Definition & Overview
The application of casts is a key part of treatment for broken bones or fractures. Casts help promote proper bone healing during the recovery period. They work by keeping the injured part of the body straight and without motion. Casts come in different types, such as short leg casts, patellar tendon bearing casts, and rigid total contact leg casts, among others. To prevent potential complications, casts should be worn only for the correct amount of time, which depends on the severity of the injury.
Who Should Undergo and Expected Results
The application of short leg, patellar tendon bearing, and rigid total contact leg casts is helpful for patients recovering from musculoskeletal conditions, such as:
- Reduced joint dislocations
- Severe soft tissue injuries
They can be used on almost any body part, including the arms, legs, elbows, ankles, and even the fingers.
Casts keep bones from moving while they are healing and support the injured limb during the recovery period. They also stabilise reduced, displaced, or unstable fractures before the patient seeks further treatment.
Using casts offers the following benefits:
- Promote proper healing
- Keep the injured limb from unnecessary stress
- Shorten the patient’s recovery time
- Help reduce pain and swelling
Casts are made of either plaster of Paris or fibreglass. Fibreglass is a type of mouldable plastic used to make cooler and more lightweight casts than the traditionally used plaster casts.
Casts come in many different types, including:
Short leg casts. These are appropriate for patients who suffer from lower leg, ankle, and foot injuries, such as non-displaced metatarsal or fibular fractures. The cast is applied at the metatarsal heads until 2 inches away from the fibular head. The bony parts, such as the fibular head and malleoli, are covered with additional padding. If it is the ankle, it is flexed to a neutral 90-degree position.
Patellar tendon bearing casts. Patellar tendon bearing casts are below-knee total contact casts first developed in 1967. They are appropriate for injuries affecting the patellar and its soft tissues, such as patellar fracture, patellar dislocation, and patellar tendon rupture. They are modified versions of the short leg cast. The top of the cast has a wing-like addition that supports the knee’s medial and lateral side. The back of the cast is then cut in the back to allow the leg to flex at the crease of the patellar. These modifications were made to allow the knee to move but to keep it from rotating and worsening the injury. This cast is used by patients who are ready to begin bearing weight. It is usually worn after coming out of a long leg cast.
Rigid total contact leg casts. A total contact cast is the primary type of cast used for diabetic patients who suffer from foot ulcers. For diabetic patients, it is important to keep the pressure on the foot ulcer low. Studies show that a rigid total contact cast put the lowest peak plantar pressure in ambulatory patients. These casts are ideal for diabetic patients with foot ulcers as long as the patient:
- Is not infected
- Has sufficient arterial flow
- Does not have pain or significant oedema
- Has a stable gait
- Does not have safety hazards and compliance issues
- Has Wagner 1 or 2 ulcers
Patients who have an active infection or compromised arterial flow are reconsidered for a total contact cast only if they have received treatment for the infection or have undergone vascular surgery.
The selection of the right cast to use depends on the following factors:
- The body part being treated
- The type of injury
- The extent of the injury
- The stability of the injury
How is the Procedure Performed?
Doctors generally follow the same steps during the application of different casts, which include short leg, patellar tendon bearing, and rigid total contact leg casts.
- The doctor first wraps the injured area with several layers of soft cotton or, in the case of a total contact cast, foam dressing. This makes up the inner layer of the cast. Sometimes, patients are also given a stockinette or a strip of felt.
- The outer layer of the cast, which is made from plaster of Paris or fibreglass, is soaked in water.
- The material is then wrapped around the injured area and the inner layer of the cast. It normally feels wet at first, but the cast will quickly harden.
- The cast is trimmed to the right size.
- Doctors may make tiny cuts on the sides of the cast to accommodate any swelling.
- A rubber or plywood walking heel is attached to the bottom of the patient’s foot.
- After the cast is applied, patients are not allowed to bear any weight for around 15 minutes or until the cast is cool and hard.
There are some special considerations depending on the type of cast being used. For the patellar tendon bearing cast, it should be applied in segments and over minimal padding. During the application, the patient is asked to flex the knee to a right angle. The doctor then moulds the cast over the upper calf. This creates a triangular cross section. The cast is then moulded around the patella with a special indentation around the tendon.
For the application of a rigid total contact leg cast, the patient should be in a prone position, and the leg should be flexed at the knee. The foot should also be in a neutral position with the ankle.
Patients are given instructions on the care of the cast before being discharged.
Possible Risks and Complications
Patients who have a short leg, patellar tendon bearing, or rigid total contact leg cast placed are prone to the following symptoms or complications:
- Chronic pain
- Joint stiffness
- Muscle atrophy
- Heat injury
- Pressure sores
- Skin breakdown
- Complex regional pain syndrome
To avoid such complications, the casts are only worn for a limited amount of time. Patients are also carefully monitored.
Boyd AS, Benjamin HJ, Asplund C. “Splints and casts: Indications and methods.” Am Fam Physician. 2009 Sep 1;80(5): 491-499. http://www.aafp.org/afp/2009/0901/p491.html
H. Svend-Hansen, V. Bremerskov & P. Ostri (1979) Fracture-Suspending Effect of the Patellar-Tendon-Bearing Cast, Acta Orthopaedica Scandinavica, 50:2, 237-239, DOI: 10.3109/17453677908989761