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Patients with classical plaster casts can be seen less and less. In recent years, colorful fiberglass casts and especially orthoses made of composite materials compete with plaster. What is the future of plaster for the immobilization of limbs?
Evolution by the plaster cast
Over 150 years ago, when the Dutch military physician Antonius Mathijsen used for the first time cotton bandages soaked with plaster of Paris to produce an immobilizing cast, this was a huge step forward. Previously splints were used, usually made out of wood. They were held by bandages which were stiffened with glue, starch or wax. These structures were quite unstable, so that the patient could not leave the bed, in order to achieve immobilization of the injured limb. Plaster casts were superior to them in many ways. They are compact, sturdy and not too heavy. In particular, the patients are mobile while the injured limb is immobilized. For the first time, an outpatient treatment of bone fractures was possible. Furthermore, the plaster cast can be applied easily, it is moldable when wet, dries quickly and achieves a good strength. Above all, it is cheap.
Fiberglass as competition to plaster
The very low cost are now the main argument for plaster casts not only in underdeveloped countries but also in countries where the cost increase is limited in the health system. The more expensive fiberglass bandages impregnated with polyurethane that arose in the late 20th century could surpass the already good characteristics of plaster only by a lower weight. In addition, fiberglass bandages are more stable, hardened faster and are resistant to moisture. However, the padding under the slightly air-permeable fiberglass layer should not be wet.
In comparison, the advantages of plaster in addition to price are the unlimited duration of unused bandages and better environmental compatibility of the used cast. In addition, the freshly applied plaster bandages can be more easily molded to make a snug and more comfortable fit. The plaster surface is permeable to air and much smoother, therefore it does not rub the clothing. In response to the colored fibreglass cast colorful bandages can be wrapped on top of the fresh white plaster.
Orthoses for more freedom of movement
Instead of Both types of immobilizing casts, today mainly orthoses are used with ligament injuries. A cylinder cast on the knee after cruciate ligament rupture, a short leg cast after ankle ligament tear or a cast in foot drop position after Achilles tendon rupture are today only used for a short time after surgery. Otherwise knee, ankle or lower-limb orthoses are the tools of choice. Their advantages are in greater flexibility during use. In contrast to the rigid plaster the diffraction angle of a knee brace is adjustable. Similarly with Achilles tendon injuries, the foot drop position which is necessary to relief the tendon can be achieved with an inserted wedge-shaped sole in a lower leg orthesis, called walker.
In addition to such functional advantages of orthoses, they allow more freedom of movement due to their less immobilizing effect. In an advanced healing phase, when the injured area has certain stability again, a moderate exercise is beneficial. It prevents muscular atrophy and the connective tissue surrounding the injured area is better supplied with blood. Also, joints become less stiff.
The emphasis on more mobility is particularly evident in the treatment of ligament injuries of the ankle. While a few years ago, a torn ligament was stitched and the lower leg was immobilized in a plaster cast. Today this is only done, if all three ligaments of the ankle are completely torn. Otherwise, first a splint or a cut cast is applied for a few days until the swelling is reduced. Then it is standard that the ankle is splinted with a brace for six weeks. The ankle brace is a U-splint, which can be worn in a shoe. It stabilizes the joint, the ligaments are lightened and at the same time a horizontal movement of the joint is provided. So walking is possible and the ligaments could grow together.
Orthoses in the treatment of fractures
In the case of bone fractures, orthoses are only useful if the fragments cannot relocate, so usually after an advanced healing. Lower-limb orthoses are most common. They can be used for stable foot, ankle and lower leg fractures. Their advantage over immobilizing casts is that the on and off is possible at any time, for example for wound control or for washing. This can also be a disadvantage if the patient arbitrarily inserts carrying breaks. In addition, they have a walking sole that can tempt to put weight on the injured limb too early.
The cast from the 3D printer
The latest idea comes from New Zealand designer Jake Evill. He has produced a cast in grid structure with a 3D printer. After an X-ray and 3D scan of the injured limb, a special software calculates the exoskeletal cast "Cortex", as he calls his invention, for a perfect fit. Then it is printed with recyclable nylon material. The honeycomb-like structure is extremely light and fully ventilated. A sweating in the cast is passé. The injured part of the body and the surrounded exoskeletal cast can be washed, because no padding is underneath.
But the lack of padding is just the crucial disadvantage. Pressure sores will occur. Especially in places where bones are located directly under the skin and where the exoskeletal cast is stuck together. It is unthinkable as weight-bearing cast on the foot. Furthermore, considerable investment costs for 3D scanners and printers are required to provide individual fitting. But a better fit is not achieved in comparison to immobilizing casts or orthoses. Also, the 3D printing lasts quite a long time. An exoskeletal cast for the forearm takes about three hours.
Conclusion
The previously undefeated argument for plaster is its price-performance ratio. Fiberglass casts can compete with plaster, but could not replace it. Plaster casts have a future in short and medium-long wearing. Especially after a decrease of swelling when the cast needs to be changed soon. Fiberglass casts, also named secondary casts, are used for a long-term wearing. In this case, the lower weight and the robustness are appreciated.
Orthoses can show off with variable settings that are useful especially in the treatment of ligament injuries. Orthoses are not the first choice for fractures where the fragments have to be held in position and an effective immobilization is needed.
A nylon-skeleton out of the 3D printer is currently not suitable as immobilizing cast. On one hand it is light and airy, on the other hand the lack of padding causes pressure sores. Negative are also the high costs of the equipment and a long production time.
So plaster plays still an important role in immobilization as primary cast. In later phases of the treatment orthoses and fiberglass casts are alternatives.
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