A plaster cast, slab or splint is applied in broken bones of upper or lower extremity. Plaster can be applied for temporary period while waiting for definitive treatment or it could be definitive treatment in itself.
What Are Uses of Plaster Cast Application
Basic aim of a plaster application is immobilization of the fracture fragments and joints.
A plaster could be
- A temporary measure pain relief and reduction of swelling so that definitive treatment could be executed.
- For immobilization of joints in case of ligament injury, joint swelling due to disease.
- A splint for undisplaced fractures.
- A definitive treatment where plaster is applied to maintain the reduction of the fragments.
- External splint to aid with the internal fixation of the fractures, osteotomies and other bone surgeries where internal fixation alone would not be able to withstand loads.
- External splint for blocking movements in case of nerve, tendon or vessel repair.
Principles of Plaster Cast Application
Traditionally plaster of Paris casts are used. You must have seen those white colored casts, those are made of plaster of Paris or POP.
Another material which ic commonly used now is fiberglass cast. It is a special kind of plastic which when comes in contact with water turns hard. It is available in many colors.
Rule of thumb for plaster applications block a joint above and below the fracture. This is done as movement of either joint can cause movement in fracture fragments.
For immobilizing the joint, a plaster should be adequate enough to counter the forces of the muscles that move the joint.
Majorly, a plaster, depending on its extent, could be
An above elbow plaster cast or slab is applied from knuckles of hand [distal palmar crease anteriorly] and covers lower two thirds of arm
While distal extent is same as above, proximally the plaster ends below elbow elbow crease.
Distal extent is up to metatarsophalngeal joints and proximally it covers lower two thirds of thigh.
Distal extent is same, proximal extent ends below knee.
There are various other types of casts used in case of a number of fractures where the extent and position is defined by the type of plaster applied.
Plaster slabs or cast may have same extent but different joint positions depending upon conditions.
Plaster Slabs and Plaster Casts
A plaster cast is a circumferential application of plaster bandages. Cast is stronger by virtue of being circumferential than slabs, control the reduction of fragments better and withstand mechanical stresses better. Most of the closed reductions of the fractures require cast application.
Slab is a support created from plaster material which is applied on one aspect of the limb and secured with cotton bandages. Sometimes, two slabs may be applied, for example one anterior and second posterior, for better strength and control.
Slabs are applied in case where there is swelling , poor skin condition that needs to be observed like blisters, after internal fixation to aid the fixation, while waiting for definitive treatment. Many undisplaced fractures are treated by slab application.
Though few people had advocated this in the past, a plaster cast or slab is not applied without the padding.
Soft resilient material such as wool, felt and special orthopaedic padding is placed on the skin before plater application.
Padding serves to
- prevent sores
- increase comfort
- act as a spacer to aid removal.
Traditional casts are made of plaster of Paris material. Other materials like fiberglass casts are also applied now. Fiberglass is a type of plastic that can be shaped.
Fiberglass casts are lighter and more durable than traditional plaster casts. There is better air circulation in the cast and xrays also have better penetration making it easier for the clinician to evaluate the union of fracture
How to Apply Plaster
For details of the procedure, please click on the relevant link.
Care of cast
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