheel camber improves hand protection as chairs pass through doors and, in terms of basketball, camber makes a wheelchair more responsive during turns and protects players’ hands when two wheelchairs collide from the sides, by limiting the collision to the bottom of the wheels and leaving a space at the top to protect the hands. Basketball wheelchair seats typically have a backward seat angle slope of 5–158. The angle of the seat compared to the ground is known as ‘‘seat angles’’. Guards are an exception. Guards are allowed to have lower seat heights and greater seat angles. These modifications make chairs faster and more maneuverable for ball handling.

Wheelchair Racing

Individuals with all levels of SCI as well as lower limb amputees can participate in competitive races. The preferred racing chair among racers is the three-wheel chair (Fig. 5). The three-wheel design is constructed from high pressure tubular tires, light weight rims, precision hubs, carbon disk/spokes wheels, compensator steering, small push rings, ridged aluminum frame, and 2–158 of wheel camber. The camber in a racing chair makes the chair more stable and allows the athlete to reach the bottom of the pushrim without hitting the top of the wheels or pushrim.

Hand-Cycling

Cycling has been a popular outdoor sport for several years. The adaptability of cycling to different terrains makes it a favorite for many. Adaptive equipment for bicycles consists of a hand cycle allows individuals with limited use of their legs to utilize the strength of their arms (28). A handcycle typically consists of a three-wheel setup to compromise for the balance required when riding a two-wheeled bicycle. Two-wheeled handcycles do exist but require a great deal of skill and balance. Handcycle designs allow the user to propel, steer, break, and change gears, all with the upper extremities and trunk. Two types of handcycle designs are

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readily available (1) the upright and (2) the recumbent. In an upright handcycle, the rider remains in an upright position similar to the position the body takes when seated in a touring bike. Upright handcycles use a pivot steer to turn. Only the front wheel turns while the cycle remains in an upright position. Transferring and balancing tend to be easier on the upright cycle. In the recumbent handcycle, the rider’s torso reclines and the legs are positioned out in front of the cyclist. These cycles use a lean-to-steer mechanism. The rider leans to turn, causing the cycle to pivot at hinge points. Leaning to turn can be challenging if the rider lacks trunk stability, in which case a pivot steering recumbent handcycle may be more appropriate. Recumbent handcycles are lighter and faster, making them the choice for hand cycle racing. Relatively minimal modifications are needed to accommodate individuals with tetraplegia. Some of the modifications include hand cuffs that can be mounted to the arm crank handles and elastic abdominal binders which can be fitted around the user and the handcycle seat to increase trunk stability.

Wheelchair Rugby

Rugby is played indoors on a large gym on a basketball court surface. Players use manual wheelchairs specifically designed for the sport. Due to the level of contact, the chairs have protective side bars on them and players are strapped in to prevent injury. Most chairs are made of titanium or steel to handle the hits that they sustain. In addition, the low pointers have a high camber (angle of the wheels) so that they can turn fast, as well as ‘‘red push rim covers so they can actually stick to the other person’s chair and hold them.’’ The high pointers have armor on the front of their chairs resembling a cow catcher so that they can push through the other players without getting stuck (Fig. 6).

To be eligible to play rugby, players must have a combination of upper and lower extremity impairment. Most of the players have sustained cervical level spinal injuries and have some degree of tetraplegia. Like in basketball, players receive a classification number based on there level of impairment (29). Rugby consists of two teams comprised of four players. The object of the game is for a player to have possession of the ball and cross the opponent’s goal line.

Rugby wheelchairs are strictly regulated to ensure fairness. However, chairs may vary considerably depending on

Figure 5. Shows a racing three-wheeled wheelchair.

Figure 6. Wheelchair rugby.

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a player’s preferences, functional level and team role. Team roles may be assigned according to ability. Players with upper body limitations tend to perform the defensive blocking and picking roles. They use chairs that have additional length and hardware. All rugby chairs have extreme amounts of camber, 16–208, significant bucketing, and antitip bars. The camber provides lateral stability, hand protection, and ease in turning. The bucketing (knees held high relative to rear end) helps with trunk balance and protection of the ball.

