A cast is a rigid device used to provide support and protection following injury and surgery and for other musculoskeletal conditions that require immobilisation (Table 8.1). Casts are constructed from flexible bandages impregnated with material which hardens when ‘cured’ following contact with water. The bandage is usually dipped in water, wrapped around the limb or body part and then held in position until the material hardens. This provides a firm support that follows the contours of the area it encases.

A number of materials are used for casting (Table 8.2). Plaster of Paris casts are most often used immediately following injury or surgery as they are relatively cheap and easy to apply. A lighter, more robust, synthetic cast can then be applied for a longer period of time once swelling has subsided. The choice of cast depends on applier preference and the instructions of the consulting surgeon.

Health and safety is an important consideration for both patients and staff whether a cast is applied in a casting room or other area. Employers and staff have a duty to ensure safety through systems that provide:

• training and education in safe cast application
• staff with the correct skills and experience
• appropriate, well-maintained equipment.

Ideally casting should take place in a casting room where specialist facilities are available. Casting materials and equipment should always be used in accordance with the manufacturer’s instructions and there should be a regular and recorded equipment maintenance programme. The application of casts involves the use of substances which might be hazardous to health. Appropriate risk assessment must, therefore, take place. Manufacturers of casting materials have a legal responsibility to provide information and guidance which must be adhered to. Important precautions include:

• Plaster of Paris application and removal results in dust which can be inhaled by patients and staff. Oscillating saws must be fitted with a vacuum and staff and patients should wear a face mask.
• Gloves need to be worn, particularly when applying synthetic materials as the resin can cause irritation.
• The noise produced by the oscillating cast saw is below the required daily exposure limit for personnel. However, it becomes louder on contact with casting materials and ear defenders should be worn if the saw is to be used for prolonged periods of time.

There must be enough staff available to apply casts safely. Ideally, there should be one person to hold and position the patient’s limb and reassure the patient whilst the other applies the cast.

Casting technique

The basic principles of cast application are the same whether applying plaster of Paris or synthetic casts. Casting is a highly skilled and technical activity that requires great manual dexterity. It should only be undertaken by staff with the knowledge and skills required and who practice the skills regularly. Even so, all staff working in orthopaedic and trauma settings should have a working understanding of the principles of cast application.

A good cast should always:

• Be applied in the recommended position – providing the best possible support of the limb.
• Be functional – not restricting joint movement unnecessarily and not restricting movement of joints that are not within the cast.
• Fit well – to provide adequate splintage but not be too tight. Casts that are too tight restrict blood and nerve supply and must be smooth inside without ridges that cause pressure.
• Be ‘just enough’ – sufficient casting material should be applied to achieve the support necessary whilst keeping the cast as light as possible
• Be complete – the cast should not be a succession of layers but should be moulded so that the materials involved are fully bonded together.

Before applying a cast it is essential to:

• check the patient’s details and the written instructions for the cast
• prepare the area to be used and ensure all equipment is ready for use
• provide verbal and written information and gain consent
• provide reassurance and pain relief prior to any casting
• position and support the patient and limb correctly and comfortably
• maintain privacy and dignity
• assess the condition of the patient’s skin
• ensure that jewellery has been removed from the limb to be casted.

Cast application follows general principles:

• Stockinette and appropriate padding is applied that is not excessive, but adequately protects bony prominences and vulnerable skin.
• Casting materials should be applied in accordance with the manufacturer’s instructions for timings and water temperature.
• The casting material should be applied by starting at one end of the area to be covered and each turn of the casting bandage should be approximately one third of the previous turn.
• All the bandages should be applied carefully, but rapidly; smoothing continuously so that the cast layers laminate together.
• The cast should be applied without tension so that it is not too tight or too loose.
• The cast is then moulded to the shape of the area. This should be done with the palm of the hand and not the fingers, which can cause indentations leading to pressure under the cast.
• Once the cast has set, the edges should be trimmed and the stockinette should be folded back and secured with casting material.

