Orthopaedics POP and Bone Cement ppt

1. TOPIC- Plaster of Paris &
Bone Cement
MODERATOR- Dr. MAHESH G
PRESENTER- Dr. KARTHIK M V

2. History
• Hippocrates, in about 350 BC, used bandages stiffened
by waxes and resins to treat fractures.
• POP was first used by Antonius Matthysen, a Dutch
military surgeon in year 1858.
• Made by rubbing dry plaster-of-Paris powder into
coarsely woven cotton bandages, which were then
soaked in water before being applied.

3. History
• Plaster of Paris name derived from accident to the house built in
deposits of gypsum, near Paris.
• House burnt down  when rain fall on baked mud of the floor
 foot prints in mud set rock hard.

4. Plaster of Paris
• Pop consists of roll of muslin stiffened by Dextrose or starch and
impregnated by hemihydrate of calcium sulfate.
• When water is added the calcium sulphate takes up its water for
crystallization.
• EXOTHERMIC REACTION- liberates heat

5. • Setting time: time taken to change from powder form to crystalline
form.
• Setting time: 4–5 minutes
• Drying time: time taken to change from crystalline form to anhydrous
form.
• Drying time: 24–48 hours.

6. Factors affecting setting time
• Increasing setting time
- Hot water
- salt solution
- Borax solution
- Addition of resins
• Decreasing setting time
- Cold water
- sugar solution

7. • Commonly available sizes—4 inch, 6 inch × 2.7 meter.

8. Uses of POP bandage
• As a slab for immobilization
Extent of slab coverage—50–70% circumference
(2/3rd) of limb.
For upper limb—12-14 layers and for lower
limb—16-18 layers.
Should immobilize one joint above and below
fracture- except distal radius fracture.

9. Uses of POP bandage
• As definitive casting
Wrapped around whole circumference of limb or part involved.
The overlapping of bandage is 1/3rd– 1/2 of previous turn.

10. Uses of POP bandage
• Functional cast bracing
• Deformity correction serial casting.
• Spica
• Pin plaster technique.

11. FUNCTIONAL CAST BRACING
Patellar tendon bearing cast bracing :
SARMIENTO 1963
• It is a closed method of fracture treatment
• Principle: It is based on the belief that continuing
function while a fracture is uniting it does three
things:
– Enhances osteosynthesis
– Promotes healing of fracture
– Prevent complication like joint stiffness.

12. • Mechanism of action Pascal’s law:
• When the limb is loaded there is generation of intracompartmental
pressure around fracture site that exerts pressure on wall of facial
compartment.
• As there is a rigid cast around limb, the similar amount of pressure
starts in opposite direction that maintain the reduction of fracture.

13. Prerequisites for patellar tendon bearing (PTB) casting
• Angular and rotational deformity must be corrected.
• There is no pain at fracture site on minimal movements.
• There is no deformity at fracture site.
• There should be a reasonable resistance to telescopy.

14. Hip Spica
• Hip: 45° flexion and slight abduction
(clear the perineum)
• Knee: 45° flexion (less than 45° may lead
to loss of fracture reduction)
• Extent of cast-
oProximally – up to nipple rest on ribcage
(bony support)

15. oDistally –
• Single hip spica: Involving only one leg
and extend up to foot.
• One and half spica: Involves one leg up to
foot and other leg up to knee.
• Double hip spica: Involving both leg up to
foot.
• Uses
- Fracture femur in children
- After pediatric hip surgeries.

16. Pin Plaster technique
• Principle: Stabilization of fracture with cast
and Steinmann pin assembly.
• How to apply:
• 1st pin above fracture and 2nd below
fracture, as far as possible.
• Achieve reduction.
• Cast applied in reduced position.
• Minimal joint involvement.

17. • Advantages of pin plaster technique:
• Prevents joint stiffness
• Early mobilization
• Check rotation
• Disadvantages of pin plaster technique:
• Loss of reduction
• Pin track infection.

18. Alternatives to Plaster of Paris
• Fibre glass
Composition: Fiber-glass impregnated with
polyurethane polymer.
 Colorful and sticky.
Setting time: 1–2 minutes.
Full strength of cast is achieved in 2–4 hours
Activated by water or other agents.
Caution: Surgical gloves must be worn before using this
cast.
Commonly available sizes 3" and 5" × 3.6 meter.

