Patient Selection | Bone Quality | Age | Activity Level | AOANJRR Outcomes
- Cemented fixation uses PMMA bone cement (polymethylmethacrylate) for immediate stability
- Cementless fixation relies on biological ingrowth into porous coating (takes 6-12 weeks)
- Patient age and bone quality are primary selection criteria
- AOANJRR data shows excellent outcomes with both methods when appropriately selected
- Hybrid THA (cementless cup + cemented stem) common in Australia
- “Cemented stems have longer track record (Charnley since 1960s)
- “Cementless relies on press-fit initial stability and osseointegration
- “Cement disease = aseptic loosening from particulate cement debris
- “Young patients (under 65) benefit from cementless (easier revision)
Clinical Imaging
Imaging Atlas
Age, bone quality, and activity level drive fixation choice. Young active patients (under 65) get cementless for easier future revision. Elderly osteoporotic patients (over 75) benefit from immediate cement stability. This is evidence-based, not surgeon preference.
The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) is the world's largest joint registry. Know the survival curves for cemented vs cementless in different age groups. This is essential for Australian exam context.
Modern cement technique includes pressurization, cement gun delivery, distal cement plug, pulsatile lavage, and cement restrictor. Poor technique causes early failure. Third-generation cement technique achieves excellent outcomes.
Press-fit initial stability is mandatory for cementless fixation. Without it, micromotion prevents ingrowth and causes fibrous interface. Requires good bone quality, precise reaming, and appropriately sized implant. Not suitable for poor bone stock.
| Patient Profile | Age | Bone Quality | Recommended Fixation |
|---|---|---|---|
| Young active | Under 50 years | Good bone stock | Cementless both components (easier revision) |
| Middle-aged active | 50-65 years | Good to moderate bone | Cementless (or hybrid with cemented stem) |
| Elderly active | 65-75 years | Moderate bone quality | Hybrid (cementless cup + cemented stem) |
| Elderly low-demand | Over 75 years | Osteoporotic bone | Cemented both components (immediate stability) |
| Rheumatoid arthritis | Any age | Poor bone quality | Cemented both components (bone quality issue) |
CEMENTCEMENT - Indications for Cemented Fixation
Hook:CEMENT helps remember when to use cemented fixation - elderly patients with poor bone quality
PRESSPRESS-FIT - Cementless Fixation Requirements
Hook:PRESS-FIT describes the technique and requirements for successful cementless fixation
HYBRIDHYBRID - Mixed Fixation Strategy
Hook:HYBRID is the middle ground - combining advantages of both fixation methods
Overview and Epidemiology
PMMA Bone Cement (Polymethylmethacrylate)
- Provides immediate mechanical interlock
- Gold standard since Charnley (1960s)
- Ideal for elderly, osteoporotic bone
- Requires proper third-generation technique
Biological Osseointegration
- Press-fit initial stability required
- Bone ingrowth into porous coating (6-12 weeks)
- Ideal for young, active patients with good bone
- Easier revision if needed in future
Total hip arthroplasty fixation refers to the method of attaching prosthetic components to host bone. The two primary methods are cemented (using polymethylmethacrylate bone cement) and cementless (relying on biological ingrowth). Each has distinct indications, advantages, and limitations.
Historical evolution:
- 1960s: Sir John Charnley developed the low-friction arthroplasty using PMMA cement
- 1970s: Excellent long-term results established cemented THA as gold standard
- 1980s: Concerns about "cement disease" led to development of cementless implants
- 1990s: Recognition that both methods work well when appropriately indicated
- 2000s: Registry data confirms excellent outcomes with modern techniques for both
"Cement disease" is a misnomer - it's actually aseptic loosening caused by particulate debris (cement, polyethylene, metal) triggering osteolysis. The problem isn't cement itself but particle generation from micromotion and wear. Modern cement technique and improved polyethylene have dramatically reduced this complication.
Current practice patterns:
- Young patients (under 50): predominantly cementless
- Middle-aged (50-65): cementless or hybrid
- Elderly (65-75): hybrid common in Australia
- Very elderly (over 75): cemented both components
- Poor bone quality (any age): cemented
Pathophysiology of Fixation and Loosening
Cemented fixation pathophysiology:
The primary mechanism of cemented fixation is mechanical interlock, not chemical bonding. PMMA cement penetrates 3-5mm into the cancellous bone, creating a mechanical interdigitation that distributes load from the implant to the bone. The cement mantle acts as a grout, filling irregularities and creating a stable interface.
