Depending on the extent of the aorta repaired, an open aortic operation may be called an Infrarenal aortic repair, a Thoracic aortic repair, or a Thoracoabdominal aortic repair. A thoracoabdominal aortic repair is a more extensive operation than either an isolated infrarenal or thoracic aortic repair.
OAS is distinct from aortic valve repair and aortic valve replacement, as OAS describes surgery of the aorta, rather than of the heart valves. When the aortic valve is diseased in addition to the ascending aorta, the Bentall procedure is used to treat the entire aortic root. An axillary-bifemoral bypass is another type of vascular bypass
used to treat aortic pathology, however it is not true open aortic
surgery as it reconstructs the flow of blood to the legs from the arm,
rather than in the native location of the aorta.
Medical uses
Open aortic surgery (OAS) is used to treat patients with aortic aneurysms greater than 5.5 cm in diameter, to treat aortic rupture of an aneurysm any size, to treat aortic dissections, and to treat acute aortic syndrome.
It is used to treat infrarenal aneurysms, as well as juxta- and
pararenal aneurysm, thoracic and thoracoabdominal aneurysms, and also
non-aneurysmal aortic pathology. Disease of the aorta proximal to the
left subclavian artery in the chest lies within the specialty of cardiac
surgery, and is treated via procedures such as the valve-sparing aortic root replacement.
Prior to the advent of endovascular aneurysm repair
(EVAR), OAS was the only surgical treatment available for aortic
aneurysms. It is still preferred at some institutions and by some
patients as it may be more durable than EVAR, and does not require post-operative surveillance CT scans.
OAS is sometimes required for patients who have previously
undergone EVAR but need further treatment, such as for degeneration of
the EVAR seal zones leading to continued aneurysm growth. OAS is also
sometimes required in cases of EVAR graft infection where the stent
graft is removed to treat the infection.
Open repair versus endovascular repair
The shift away from open aortic surgery towards endovascular surgery since 2003 has been driven by worse perioperative mortality associated with OAS, particularly in patients in relatively frail health.
Unlike endovascular repair, there are no strict anatomic
contra-indications to open repair; Rather, open repair is viewed as the
fall back option for patients with unfavorable anatomy for endovascular
repair.
The main drawback of open repair is the larger physiologic demand of
the operation, which is associated with increased rates of short term
mortality in most studies.
Patients younger than 50 years with descending and
thoracoabdominal aortic aneurysm have low surgical risks, and open
repairs can be performed with excellent short-term and durable long-term
results. Open surgical repairs should be considered initially in
younger patients requiring descending and thoracoabdominal aortic
aneurysm repairs. Heritable thoracic aortic disease (HTAD) warrants
closer postoperative surveillance.
Technique
Simulated
open aortic surgery for an infrarenal aortic aneurysm. The clamp seen
is above the aneurysm and below the renal arteriesSimulated clamp placement for open repair of an infrarenal aortic aneurysmSimulated proximal suture line using "parachute" technique for an open infrarenal aortic aneurysm repairCompleted proximal suture line of a simulated infrarenal open aortic repair with a dacron bifurcated graft
Open surgery typically involves exposure of the dilated portion of the aorta and insertion of a synthetic (Dacron or Gore-Tex)
graft (tube). Once the graft is sewn into the proximal (toward the
patient's head) and distal (toward the patient's foot) portions of the
aorta, the aneurysmal sac is closed around the graft.
Alternatively, the anastomosis can be carried out with expandable devices, a simpler and quicker procedure
The aorta and its branching arteries are cross-clamped during
open surgery. This can lead to inadequate blood supply to the spinal
cord, resulting in paraplegia,
when repairing thoracic aneurysms. A 2004 systematic review and meta
analysis found that cerebrospinal fluid drainage (CFSD), when performed
in experienced centers, reduces the risk of ischemic spinal cord injury
by increasing the perfusion pressure to the spinal cord.
A 2012 Cochrane systematic review noted that further research regarding
the effectiveness of CFSD for preventing a spinal cord injury is
required.
Approach
The infrarenal aorta can be approached via a transabdominal midline or paramedian incision, or via a retroperitoneal approach.
The paravisceral and thoracic aorta are approached via a
left-sided posteriolateral thoracotomy incision in approximately the 9th
intercostal space.
For a thoracoabdominal aortic aneurysm, this approach can be extended
to a median or paramedian abdominal incision to allow access to the
iliac arteries.
Sequential aortic clamping
At
medical centers with a high volume of open aortic surgery, the fastest
option for open aortic surgery was sequential aortic clamping or
"clamp-and-sew", whereby the aorta was clamped proximally and distally to the diseased segment, and a graft sewn into the intervening segment.
This technique leaves the branches of the aorta un-perfused during the
time it takes to sew in the graft, potentially increasing the risk of ischemia
to the organs which derive their arterial supply from the clamped
segment. Critics of this technique advocate intra-operative aortic
perfusion.
In infrarenal aneurysms, the relative tolerance of the lower
extremities to ischemia allows surgeons to clamp distally with low risk
of ill effect.
Techniques to limit ischemia
A
number of techniques exist for maintaining perfusion to the viscera and
spinal cord during open thoracoabdominal aortic aneurysm repair,
including left heart bypass, balloon perfusion catheter placement in the
visceral arteries, selective spinal drainage and cold crystalloid renal
perfusion. There is limited evidence supporting these techniques.
Graft configuration
The
abdominal aorta is anastomosed preferentially to the main limb of a
tube or bifurcated graft in an end-to-end fashion to minimize turbulent
flow at the proximal anastomosis. If normal aorta exists superior to the
iliac bifurcation, a tube graft can be sewn distally to that normal
aorta. If the distal aorta is diseased, a bifurcated graft can be used
in an aorto-billiac or aorto-bifemoral configuration. If visceral
vessels are involved in the diseased aortic segment, a branched graft
can be used with branches sewn directly to visceral vessels, or the
visceral vessels can be separately revascularized.
OAS
is widely recognized as having higher rates of perioperative morbidity
and mortality than endovascular procedures for comparable segments of
the aorta. For example, in infrarenal aneurysms, perioperative mortality
with endovascular surgery is approximately 0.5%, against 3% with open
repair.
Besides the risk of death, other risks and complications with OAS
depend on the segment of aorta involved, and may include renal failure,
spinal cord ischemia leading to paralysis, buttock claudication,
ischemic colitis, embolization leading to acute limb ischemia,
infection, and bleeding. Development of spinal cord injury is associated with increased
perioperative mortality after the complex aortic repair.
Recovery after OAS
Recovery
time after OAS is substantial. Immediately following surgery, patients
can expect to spend 1–3 days in the intensive care unit, followed by
4–10 days on the hospital ward. After discharge, patients will take 3–6
months to fully recover their energy and return to their pre-operative
daily activities. However, enhanced recovery after surgery (ERAS) protocols can improve recovery following surgery.
TAAA repair requires a very large incision that cuts through
muscles and bones making recovery very difficult and painful for the
patient. Intraoperative intercostal nerve cryoanalgesia has been used
during procedure to help reduce pain after TAAA.
History
The
history of aortic surgery dates back to Greek surgeon Antyllus, who
first performed surgeries for various aneurysms in the second century
AD. Many advancements of OAS have been developed in the past century.
In 1955, cardiovascular surgeons, Drs. Michael DeBakey and Denton Cooley
performed the first replacement of a thoracic aneurysm with a
homograft. In 1958, they began using the Dacron graft, resulting in a
revolution for surgeons in the surgical repair of aortic aneurysms. DeBakey was first to perform cardiopulmonary bypass to repair the ascending aorta, using antegrade perfusion of the brachiocephalic artery.
