Orthopedic cast

Overview
An orthopedic cast is a shell, frequently made from plaster, encasing a limb (or, in some cases, large portions of the body) to hold a broken bone (or bones) in place until it has healed.

Plaster bandages consist of a cotton bandage that has been impregnated with plaster of paris, which hardens after it has been made wet. Plaster of Paris is calcined Gypsum, ground to a fine powder by milling. When water is added, the more soluble form of calcium sulphate returns to the relatively insoluble form, and heat is produced.


 * 2(CaSO4.½ H2O) + 3H2O → 2(CaSO4.2H2O) + Heat

The setting of unmodified plaster starts about 10 minutes after mixing and is complete in about 45 minutes, the cast is not fully dry though for 72 hours.

Nowadays fiberglass bandages are often used. These consist of a knitted fiberglass bandage impregnated with polyurethane. These are lighter and dry much faster than plaster bandages. However, plaster can be more easily moulded to make a snug and therefore more comfortable fit. In addition, plaster is much smoother and does not snag clothing or abrade the skin. Plaster casts are generally made available only to patients who insist on them, because they take more time to apply, or when the cost of the fiberglass material is a consideration.

History
The earliest methods of holding a reduced fracture involved using splints. These are rigid strips laid parallel to each other alongside the bone. The Ancient Egyptians used wooden splints made of bark wrapped in linen. They also used stiff bandages for support that were probably derived from embalming techniques. The use of Plaster of Paris to cover walls is evident, but it seems it was never used for bandages. Ancient Hindus treated fractures with bamboo splints, and the writings of Hippocrates discuss management of fractures in some detail, recommending wooden splints plus exercise to prevent muscle atrophy during the immobilization. The ancient Greeks also used waxes and resins to create stiffened bandages and the Roman Celsus, writing in AD 30, describes how to use splints and bandages stiffened with starch. Arabian doctors used lime derived from sea shells and albumen from egg whites to stiffen bandages. The Italian School of Salerno in the twelfth century recommended bandages hardened with a flour and egg mixture as did Medieval European bonesetters, who used casts made of egg white, flour, and animal fat. By the sixteenth century the famous French surgeon Ambroise Paré; (1517-1590), who championed more humane treatments in medicine and promoted the use of artificial limbs made casts of wax, cardboard, cloth, and parchment that hardened as they dried.

These methods all had merit, but the standard method for the healing of fractures however was bed rest and restriction of activity. The search for a simpler less time consuming method lead to the development of the first modern occlusive dressings, stiffened at first with starch and later with plaster-of-paris. The ambulatory treatment of fractures was the direct result of these innovations. The innovation of the modern cast can be traced to, among others, four Military surgeons, Dominique Jean Larrey, Louis Seutin, Antonius Mathijsen, and Nikolai Ivanovich Pirogov.

Dominique Jean Larrey(1768 - 1842) was born in a small town in southern France. He first studied medicine with his uncle, a surgeon in Toulouse. After a short tour of duty as a naval surgeon, he returned to Paris, where he was became caught up in the turmoil of the Revolution, being present at the storming of the Bastille. From then on, he made his career as a surgeon in France's revolutionary and Napoleonic armies, which he accompanied throughout Europe and the Middle East. Larrey as a result accumulated a vast experience in military medicine and surgery.

Among his patients after the battle of Borodino in 1812, was an infantry officer whose arm had to be amputated at the shoulder. The patient was evacuated immediately following the operation and passed from Russia, through Poland and Germany. On his arrival at his home in France the dressing was removed and the wound found to be healed. Larrey concluded that the fact that the wound had been undisturbed had facilitated healing. After the war, Larrey began stiffening bandages using camphorated alcohol,  lead acetate and egg whites beaten in water.

