components, mechanisim of delivery, uses and complications of bone cement in orthopaedics

1. Bone cement
DR. NAVEEN BAGILUMANE

2. Bone cement

3. Bone Cement
 In reality, “Bone Cement” is a misnomer .Word cement is used to
describe a substance that bonds two things together, But bone
cement acts as a space-filler that creates a tight space which holds the
implant against the bone.
 Originally developed for Dental applications.
 Using in orthopaedics for more than 40 years.
 Gold standard in the field of joint replacement surgery.
 Neither Osteoinductive, nor Osteoconductive and does no remodeling
of bone.

4. History trace back to…..
 Themistokles Gluck ,a German surgeon, 1870
 Fixed a total knee prosthesis made of ivory using
cement made of plaster and colophony
“...for a better fixation, I mixed plaster with
colophony, which cures up to the hardness ofglass.”

5. History trace back to…..
 1958 – Sir John Charnley used self
curing PMMA to anchor femoral head
prosthesis to femur
 First cement - Nulife

6. What is bone cement?
 Self curing organic or inorganic formulations which may or
may not contain antibiotics used to fill up a cavity or to create
a mechanical fixation of prosthesis to living bone.
 Chemical name - PMMA

7. Interest in orthopaedics
 Joint Replacement Surgery
 Spinal Compression Fractures
 Chronic Osteomyelitis
 Tumours

8. Composition
POWDER (2) LIQUID (1)
Polymer : PMMA Monomer: Methyl methacrylate
(MMA)
Initiator : BPO (Benzoyl peroxide) Accelerator: N, N-Dimethyl para-
toluidine (DMPT)
Radio-opacifier: Barium sulphate
(BaSO4)/Zirconia (ZrO2)
Stabilizer: Hydroquinone

9. Why separate components?
 Polymerisation of MMA is too slow ( hrs to days)
 Pure MMA is of low viscosity can easily diffuse in blood
 Much easier to shape
 Heat polymerisation can boil monomer
 Pure MMA volumetric shrinkage

10. Processing and handling
Four phases :
1. Mixing
2. Waiting
3. Working
4. Setting

11. 1.Mixing
 Viscosity starts to increase
 Chemical reaction :
1. Wetting - Surface area of Polymer beads
dissolved by MMA
2. Polymerization
 Phase ends – formation of Homogenous mass
(tooth paste like consistency)
which is transferred to cement gun

12. What is polymerisation?
 Free radical polymerisation.
 Carbon-to-carbondouble bonds broken
and newcarbonsingle bonds form
 Exothermic reaction.
 Temperature reach up to 70-120 C.
May cause thermal bone damage.
 Viscosity increases.

13. How to mix?
Hand mixing :
 Open bowl using spatula
 1 to 2 Hz, period of 2min
 Disadvantages :
- Introduction of Voids
- Porosity 7% and higher
- Excessive mixing
increases porosity

14. Centrifugation
 Liquid & powder hand mixed then
centrifuged
 2300 – 4000 rpm for 0.5 – 3 min
 Adv : Dramatic decrease in porosity by
1%
 Disadv : Sedimentation of radiopacifiers
 It works only in low viscosity and its
achieved by chilling MMA monomer

15. Vacuum mix
 Contents placed in bowl –
mixed after vacuum conditions
 Adv : Low Porosity
Low exposure of
vapours
Distribution of
Radiopacifiers

16. 2. Waiting phase
 Viscosity increases
 Chemical reaction :
Chain propagation starts
Polymerisation continues
 Ends by sticky dough

17. 3.Working phase
 Cement is no longer sticky but of sufficiently low viscosity to
enable surgeon to easily apply cement
 Chemical reaction :
Exothermic reaction
Polymerisation continues
Viscosity increases

18. 4. Setting
 Chain Growth Finished
 No Movability
 Cement Hardened
 High Temperature.
 Volumetric & Thermal shrinkage

19. Functions of Bone cement
 Allows secure fixation of implant and bone
 Mechanical interlock and space filling
 Load transferring
 Maintenance/restoration of bone stock
 Release of antibiotics