By the mid-1960s, at Baylor College of Medicine,
DeBakey’s group began performing surgery on thoracoabdominal aortic
aneurysms (TAAA), which presented formidable surgical challenges, often
fraught with serious complications, such as paraplegia, paraparesis and
renal failure. DeBakey protégé and vascular Surgeon, E. Stanley
Crawford, in particular, began dedicating most of his time to TAAAs. In
1986, he classified TAAA open surgery cases into four types:
Extent I, extending from the left subclavian artery to just below the
renal artery; Extent II, from the left subclavian to below the renal
artery; Extent III, from the sixth intercostal space to below the renal
artery; and Extent IV, from the twelfth intercostal space to the iliac
bifurcation (i.e. total abdominal).
In 1992, another classification, Extent V, characterized by Hazim J. Safi,
MD, identified aneurysmal disease extending from the sixth intercostal
space to above the renal arteries. Safi's group used experimental
animal models for a prospective study on the use distal aortic
perfusion, cerebrospinal fluid drainage, moderate hypothermia and
sequential clamping to decrease in the incidence of neurological
deficit. In 1994, they presented their experiences, showing that the
incidence for Extent I and II dropped from 25% to 5%. This marked a new era for protecting the spinal cord, brain, kidneys, heart and lungs during OAS on TAAA.
Progress and future challenges
Postoperative
paraplegia and paraparesis have been the scourge of thoracoabdominal
aortic repair since the inception of the procedure.
However, with evolving surgical strategies, identification of
predictors, and use of various adjuncts over the years, the incidence of
spinal cord injury after thoracic/thoracoabdominal aortic repair has
declined. Embracing a multimodality approach offers a good insight into
combating this grave complication.
In medicine, a prosthesis (PL: prostheses; from Ancient Greek: πρόσθεσις, romanized: prósthesis, lit. 'addition, application, attachment'), or a prosthetic implant,
is an artificial device that replaces a missing body part, which may be
lost through trauma, disease, or a condition present at birth (congenital disorder). Prostheses are intended to restore the normal functions of the missing body part. Amputee rehabilitation is primarily coordinated by a physiatrist
as part of an inter-disciplinary team consisting of physiatrists,
prosthetists, nurses, physical therapists, and occupational therapists. Prostheses can be created by hand or with computer-aided design (CAD), a software interface that helps creators design and analyze the creation with computer-generated 2-D and 3-D graphics as well as analysis and optimization tools.
Types
A person's
prosthesis should be designed and assembled according to the person's
appearance and functional needs. For instance, a person may need a
transradial prosthesis, but the person needs to choose between an
aesthetic functional device, a myoelectric device, a body-powered
device, or an activity specific device. The person's future goals and
economical capabilities may help them choose between one or more
devices.
Limb prostheses include both upper- and lower-extremity prostheses.
Upper-extremity prostheses are used at varying levels of
amputation: forequarter, shoulder disarticulation, transhumeral
prosthesis, elbow disarticulation, transradial prosthesis, wrist
disarticulation, full hand, partial hand, finger, partial finger. A
transradial prosthesis is an artificial limb that replaces an arm
missing below the elbow.
Upper limb prostheses can be categorized in three main
categories: Passive devices, Body Powered devices, and Externally
Powered (myoelectric) devices. Passive devices can either be passive
hands, mainly used for cosmetic purposes, or passive tools, mainly used
for specific activities (e.g. leisure or vocational). An extensive
overview and classification of passive devices can be found in a
literature review by Maat et.al.
A passive device can be static, meaning the device has no movable
parts, or it can be adjustable, meaning its configuration can be
adjusted (e.g. adjustable hand opening). Despite the absence of active
grasping, passive devices are very useful in bimanual tasks that require
fixation or support of an object, or for gesticulation in social
interaction. According to scientific data a third of the upper limb
amputees worldwide use a passive prosthetic hand.
Body Powered or cable-operated limbs work by attaching a harness and
cable around the opposite shoulder of the damaged arm. A recent
body-powered approach has explored the utilization of the user's
breathing to power and control the prosthetic hand to help eliminate
actuation cable and harness. The third category of prosthetic devices available is myoelectric arms. These work by sensing, via electrodes, when the muscles in the upper arm
move, causing an artificial hand to open or close. In the prosthetics
industry, a trans-radial prosthetic arm is often referred to as a "BE"
or below elbow prosthesis.
Lower-extremity prostheses provide replacements at varying
levels of amputation. These include hip disarticulation, transfemoral
prosthesis, knee disarticulation, transtibial prosthesis, Syme's
amputation, foot, partial foot, and toe. The two main subcategories of
lower extremity prosthetic devices are trans-tibial (any amputation
transecting the tibia bone or a congenital anomaly resulting in a tibial
deficiency) and trans-femoral (any amputation transecting the femur
bone or a congenital anomaly resulting in a femoral deficiency).
A transfemoral prosthesis is an artificial limb that replaces a
leg missing above the knee. Transfemoral amputees can have a very
difficult time regaining normal movement. In general, a transfemoral
amputee must use approximately 80% more energy to walk than a person
with two whole legs.
This is due to the complexities in movement associated with the knee.
In newer and more improved designs, hydraulics, carbon fiber, mechanical
linkages, motors, computer microprocessors, and innovative combinations
of these technologies are employed to give more control to the user. In
the prosthetics industry, a trans-femoral prosthetic leg is often
referred to as an "AK" or above the knee prosthesis.
A transtibial prosthesis is an artificial limb that replaces a
leg missing below the knee. A transtibial amputee is usually able to
regain normal movement more readily than someone with a transfemoral
amputation, due in large part to retaining the knee, which allows for
easier movement. Lower extremity prosthetics describe artificially
replaced limbs located at the hip level or lower. In the prosthetics
industry, a trans-tibial prosthetic leg is often referred to as a "BK"
or below the knee prosthesis.
Prostheses are manufactured and fit by clinical Prosthetists.
Prosthetists are healthcare professionals responsible for making,
fitting, and adjusting prostheses and for lower limb prostheses will
assess both gait and prosthetic alignment. Once a prosthesis has been
fit and adjusted by a Prosthetist, a rehabilitation Physiotherapist
(called Physical Therapist in America) will help teach a new prosthetic
user to walk with a leg prosthesis. To do so, the physical therapist may
provide verbal instructions and may also help guide the person using
touch or tactile cues. This may be done in a clinic or home. There is
some research suggesting that such training in the home may be more
successful if the treatment includes the use of a treadmill.
Using a treadmill, along with the physical therapy treatment, helps the
person to experience many of the challenges of walking with a
prosthesis.
In the United Kingdom, 75% of lower limb amputations are performed due to inadequate circulation (dysvascularity). This condition is often associated with many other medical conditions (co-morbidities) including diabetes and heart disease that may make it a challenge to recover and use a prosthetic limb to regain mobility and independence.
For people who have inadequate circulation and have lost a lower limb,
there is insufficient evidence due to a lack of research, to inform them
regarding their choice of prosthetic rehabilitation approaches.
Types of prosthesis used for replacing joints in the human body
Lower extremity prostheses are often categorized by the level of amputation or after the name of a surgeon:
Transfemoral (Above-knee)
Transtibial (Below-knee)
Ankle disarticulation (more commonly known as Syme's amputation)
Knee disarticulation
Hip disarticulation
Hemi-pelvictomy
Partial foot amputations (Pirogoff, Talo-Navicular and
Calcaneo-cuboid (Chopart), Tarso-metatarsal (Lisfranc),
Trans-metatarsal, Metatarsal-phalangeal, Ray amputations, toe
amputations).
