Given its importance as an integral part of the human body, the loss of a hand – regardless of cause – can be a highly traumatic experience requiring extended periods of psychological and physical rehabilitation. Attempts to reintegrate hand amputees back into society using state-of-the-art, contemporary technology can be documented to as far back as antiquity and the middle ages. Despite astounding progress in the field, a highly functional, cosmetically appealing replacement has eluded clinicians and researchers. However, more recent advances in robotic technology, hand restoration and even hand transplantation have shown promising results.
Keywords:
Hand amputation, Hand amputee, Hand prosthesis, Hand transplantation, Myoeletric prosthesis, Targeted reinnervation
The hand is an integral component of the human body, with an incredible spectrum of functionality. In addition to possessing gross and fine motor capabilities essential for physical survival, the hand is fundamental to social conventions, enabling greeting, grooming, artistic expression and syntactical communication. The loss of one or both hands is, thus, a devastating experience, requiring significant psychological support and physical rehabilitation. The majority of hand amputations occur in working-age males, most commonly as a result of work-related trauma or as casualties sustained during combat. For millennia, humans have used state-of-the-art technology to design clever devices to facilitate the reintegration of hand amputees into society. The present article provides a historical overview of the progress in replacing a missing hand, from early iron hands intended primarily for use in battle, to today’s standard body-powered and myoelectric prostheses, to revolutionary advancements in the restoration of sensorimotor control with targeted reinnervation and hand transplantation.
Keywords:
Hand amputation, Hand amputee, Hand prosthesis, Hand transplantation, Myoeletric prosthesis, Targeted reinnervation
La main, dont le spectre fonctionnel est incroyable, fait partie intégrante du corps humain. En plus de la motricité globale et de la motricité fine essentielles à la survie physique, la main est fondamentale dans le cadre des conventions sociales, permettant de souhaiter la bienvenue, de se nettoyer, de démontrer son expression artistique et sa communication syntaxique. La perte d’une main ou des deux mains est donc une expérience dévastatrice, qui exige un soutien psychologique et une réadaptation physique considérables. La majorité des amputations de la main se produisent chez des hommes en âge de travailler, surtout après un traumatisme lié au travail ou d’incidents au combat. Depuis des millénaires, les humains recourent avec ingéniosité à la technologie de pointe pour concevoir des dispositifs afin d’aider les amputés de la main à réintégrer la société. Le présent article propose un aperçu historique de l’évolution du remplacement d’une main manquante, en commençant par les premières mains de fer conçues principalement pour les combats, en passant par les prothèses standards myoélectriques ou activées par le corps actuelles, jusqu’aux progrès révolutionnaires dans la restauration du contrôle sensorimoteur avec réinnervation ciblée et transplantation de la main.
From grasping and manipulating objects to grooming and communication, the versatility of the human hand is integral to both physical survival and social conventions. The loss of one or more hands is, thus, a devastating experience, requiring significant psychological support and physical rehabilitation. The majority of upper extremity amputations occur in working-age males, most commonly from occupational or combat trauma. Congenital deficiencies, cancers and vascular disease are also major causes of amputations (1). For millennia, humans have used state-of-the-art technology to help hand amputees reintegrate into society. Despite outstanding progress in this field, however, creating an ideal functional and cosmetic replacement for a missing hand continues to challenge clinicians and researchers. The present article provides a historical overview of approaches to replacing a missing hand, from early iron hands, to today’s standard prostheses, to revolutionary advancements in sensorimotor restoration.
The concept of an ‘automatic’ body-powered upper limb prosthesis was pioneered by German dentist Peter Baliff in 1818 (5). Using transmission of tension through leather straps, Baliff’s device enabled the intact muscles of the trunk and shoulder girdle to elicit motion in a terminal device attached to the amputation stump. For the first time, an amputee was able to operate his prosthesis with fluid body motions, rather than as a distinct foreign object. In the 1860s, the Comte de Beaufort in France adapted the design for use by wounded soldiers. A shoulder harness with a strap buttoned to the trousers was passed through a loop to the contralateral axilla and missing limb, allowing an amputee to manipulate the strap tension to open and close a double spring hook, or flex and extend the thumb on a simple hand with fused fingers (5,6).
In 1916, German surgeon Dr Ferdinand Sauerbruch described his prosthetic design with digits controlled by transmission of upper arm muscle movements ( ) (7). Video captures from the era show amputees effectively using the prosthesis to drink from a teacup and even to remove a match from a box to light a cigarette (8). Unfortunately, due to the high cost of production, few individuals were able to afford the device.
