Overview and Description
In 2005, an estimated 540,000 individuals in the United States were living with an upper limb loss, of which approximately 40,000 were amputations above the wrist. This number was projected to double by 2050.1 (Unfortunately, more recent data on individuals living with an upper limb loss has not been collected since 2005, although a Limb Loss and Preservation Registry is being developed to better understand amputee challenges and needs. National Institutes of Health is partnering with the Department of Defense (DoD) on the project, which will be led by the Mayo Clinic). The most frequent causes of upper limb amputation are trauma, vascular complications of disease, and cancer. Trauma due to work-related injuries are the most common cause in civilians. Additionally, military personnel sustain combat related injuries most commonly due to improvised explosive devices (IEDs). Previously, the Operation Iraqi Freedom reported extremity injuries to be as high as 50% but has recently decreased to 20% with improvements in protective gear.2,3 Upper limb amputations are delineated at the wrist joint; distal to the wrist are considered minor amputations, whereas proximal to the wrist are major amputations. Amputations can occur at the forequarter (interscapulothoracic), shoulder, transhumeral, elbow, transradial, wrist, transcarpal, transmetacarpal, and transphalangeal level. The most common major upper limb amputation is at the transradial level, which accounts for over half of all major arm amputations.4,5
In 2016 over 10,000 upper limb amputations occurred in the United States. Of these amputations 5.2% occurred at the wrist disarticulation and transradial level, 6.1% were elbow disarticulation or transhumeral, and 2.3% were at the shoulder or higher. The majority 75.6% were finger amputations.6
Prosthetic prescription and use is one of the primary treatments of disability as a result of amputation in an effort to restore functional independence and improve quality of life.
Time is of the essence when dealing with upper limb amputation and prosthetic restoration. Delay in initial prosthetic fitting and training is a major factor for prosthetic rejection/abandonment.7 Therefore, the amputee rehabilitation program should ideally begin prior to amputation. The complicated movements and functions of the upper extremity have yet to be replicated with prostheses and patients that utilize prosthetics often cite limited dexterity as the primary reason for abandoning the prosthesis.8 The need for a multidisciplinary team approach is acknowledged in the first evidence-based clinical practice guidelines for the rehabilitation of persons with upper-limb amputation, released in 2014.9
Relevance to Clinical Practice
Factors to consider when selecting prosthetic components are amputation level, residual limb geometry, sensation, range of motion, strength, cognition, vocation, hobbies, importance of cosmesis, financial resources available, and environment and weather. Collaboration between the patient and physiatrist-led rehabilitation team should be in place at the time of prescription. Major components of upper limb prostheses include the terminal device (TD), interposing joints, socket, suspension, and control system. Typically, there are three general classes of upper extremity prostheses: cosmetic, body-powered and myoeletric.10 There are also hybrid type prostheses available. When considering the type of device prescribed and the type and amount of prosthetic training prescribed, a comprehensive clinical assessment by a trained multidisciplinary team can help in assessing their appropriateness and readiness for use of an upper limb prosthesis. It can guide the prescription of an appropriate device or devices and a training program to meet the individual’s needs.11
Prostheses can be controlled using body-powered, externally powered, or hybrid control systems. Body-powered systems use body movements to control a TD and/or elbow. Advantages of the body powered systems include durability, reduced cost, and weight compared with other systems. They also offer some proprioceptive feedback to the user.
Externally battery-powered systems may use electric switches or myoelectric signals for control. Electric switches can be activated by residual limb movements within the socket or by other body parts. Myoelectric systems use electromyographic (EMG) signals generated during muscle contractions. They provide digital or proportional control. With digital control, the system triggers an on/off signal regardless of the intensity of the electromyography. With proportional control, the motor action is proportional to the EMG signal amplitude allowing for variable speed and force. Externally powered systems reduce the need for harnessing and require less movement for activation, but they are heavier, expensive, and require more maintenance than body-powered devices.