Van Nes rotationplasty
Prosthetic raw materials
Prosthetic are made lightweight for better convenience for the amputee. Some of these materials include:
Plastics:
Polyethylene
Polypropylene
Acrylics
Polyurethane
Wood (early prosthetics)
Rubber (early prosthetics)
Lightweight metals:
Titanium
Aluminum
Composites:
Carbon fiber reinforced polymers
Wheeled prostheses have also been used extensively in the
rehabilitation of injured domestic animals, including dogs, cats, pigs,
rabbits, and turtles.
History
Prosthetic toe from ancient Egypt
Prosthetics originate from the ancient Near East circa 3000 BCE, with the earliest evidence of prosthetics appearing in ancient Egypt and Iran. The earliest recorded mention of eye prosthetics is from the Egyptian story of the Eye of Horus dates circa 3000 BC, which involves the left eye of Horus being plucked out and then restored by Thoth.
Circa 3000-2800 BC, the earliest archaeological evidence of prosthetics
is found in ancient Iran, where an eye prosthetic is found buried with a
woman in Shahr-i Shōkhta. It was likely made of bitumen paste that was covered with a thin layer of gold. The Egyptians were also early pioneers of foot prosthetics, as shown by the wooden toe found on a body from the New Kingdom circa 1000 BC. Another early textual mention is found in South Asia circa 1200 BC, involving the warrior queen Vishpala in the Rigveda. Roman bronze crowns have also been found, but their use could have been more aesthetic than medical.
An early mention of a prosthetic comes from the Greek historian Herodotus, who tells the story of Hegesistratus, a Greek diviner who cut off his own foot to escape his Spartan captors and replaced it with a wooden one.
Wood and metal prosthetics
The Capua leg (replica)Iron prosthetic hand believed to have been owned by Götz von Berlichingen (1480–1562)"Illustration of mechanical hand", c. 1564Artificial iron hand believed to date from 1560 to 1600
Pliny the Elder also recorded the tale of a Roman general, Marcus Sergius, whose right hand was cut off while campaigning and had an iron hand made to hold his shield so that he could return to battle. A famous and quite refined historical prosthetic arm was that of Götz von Berlichingen,
made at the beginning of the 16th century. The first confirmed use of a
prosthetic device, however, is from 950 to 710 BC. In 2000, research
pathologists discovered a mummy from this period buried in the Egyptian
necropolis near ancient Thebes that possessed an artificial big toe.
This toe, consisting of wood and leather, exhibited evidence of use.
When reproduced by bio-mechanical engineers in 2011, researchers
discovered that this ancient prosthetic enabled its wearer to walk both
barefoot and in Egyptian style sandals. Previously, the earliest
discovered prosthetic was an artificial leg from Capua.
Around the same time, François de la Noue is also reported to have had an iron hand, as is, in the 17th century, René-Robert Cavalier de la Salle. Henri de Tonti
had a prosthetic hook for a hand. During the Middle Ages, prosthetic
remained quite basic in form. Debilitated knights would be fitted with
prosthetics so they could hold up a shield, grasp a lance or a sword, or
stabilize a mounted warrior. Only the wealthy could afford anything that would assist in daily life.
One notable prosthesis was that belonging to an Italian man, who
scientists estimate replaced his amputated right hand with a knife. Scientists investigating the skeleton, which was found in a Longobard cemetery in Povegliano Veronese, estimated that the man had lived sometime between the 6th and 8th centuries AD.
Materials found near the man's body suggest that the knife prosthesis
was attached with a leather strap, which he repeatedly tightened with
his teeth.
During the Renaissance, prosthetics developed with the use of
iron, steel, copper, and wood. Functional prosthetics began to make an
appearance in the 1500s.
Technology progress before the 20th century
An
Italian surgeon recorded the existence of an amputee who had an arm
that allowed him to remove his hat, open his purse, and sign his name. Improvement in amputation surgery and prosthetic design came at the hands of Ambroise Paré. Among his inventions was an above-knee device that was a kneeling peg leg
and foot prosthesis with a fixed position, adjustable harness, and knee
lock control. The functionality of his advancements showed how future
prosthetics could develop.
Other major improvements before the modern era:
Pieter Verduyn – First non-locking below-knee (BK) prosthesis.
James Potts –
Prosthesis made of a wooden shank and socket, a steel knee joint and an
articulated foot that was controlled by catgut tendons from the knee to
the ankle. Came to be known as "Anglesey Leg" or "Selpho Leg".
Sir James Syme – A new method of ankle amputation that did not involve amputating at the thigh.
Benjamin Palmer – Improved upon the Selpho leg. Added an anterior spring and concealed tendons to simulate natural-looking movement.
Dubois Parmlee – Created prosthetic with a suction socket, polycentric knee, and multi-articulated foot.
Henry Heather Bigg, and his son Henry Robert Heather Bigg, won the
Queen's command to provide "surgical appliances" to wounded soldiers
after Crimea War. They developed arms that allowed a double arm amputee
to crochet, and a hand that felt natural to others based on ivory, felt
and leather.
At the end of World War II, the NAS (National Academy of Sciences)
began to advocate better research and development of prosthetics.
Through government funding, a research and development program was
developed within the Army, Navy, Air Force, and the Veterans
Administration.
Lower extremity modern history
An artificial limbs factory in 1941
After the Second World War a team at the University of California, Berkeley including James Foort
and C.W. Radcliff helped to develop the quadrilateral socket by
developing a jig fitting system for amputations above the knee. Socket
technology for lower extremity limbs saw a further revolution during the
1980s when John Sabolich C.P.O., invented the Contoured Adducted
Trochanteric-Controlled Alignment Method (CATCAM) socket, later to
evolve into the Sabolich Socket. He followed the direction of Ivan Long
and Ossur Christensen as they developed alternatives to the
quadrilateral socket, which in turn followed the open ended plug socket,
created from wood.
The advancement was due to the difference in the socket to patient
contact model. Prior to this, sockets were made in the shape of a square
shape with no specialized containment for muscular tissue. New designs
thus help to lock in the bony anatomy, locking it into place and
distributing the weight evenly over the existing limb as well as the
musculature of the patient. Ischial containment is well known and used
today by many prosthetist to help in patient care. Variations of the
ischial containment socket thus exists and each socket is tailored to
the specific needs of the patient. Others who contributed to socket
development and changes over the years include Tim Staats, Chris Hoyt,
and Frank Gottschalk. Gottschalk disputed the efficacy of the CAT-CAM
socket- insisting the surgical procedure done by the amputation surgeon
was most important to prepare the amputee for good use of a prosthesis
of any type socket design.
The first microprocessor-controlled prosthetic knees became
available in the early 1990s. The Intelligent Prosthesis was the first
commercially available microprocessor-controlled prosthetic knee. It was
released by Chas. A. Blatchford & Sons, Ltd., of Great Britain, in
1993 and made walking with the prosthesis feel and look more natural.
An improved version was released in 1995 by the name Intelligent
Prosthesis Plus. Blatchford released another prosthesis, the Adaptive
Prosthesis, in 1998. The Adaptive Prosthesis utilized hydraulic
controls, pneumatic controls, and a microprocessor to provide the
amputee with a gait that was more responsive to changes in walking
speed. Cost analysis reveals that a sophisticated above-knee prosthesis
will be about $1 million in 45 years, given only annual cost of living
adjustments.
