casting and splinting principles and common pitfalls

Casting and Splinting

Principles and Common

Pitfalls

Muhammad AbdelghaniQGH Instructional Lectures

22 Aug 2016

“With the advent of rigid internal plate and

intramedullary rod fixation, the technique of cast

immobilization has become a lost art for many young

orthopaedists.”

Halanski M, Noonan KJ: Cast and Splint Immobilization: Complications. J Am Acad

Orthop Surg 2008;16:30-40

Today, casts are routinely applied by midlevel orthopaedic providers (ie, cast room technicians, physician assistants), thus further decreasing the

amount of training orthopaedic residents receive in casting. Despite these limitations in training and

exposure, cast immobilization remains a mainstay of treatment for many orthopaedic conditions.

Halanski M, Noonan KJ: Cast and Splint Immobilization: Complications. J Am Acad Orthop Surg 2008;16:30-40

Know Your Materials

• Plaster of Paris (POP)• Synthetically based

fiberglass

POP

• The time-tested form of immobilization.

• Hemihydrated calcium sulfate

• First described in 1852

POP

• Advantages:– Less expensive – More moldable than synthetic

counterparts– More pliable

• Can be effectively spread after the cast is univalved

POP

• Disadvantages:– Poor resistance to water– Relatively low strength-to-

weight ratio• Heavier (thicker) casts

POP

• Associated Exothermic Reaction:– The conversion of POP to gypsum during setting up is an

exothermic reaction.• Faster-setting plasters produce more heat.

Synthetic Fiberglass Materials• Advantages:

– Lightweight, yet strong– May be combined with

waterproof liners to allow bathing and swimming in the cast.

– Often more radiolucent than plaster

• Better imaging within the cast. – Lower risk of thermal injury:

• Less material is required • Very low amount of thermal energy

is released during the curing process.

Synthetic Fiberglass Materials

• Disadvantages:– More expensive.– More difficult to mold

• More stiff

– Higher risk of pressure on and constriction of the limb.

– Carcinogenic risk (??)

Padding

• Simple cotton – The cheapest – The most commonly used – Can be applied under both plaster and

fiberglass cast material.

• Synthetic materials• Newer waterproof liners and padding

– Much more expensive– Variable water resistance

Casting over a Wound

• Never dress the wound with circumferential cotton fiber gauze. – Cotton fibers absorb blood, which hardens and may

become constrictive around the limb as edema increases.

Selecting the Appropriate Cast Material

• Considerations:– Goals and anticipated duration of immobilization– Patient and financial factors

Selecting the Appropriate Cast Material

• When to Use POP:– When a well-molded cast is crucial to maintain reduction

• Acute paediatric forearm fractures that requires closed reduction and immobilization

• Clubfoot – The immobilized limb is small– Maintaining position is essential– Life span of each cast is short.

– In the busy nonsurgical fracture clinic• Many casts are regularly applied• Plaster might be chosen for both its increased pliability and its lower cost.

Selecting the Appropriate Cast Material

• When to Choose Fiberglass:– When cast immobilization is used simply to offer

support and hold a limb in an anatomic position• e.g. in stable minimally displaced fractures.

– For postoperative casting• After the initial postoperative edema has abated. • Advantages:

– High strength-to-weight ratio allows for easier mobilization postoperatively

– Durability is ideal for walking casts

Beware!

• Do not use a fiberglass cast in the acute setting unless the patient will be under close observation in the hospital.

• Never use it in the acute setting on an obtunded patient.

A Well Molded Cast

• Application of a well-molded cast is the key to preventing soft-tissue irritation and loss of fracture reduction.

• Each cast should closely mimic the limb it is immobilizing.

“Well Molded” Does Not Mean Tight!

• A cast that is wrapped too tightly acts like a rigid tourniquet to the extremity.

Avoid Dimpling the Cast

• Areas of increased pressure lead to foci of decreased perfusion, resulting in pressure sores.

• Every assistant should be well trained to hold the limb without producing divots or dimples in the cast.

Avoid Air Pockets

• Avoid air pockets or bubbles in the plaster, which form a stress riser inside the cast and lead to structural failure.

No Direct Contact

• Avoid direct contact between the skin and plaster, which can result in abrasions and lacerations.

Role of Padding• Some try to avoid pressure sores by increasing the amount

of padding under the cast. • This is a misconception!• Excessive padding leads to a cast that is too loose

– This paradoxically increases skin irritation from shear stress at the skin/padding interface.

• The loose-fitting cast can also cause malunion due to loss of fracture reduction.

