PLASTER CASTS – Purpose,
Articles Used, Types,
Application – Nurse Procedure
PLASTER CASTS
Plaster casts made from plaster of Paris are devices that encase an injured part in order to protect, to support and to immobilize it during healing process and are used to prevent or correct a deformity.
Purpose
1. To immobilize, to support and to protect a part of the musculoskeletal system during healing process
2. To prevent or correct deformity
3. To relieve pain associated with fracture of bone by relieving muscle spasm and preventing displacement of the fractured bone fragments
4. To maintain a particular position and enforce rest
ARTICLES USED FOR APPLICATION OF PLASTER CASTS
1. Plaster of Paris (gypsum salt)
Plaster of Paris is soft and malleable when moistened with water, but is hard and durable when dry. Plaster of Paris (anhydrous calcium sulphate) is chalky white powder made by a process that removes water from gypsum. In the process of making plaster of Paris, crystals of gypsum are broken up and reduced to powder and intense heat is applied. This removes water from the crystals. A chemical process of rehydration occurs when plaster of Paris is placed in water. The heat produced during this recrystallization, or ‘setting’ period can be felt in the newly applied cast.
A plaster cast becomes firm (sets) rapidly but it takes a long period to dry. During this setting period, there should be no movement which may produce a crack in the cast and makes the cast weak. A newly set plaster cast is called a ‘green cast’. It contains excess of water which adds to the weight of the cast. Eventually, this water evaporates leaving a dried cast which is light in weight and is porous. The porous nature of the plaster permits the evaporation of moisture from the skin. A cast attains its full strength, once an evaporation of complete water occurs. Plaster casts take variable time to dry. Setting is influenced by:
a. The type of plaster used
b. The thickness of the cast
c. The condition of the surrounding environment
d. The temperature of the water (warmer temperature speed up the setting time, while colder temperature slows down the setting time).
Plaster casts are applied by applying 5 to 7 or more layers of plaster bandages. Plaster of Paris bandages are available in individually wrapped pre-cut rolls of crinoline impregnated with plaster of Paris. The bandages are available for varying widths from 5 to 15 cm. they are available for varying setting periods. The strength of the plaster cast is determined by the number of layer of plaster bandages used. Plaster splints (slabs) may be used to strengthen and re-inforce area of casts which require an additional support.
2. Stockinette
Stockinette is a soft knit material which is in tubular form, resembles a footless stocking without seams and is available in rolls of various widths (5 to 40 cm) to cover any part of the body. It protects the skin under the plaster cast and form a lining for the cast. Stockinettes are also helpful to protect the edges of the plaster casts.
3. Padding
An adequate padding with cotton is necessary to protect the skin and bony prominences under the plaster cast. Padding is applied directly over the skin or over a covering of stockinette. The padding applied should be smooth and without wrinkles.
4. Warm Water
Water at the temperature of 35 to 40.5 degree celcius is necessary to saturate the plaster bandages. The setting time of plaster is also influenced by the temperature of water. Warmer temperature will speed up the setting time. When a large cast is being applied, it may be necessary to change water in between, otherwise excessive sediments of plaster accumulate and begins to adhere to the new rolls of plaster which causes slow setting of the plaster and produces lamination and weakness of the cast.
5. Special Tables (Orthopaedic Tables)
Special tables, called orthopaedic tables are used for the application of the cast. It has devices to support the uncasted area leaving the area on which the cast is applied left free.
6. Other Accessories
If a cast is to be used for bearing client’s weight during ambulation, it is fitted with a walking heel on the plantar surface. It is fitted on the plaster cast in its green stage.
TYPES OF PLASTER CASTS
1. Short Arm Cast (Wrist Plaster)
Short arm casts are applied in the treatment of the fractures of the carpel and metacarpal bones and for the dislocation of the wrist joint. It is extending from below the elbow to the phalanges. The fingers are left free to check the blood circulation and movement in the arm.