In 2019, a project under AT2030 was launched in which bespoke
sockets are made using a thermoplastic, rather than through a plaster
cast. This is faster to do and significantly less expensive. The sockets
were called Amparo Confidence sockets.
Upper extremity modern history
In 2005, DARPA started the Revolutionizing Prosthetics program.
Patient procedure
A prosthesis is a functional replacement for an amputated or congenitally malformed or missing limb. Prosthetists are responsible for the prescription, design, and management of a prosthetic device.
In most cases, the prosthetist begins by taking a plaster cast of
the patient's affected limb. Lightweight, high-strength thermoplastics
are custom-formed to this model of the patient. Cutting-edge materials
such as carbon fiber, titanium and Kevlar provide strength and
durability while making the new prosthesis lighter. More sophisticated
prostheses are equipped with advanced electronics, providing additional
stability and control.
Over the years, there have been advancements in artificial limbs. New plastics and other materials, such as carbon fiber,
have allowed artificial limbs to be stronger and lighter, limiting the
amount of extra energy necessary to operate the limb. This is especially
important for trans-femoral amputees. Additional materials have allowed
artificial limbs to look much more realistic, which is important to
trans-radial and transhumeral amputees because they are more likely to
have the artificial limb exposed.
Manufacturing a prosthetic finger
In addition to new materials, the use of electronics has become very
common in artificial limbs. Myoelectric limbs, which control the limbs
by converting muscle movements to electrical signals, have become much
more common than cable operated limbs. Myoelectric signals are picked up
by electrodes, the signal gets integrated and once it exceeds a certain
threshold, the prosthetic limb control signal is triggered which is why
inherently, all myoelectric controls lag. Conversely, cable control is
immediate and physical, and through that offers a certain degree of
direct force feedback that myoelectric control does not. Computers are
also used extensively in the manufacturing of limbs. Computer Aided Design and Computer Aided Manufacturing are often used to assist in the design and manufacture of artificial limbs.
Most modern artificial limbs are attached to the residual limb (stump) of the amputee by belts and cuffs or by suction.
The residual limb either directly fits into a socket on the prosthetic,
or—more commonly today—a liner is used that then is fixed to the socket
either by vacuum (suction sockets) or a pin lock. Liners are soft and
by that, they can create a far better suction fit than hard sockets.
Silicone liners can be obtained in standard sizes, mostly with a
circular (round) cross section, but for any other residual limb shape,
custom liners can be made. The socket is custom made to fit the residual
limb and to distribute the forces of the artificial limb across the
area of the residual limb (rather than just one small spot), which helps
reduce wear on the residual limb.
Production of prosthetic socket
The
production of a prosthetic socket begins with capturing the geometry of
the residual limb, this process is called shape capture. The goal of
this process is to create an accurate representation of the residual
limb, which is critical to achieve good socket fit.
The custom socket is created by taking a plaster cast of the residual
limb or, more commonly today, of the liner worn over their residual
limb, and then making a mold from the plaster cast. The commonly used
compound is called Plaster of Paris.
In recent years, various digital shape capture systems have been
developed which can be input directly to a computer allowing for a more
sophisticated design. In general, the shape capturing process begins
with the digital acquisition of three-dimensional (3D) geometric data
from the amputee's residual limb. Data are acquired with either a probe,
laser scanner, structured light scanner, or a photographic-based 3D
scanning system.
After shape capture, the second phase of the socket production is
called rectification, which is the process of modifying the model of
the residual limb by adding volume to bony prominence and potential
pressure points and remove volume from load bearing area. This can be
done manually by adding or removing plaster to the positive model, or
virtually by manipulating the computerized model in the software.
Lastly, the fabrication of the prosthetic socket begins once the model
has been rectified and finalized. The prosthetists would wrap the
positive model with a semi-molten plastic sheet or carbon fiber coated
with epoxy resin to construct the prosthetic socket.
For the computerized model, it can be 3D printed using a various of
material with different flexibility and mechanical strength.
Optimal socket fit between the residual limb and socket is
critical to the function and usage of the entire prosthesis. If the fit
between the residual limb and socket attachment is too loose, this will
reduce the area of contact between the residual limb and socket or
liner, and increase pockets between residual limb skin and socket or
liner. Pressure then is higher, which can be painful. Air pockets can
allow sweat to accumulate that can soften the skin. Ultimately, this is a
frequent cause for itchy skin rashes. Over time, this can lead to
breakdown of the skin.
On the other hand, a very tight fit may excessively increase the
interface pressures that may also lead to skin breakdown after prolonged
use.
Artificial limbs are typically manufactured using the following steps:
Measurement of the residual limb
Measurement of the body to determine the size required for the artificial limb
Fitting of a silicone liner
Creation of a model of the liner worn over the residual limb
Formation of thermoplastic sheet around the model – This is then used to test the fit of the prosthetic
Formation of permanent socket
Formation of plastic parts of the artificial limb – Different methods are used, including vacuum forming and injection molding
Creation of metal parts of the artificial limb using die casting
Assembly of entire limb
Body-powered arms
Current technology allows body-powered arms to weigh around one-half to one-third of what a myoelectric arm does.
Sockets
Current
body-powered arms contain sockets that are built from hard epoxy or
carbon fiber. These sockets or "interfaces" can be made more comfortable
by lining them with a softer, compressible foam material that provides
padding for the bone prominences. A self-suspending or supra-condylar
socket design is useful for those with short to mid-range below elbow
absence. Longer limbs may require the use of a locking roll-on type
inner liner or more complex harnessing to help augment suspension.
Wrists
Wrist
units are either screw-on connectors featuring the UNF 1/2-20 thread
(USA) or quick-release connector, of which there are different models.
Voluntary opening and voluntary closing
Two
types of body-powered systems exist, voluntary opening "pull to open"
and voluntary closing "pull to close". Virtually all "split hook"
prostheses operate with a voluntary opening type system.
More modern "prehensors" called GRIPS utilize voluntary closing
systems. The differences are significant. Users of voluntary opening
systems rely on elastic bands or springs for gripping force, while users
of voluntary closing systems rely on their own body power and energy to
create gripping force.
Voluntary closing users can generate prehension forces equivalent
to the normal hand, up to or exceeding one hundred pounds. Voluntary
closing GRIPS require constant tension to grip, like a human hand, and
in that property, they do come closer to matching human hand
performance. Voluntary opening split hook users are limited to forces
their rubber or springs can generate which usually is below 20 pounds.
Feedback
An
additional difference exists in the biofeedback created that allows the
user to "feel" what is being held. Voluntary opening systems once
engaged provide the holding force so that they operate like a passive
vice at the end of the arm. No gripping feedback is provided once the
hook has closed around the object being held. Voluntary closing systems
provide directly proportional control and biofeedback so that the user can feel how much force that they are applying.
In 1997, the Colombian Prof. Álvaro Ríos Poveda, a researcher in bionics in Latin America, developed an upper limb and hand prosthesis with sensory feedback. This technology allows amputee patients to handle prosthetic hand systems in a more natural way.
A recent study showed that by stimulating the median and ulnar
nerves, according to the information provided by the artificial sensors
from a hand prosthesis, physiologically appropriate (near-natural)
sensory information could be provided to an amputee. This feedback
enabled the participant to effectively modulate the grasping force of
the prosthesis with no visual or auditory feedback.