Application of a synthetic cast is very similar but with the following exceptions:

• Padding is used but stockinette is not required.
• Extra strips of adhesive padding are applied at ends where the cast will start and terminate so that it can be turned back over the edges of the cast.
• The bandages are rolled out covering half of the previous turn with controlled tension.
• During the final moulding the cast needs to be held in place until set, otherwise the shape will not be held.

Following completion of the cast:

• The patient’s skin should be cleansed and dried.
• Cast edges should be checked and trimmed as necessary to ensure that joints maintain their full range of movement and that edges do not rub the skin. The edges should then be padded and the stockinette secured in place.
• Cast setting depends on the type of cast applied and the patient should be advised how long this will take and instructed to rest the area and not bear weight on the cast during this time. All limbs in casts should be elevated and rested on pillows.
• The cast should be left uncovered for 48 hours to allow it to dry and should be handled as little as possible to prevent denting and cracking.
• Neurovascular assessment should be undertaken for all limb casts (see Chapter 9) and clearly documented.
• Documentation of any assessment, intervention and follow-up must be clear and precise.
• All advice given verbally should also be given in written format to the patient and carer. It should include care of the cast preventing complications and exercise sheets.
• If equipment such as crutches is required, advice and demonstration/practice should be given in writing and verbally on how to use them both. A physiotherapy referral may be advised.

Cast complications

If a cast is poorly or inappropriately applied the patient is at risk of injury and professional and legal action can be taken. A good quality cast is the best way to make sure that complications do not occur. The complications of casts along with mode of recognition and management are listed in Table 8.3. These complications can also be prevented by making sure the patient knows how to seek help immediately if they have any problems at all.

Living with a cast

It is important that practitioners have an understanding of how a patient will cope with life in a cast (Box 8.1). A comprehensive assessment by the multidisciplinary (MDT) team may be required to ensure the patient will be able to manage safely after discharge. This will depend on previous levels of independence, the ability to accept a different level of self-care than before, availability of assistance from others and the practical advice they are given.

Assistance may be required with some activities of daily living including:

• Toileting – a stool to place the leg on if in a long leg cast and a commode and/or hoist if mobility is poor.
• Eating and drinking – food and fluids within easy reach; making sure the patient has their food cut up if their arms are in casts; equipment such as non-slip mats and adapted cutlery.
• Dressing – advice on the best clothing to wear or adaptations to be made such as Velcro fastenings.
• Mobility – assessment of mobility and aids required with instructions for use.
• Sleeping – can be difficult. Extra pillows and bed cradles may help along with short term medication to help re-establish a sleep pattern.
• Socialising – living with a cast can result in significant isolation and additional support is needed in leaving the home such as temporary use of a wheelchair and contact with voluntary organisations to provide transportation.

Box 8.1 Evidence digest

Cast removal, splitting and bi-valving

Casts may be removed or bi-valved at the end of treatment, when a new cast is needed or if there is a problem with the cast or limb causing neurovascular compromise. Every orthopaedic practitioner should be able to safely remove or bi-valve a cast. Bi-valving involves cutting the cast in half along both sides so that one half of the cast can be removed whilst the limb is still supported with the other half. The same process should be used when removing a cast, allowing the bottom half of the cast to be used as a splint while the limb is inspected. The limb can then be carefully lifted out of the cast to remove it.

Casts are bi-valved or removed using either plaster shears or an oscillating plaster saw. Practitioners must receive training and be competent in the use of either piece of equipment. Prior to cutting, the cast should be marked on the medial and lateral sides so that the cutting lines do not pass over any bony prominences or fragile skin.