19. • Fibre glass
Advantages
-Lighter
-Stronger than POP
-Impervious to water
- Radiolucent
Disadvantage
-Costly

21. Padding
• Distal to proximal with 50% overlap, minimum of 2 layers
• Extra padding at bony prominences like fibular head, malleoli, patella,
olecranon etc.

25. Why wet roller bandaging during POP slab
application?
• Wet bandages increase POP setting time and provide enough time for
plaster molding and limb manipulation.
• Wet bandages well incorporated with slab and provide extra strength.
• Dry bandages absorbs water from POP and decreases the setting time
and side by-side it does not incorporates well with slab.

26. Some common slabs
• Below elbow slab/ short arm back slab
- Extends from 2 finger breath below the elbow crease or 5cm below
the tip of olecranon to distal crease in the palmar aspect.
-MCP joints should be freely mobile
Indications
- Wrist fractures
- Colle's fracture

27. • Cock up slab
Wrist in 40-45degree extension, MCP in
90degree flexion, IP joint in extension.
Indications
- Metacarpal fractures
• Above elbow slab
Indications
- both bone fracture of forearm
- supracondylar fracture of humerus
- proximal radius or ulnar fracture

29. • Above Elbow slab on extension
Indications
- Olecranon fractures
- supracondylar fracture of humerus flexion type
Position
-Extends from middle of upper arm to distal crease on palmar aspect
- Elbow in extension

30. • U- Slab
Proximal and shaft of humerus fracture.
Applied from medial to lateral aspect of arm
encircling the elbow, and overlapping the
shoulder.
Utilizes dependency traction for fracture
reduction

31. • Above knee slab
Position- knee in 10-15 degree flexion, ankle in
neutral position
Indications
-Supracondylar fractures of femur
-Both bone fractures of leg

32. • Below Knee Slab
Indications
- Malleolar fractures
- Metatarsal fractures
- Calcaneal fractures

36. Plaster disease
• When the limb is put into plaster and joints
are immobilized for a long period, joint
stiffness, muscle wasting and osteoporosis is
unavoidable.
• Reduced by early weight bearing and
isometric exercises

37. Fracture disease
• Prolonged immobilization in a non functional cast lead to vicious cycle
of pain, swelling and unresolved edema.
• Edema is a proteinaceous exudate that will get converted to
gelatinous material and deposited as scar.
• Tissue around joint and tendon cause joint stiffness and contractures.
• Muscle atrophy and osteoporosis
• Reflex sympathetic dystrophy may sometime occur and further
complicate the picture.

38. Complications with POP bandage:
– Neurovascular compromise
– Compartment syndrome
– Pressure sore
– Purulent dermatitis
– Reactionary edema
– Fracture disease
– Wasting of limb
– Joint stiffness

39. Care of a limb in plaster
• Constant movements of finger or toes
• Keep limb elevated
• Do not bring the plaster in contact with water
• Report immediately if any swelling, color changes, numbness or
excess pain.

40. Bone Cement/ PMMA / Plexiglas

41. Bone Cement/ PMMA/ Plexiglas
• Polymethyl methacrylate (PMMA), is commonly known as bone cement,
and is widely used for implant fixation in various Orthopaedic and trauma
surgery.
• Word cement is misnomer- used to describe a substance that bonds two
things together.
• It is used for fixation of artificial joints where it fills the free space between
the prosthesis and bone and thus acts as a ‘grout’.
• Thus acts as a mechanical bond

42. • The use of interface material (cement made of
plaster and colophony) for fixation of implants was
first described by Themistocles Gluck in 1870 so
use of “cementing” per se should be credited to
him.
• Compound PMMA came from the thesis of Otto
Rohm’s “polymerization products of acrylic acid”

43. • Sir John Charnley (1958) –Father of
modern arthroplasty.
• First used it for total hip arthroplasty
• First to succeed in anchoring femoral prosthesis
with use of bone cement
• realized that PMMA easily could be used to fill
the medullary canal and is easy to blend with the
bone morphology
• Published six cases in Journal of Bone and Joint
Surgery (JBJS) British edition.