20. How to deliver cement?
1st Generation
 Hand / Finger packing
 Femoral component used – stainless steel & co
– cr alloy
 Failed due to geometry of implants
narrow medial margins
sharp corners

21. 2nd Generation
 Cement gun
 Placement of bone cement - retrograde fashion
 Plastic plug – cement pressurisation
 Pulsatile lavage – cleanse femoral canal of loose
cancellous bone, blood, fat, marrow contents & dried
prior to cementing
it increases the shear strength at bone cement
interface
 improved survival rate of implant

22. 3rd Generation
 Pressurisation of cement during insertion
 Porosity reduction
 Surface modification of implant itself

23. 4th Generation
 Use of proximal & distal
centralizer in an attempt to
make uniform cement mantle

24. Bone bed
preparation
Surgeon
Cementing
technique

25. Antibiotics Loaded Bone cement
Ideal antibiotic properties :
 Preparation must be thermally stable
 Antibiotic properties not affected by heat
 Must be water soluble for diffusion into tissues
 Bactericidal
 Gradual elution over an appropriate time period
 Minimal local inflammatory response

26. Contd..
 Have action against common pathogens like S.aureus, S.
epidermidis ,coliforms and anaerobes.
 Must not significantly compromise mechanical integrity
 Must be available as a powder.
 Must have a low incidence of allergy.

27. Which antibiotics to use?
 Gentamycin (most common) andtobramycin are commonly
used
 Vancomycin (ultrafine powder) is used as lyophilised
vancomycin. It greatly reduces fatigue strength.
 Ciprofloxacin may inhibit soft tissuehealing
 Penicillins and cephalosporins exhibits stability and good
elution properties. But are avoideddue to their potential
allerginicity.

28. ALBC : ANTIBIOTIC LOADED BONE
CEMENT

29. How to asses radiologically?
 Barrack’s Cement mantle grading
 Gruen zones

30. Barrack’s femoral component
cementation Quality grading
Grade Radiographic charcterstics
A Complete filling of medullary canal, without radiolucent line between
cement & bone ( White-Out)
B Radiolucent line covering upto 50% of cement-bone interface
C Radiolucent line covering between 50 -99% of cement – bone
interface or incomplete cement mantle
D Complete Radiolucent line (100%) at cement-bone interface and/or
absence of cement distally to end of stem

31. Gruen zones
 7 zones in AP / lateral
Radiographs
 What is measured?
Radiolucent lines at bone
cement and prosthesis cement
interface
 Progression of no. of Zones -
Loosening

32. Mechanism of loosening
Debris produced because of
mechanical factors
Biological response by formation of
FIBROUS MEMBRANE b/w cement &
bone interface
Results in loosening

33. Bone cement in Tumours
Benificial role
Cytotoxic effect
Direct
toxicity of
monomer
By mixing
with MTX
Mechanical
Decreases
blood
supply
Thermal
Structural
support

34. Contraindications
 Pregnancy
 Active infection
 Hypersensitivity (d/t histamine release n Complement
activation C3a/C5a)
 Metabolic disorder

35. Bone Cement Implantation
Syndrome – (BCIS)
 HYPOXIA, HYPOTENSION or both and/or unexpected LOSS
OF CONSCIOUSNESS
 occurring around the time of cementation, prosthesis
insertion, reduction of the joint or, occasionally, tourniquet
deflation in a patient undergoing cemented bone surgery.

36. Clinical picture varies..
 Hypoxia
 Hypotension
 Cardiac arrhythmias
 increased Pulmonary Vascular Resistance (PVR)
 Cardiac arrest

37. Classification
• Grade 1: moderate hypoxia (SpO2-94%) or hypotension [fall
in systolic blood pressure (SBP) 20%].
• Grade 2: severe hypoxia (SpO2-88%) or hypotension (fall in
SBP 40%) or unexpected loss of consciousness.
• Grade 3: cardiovascular collapse requiring CPR.

38. Etiology of BCIS
1. Absorption of monomer into circulation
2. Embolization
3. Histamine release & Hypersensitivity
4. Complement activation
5. Multimodal