Tennis

Tennis players compete in both singles and doubles games. Players are required to have a permanent mobility-related physical disability that requires a wheelchair as the primary means of mobility. Tennis is played on the traditional tennis court using the tradition size and height tennis net. However, unlike traditional tennis, the ball is permitted two bounces on the court before it must be returned. Brakes are not permissible as stabilizers and the athlete must keep one buttock in contact with the seat at all times.

Tennis players use a three-wheeled chair with a large amount of camber to maximize mobility around the court. The seat is situated at a steep backwards seat angle slope. The angle helps with balance, keeps players against the seat backs, and gives them greater control over the wheelchair. The knees tend to be flexed with the feet on the footrest behind the player’s knees. With the body in a relatively compact position, the combined inertia of rider and wheelchair is reduced, making the chair more maneuverable (30). Handles and straps can also be added to the chair. Many players incorporate plastic rigid handles into the front of the seat. Players use these handles when leaning for a shot or making quick directional changes. Straps can be used around the waist, knees and ankles, to help with balance (31).

Adaptive Skiing

Skis for skiers with disabilities have advanced state-of-the- art skis that offer shock absorption systems, frames molded to body shape, and quick release safety options. Skiers with disabilities can maintain a similar pace to that of unimpaired athletes with the development of adaptive seating, backrests, cushions, tethering ropes, roll bars and outriggers. Outriggers, an adapted version of a forearm crutch with a shortened ski, provide extra balance and steering maneuverability (32). Two types of sit-down adaptive skies are available: Bi and Mono. Bi skis are appropriate for skiers with limited trunk stability. With Bi skis, the skier balances on two skies and angulates and shifts to put the skis on edge. Bi skis have wider base of support, can usually be mastered quickly with few falls and are easier to control than a mono ski. The Mono Ski is the ski of choice for individuals who want high end performance, maneuverability and speed. With a mono ski, the skier sits relatively high on the seat of the ski over the snow. The skier uses upper body, arm and head to guide their movement down the hill. Sit-, Monoand Bi-skis have loading mechanisms, usually hydraulic, that enable the individual

to raise themselves to a higher position for transferring onto a ski lift.

TRANSPORTATION SAFETY AND ADAPTIVE DRIVING FOR WHEELCHAIR USERS

Wheelchair users, like the entire population, use several forms of transportation to travel from place to place: They are passengers in public transportation systems (bus, subways, and vans) and private vehicles, and are potential drivers of each of these types of vehicles. To ensure the safety of all passengers and drivers, certain safety mechanisms must be in place: drivers must be able to safely control the vehicle, and all seated passengers require seats securely fastened to the vehicle and passenger restraints (e.g., seatbelts) which can secure the passenger to the seat. The requirement of passenger restraints is relaxed for passengers in large vehicles, like busses and subways, because of the low likelihood of high velocity crashes (33). In many cases, adaptation of a vehicle is necessary when the original equipment manufacturer (OEM) control and/or securement mechanism cannot provide adequate safety for wheelchair users because either (1) sensory and/ or motor impairments of the user requires adaptive driving equipment so the vehicle can be safely controlled, or (2) the user cannot safely or effectively use the OEM seat or passenger restraint system in the vehicle.

Vehicle Control Systems

The complexity of the adaptive equipment required for safe control of the vehicle is correlated to the type and level of impairment of the wheelchair user. Adaptive driving equipment can be as low tech as attaching a knob on a steering wheel, and as high tech as fly-by-wire technology, where computer-controlled actuators are added to all of the controls, and the drive interfaces with the computer (via voice and/or low or no-effort sensors). Adding actuators to all of the driving and operating controls of the vehicle through computer controls.

An example of this range is the types of steering adaptations available for people with disabilities. Figure 7 demonstrates both a typical steering knob for a person with little to no loss of hand sensory-motor function (a), and (b) a knob for someone with loss of some sensory motor function. Both types of steering knobs serve the same purpose: They allow the driver to safely steer the vehicle with one hand while (typically) their other hand is operating a hand control which actuates the fuelaccelerator and brake pedals. When upper-extremity sensory-motor function does not allow for safe turning of the OEM steering system (even with a knob), actuators can be used in lieu of upper-extremity function. These systems are named ‘‘low-’’ or ‘‘no-effort’’ steering systems, depending on the type of assistance that the actuators provide. Retrofitted controls for these systems are used and typically require removal of the OEM equipment (e.g., the steering wheel and/or column). Consequently, when this level of technology is used, it usually becomes unsafe for an unimpaired individual to drive the vehicle (without significant training).