Open in a separate windowWorld War I (1914 to 1918) resulted in casualties in numbers previously unimagined. In the United States (US), amputee rehabilitation programs were created to help the >4400 amputees, of which the majority (54%) were upper limb (9), to regain some ability to work on farms or in factories. The distribution of prosthetics with sockets and a universal terminal device allowed the attachment of various work tools ( ) (5). In 1917, the Surgeon General of the US Army issued a landmark invitation for limb makers to meet in Washington, DC. The result was the creation of the Association of Limb Manufacturers of America, today the American Orthotic & Prosthetic Association. In Canada, a national charter in 1920 recognized the need to provide support to amputees, leading to the creation of the Amputations Association of The Great War, today known as the War Amps (10).
Open in a separate windowDuring World War II (1939 to 1945), improved shock management and antibiotics saved lives but resulted in 3475 upper limb amputees in the US (9). The huge demand for artificial limbs led to the creation of a US Committee on Prosthetics Research and Development in 1945 and the Canadian Association of Prosthetics and Orthotics in 1955 (11,12). The thalidomide tragedy (1958 to 1962) resulted in the birth of many children with shortened limbs, further driving demand and investment for improved prosthetics (13).
In 1948, the Bowden cable body-powered prosthesis was introduced, replacing bulky straps with a sleek, sturdy cable. Despite new materials and improved craftsmanship, today’s body-powered prostheses are essentially adaptations of the Bowden design ( ). Durable, portable and relatively affordable, body-powered prostheses allow the user an impressive range of motion, speed and force in operating a terminal device – most commonly a two-pronged hook – by changing the tension in a cable via preserved shoulder and body movements. The ability to use both hands simultaneously, rather than requiring a healthy hand to control the prosthesis, permits the user to complete tasks more efficiently. Furthermore, by sensing cable tension, the amputee is able to predict and adjust the position of the prosthesis without visual feedback. Although prolonged wearing can be uncomfortable, complicated motor tasks are limited and appearance is not human-like, body-powered prostheses are widely used (14).
Open in a separate windowA major advancement in intuitive artificial limb control is via the technique of targeted motor reinnervation (TMR), first described in 2004 by Dr Todd Kuiken and Dr Gregory Dumanian in the US (29). By rerouting the cut (ie, amputated) peripheral nerves from an amputated limb to intact spare (target) muscles, the resultant EMG signals of the target muscles now represent motor input to the missing limb muscles ( ) (30). For example, if the median nerve is transferred into the middle pectoralis major muscle belly, then when the amputee thinks ‘flex digits’, the middle region of the pectoralis major will contract, generating a robust EMG to close a prosthetic hand. Unlike body-powered and conventional myoelectric prostheses, TMR is intuitive and enables patients to simultaneously move multiple joints, such as opening and closing the prosthesis while flexing and extending the elbow, increasing the speed of task performance by two- to sixfold (21,31).
Open in a separate windowIn addition to improved motor control, early TMR patients were found to have sensory recovery in the skin overlying the reinnervated muscle. When reinnervated skin was stimulated, sensation was perceived in the body region the amputated nerve used to innervate; that is, the amputee felt touch on a particular part of the missing limb ( ) (32). With this knowledge, the targeted reinnervation technique was extended to include reattaching sensory nerves to the main peripheral nerve trunks (30). A variation of this surgical method to identify, separate and redirect individual sensory nerve fibres from the median and ulnar nerves to target cutaneous sensory areas distant from the reinnervated muscle is being developed by a multidisciplinary team at the University of Alberta (Edmonton, Alberta). This technique, known as fascicular targeted sensory reinnervation, creates a discrete spatial sensory hand map over a selected area of receptor skin away from the prosthesis interface. By incorporating a sensory feedback device, the patient is able to feel and, thus, coordinate the strength of force applied by the myoelectric prosthesis when handling an object. Early results show effective recovery of discriminative pressure sensation (up to four discrete levels of force with 75% to 85% accuracy), the ability to grip and release objects, and the ability to discriminate between size (mean [± SD] 93±6% accuracy) and density (100% accuracy) without visual or auditory stimuli (33).
Open in a separate windowReported complications of the targeted reinnervation procedure include cellulitis, seroma and transiently increased phantom limb pain. The cost of the surgical procedure, hospitalization, prosthesis and rehabilitation ranges from USD$150,000 to $250,000 (34). Although early in its development, as of 2011, targeted reinnervation has been performed on >40 patients worldwide (21).