44. Constituents
• 2 components-powder and liquid form.
• The two components are mixed at
appropriate ratio of 2:1 to start chemical
reaction called polymerization- forms
PMMA cement.
• 40gm of powder and 20ml of monomer
liquid

45. Powder component-
1).Copolymer beads based on the substance PMMA
(polymethylmethacrylate)
2). Initiator-benzoyl peroxide (BPO), which encourages the polymer
and monomer to Polymerize at room temperature
3). Contrast agents such as zirconium dioxide (ZrO2) or barium sulphate
(BaSO4) to make the bone cements radiopaque
4). Antibiotics eg, gentamicin, tobramycin

46. • Liquid component-
Is a colourless liquid of intense odors
1).A monomer, methylmethacrylate (MMA)
2).Accelerator (N,N-Dimethyl para-toluidine) (DMPT)
3).Stabilizers (or inhibitors) Hydroquinone to prevent premature
polymerization from exposure to light or high temperature during storage
Chlorophyll or artificial pigment sometimes added to cements for easier
visualization in case of revision surgeries.

47. • Polymerization of MMA is too slow so
• When the two components are mixed
• The liquid monomer polymerizes around the pre polymerized
powder particles to form hardened PMMA.
• In the process, heat is generated, due to an exothermic reaction.
Why separate Components ?

48. Functions of bone cement
• Immobilize implant, anchors the prosthesis in bone
• Transfers load onto the bone and increases load
carrying capacity of prosthesis-bone- cement- bone
system.
• Absorbs forces
• Deliver antibiotics if needed.

49. Uses of bone cement:
• Arthroplasty procedures of hip, knee and other joints.
• Fixation of bone defects and as bone substitute, vertebral defects ,
pathological fractures to fill the substance loss
• Used in dental procedures and to fill craniofacial defects
• To deliver antibiotics eg: cement beads
• As spacer after removal of infected prosthesis

50. Antibiotic bone cement
• Not all antibiotics are suitable for use in bone cements.
Following factors need to be considered,
1). Preparation must be thermally stable and able to
withstand the exothermic temperature of polymerization.
2). Must have broad antimicrobial coverage.
3). Must be available as a powder.
4). Must have a low incidence of allergy.
5). Must not significantly compromise mechanical integrity.
6).Must elute from the cement over an appropriate period
of time.
Examples: Gentamycin, Tobramycin, Erythromycin,
Cefuroxime, Vancomycin, Colistin

51. Dosing of antibiotic:
• Low dose: Less than 2 g of antibiotic/ 40 g of cement, used for THR
and TKR surgeries as prophylaxis (eg. 1.2 g of tobramycin + 1g
vancomycin)
• High dose: More than 2 g of antibiotic/40 g of cement, used in
revision THR, spacers, beads formation. (eg. 3.6g tobramycin + 4g
vancomycin)

52. Vertebroplasty
• Impregnation of polymethyl methacrylate into
the vertebral body is called Vertebroplasty
• pain relief and rehabilitation
• extradural extravasation of bone cement that
would cause neurological compromise
• Formation of cement emboli that may migrate
in the spinal canal

53. Kyphoplasty
• More effective
• Inflating a balloon inside the vertebra restoring
vertebral height and then bone cement is injected into
the balloon
• concerns of compression fractures of adjacent
vertebrae
• Indications
- Painful fractures with a back pain
- Compression fracture due to osteoporosis
- Adjacent vertebra” of a fractured and treated one
(D12-L1) as preventive

54. Phases And Times(Curing process)
• 1) Mixing phase
• 2) sticky/ waiting phase
• 3) working phase
• 4) hardening (setting) phase

55. 1).Mixing Phase:
• The time taken to fully integrate the powder
and liquid.
• There is release of the initiator benzoyl
peroxide and the accelerator DMPT which
causes the cement to begin the polymerization
process.
• It is important for the cement to be mixed
homogeneously, thus minimizing the number
of pores.
• The mixing can be done by hand or with the aid
of centrifugation or vacuum technologies.