Hybrid control systems combine body and external power control in an effort to balance weight, cost, and cosmesis and accommodate different anatomic levels. The literature is insufficient currently to determine the functional superiority of myoelectric versus body powered prostheses. Body powered prostheses are generally more robust and can be used in wet or dirty environments and generally require shorter training periods. Myoelectric devices can provide better cosmesis, improve phantom limb pain and are more accepted for light intensity work.12 Many prosthetic users frequently use multiple devices on a daily basis. One survey of 50 service members from the Operation Enduring Freedom/Operation Iraqi Freedom with unilateral amputation found that within 1 year of their amputation many used more than one type of device.13
The current level of prosthetic technology is far from replacing the versatility and coordination of the human hand, although technology and prosthetics is continually advancing. Prosthetic TDs include passive, body-powered, and externally powered hooks and hands. Passive TDs are used primarily for cosmesis.
Prosthetic hands provide 3-jaw chuck pinch, and hooks provide the equivalent of lateral or tip pinch. Body-powered control allows for voluntary opening (VO) or voluntary closing (VC) of the TD, but not both. VO devices are maintained in the closed position by rubber bands or springs. VC devices are maintained in the open position and close when tension is applied through a cable connected to a harness. VC TDs are capable of applying more force, but VO TDs are more practical because tension does not need to be maintained when holding objects.
Externally powered TDs can have digital or proportional control and can open or close as desired and offer the advantage of higher grip force. Typically, these terminal devices replicate the pinching or squeezing function rather than the use of each individual finger.
The lightest and simplest prosthetic wrist is a friction control unit, which permits passive pronosupination of the TD but can rotate when lifting heavier objects (e.g., a plate of food). A locking, quick disconnect wrist allows locking in the desired pronation/supination position and rapid interchange between different TDs. Spring-assisted wrist flexion is helpful to bilateral amputees to permit midline reach for activities of daily living (ADLs). They may also benefit from spring-assisted wrist rotation.
Externally powered wrist units are prescribed primarily for bilateral transhumeral or higher levels of amputation. Some wrists are capable of 360˚ rotation, which can be used for key turning or operating a screwdriver.
Body-powered elbows can have spring-assisted flexion. External mounted elbows are indicated for elbow disarticulations in attempts to maintain optimal proportional arm length. Passive and body-powered elbows have a locking mechanism that can be activated with the contralateral hand, chin, or ipsilateral shoulder. When used with a body-powered TD, the elbow must be locked in order to operate the TD.
Externally powered elbows can be controlled with a switch or myoelectric control. Internal and external rotation can be provided with a rotating turn table, which enables midline reach.
Most shoulder joints allow passive abduction and flexion through a bulkhead or universal joints with the desired position maintained by friction, chin control, or electric lock. However, there is increased risk of nonuse because of a combination of weight, diminished overall control across multiple joints, and increased effort with shoulder or forequarter amputations. Powered shoulders with electronic controls are in development that utilize the sensing of shoulder protraction and elevation- depression, which will promote better prosthetic control for individuals with high level transhumeral amputations.14
Most upper limb prosthetic sockets are double layered and composed of external carbon graphite or rigid plastic materials to which the necessary prosthetic components are attached. The inner socket is fabricated from a cast of the patient’s residual limb and can be constructed of a flexible plastic. Windows can be cut in the outer socket to allow for inner socket expansion. Although more costly to fabricate, the frame design allows for inner socket replacement to accommodate residual limb volumetric changes.
The major suspension types are harness, anatomic, friction, and suction suspension. Socks can be used in most suspension systems as an interface between the residual limb and socket to accommodate for physiologic volume changes that occur during the day and protect the skin and improve hygiene. Socks cannot be used in suction suspension because these require direct skin to socket contact.
The harness suspends the prosthetic device to the body while providing body-powered control. A figure 8 harness is commonly used for transradial and transhumeral amputees. A harness loops around the contralateral axilla to anchor the suspension and control cables. A chest strap is an alternative for those who find the axillary pressure uncomfortable. A shoulder saddle with a chest strap can be used in more proximal amputations and for those who do heavier lifting.
