Page 187 - ASOP ROT Study Guide

The Orthopedic Technician as a Professional

1. INTRODUCTION

This module describes the aspects of fracture management in a hospital environment mat
affect you, the Plaster Technician, on a day to day basis. It has been written from a practical
perspective but it also provides information about the reasons for certain procedures and gives
advice about precautions which should be observed in various aspects of your work. Many of the
sections, such as those on safety and First Aid, are not intended to be comprehensive but cover
the basics. Practical instruction in these topics should be sought from qualified instructors. This
is available either through local colleges, voluntary bodies, or within existing educational courses
in the institution in which you work. You may get help from the Nursing Officer in Orthopaedics
or in Accident and Emergency. You could also make enquiries in the department dealing with staff
development and in-service training in your hospital.

2. MATERIALS USED IN THE PLASTER ROOM

2.1 History

Over the centuries, many materials have been used to form casts. In hot countries, such as
Egypt and Persia, splints were fashioned from clay and sticks, or egg white and lime.
Specimens have been found in the mummies of accident victims who were interred with their
splints in place. In Europe wooden splints were used, often associated with strips of cloth known
as clouts. The mtertwining of these clouts was known as clouting and could produce very
supportive splints.

Plaster of Paris, which will be described in detail later, was not used until the nineteenth century.
A Dutch army surgeon, Antoninus Matysen, was the first to combine plaster of Paris with a
bandage. Commercial plaster bandages were originally produced in Germany around 1910,
and these were the first to resemble the modern plaster bandages used today. Commercial
products were not made in the UK until 1949 and materials such as thermoplastics were first
introduced in the 1970s.

It can therefore be seen that the casting materials in use today to treat fractures are relatively
modern. Casting techniques continue to develop as the technology advances.

2.2 Plaster of Paris Bandages

Plaster of Paris is a natural material - calcium sulphate - which was first found in a mine near
Paris at Montmartre. It is extracted in crystal form and heated to remove water, producing an
almost water-free, powdery compound known as calcium sulphate hemihydrate (Ca S04 ViHjO).
If this compound is mixed with water it forms crystals again and "sets" to a solid. This process
results in considerable heat production. The more calcium sulphate hemihydrate there is in the
bandage, the more heat is produced. Therefore, when using plaster of Paris to form a cast, there
is a real risk mat the heat can cause damage to patients if care is not taken.

Commercial plaster bandages are made by dissolving calcium sulphate hemihydrate in an organic
solvent, such as ether, which contains no water. Starch is added to this mixture and the whole
paste is spread on a cotton bandage. This wet bandage is then dried and the solvent collected for
re-use. The bandage is therefore coated with calcium sulphate 'held on' by starch. This is known
as a hard coated bandage.

An old method, as described by Matysen and used until relatively recently, was simply to dust
calcium sulphate hemihydrate onto a bandage so that there was a weak association between
bandage and plaster. A skilled user could use these to make good casts, but much of the plaster
was lost. This type of bandage was known as a loose coated bandage.

2.3 Plaster of Paris Casts

A plaster of Paris cast is made using cotton bandages, hard-coated with crystals of calcium
sulphate hemihydrate as described above. The bandage adds little to the strength but provides a
vehicle for getting the wet plaster on to the part to be splinted. It consists of cotton thread