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Figure 7. Steering knobs.

Common fuelaccelerator and braking system hand controls are bolted to the OEM steering column, and actuate each pedal with mechanical rods (Fig. 8). These types of controls require nearly complete upper extremity function to operate. When upper extremity function is substantially impaired actuators are added to the braking and fuelaccelerator systems and are operated through some switching methods. The types of switches depend on the most viable control mechanism for the user: in some cases, a simple hand-operated rheostat variable resistance switch (i.e., dimmer switch or rheostat) may be used, and in other cases, a breath-activated pressure switch (sip-and-puff) system may be used.

The above steering, fuelaccelerator, and brake adaptive equipment are focused on the primary control systems of the vehicle (those which are required to drive the automobile). Various adaptive equipment can control the secondary control system of the vehicle also (e.g., ignition switch, climate control, windows). Like the primary control adaptive equipment, equipment to modify the secondary controls of the vehicle range from low to high tech. For example, users with impaired hand function may require additional hardware to be bolted to the ignition key so they can insert the key and turn it to start the vehicle. Alternatively, hardware can be added to allow a drive to start the vehicle via a switch, either remotely or from within the cabin. Power windows and door-lock switches can be

Figure 8. Common hand controls.

rewired to larger switches, or in more accessible locations for the driver.

Both primary and secondary control systems must be placed in locations easily accessible to the driver. In some cases, wheelchair riders will transfer out of their wheelchair directly into the OEM seating system, allowing for most controls to remain in their OEM locations. If a wheelchair user remains in their wheelchair and drives the vehicle the controls must be made accessible to their seated position and posture. In these cases, along with the case a wheelchair users remaining in their wheelchair as passenger, provisions must be made to safely secure the wheelchair to the vehicle, and to provide adequate passenger restraints.

Wheelchair Tie-Down and Occupant Restraint

Systems (WTORS)

For both practical and safety reasons, when a wheelchair user remains in wheelchair while riding in a vehicle they must be safely secured to the vehicle. An unsecured wheelchair will move around, causing the user to be unstable while the vehicle is moving. Being that power wheelchairs can be in excess of 200 lb (91 kg) in weight, This instability could cause harm to the wheelchair rider and/or the surrounding other passengers vehicle occupants. If the wheelchair user is driving, they may lose control of the vehicle if they accidentally roll away from the vehicle controls. Another important concern for an unsecured wheelchair rider is in the case of an accident. An unsecured wheelchair and user can easily be ejected out of the vehicle if they are not secured. The WTORS systems are currently governed by the ISO 7176-19 (34).

Several types of tie-down systems exist, including a four-point belt system and various latching-type mechanisms which typically require hardware to be attached to the wheelchair. The four-point belt systems are most common, and are found on public busses, and also private vehicles. Theses systems are the most widely used tie-down system because they can be attached to a wide variety of wheelchairs. In some cases, manufacturers incorporate attachment rings for these tie-down systems into their wheelchair. When no points of attachment are available (most common situation), points at the front and rear of the seat or frame be used. These attachment points must be sufficiently strong to secure the wheelchair in the event

552 MOBILITY AIDS

of a crash, and be in locations which will allow the straps to be oriented within a specified range of angles with the horizontal (front straps: 30–608, rear: 30–458).

Unfortunately, tie-down systems are they are not convenient to use: a second person (other than the wheelchair user) is typically needed to help secure the wheelchair, making the operation laborious, and in some cases awkward for the wheelchair users who may not be comfortable with another person touching their wheelchair or encroaching on their personal space. Consequently, and especially on public transportation, these systems are commonly unused and the wheelchair user relies on their brakes wheel-locks for stability, risking their own safety in a crash.

Other mechanisms have been used to secure a wheelchair to the vehicle. These included wheel-clamps and t-bar systems. With these mechanisms, wheelchairs are secured to the vehicle through a mechanical clamp that adjusts to the wheelchair size. These systems are quicker to attach to the wheelchair, but are still difficult or impossible for a user to use independently.