In February 2013, researchers from École Polytechnique Fédérale de Lausanne in Switzerland and the Scuola Superiore Sant'Anna
in Italy, implanted electrodes into an amputee's arm, which gave the
patient sensory feedback and allowed for real time control of the
prosthetic.
With wires linked to nerves in his upper arm, the Danish patient was
able to handle objects and instantly receive a sense of touch through
the special artificial hand that was created by Silvestro Micera and
researchers both in Switzerland and Italy.
In July 2019, this technology was expanded on even further by researchers from the University of Utah,
led by Jacob George. The group of researchers implanted electrodes into
the patient's arm to map out several sensory precepts. They would then
stimulate each electrode to figure out how each sensory precept was
triggered, then proceed to map the sensory information onto the
prosthetic. This would allow the researchers to get a good approximation
of the same kind of information that the patient would receive from
their natural hand. Unfortunately, the arm is too expensive for the
average user to acquire, however, Jacob mentioned that insurance
companies could cover the costs of the prosthetic.
Terminal devices
Terminal devices contain a range of hooks, prehensors, hands or other devices.
Hooks
Voluntary opening split hook systems are simple, convenient, light, robust, versatile and relatively affordable.
A hook does not match a normal human hand for appearance or
overall versatility, but its material tolerances can exceed and surpass
the normal human hand for mechanical stress (one can even use a hook to
slice open boxes or as a hammer whereas the same is not possible with a
normal hand), for thermal stability (one can use a hook to grip items
from boiling water, to turn meat on a grill, to hold a match until it
has burned down completely) and for chemical hazards (as a metal hook
withstands acids or lye, and does not react to solvents like a
prosthetic glove or human skin).
Hands
Actor Owen Wilson gripping the myoelectric prosthetic arm of a United States Marine
Prosthetic hands are available in both voluntary opening and
voluntary closing versions and because of their more complex mechanics
and cosmetic glove covering require a relatively large activation force,
which, depending on the type of harness used, may be uncomfortable.
A recent study by the Delft University of Technology, The Netherlands,
showed that the development of mechanical prosthetic hands has been
neglected during the past decades. The study showed that the pinch force
level of most current mechanical hands is too low for practical use.
The best tested hand was a prosthetic hand developed around 1945. In
2017 however, a research has been started with bionic hands by Laura Hruby of the Medical University of Vienna. A few open-hardware 3-D printable bionic hands have also become available. Some companies are also producing robotic hands with integrated forearm, for fitting unto a patient's upper arm
and in 2020, at the Italian Institute of Technology (IIT), another
robotic hand with integrated forearm (Soft Hand Pro) was developed.
Commercial providers and materials
Hosmer and Otto Bock
are major commercial hook providers. Mechanical hands are sold by
Hosmer and Otto Bock as well; the Becker Hand is still manufactured by
the Becker family. Prosthetic hands may be fitted with standard stock or
custom-made cosmetic looking silicone gloves. But regular work gloves
may be worn as well. Other terminal devices include the V2P Prehensor, a
versatile robust gripper that allows customers to modify aspects of it,
Texas Assist Devices (with a whole assortment of tools) and TRS that
offers a range of terminal devices for sports. Cable harnesses can be
built using aircraft steel cables, ball hinges, and self-lubricating
cable sheaths. Some prosthetics have been designed specifically for use
in salt water.
Lower-extremity prosthetics describes artificially replaced limbs
located at the hip level or lower. Concerning all ages Ephraim et al.
(2003) found a worldwide estimate of all-cause lower-extremity
amputations of 2.0–5.9 per 10,000 inhabitants. For birth prevalence
rates of congenital limb deficiency they found an estimate between 3.5
and 7.1 cases per 10,000 births.
The two main subcategories of lower extremity prosthetic devices
are trans-tibial (any amputation transecting the tibia bone or a
congenital anomaly resulting in a tibial deficiency), and trans-femoral
(any amputation transecting the femur bone or a congenital anomaly
resulting in a femoral deficiency). In the prosthetic industry, a
trans-tibial prosthetic leg is often referred to as a "BK" or below the
knee prosthesis while the trans-femoral prosthetic leg is often referred
to as an "AK" or above the knee prosthesis.
Other, less prevalent lower extremity cases include the following:
Hip disarticulations – This usually refers to when an amputee or
congenitally challenged patient has either an amputation or anomaly at
or in close proximity to the hip joint.
Knee disarticulations – This usually refers to an amputation through the knee disarticulating the femur from the tibia.
Symes – This is an ankle disarticulation while preserving the heel pad.
Socket
The
socket serves as an interface between the residuum and the prosthesis,
ideally allowing comfortable weight-bearing, movement control and proprioception. Socket problems, such as discomfort and skin breakdown, are rated among the most important issues faced by lower-limb amputees.
Shank and connectors
This
part creates distance and support between the knee-joint and the foot
(in case of an upper-leg prosthesis) or between the socket and the foot.
The type of connectors that are used between the shank and the
knee/foot determines whether the prosthesis is modular or not. Modular
means that the angle and the displacement of the foot in respect to the
socket can be changed after fitting. In developing countries prosthesis
mostly are non-modular, in order to reduce cost. When considering
children modularity of angle and height is important because of their
average growth of 1.9 cm annually.
Foot
Providing contact to the ground, the foot provides shock absorption and stability during stance.
Additionally it influences gait biomechanics by its shape and
stiffness. This is because the trajectory of the center of pressure
(COP) and the angle of the ground reaction forces is determined by the
shape and stiffness of the foot and needs to match the subject's build
in order to produce a normal gait pattern.
Andrysek (2010) found 16 different types of feet, with greatly varying
results concerning durability and biomechanics. The main problem found
in current feet is durability, endurance ranging from 16 to 32 months
These results are for adults and will probably be worse for children
due to higher activity levels and scale effects. Evidence comparing
different types of feet and ankle prosthetic devices is not strong
enough to determine if one mechanism of ankle/foot is superior to
another.
When deciding on a device, the cost of the device, a person's
functional need, and the availability of a particular device should be
considered.
Knee joint
In
case of a trans-femoral (above knee) amputation, there also is a need
for a complex connector providing articulation, allowing flexion during
swing-phase but not during stance. As its purpose is to replace the
knee, the prosthetic knee joint is the most critical component of the
prosthesis for trans-femoral amputees. The function of the good
prosthetic knee joint is to mimic the function of the normal knee, such
as providing structural support and stability during stance phase but
able to flex in a controllable manner during swing phase. Hence it
allows users to have a smooth and energy efficient gait and minimize the
impact of amputation. The prosthetic knee is connected to the prosthetic foot by the shank, which is usually made of an aluminum or graphite tube.
One of the most important aspect of a prosthetic knee joint would
be its stance-phase control mechanism. The function of stance-phase
control is to prevent the leg from buckling when the limb is loaded
during weight acceptance. This ensures the stability of the knee in
order to support the single limb support task of stance phase and
provides a smooth transition to the swing phase. Stance phase control
can be achieved in several ways including the mechanical locks, relative alignment of prosthetic components, weight activated friction control, and polycentric mechanisms.
Microprocessor control
To
mimic the knee's functionality during gait, microprocessor-controlled
knee joints have been developed that control the flexion of the knee.
Some examples are Otto Bock's C-leg, introduced in 1997, Ossur's
Rheo Knee, released in 2005, the Power Knee by Ossur, introduced in
2006, the Plié Knee from Freedom Innovations and DAW Industries' Self
Learning Knee (SLK).