2. Long Arm Cast (Above-elbow Plaster)
This is used in the treatment of the fractures of one or both bones of the forearm and dislocation involving the elbow joint. The long arm cast extends from below the shoulder to the phalanges. The elbow joint is kept flexed.
3. Short Leg Cast (Below-knee Plaster)
This is used for the treatment of the fractures of the tarsal and metatarsal bones and for the dislocation, sprains etc. involving the ankle joint. Short leg cast may be either weight bearing or non weight bearing. If it is to be used for bearing a client’s weight during ambulation, it is fitted with a walking heel. The ankle joints are kept at 90 degree angle. The cast is applied from below the knee to the toes. The toes are left exposed.
4. Long Leg Cast (Above-knee Plaster)
This is used in the treatment of the fractures of the bones of the lower leg and thus involving the knee joint. It extends from below the groin to the toes.
5. Spica Cast
Spica cast may be applied to the hip, shoulder and thumb joints. A shoulder spica cast is a combination of a body jacket and a long arm cast. It is used in the treatment of fractures of the shoulder girdle, humerus, dislocation of the shoulder joint etc.
Hip spica extends from the mild trunk just below the nipple line down the entire length of one leg on the affected side. The cast has an opening around the buttocks and perineal region for the purpose of elimination and cleanliness. Hip spica casts are used to treat congenital dislocation of the pelvis, hip joint or fracture of the pelvic bones and femur. Shoulder or hip spica casts may be reinforced by plastering a stick or bar between the extended portions of the cast.
6. Body Casts
Two types of body casts are used – Minerva jacket and body jacket. A Minerva jacket covers the frontal and occipital regions of the skull and extends over the neck, chest, back, abdomen and iliac crests. The face, ears and upper extremities are exposed.
Body jacket extends from the upper chest to the pubis, exposing buttocks and perineal area. Some of the body casts include thighs.
Both Minerva casts and body jackets are used to immobilize the spine to promote healing of surgical spinal fusions, spinal injuries or to relieve degenerative disorders. Body casts may be used to immobilize the spine in a position of hyperextension to treat compression fractures.
Body casts, if applied too tightly over the chest and abdomen 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 is complete.
7. Bivalved Casts
Bivalved a cast means splitting it along both sides. A cast may be bivalved for the following purpose:
To allow space for tissue swelling when it is expected in an area.
To treat a surgical wound
To prevent uncomfortable abdominal distension
To facilitate skin care when skin damage is expected without disturbing the body alignment
To make a half cast which can be used as an intermittent splint to prevent deformities
To help the client to adjust gradually without a body cast
The top half is removed while the client lies supine and remains in the bottom half of the cast and vice versa. When reapplying the bivalved cast, be certain to handle the client carefully and take care not to pinch the skin between the two halves.
COMPLICATIONS OF PLASTER CASTS
Complications
1. Impaired blood flow
Signs and Symptoms: absence of pulse in the extremity below the plaster cast, Pallor, blanching or cyanosis of the skin, Pain, coldness of the skin, Swelling, Numbness, Motor paralysis.
2. Nerve damage
Signs and Symptoms: persistent and increasing pain, Numbness and Motor paralysis.
3. Tissue necrosis and infections
Signs and Symptoms: unpleasant odour, Feeling of ‘hot’ sensations, Drainage through the cast, Sudden elevation of unexplained body temperature.
4. Volkman’s ischaemic contracture
Signs and Symptoms: all the signs and symptoms of impaired blood flow. Absence of radial/pedal pulse, Infarction and necrosis of the muscles, Absence of finger/toe movement, Absence of pain which was intense in the beginning.
5. Cast Syndrome
Signs and Symptoms: prolonged nausea and vomiting. Abdominal distension, Vague abdominal pain.
6. Complications due to immobility
Signs and Symptoms: hypostatic pneumonia, foot drop, renal calculi, decubitus ulcer on all pressure points, stiffness of joints, constipation and retention of urine, lethargy, loneliness and depression, insomnia.
7. Surgical complications
Signs and Symptoms: phlebo-thrombosis and pulmonary embolism, wound infection.