A plaster cast is given for treatment of fractures and other orthopedic ailments. Though a very safe mode of treatment, complications of plaster may occur.
Main complications of plaster are stiff joints, muscle wasting, and impaired circulation. Physiotherapy and good nursing can help reduce these complications and speed the final recovery.
Complications of plaster cast can be divided in systemic, which affects whole body or local which affects limb where plaster has been applied.
Local cast complications can be further classified as immediate and delayed.
Systemic Complications of Plaster Cast
The most serious is deep venous thrombosis leading to pulmonary embolism. Pain in the calf is an important sign needing medical advice.
Immobilization in trunk plasters or plaster beds may also produce nausea, abdominal muscle cramps, retention of urine and abdominal distention.
Good nursing and diet with regular exercises will help ensure that the initial period of extensive immobilization is achieved without complications.
A patient might be allergic to the material of cast, the preservatives and other substances in the cast. It is not that common. Allergies are more common with newer synthetic cast materials.
If the limb is allowed to move while the plaster is setting, a ridge forms in the plaster, creating a pressure point on the underlying skin.
Such a ridge commonly forms in the dorsum of the ankle, the popliteal fossa, and the cubital fossa.
Pressure points may be created by denting caused by the operator’s fingers while the cast is being applied. Complaints of pain or burning must be taken seriously, and the cast must be windowed to inspect painful areas.
Rarely, very hot water used to wet the plaster rolls can cause the burn.
A plaster produces constricting effect on the limb and most of it is well tolerated but a moderate constriction will produce compression of the veins, damming the blood, and causing swelling, discomfort or pain, and a blue color in the skin and under the nails.
Swelling is a natural sequel to an acute injury that produces a fracture. If the extremity is placed in a cast too soon after injury, ischemic changes may result from neurovascular compromise.
A freshly fractured extremity may be splinted or placed in traction until swelling subsides.
Casts should be trimmed back to the metatarsophalangeal joints of the foot and the metacarpophalangeal joints of the hand to provide for the inspection of the fingers and toes. This helps for early detection and to detect signs of neurovascular compromise in the extremities.
Temporary remedies such as elevation of the limb and exercising the digits may be tried, but, if persistent, the constriction must be relieved. The cast can be splint and eased or bivalved, taking care not to damage the skin.
Impaired Arterial Supply
A pale skin which is cool and without a palpable pulse indicates that the arterial supply is disrupted. After the pressure on the fingernail, the color does not immediately return. This is a serious complication. Medical advice must be sought immediately.
Splitting the cast may relieve the arterial compression but sometimes surgery may be necessary.
Incomplete arterial occlusion may present with pain or aching with loss of power. If in doubt ask for medical advice.
Pain has many causes. This may be due to tissue damage at injury or reduction, swelling within the cast, muscle spasm, pressure on blood vessels or nerves, skin irritation or sores. Although diagnosis may be difficult, persistent pain or intermittent acute pain should not be ignored. Medical advice must be sought.
The most common cause of sores is the pressure of the plaster on the skin due to poor cast application.
Cast wedging, which is used for correction of angular deformities can cause skin pressure can occur at the level of the wedge.
The patient may report burning, itching or stabbing pain.
Children may have disturbed sleep and elevated temperature.
Signs that may suggest plaster sore
- Heat and swelling of the digits.
- Increased warmth over a localized area of the cast localized odor
- Visible pus or staining of the cast.
The most likely reasons for plaster sore development are:
- The poor technique with adequate padding, or a ridge inside the cast, or failure to trim the ends of the cast correctly.
- Local cast breakdown with skin irritation due to poor care
- Foreign bodies may easily slip between the cast and the skin. Children especially may insert small toys, coins or beads while hairgrips may fall inside the cast.
Patients should be warned of these damages and also to care for the plaster edges since wetting will cause plaster crumbs to be detached and fall inside the cast.
- Scratching at minor irritation beneath the cast with metal implements or knitting needles may cause trauma and infection. Such irritation should be reported and investigated early.
- Plaster soakage leading to skin damage and infection
- Cut edges of plaster following splinting or bivalving or window procedures may irritate the skin especially if swelling occurs around the edge.
Development of plaster sore is very painful. It is a constant nagging pain that does not leave the patient. The patient is often able to pinpoint the sore area. If the patient complains of unrelenting pain or digging sensation the part should be examined.
It should not be ignored at any cost otherwise the results could be disastrous consequences.
A window is cut in the plaster, with an electric cutter. Then underlying padding and lining is removed to inspect the skin.
The skin is examined for any redness or wound.
Grades of Sore
Sores are graded according to the depth of the involvement.
- Grade I-Redness of skin
- Grade II-Involvement of Subcutaneous Tissue or cellulitis
- Grade III- Involvement of Muscles
- Grade IV- Bone Deep
The treatment of sore depends upon the grade. While grade I only require removal of offending pressure others require treatment that varies from simple dressings to surgical debridement and reconstructive procedures.
Apart from immediate complications and plaster sores, there are many other problems that can arise with plaster application.