A variety of wheelchair tie-down systems have been developed that allow the wheelchair users to independently lock and unlock their wheelchair to the vehicle. A common one used for personal vehicles is the EZ-Lock System, which is a hitch system for the wheelchair. This system allows the wheelchair user to maneuver the wheelchair so a specialized hitch attached to the wheelchair is captured into a latch bolted to the vehicle; both electric and manual release mechanisms can be used to unhitch the wheelchair from the device, allowing for custom placement of a hitch for easy accessibility to the wheelchair user. A drawback to this system is the specialized hardware that must be attached to the wheelchair that restricts folding a manual wheelchair and reduces ground clearance.

Because this system is designed to allow the user to drive forward into the device, it works well and is common in private vehicles where the wheelchair user drives the vehicle. In larger vehicles, such as public busses, it is typically more convenient for a user to back into a spot and lock their wheelchair.

An ideal system for public transportation would be one that a user can operate independently and that does not require specific hardware to be attached to the wheelchair that may not work on all wheelchair models. A system is currently being developed at the University of Pittsburgh that tries to achieve these goals.

Occupant restraint systems are the last requirement to allow a wheelchair user to safely travel in a vehicle. These restraint systems mimic the function of a seat belt, and can be either attached to the wheelchair (integrated restraint) or to the vehicle (Fig. 4). In both cases, the placement of the restraints with respect to the body is critical to prevent injury in a crash—either through direct insult of the seatbelt with the body, or because of submarining (where the torso slides down under the pelvic belt).

To ensure these WTORS systems and the wheelchair themselves can safely survive a crash, standards testing is in place. Rehabilitation Engineering and Assistive Technology Society of North America (RESNA), International Standards Organization (ISO), and Society of Automotive

Engineers (SAE) have worked in parallel to establish minimum standards and testing methods to evaluate wheelchairs and WTORS systems (35). These tests mimic those performed on OEM seat and occupant restraint systems, which suggest the system should be able to withstand a 20 g crash (36). To encourage and guide wheelchair manufacturers to build their wheelchairs to these standards researchers have developed a website to inform all relevant stakeholders of the latest information (http:// www.rercwts.pitt.edu/WC19.html).

LOWER EXTREMITY PROSTHETICS

Prosthetics are devices that replace the function of a body organ or extremity, unlike orthotic devices, which support existing extremities. Prosthetics range from simple cosmetic replacements to complicated structures that contain microprocessors for controlling hydraulic and pneumatic components. Commonly used prosthetic devices primarily include artificial limbs, joint implants, and intraocular lenses. Approximately, 29.6–35.4% of the U.S. population use prosthetic limbs (37) with >2% of them aged between 45 and 64 years using lower extremity (LE) prosthetics for mobility (U.S. Bureau of Census, 2000). Amputation, resulting from peripheral vascular diseases in the older population (60 years and older) and trauma in young population can be considered factors for the use of LE prosthetics.

Research and development in clinical practice has resulted in recent advances in the area of prosthetics designs and controls technology. Examples of these advances include the use of injection molding technology for socket manufacturing, shock absorbing pylons, the incorporation of neuro-fuzzy logic microprocessor-based controllers for myoelectric prostheses, and microprocessorcontrolled prosthetic knees and ankles (38,39).

Prosthetic feet classified as"uniaxial’’ allow for movement at a single axis in one plane, such as plantarflexion and dorsiflexion of the ankle. In this type of prosthetic foot, the heel is typically composed of the same density materials as the rest of the foot, with an option of different heel height. Also, uniaxial feet have different options at the rubber toe section in terms of flexibility, which depends on the weight of the individual. Multiaxial prosthetic feet (MPFs) have five degrees of motion in three planes: plan- tarflexion–dorsiflexion, inversion/eversion, and rotation. This feature provides stability to the user, while walking on uneven surfaces and also aid in shock absorption lowering intensity of shear forces on residual limb. Elastomer or rubberized material is used to alter, resist, or assist with the different degrees of motion in the prosthetic foot. MPFs also provide options for different heel heights [0.5–1 in. (13–26 mm)] and different degrees of toe material resistance, while split internal structures in the heel assist with inversion/eversion on uneven ground. The MPFs are prescribed by the weight and shoe size of the consumer.