Before removing a cast it is important to:

• Check the patient’s details and the written instructions for removal.
• Prepare the area and equipment to be used.
• Give verbal information prior to removal to gain the patient’s cooperation and consent.
• Demonstrate the equipment to be used on the patient prior to use to allay anxiety.
• Adequate pain relief must be provided.
• The patient must be positioned comfortably and the part of the body to have the cast removed must be supported in the correct position.
• Privacy and dignity must be maintained at all times.
• The patient’s cast should be carefully assessed prior to removal to ensure the correct equipment is used for cast removal.
• Mark the cutting area medially and laterally avoiding bony prominences.
• Written information must be given to the patient following cast removal.

All types of casts can be removed with plaster shears or an oscillating saw. Synthetic casts require special saw blades made of tungsten.

Plaster shears are blunt, and crush plaster of Paris between two hinged ‘jaws’. The blade of the shears should be passed between the cast and the padding with the hand nearest the cast being kept parallel to the limb and kept still. If the shears are tilted they can dig in or catch the patient’s skin. The other hand is then used to push the shears together to cut through the cast. Once the cast is cut through on both sides it can be opened with the plaster spreaders and the padding cut all the way through with bandage scissors. Shears are often used to remove children’s casts as the oscillating plaster saw may frighten them. Shears are often not effective with synthetic casts.

Plaster saws have an oscillating circular blade which vibrates back and forth at high speed rubbing through the casting material. It must have a vacuum attached to ensure the dust is collected in keeping with health and safety regulations. The blade is held at right angles to the cast and light pressure is applied to make it cut without dragging the saw along the cast. The blade is then removed and reapplied above or below the original cut in an in-and-out motion. The saw must not be used by someone with wet hands and care must be taken as the blade can become hot and burn the skin if:

• a dragging motion is used instead of the in and out motion
• the saw is used continually for a long period of time
• even in normal use the patient may feel the heat through the padding
• if there is a large cast and it is taking a long time to remove it.

The patient’s skin can also be damaged if:

• the cast is bloodstained and the padding and gauze has hardened
• the patient’s skin is taught through swelling
• the blade of the saw is blunt or damaged
• the cast is unpadded as extra care then needs to be taken to avoid damaging the patient’s skin.

The patient’s limb should be placed back in the remaining half of the cast until it has been assessed and permission is given to remove it.

It is important that the patient is warned that their skin will have flaky yellow scales where the upper layers have been unable to shed. The limb will also appear thin and withered as muscles lose their tone from lack of use. The skin should be carefully inspected and assessed and any signs of pressure or soreness should be reported and documented. The patient should be encouraged to wash and dry the area gently and if the skin is very dry, oils or emollient cream can be applied. The skin will be more sensitive to sunlight.

Orthotics, braces, prosthetics and appliances

Orthotics is a specialty that deals with the design, manufacture and supply of orthoses – a general term for splints, appliances and braces. These are externally applied devices that are used to modify the structural or functional characteristics of the neuromuscular and skeletal systems (BAPA 2000). They can be used for acute injuries, chronic conditions and prevention of injury. Prosthetics are devices used to replace either a whole or part of an absent or deficient limb. An orthosis may be used to:

• control, guide or immobilise a limb, joint or body segment
• restrict movement in a given direction
• assist movement and/or posture
• reduce weight-bearing forces for a particular purpose
• assist with rehabilitation following fractures after the removal of a cast
• provide easier movement capability or reduce pain by correcting the shape and/or function of the body
• act as part of fixed or balanced traction
• prevent or correct deformity
• prophylactically for athletes in contact sports.

The orthotist is a healthcare professional with a key role in an orthopaedic and trauma multidisciplinary team (Chapter 5). They design and fit a variety of orthoses under prescription from a licensed healthcare provider. Orthotists also provide ongoing support and information to the patient and the carers.

Caring for a patient with an orthosis is very much like caring for a patient in a cast. Patients and carers can be taught to undertake their own skin care and advised how to seek help if there are problems. Advice also needs to be given regarding preventing and recognising neurovascular problems, exercising and mobilising safely using the orthosis or prosthesis to prevent joint stiffness and swelling. Verbal and written information and advice on how to care for the orthosis and how to recognise complications must be given to both patients and carers. Adjustments to any orthosis should only be undertaken by staff who have the knowledge and skills required. The complications that can occur for patients with an orthosis are related to poorly fitted devices and are similar to those experienced with casts.

