Prosthesis: Design, Types and Raw Materials

An artificial device known as a prosthesis can help or even completely replace a lost or damaged limb. Prosthetics have undergone a long and fascinating evolution, beginning with peg legs and hand hooks in Ancient Egypt (circa 1500 BC). 

• Though prosthetics have advanced significantly since then, their impact has not changed. 
• The Greek terms "pros" (for furthermore) and "tithenai" are the source of the English word "prosthesis" (to place). 
• Prostheses can either be implanted inside the damaged body part or placed outside.

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Key Terms: Prosthesis, Limb, Myoelectrical Control System, Transradial prostheses.

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What is Prosthesis?

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A prosthesis is an artificial replacement for any bodily component that is missing. 

• The artificial parts that replace missing legs and limbs are those that are most frequently thought of as prostheses. 
• They also include teeth, artificial eyes, and replacements for arteries, bones, and heart valves. 
• The word is occasionally broadened to include devices like eyeglasses and hearing aids that enhance a part's functionality. 
• Prosthetics is the term for the branch of medicine that deals with prostheses.

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Prosthesis Design

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A robotic prosthesis' main objective is to actively operate during gait in order to improve the biomechanics of walking, including, among other things, symmetry, stability, and energy expenditure for amputees. Several powered prosthetic legs are currently available on the market, including fully powered legs, which are defined as prosthetic legs 

• Some of the more particular ones include the empower from BionX, the Elan Foot from Endolite, and the Proprio Foot from Ossur. 
• A number of research teams have also tried robotic legs over the past ten years.
• The design of the device's behavior throughout the swing and stance phases, identification of the current ambulation task, and other mechanical design challenges, including weight, robustness, noise level, and battery efficiency/life, can be listed as the main research questions.

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Types of Prosthesis

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One type of below-knee prosthesis is constructed of plastic and makes full contact with the below-knee stump. It is secured either by a strap that crosses above the kneecap or by hard metal knee hinges fastened to a leather thigh corset. 

• Weight-bearing is made possible by the prosthesis's tension on the tendon that connects the kneecap to the lower leg bone. 
• In addition, a foot piece that comprises a solid ankle and foot with rubber layers in the heel to provide cushioning is frequently employed.
• There are Two Primary Types of Above-Knee Prostheses:

1. The prosthesis is hanging from the shoulder or exists around the pelvis and is secured by a belt.
2. The belt, shoulder straps, and prosthesis—which are held in place by suction on the leg stump—are gone.

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Limb Prostheses

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Arm prostheses are often made of plastic and frequently reinforced with glass fibers, and they are among the sorts of limb prostheses that have undergone the greatest advancements in manufacture since World War II.

• A single plastic shell and a metal wrist joint that are connected to a terminal device, such as a hand or a hook, are held by the below-elbow prosthesis. 
• The person is strapped into a steel cable-and-webbing shoulder harness that extends to the terminal system. 
• The cable is tightened when a person shrugs his shoulder, opening and closing the terminal system. 
• In a few instances, a surgical procedure known as cineplasty can join the biceps muscle to the prosthesis.
• By using this method, a shoulder harness is not required, and the terminal system may be controlled more precisely.
• While the above-elbow prosthesis also has a plastic upper-arm shell, a locking mechanical elbow joint, and a forearm shell. 
• This makes using it more difficult because there should be two cable controls: one to control the terminal device and the other to lock and unlock the elbow. 
• Additionally, the most complex upper-extremity prosthesis, utilized in situations of shoulder amputation, features a plastic shoulder cap that covers the chest and back.

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Prosthetic Raw Materials

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For the amputee's ease, prosthetics are developed to be lighter. These materials include, among others:

1. Plastics:

• Polyethylene
• Acrylic
• Polypropylene

2. Wood Composites (early prosthetics)
3. Rubber (early prostheses)
4. Metals that are thin:

• Titanium
• Aluminum

5. Composites:

• Polymers with carbon fiber reinforcement

The rehabilitation of injured domestic animals, such as dogs, cats, pigs, rabbits, and tortoises, has also made considerable use of wheeled prostheses.

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Myoelectrical Control System

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The most popular and effective terminal device is a metal hook with two fingers-like opening and closing motions. The American Army Prosthetic Research Laboratory (APRL) hand was created following World War II. This is characterized as a mechanical hand made of metal that is covered with a rubber glove that matches the patient's other hand's color.

• There have been numerous attempts to employ electrical energy as the hook or hand control source. 
• The arm prosthesis mainly achieves this by including electrodes that are activated by the patient's own muscle contractions. 
• Batteries and other electrical components boost the electric current generated by muscle contractions, which is then used to power the terminal unit. 
• An arrangement like this is referred to as a myoelectrical control system.
• After a mastectomy, a breast prosthesis may be worn. 
• Although external prostheses are an option, surgical breast reconstruction with prosthesis implantation started to become more prevalent in the 1970s.

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Things to Remember

• Most prosthetic devices are made of lightweight materials like titanium, aluminum, and carbon fiber. 
• A prosthetic typically lasts three to five years.
• The oldest prosthetic device was discovered in Cairo, Egypt, in the year 2000. 
• The wooden and leather prosthetic toe was thought to be close to 3,000 years old.
• The most common type of amputation is a below-knee amputation.
• Currently, there are 2.1 million people living without a limb.
• Although surgical breast reconstruction with prosthesis insertion became increasingly common in the 1970s, external prostheses are still a viable alternative.

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Previous Year Questions

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