Prosthetic Medicine: Past, Present and Future

What links a famous Roman General, drummer of band Def Leppard and an ex-wife of a member of the Beatles? This rather unusual trio have all experienced amputations (either accidental or by design) and have benefitted significantly from prosthetic limbs. Although emerging evidence garnered from mummified Ancient Egyptians and archaic Latin texts suggests that prosthetic limbs have been in use for nearly 3000 years, it is only in the past two centuries that significant advances have been made in this field. The story of their evolution – and significant enhancement since the wars in Afghanistan and Iraq – bears important lessons not just for medicine, but for human life on this planet. 

Each year in the UK, more than 5000 significant limb amputations are performed, usually due to critical loss of blood flow to the affected limb. This invasive and life-changing surgery often has a profound effect upon a patient’s quality of life, independence, and, in many cases, their mobility. It is unsurprising therefore, that 20-30% amputees suffer from marked depression in the years after surgery. Prosthetic limbs can (at least to some extent) help to restore a patient’s autonomy and the greater physical activity which they afford their users can significantly improve both health and life-span. The remarkable utility of modern biomechanical limbs – often sufficient to allow their users to lead very normal lives – is a thoroughly modern innovation. In centuries long past, many prostheses were profoundly limited in the practical sense. 

The oldest documented prosthesis is thought to date from 950-710 BC. Unearthed in Cairo in 2000, this prosthetic toe was found attached to the foot of Tabakentenmut, the mummified daughter of an Ancient Egyptian priest. Remarkably, a primitive hinge joint – thought to mimic that between the big toe and the foot – was present to allow some movement. Centuries later, another great civilization – the Romans – also utilised prosthetic limbs. The historian Pliny tells the story of the celebrated general Marcus Sergius, a leader in the Second Punic War. This steadfast soldier sustained no less than 23 injuries in a single campaign and twice escaped from the enemy following capture. A bespoke iron hand was constructed for Marcus Sergius so that he could continue to carry a shield whilst leading his troops into battle. 

The world’s most famous antiquated prosthesis is without doubt the pirate “pegleg”. Immortalised in fiction (worn by the illustrious Captain Ahab, Mad-Eye Moody and Long John Silver), the pegleg was actually a cheap alternative to more cumbersome life-like legs in the 18th and 19th centuries. However, its popularity waned as amputees switched to more comfortable and mobile lower-leg prostheses in the mid-19th century. 

In fact, little changed in the design and practicality of the prosthetic limb between the Roman era and the industrial revolution. The mid-19th century constitutes a key turning point in this story as it was during this period that general anaesthetics were first applied in surgical procedures. This produced a significant improvement in post-operative outcome besides giving surgeons more time to provide better quality amputations – two factors which conspired to increase demand for well-made and functional prosthetic limbs. With high demand comes innovation, and over the next hundred years, several prostheses with a wide range of movements under fine control were developed. 

Ultimately, however, the great breakthroughs in prosthetic medicine have come about in the past sixty years. This coincides not only with the development of novel materials such as plastics and carbon fibre, but also with the great wars of our time. Major advances in battlefield medicine during the past decade have meant that soldiers gravely injured in Iraq and Afghanistan now stand an excellent chance of survival. After surgery, the reality hits these young men and women: they must adjust to everyday life following the loss of one or more limbs. An industry dedicated to the production of comfortable, functional and durable prostheses has sprung up to meet this demand. 

Modern “myoelectric” prostheses (such as the i-LIMB hand) provide a fine range of highly controlled movements, and perhaps constitute the most elegant human-machine interface in modern medicine. Electrodes placed upon the muscles at the site of amputation detect small electrical pulses (driven by the conscious will of the user to move these muscles) which are translated into a rich repertoire of meaningful movements. A similarly elegant technique, targeted muscle innervation (TMR), is employed in child amputees, and relies on the same detection and interpretation of these small “muscle signals”. TMR depends upon the intrinsic plasticity of the developing brain and involves the re-routing of nerves which would normally serve the amputated limb to other areas of the body. Following surgery, the young patient gradually learns how to control the activity of their prosthesis through small, conscious movements of the newly innervated muscle. Unsurprisingly, habituation to this new movement “control system” during childhood produces outstanding functional outcomes in these patients. 

With prosthetic technology improving by the day, a rather ugly prospect is beginning to rear its head. Bionic limbs will soon far outstrip their human templates in terms of durability and functionality, a fact which may encourage individuals to engineer an “upgrade”. Could aspiring musicians, surgeons and artists amputate their own hands in order to receive an artificial, but improved equivalent? Whilst this dystopian vision may sound far-fetched, one must remember that just five years ago, an inquiry was launched by the International Association of Athletics Federations to examine the “competitive advantage” conferred upon Oscar Pistorius by his prosthetic “blades”. A future of “constructed” humans may not be as remote as we envisage. 

Modern artificial limbs have allowed their bearers to perform feats thought previously unattainable, from competing in able-bodied Olympic Games to trekking to the South Pole. Nonetheless, further innovation remains a priority as comfort and functionality are basic problems in prostheses widely available on the National Health Service. Furthermore, the persistent, poorly-understood and virtually untreatable problem of phantom limb pain – believed to affect up to 80% of amputees – presents a serious hurdle which requires further investigation alongside efforts to develop superior prostheses. 

Prosthetic medicine is now about more than transforming shattered lives and restoring autonomy to patients who have undergone limb amputations; it lies at the forefront of transhumanism, a growing field with a seemingly inexorable goal of improving the human condition ad infinitum. Whilst these advances may help to address the stigma associated with amputations and prosthetic limbs, we must take measures to ensure that the application of new biotechnology does not compromise the human side of patient care. After all, prosthetic medicine is not just “peglegs” and “blades”; it is the common understanding between the doctor and his patient of the loss of a treasured and intimate part of one’s self.