An improved method was introduced by Louis Seutin, (1793 - 1865) of Brussels. In 1835 Seutin had served in the allied armies in the war against Napoleon and was on the field of waterloo. At the time of development of his bandage he was chief surgeon in the Belgium army. Seutin’s “bandage amidonnee” consisted of cardboard splints and bandages soaked in a solution of starch and applied wet. These dressings required 2 to 3 days to dry, depending on the temperature and humidity of the surroundings. The substitution of Dextrin, a product of starch hydrolysis, for starch, advocated by Velpeau, the man widely regarded as the leading French surgeon at the beginning of the 19th century, reduced the drying time to 6 hours, a vast improvement, but still a long time especially in the harsh environment of the battlefield. A good description of Seutin’s technique was provided by Samson Gamgee who learned it from Seutin in France during the winter of 1851-52 and went on to promote its use in Britain. The limb was initially wrapped in wool, especially over any bony prominences. Pasteboard was then cut into shape to provide a splint and dampened down in order that it could be moulded to the limb. The limb was then wrapped in bandages before a starch coating was applied to the outer surface. Suetin’s technique for the application of the starch apparatus formed the basis of the technique used with plaster of Paris dressings today. The use of this method led to the early mobilization of patients with fractures and a marked reduction in hospital time required.

Although these bandages were an improvement over Larrey’s method, they were far from ideal. They required a long time to apply and dry and there was often shrinkage and distortion. A great deal of interest had been aroused in Europe around 1800 by a British diplomat, who described a method of treating fractures that he had observed in turkey. He noted that Gypsum (plaster of paris) was moulded around the patient’s leg to cause immobilization. If the cast became loose due to a reduction in swelling, then liquid gypsum was poured into a hole to fill the space. Adapting the use of plaster of Paris however for use in hospitals took some time. In 1828, doctors in Berlin were treating leg fractures by aligning the bones in a long narrow box which was then filled with moist sand. The substitution of Plaster of Paris for the sand was the next logical step. Such plaster casts did not succeed however as the patient was confined to bed due to the casts being heavy and cumbersome.

Plaster of Paris bandages were introduced in different forms by 2 army surgeons, one at a peacetime home station and another on active service at the front. Antonius Mathijsen (1805 - 1878) was born in Budel, the Netherlands, where his father was the village doctor. He was educated in Brussels, Maastricht and Utrecht obtaining the degree of doctor of medicine at Gissen in 1837. He spent his entire career as a medical officer in the Dutch Army. While he was stationed at Haarlem in 1851, he developed a method of applying Plaster of Paris bandages. A brief note describing his method was published on January 30 1852; it was followed shortly by more complete accounts. In these accounts Mathijsen emphasised that only simple materials were required and the bandage could be quickly applied without assistance. The bandages hardened rapidly, provided an exact fit and could be windowed or bivalved easily. Mathijsen used coarsely woven materials, usually linen, into which dry Plaster of Paris had been rubbed thoroughly. The bandages were then moistened with a wet sponge or brush as they were applied and rubbed by hand until they hardened.

Plaster of Paris dressings were first employed in the treatment of mass casualties in the 1850's during the Crimean War by Nikolai Ivanovich Pirogov (1810-1881). Pirogov was born in Moscow and received his early education there. After obtaining a medical degree at Dorpat he studied at Berlin and Gottingen before returning to Dorpat as a professor of Surgery. In 1840, he became the professor of surgery at the Academy of military medicine in St. Petersburg. Pirogov introduced the use of ether anaesthesia into Russia and made important contributions to the study of cross-sectional human anatomy. With the help of his patron, the grand duchess Helene Pavlovna, he introduced female nurses into the military hospitals at the same time that Florence Nightingale was beginning a similar program in British military hospitals.

Seutin had travelled through Russia demonstrating his Starched Bandage, and his technique had been adopted by both the Russian army and navy by 1837. Pirogov had observed the use of plaster of Paris bandages in the studio of a sculptor who used strips of linen soaked in liquid plaster of Paris for making models. Pirogov went on to develop his own methods, although he was aware of Mathijsen's work. Pirogov's method involved soaking coarse cloth in a plaster of Paris mixture immediately before application to the limbs, which were protected either by stockings or cotton pads. Large dressings were reinforced with pieces of wood.

As time passed and the method moved more into the main stream some disagreement arose as to the problems associated with cutting off air to skin contact, and also some improvements were made. Eventually Pirogov's method gave way to Mahjisens. Among the improvements suggested as early as 1860 was that of making the dressing resistant to water by painting the dried plaster of Paris with a mixture of shellac dissolved in alcohol. The first commercial bandages were not produced until 1931 in Germany, and were called Cellona. Before that the bandages were made by hand at the hospitals.

