How Prostheses Improve Lives: Applications and Innovation
To define prosthetic, it is an artificial substitute for any missing part of the body. The artificial parts that are most often thought of as prostheses are those that replace missing legs and arms, but they also include artery, bone, and heart valve replacements, as well as teeth and artificial eyes. Sometimes, the term is extended to cover such things as hearing aids and eyeglasses that improve the functioning of a part. The medical prosthetics speciality that deals with prostheses are known as prosthetics.
Prosthesis Design
The major goal of a robotic prosthesis is to provide active actuation during gait to improve the biomechanics of gait, including, among other things, symmetry, stability, or energy expenditure for amputees. There are many powered prosthetic legs currently present on the market, including fully powered legs, where the prosthetic leg meaning is given as, they are actuators directly drive the semi-active legs, and joints that use fewer amounts of energy, and a small actuator to change the leg’s mechanical properties but do not inject the net positive energy into gait.
Some of the specific examples can be given as the Proprio Foot from Ossur, the Elan Foot from Endolite, and the emPOWER from BionX. Also, various research groups have experimented with robotic legs around the last decade. Central issues being researched can be given as designing the device behaviour during the swing and stance phases, recognizing the current ambulation task, and different mechanical design problems such as weight, robustness, noise level, and battery efficiency/life.
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Types of Prosthesis
Let Us Discuss the Types of Prosthesis in Detail Here.
One form of below-knee prosthesis is made of plastic and has complete contact with the below-knee stump. It is held on either by means of rigid metal knee hinges attached to a leather thigh corset or by means of a strap that passes above the kneecap. The strain of the prosthesis against the tendon that runs from the kneecap to the lower leg bone allows for weight-bearing. In addition to this, a foot piece can be commonly used that consists of a solid ankle and foot with the rubber layers in the heel to give a cushioning effect.
There are Two Primary Types of Above-Knee Prostheses:
The prosthesis, which is held on by means of a belt, exist around the pelvis or suspended from the shoulder by straps
The prosthesis, which is kept in contact with the leg stump by suction, the shoulder straps, and the belt is eliminated.
The more complex prosthesis used in the case of amputation through the pelvis or hip joint normally consists of a plastic socket in which the individual sits virtually; a leather, plastic, or wooden thigh piece or a metal mechanical hip joint; and a mechanical knee, foot, and shin part.
Limb Prostheses
Out of the types of limb prosthesis, the great fabrication advances of functional upper-extremity prostheses, which followed World War II. Arm prostheses are made of plastic, which is frequently reinforced with glass fibres.
The below-elbow prosthesis holds a single plastic shell and a metal wrist joint that is attached to a terminal device, either a hand or a hook. The individual wears a webbing shoulder harness with a steel cable that stretches to the terminal system. The terminal system opens and closes when an individual shrugs his shoulder, tightening the cable. In some of the cases, the biceps muscle can be attached to the prosthesis by a surgical operation called cineplasty.
This procedure eliminates the need for a shoulder harness and allows for more precise control of the terminal system.
Whereas the above-elbow prosthesis, in addition, has the forearm shell, an upper-arm plastic shell, and a locking, mechanical elbow joint. This complicates its usage, in as much as there should be one cable control for the terminal device and the other control either to lock and unlock the elbow. And, the most complicated upper-extremity prosthesis, which is used in cases of amputation via shoulder, includes a plastic shoulder cap extending over the chest and the back. Generally, no shoulder rotation is possible, but the terminal device and mechanical elbow function as in the other arm prostheses.
Myoelectrical Control System
The most widely used and most powerful terminal device is a metal hook that opens and closes like two fingers. After World War II, the APRL hand (from the U.S. Army Prosthetic Research Laboratory) was developed. This is defined as a metal mechanical hand, which is covered by a rubber glove of a color that is the same as that of the remaining hand of the patient.
Several attempts have been made to use the electrical energy as either the hook or hand control source. This is primarily accomplished by incorporating electrodes into the arm prosthesis that are triggered by the patient's own muscle contractions. The electric current produced by muscle contractions is amplified by batteries and electrical components and used to power the terminal unit. Such an arrangement is called a myoelectrical control system.