Loss of Reduction
Because swelling occurs with most fractures especially after reduction, the technician puts padding under the cast to protect the skin. This padding gets compressed. After 48 hours when the edema is subsiding, the cast may be too loose to hold the bone ends in position against undesirable muscle action.
Such displacement may be sudden and cause pain or gradual being first noticed on the next x-ray. This complication may seriously delay sound healing and may produce permanent deformity.
Medical advice must be sought if the position is suspect.
If the limb is not properly held during the casting procedure, it could also be responsible for malpositioning.
Loss of power, tingling, and numbness distal to the cast are signs of impaired nerve function. The cause may be direct compression by bone ends or plaster pressure, indirect compression of oedematous tissue or tourniquet effect, or reduced blood flow.
Routine testing of power and sensation will detect any defect quickly. Corrective action includes relieving cast pressure, supporting and protecting paralyzed parts, and physiotherapy to help restore normal function of muscle and joints.
Breaking of the Cast
Breaking and softening of the cast occur due to many reasons
- Cast gets wet [in case of POP casts. This is one of the complications of plaster of Paris cast, newer materials are water impervious]
- Persistent pressure on a particular area such as the foot or heel
- The patient fails to take proper care of the cast [for example in children, noncompliant patients or elderly patients]
- Fall on the casted extremity
- Self-repair attempts by patients
In case the break is noticed in the cast, the patient must contact the physician for repair or replacement of the cast.
Complications of Special Plaster Casts
Body casts are not used as frequently now as they were used before. The most frequent complication of the cast is that it fails to fit the body and keeps on sliding down.
Due to this movement, pressure necrosis over the sacrum and under the axillae is a common complication.
Gastrointestinal discomfort is manifested by a fleeting sensation of gastrointestinal fullness or persistent discomfort known as “cast syndrome which involves compression of mesentric artery.
Minerva cast is a body cast with an extension that incorporates the cervical spine, and it is used in the treatment of lesions of the cervical spine.
Again, the cast is not used as frequently as before due to better surgical care and custom orthoses.
Pressure areas occur over the sacrum, coccyx, and iliac crests and around the axillae.
Paresthesia in the area of the axillae may occur.
Loss of alignment occurs over the fracture site when the cast slips down or when the patient attempts rotational movements of the neck.
Shoulder spica cast is essentially a body cast with the inclusion of an upper extremity.
Hanging cast is used to treat fractures of the humerus.
If the cast is very heavy, a distraction of fragments may occur.
The hanging cast is ineffective if the patient is allowed to lie flat in bed. The patient must be instructed to maintain a sitting position while sleeping.
in an obese patient, a hanging cast may cause skin problems changes can occur in the axilla.
Long arm cast extends from the base of the metacarpals almost to the axilla. Pressure areas can occur at the base of the thumb or in the cubital fossa. Cubital fossa pressure may occur when the POP cast is applied in two parts.
Sometimes the patient put some objects under the cast, mostly to relieve the itch. Patients must be forewarned about this and instructed not to do this.
Short arm cast extends from the elbow to heads of metacarpals and is prone to slide if the wrist is in the neutral position.
Hip Spica Cast
The hip spica cast is used in the treatment of injuries of the femur, hip, and pelvis and includes opposite leg to a variable extent.
Sacrum, coccyx, trochanters, popliteal and calf regions are prone to pressure changes.
The patient may be turned from side to side and from supine to prone to prevent pressure sores.
Hypercalcemia can develop in patients with Paget disease or metastatic disease during prolonged immobilization.
These are long leg casts and short leg casts.
The long leg cast is used to treat many injuries by immobilizing in plaster the entire lower extremity from the ankle to the thigh.
Long leg cast is prone to breakage at the thigh and at the foot-ankle junction.
Pressure areas are common over the heel. Burning pain in the heel should be investigated; the heel of the cast should be windowed and the skin examined. If there is evidence of only minor irritation, the plaster patch should be replaced and sealed with adhesive tape or plaster. If the window is allowed to remain open, the area swells (ie, window edema), and pressure necrosis occurs around the edges of the window
In a patient with a short leg cast, which extends from below the knee to ball toes, the cast can impinge on the thigh on flexion of the knee.
The cast wears and softens when the patient repeatedly rests the cast on the floor with the weight of the leg pressing on the heel.
Pressure changes may occur on the skin over the patella and head of the fibula.
Pressure on the head of the fibula, if persistent may result in peroneal nerve damage.
In conclusion, utmost care from applying person and the patient is required to avoid any complication of the plaster cast.
How to Avoid the Complications of Plaster Cast
Plaster cast complications can be reduced by taking all precautions of application of the cast, keep a vigilant eye and making sure that patient is well instructed about the care of cast.
- Application of the plaster cast should be done by a skilled person in the proper manner
- Patient, as a routine, should always be called for follow up examination next day.
- Strict elevation of the limb should be instructed.
- The patient should report on every pain that is not relieved, swelling, bluishness or pallor of the distal part.
- The patient should be carefully examined in the follow up for probable complications of plaster cast
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