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Logo for the Journal of Rehab R&D
Volume 35 Number 4, October 1998
Pages 431-446

CLINICAL REPORT


Clinical Evaluation of a New, Above-Elbow, Body-Powered Prosthetic Arm: A Final Report

Mary E. Cupo, BS, RKT and Saleem J. Sheredos, BEE, MHCA, Rehabilitation Engineer

Technology Transfer Section, Baltimore Rehabilitation Information and Technology Administrative Center, Department of Veterans Affairs, Baltimore, MD 21202-4051

Abstract--The AdVAntage ArmTM is an above-elbow (AE) body-powered arm designed to improve upon, and overcome, some of the major limitations of conventional prostheses. It is the result of research and development (R&D) accomplished at the Center for Engineering Design (CED), University of Utah and Sarcos Research Corporation (SRC), Salt Lake City, UT. The AdVAntage Arm was developed to provide the following main features: lightweight, independent elbow and terminal device (TD) control, and a cable recovery system for full TD actuation at any elbow position.

  The Department of Veterans Affairs (VA) Rehab R&D Service's Technology Transfer Section (TTS), with collaboration from the VA National Prosthetic and Sensory Aids Service (PSAS), managed a multi-center clinical evaluation of the precommercial AdVAntage Arm (the Arm). The purpose was to objectively assess and affirm the Arm's functional advantages, reliability, clinical application, and commercial readiness.

  Eleven VA prosthetic services served as evaluation sites with a total of 16 subjects with amputation (14 unilateral and 2 bilateral). Fifteen prosthetists provided their comments. Overall, the results demonstrated that the Arm could be fit for use by persons with transhumeral amputation. Once the learning curve was overcome, the majority of subjects reported that the Arm offered several functional advantages over their conventional prosthesis. Its overall lightweight, separation of elbow and TD function, and cable recovery system allowed opening and closure of the TD at any elbow position; resulting in a more fluid manner of use and allowing subjects to perform more activities from waist level and above (especially in the outstretched and overhead positions). At the conclusion of clinical trials, 10 subjects elected to keep the Arm for continued use.

  The manufacturer is committed to the commercial marketing and technical support of the arm. Based upon the clinical findings, the AdVAntage Arm was recommended for commercial production and availability, upon prescription, to appropriate veteran beneficiaries.

Key words: above-elbow, AdVAntage Arm, amputation, body-powered, clinical evaluation, prosthesis, technology transfer, transhumeral amputation.


This material is based on work supported by the Department of Veterans Affairs, Rehabilitation Research and Development Service, Washington, DC.
Address all correspondence and requests for reprints to: Mary Cupo, RKT, BRITAC, VA Rehabilitation Research and Development Service, Technology Transfer Section, 103 South Gay Street, Baltimore, MD 21202-4051; email: mary@vard.org.

INTRODUCTION

  One of the high priority areas for the Department of Veterans Affairs (VA), Rehabilitation Research and Development (Rehab R&D) Service involves prosthetics, amputations, and orthotics. The VA supports research and development that result in artificial limbs that are lighter, better fitting, and permit more natural movement for activities of daily living (ADL).

  In 1985, LeBlanc (1) stated, "Standard body-powered upper-limb prostheses have not changed significantly since developments in the 1950s [that] were spurred by World War II. [Prosthetists] still employ ancient technology using a shoulder harness and steel cables for operation." This observation still holds true today. The artificial arm problem has not yet been solved. "Adequate replacement of the human hand and arm is one of the most difficult problems facing medical technology" (2). Only 50 percent of those with upper limb amputation are estimated to wear prostheses, versus 75 percent for persons in need of lower limb prostheses (3). In part, this is because the loss of one leg is far more debilitating in the process of ambulation than the loss of one arm is in manipulation. However, the statistics also indicate a general dissatisfaction with upper limb prostheses. Many individuals with upper limb amputation (particularly those with one sound arm) feel that a prosthesis offers too little cosmetic benefit or functional advantage to compensate for the discomfort and inconvenience of wearing the device (4).

  Although the use of externally powered prostheses is increasing, current estimates are that 90 percent of individuals who wear upper limb prostheses use the body-powered types because they are relatively inexpensive, functional, reliable, and have some sensory proprioceptive feedback from the shoulder harness and cable control system (5). Even with these relative benefits, "to actually move the elbow, large forces are required due to the 'mechanical disadvantage' experienced by the shoulders. Because of these high forces, lifting ability is extremely limited" (4). Studies at New York University indicate that it requires 5.08 cm of excursion to flex the elbow to full flexion and 6.35 cm of excursion to open the terminal device (TD) fully at the mouth. Therefore, a total of 11.43 cm of excursion is necessary to fully operate a traditional above-elbow (AE) prosthesis (6). A drawback of conventional AE prostheses is that the same cable is used for both the elbow and TD. This requires extra motion of the cable in order to actuate the TD when the elbow is fully flexed. The shorter the length of the humerus, the more difficult it is to develop excursion of the cable and, therefore, the more difficult to perform activities that occur with the elbow flexed and the TD open, usually near the wearer's midline or mouth. Although full TD opening is not a goal of most individuals with unilateral transhumeral amputation (THA), it remains a goal for many of them, even though they still have one normal hand. Persons with short AE amputations have difficulties performing full TD opening near the mouth (6).