A cable connected to the harness allows transmission of body power for prosthetic control. A cable used to activate a single prosthetic component is called a single-control cable or Bowden cable system. A dual-control cable system uses one cable to control two prosthetic functions (eg, flexion of the elbow, activation of the TD). This is accomplished by passing a single cable through two separate sections of cable housings (fair lead cable system). In transradial and transhumeral amputations, biscapular abduction and/or humeral flexion control elbow flexion and/or the TD. However, the elbow must be locked for activation of the TD in transhumeral amputations. In order to lock or unlock the elbow, shoulder depression, humeral abduction, and humeral extension are performed simultaneously. Patients with shoulder disarticulation perform biscapular abduction to control the elbow and TD with scapular elevation to lock the elbow.
Anatomic (self-suspension) systems use bony prominences for suspension encasing the medial and lateral epicondyles, with some loss in terminal elbow range of motion. The supracondylar (Müenster or Northwestern) suspension is used with transradial amputations and some wrist disarticulations. A figure 9 harness can be incorporated for TD control only. This suspension works well with externally powered prostheses and is less restricting when flexible materials are incorporated in the design.
Silicone sleeves provide suspension by creating negative atmospheric pressure and an adhesive bond to the skin. The sleeve also protects the skin by reducing shear forces and cushioning. Therefore, it is useful when the skin is delicate because of scars or injury. It is easily donned with one hand and allows for some residual limb volume change accommodation. There is often a distal attachment pin that interfaces with a shuttle lock mechanism built into the socket. After spraying the external surface with lubricating fluid, the patient rolls the sleeve directly over the skin. Once in place, socks can be applied to improve fit. Disadvantages to this suspension are that excessive perspiration and skin irritation can occur, which limit their use in warm and humid weather.
Suction suspension is preferred for transhumeral amputees with externally controlled devices. The patient dons the socket using a pull sock or lubricant fluid with a 1-way valve to allow for expulsion of air to create negative pressure. For this system to work well, it requires intimate fit between the residual limb and socket to create a tight seal; therefore, the limb volume should be stable with minimal surface irregularities.
Expected functional outcomes and realistic goals for most unilateral transradial and transhumeral amputees are independence in all ADLs, household activities, and driving. Some limitations regarding work and household chores may be necessary, especially when dealing with the handling of delicate, heavy, or voluminous objects. Bilateral amputees should be able to perform most ADLs and household activities after assisted donning of the prosthesis. They may also drive with a spin ring and perform some sedentary work with environmental modifications.
Cutting Edge/ Unique Concepts/ Emerging Issues
The overarching goal for upper extremity prosthetics and the advancement in technologies in this realm is to recreate the complex functions of the human hand. Concepts being developed are prosthetic hands with independently powered finger movements, targeted muscle reinnervation, osseointegration, neural prosthesis interfaces, and incorporation of tactile feedback.15,16 Improvement in power supply, sensors, and newer materials and reduction in the size and weight of motors should allow for further improvement in prosthetic manufacturing. The advent of 3-dimensional printers also have the potential to reduce the costs of prostheses as well as allow for larger degrees of customization.
New technologies for myoelectric prostheses
Recently, pattern recognition technology has allowed the user to correlate a specific EMG pattern with a corresponding preprogrammed action rather than previously simply “hand open” or “hand closed” models. This advancement allows for more simultaneous control of multiple degrees of freedom, more initiative and adaptable control of the prosthesis and elimination of the need for mode switching. Additionally, there have been surgical advancements as well such as target muscle reinnervation that complement the advances in pattern recognition technology. Myoelectric sensors can be implanted beneath the skin to improve the prosthetic function and control.
