Module 2- Prosthetic Limbs Flashcards
What is a prosthesis?
- An artificial device that replaces a missing body part, which may be lost through trauma, disease, or congenital conditions.
- Prosthetics are intended to restore the normal functions of the missing body part.
First prosthetic
- The first prosthetic could have been The Cairo Toe
- A prosthetic toe was found by unearthing a mummy in Cairo, Egypt, in the year 2000 and dates back 3000 years — it was made of wood and held on with leather straps
The first documented wearer of a prosthetic limb was Marcus Sergius
A Roman general during the Second Punic War (218 to 201 BC), Marcus had a metal hand constructed to allow him to hold his shield in battle.
How has surgery advanced to ease the burden of amputations?
- In the Middle ages, there was little progress in the development of prosthetics and our understanding of the limbs.
- Anesthesia was introduced in the 1840s — opening doors to painless surgery.
- By the mid-19th century, we could shape a residual limb that made it receptive to the attachment of a prosthesis.
The Hanger Limb
- With the carnage of the Civil War, advances in prosthetics became prominent again.
- The Hanger Limb was made of metal and contained a hinged knee and ankle —becoming the most advanced prosthetic of the time.
- J.E. Hanger’s company continues to be a leader in prosthetics today.
Defence Advanced Research Projects Agency
DARPA was formed by the American government in response to Sputnik in 1957. The government pledged that future national research would be the “initiator” and not the “victim” of strategic technological surprises.
How many types of prosthetic limbs are there?
4
What are the 4 types of prosthetic limbs?
- Below the knee (BK, transtibial) — a prosthetic lower leg attached to an intact upper leg
- Above the knee (AK, transfemoral) — a prosthetic lower and upper leg, including a prosthetic knee
- Below the elbow (BE, transradial) — a prosthetic forearm
- Above the elbow (AE, transhumeral) — prosthetic lower and upper arm, including a prosthetic elbow
The Standard Components of a Prosthetic Limb
- Socket
- Suspension system and
attachment Mechanism - Joint (if necessary)
- Pylon
- Terminal device
Fit as a consideration in prosthetics
- A very important consideration is fit — a carefully detailed socket fit
- Fit is measured using laser scanners and CT scans.
- CAD software to begin the process of design, based on the real anatomical data of the specific patient.
Design considerations in prosthetics
- Fit — carefully detailed socket fit
- Energy storage and return — storage of energy acquired through ground contact and usage of that energy for propulsion
- Energy absorption — minimizing the effect of impact on the musculoskeletal system
- Rotation — ease of changing direction
- Ground compliance — stability independent of terrain
- Weight — maximizing comfort, balance, and speed
- Patient concerns — cosmetics, costs, and ease of use
Attachment of prosthetic limb
- A well-fitting prosthetic is usually secured to a residual limb by straps, harnesses, or even by suction.
- A snug, secure fitting is vital for comfort — and ensures the limb can be properly controlled.
What’s wrong with surface-mounted prostheses?
- These prosthetics compress onto the skin and can cause pain and poor fit — leading to slippage and further problems.
- There is a short life to soft mount given volume changes. They are difficult removal and attach.
- Surface-mounted designs induce a loss of load perception through bone.
Overview of attachment by osseointegration
Osseointegration alleviates worries about issues such as heat and chafing that prosthetic sockets give — there is increased mobility, comfort, and function.
Advantages of attachment by osseointegration
The direct connection between the prosthesis and bone has several advantages:
- It provides greater stability and control and can reduce the amount of energy expended.
- It does not require suction for suspension, which makes it easier and more comfortable for the user.
- The weight‐bearing is brought back to the femur, hip joint, tibia, or other bone, reducing the possibility of degeneration and atrophy that can accompany traditional prostheses.
- Integral to proprioception
Progression in osseointegration
Stimulating osteoblast activity
- Metal foams (monetite crystals) may promote and contribute to bone infiltration and the formation and growth of vascular systems within the defined area.
- The porous, bone‐like metal foam allows osteoblast activity to begin.
Body- vs. external-controlled prosthetics
- With body-controlled prosthetics, there is a cable attached to a ring harness, which controls opening and closing of the hook.
- A microprocessor receives inputs from the sensors and allows adjustments to approximate natural gait.
Prosthetics Controlled by Myoelectricity
Myoelectric refers to the electrical signals produced by muscles — these are typically difficult to control and have limited function.
iLimb, Touch Bionics, and Myoelectric
- The hand uses a rotating thumb and individually powered fingers to form various grips. In each of the fingers, a sensor recognizes the level of resistance on an object and tells them to stop grasping.
- The five individually powered fingers grips around objects and locks when enough force has been used.
- The skin covering is convincingly life-like, with knuckles and fingernails.
Targeted Muscle Reinnervation (TMR)
- Neurons that are typically bundled into the residual limb can reinnervate nearby muscle and electrodes record those signals
- TMR is meant to improve upon, but not replace, myoelectric control by amplifying the signal
DEKA Arm
- The first TMR controlled FDA approved device (2014), it’s still controlled by myoelectricity.
- Costs between 50,000 USD to 80,000 USD and requires replacement every 3-4 years.
Modular Prosthetic Limbs- features
A modular prosthetic limb features…
● Anthropomorphic (lifelike) form factor and appearance
● Human-like strength and dexterity
● High-resolution tactile and
position sensing
● Neural interface for intuitive and
natural closed-loop control
Modular prosthetic limb- function
- At the individual joints, sensors measure angle, velocity, and torque.
- Additional sensors at the fingertip measure force, vibration, fine point contact, and temperature/heat flux.
Experimental therapies for phantom limb pain
- Mirror box therapy is used to create a reflective illusion of an affected limb to trick the brain into thinking movement has occurred without pain
- Repetitive transcranial magnetic stimulation (rTMS) is FDA-approved for depression and certain psychotic disorders
Lower-limb amputees in India
- Professor P. K. Sethi observed that lower limb amputees in India would prefer to go along in crutches over using a solid ankle-cushion heel — the prosthetic was too rigid and broke too easily.
- A suitable prosthetic
was needed for amputees.
Jaipur Foot
- Consisting of 3 blocks (rubber hind foot, rubber forefoot, and laminate wood for ankle block), this prosthetic can bear weight, and withstand pressure while providing a proper range of motion and attaching securely to the stump.
- The rubber forefront allows for multidirectional movement and allows for movement on uneven grounds.
Developing the socket for the Jaipur foot
- The socket was designed with high-density polyethylene — a light-weight material with high impact resistance and tensile strength.
- Already formed pipes mean a short fabrication time, ideal for the high demand of prosthetics.