  The higher the level of amputation, the more difficult it is for the person to control the functions of the limb. For those with THA, more exertion and greater gross body motion are required to operate an elbow plus a terminal device (7). Weight reduction in upper limbs is extremely important and may be the difference in a person's decision to wear or not wear an artificial arm. The constant axilla pressure creates a fair amount of discomfort. This pressure is directly related to the weight of the total prosthesis. For the person with lower limb amputation, the weight can be relieved while standing, sitting, and even walking, but the person with upper limb amputation is frequently saddled with a constant hang weight (8). The combination of high popularity with significant problems gives the impression that the body-powered prosthesis has functional advantages that have been overlooked (4).

  The AdVAntage ArmTM (Figure 1) is designed to improve upon, and overcome, some of the major limitations of existing body-powered arms. It is the result of research and development (R&D) accomplished at the Center for Engineering Design (CED), University of Utah, Salt Lake City, UT and Sarcos Research Corporation (SRC), Salt Lake City. The CED also developed the Utah Arm, which is still the most advanced commercially available myoelectric prosthesis (9).


Figure 1. Several views of the AdVAntage Arm.
Figure 1.Several views of the AdVAntage Arm.

  The CED and SRC (the manufacturer), based upon design criteria from the 1989 VA Prosthetics/Orthotics/Amputations Priority Workshop that called for "body-powered elbows that provide greater range of motion (ROM), and adjustable force excursion requirements," developed the AdVAntage Arm (the Arm) to provide these features and several more. These new milestones in prosthetic technology have been enabled by the application of advanced computer-aided design (Pro-E) and composite injection molding techniques; which led to efficient mechanical computations and control functions, and the design of the new lightweight, body-powered Arm. Developers felt that these unique design features would make the Arm especially useful for persons with high-level THA (Figure 2), bilateral amputation, and those with limited shoulder motion.


Figure 2. Subject with a short transhumeral
Figure 2. Subject with a short transhumeral amputation level using the AdVAntage Arm. High elbow flexion angle allows full operation of TD at and around the mouth and head area.

  The AdVAntage Arm has the following claimed advantages over existing, conventional body-powered systems:

  This R&D effort led to the submittal of a Request for Evaluation (RFE) to the VA Rehab R&D's Technology Transfer Section (TTS) for review. Results of the peer reviews were positive and endorsed proceeding with a national, multi-center clinical evaluation. TTS coordinated the evaluation of the precommercial Arm as part of the technology transfer process.

  During the initial process of transferring this precommercial arm, many unforeseen design changes surfaced. Technical problems arose when attempting to fit the first five arms. Subjects were unable to achieve a functional level of acceptance in order for clinical trials to commence. This necessitated a hold on further manufacture and a recall was initiated by the manufacturer to reevaluate and incorporate design improvements. Subsequently, the following changes were made: relocation of the control mechanism from the forearm assembly to the elbow and the addition of a wrist interface that would accept the most commonly used TD. As a result, manufacture and clinical trials of the remaining 15 arms, with the revisions, was resumed.

  The purpose of the evaluation was to determine the acceptance of the precommercial Arm by the target population; assess its potential for improving functional levels of independence for the intended user; validate the effectiveness of the design features; and identify any modifications that might be needed to improve optimal clinical use and enhance its marketability. Specific areas to be scrutinized in this evaluation were:

DESCRIPTION

  The Arm is an AE body-powered prosthesis designed to offer a unique separation of the elbow movement mechanism from TD actuation, which allows opening and closure of the TD at any elbow position using the same cable excursion. Functional characteristics are detailed in Table 1.

Table 1.
AdVAntage ArmTM: functional characteristics.


Characteristic Numerical Range

Excursion Range 128° (20° to 148° elbow flexion)
Angle past horizontal 58°
Main cable travel 2 in
Lock/unlock cable travel 3/8 in
Total weight: (elbow and
  forearm assembly
460 g
Life lock positions 9
Active lift/Load limit
  (locked)
2.5 lbs/50 lbs

  When the elbow is controlled, the TD is disconnected from the control cable. When the TD is controlled, the elbow is locked and disconnected from the control cable. There is cable recovery when the state is changed so that the total required cable excursion, in order to fully flex the elbow and fully operate the TD, is reduced over that of conventional prostheses.

  Control is by conventionally positioned dual cables. The control cable drives the elbow and TD sequentially according to the state of the switching mechanism. The lock cable locks the elbow and simultaneously changes the state from elbow control to TD control. The system consists of two main parts, the elbow mechanism and forearm structure. The elbow contains the mechanism that controls the function of the arm and the state changer lock pin lift assist. A sequential pull of the lock cable will unlock the elbow and change the state from TD to elbow control. Polymer cable material (Spectra 1000®) is used for both the control and lock cables. This material provides very low friction as well as high strength.

  The Arm uses a standard socket and a conventional dual cable harnessing system, such as the figure-eight harness, for attachment and actuation. For correct operation of the cable recovery system and state changer, the harness must be adjusted so the wearer is able to relax the actuation cable. Operation of the Arm is similar to typical dual cable control systems, with one exception. After a lock or unlock command, the wearer relaxes the actuation cable to allow the logic cable to engage the state changer device. For example, if the Arm is raised to a position and locked, the actuation cable must be relaxed until the TD is engaged. Pulling on the actuation cable will then operate the TD. Pulling on the lock cable again to unlock the Arm will release the TD control but will not unlock the elbow until the actuation cable is pulled to the appropriate position to engage the elbow control. The elbow will unlock at that point and the actuation cable will control the elbow motion once again.