Breast prostheses can be used after mastectomy. External prostheses can be worn, but the surgical reconstruction of the breast, involving prosthesis implantation, became increasingly common in the 1970s.
FAQs on Prosthesis: Definition, Types, and Modern Developments
1. What is a prosthesis?
A prosthesis is an artificial device designed to replace a missing body part, which may have been lost through trauma, disease, or a congenital condition. Often referred to as an artificial limb, its primary purpose is to restore the normal functions of the missing part. Beyond limbs, prostheses can also replace other parts, such as eyes, teeth (dental prostheses), or heart valves.
2. What are the main types of prostheses based on amputation level?
Prostheses are primarily categorised based on the location of the amputation. The four main types for limbs are:
Transradial Prosthesis: Replaces an arm missing below the elbow.
Transhumeral Prosthesis: Replaces an arm missing above the elbow.
Transtibial Prosthesis: Replaces a leg missing below the knee.
Transfemoral Prosthesis: Replaces a leg missing above the knee.
Each type is specifically designed to meet the functional needs of that particular level of limb loss.
3. How has the technology used in prosthetics evolved over time?
Prosthetic technology has seen remarkable evolution. Historically, prostheses were often heavy, passive devices made from materials like wood and leather, offering limited function. Modern prosthetics, in contrast, are a product of advanced engineering and materials science. They are made from lightweight, high-strength materials such as carbon fibre, titanium, and advanced polymers. The most significant advancement is the integration of electronics, leading to myoelectric prostheses that use muscle signals to control movement, and neuroprosthetics that aim to interface directly with the nervous system for more intuitive control.
4. What is the difference between a prosthesis and an orthosis?
The key difference lies in their function: a prosthesis replaces a missing body part, while an orthosis supports an existing but weakened or ineffective body part. For example, an artificial leg is a prosthesis. In contrast, a brace used to support a weak ankle or correct spinal curvature (like in scoliosis) is an orthosis. The goal of a prosthesis is replacement, whereas the goal of an orthosis is to assist, align, or correct.
5. How is a custom prosthesis designed and fitted for a patient?
Creating a custom prosthesis is a multi-step process managed by a professional called a prosthetist. It begins with taking a precise measurement of the patient's residual limb, often by creating a plaster cast or using digital scanning technology. This model is used to fabricate a custom socket, which is the critical part that connects the device to the body. Lightweight materials like thermoplastics and carbon fibre are then custom-formed. The final device is assembled, aligned, and fitted to the patient, who then undergoes rehabilitation therapy to learn how to use it effectively.
6. Beyond replacing a limb, what are the functional and cosmetic goals of a modern prosthesis?
Modern prosthetics aim to achieve two main goals: function and cosmesis.
Functional Goal: This is about restoring mobility and the ability to perform daily activities. For a leg prosthesis, this means stable walking and running. For an arm, it could mean grasping and holding objects. Advanced prostheses use myoelectric sensors to enable complex movements.
Cosmetic Goal (Cosmesis): This focuses on creating a life-like appearance. A cosmesis is a realistic, skin-like covering for the prosthesis, designed to match the patient's skin tone, shape, and even details like freckles or hair, helping with psychological well-being and social integration.
7. How do myoelectric prostheses work?
Myoelectric prostheses are advanced devices that use the body's own electrical signals to control movement. When a person tenses the muscles in their residual limb (the part of the limb remaining after amputation), those muscles generate a small electrical signal (an electromyographic or EMG signal). Electrodes placed on the skin inside the prosthetic socket detect these signals. A processor within the prosthesis interprets these signals as commands (e.g., "open hand" or "close hand") and powers small motors to move the prosthetic hand, wrist, or elbow accordingly.
8. What common materials are used to make modern prosthetic devices?
The choice of material is crucial for making a prosthesis both strong and lightweight. Early prosthetics used heavy materials like wood and steel. Today, a range of advanced materials are used:
Carbon Fibre Composite: Valued for its exceptional strength-to-weight ratio, making limbs durable yet easy to move.
Titanium and Aluminium Alloys: Used for structural components due to their strength and resistance to corrosion.
Thermoplastics: These plastics can be heated and moulded to create custom-fitted sockets.
Silicone: Often used for creating the cosmetic covering (cosmesis) as it can be coloured and textured to resemble skin.
