Bone cement

Bone cement; composition, generations handling and preparation
hazards

1. Bone Cement By Ihab El- Desouky (M.D.) Asst. Prof. Orthopaedics & Traumatology Pelvis and Joints Reconstruction Unit Kasr Al- Ainy School pf Medicine Cairo University- Egypt

2. BONE CEMENT Definitions : Cement: Synthetic, self-curing organic or inorganic material used to fill up a cavity or to create a mechanical fixation . Bone cement : A bio-material cement obtained by mixing a powder and a liquid & can be molded and implanted as a paste with the ability to set within the body. It is a filler (grout) and not a glue

3. BONE CEMENT History: 1936: Kulzer Co.: heat-curing PMMA (at 100 ⁰C) 1943: Kulzer & Degussa Co.: Cold -curing PMMA (room temperature)—close cranial defects. Birth Of PMMA Bone Cement

4. BONE CEMENT History Early 1950s: Judet & Judet : PMMA femoral head prosthesis ( Plexiglass ) but failed In 1958: Sir John Charnley : Succeeded “Bone Cement On Acrylic Basis” Used PMMA to anchor prosthesis .

5. Components Of Bone Cement Powder: P olymers Polymethyl methacrylate (PMMA) Initiator B enzoyl Peroxide (BPO) Radio- opacifier : B arium Sulfate Zirconia Anti b iotics (heat stable) e.g.: gentamycin, vancomycin tobramycin Liquid Monomer Methyl methacrylate ( polymerizable ) Activator (accelerator): N-Dimethyl-p-Toluidine ( DmpT ) Inhibitor (stabilizer) Hydroquinone

6. Polymerization Process: Powder + Liquid = Reaction Powder dissolves in liquid (PMMA mixed with monomers) AND Initiator ( BPO )reacts with activator ( DmpT )--- Free Radicals ( Radical Polymerization )

7. Radical Polymerization Bonding of monomers +PMMA-- longer polymers chains of variable MW By Time: -Depletion of free radicals (polymerization stops) -Viscosity of the dough increases+ residual monomers. -Release of heat: Exothermic reaction in vitro: 70-80 ⁰C BUT In vivo : 40-45 ⁰C Why?

8. Radical Polymerization Exothermic Reaction: Polymerization shrinkage: In vivo: early shrinkage is compensated by air & water uptake by cement

9. Radical Polymerization Fate of residual monomers Phases of polymerization in surgical procedures: Four phases 1-Mixing. 2-Waiting. 3-Working. 4-Hardening (setting)

10. Handling Of The Bone Cement:

11. Handling Of Bone Cement

12. Handling Of The Bone Cement In general, all bone cements have dough, working and setting TIMES : Dough Time: Beginning of mixing till cement is not stick to gloved fingers (includes mixing and waiting phases) Up to 3 minutes Working Time: End of dough time till the cement is too stiff to manipulate (includes working phase) 5-8 minutes Setting Time: Dough + working times 8-10 minutes

13. Types of Bone Cement: (viscosity) Low viscosity: Long waiting (sticky) phase (3 min) then viscosity rapidly increases during short working phase ( 2 min long) Medium viscosity : Long waiting phase (3 min) but viscosity slowly increases during working and setting. High viscosity: Short waiting phase (1 ½ to 2 min), long working phase with constant viscosity

14. Factors affecting cement preparation

15. Generations Of Cementing

16. Technique of better bone cementing: Pulsatile lavage (Bone bed preparation) -Pulsatile lavage is equally important to pressurization. - Pulsatile lavage improves cement penetration+ reduces the risk of embolic complications during cement pressurization .

17. Technique of better bone cementing: Distal Cement Restrictor: allow formation of closed space for cement pressurization Should be appropriate size to close the canal

18. Technique of better bone cementing: Vacuum Mixing: Reduces Porosity and air inclusion &Increases cement homogeneity----Increases mechanical strength of cement Decrease exposure of surgical team to monomer fumes.

19. Technique of better bone cementing: Pressurization: more cement inter-digitation

20. Technique of better bone cementing: Stem centralizer(s): uniform cement mantle & allow for controlled stem subsidence

21. Technique of better bone cementing: Stem Design: Collar-less : allow stem subsidence by cement shrinkage (creep) Polished : no shear during insertion or subsidence. Tapered : wedged inside the cement in stem travel during subsidence so –-- compression forces (not shear)

22. Properties of Bone Cement Visco -elastic material 1- Creep - Gradual Deformation of material under constant load -Cement creep is reflected as Volume reduction

23. Properties of Bone Cement Stress relaxation Decrease of material stress under condition of constant strain Effect of loading: Compression> Tension> Shear

24. Additives To Bone Cement: ( Opacifiers , Antibiotics ) 1-Opacifiers: Barium sulphate or Zirconium dioxide For: monitoring & detection of failures Radiographic assessment of quality of cementing: Barrack grading :

25. Additives to Bone Cement: Antibiotics: Antibiotics Loaded Acrylic Cement (ALAC) Bone cement acts a delivery system for local antibiotics .

26. Additives to Bone Cement: Antibiotics: Antibiotics Loaded Acrylic Cement (ALAC) Low dose < 2 gram Antibiotic per 40 gram cement High dose > 3.6 gram --- per 40 gram cement

27. Additives to Bone Cement: Antibiotics: Antibiotics Loaded Acrylic Cement (ALAC)

28. Hazards Of Bone Cementing Occupational hazards : on Surgical team 1-Excessive vapor– respiratory irritation 2-High vapor concentration---headache, drowsiness and even loss of consciousness. 3-Skin irritation and burns if exposed to liquid. 4-Contact lenses (soft) penetration by vapor---pitting

29. Hazards Of Bone Cementing Patient Hazards : Bone Cement implantation Syndrome(BCIS) Hypoxia, hypotension, loss of consciousness and even cardiac arrest At time of: cementing, prosthesis insertion, joint reduction, or deflation of tourniquet in stemmed total knee. Etiology: (theories) 1-Monomer liquid absorption into circulation 2-Emblosim: exothermic reaction expand medullary B.V.– embolism of fat , marrow , air or cement particles. 3-Anapylxis and complement activation

30. Hazards Of Bone Cementing Bone Cement implantation Syndrome(BCIS) Prevention: Management:

31. Take Home Messages Bone cementing technique: results and complications. A stem: respects the natural properties of the bone cement Antibiotics loaded cement : dose and use. Complications: strict technique to avoid its occurrence . Thank you