Devices that attach directly to nerves that can detect both efferent and afferent signals are under investigation one of these devices is the Utah Slanted Electrode Array (USEA). What was promising about the study involving this device was that individuals were able to regain control of individual fingers of a virtual robotic hand.17
Osseointegration is an emerging surgical technique designed to bypass the impact of the socket on the success of fitting the prostheses. Currently in the US this has not been approved by the FDA for the use in upper limb applications. An additional and cutting edge concept in osseointergration is the incorporation of motosensory devices into the implant itself. 18 The e-OPRA device for example contains a bidirectional interface using electrodes integrated with the device to improve control of the osseointegrated prosthesis, the e-OPRA is currently undergoing clinical trials in the US with the study completion date of Jan 2023.19
3D Printing in Upper limb prosthetics
3D printing was developed in the late 1980s and since 2010 there was significant advancement in the 3D printing of upper extremity prostheses. There have been many publications in the scientific community about research regarding the field of 3D-printed upper limb prostheses. Currently the global community e-NABLE has grown into a worldwide interdisciplinary movement.20 Largely the development of 3D printed upper extremity prosthetics came about due to a necessity to develop more affordable hand prosthesis, the typical cost of a commercial body powered prosthetic hand can range from $4,000 to $10,000 and the cost of an externally powered prosthetic hand can range from $25,000 to $75,000.21
Virtual Reality and advanced rehabilitation
Many interdisciplinary teams (rehabilitation physicians, therapists, and prosthetists) have begun to implement virtual reality programs to optimize prosthesis design, incorporation and use. This technology has been used twofold on the design side and the training side. The virtual limb prosthesis has been used to test devices prior to their construction in a virtual reality environment.22 Also there have been some advancements with a virtual reality program to efficiently train upper extremity amputees where these individuals learn to control a virtual avatar over 1 to 2 months.23 Game-based training has been shown to improve myoelectric prosthesis use (such as muscle control) and could potentially improve rehabilitation success through enhanced training outside the clinic.24
Gaps in Knowledge/ Evidence Base
Upper extremity prosthetics research is currently investigating sensory feedback to prosthesis users. All of the current devices fall short of restoring the sense of touch or proprioception of the amputated appendage. This loss of sensation makes control of grip force problematic, as prosthesis users cannot tell how hard they are gripping objects; thus, they are susceptible to dropping items because of too little or improper grip or to crushing fragile items by using a stronger grip than intended. This is an area of prosthetics that needs further development.25
Additionally, there is a gap in knowledge about the impact of upper-limb loss, prosthesis use and amputation rehabilitation on activity and participation, specifically work participation. This may develop a rational of resource utilization cost-benefit analyses and coverage for devices and related services.26
Also there are no universally accepted guideline for prescription of prosthetics and training in their use.27 Data do not exist on the location and distribution of expertise, such as centers of excellence in the care of persons with upper- limb amputation across the US. There is no standardization for upper extremity prosthetic centers of excellence except in the Veterans Health Administration (VHA), where access to services is limited to veterans.28
- Ziegler-Graham K, Mackenzie E, Ephraim P, et al. Estimating the prevalence of limb loss in the United States: 2005 to 2050.Arch Phys Med Rehabil.2008;89:422-429.
- Dougherty AL, Mohrle CR, Galarneau MR, et al. Battlefield extremity injuries in Operation Iraqi Freedom. Injury 2009; 40:772.
- Tennent DJ, Wenke JC, Rivera JC, Krueger CA. Characterisation and outcomes of upper extremity amputations. Injury 2014; 45:965.
- Glattly H. A statistical study of 12,000 new amputees.South Med J.1964;57:1373-1378.
- Kay H, Newman J. Relative incidence of new amputations: statistical comparisons of 6,000 new amputees.Orthot Prosthet.1975;29:3-16.
- O&P Almanac. Amputation data from community hospitals. O&P Almanac. 2016 April:8.
- Malone J, Fleming LL, Roberson J, et al. Immediate, early, and late postsurgical management of upper-limb amputation.J Rehabil Res Dev.1984;21:33-41.
- Esquenazi A. Amputation rehabilitation and prosthetic restoration. From surgery to community reintegration.Disabil Rehabil.2004;26:831-836.
- Management of Upper Extremity Amputation Rehabilitation Working Group. VA/DoD clinical practice guideline for the management of upper extremity amputation rehabilitation. Washington, DC: VA, Department of Defense (DoD); 2014.
- Pierrie SN, Gaston RG, Loeffler BJ. Current Concepts in Upper-Extremity Amputation. J Hand Surg Am. 2018 Jul;43(7):657-667. doi: 10.1016/j.jhsa.2018.03.053. Epub 2018 Jun 2. PMID: 29871787.
- National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Health Care Services; Committee on the Use of Selected Assistive Products and Technologies in Eliminating or Reducing the Effects of Impairments; Flaubert JL, Spicer CM, Jette AM, editors. The Promise of Assistive Technology to Enhance Activity and Work Participation. Washington (DC): National Academies Press (US); 2017 May 9. 4, Upper-Extremity Prostheses.
