A) MATERIALS AVAILABLE IN INDIA AND PRODUCTION PROCEDURES

The materials utilised for prostheses are mainly bamboo, HDPE, steel, resins, "Raxider", wood and polymers, aluminium (mostly for callipers), leather, soft leather and foam.

Bamboo

Classified in more than one thousand species, bamboo has from ancient times been used in many Southeast Asian and African countries. This is due not only to its easy availability but also to the mechanical properties stemming from its "stratified" structure.There are three phases in the preparation of bamboo:

1) Harvest and desiccation during the dry season. Subsequently, paint is applied over the entire surface to prevent external damage.

2) Shaping and folding. During this process different thicknesses are rolled in order to obtain the necessary components.

3) The components are assembled and trimmed using nails, bolts and glue. The average life of a prosthesis varies from two to three years

.The disadvantages of using bamboo are:

1) Deterioration

2) Brittleness

3) During the shaping phase some fibres are burned and must be replaced.

The advantages of using bamboo are:

1) It is a natural material.

2) Its processing requires low energy consumption.

3) It is easily found in developing countries.

4) Its production technology is simple and cheap.

5) Its use does not produce industrial waste.

6) It is a versatile material.

7) It is familiar to the local people.

Therefore, bamboo is a valid alternative to those biomedical engineering solutions which are not feasible due to environmental, social or economic conditions.

High Density Polymers (HDPE)

The material most used instead of bamboo is HDPE (Ethylene Polymers) whose characteristics change with the percentage of crystallisation. World production of HDPE is approximately 14 million tons per year. A component made out of this material is the potting of the prostheses whose production process is as follows:

1) The resin is bought in metal tubes which are cut into various lengths as necessary. All the pieces are internally and externally covered with cotton strips.

2) The tubes are put in induction furnaces for 1-1/2 hours.

3) After this the material has the proper consistency to be worked.

4) Thereafter each piece is quickly put into a pre-prepared plastic mold.

This phase must be rapid and accurate, otherwise the piece has to be rejected.HDPE's advantages are:

1) The final product has very good mechanical characteristics.

2) It is immune to external agents like bacteria or fungus.

3) It is easy and fast to work.

4) It is comfortable to wear.

5) It is a cheap raw material (with a $35 tube, 25 transtibial prostheses can be made).

Its disadvantages are:

1) It requires technical knowledge higher than that of an artisan.

2) Its production needs equipment which is expensive and not easy to find.

3) If the shaping is incorrect during the production process, the piece cannot be recycled.

 

Kuntala Jayaraman,

Anna University, India

Rajko Schmidt

Otto von Guericke University, Germany

Marco Bozzetti Elisabetta Papa, Andrea Raggi

I.LI.TEC.,Italy

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