56. 2).Sticky/waiting phase (dough time):
• lasts several minutes. cement achieves a suitable viscosity for
handling (i.e, can be handled without sticking to gloves).
• Dough time is the time point measured from the beginning of
mixing to the point when the cement no longer sticks to
surgical gloves.
• Under typical conditions (23°C-25°C, 65% relative humidity),
dough time is 2-3 minutes after beginning of mixing for most
bone cements
• At this phase the components are well mixed and the bone
cement may be loaded into a syringe, cartridge, or injection
gun for assisted application.

57. 3). Working phase/working time:
• The working phase is the period during which the cement can be
manipulated and the prosthesis can be inserted.
• The working phase results in an increase in viscosity and the
generation of heat from the cement.
• The implant must be implanted before the end of the working
phase
• Working time is the interval between the dough time and setting
time, typically 5-8 minutes.

58. • 4).Setting Phase/Setting Time(Hardening)
• During this phase, the cement hardens (cures) and sets
completely, and the temperature reaches its peak.
• The temperature increase is due to conversion of
chemical to thermal energy as polymerization takes place.
• The cement continues to undergo both volumetric and
thermal shrinkage as it cools to body temperature
• Hardening is influenced by the cement temperature, the
operative room temperature, and the body temperature
of the patient.
• Setting time is usually about 8-10 minutes

59. Factors that affect dough, working, and setting times:
• 1). Mixing Process: mixing too rapidly can accelerate
dough time and is not desirable since it may produce
a weaker, more porous bone cement
• 2). Ambient Temperature: Increased temperature
reduces both dough and setting times approximately
5% per degree Centigrade, whereas decreased
temperature increases them at the same rate.
• 3). Humidity: High humidity accelerates setting time
whereas low humidity retards it.

60. • There are two requirements for bone cement viscosity
during the working phase:
• 1). Viscosity must be sufficiently low to facilitate the delivery
of the cement dough from the syringe to the bone site.
• 2).Secondly, it must penetrate into the interstices of the
trabecular bone
• 3). Viscosity of the bone cement should be sufficiently high
to withstand the back bleeding pressure, there by avoiding
the risk of the inclusion of blood into the cement

61. • Cement flaws –
• Cement additives or air entrapment produces voids or pores referred
as flaws
• Air entrapment during mixing
• Critical size of flaw is reached, there is stress concentration causing
cement breaks
• Reduced by vacuum mixing or centrifugation methods

62. Methods of application
• 1).Manual mixing
• The cement is mixed in an open bowl(plastic
or stainless steel) carefully and thoroughly to
minimize the entrapment of air.
• Once dough is formed the surgeon should
wait until the cement no longer adheres to
the glove and the surface has become dull as
opposed to shiny
• The cement can then be taken into gloved
hands and kneaded thoroughly
• It is vital that premature insertion of cement
is avoided as this may lead to a drop in the
patient’s blood pressure.

63. • Following introduction the implant must be firmly
held in position to avoid movement and
pressurization must be maintained until the cement
finally hardens.
• Excess bone cement must be removed before the
cement has completely hardened.
• This method induces 7% of porosity

64. • Drawbacks of open bowl hand mixing technique:
1). Exposure to the resulting noxious fumes created
serious safety concerns
2). A certain amount of porosity in the final material
remained unavoidable due to the air introduced by
stirring during hand spatulation

65. • 2). Centrifugation
• In this technique, cement was first mixed manually
and then subjected to centrifugation to eliminate any
air inclusions introduced during mixing and thus
reduce porosity
• 2,300-4,000rpm for 1-2min
• Porosity reduces to 1% or less

66. • 3).Vacuum mixing:
• Vacuum mixing reduces bone cement porosity and
reduces monomer evaporation and exposure in the
operating room.
• Mixing cement under vacuum yields a homogenous
mix without affecting viscosity or other properties of
the cement

67. • The methods for application of bone cement include hand packing,
injection, and gun Pressurization
• 1).Hand packing: The original method for hip arthroplasty was hand
packing, where cement in the femoral canal was finger packed.
• Cementing in total knee arthroplasty is still commonly hand-packed
because the surfaces are readily visualized.
• 2).Injection : cement may be applied using cement gun and syringe.
Appropriate viscosity of cement is required to inject using the gun
/syringe. A small amount of cement should be extruded from the
syringe and visually assessed to ensure that the surface of the cement
appears dull and excessive flow under gravity has ceased