The idea was originally developed by Kelly James, a Canadian engineer, at the University of Alberta.
A microprocessor is used to interpret and analyze signals from
knee-angle sensors and moment sensors. The microprocessor receives
signals from its sensors to determine the type of motion being employed
by the amputee. Most microprocessor controlled knee-joints are powered
by a battery housed inside the prosthesis.
The sensory signals computed by the microprocessor are used to control the resistance generated by hydraulic cylinders in the knee-joint. Small valves control the amount of hydraulic fluid
that can pass into and out of the cylinder, thus regulating the
extension and compression of a piston connected to the upper section of
the knee.
The main advantage of a microprocessor-controlled prosthesis is a
closer approximation to an amputee's natural gait. Some allow amputees
to walk near walking speed or run. Variations in speed are also possible
and are taken into account by sensors and communicated to the
microprocessor, which adjusts to these changes accordingly. It also
enables the amputees to walk downstairs with a step-over-step approach,
rather than the one step at a time approach used with mechanical knees.
There is some research suggesting that people with
microprocessor-controlled prostheses report greater satisfaction and
improvement in functionality, residual limb health, and safety. People may be able to perform everyday activities at greater speeds, even while multitasking, and reduce their risk of falls.
However, some have some significant drawbacks that impair its
use. They can be susceptible to water damage and thus great care must be
taken to ensure that the prosthesis remains dry.
Myoelectric
A myoelectric prosthesis
uses the electrical tension generated every time a muscle contracts, as
information. This tension can be captured from voluntarily contracted
muscles by electrodes applied on the skin to control the movements of
the prosthesis, such as elbow flexion/extension, wrist
supination/pronation (rotation) or opening/closing of the fingers. A
prosthesis of this type utilizes the residual neuromuscular system of
the human body to control the functions of an electric powered
prosthetic hand, wrist, elbow or foot.
This is different from an electric switch prosthesis, which requires
straps and/or cables actuated by body movements to actuate or operate
switches that control the movements of the prosthesis. There is no clear
evidence concluding that myoelectric upper extremity prostheses
function better than body-powered prostheses.
Advantages to using a myoelectric upper extremity prosthesis include
the potential for improvement in cosmetic appeal (this type of
prosthesis may have a more natural look), may be better for light
everyday activities, and may be beneficial for people experiencing phantom limb pain.
When compared to a body-powered prosthesis, a myoelectric prosthesis
may not be as durable, may have a longer training time, may require more
adjustments, may need more maintenance, and does not provide feedback
to the user.
Prof. Alvaro Ríos Poveda
has been working for several years on a non-invasive and affordable
solution to this feedback problem. He considers that: "Prosthetic limbs
that can be controlled with thought hold great promise for the amputee,
but without sensorial feedback from the signals returning to the brain,
it can be difficult to achieve the level of control necessary to perform
precise movements. When connecting the sense of touch from a mechanical
hand directly to the brain, prosthetics can restore the function of the
amputated limb in an almost natural-feeling way." He presented the
first Myoelectric prosthetic hand with sensory feedback at the XVIII World Congress on Medical Physics and Biomedical Engineering, 1997, held in Nice, France.
The USSR was the first to develop a myoelectric arm in 1958, while the first myoelectric arm became commercial in 1964 by the Central Prosthetic Research Institute of the USSR, and distributed by the Hangar Limb Factory of the UK.
Robots can be used to generate objective measures of patient's
impairment and therapy outcome, assist in diagnosis, customize therapies
based on patient's motor abilities, and assure compliance with
treatment regimens and maintain patient's records. It is shown in many
studies that there is a significant improvement in upper limb motor
function after stroke using robotics for upper limb rehabilitation.
In order for a robotic prosthetic limb to work, it must have several components to integrate it into the body's function: Biosensors detect signals from the user's nervous or muscular systems. It then relays this information to a microcontroller
located inside the device, and processes feedback from the limb and
actuator, e.g., position or force, and sends it to the controller.
Examples include surface electrodes that detect electrical activity on
the skin, needle electrodes implanted in muscle, or solid-state
electrode arrays with nerves growing through them. One type of these
biosensors are employed in myoelectric prostheses.
A device known as the controller is connected to the user's nerve
and muscular systems and the device itself. It sends intention commands
from the user to the actuators of the device and interprets feedback
from the mechanical and biosensors to the user. The controller is also
responsible for the monitoring and control of the movements of the
device.
An actuator
mimics the actions of a muscle in producing force and movement.
Examples include a motor that aids or replaces original muscle tissue.
Targeted muscle reinnervation (TMR) is a technique in which motor nerves, which previously controlled muscles on an amputated limb, are surgically rerouted such that they reinnervate a small region of a large, intact muscle, such as the pectoralis major.
As a result, when a patient thinks about moving the thumb of their
missing hand, a small area of muscle on their chest will contract
instead. By placing sensors over the reinnervated muscle, these
contractions can be made to control the movement of an appropriate part
of the robotic prosthesis.
A variant of this technique is called targeted sensory reinnervation (TSR). This procedure is similar to TMR, except that sensory nerves are surgically rerouted to skin
on the chest, rather than motor nerves rerouted to muscle. Recently,
robotic limbs have improved in their ability to take signals from the human brain and translate those signals into motion in the artificial limb. DARPA,
the Pentagon's research division, is working to make even more
advancements in this area. Their desire is to create an artificial limb
that ties directly into the nervous system.
Robotic arms
Advancements
in the processors used in myoelectric arms have allowed developers to
make gains in fine-tuned control of the prosthetic. The Boston Digital Arm
is a recent artificial limb that has taken advantage of these more
advanced processors. The arm allows movement in five axes and allows the
arm to be programmed for a more customized feel. Recently the I-LIMB Hand, invented in Edinburgh, Scotland, by David Gow
has become the first commercially available hand prosthesis with five
individually powered digits. The hand also possesses a manually
rotatable thumb which is operated passively by the user and allows the
hand to grip in precision, power, and key grip modes.
Another neural prosthetic is Johns Hopkins University Applied Physics Laboratory Proto 1. Besides the Proto 1, the university also finished the Proto 2 in 2010.
Early in 2013, Max Ortiz Catalan and Rickard Brånemark of the Chalmers
University of Technology, and Sahlgrenska University Hospital in Sweden,
succeeded in making the first robotic arm which is mind-controlled and
can be permanently attached to the body (using osseointegration).
An approach that is very useful is called arm rotation which is
common for unilateral amputees which is an amputation that affects only
one side of the body; and also essential for bilateral amputees, a
person who is missing or has had amputated either both arms or legs, to
carry out activities of daily living. This involves inserting a small
permanent magnet into the distal end of the residual bone of subjects
with upper limb amputations. When a subject rotates the residual arm,
the magnet will rotate with the residual bone, causing a change in
magnetic field distribution.
EEG (electroencephalogram) signals, detected using small flat metal
discs attached to the scalp, essentially decoding human brain activity
used for physical movement, is used to control the robotic limbs. This
allows the user to control the part directly.
Robotic transtibial prostheses
The research of robotic legs has made some advancement over time, allowing exact movement and control.
Researchers at the Rehabilitation Institute of Chicago
announced in September 2013 that they have developed a robotic leg that
translates neural impulses from the user's thigh muscles into movement,
which is the first prosthetic leg to do so. It is currently in testing.
Hugh Herr, head of the biomechatronics group at MIT's Media Lab developed a robotic transtibial leg (PowerFoot BiOM).
