Parts of Transtibial Prosthesis

Transtibial prosthesis consist the following parts

•       Socket

•       Socket adopter

•       Shank

•       Foot adopter

•       Foot

Note: All the above mentioned components are discussed in detail.

Prosthetics sockets

•       Prosthetic socket connect the residual limb to the prosthesis.

•       It provides optimum support to the patient and ensures a good prosthesis fitting.

•       The prosthetic socket consists of a liner and a matching closure system.

•       The liner acts as a sort of “second skin” between the movable soft tissue of the residual limb (muscles, tissue, skin) and the hard shell of the socket.

•       It is custom–made according to the shape and condition of the residual limb and the respective mobility grade.

OBJECTIVES OF SOCKET

•       Total Contact.

•       Good sensory feed back.

•       Loading Pressure Tolerant Areas.

•       Relieving Pressure Sensitive Areas.

•       Light in Weight.

•       Cosmetically Acceptable.

•       Strong enough for weight bearing.

•       Suspend the prosthesis.

•       5-10° of socket flexion exposes more of the anterior wall for weight bearing.

PARTS OF SOCKET

•       Prosthetic socket consist of

o   Soft inliner(second skin)

o   Laminated socket 

SECOND SKIN

The “second skin” is

•       thin protective membrane

•       made of a flexible material

•       Rolled over the residual limb.

•       It connects the residual limb of patient to the socket.

•       Selection of right liner is essential so that prosthesis fits well and is comfortable to wear.

•       For optimum patient safety and comfort there should be a good combination of liner and closure system.

The single most critical aspect of any
prosthesis is the quality of the interface
between the residual limb and the
prosthesis.” Marks & Michael (2001)

FORCE ACTS ON A SOCKET

There are three types of forces act on socket during normal gait.

·          Impact forces generated when heel strikes the ground.

§  Soft liner and shock-absorbent feet minimize impact forces.

·         Rotation forces occur during the stance phase can cause rotation in the socket. The shape of the socket combined with special connective techniques (e.g. negative pressure) can be used to minimize rotation forces.

·         Shear forces also known as lifting forces. Occur during the swing-through phase, and can be controlled with the help of the right liner material and correct closure system. 

    MATERIALS USED IN A SOCKET

•       P.V.A files

•       Stockinet

o   Perlone

o   Nylone

o   Dacron

o   Cotton

•       Fiber glass/carbon fiber

•       Risins

•       Hardner

•       Accelerator(catalyst)

•       Socket adapter

TYPES OF SOCKET

•       Leather sockets(Provide flexibility and Adjustment),

•       Wooden Sockets.

•       laminated/moulded

o   They are total contact sockets.

•       Flexible

•       Rigid

•       Mainly there are four types of sockets

1.       Patellar Tendon Bearing (PTB).

2.       Kondylen buttlen munster (KBM)

3.       Supra condylar (medial wedge).

4.    Supra-condylar and supra-patellar.