- Carey SL, Lura DJ, Highsmith MJ. Differences in myoelectric and body-powered upper-limb prostheses: Systematic literature review. Journal of Rehabilitation Research & Development. 2015;52(3):247–262.
- McFarland LV, Winkler S, Jones MW, Heinemann AW, Reiber GE, Esquenazi A. Unilateral upper limb loss: Satisfaction and prosthetic device use in service members from Vietnam and OIF/OEF conflicts. Journal of Rehabilitation Research & Development. 2010;47(4):275–298.
- Barton JE, Sorkin JD. Design and evaluation of prosthetic shoulder controller. J Rehabil Res Dev. 2014;51(5):711-726. doi:10.1682/JRRD.2013.05.0120
- Behrend C, Reizner W, Marchessault J, Hammert W. Update on advances in upper extremity prosthetics.J Hand Surg Am.2011;36:1711-1717.
- O’Doherty J, Lebedev M, Ifft P, et al. Active tactile exploration using a brain-machine-brain interface.Nature. 2011;479:228-231.
- Kuiken TA, Dumanian GA, Lipschutz RD, Miller LA, Stubblefield KA. The use of targeted muscle reinnervation for improved myoelectric prosthesis control in a bilateral shoulder disarticulation amputee. Prosthetics Orthot Int. 2004;28:245–253
- Bates TJ, Fergason JR, Pierrie SN. Technological Advances in Prosthesis Design and Rehabilitation Following Upper Extremity Limb Loss. Curr Rev Musculoskelet Med. 2020;13(4):485-493. doi:10.1007/s12178-020-09656-6
- e-OPRA Implant System for Lower Limb Amputees. In: ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT03720171. Accessed 4 Nov 2019.
- Enabling The Future [Online]. [cited 2015 Jun 19]. Available from: http://enablingthefuture.org/
- Resnik L, Meucci MR, Lieberman-Klinger S, et al. Advanced upper limb prosthetic devices: implications for upper limb prosthetic rehabilitation. Arch Phys Med Rehabil. 2012;93:710–717.
- Putrino D, Wong YT, Weiss A, Pesaran B J Neurosci Methods. A training platform for many-dimensional prosthetic devices using a virtual reality environment. 2015 Apr 15; 244():68-77.
- Perry BN, Armiger RS, Yu KE, Alattar AA, Moran CW, Wolde M, McFarland K, Pasquina PF, Tsao JW. Virtual Integration Environment as an Advanced Prosthetic Limb Training Platform. Front Neurol. 2018; 9():785.
- Melero M, Hou A, Cheng E, Tayade A, Lee SC, Unberath M, Navab N. Upbeat: augmented reality-guided dancing for prosthetic rehabilitation of upper limb amputees. J Healthcare Eng. 2019;2019:1–9.
- Schiefer M, Tan D, Sidek SM, Tyler DJ. Sensory feedback by peripheral nerve stimulation improves task performance in individuals with upper limb loss using a myoelectric prosthesis. Journal of Neural Engineering. 2016;13(1):016001
- Darter BJ, Hawley CE, Armstrong AJ, Avellone L, Wehman P. Factors Influencing Functional Outcomes and Return-to-Work After Amputation: A Review of the Literature. J Occup Rehabil. 2018;28(4):656-665. doi:10.1007/s10926-018-9757-y
- Etter K, Borgia M, Resnik L. Prescription and repair rates of prosthetic limbs in the VA healthcare system: Implications for national prosthetic parity. Disability and Rehabilitation: Assistive Technology. 2014;10(6):1–8
- Stark G. Competency, risk, and acceptance of upper limb prosthetic technology. Washington, DC: 2016. [May 16]. Presentation to the Committee on the Use of Selected Assistive Products and Technologies in Eliminating or Reducing the Effects of Impairments.
Original Version of the Topic
Alberto Esquenazi, MD, Daniel Moon, MD, Upper limb prosthetics. 9/20/2014
Laura Gruber, MD
Nothing to Disclose
Tiffany M. Lau, MD
Nothing to Disclose