Plaster of Paris: In 1852 powder gypsum was first used as splint and for immobilization of fractures. This powder is now known as plaster of Paris.
Plaster of Paris is hemi-hydrated calcium sulphate [(CaS O] powder.
Plaster of Paris reacts with water to from hydrated calcium sulphate and become solid.
Plaster bandage can be made with cotton bandage impregnated with Plaster Paris powder. Now commercially prepared plaster bandage are available.
Types of Plaster of Paris:
- Plaster slab (Incomplete)
- Full plaster cast (Complete)
- As splint in fracture as first aid treatment.
- Immobilization of fracture as definitive treatment.
- To correct some deformities.
- To immobilize joints sometimes in infection.
- Immobilization to prevent pathological fracture.
- Extra support in some cases of internal fixation.
- It is cheap.
- Easily available.
- Easily changeable.
- Hazards of operation can be avoided.
- Can be molded properly over the contour and bony prominences.
- Angulations of limb may be corrected by cutting the plaster partially.
- Duration the process of setting of plaster, it neither shrinks nor expands.
- Does not change the shape after setting.
- Plaster bandage can be applied in any limb or any part of the body in any size.
- It is non-inflammable.
- Pressure sore over bony prominences and at the sharp margins.
- Nerve palsy.
- Edema/ Swelling, distal to the plaster.
- Infection under plaster.
- Deep vein thrombosis.
- Stiffness of immobilized joints.
- Disuse osteoporosis.
- Disused atrophy of muscle.
- Renal calculi.
- Hypostatic pneumonia.
How to correct contracture by using plaster casts:
- Put stockinette or a close fitting cotton stocking on the leg. Avoid wrinkles.
- Put cast padding or cotton roll (or wild kapok) evenly around the leg.
- To protect the knee, it helps to put a soft sponge or piece of sponge rubber over the knee.
- Put extra padding around the thigh, the knee and the ankle.
- Put a plaster cast on the leg. Be sure it reaches high up the thigh.
- Put length wise strips of plaster for reinforcement over the knee.
- Holding the calf below the knee, gently straighten the leg as far as it will go, without using force.
- Position the foot at a right angle (or as near to it as you can without using force)
- Cut through the plaster behind the mnee.
- Use steady, gentle pressure so that the leg straightens a little and the cut opens.
- Hold the cut open with a small wedge of wood.
- Warp a piece of cloth around the knee.
- Then wrap a thin ring of plaster around it to keep the wedge in place.
- Cut and remove the ring of plaster.
- Gently stretch the joint and put in a wider wedge.
- And cover it with a new ring or plaster.
Fourth week: Each time you change the ring, put in a bigger wedge.
Fifth week: Continue casting until the knee is completely straight or bends back ward just a little. Then use a brace for at least a few weeks (day and night) to keep it straight.
Sixth week: The time to straighten a contracture may vary between 2 weeks and 6 months or more. If the leg stops straightening for 3 or more cast changes, stop casting and try to arrange surgery.
(Here is the description for the knee but the basic methods are the same for contractures in ankles, feel, elbow and wrists)