CLINICAL EVALUATION METHODS

Evaluation Models
  TTS contracted and procured 20 precommercial models of the Arm for evaluation purposes (SRS, Salt Lake City, UT).

Subject Selection
  With collaboration from the Chief Consultant, Prosthetic and Sensory Aids Service (PSAS), VA Headquarters (HQ), TTS coordinated the subject selection for the clinical evaluation of the Arm. The following subject selection criteria, as provided by the developer, was transmitted to Chiefs, PSAS, VA-wide:

Primary Indications

Supplemental Indications

Primary Subject Characteristics

  Data instruments were completed on each potential subject assessing their current physical and prosthetic function. These data were reviewed for approval by PSAS (VA HQ)/TTS/CED/SRS to ensure that the intended subject fully met the stated criteria. Upon approval, a memorandum, acknowledging participation in the evaluation and concomitant responsibilities, was sent from the appropriate Regional Director to the Director of the VA Medical Center (VAMC) responsible for the subject's prosthetic services.

  All approved subjects received information on the purpose and significance of their participation in this evaluation. Each was informed that participation would involve a 30- and 90-day follow-up visit after the fitting was complete. Informed consent was obtained from each subject prior to their fitting and in accordance with the respective VAMCs.

Fitting Process
  The costs for fitting the revised Arm were covered by PSAS VA HQ. The fitting site supplied the wrist and TD. Preferably, these were the same as the subject was currently using. The local prosthetist fabricated the socket and harness; the socket was conventional. The harness was also conventional, with modifications, as needed, to ensure rotational stability, since the control cable must be able to be relaxed by the wearer.

  A User's Manual was supplied with each elbow unit. The manual included operating and fitting instructions and a prosthetic checkout for the Arm. According to the manual, a manufacturer's technical liaison was designated as point of contact for questions pertaining to the fitting process and for any technical issues that arose during the evaluation.

Training
  An outline for training procedures was provided by the developer and included as part of the protocol.

Maintenance and Repair
  In the event of arm malfunction, the designated field Participating Investigator (PI) was instructed, in the protocol, to document (TTS-105 data instrument) the incident and submit the form to the Project Manager, TTS.

Documentation and Data Management
  All data instruments, used for this evaluation, were completed by the field PI at each center via interview with evaluation participants (i.e., subjects, prosthetist, and therapist). Data analyses for statistical measures and responses were tabulated using the Statistical Package for the Social Sciences (SPSS/PC+).

RESULTS

  The following results are based upon data collected from the participating subjects, prosthetists, and field PIs. Sixteen subjects met the criteria and were accepted into the study; all subjects completed pre-fitting data instruments. Fifteen of the 16 completed the 30-day post-fitting instruments. One subject was lost to follow-up. Eleven subjects completed the 90-day post-fitting instruments. Of the 5 subjects who terminated their clinical trial at the end of their 30-day follow-up, 4 reported that it was primarily due to their inability to function properly with the Arm. A fifth subject was unexpectedly hospitalized. Fifteen out of 16 prosthetists completed fitting instruments.

Subject Characteristics
  The subject characteristics (as shown in Table 2) are based on the completed Subject Background data instruments. (Two of the approved subjects had bilateral THA).

Table 2.
Subject sample.


Characteristics N=16 %

Age Groups 31-45 19
  46-60 44
  61-75 31
  75+  6
     
Sex Male 94
  Female  6
     
Presently Employed Yes 50
  No 50
     
Type of Employment (n=8) Administrative 37
  Clerical 13
  Technical 13
  Other 37
     
Amputation Type Unilateral 88
  Bilateral 12
 
Amputation Levels (n=18) Forequarter  6
(two subjects are bilateral) Short AE 39
  Standard AE 55
     
Years Post-Amputation (n=18) 1-5 16
(two subjects are bilateral) 5-10  6
  10+ 78

  The subject sample was a very diverse group, with geographic location distributed throughout the country. Subjects resided in a variety of environments from rural to urban settings. They ranged from extremely active, heavy-duty users to those who would be considered light-duty users. A majority of the subjects were long-time prosthetic wearers. This diversity provided for a very comprehensive clinical trial. All subjects were very motivated to participate and were looking forward to trying a more functional and efficient body-powered arm.

  Nineteen percent of the subjects reported poor strength and ROM of the residual limb. These subjects had experienced difficulty with conventional body-powered arms and were considered good candidates for the Arm based upon its unique cable recovery system and lightweight features.

  Fifty percent of the subjects indicated usage of modifications such as an axilla loop, shoulder sling with axilla loop, or excursion amplifier to increase dual control function of their existing body-powered arms.

  Eighty percent of the subjects employed shoulder extension on the amputation side to control their elbow lock while the remaining used shoulder flexion on intact side and manual pull with the intact hand.

  Of the 16 subjects, 75 percent utilized an exoskeletal prosthesis while the remaining 25 percent reported using an endoskeletal.