68. • 3). Pressurization :
• Injection of the cement with a gun offers a
mechanical advantage to force more cement into the
interstices of the bone via higher pressurization and
improves bone cement interface .
• The pressure applied to the cement has to be larger
than the blood pressure so as not to be pushed out
of the bone
• When pressurizing the cement in the femur, a positive
sign of pressurization is marrow extrusion in the
greater trochanter (sweating trochanter sign)

69. Evolution of cementing techniques:
• 1).First generation :
- It involved the hand mixing of cement in bowels.
-There was only a minimal preparation of the femoral canal and
cancellous bone was left in-situ
- The canal was irrigated and suctioned prior to the digital application
of cement
-Finger pressurization of cement
2). Second generation:
-All cancellous bone is removed as near to the endosteal surface
-Distal cement restrictor was also used.
-Preparation of femoral canal
-There is pulsatile irrigation, packing and drying of the femoral canal
-Retrograde insertion of cement with a cement gun

70. • 3).Third generation:
-Cement is now prepared using a vacuum-centrifugation, which
further reduces porosity
-The femoral canal is irrigated with pulsatile lavage and then
packed with adrenaline soaked swabs.
-After insertion of the cement in a retrograde fashion, the
cement is pressurised
3).Fourth generation:
-Use of distal and proximal centralizers to ensure an even
circumferential cement mantle around the stem
-Central placement of stem to increase its longevity

71. Barrack’s and Harris femoral cementation
• Grade A – complete filling of medullary canal “white out”
bone cement interface
• Grade B – Radiolucency covering <50% of cement – bone
interface
• Grade C – Radiolucency > 50% of bone – cement interface
• Grade D – gross Radiolucency or absent of cement distally
to tip of stem

72. Caution and adverse effects
• Hypotensive episodes and cardiac arrest have been
reported during cementation or prosthesis insertion
• Pressurization and thorough cleaning of the bone
with expulsion of bone marrow has been associated
with the occurrence of pulmonary embolisms
• The premature insertion of bone cement may lead to
a drop in blood pressure which can further lead to
cardiac arrhythmias or to an ischaemic myocardium.
• Hypotensive effects are due to methyl methacrylate.

73. BCIS (Bone cement implantation syndrome)
• It usually occurs at one of the five stages in the
surgical procedure :
• femoral reaming, acetabular or femoral cement
implantation, insertion of the prosthesis or joint
reduction.
• Clinical features: hypoxia, hypotension, cardiac
arrhythmias, increased pulmonary vascular resistance
(PVR) and cardiac arrest.
• It is most commonly associated with hip arthroplasty

74. Cement Disease / osteolysis
• Shielding effect of cement and thinning of bone per se.
• Misnomer
• Previously thought – cement is foreign body so its culprit
• Causes are – infections, cortical thinning (heat necrosis of bone),
osteolysis ( septic or aseptic)

75. Drawbacks of bone cement:
• One of the major drawbacks of bone cement in joint
replacement is cement fragmentation and foreign
body reaction to wear debris, resulting in prosthetic
loosening and periprosthetic osteolysis
• The production of wear particles from roughened
metallic surfaces and from the PMMA cement
promotes local inflammatory activity mediated by
cytokines such as interleukin-1, interleukin-6 and TNF
alpha
• It is neither osteoinductive nor osteoconductive and
does not remodel

76. • Reduction of heat generation – N- acetylcysteine
• Radio opacifying agents – iodine compounds and organobismuth
( Zirconium oxide & Baso4 reduce osteoblast activity)
• Nanosilver added cement shows inhibition to MRSA

77. Dorr classification
Type A: narrow canal with thick cortical
walls (champagne flute canal).
Type B: moderate cortical walls.
Type C: wide canal with thin cortical
walls (stove-pipe canal).
Its calculated by measuring the ratio
between the canal width at lesser
trochanter and the canal width 10 cm
below the lesser trochanter
Indications of bone cement use- all
cases of type C and few type B types

78. Reference’s
• Traction’s and applications, Stewart 2nd edition
• McRae’s orthopaedic trauma 4th edition
• Essential Orthopaedics by Manish Kumar Varshney 3rd Edition
• Bed side clinics in orthopaedics Updendra Kumar 2nd Edition

79. THANK YOU