External fixation and pin site care

External fixation is a powerful surgical technique, which involves the use of pins and tensioned wires attached to an external scaffolding framework to hold bones in place. The types of frames used in limb reconstruction correct deformity in children and adults, stabilise high-energy fractures in near-fatal trauma and grow bone lost due to trauma or bone tumours where the only other alternative is amputation.

Stabilisation of fractures using external fixation has been in use for thousands of years and mummified remains of humans with long bone fractures with external splintage have been found. It evolved in the 1950s to include deformity correction following the work of Gavril Abramovich Ilizarov (1921–1992) who first used circular frames with threaded rods and wires to help postwar amputees to overcome flexion contractures. One such patient had an undiagnosed fracture. Rather than distracting the contracture itself, distraction occurred at the fracture site. Subsequent X-rays showed bone formation in the gap. This was termed distraction osteogenesis, a previously unknown phenomenon. Bone actively forms in the endosteum, periosteum and bone marrow when compression and distraction is applied in the presence of stable external fixation. Connective tissue only forms bone by distraction osteogenesis; this is the process by which fibroblasts lay down type 1 collagen, orientated along the line of tension. The tension is supplied through the external fixator gradually distracting the bone ends, normally at a rate of 1mm per day, Osteoblasts then invade the periphery and start laying down bone in columns.

Types of fixator

Many types of external fixator now exist, but they generally fall into two categories: monolateral and circular. Figures 8.1 and 8.2 illustrate just two of many different types of frames. ‘Hybrid’ fixators are a combination of both circular and monolateral fixators. Monolateral fixators are biomechanically less stable than circular fixators.

Monolateral fixators (e.g. Figure 8.1) are usually modular devices used to stabilise a fracture. They enable the surgeon to build their own frame and position half-pins away from any soft tissue injury. Some monolateral fixators can also be used for deformity correction; these usually involve a rail system. Often used for femoral lengthening, they are arguably more comfortable for the patient than a circular fixator, but may not allow early weight bearing.

Circular external fixators (see for example Figure 8.2) are used for both fracture stabilisation and deformity correction. They can be used to correct:

• angulation
• rotation
• translation
• limb length discrepancy.

The circular frame is easily adjustable. Adding load, through early weight bearing to the already tensioned wires, stiffens the frame. Weight bearing increases blood flow to the limb and promotes healing. There are two main types of circular fixator: the Ilizarov and the hexapod. The Ilizarov has straight rods and hinges. The patient or their carer adjusts the fixator (usually with a set of spanners) in four increments per day of 0.25 mm. Hexapods are based on the Gough Stuart platform which is also used in industry, for example in parallel robotics and aircraft simulators. Six telescopic struts are adjusted once daily according to a computer calculated prescription. Depending on the manufacturer of the fixator, it may be single or multi-use. The practitioner should establish if the equipment can be re-used and should the patient be transferred to another hospital, or in the case of death, it is important to ensure its return, as lost or mislaid equipment can lead to considerable financial loss (Timms et al., 2010).

Biomechanics

The biomechanical properties of the frame in addition to its fixation to the bone are important to the success of the treatment. A frame which is either unstable or too stiff can lead to non-union. The skill of the surgeon is of prime importance as poor application of the fixator will lead to failure of the treatment. The fixator can also become unstable due to failure of the hardware. Components of the fixator, wires and half pins may occasionally loosen or break. Pin loosening and pin site infections are known to be related (Saithna 2010). An unstable fixator needs urgent review. If the wire or pin breaks at the interface between the wire and the fixator, it may be possible to ‘re-fix’ the wire. If the wire breaks at the interface with the bone, it will need to be removed and, depending on the stage of treatment, the patient may need further surgery to replace the broken wire or pin. The patient may describe:

• hearing the metal break
• the pin site may have become increasingly painful
• the wire may move freely depending upon where it has broken
• the fixator may feel unstable.

