Liquid (Monomer):

• Methylmethacrylate (MMA): The building block. Strong smell.
• DMPT: Accelerator (starts reaction when mixed with powder).
• Hydroquinone: Stabiliser (prevents premature polymerisation in storage).

Powder (Polymer):

• PMMA Beads: Pre-polymerised beads.
• Benzoyl Peroxide: Initiator.
• Zirconium Dioxide / Barium Sulphate: Radiopacifier (makes it white on X-ray).
• Antibiotics: (e.g., Gentamicin) - Optional.

PMMA (polymethylmethacrylate) is an acrylic grout—not adhesive—that provides prosthetic fixation through mechanical interlock into trabecular bone. It forms via exothermic polymerization (80-100°C) between liquid monomer (MMA + DMPT accelerator) and powder polymer (PMMA beads + benzoyl peroxide initiator), progressing through Mixing-Sticky-Doughy-Hard phases. Properties include high compression strength (70-100 MPa) but weak tensile strength. Vacuum mixing reduces porosity and improves fatigue life, while pressurization enhances bone interdigitation. Bone Cement Implantation Syndrome (BCIS) causes hypotension, hypoxia, and potential cardiac arrest from marrow/monomer embolization during femoral pressurization—risk factors include ASA III/IV patients and long stems.

• Compression: High strength (Matches cancellous bone). Good for loading.
• Tension: Very weak.
• Shear: Weak.
• Viscoelastic: Creeps under load (slight deformation over years).

Enhancing Strength:

• Vacuum Mixing: Removes air bubbles, reduces porosity, increases fatigue life.
• Centrifugation: Removes bubbles.
• Pressurisation: Forces cement deeper into bone pores (Micro-interlock).

Pathophysiology:

• Embolisation of marrow fat/cement contents into pulmonary circulation during pressurisation.
• Direct toxic effect of Monomer on myocardium? (Vasodilation).
• Clinical: Hypotension, Hypoxia, Loss of Consciousness to Cardiac Arrest.

Risk Factors:

• Patient: ASA III/IV, COPD, Pulmonary Hypertension.
• Surgery: Femoral component (Hip), Long stems, Metastatic disease.

Prevention:

• Lavage canal (remove fat).
• Venting the femur (drill hole?) - controversial.
• Maintain blood pressure (Anaesthetic alert).

Australian Epidemiology and Practice

AOANJRR (Australian Orthopaedic Association National Joint Replacement Registry) Data:

• Cemented fixation remains the gold standard for THA in elderly patients with osteoporotic bone
• Registry data demonstrates lower revision rates for cemented hemiarthroplasty compared to uncemented in NOF fractures (particularly in patients over 75 years)
• Hybrid fixation (cemented femur, uncemented acetabulum) increasingly common for primary THA
• Registry tracks cement type and antibiotic loading as part of procedural data

RACS Orthopaedic Training Relevance:

• PMMA bone cement and BCIS are core FRACS Basic Science examination topics
• Viva scenarios commonly test understanding of polymerisation chemistry, mechanical properties, and BCIS management
• Key exam focus: monomer vs polymer distinction, generations of cementing technique, and BCIS risk factors
• Examiners expect knowledge of Australian-specific registry data on cementing outcomes

Antibiotic-Loaded Cement in Australia:

• Gentamicin-loaded cement is standard of care for primary arthroplasty in Australia
• Tobramycin and vancomycin preparations also available through Australian suppliers
• PBS restrictions apply to certain antibiotic preparations for cement mixing
• High-dose antibiotic cement used in two-stage revision for periprosthetic joint infection

eTG (Therapeutic Guidelines) Considerations:

• Antibiotic prophylaxis guidelines recommend cefazolin for most joint replacement procedures
• Gentamicin-loaded cement provides local antibiotic delivery complementing systemic prophylaxis
• Vancomycin cement considered for MRSA colonised patients or high-risk revision cases

BCIS Prevention and Management:

• Australian and New Zealand College of Anaesthetists (ANZCA) guidelines address BCIS management
• Team communication protocols emphasise "Cement going in" warning to anaesthetic team
• Third-generation cementing techniques (pulsatile lavage, vacuum mixing, pressurisation) are standard practice

Australian Implant and Cement Suppliers:

• Major suppliers: Stryker (Simplex), DePuy Synthes (CMW), Heraeus (Palacos)
• TGA registration required for all bone cements and antibiotic preparations
• Prostheses List determines private health insurance coverage for implants

1. Charnley J. Acrylic cement in orthopaedic surgery. 1970.
2. Breusch SJ, et al. The effect of pulsatile lavage on the fixation strength of cemented hip replacement. J Arthroplasty. 2002.