The solid ankle, cushion heel (SACH) prosthetic foot is the most commonly prescribed prosthetic foot for lower extremity amputations. The SACH foot is constructed out of eurothene (plastic) materials with a less dense material

 

 

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553

Table 1. Functional Level and Devices

 

 

 

 

 

 

 

 

 

Functional Level

Type of Device

 

 

 

 

 

 

K0

No ability to ambulate or transfer safely; prosthesis

Cosmesis

 

 

does not enhance mobility

 

 

 

K1

Transfers and ambulates on level surfaces;

SACH

 

 

household use

 

 

 

K2

Able to negotiate over low level environmental

Low level energy storage feet

 

 

barriers; limited community ambulation

 

 

 

K3

Prosthetic usages are beyond simple ambulation;

Energy storage prosthesis

 

 

able to traverse MOST environmental barriers and

 

 

 

 

is a community ambulator

 

 

 

K4

Able to perform prosthetic ambulation exceeding

Energy storage prosthesis

 

 

basic skills (i.e., high impact); child, active adult

 

 

 

 

and athlete

 

 

 

 

 

 

 

 

incorporated at the heel. Use of materials with different densities permits proper positioning while standing, as softer heels aides in enhancement of the walking efficiency after heel strike, by shifting center of gravity forward. A device known as durometer is used to measure the density of plastics used in prosthetic devices. The weight and activity level of the individual using the prosthesis determines which heel density is selected, as heavier user require firmer heel cushion. The stiffness of heel, also determine amount of knee flexion and shock absorption. Greater the heel stiffness more the knee flexion and lower shock absorption during heel strike and vice versa. The SACH foot also contains a keel made out of a hard wood or composite material. Belting material is applied to the keel, which prevent the keel it from breaking through the eurothene cover. During ambulation, the foot simulates plantar flexion movement and prevents the loss of anterior support during the push off at the toe.

Individuals who use foot prosthetic devices are assessed for weight, potential activity levels, and type of use for which they anticipate using their prosthetic devices. Based on this assessment, clients are then categorized into four functional levels:

Energy Storage and Return (ESAR) prosthetic feet are fabricated to assist with the dynamic response of feet, acting as a diving board from which a person can push off during walking. These feet have capability to store energy during stance phase and return it to the user to assist in forward propulsion in late stance phase. The ESAR has flexible keels and are prescribed by the anticipated activity level and weight of the person. Also, limited evidence suggests use of ESAR as their use results in increasing ambulation speed and stride length 7–13% greater than with a conventional (SACH) foot in both traumatic and vascular transtibial amputees (40).

Macfarlane et al. (40) compared energy expenditure of individuals with transfemoral amputations who walked with a SACH foot versus a Flex-Foot prosthetic. The SACH has a solid ankle and cushioned heel construction, while the Flex-Foot prosthetic has a hydraulic knee joint. The authors determined that Flex-Foot walking resulted in significantly lower exercise intensity, reduced energy expenditure and improved gait efficiency. These findings are significant considering the SACH foot is the most commonly used foot prosthetic in the U.S. today (41). Lower

energy expenditure was also reported for individuals with trans-tibial amputation with the use of Flex-Foot as compared with a SCAH foot.