It is important to inform the surgeon of this as one broken wire affects the overall fixator stability which may lead to further wire or pin breakage and a failure of the fixator.

Complications

Pain

Pain is an anticipated result of limb reconstruction and patients should be prepared to deal with some degree of discomfort, particularly in the early stages. Modern analgesic drugs allow much more control of pain and offer several alternatives if a particular drug is found to be unsuitable.

Pin site infection

This is arguably the second most likely complication after pain (Patterson 2006) and should take up a large part of pre-operative counselling. Teaching patients to recognise the signs and symptoms of infection is essential as following discharge from hospital it is unlikely that the patient will see a health professional daily. It is important to explain that should infection occur it is not a failing on the patient’s or clinician’s part; rather a common outcome of having metal work penetrating the protective barrier of the skin for prolonged periods of time (see pin site care below).

Joint stiffness

Prolonged periods of immobility will lead to joint stiffness. Patients should be encouraged, with physiotherapist support, to mobilise and exercise joints not constrained by the frame. In some cases the frame will span a joint – most commonly the knee or ankle – because of the fracture site and it is important to inform the patient that following frame removal a great deal of work will be necessary to regain joint function. Managing expectations is very important as the joint in question may never be as flexible as it was pre-injury.

Swelling

The majority of patients will experience some swelling during the treatment. This is partly a natural biophysical reaction to the presence of metalwork within the body. With lower limb frames, most commonly the swelling is due to the loss of the ‘pumping action’ supplied by the calf muscles when mobilising. Weight bearing through the affected limb can help reduce this. In some circumstances the limb may swell to a degree that the rings are in contact with the skin and steps must be taken to protect the area from pressure damage.

Nerve and blood vessel injury

A complication of any orthopaedic surgery and where the insertion of a particular wire or pin proves to be a problem, it may be necessary to remove and possibly re-site this.

Compartment syndrome

Because frame surgery is often minimally invasive, compartment syndrome is rare. However the same neurovascular assessments should be undertaken throughout treatment and the immediate post-operative period with frame surgery as any other orthopaedic procedure (Chapter 9). Some of the temporary, monolateral fixators are applied following high impact trauma where risk is greatly increased.

Venousthromoboembolism

Any procedure which limits mobility and function puts the patient at risk of VTE (Chapter 9). Pre-operative preparation gives the clinician the opportunity to advise the patient on the signs and symptoms to look out for.

Re-fracture

Although X-rays may look adequate and the patient is reporting positively, a frame is sometimes removed too early. This can result in re-fracture. This will present in a gradual ‘bend’ at the fracture/regenerate site and increased pain. This is why may surgeons are now opting to remove the interlocking struts for a couple of weeks prior to complete removal, if bending occurs the struts can be reinserted and the limb can be left to heal for longer. Others will choose to protect the limb in a cast or orthotic for a few weeks preceding removal. It is considered preferable to remove the frame late rather than too early.

Nursing care

Nursing care for patients with frames can be time-intensive and both physically and emotionally draining for both the patient and carers. Pre-operative counselling improves patient understanding and acceptance, but in cases of new trauma this is not an option. Those with chronic injuries may be facing the decision of having a frame fitted or amputation, raising a discussion about when to abandon limb salvage treatment and offer amputation. This involves intense psychological support, especially given that the patient may have many months or years of treatment in a frame for it to then fail, with the end result being amputation. Therefore, it is worth bearing in mind the work of the Lower Extremity Assessment Project (LEAP) (MacKenzie and Bosse 2006), demonstrating the importance of managing patients’ expectations. Patients should be made aware that following severe trauma, function of the affected limb may never return to its pre-injury state.

Box 8.2 Evidence summary