Subject Response (Pre-AdVAntage Arm)
  Prior to receiving the Arm, each subject completed a Subject Response (PRE) data instrument. The data gathered from this instrument is based upon the subject's, present or past, prosthetic experiences and provided comparative data for the Arm.

  A majority of subjects (88 percent) used their present arm for more than 5 hours per day and between 5-7 days per week (88 percent). Subjects rated features of their present arm as shown in Table 3.

Table 3.
Subject's rating of features of present prosthesis (N=16).


FEATURES % POOR % FAIR % GOOD % EXCELLENT % N/A

Elbow control 25 25 50    
Terminal device control 20 37 37  6  
Cable control system 19 44 31  6  
Ease of use  6 50 30  6  
Reliability 19 12 56 13  
Forearm lift 50 13 31   6
Cosmesis 13 56 31    
Noise level  6 37 57    
Weight 12 38 44 6  
Training 12 38 44 6  
Durability  6 12 69 13  
Donning/Doffing  6 31 38 19 6
Suspension system  6 31 56  7  
Comfort 19 38 37  6  

  Each subject experienced some malfunction with his/her prosthesis and in some cases found the length of downtime to be unacceptable.


Rating of TD
Figure 3. Subject's rating of TD function of present prosthesis (N=16).

  Figure 3 focuses on subjects' rating of TD function for specific activities. For any item rated No or Not Done, the following comments were provided:

  1. "Unable to voluntarily open the TD due to suspension and control cables when elbow is flexed."
  2. "My prosthesis is not very functional."
  3. "Not enough cable."
  4. "Unable to open TD when arm is flexed, also locked elbow has a tendency to release when performing activities around the head."
  5. "Unable to open TD at these positions."
  6. "Do not have good control of arm in general, especially TD, harness will slip if arm attempts to reach mouth."
  7. "When elbow flexed up 90°, loses control."
  8. "Cannot open TD once positioned."

  When asked if their present prosthesis snags clothing during operation 62 percent responded yes while 31 percent reported no problems. The following were some of their comments pertaining to this issue:

  1. "Specifically at the cable and pivot points of the elbows"
  2. "When getting dressed, and bunches in elbow limiting elbow flexion"
  3. "Taking clothes on and off, arm will snag"
  4. "Hooks on pants or jackets"
  5. "It wears out clothes in certain areas"
  6. "TD snags on loose fitting clothes"
  7. "Sweaters snag on TD and cable housing."


Subject rating
Figure 4. Subject's overall rating of present prosthesis (N=16).

  Figure 4 shows subjects' overall rating of their present arm. Subjects who gave a Poor or Fair rating made the following comments:

  1. "Poor design."
  2. "Due to my severe level of amputation, it was difficult to get the arm to function for any type of activity."
  3. "Limited range of use for TD function and excessive body motion required to operate."
  4. "Not made for someone to do everyday things--never sure arm will work right when needed; Cables snap and have to ask others for help."
  5. "Using same type of arm 50+ years and should be better comfort and function."
  6. "Not totally pleased with functionality of prosthesis and looking for a more energy efficient responsive prosthesis."
  7. "Elbow controls are poor."

Fitting/Training of the AdVAntage Arm
  Sixteen fittings were completed during the clinical evaluation. Fourteen were unilateral and two were bilateral. Subjects were given the option of keeping their Arm for continued use at the conclusion of their clinical trial. Those Arms that were not kept were refitted to other subjects, which resulted in a larger number of fittings than Arms.

  The Arm was distributed to the respective local prosthetists (identified by the field PI) to complete the fitting and associated training of the subjects. The prosthetists were asked to complete the fitting instrument for each subject. This instrument also included questions pertaining to the subjects' training. Out of an expected 16 instruments, 15 were completed and returned to TTS.

  Compared with fitting conventional AE arms, 20 percent felt fitting the AdVAntage Arm was easier, 20 percent reported it to be the same, while 60 percent rated it more difficult to fit. A User's Manual was provided with shipment of each Arm. This manual gave information for fitting, training, and checkout of the Arm. The prosthetists provided the following collective recommendations for revision of the instructional manual:

  1. Instructions did not clearly explain the smart function of the elbow. Diagrams/schematics of elbow set-up need to be included. Guidelines are needed for cable routing and adjustments, and wrist installation, and requirements are needed for adjusting TD tension/slack cable for setting up the TD in both pronation and supination. Difficulty was experienced when deciding where to set knot for terminal ball. It would be worth noting the position of the tension take-up pulley.
  2. The type of wrists to be used with arm should be included.
  3. Having an instructional video available showing set-up and assembly of arm should be considered.
  4. A troubleshooting guide should be included. An example of a problem would be how to attach the TD cable to the TD. The instructions did not explain that the cable had to be pulled as far as possible before attaching it to the TD. The fitting was more difficult due to minimal instructions.
  5. Technical/functional specifications for the arm (i.e., lifting limit when elbow locked at 90°) should be provided. A discussion of variables between this elbow function and the Hosmer elbow should also be included.
  6. Guidelines for cosmetic covering should be included. Problems were experienced with a soft cover fabricated over the forearm. This made adjusting the forearm lift knob very difficult when changing TDs of different weight. A finishing kit is needed--"right now it is a guessing game."
  7. The fact that the elbow does not fully extend (has 10°-15° flexion) needs to be addressed. It may be important to some users to have full extension at the elbow.
  8. Training guidelines with diagrams to illustrate control motions of elbow operation (i.e., elbow lock/unlock movements) should be included. It is difficult for the user to know when the elbow lock has been actuated.
  9. The three-lift assist springs available for use with the arm should be identified.
  10. Unilateral versus bilateral fitting requirements need to be fully addressed.

