Polyurethane in
Prosthesis
Polyurethane has been
finding wide usage in many of biomedical and therapeutic applications. One such
application is prosthesis. Prosthesis means artificial replacement for a
missing limb. Most widely used prosthesis for rehabilitation includes feet,
legs, arms and hands. Others include
dental , facial and heart valve etc. Correctly
made prosthesis has proven a major enabler to many people globally. What could
have been better fitting example than the recently held Paralympic events at
Rio? In fact some of the Olympic records
were beaten at Paralympic events this year.
Like
many Indians, my early introduction to prosthesis was to famous Jaipur foot. As
the name suggests these are below knee prosthetic which before the era of
globalization has helped in rehabilitation of many people including soldiers,
accident victims and polio patients. Low cost and custom-made products have
been two most attractive features of Jaipur Foot. Over the years technological
developments have aided the transformation of earlier wood-rubber based products
to combination of metals with polyethylene, polyurethane.
Various forms of Jaipur Foot
[www.jaipurfoot.org]
Light weight, strength,
flexibility, non-abrasiveness, durability, antimicrobial properties and soft to
tissues – these are some of the common desirable properties of the prosthetic.
However depending upon the final application, multiple complexities get added. Further each prosthetics has to be designed as
per the life style, physical characteristics of the individual. Hence most prosthetics require multiple types
of materials for the fabrications. Polymers have become choice of materials for
prosthetic application due to properties like high strength, non-corrosive
nature, light weight, impact strength, toughness, flexibility etc. Use of low weight reinforcing fillers has
added another dimension to make light weight and stronger part. Carbon fiber
has been introduced few years ago due to its strength at very low loadings in
the composite form.
In addition to the
material development, designing has also evolved tremendously in the prosthetics
development. This year, Paralympic participants have used 3D-printed prosthetics. Introduction of better mechanical designs through use
of electrical signalling and robotics have improved the functionality of
prosthetics in recent years.
Polyurethane
has been used in prosthetic applications for its shock absorption capacity to
reduce vibrations. Due to its availability in a very soft form, polyurethane
has been used along with silicone as a liner material. Polyurethane foam has
been used as a cushioning material for its ability to distribute pressure
evenly.
Application of
polyurethane in prosthetic foot (www.oandp.com]
In
addition, features like easy fabrication, wear resistance, resilience, high
strength to weight ratio, easy to clean, ability to withstand weight of the
person without disintegration make polyurethane foam an ideal choice of
material in prosthetic. Other
applications include inserts, leg sleeve, grip pads
for hand prosthetic, as a matrix in carbon fiber based composite for foot
prosthetic, as a elastomer for designing socket and polyurethane adhesive to
glue various parts.