The Icelandic company Össur has also created a robotic
transtibial leg with motorized ankle that moves through algorithms and
sensors that automatically adjust the angle of the foot during different
points in its wearer's stride. Also there are brain-controlled bionic
legs that allow an individual to move his limbs with a wireless
transmitter.
Prosthesis design
The
main goal of a robotic prosthesis is to provide active actuation during
gait to improve the biomechanics of gait, including, among other
things, stability, symmetry, or energy expenditure for amputees.
There are several powered prosthetic legs currently on the market,
including fully powered legs, in which actuators directly drive the
joints, and semi-active legs, which use small amounts of energy and a
small actuator to change the mechanical properties of the leg but do not
inject net positive energy into gait. Specific examples include The
emPOWER from BionX, the Proprio Foot from Ossur, and the Elan Foot from
Endolite. Various research groups have also experimented with robotic legs over the last decade.
Central issues being researched include designing the behavior of the
device during stance and swing phases, recognizing the current
ambulation task, and various mechanical design problems such as
robustness, weight, battery-life/efficiency, and noise-level. However,
scientists from Stanford University and Seoul National University has developed artificial nerves system that will help prosthetic limbs feel. This synthetic nerve system enables prosthetic limbs sense braille, feel the sense of touch and respond to the environment.
Use of recycled materials
Prosthetics are being made from recycled plastic bottles and lids around the world.
Attachment to the body
Most
prostheses can be attached to the exterior of the body, in a
non-permanent way. Some others however can be attached in a permanent
way. One such example are exoprostheses (see below).
Osseointegration is a method of attaching the artificial limb to the body. This method is also sometimes referred to as exoprosthesis (attaching an artificial limb to the bone), or endo-exoprosthesis.
The stump and socket method can cause significant pain in the
amputee, which is why the direct bone attachment has been explored
extensively. The method works by inserting a titanium bolt into the bone
at the end of the stump. After several months the bone attaches itself
to the titanium bolt and an abutment is attached to the titanium bolt.
The abutment extends out of the stump and the (removable) artificial
limb is then attached to the abutment. Some of the benefits of this
method include the following:
Better muscle control of the prosthetic.
The ability to wear the prosthetic for an extended period of time; with the stump and socket method this is not possible.
The ability for transfemoral amputees to drive a car.
The main disadvantage of this method is that amputees with the direct
bone attachment cannot have large impacts on the limb, such as those
experienced during jogging, because of the potential for the bone to
break.
Cosmesis
Cosmetic prosthesis has long been used to disguise injuries and disfigurements. With advances in modern technology, cosmesis, the creation of lifelike limbs made from silicone or PVC, has been made possible.
Such prosthetics, including artificial hands, can now be designed to
simulate the appearance of real hands, complete with freckles, veins,
hair, fingerprints and even tattoos.
Custom-made cosmeses are generally more expensive (costing thousands of
U.S. dollars, depending on the level of detail), while standard cosmeses
come premade in a variety of sizes, although they are often not as
realistic as their custom-made counterparts. Another option is the
custom-made silicone cover, which can be made to match a person's skin
tone but not details such as freckles or wrinkles. Cosmeses are attached
to the body in any number of ways, using an adhesive, suction,
form-fitting, stretchable skin, or a skin sleeve.
Unlike neuromotor prostheses, neurocognitive prostheses would sense
or modulate neural function in order to physically reconstitute or
augment cognitive processes such as executive function, attention,
language, and memory. No neurocognitive prostheses are currently
available but the development of implantable neurocognitive
brain-computer interfaces has been proposed to help treat conditions
such as stroke, traumatic brain injury, cerebral palsy, autism, and Alzheimer's disease.
The recent field of Assistive Technology for Cognition concerns the
development of technologies to augment human cognition. Scheduling
devices such as Neuropage remind users with memory impairments when to
perform certain activities, such as visiting the doctor. Micro-prompting
devices such as PEAT, AbleLink and Guide have been used to aid users
with memory and executive function problems perform activities of daily living.
Sgt.
Jerrod Fields, a U.S. Army World Class Athlete Program Paralympic
sprinter hopeful, works out at the U.S. Olympic Training Center in Chula
Vista, Calif. A below-the-knee amputee, Fields won a gold medal in the
100 meters with a time of 12.15 seconds at the Endeavor Games in Edmond,
OK, on June 13, 2009
In addition to the standard artificial limb for everyday use, many amputees or congenital patients have special limbs and devices to aid in the participation of sports and recreational activities.
Within science fiction, and, more recently, within the scientific community,
there has been consideration given to using advanced prostheses to
replace healthy body parts with artificial mechanisms and systems to
improve function. The morality and desirability of such technologies are
being debated by transhumanists, other ethicists, and others in general. Body parts such as legs, arms, hands, feet, and others can be replaced.
The first experiment with a healthy individual appears to have been that by the British scientist Kevin Warwick. In 2002, an implant was interfaced directly into Warwick's nervous system. The electrode array, which contained around a hundred electrodes, was placed in the median nerve. The signals produced were detailed enough that a robot arm was able to mimic the actions of Warwick's own arm and provide a form of touch feedback again via the implant.
The DEKA company of Dean Kamen developed the "Luke arm", an advanced nerve-controlled prosthetic. Clinical trials began in 2008, with FDA approval in 2014 and commercial manufacturing by the Universal Instruments Corporation expected in 2017. The price offered at retail by Mobius Bionics is expected to be around $100,000.
Further research in April 2019, there have been improvements
towards prosthetic function and comfort of 3D-printed personalized
wearable systems. Instead of manual integration after printing,
integrating electronic sensors at the intersection between a prosthetic
and the wearer's tissue can gather information such as pressure across
wearer's tissue, that can help improve further iteration of these types
of prosthetic.
Oscar Pistorius
In early 2008, Oscar Pistorius, the "Blade Runner" of South Africa, was briefly ruled ineligible to compete in the 2008 Summer Olympics
because his transtibial prosthesis limbs were said to give him an
unfair advantage over runners who had ankles. One researcher found that
his limbs used twenty-five percent less energy than those of a
non-disabled runner moving at the same speed. This ruling was overturned
on appeal, with the appellate court stating that the overall set of
advantages and disadvantages of Pistorius' limbs had not been
considered.
Pistorius did not qualify for the South African team for the Olympics, but went on to sweep the 2008 Summer Paralympics, and has been ruled eligible to qualify for any future Olympics.
He qualified for the 2011 World Championship in South Korea and reached
the semi-final where he ended last timewise, he was 14th in the first
round, his personal best at 400m would have given him 5th place in the
finals. At the 2012 Summer Olympics in London, Pistorius became the first amputee runner to compete at an Olympic Games. He ran in the 400 metres race semi-finals, and the 4 × 400 metres relay race finals. He also competed in 5 events in the 2012 Summer Paralympics in London.
Design considerations
There
are multiple factors to consider when designing a transtibial
prosthesis. Manufacturers must make choices about their priorities
regarding these factors.
Performance
Nonetheless,
there are certain elements of socket and foot mechanics that are
invaluable for the athlete, and these are the focus of today's high-tech
prosthetics companies:
Fit – athletic/active amputees, or those with bony residua, may
require a carefully detailed socket fit; less-active patients may be
comfortable with a 'total contact' fit and gel liner
Energy storage and return – storage of energy acquired through
ground contact and utilization of that stored energy for propulsion
Energy absorption – minimizing the effect of high impact on the musculoskeletal system
Ground compliance – stability independent of terrain type and angle
Rotation – ease of changing direction
Weight – maximizing comfort, balance and speed
Suspension – how the socket will join and fit to the limb
Other
The buyer is also concerned with numerous other factors:
Cosmetics
Cost
Ease of use
Size availability
Cost and source freedom
High-cost
In
the USA a typical prosthetic limb costs anywhere between $15,000 and
$90,000, depending on the type of limb desired by the patient. With
medical insurance, a patient will typically pay 10%–50% of the total
cost of a prosthetic limb, while the insurance company will cover the
rest of the cost. The percent that the patient pays varies on the type
of insurance plan, as well as the limb requested by the patient.