As a plaster cast is applied, itexpands by approximately ½ %. The less water is used, the more linear expansion occurs. Potassium Sulphate can be used as an accelerator and sodium borate as a retarder in order that the plaster can be caused to set more quickly or slowly.

Limitations of Plaster casts
Due to the nature of the dressing in that the limb is unreachable during treatment; the skin under the plaster becomes dry and scaly because the discarded epithelium (skin cells) is not washed off. Also, plaster of Paris casts can result in cutaneous complications including macerations, ulcerations, infections, rashes, itching, burns, and allergic contact dermatitis, which may also be due to the presence of formaldehyde within the plaster bandages. In hot weather, staphylococcal infection of the hair follicles and sweat glands can lead to severe and painful dermatitis.

Other limitations of Plaster Casts include their weight which can be quite considerable, thus restricting movement, especially of a child and their opacity to X-rays. As such the only way to check that the bone is healing is to remove the cast. Removal of the cast can only be done by destroying the cast itself. The process is often noisy making use of a circular saw to cut through the tough plaster shell. Although the removal is painless, this can be distressing for the patient, especially children. Additionally, plaster of Paris casts break down if patients get them wet.

Due to the limitations of plaster-of-paris surgeons have also experimented with other types of materials for use as splints. An early plastic like material was Gutta-Percha obtained from the latex of trees found in Malaya. It resembled rubber, but contained more resins. When dry it was hard and inelastic, but when warmed it became soft and malleable. In 1851 Utterhoeven, described the use of splints made from this material for the treatment of fractures. In the 1970s, the development of fibreglass casting tape made it possible to produce a cast that was lighter and more durable than the traditional plaster cast and also resistant to water (although the bandages underneath were not) allowing the patient to be more active.

In 1990s the introduction of new cast lining products such as PROCEL from W. L. Gore & Associates has meant that fiberglass casts with this liner are completely waterproof, allowing patients to bathe, shower, and swim while wearing a cast. The waterproof cast liner however adds approximately 2 to 3 more minutes to the application time of the cast and increases the cost of the cast. Drying time, however, can be inconvenient enough to warrant a cast and bandage moisture protector. These waterproof covers, like SEAL-TIGHT from Brown Medical Industries, allow for bathing and showering while wearing either a plaster or fiberglass cast.

Upper Extremity Casts
Upper Extremity Casts are those which encase the arm, wrist, and/or hand. A long arm cast encases the arm from the hand to the elbow, leaving the fingers and thumbs free. A short arm cast, in contrast, stops just below the elbow. Both varieties may, depending on the injury and the doctor's decision, include one or more fingers or the thumb, in which case it is called a finger spica or thumb spica cast.

Lower Extremity Casts
Lower Extremity Casts are classified similarly, with a cast encasing both the foot and the leg to the hip being called a long leg cast, while one covering only the foot and the lower leg is called a short leg cast. A walking heel may be applied, or a canvas or leather cast shoe provided to the patient who is expected to walk on the immobilized limb during convelescence (referred to as being weight bearing). Where the patient is not to walk on the injured limb, crutches or a wheelchair may be provided. The sole of a leg cast may also be extended to the tip of the toes, if providing a toeplate. This addition may be made to offer support to and stabilize the metatarsals and to protect the toes from additional trauma. Toeplates are infrequently used in the USA, and are more common in continental Europe.

Cylinder cast
In some cases, a cast may include the upper and lower arm and the elbow, but leaves the wrist and hand free, or the upper and lower leg and the knee, leaving the foot and ankle free. Such a cast may be called a cylinder cast, or may simply be called a long arm or long leg cast.

Body casts
Body casts, which cover the trunk of the body, and in some cases the neck up to or including the head (see Minerva Cast, below) or one or more limbs, are rarely used today, and are most commonly used in the cases of small children, which cannot be trusted to comply with a brace, or in cases of radical surgery to repair an injury or other defect. A body cast which encases the trunk (with "straps" over the shoulders), is usually referred to as a body jacket.

Spica cast
A cast which includes the trunk of the body and one or more limbs is called a spica cast, just as a cast which includes the "trunk" of the arm and one or more fingers or the thumb is. For example, a shoulder spica includes the trunk of the body and one arm, usually to the wrist or hand. Shoulder spicas are almost never seen today, having been replaced with specialized splints and slings which allow early mobility of the injury so as to avoid joint stiffness after healing.