• Proximal migration of fingers or toes should alert the clinician that there is a problem.

Role of Padding

• Bony prominences and cast edges should be well padded and the cast molded to fit snugly without undue pressure.

Cast Index

• The cross-section of an appropriate forearm plaster should resemble an oval, not a circle.

• For optimal cast fitting in distal forearm fractures treated, the sagittal-to-coronal ratio should be 0.7.

• Well-fitting plasters are important with any immobilized limb.

Don’t Change the Position Once You Finish the Cast

• Don’t change the limb position once the casting material is applied (i.e. during the curing process).

• This will weaken the cast, resulting in increased bunching of casting material and, thus, increased pressure in the flexion crease.

Position of Immobilization

• Unless a pressing reason exists to do otherwise, each joint should be immobilized in the optimal position to retain joint mobility after the cast/splint is removed.

Position of Immobilization• Elbow: 90º of flexion • Wrist: 30º of extension • Thumb: midway between

maximal radial and palmar abduction

• Hand: intrinsic plus (MCP joints in at least 70º of flexion and IP joints in extension)– Position of Safe Immobilization

(POSI)

The HandPosition of Safe Immobilization (POSI)

• A position used to rest the hand during periods of immobilization to minimize/prevent joint stiffness & intrinsic contractures.

• In the early 1960’s, James recognised that the MCP joints recover better from a period of immobilisation when placed in flexion and the IP joints recover better when in extension.

• Since then, extensive research emphasised the importance of this position.

“The MCPJs are safe from contracture in flexion & most unsafe in extension; the PIPJs,

conversely, are safe in extension & exceedingly unsafe if immobilised in flexion”

(James, 1970)

The HandPosition of Safe Immobilization (POSI)

• Wrist: Moderate extension (10-45º)

• MCP joints: Flexion (70-90º) • PIP joints: Neutral

– The exact degrees can vary slightly depending on

• reason for splinting • conditions of the patient’s hand

(e.g. injury, surgery, existing problems)

The HandPosition of Safe Immobilization (POSI)

• MCP Flexion– Collateral ligaments are stretched and

tight– Greater bone surface area contact

causing more joint stability

• MCP Extension – Collateral ligaments are lax and loose– Less bone surface contact causing less

joint stability

“It is well known that the MCP develop an extensor contracture if they are held in

extension for as little as 3 weeks”(James, 1970)

The HandPosition of Safe Immobilization (POSI)

• IP Flexion:– Collateral ligaments are lax and

loose– Fibers between the collateral

ligament and palmar plate contract

• IP Extension – Collateral ligaments are

stretched and tight– Volar plate is maximally

stretched

“It is easier to regain flexion than extension at the PIPJ after a period of

immobilisation” (Hardy, 2004)

The HandPosition of Safe Immobilization (POSI)

• Apply the splint to the volar surface of the hand.• Use your own hands to emphasise and achieve

the position.• If you feel the person’s hand is not in an ideal

intrinsic plus position it is important to correct the position as soon as possible. – Changes to soft tissue can begin after 3 days.

Beware!

• Upper extremity casts extending beyond the metacarpal heads should be avoided because they inhibit finger motion, resulting in stiffness.

“Simple errors in the plaster for a Colles’ fracture which block flexion at the MCP joints, and similar

minor errors give imperfect results in these patient. It cannot be stressed too much how rapidly these

joints stiffen in the dangerous position even in young people, how irreversible the situation is even with active physiotherapy, and how simple are the

mistakes that lead to these difficulties” (James, 1970)

What about the Lower Limb?

• Hip: –10-30º of abduction–20-45º of flexion–15º of external rotation

• Knee: 15-30º of flexion • Ankle: Neutral dorsiflexion

Cast Wedging

• When a fresh fracture (= significant callus formation has not yet occurred) is found to have an unacceptable loss of reduction within the plaster and the cast appears to be well-fitting, cast wedging may be attempted to regain correction.

• Many techniques for cast wedging have been described.

Cast Wedging

Bebbington et al: • A radiograph of the injured area is used to trace the long axis of the

malaligned bone onto a sheet of paper. • The piece of paper is cut along this line, and the cut edge is traced

onto the cast. • The position of the apex of the deformity is determined from the

radiographs.• Next, the plaster is cut nearly circumferentially at this level, leaving a

bridge of intact plaster only at the apex. • Corks or cast wedges are applied opposite this bridge, until the line

transferred onto the cast is straight. • If this fails, the cast may need to be removed and the fracture

remanipulated or treated in some other manner.