In the United Kingdom, much of Europe, Australia and New Zealand the
entire cost of prosthetic limbs is met by state funding or statutory
insurance. For example, in Australia prostheses are fully funded by
state schemes in the case of amputation due to disease, and by workers
compensation or traffic injury insurance in the case of most traumatic
amputations. The National Disability Insurance Scheme, which is being rolled out nationally between 2017 and 2020 also pays for prostheses.
Transradial (below the elbow amputation) and transtibial prostheses (below the knee amputation) typically cost between US $6,000
and $8,000, while transfemoral (above the knee amputation) and
transhumeral prosthetics (above the elbow amputation) cost approximately
twice as much with a range of $10,000 to $15,000 and can sometimes
reach costs of $35,000. The cost of an artificial limb often recurs,
while a limb typically needs to be replaced every 3–4 years due to wear and tear
of everyday use. In addition, if the socket has fit issues, the socket
must be replaced within several months from the onset of pain. If height
is an issue, components such as pylons can be changed.
Not only does the patient need to pay for their multiple
prosthetic limbs, but they also need to pay for physical and
occupational therapy that come along with adapting to living with an
artificial limb. Unlike the reoccurring cost of the prosthetic limbs,
the patient will typically only pay the $2000 to $5000 for therapy
during the first year or two of living as an amputee. Once the patient
is strong and comfortable with their new limb, they will not be required
to go to therapy anymore. Throughout one's life, it is projected that a
typical amputee will go through $1.4 million worth of treatment,
including surgeries, prosthetics, as well as therapies.
Low-cost above-knee prostheses often provide only basic structural
support with limited function. This function is often achieved with
crude, non-articulating, unstable, or manually locking knee joints. A
limited number of organizations, such as the International Committee of
the Red Cross (ICRC), create devices for developing countries. Their
device which is manufactured by CR Equipments is a single-axis, manually
operated locking polymer prosthetic knee joint.
Table. List of knee joint technologies based on the literature review.
A plan for a low-cost artificial leg, designed by Sébastien Dubois,
was featured at the 2007 International Design Exhibition and award show
in Copenhagen, Denmark, where it won the Index: Award. It would be able to create an energy-return prosthetic leg for US $8.00, composed primarily of fiberglass.
Prior to the 1980s, foot prostheses merely restored basic walking
capabilities. These early devices can be characterized by a simple
artificial attachment connecting one's residual limb to the ground.
The introduction of the Seattle Foot (Seattle Limb Systems) in
1981 revolutionized the field, bringing the concept of an Energy Storing
Prosthetic Foot (ESPF) to the fore. Other companies soon followed suit,
and before long, there were multiple models of energy storing
prostheses on the market. Each model utilized some variation of a
compressible heel. The heel is compressed during initial ground contact,
storing energy which is then returned during the latter phase of ground
contact to help propel the body forward.
Since then, the foot prosthetics industry has been dominated by
steady, small improvements in performance, comfort, and marketability.
With 3D printers, it is possible to manufacture a single product without having to have metal molds, so the costs can be drastically reduced.
There is currently an open-design Prosthetics forum known as the "Open Prosthetics Project".
The group employs collaborators and volunteers to advance Prosthetics
technology while attempting to lower the costs of these necessary
devices. Open Bionics
is a company that is developing open-source robotic prosthetic hands.
They utilize 3D printing to manufacture the devices and low-cost 3D
scanners to fit them onto the residual limb of a specific patient. Open
Bionics' use of 3D printing allows for more personalized designs, such
as the "Hero Arm" which incorporates the users favourite colours,
textures, and even aesthetics to look like superheroes or characters
from Star Wars with the aim of lowering the cost. A review study on a
wide range of printed prosthetic hands, found that although 3D printing
technology holds a promise for individualised prosthesis design, and it
is cheaper than commercial prostheses available on the market, yet more
expensive than mass production processes such as injection molding. The
same study also found that evidence on the functionality, durability and
user acceptance of 3D printed hand prostheses is still lacking.
Artificial limbs for a juvenile thalidomide survivor 1961–1965
In the USA an estimate was found of 32,500 children (<21 years)
had a major paediatric amputation, with 5,525 new cases each year, of
which 3,315 congenital.
Carr et al. (1998) investigated amputations caused by landmines
for Afghanistan, Bosnia and Herzegovina, Cambodia and Mozambique among
children (<14 years), showing estimates of respectively 4.7, 0.19,
1.11 and 0.67 per 1000 children.
Mohan (1986) indicated in India a total of 424,000 amputees (23,500
annually), of which 10.3% had an onset of disability below the age of
14, amounting to a total of about 43,700 limb deficient children in
India alone.
Few low-cost solutions have been created specially for children. Examples of low-cost prosthetic devices include:
Pole and crutch
This
hand-held pole with leather support band or platform for the limb is
one of the simplest and cheapest solutions found. It serves well as a
short-term solution, but is prone to rapid contracture formation if the
limb is not stretched daily through a series of range-of motion (RoM)
sets.
Bamboo, PVC or plaster limbs
This
also fairly simple solution comprises a plaster socket with a bamboo or
PVC pipe at the bottom, optionally attached to a prosthetic foot. This
solution prevents contractures because the knee is moved through its
full RoM. The David Werner Collection, an online database for the
assistance of disabled village children, displays manuals of production
of these solutions.
Adjustable bicycle limb
This
solution is built using a bicycle seat post up side down as foot,
generating flexibility and (length) adjustability. It is a very cheap
solution, using locally available materials.
Sathi Limb
It
is an endoskeletal modular lower limb from India, which uses
thermoplastic parts. Its main advantages are the small weight and
adaptability.
Monolimb
Monolimbs
are non-modular prostheses and thus require more experienced
prosthetist for correct fitting, because alignment can barely be changed
after production. However, their durability on average is better than
low-cost modular solutions.
Cultural and social theory perspectives
A number of theorists have explored the meaning and implications of prosthetic extension of the body. Elizabeth Grosz
writes, "Creatures use tools, ornaments, and appliances to augment
their bodily capacities. Are their bodies lacking something, which they
need to replace with artificial or substitute organs?...Or conversely,
should prostheses be understood, in terms of aesthetic reorganization
and proliferation, as the consequence of an inventiveness that functions
beyond and perhaps in defiance of pragmatic need?" Elaine Scarry
argues that every artifact recreates and extends the body. Chairs
supplement the skeleton, tools append the hands, clothing augments the
skin.
In Scarry's thinking, "furniture and houses are neither more nor less
interior to the human body than the food it absorbs, nor are they
fundamentally different from such sophisticated prosthetics as
artificial lungs, eyes and kidneys. The consumption of manufactured
things turns the body inside out, opening it up to and as the culture of objects." Mark Wigley,
a professor of architecture, continues this line of thinking about how
architecture supplements our natural capabilities, and argues that "a
blurring of identity is produced by all prostheses." Some of this work relies on Freud's earlier characterization of man's relation to objects as one of extension.