Failure mechanisms in cemented THA:
- Particle disease: Cement, polyethylene, or metal particles activate macrophages
- Osteolysis: Activated macrophages recruit osteoclasts, leading to bone resorption
- Mantle fracture: Thin cement mantle (less than 2mm) is prone to fracture
- Interface failure: Cement-bone interface weakens over time from micromotion
- Subsidence: Component migration indicates loss of fixation
Cementless fixation pathophysiology:
Cementless fixation relies on biological osseointegration. Initial press-fit stability must be achieved (less than 150 microns micromotion), which allows bone to grow into the porous coating over 6-12 weeks. The biological interface is stronger than cement at maturity.
Failure mechanisms in cementless THA:
- Inadequate press-fit: Micromotion greater than 150 microns prevents bone ingrowth
- Fibrous interface: Without osseointegration, a fibrous membrane forms (unstable)
- Stress shielding: Stiff implants shield proximal bone, causing atrophy
- Particle-induced osteolysis: Bearing surface particles still cause bone loss
- Subsidence: Poor initial stability leads to progressive migration
Key concept: Both fixation methods ultimately fail from particle-induced osteolysis when bearing surfaces generate debris. Modern highly crosslinked polyethylene has dramatically reduced this problem.
Classification
Fixation Classification by Method
| Type | Components | Mechanism | Optimal Patient |
|---|---|---|---|
| Fully Cemented | Cemented cup + cemented stem | PMMA mechanical interlock | Elderly (over 75), osteoporosis |
| Fully Cementless | Cementless cup + cementless stem | Biological osseointegration | Young (under 65), good bone stock |
| Hybrid | Cementless cup + cemented stem | Combined approach | Age 65-75, Dorr C femur |
| Reverse Hybrid | Cemented cup + cementless stem | Combined approach | Poor acetabular bone, good femur (rare) |
Dorr Classification of Femoral Morphology
- Type A: Narrow canal, thick cortices - ideal for cementless
- Type B: Intermediate - either method suitable
- Type C: Wide canal, thin cortices - cemented preferred
Clinical Presentation and Indications
When to choose THA fixation method:
The "clinical presentation" for fixation choice is the patient evaluation that determines which method to use. This assessment occurs pre-operatively and intra-operatively.
Age-based indications:
- Under 50 years: Cementless preferred (future revision likely)
- 50-65 years: Either method acceptable based on bone quality
- 65-75 years: Hybrid common in Australian practice
- Over 75 years: Cemented preferred (osteoporosis common, lifetime implant)
Activity level:
- High-demand athletic patients: Cementless (biological fixation)
- Low-demand sedentary patients: Cemented acceptable at any age
- Manual laborers: Either method if bone quality adequate
Medical comorbidities:
- Osteoporosis: Cemented (cannot achieve press-fit)
- Rheumatoid arthritis: Cemented (poor bone quality, protrusio)
- Previous DVT/PE: Consider avoiding cement (embolism risk)
- Cardiac disease: Cemented requires careful monitoring (hypotension risk)
These comorbidities significantly influence fixation choice and surgical planning.
Intra-operative decision-making:
Even with pre-operative planning, final fixation choice may change based on:
- Actual bone quality encountered during reaming
- Unexpected bone defects or sclerosis
- Inability to achieve adequate press-fit (convert to cemented)
- Intraoperative fracture (may favor cemented for immediate stability)
Investigations and Pre-operative Planning
AP pelvis (mandatory):
- Assess Dorr classification of femur (Types A, B, C)
- Measure canal diameter at isthmus
- Assess cortical thickness
- Identify dysplasia, protrusion, or bone defects
- Measure leg length discrepancy
Lateral hip:
- Assess femoral bow
- Identify anterior/posterior cortical thickness
- Plan stem size and design
Template both views:
- Use digital templating software
- Determine component sizes for cemented and cementless options
- Plan for restoration of offset and leg length
Accurate templating is essential for component selection and surgical planning.
Templating for fixation choice:
Digital templating helps determine if anatomy suits cemented or cementless:
- Narrow canal (canal-to-cortex ratio less than 0.5): Dorr A, cementless ideal
- Wide canal (canal-to-cortex ratio over 0.75): Dorr C, cemented preferred
- Intermediate canal: Either method appropriate
Pre-operative optimization:
Before choosing fixation, optimize:
- Correct anemia (Hb greater than 120 for elective THA)
- Treat osteoporosis (vitamin D, bisphosphonates if time permits)
- Optimize medical comorbidities (cardiac, respiratory)
- Cease anticoagulation per protocol
Management - Surgical Techniques
PMMA bone cement characteristics:
- Polymethylmethacrylate (PMMA) mixed with liquid monomer
- Exothermic polymerization (can reach 80-110°C)
- Working time 5-8 minutes, setting time 10-12 minutes
- Provides immediate mechanical stability
- Does not bond to bone - acts as grout filling irregularities
Modern cement technique (third-generation):
- Preparation: Pulsatile lavage, dry bone, insert distal cement restrictor
- Mixing: Vacuum mixing reduces porosity, wait for dough stage
- Delivery: Retrograde cement gun, pressurize to 3-5mm penetration
- Stem insertion: Insert and hold steady until polymerization complete
- Curing: Wait 10-12 minutes, check mantle on fluoroscopy
Goal: 2-3mm uniform cement mantle in all Gruen zones.
