Plaster casts are often made from plaster of Paris. They are devices that encase an injured part to protect, support, and immobilize it. Especially during the healing process, and are often used to prevent or correct a deformity.
Plaster of Paris bandage is a gauze cloth containing plaster of Paris crystal powder. Your doctor will use the bandage mainly used to protect and immobilize a broken limb. The plaster bandages are often chosen over other options due to their durability and firm cast-formation. Read below to learn more on the topic.
Why Plaster of Paris Casts are Used
Casts are generally supportive devices used to help keep an injured bone in place while it heals. Splints are also called half casts – a less supportive, less restrictive version of a cast.
Casts and splints might help treat broken bones and injured joints and tendons. Plaster of Paris bandage is often used after bone, joint, or tendon surgery.
The purpose of a cast or splint is to immobilize a bone or joint – while the joint heals from an injury. The bandage helps to restrict movement and protect the area from further injury.
At times, your doctor would use casts and splints together. For example, they may stabilize a fracture with a splint first. Later replace it with an entire case. After the initial swelling, the area goes away. Other fractures may need just a cast or just a splint.
Purpose
- To support, immobilize, and protect a part of the musculoskeletal system during the healing process.
- To prevent or correct deformity.
- To relieve pain associated with a fracture of a bone in the area. It also helps relieve muscle spasms and prevents displacement of the fractured bone fragments.
- To maintain a particular position and enforce rest.
Things Used For Application of Plaster Casts
1. Plaster of Paris (gypsum salt)
Plaster of Paris is soft and malleable when you moisten it with water but becomes rigid and durable when dry. It is anhydrous calcium sulfate which is a chalky white powder. It is made by a process that removes water from gypsum.
In making plaster of Paris, large gypsum crystals are broken up and reduced to powder. Intense heat is applied to make them into powder. The process will remove water from the crystals. When plaster of Paris is placed in water – a chemical process of rehydration occurs. You can quickly feel the newly applied cast -as heat is produced during the recrystallization or set period.
A plaster cast becomes firm or sets in rapidly. But it may take a long period to dry. During this set period, there should be no movement in the area being treated. Otherwise, it may produce a crack in the cast and thus making the cast weak.
Newly Set Cast
A newly set plaster cast is often called a green cast. It contains excess water, which adds to the cast’s weight. Eventually, this water evaporates, leaving a dried cast – which is lightweight and porous too.
The porous nature of the plaster – will permit moisture evaporation from your skin. The cast will attain its full strength once evaporation of complete water occurs. Plaster casts take variable time to dry, depending on their size. The following factors influence the setting:
- The type of plaster your doctor uses.
- The thickness of the cast.
- The condition of the surrounding env.
- The temperature of the water. Meaning warmer temp will speed up the setting time. While colder temp will slow down the setting time.
Plaster casts are applied by applying 5 – 7 or more layers of plaster bandages depending on the injury. You can find plaster of Paris bandages in individually wrapped pre-cut rolls of crinoline impregnated with plaster of Paris.
The bandages available in the market vary in width from 5 to 15 cm. They are known for varying setting periods as well. The strength of the plaster cast is determined by the number of layers of plaster bandages your doctor uses. Plaster splints (slabs) might strengthen and reinforce cast areas- especially areas requiring additional support.
2. Stockinette
Do you know stockinette is a soft knit material in tubular form? It resembles a footless stocking without seams. It is available in rolls of various widths, 5 to 40 cm – you can use it to cover any body part. The cast will protect the skin under the plaster cast. In simple terms, it forms a lining for the model. Stockinettes are also helpful as they protect the edges of the plaster casts as well.
3. Padding
Adequate padding with cotton is necessary to protect your skin and bony prominences under the plaster cast. Your doctor will apply padding directly over the skin or stockinette covering. Note that the padding used should be smooth and without wrinkles.
4. Warm Water
Water at the temp of 35 to 40.5-degree celsius is necessary to saturate the plaster bandages. The temp of water used primarily influences the setting time of plaster.
Warmer temperatures will speed up the setting time. When your specialist applies a large cast, changing the water in between may be necessary. Otherwise excessive sediments of plaster might accumulate and begin to adhere to the new rolls of plaster, causing a slow setting of the plaster. The process will produce lamination and weakness of the cast, which is not preferred.