Why Common Complications Occur• Improperly and irregularly applied padding → Pressure

sores beneath the cast• Inadequate padding material at the ends of the cast →

sharp edges and skin irritation• Aggressive cast molding → Pressure sores beneath the cast• Inadequate casting material → cast breakdown and loss of

control of the unstable fracture • Tight application of casting material or failure to allow for

underlying injury swelling → Compartment syndrome • Hot dip water → elevated setting temperatures and skin

burns

Beware!

• Avoid ending below-knee casts at the fibular neck.

• This places pressure over this area and are notorious for causing peroneal nerve palsy.

Cast Spreading

• If the cast is too tight, the first intervention should be to relieve circumferential pressure by splitting the cast.

Cast Spreading

• Plaster cast: – Cutting and spreading (univalving) reduce pressure by

40-60% – Release of padding may reduce pressure an additional

10-20%.

Cast Spreading

• Fiberglass cast: – Fiberglass casts have to be bivalved to

see similar decreases in pressure. – In casts applied with the stretch-

relaxation method, univalving may be sufficient as long as the cast can be spread and held open.

– It is wise to use plastic cast wedges to help hold open these split casts.

• Synthetic casts tend to spring back to their original position after simply cutting one side of the cast.

Duration of Immobilization

• Excessive length of immobilization may lead to problems such as joint stiffness, muscle atrophy, cartilage degradation, ligament weakening, and osteoporosis.

• This must be weighed against the bony healing gained in prolonged immobilization.

Thermal Injury

• Contributing Factors: – Speed of reaction– Amount of reactants– Temperature of the system (dip water and/or ambient

temperature): >50°C is too hot– Thicker casts

• Those who are unfamiliar with the amount (ply) of plaster to use may inadvertently use too much, resulting in a burn.

Thermal Injury

• Temperatures high enough to cause significant thermal injury can be reached when the clinician places a curing cast on a pillow.

• Reinforcing a curing plaster cast with fiberglass may place the limb at significant risk.– The synthetic overlap prevents heat from effectively dissipating.

• Wait for the plaster to cure before either setting the casted limb on a support frame or pillow or applying fiberglass reinforcement.

High-Risk Patients

• Patients with an inability to effectively communicate:– Obtunded or

comatose polytrauma patients

• Temporarily place the limb in splint.

• Splint can be removed to inspect limb periodically.

• Such patients are at risk for swelling (fluid shifts, bleeding,..).

High-Risk Patients

• Patients under general or limb block anesthesia (eg, axillary nerve, Bier) – Unable to feel and respond to noxious stimuli (e.g. heat

and pressure) during cast application.

High-Risk Patients

• Very young or developmentally delayed patient– Difficulty to clearly express pain. – Almost any intervention can cause these patients to

become irritable. Thus, discerning a problem may be difficult.

High-Risk Patients

• Patient with impaired sensation– Patients with spinal cord

injury, meningomyelocele, and systemic disorders (eg, DM).

– Vicious Circle:• Prolonged immobilization

→ potentiation of existing osteopenia → increasing risk of insufficiency fracture → further immobilization

• Temporary splint. – Can be removed periodically to inspect

limb.

• Limit the length of immobilization– To combat the cycle of immobilization-

induced osteopenia in the neuropathic patient.

– Patient may begin weight bearing while immobilized or be placed in flexible synthetic cast material that maintains semirigid reduction.

High-Risk Patients

• Patient with spasticity – Spasticity + multiple risk factors (e.g. communication

difficulties and poor nutrition) – These place the patient at particular risk for

developing pressure sores, which result from increased tone after the cast is applied.

“There are no hypochondriacs in casts”

“There are no hypochondriacs in casts”

• Every patient complaint regarding the cast should be evaluated in a timely manner by a member of the medical team.

• Most limbs are more comfortable after immediate immobilization. – Increased pain and neurovascular change should be fully

evaluated.

• Soft-tissue swelling, which may or may not have been present during cast application, may lead to compartment syndrome.

References

• Halanski M, Noonan KJ: Cast and Splint Immobilization: Complications. J Am Acad Orthop Surg 2008;16:30-40.

• Thompson SR, Zlotolow DA: Handbook of Splinting and Casting. Elsevier Mosby, Philadelphia 2012.

• Wells L, Avery AL, Hosalkar HH, Friedman JE, Davidson RS: Cast Wedging: A “Forgotten” Yet Predictable Method for Correcting Fracture Deformity. UPOJ 2010; 20:113-116.