  During the initial fitting phase, the HOSMER Passive Wrist Unit # 71983 and the HOSMER Constant Friction Wrist Unit # 71988 were identified for use with the AdVAntage Arm.

  Prior to shipment of the Arm for fitting, prosthetists were asked to identify whether their subjects used a quick-disconnect wrist unit and if a heavier lift assist spring would be required. A wrist interface adapter, custom-made by the manufacturer, was provided for use with the quick-disconnect wrist and the appropriate lift assist spring was installed before shipment of the arm to the prosthetist.

  In all instances, subject training was required. Sixty percent of the prosthetists found the length of training time to be acceptable, while 40 percent felt that it was unacceptable. More than half of the subjects were long-time wearers of their arms and required a longer period to appropriately control the elbow and TD; specifically, the proper shoulder motions necessary for getting the control cable to lock/unlock the elbow and actuate the TD. Prosthetists also reported subjects experiencing some frustration in knowing when, and if, the elbow lock had been actuated. Overall, 13 percent of the prosthetists rated the training requirements excellent; 47 percent rated them satisfactory, and 40 percent rated them as poor.

  Prosthetists were also asked to rate the features shown in Table 4: For any ratings of Fair or Poor, the following comments were provided:

  1. "Due to unfamiliarity with product and quality of cable material."
  2. "Limits possibility of quick disconnect for use with various terminal devices."
  3. "Use of a soft cover made adjusting the forearm lift knob very difficult when changing to TDs of different weight."
  4. "Shortening of cable housing is complicated because of polymer lining and type of cable used. There is too much friction at outlet to TD."
  5. "Some difficulty was found when deciding where to set knot for terminal ball."
  6. "Poor means of determining what cycle elbow controls are engaged."
  7. "Difficult to thread the nylon through housing and cut housing to length and rethread (time consuming)."
  8. "Multiple shortening of the forearm and cable housings were very labor intensive and required specialized procedures to do them."
  9. " In the E-400 elbow only one motion was required for a state change. In the AdVAntage elbow, at least two motions are required for the same state change. This means more overall motion for the patient."
  10. "The TD cable, with its posterior exit point, has caused some difficulty when rotating the TD. The housing must wrap around the forearm tube when the TD is rotated to the extreme position and supination. Would prefer an anterior cable exit to TD for a more direct pull."

Table 4.
Prosthetist's rating of features of AdVAntage Arm (N=15).


FEATURES % GOOD % FAIR % POOR

Front Elbow Hinge 53 40  7
Dual Cable Control 33 47 20
Spring-Powered Cable Recovery 67 26  7
Adjustable Cable Pull-Life Assist 60 27 13
Internal Cable Routing w/Polymer Material 13 54 33
Weight 93    7
Maximum Elbow Flexion Angle 93    7
Actuation Cable Excursion 80  7 13
Elbow Locking Positions 73 27  
Adjustable Forearm Length 73 20  7
Shoulder/Humeral Motions 53 20 27

  Prosthetists were asked to compare the Arm with conventional body-powered arms in specific areas shown in Table 5.

  For any rating of Worse, the following comments were given:

  1. "The forces required to flex a conventional elbow-forearm system can be modified in two ways: the forearm lift assist and the location of the forearm lift tab. The latter has been very useful to modify these forces when using different TDs and varying forearm lengths. The AdVAntage Arm, not having a variable lift tab, must rely on the spring assist. I think it needs easier adjustment and greater potential for assist."
  2. "The subject experienced some frustration in knowing when the elbow lock has been actuated. I believe his conventional system has more resistance and also offers the two audible clicks as feedback."
  3. "In using a shoulder saddle harness over a figure-eight, the route of the toggle cable is just inferior to the axilla. This has caused difficulty in activation for subject when wearing a coat. I think added resistance would help this."
  4. "The elbow is larger even though the forearm is smaller. A custom cover has to be made."
  5. "At full flexion, elbow lock/unlock does not always (consistently) function as it should. It takes several attempts at getting control cable to allow lock/unlock."
  6. "Cable routing more complex."
  7. "Tubular construction not realistic looking. Requires cosmetic cover."
  8. "Elbow range of motion does not come into full extension."
  9. "Not acceptable when an individual wants various TDs (i.e., golfing, fishing, and hand attachments)."
  10. "When you remove cable from TD, elbow becomes non-functional, unlike conventional arm. The elbow cannot be locked into position for a fishing pole TD which does not require TD control."
  11. "Location of housing--the way it exits the cosmetic cover is poor. It makes rotation of the wrist difficult."

Table 5.
Prosthetist's comparison of AdVAntage Arm to conventional body-powered arms (N=15).


FEATURES % BETTER % SAME % WORSE

Weight 100    
Cosmesis 27 27 46
Elbow Range of Motion 60 27 13
Flexion Angle 53 40  7
Terminal Device Control 53 27 20
Elbow Lock Control  7 40 53
Cable Routing 20 20 60
Actuation Cable Excursion 40 47 13
Lift Assist/Gain 33 60  7
Elbow Locking Positions 27 73  
Adjustable Humeral Rotation Friction  7 93  
State Change Control 33 27 40
Function 43 37 20


Amputation levels
Figure 5. Prosthetist's recommended amputation levels for prescription of the AdVAntage Arm (N=15).