Cement mantle zones (Gruen zones):
- Zone 1: Proximal-lateral (stress shielding common)
- Zone 7: Proximal-medial (calcar region)
- Zones 2-6: Mid and distal stem
- Goal: 2-3mm uniform cement mantle in all zones
A uniform 2-3mm cement mantle is essential. Mantle less than 2mm risks fracture. Direct bone-implant contact (lack of mantle) creates stress concentration and early loosening. The cement restrictor prevents distal cement escape and creates a closed pressurization system.
Advantages: Immediate stability, works in poor bone, proven track record.
Disadvantages: Difficult revision, embolism risk, potential cement hypotension.
AOANJRR Registry Data and Outcomes
The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR):
- World's largest national joint registry
- Tracks over 500,000 hip replacements
- Annual report essential reading for Australian exam
- Provides evidence-based fixation recommendations
Key AOANJRR findings for primary THA:
Survival by fixation type (registry pattern, approximately 15-year data):
- Cemented both components: high survivorship, broadly in the mid-90% range
- Cementless both components: high survivorship, broadly in the mid-90% range
- Hybrid (cementless cup + cemented stem): among the best-performing constructs in registry reports
- Reverse hybrid: less common, selected cases
Exact percentages differ between registries and between annual reports; quote the current annual report of the relevant registry rather than a fixed number.
Age-stratified outcomes:
- Under 55 years: Cementless superior (easier revision)
- 55-65 years: All methods similar outcomes
- 65-75 years: Hybrid excellent results
- Over 75 years: Cemented excellent results
Reasons for revision:
- Aseptic loosening: Most common overall
- Dislocation: Higher in cementless (head size effect)
- Infection: Similar across all fixation types
- Periprosthetic fracture: Higher in cementless
For the Australian exam, know the AOANJRR data. Be able to state that modern techniques achieve 94-96% survival at 15 years for all fixation methods when appropriately selected. The registry supports age-based and bone quality-based selection, not dogmatic fixation choice.
Factors affecting survival (registry-identified):
- Surgical approach (posterior vs lateral)
- Surgeon volume (high volume = better outcomes)
- Head size (36mm optimal for dislocation vs wear)
- Bearing surface (highly crosslinked polyethylene)
- Component positioning (cup inclination, version)
Surgical Technique Summary
Cemented Technique Essentials
Third-Generation Cement Technique:
- Pulsatile lavage - clean all blood and debris from cancellous bone
- Bone drying - hydrogen peroxide-soaked packs, dry sponges
- Distal cement restrictor - creates closed pressurization system
- Vacuum mixing - reduces cement porosity, improves strength
- Cement gun delivery - retrograde filling from distal to proximal
- Pressurization - achieve 3-5mm cement penetration into cancellous bone
- Stem insertion - single, deliberate insertion without repositioning
- Maintain pressure - hold until full polymerization (10-12 minutes)
Cementless Technique Essentials
Acetabular Component:
- Sequential reaming to bleeding subchondral bone
- Underream 1-2mm smaller than cup diameter
- Impaction to achieve line-to-line peripheral rim fit
- Add 2-3 supplemental screws if stability questionable
Complications by Fixation Method
| Complication | Fixation Type | Incidence | Prevention/Management |
|---|---|---|---|
| Aseptic loosening | Cemented | 1-2% at 10 years | Modern cement technique, avoid thin mantle |
| Aseptic loosening | Cementless | 1-2% at 10 years | Adequate press-fit, good bone quality |
| Thigh pain | Cementless stem | 5-20% (usually mild) | Modulus mismatch, choose appropriate stem design |
| Fat embolism | Cemented | Rare but serious | Pulsatile lavage, venting hole, monitor vitals |
| Cement hypotension | Cemented | Under 1% | Adequate fluid resuscitation, avoid hypovolemia |
| Intraoperative fracture | Cementless | 1-5% | Careful reaming, broaching, avoid over-sizing |
| Periprosthetic fracture (late) | Cementless | 2-3% at 10 years | Avoid stress shielding, ensure proximal fit |
| Difficult revision | Cemented | Variable | Cement removal tools, risk of perforation |
Aseptic loosening mechanisms:
Cemented:
- Particle debris (cement, polyethylene, metal) → macrophage activation
- Osteoclast recruitment → periprosthetic osteolysis
- Progressive radiolucent lines at cement-bone interface
- Eventually leads to mechanical failure
Cementless:
- Inadequate initial stability → fibrous interface instead of ingrowth
- Micromotion prevents osseointegration
- Stress shielding → proximal bone loss
- Particle debris from bearing surfaces still an issue
Differential diagnosis of the painful THA (by fixation context):
A loose or failing fixation must be distinguished from other causes of a painful hip replacement, because the management differs completely. Aseptic loosening is a diagnosis of exclusion - periprosthetic joint infection must always be ruled out first.