5. Special Tables (Orthopedic Tables)
Your specialist will use a special table, called orthopedic tables – for the application of the cast. It has devices to support the uncasted area leaving. Thus the area on which the cast is applied is left free.
Types of Plaster of Paris Casts
1. Short Arm Cast (Wrist Plaster)
Your specialist will apply short arm casts to treat the fractures – of the carpal and metacarpal bones and for the dislocation of the wrist joint. This cast extends from below the elbow to the phalanges. The fingers are often left free to check the blood circulation and movement in the arm.
2. Long Arm Cast (Above-elbow Plaster)
Your doctor will use this in the treatment of the fractures of one or both bones of the forearm.
They will use it for the dislocation involving the elbow joint. This long arm cast extends from below the shoulder to the phalanges. Note that the the The elbow joint is kept flexed.
3. Short Leg Cast (Below-knee Plaster)
Your doctor will use this type of plaster cast to treat the fractures of the tarsal and metatarsal bones. They will also use it for dislocation, sprains, etc., involving the ankle joint.
It is important to note that short leg casts might be either weight-bearing or non-weight-bearing. If your doctor uses it for bearing a person’s weight during ambulation, it is fitted with a walking heel. In such a scenario, the ankle joints are kept at 90-degree angle. The plaster of Paris cast is applied from below the knee to the toes. The toes are always left exposed.
4. Long Leg Cast (Above-knee Plaster)
Your doctor will use this treatment to treat the fractures of the lower leg bones. It may also involve the knee joint. It extends from below the groin to the toes.
5. Spica Cast
Your doctor will apply this to the shoulder, hip, and thumb joints. A shoulder spica cast combines a body jacket and a long arm cast. Your doctor will use this plaster of Paris bandage to treat the fractures of the shoulder humerus, girdle, dislocation of the shoulder joint etc.
Note that hip spica typically extends from the mild trunk just below the nipple line down to the entire length of one leg. It covers the affected side. The plaster of Paris cast will have an opening around the buttocks and perineal region, especially for the purpose of cleanliness and elimination.
Do you know that your doctor will use hip spica casts to treat congenital dislocation of the pelvis? They will also use it to treat hip joints or pelvic bones and femur fractures. Hip or shoulder spica casts might be reinforced by plastering a stick or bar between the extended portions of the cast.
6. Bivalved Casts
Bivalved a cast means splitting it along both sides. A cast may be bivalved for the following purpose:
- It allows space for tissue swelling when it is expected in an area.
- It helps treat a surgical wound.
- The cast facilitates skin care when skin damage is expected. It does not disturb the body alignment.
- Your doctor can make a half cast which can be used as an intermittent splint that prevents deformities.
- It helps the client to adjust gradually without a body cast.
The top half is removed. The patient lies in the bottom half of the cast and vice versa. When reapplying the bivalved cast, your doctor will handle the client carefully. They will take care not to pinch the skin between the two halves.
7. Body Casts
Your doctor will often use two types of body casts – Minerva jackets and body jackets. Your doctor will use a Minerva jacket that covers the frontal and occipital regions of the skull. It extends over the chest, neck, back, abdomen, and iliac crests. Note that the cast will expose your ears, face, and upper extremities.
The body jacket typically extends from the upper chest to the pubis. This plaster of Paris bandage exposes the buttocks and perineal area. Some of the body casts may also include thighs.
Your doctor will use both Minerva casts and body jackets to immobilize the spine. It helps to promote the healing of surgical spinal fusions and spinal injuries or to relieve degenerative disorders. They may also use body casts to immobilize the spine in a position of hyperextension when treating compression fractures.
If applied too tightly over the chest and abdomen, body casts will interfere with the chest expansion during breathing and may cause abdominal discomforts. Body casts are sometimes prepared several days before surgery. It is bivalved and removed when dry and then it is reapplied when the operation completes.
Conclusion
An application of a plaster cast is entirely the responsibility of the doctor. The responsibility of the nurses lies in the preparation of the client. Thus helping the doctor in applying the plaster of Paris cast and also taking care of the patient.
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