  Figure 5 indicates various amputation levels that the prosthetists felt would benefit from using the Arm:

  Prosthetists who indicated No for use of the Arm by the above amputation levels gave the following comments:

  1. " Not for anyone who wants a hand or any specialty TD attachment."
  2. " Because of the increase of shoulder motions required for the state change, would make it difficult for users with shoulder disarticulation (SD), forequarter, and bilateral amputations."
  3. " Harnessing issues need to be resolved for bilateral consideration."

  As indicated earlier, there were two bilateral fittings. Harnessing problems were experienced that inhibited one subject's ability to function with the Arms. He had a bilateral short THA. For a person with bilateral THA, each control cable is dependent on the opposite arm (i.e., to open the left TD, the right prosthesis provides the support). As this subject would try to open his left TD, the hanger and actuator cable on the right prosthesis would shift toward the left. This resulted in the subject not getting adequate excursion of cable/harness system through either bilateral scapula abduction or humeral flexion. As the subject tried to open the left TD, the right arm uncoiled causing the hanger to shift left. The rewinder on each arm must have a more positive stop to prevent uncoiling of opposite arm. The subject was not able to get either TD to mouth (the TDs missed by approx. 20.32-22.86 cm).

  The second subject with bilateral amputation had a short THA on the right and a forequarter on the left. His fitting was completed and he has been able to function with the arms.

  Out of the 14 unilateral fittings, four involved short THAs, of which two were on left side and the remaining two on the right. There was a reported problem with fitting one of these subjects. The subject had a very short (2.54\7.62 cm) residual limb on the left side. The prosthetist felt that the elbow provided functioned as a right elbow. Even though he was able to complete the fitting, he indicated that the harnessing and suspension, in conjunction with the right and left side problem, were responsible for many of the fitting problems he encountered with this subject.

  The above issue concerning right and left sidedness was brought to the attention of the manufacturer. In providing a response, they reviewed the matter with a consulting prosthetist. While both the control cable and lock/unlock cable are offset from midline toward what would be the subject's left, it does not necessarily compromise the ability to effectively fit a right THA. However, the prosthetist cannot use the same standard control cable routing and mounting for an individual with amputation on the right as he can with one on the left. In routing the cable in case of the former, one must use more of a European style cable routing in which the cable is routed more toward the medial side of the socket rather than the lateral side as is typical in the United States. While this may be somewhat unusual, it has little apparent effect on the efficiency of the control cable, since most of the fittings went well. Based upon this information, a section will be added to the instructional manual instructing prosthetists on how to route the cables to include the total fitting.

  Five prosthetists were able to provide a custom cosmesis for the Arm using a soft forearm cover. Each accomplished this, based upon his or her prosthetic experience, since no instructions addressing this topic were included in the manual. There were difficulties encountered that included the inability to adjust lift assist after the cover was in place.

Subject Response (30- and 90-Day Post-AdVAntage Arm)
  Subject trials consisted of a 30- and 90-day follow-up from the date of completed fitting. At the end of each follow-up period, the subject was asked to complete a data instrument to record responses pertaining to each subject's use of the Arm. This comparative data assessed the Arm for improved function and utility over the subject's conventional body-powered AE prostheses.

Subject Response (30-Day Post-AdVAntage Arm):
  An overall synopsis of the subjects' responses with regard to performance and characteristics of the Arm was made from data received and a review of their comments.

  A majority of the subjects (74 percent) used the Arm for more than 5 hours per day and between 3-7 days per week (54 percent). In Table 6, subjects compared prosthetic features of the Arm.

Table 6.
Subject's comparison of AdVAntage Arm features: 30-days
post (N=15).


FEATURES % WORSE % NO CHANGE % BETTER % N/A

Elbow Control 54 13 34  
Terminal device control 13 27 34  
Cable control system 27 27 46  
Ease of use 40 20 40  
Reliability 33 47 20  
Forearm Lift 13 40 47  
Cosmesis 27 33 40  
Noise level 20 40 40  
Weight  7 33 60  
Training 36 28 36  
Durability 20 60 20  
Donning/Doffing 13 74 13  
Suspension system  7 80 13  
Comfort 13 27 60  

  Fifty-three percent of the subjects experienced some malfunction with his or her prosthesis. The elbow unit was the item that needed the most frequent repair or adjustment. The majority of these subjects found the length of downtime to be acceptable.


Subject rating graph
Figure 6. Subject's rating of TD function of AdVAntage Arm: 30-days post (N=15).

  In Figure 6, subjects rated TD function of the Arm for specific activities. For any item rated No or Not Done, the following comments were provided:

  1. One subject had limited use due to an unplanned hospitalization.
  2. Not reliable enough when doing tasks.
  3. Not able to use arm at and around head due to shoulder fusion (fused at 35° flexion and 15° abduction).
  4. Needs more training.
  5. Requires too much effort to operate.