One of the most intriguing developments in hand ‘prostheses’ is vascularized composite allotransplantation (VCA), which involves the transfer of multiple tissue types (skin, muscle, nerve, vessels and bone) as a functional unit ( ).
Open in a separate windowThe first attempt at hand transplantation was performed in Ecuador in 1964 by Dr Robert Gilbert. Unfortunately, after three weeks, the hand was amputated due to acute organ rejection (35,36). In 1998, the world’s first successful hand transplantation was performed in Lyon, France by an international team led by Dr Jean-Michel Dubernard (37). The 48-year-old patient received the right hand of a 41-year-old brain-dead donor in a 13 h procedure (38,39). Despite technical success and rehabilitative progress, poor medication compliance led to graft rejection, and the hand was removed after a total of 29 months (40). A subsequent transplantation, performed in Louisville (Kentucky, USA) in 1999 on 37-year-old Matthew Scott, had greater postoperative success. Scott, now 50 years of age, is the longest surviving hand transplant recipient in the world (38). In 2000, the world’s first bilateral hand transplantation was performed in Lyon, France on a 33-year-old man who lost both of his hands in a blast injury (41).
For motivated and compliant patients, the International Federation of Societies for Surgery of the Hand declared that:
…a remarkably good recovery of sensibility has been documented in all transplanted hands…protective sensation was achieved in all patients within 6 to 12 months…90% showed tactile and 72% of the discriminative sensibility, thus providing a true benefit over prosthetic wear
39 ).
Within one year, patients are able to turn doorknobs, pick up objects, hold utensils, catch balls and tie shoes (42). Hand transplantation also restores the normal appearance of a human limb, with an immeasurable psychological benefit (34). Improvement in quality of life has been stated by 75% of hand transplant recipients, with many returning to work ( ) (43).
Open in a separate windowDespite these successes, hand transplantation is a topic of intense controversy due to associated complications, ethical concerns and unique patient considerations. Immunosuppression is crucial because each tissue in a composite allograft differs in its antigenicity and may be rejected by unique humoral or cellular mechanisms. Typical protocols include prednisone, tacrolimus and mycophenolate mofetil, with complications including opportunistic infections, skin cancer, sepsis and renal failure (43). The long-term effects are unknown, but chronic organ rejection has yet to be observed. Unlike solid organ transplantation, however, the goal of hand transplantation is not to save a life, but to improve the quality of life. With this in mind, critics question the ethics of subjecting a patient to the consequences of life-long immunosuppression when other options for hand replacement are widely available. Others emphasize that not all transplant patients achieve satisfactory tactile control, grip strength or thermoregulation (44). Psychological prescreening for highly motivated patients is crucial because the patient’s commitment to rigorous rehabilitation and immunosuppression is of paramount importance to the overall success of the procedure.
Currently, 30 single hand and 21 double hand transplantations have been performed worldwide (45). Although the costs are estimated to be >$500,000 (46), hand transplantation is the most frequently performed VCA procedure. In 2010, the Mayo Clinic in Rochester (Minnesota, USA) created the first nonexperimental hand transplantation program in North America (47). No hand transplantations have been performed yet in Canada, but work is underway to develop a VCA program in Ontario. The University of Toronto (Toronto, Ontario) has submitted a proposal for upper extremity transplantation to the Ministry of Health for approval. Progress in immunoregulatory protocols with decreased toxicity is a major step toward increasing acceptance for hand transplantation.
The act of replacing a missing hand to restore both function and form has challenged humans for millennia. While materials and designs have evolved greatly, we have yet to build or create a totally satisfactory substitute for the 41,000 individuals in the US with major upper limb amputations (48).
The future of hand replacement is exciting. There is no doubt that current technology – body-powered prostheses, myoelectric prostheses, targeted reinnervation and hand transplantation – will be improved on and become more accessible. With cutting-edge advancements in regenerative medicine and tissue engineering, however, prostheses could one day become obsolete. The idea of a ‘petri dish hand’ is particularly intriguing; the ability to create a phenotypically identical hand to replace a severed one could provide optimal integration in terms of biological compatibility, functional control, social communication, sensory feedback and, of course, aesthetics.
The authors thank Dr Dawna M Gilchrist, Director of the History of Medicine Program, University of Alberta, and Dr Jacqueline S Hebert, Associate Research Chair in Clinical Rehabilitation, University of Alberta, for their generous support and guidance in the preparation of this work.
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