Mon. 22 Aug 2016 talk, QGH

1. Casting and
Splinting
Principles and
Common
Pitfalls
Muhammad Abdelghani
QGH Instructional Lectures
22 Aug 2016

2. “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

3. 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

5. Know Your Materials
• Plaster of Paris (POP)
• Synthetically based
fiberglass

7. POP
• The time-tested form
of immobilization.
• Hemihydrated calcium
sulfate
• First described in 1852

8. POP
• Advantages:
– Less expensive
– More moldable than synthetic
counterparts
– More pliable
• Can be effectively spread after the
cast is univalved

9. POP
• Disadvantages:
– Poor resistance to water
– Relatively low strength-to-
weight ratio
• Heavier (thicker) casts

10. POP
• Associated Exothermic Reaction:
– The conversion of POP to gypsum during setting up is an
exothermic reaction.
• Faster-setting plasters produce more heat.

11. 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.

12. Synthetic Fiberglass Materials
• Disadvantages:
– More expensive.
– More difficult to mold
• More stiff
– Higher risk of pressure on
and constriction of the limb.
– Carcinogenic risk (??)

13. 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

15. 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.

16. Selecting the Appropriate Cast Material
• Considerations:
– Goals and anticipated duration of immobilization
– Patient and financial factors

17. 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.

18. 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

19. 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.

20. 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.

22. “Well Molded” Does Not Mean Tight!
• A cast that is wrapped too
tightly acts like a rigid
tourniquet to the extremity.

23. 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.

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

25. No Direct Contact
• Avoid direct contact between
the skin and plaster, which
can result in abrasions and
lacerations.

26. 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.

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

28. 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.

30. 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.

31. 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.

32. 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)

33. The Hand
Position 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.

34. “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)

35. The Hand
Position 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)

36. The Hand
Position 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

37. “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)

38. The Hand
Position 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

39. “It is easier to regain flexion than
extension at the PIPJ after a period of
immobilisation”
(Hardy, 2004)

40. The Hand
Position 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.

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

43. “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)

44. 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

45. 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.

46. 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.

50. 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

51. Beware!
• Avoid ending below-knee casts at
the fibular neck.
• This places pressure over this
area and are notorious for
causing peroneal nerve palsy.

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

53. Cast Spreading
• Plaster cast:
– Cutting and spreading (univalving) reduce pressure by
40-60%
– Release of padding may reduce pressure an additional
10-20%.

54. 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.

55. 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.

56. 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.

57. 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.

58. 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,..).

59. 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.

60. 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.

61. 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.

63. 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.

64. “There are no hypochondriacs in casts”

65. “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.

66. 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.