  Eighty-seven percent of the subjects indicated that the Arm did not snag their clothing during use. Forty-seven percent reported that using the arm has made it easier and allowed them to perform more activities of daily living. Figure 7 provides subjects' overall rating of the AdVAntage Arm after completing 30-days use.


provides subjects' overall rating
Figure 7. Subject's overall rating of AdVAntage Arm: 30-days post (N=15).

Subject Response (90 -Day Post-AdVAntage Arm):
  After 90-days use, 11 subjects completed a 90-day data instrument. A majority of subjects (64 percent) continued to use the Arm for more than 5 hours per day and between 3-7 days per week (55 percent). In Table 7, subjects compared prosthetic features of the Arm to their present prosthesis. Seventy-three percent experienced some malfunction with their current prosthesis. The elbow unit most frequently needed repair or adjustment. The majority of these subjects found the length of downtime to be acceptable.

Table 7.
Subject's comparison of AdVAntage Arm features: 90-days
post (N=11).


FEATURES % WORSE % NO CHANGE % BETTER % N/A

Elbow Control 46 18 36  
Terminal device control  9 18 73  
Cable control system 27 27 46  
Ease of use 36 18 46  
Reliability 36 28 36  
Forearm Lift 27 18 55  
Cosmesis 18 55 27  
Noise level 36 18 46  
Weight   36 64  
Training 27 46 27  
Durability 18 46 36  
Donning/Doffing  9 82  9  
Suspension system   73 27  
Comfort   36 64  


figure 8. Subject's rating of TD function of
Figure 8. Subject's rating of TD function of AdVAntage Arm: 90-days post (N=11).

  Figure 8 provides subject's rating of TD function using the Arm for specific activities. For any item rated No or Not Done, the following comments were made:

  1. "Cannot reach side of head secondary to shoulder fusion."
  2. "Can't tell when elbow is locked to open TD."
  3. "More training needed."

  Eighty-two percent of the subjects indicated that the Arm did not snag their clothing during use. Fifty-five percent reported that using the arm has made it easier and allowed them to perform more than ADLs (i.e., putting seeds in bird food hopper; Working in cramped positions such as under the sink, kneeling, or working in the garden; working on fine detail tasks such as puzzles and hobbies; holding and shooting a rifle).


Overall rating
Figure 9.Subject's overall rating of AdVAntage Arm: 90-days post (N=11).

  Figure 9 provides subjects' overall rating of the Arm after completing 90-days use, with the following general:

  1. "The arm can be adjusted to fit my needs."
  2. "It functions in a more fluid manner, requiring less energy."
  3. "It is lighter."
  4. "The cloth cable has a lower coefficient of friction than the conventional steel cable and housing. This reduces the energy I use to lift the forearm and open the hook."
  5. "Better control of TD especially at outstretched or overhead positions."
  6. "Once elbow is locked, the hook works at all angles."
  7. "The arms are much more comfortable and enable me to do things with much more ease."

  At the conclusion of their clinical trials, 10 subjects elected to keep the Arm for continued use. Nine of the subjects had unilateral amputation with seven having standard length THA levels and two with short THA. Two of these subjects had limited shoulder ROM. The one bilateral subject had a short THA on the left side and a forequarter level on the right.

  Of the six who did not keep the Arm, five were unilateral and one was bilateral. Of the five unilateral subjects, three had standard length THA, and two had short THA. One subject suffered a mild stroke and had to return the Arm. The subject with bilateral amputation had short THA levels on both sides. Several of the subjects remarked that if the suggested modifications were incorporated into the Arm, they would be willing to try it again.

Maintenance and Repair
  During the course of the clinical trials, instances of product failure were reported and documented on the evaluation maintenance and repair log (TTS 105 data instrument). The manufacturer provided technical assistance to all participating sites throughout the trials and assigned a technical liaison to handle all problems identified by the field. All technical issues and malfunctions were handled in an expeditious manner, which ensured continuity of the clinical trials. The following is a summary of the problems and resolutions: [nl]1. Three failures occurred that involved the elbow locking pin sticking. The arms were shipped back to the manufacturer for pin adjustment. Based upon this problem, the pin adjustment was made to all subsequent arms.

DISCUSSION

  Results from the clinical trials demonstrated that the Arm (with revised design changes) could be fit for use by individuals with THA. Once the subject developed expertise and overcame the learning curve, the Arm offered several functional advantages over conventional arms. Its overall lightweight, unique separation of the elbow movement mechanism from TD actuation, and cable recovery system, which allows opening and closure of the TD at any elbow position using the same cable excursion, proved beneficial for many of the THAs.

  Resultant data led to the following summation of the precommercial AdVAntage Arm:

Advantages

Disadvantages

Prescriptive Indications
  The AdVAntage Arm, in its present configuration, would be indicated for use by persons with unilateral THA with

  The Arm would be indicated for use by persons with bilateral THA dependent upon the harnessing arrangement, which must be able to provide proper separation of control.

Contraindications
  The Arm, in its present configuration, would not be indicated for persons

Recommended Modifications
Primary

Secondary

CONCLUSION

  Based upon the results of this multi-center clinical evaluation, the Arm offers improved function over existing body-powered arms and can be prescribed for use by appropriate persons with unilateral and bilateral THA.

  The modifications identified during the clinical trials have been brought to the attention of the manufacturer, who has provided the following solutions to most of the identified issues. Several may require more investigation and further consumer feedback from the commercial market.