A hip spica includes the trunk of the body and one or more legs. A hip spica which covers only one leg to the ankle or foot may be referred to as a single hip spica, while one which covers both legs is called a double hip spica. A one-and-a-half hip spica encases one leg to the ankle or foot and the other to just above the knee. The extent to which the hip spica covers the trunk depends greatly on the injury and the surgeon; the spica may extend only to the navel, allowing mobility of the spine and the possibility of walking with the aid of crutches, or may extend to the rib cage or even to the armpits in some rare cases. Hip spicas were formerly common in reducing femoral fractures, but today are rarely used except for congenital hip dislocations, and then mostly while the child is still an infant.

In some cases, a hip spica may only extend down one or more legs to above the knee. Such casts, called pantaloon casts, are occasionally seen to immobilize an injured lumbar spine or pelvis, in which case the trunk portion of the cast usually extends to the armpits.

Other casts
Other body casts which were used in decades past to protect an injured spine or as part of the treatment for a spinal deformity (see scoliosis) which are rarely seen today include the Minerva cast and Risser cast. The Minerva cast includes the trunk of the body (sometimes extending down only so far as the rib cage) as well as the patient's head, with openings provided for the patient's face, ears, and usually the top of the head and hair. The Risser cast was similar, extending from the patient's hips to the neck and sometimes including part of the head. Both of these casts could, with care and the doctor's permission, be walked in during convalescence. However, in some cases the Risser cast would extend into one or more pantaloons, in which case mobility was far more restricted.

Aside from the above common forms, body casts could come in nearly any size and configuration. For example, from the 1910s to the 1970s, use of a turnbuckle cast, which used metal turnbuckles to twist two halves of the cast so as to forcibly straighten the spine before surgery, was common. The turnbuckle cast had no single configuration, and could be as small as a body jacket split in half, or could include the head, one or both legs to the knees or feet, and/or one arm to the elbow or wrist depending on the choice of the doctor.

Despite the large size and extreme immobilization some casts, particularly those used in or before the 1970s, the popular term full body cast is something of a misnomer. The popular and media-driven conception of a massive cast encasing all four limbs, the trunk, and the head - sometimes leaving only small slits for the eyes, nose, and mouth - is a true rarity in recorded medical history, and this type of large scale cast appears more commonly in throughout various Hollywood movies and on television shows. The term body cast (or full body cast) is sometimes casually used by laymen to describe any of a number of body and or spica casts, from a simple body jacket to a more extensive hip spica.

Care of casts
This section uses the general term ‘cast’ and applies mostly to the care of limb casts. However, the principles and comments apply to both Plaster of Paris and fibreglass casts of all types.

A freshly applied cast should be treated gently until it is fully dried and has developed its full strength. Do not rest a fresh cast on a hard surface or it may become dented or distorted; rest it on a pillow or similar soft surface. Use a triangular sling to support a fresh upper limb cast, rather than a collar-and-cuff sling which will apply localised pressure to the cast.

Keep the casted part elevated as much as practical. This is particularly important in the first few days after injury or the application of a fresh cast. Exercise the fingers or toes through the full range of motion both actively and passively.

A cast should be snug, but not tight. A tight cast, or a cast that becomes tight because of swelling of the casted limb, can interfere with blood circulation in the limb. This can lead to a serious emergency condition similar to compartment syndrome. If the casted limb becomes increasingly painful, the fingers or toes change colour to a dusky or white shade, become cold, lose motion or sensation, or there is increasing pain on passive extension of the digits, seek help immediately, day or night. The only treatment for this condition is to split the cast to relieve the pressure on the limb and enable normal circulation to return.

Do not let the cast get wet, or the skin underneath may become macerated. Do not use implements such as knitting needles or similar to scratch under the cast. This risks injury to the skin, which can then become infected. Seek immediate advice if any article falls into or becomes lodged inside the cast, or a discharge appears on the surface of the cast, or an unpleasant odour becomes apparent.

Comfort in a cast is a relative term, but, taking the underlying injury into account, casts themselves should not be painful. Seek advice if appropriate analgesia is not controlling pain, or if pain increases over time rather than decreases. Note that increasing analgesia in an attempt to manage increasing pain due to a tight cast will not work, and does not address the underlying condition.