Higher level of limb loss results in addition of more prosthetic components. Prostheses for transfemoral amputations comprised of four basic components: the socket, the knee joint, the pylon, and the foot. Pylons are classified as: exoskeleton in which the weight of the individual is supported by the external structure of the prostheses (i.e., a crustacean shank), or endoskeleton that is comprised of an internal, weight-bearing pylon encased in moldable or soft plastics (i.e., modular pylon). The knee mechanism use, a conventional damping system, where a flow of (fluid or air) is controlled by a valve and its operation is set for a particular walking speed according to user’s preference. The system described as intelligent prosthesis (IP), where a diameter of damping controlling valve is changeable according to varying speed of walking (42). Romo provided guidance on the selection of prosthetic knee joints and indicated that proper alignment impacts the effectiveness of matched and adjusted knee joints for smooth and reliable gait (43). Taylor et al. (44) compared effectiveness of an intelligent prosthesis (IP), and pneumatic swing-phase, control-dampening systems while walking on a treadmill at three speeds of 1.25, 1.6, and 2 mph (2, 2.6, and 3.2 km h 1). The results indicated lower VO2 consumption for individuals using IP compared to controls-damping system at 2 mph (3.2 km h 1). The question often raised by critiques concerns the cognitive demands by the high end technology on the users. The results of the study by Heller et al. (42) that investigated cognitive demand when using the IP compared to a conventional prosthesis indicated no significant differences while using these prostheses for ambulation. Though not uncommonly prescribed high rejection rates has been described for prostheses after hip disarticulation and hemipelvectomy. These prostheses consist of an addition of hip joint mechanism to other parts similar to prostheses prescribe after transfemoral amputation.

Modular systems were first developed in the 1960s by Otto Bock, which consisted of shock absorbing pylons that contained with shock absorbers. Also, a reverse-pyramid fixture at the ends of the pylon permits angular adjustments to the alignment of these devices with the residual limb. Modular systems are lighter than the earlier wooden

554 MOBILITY AIDS

systems, allow for 158 of movement gain in either the frontal or sagittal plane, and also permit internal and external rotational adjustments. Modular systems can extend the life of a prosthetic device, as worn parts can be replaced. In addition, individuals using these systems experienced less need for maintenance.

A significant improvement in the design procedure of the prosthetics considers the interaction of forces between prosthesis and residual limb can be found in the literature. Jia et al. (45) studied the exchange of loads and forces between the residual limb and prosthetic socket in transtibial amputation using the Finite Element Analysis (FEA) method. Lee et al. (46) used FEA to determine contact interface between the transtibial residual limb and prosthetic socket. The study determined the need for sameness of shapes for both the residual limb and socket in order to decrease peak normal and shear stresses over the patellar tendon, anterolateral and anteromedial tibia, and popliteal fossa. Winson et al. investigated the interaction between socket and residual limb during walking using a FEA model for transtibial prosthesis. Pylon deformities and stress distribution over the shank were problems identified during walking and results indicated need for pylon flexibility for better optimization and need of future studies identifying fatigue life of these prostheses (47).

With advancement in the area of prosthetics designs and development, simultaneous factors that need to be considered, use of these devices in clinical practice for targeted population and cost containment. Premature abandonment of mobility assistive devices, which might be due to poor performance and/or changes in the need of the user, is not uncommon and adds to the expense of these devices (48). Improved quality of service delivery for LE prostheses, which include identifications of reasons for successful use or nonuse of LE prostheses, is needed (49). Also, incorporation of standardized performance testing procedure to ensure durability of LE prosthetics is vital to the appropriate prescription of, and satisfaction with, prosthetic devices.

Prosthetic devices of today incorporate advancements from the aerospace and engineering fields and include the use of new materials, such silicone elastomer gel sleeves in to assist in the fit of prosthetic sockets, prosthetic feet made from carbon-fiber composite components that are lighter in weight, and surgical implantation of titanium prosthetic attachment devices directly to bones of residual limbs (50,51). Neuroand microprocessors and sensors are now incorporated on-board the prosthetic device to control knee joint movement to improve the symmetry of different gait patterns across a variety of cadence speeds. Hydraulic or pneumatic devices are also used to dampen the swingthrough phase of walking with the prostheses to assist with walking at difference cadences (52,53). Manufacturers are now using computer-aided design and manufacturing techniques to improve the fit of the prosthetic sockets as well as component designs (54,55).

Because of the growing population of people in need of mobility aids, and their demand to maintain their lifestyle, whether that includes going to and from work, participating in extracurricular activities, or maneuvering around their environment, continuing information must be gathered and disseminated to make these goals achievable.

Through technological advancements people who require mobility aids can accomplish more of their goals than ever before, however there are still people for whom the technology is not yet developed enough or cannot obtain the proper devices to meet their needs. It is for this reason that problems must continually be studied and innovations must advance so that mobility aids will serve anyone who requires them to meet their goals.

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