Prosthetic Limbs

Making Prosthetic Limbs

Introduction To Making Prosthetic Limbs

The purpose of a prosthetic limb is to offer a certain degree of function back to an amputated arm or leg. Prosthetic limbs have been used since antiquity, but only in recent times have they become efficient and successful ways of replacing an actual limb. Starting in the twentieth century, prosthetic limbs now use sensors that can read impulses from the brain. This offers a certain degree of mobility to the limb, making them more than just an aesthetic addition.

Artificial limbs are usually made out of a custom fitted socket, knee cuffs and belts that make sure it stays attached to the body and. It is then covered by a material making it look as close as possible to an actual body part (sometimes artificial skin). Since it's supposed to be light, the main material that is being used is plastic, but wood and rubber are also used for certain components. The making of a prosthetic limb, requires three steps:

Step 1: Measuring And Casting

Prosthetic limbs are usually prescribed by a doctor - afterwards the patient visits a prosthetic surgeon who will build the limb based on the patient's measurements and particular details. While most of the elements of the limb are manufactured in a factory, the end result is custom made to fit the arm/leg that the prosthetic is replacing. On top of the actual size of the patient, the prosthetic surgeon measures the positioning of the relevant body part in terms of bones and tendons, so that the limb is properly connected.

After the measuring is done, the prosthetic surgeon makes a plaster cast of the stump, afterwards creating an exact duplicate of it, helping the actual limb manufacturing process.

Step 2: Socket Building

A thermoplastic sheet is then used to create a test socket; it is heated in an oven around the plaster cast. Afterwards, the air between the thermoplastic sheet and the plaster cast is vacuumed, making it fit the exact shape of the mould. The thermoplastic sheet is transparent, so it is easy to see if it actually fits the shape.

The test socket is then tested on the patient, to check for comfort and suitability. The patient wears it for a period of time, offering feedback in terms of how the limb feels. Due to the flexibility of the material out of which the socket is made, the necessary adjustments can be easily made.

A permanent limb is afterwards created, made of polypropylene, based on the shape of the test socket. The process is very similar to the creation of the test socket. After about a year, the patient comes back for a resizing, since it often happens that the stump shrinks after that period of time.

Step 3: Prosthetic Fabrication

The last step involves various mass-made components being built around the custom-made socket, leading up to the prosthetic limbs final shape, using bolts, adhesives and laminating. The entire limb is then put together by a technician, using wrenches and screwdrivers.

The end of the process also requires physical therapy - making the patient comfortable with the limb and training the muscles that will from now on be used in working the device. For patients with amputated legs, it usually takes 18-20 weeks to learn to walk again. For patients with amputated arms, an instruction system is built around fulfilling easy tasks with only one hand, for emergency situations.