  1. Prototype cosmesis designed and fabricated
  2. New manual completed, including revised fitting instructions and training section
  3. Lock pin redesigned to improve consistency of lock/unlock position
  4. Improved isolation to decrease ratchet noise
  5. QD wrist adapter for TD replacement (Hosmer components)
  6. Forearm, humeral pieces and lock pin redesigned for increased strength and durability for heavy duty use

  The ability of the manufacturer, who is committed to the commercial marketing and technical support of the Arm, to handle technical issues as they arose was demonstrated throughout the clinical trial by their quick resolution and turnaround time. The modifications, as identified in this report, are provided to guide the manufacturer and will only serve to enhance the Arm's performance, clinical application, and commercial success.

  As a result of the VA's partnership in the technology transfer of this product, there will be preferential pricing for all federal purchases of the Arm. In addition, all commercial literature will credit the Department of Veterans Affairs Rehabilitation Research and Development Service for sponsoring the research, development, and technology transfer of this product.

RECOMMENDATION

  Results of this clinical evaluation demonstrated that the AdVAntage Arm has proven to be acceptable for use by appropriate veterans with amputation. The AdVAntage Arm is recommended for commercial production.

ACKNOWLEDGEMENTS

   The authors would like to acknowledge, with gratitude, the efforts of Frederick Downs, Jr., Chief Consultant Prosthetics and Sensory Aids Service (PSAS) and John Clements, Prosthetic Regional Manager, PSAS, VA Headquarters, for their contribution in planning and accomplishing this evaluation.

  A special thanks is extended to all veterans who most graciously gave of their time to participate and provide critical information during this evaluation.

  Appreciation is also expressed to the following VA Medical Center (VAMC) personnel who provided cooperation and assistance throughout the clinical trials: Andy J. McKinney, Chief PSAS, VAMC Huntington, WV; Barry Gray, Chief PSAS, VAMC West Haven, CT; Barbara Mueller, Amputee Coordinator, PSAS, VA Northern California System of Clinics, Pleasant Hills, CA; Donald Freyberger, Chief, PSAS VAMC Tampa, FL; Bernadette Kiser, PSAS, VAOPC Orlando, FL; J. Robin DeAndrade, MD PACT (Preservation, Amputation, Care and Treatment) Director; James Blaylock, Chief PSAS and Jerome Brown PACT Coordinator, VAMC Atlanta, GA; John Milani, Chief, Prosthetic and Orthotic Lab, VAMC New York, NY; John Redford MD, Chief, Physical Medicine & Rehabilitation (PM&R) Service and Robert Newson, Chief, PSAS, VAMC Kansas City, MO; Mary Jane Morrison MD, Chief PM&R Service and Kevin Labarbara, Chief PSAS, VA Domiciliary White City, OR; Miles Colwell, MD, PM&R Service, Judy Witzke, Chief, PSAS and Sally Hoeft, OTR, VAMC Ann Arbor, MI; Owen Dillon, MD, Chief, Amputee Clinic and Ben Rogers, Chief, PSAS, VAMC Washington DC; Patsy Kendall, Chief PSAS, VAMC Boise, ID; Ron Bailey, Chief PSAS, Martin McDowell, CPO, Chief Orthotic Lab and Heather Vial, OTR, VAMC Seattle, WA; Trevor Noguerira MD and Lorraine Kleinberg, Chief PSAS, VAMC Las Vegas, NV.

  Special recognition is extended to Sanford G. Meek, PhD, Center for Engineering Design, University of Utah, Salt Lake City, UT; Stephen C. Jacobsen, PhD, Chairman and CEO and Tomasz Petelenz, PhD, Technical Director, Medical Systems, SARCOS Research Corporation, Salt Lake City, UT.

REFERENCES

  1. LeBlanc MA. Innovation and improvement of body-powered arm prostheses: a first step. Clin Prosthet Orthot 1985;9(1):13-6.
  2. Childress DS. Historical aspects of powered-limb prostheses. Clin Prosthet Orthot 1985;9(1):2-13.
  3. LeBlanc MA. Current evaluation of hydraulics to replace the cable force transmission system for body-powered upper-limb prostheses. Assist Technol 1991;2:101-7.
  4. Doeringer JA, Hogan N. Performance of above elbow body-powered prostheses in visually guided unconstrained motion tasks. IEEE Trans Biomed Eng 1995;42(6):621-30.
  5. Muilenburg AL, LeBlanc MA. Body-powered upper limb components. In: Atkins DJ, Meir III RH, editors. Comprehensive management of the upper-limb amputee. New York: Springer-Verlag Publishing Co., 1989:5:30.
  6. Shurr DG, Cook TM. Upper extremity prosthetics. In: Shurr DG, Cook TM, editors. Prosthetics and orthotics. Connecticut: Appleton & Lange Publishing Co.; 1990. p. 151-71.
  7. Wooten C. Harnessing the power: control systems for upper extremity prostheses. In Motion 1995;5(4):19-20.
  8. Prescription of upper extremity limbs. In: Department of Veterans Affairs Clinical Affairs Letter: IL 11-88-4. March 9, 1988.
  9. Jacobsen SC, Knutti DF, Johnson RT, et al: Development of the Utah artificial arm. IEEE Trans Biomed Eng 1982;BME-29:4:249-69.

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