| Diagnosis | Typical clue | Key discriminating test |
|---|---|---|
| Aseptic loosening | Start-up pain, progressive over years, thigh/groin pain | Progressive radiolucent lines, subsidence; normal CRP/ESR |
| Periprosthetic joint infection | Rest pain, early or persistent pain, warmth, sinus | Raised CRP/ESR, aspiration with synovial WCC/alpha-defensin, cultures |
| Periprosthetic fracture | Acute pain after a fall or low-energy trauma | Radiographs (Vancouver classification); assess stem stability |
| Instability / recurrent dislocation | Pain with specific positions, sensation of giving way | History plus radiographs of component position (version, inclination) |
| Stress shielding / thigh pain (cementless) | Activity-related thigh pain with a well-fixed stem | Stable implant on serial films, proximal femoral atrophy |
| Adverse local tissue reaction | Pain, effusion, especially with metal-on-metal or modular junctions | Metal ions (Co/Cr), MARS MRI for pseudotumour |
| Extrinsic / referred pain | Pain not matching implant, radicular or claudicant features | Spine and vascular assessment; THA is a diagnosis of exclusion |
Postoperative Care and Rehabilitation
Immediate post-operative (Day 0-1):
- Full weight-bearing immediately (cement provides instant stability)
- Mobilize same day or next day with physiotherapy
- Hip precautions based on approach (posterior vs lateral)
- DVT prophylaxis per protocol
Early phase (Week 1-6):
- Progress to independent mobilization
- Wean from walking aids as tolerated
- Full weight-bearing encouraged
- No restrictions based on fixation method
- X-ray at 6 weeks to confirm position
Long-term:
- Annual follow-up with X-ray for first 5 years
- Then biennial if stable
- Monitor for late loosening
Cemented fixation allows immediate full weight-bearing without concerns about osseointegration.
Outcomes
AOANJRR Outcomes Summary
Overall THA Survival (All Fixation Types):
- 1-year survival: 98.5%
- 5-year survival: 97.2%
- 10-year survival: 95.5%
- 15-year survival: 94-96% (varies by fixation)
Age-Stratified Outcomes:
- Under 55 years: Cementless optimal (easier future revision)
- 55-65 years: All methods similar outcomes
- 65-75 years: Hybrid excellent results
- Over 75 years: Cemented excellent results
Revision Reasons by Frequency:
- Aseptic loosening (most common overall)
- Dislocation/instability
- Infection
- Periprosthetic fracture
- Bearing surface wear
Evidence Base
- Two long-term series of original cemented Charnley low-friction arthroplasty (22.2mm head, cemented all-polyethylene socket) confirmed excellent function beyond 25 years, with reported survivorship around 85% at 25 years. The authors emphasise that polyethylene is the weak point: mean wear was approximately 0.1mm per year and drove the late failures, not the cement itself.
- 226 cemented Charnley arthroplasties in patients with a mean age of 31.7 years followed for a mean of 19.7 years. Twenty-five-year survival of the femoral component was 81% for the whole series, but the acetabular component fared worse (68% at 25 years), with wear, loosening and acetabular revision the major limiting factors. Annual wear averaged 0.11mm/year and correlated with cup migration and revision.
- Synthesis of national hip registry reports (Australia, Denmark, England-Wales, Finland, Netherlands, New Zealand, Norway, Sweden, Switzerland) from 2010-2017. Across almost every register, cemented fixation carried a lower all-cause revision risk than uncemented fixation in patients older than 75 years, yet uncemented use remained high or rising - the 'uncemented paradox'. Femoral stem fixation appeared to be the dominant revision risk factor in older patients.
- Competing-risk analysis of 214,638 primary THAs from the Dutch Arthroplasty Register (LROI). The 10-year cumulative revision risk varied with age and fixation, ranging from approximately 1.6% to 13%, with consistently higher revision risk in younger patients regardless of fixation type.
- Randomised controlled trial of 100 cemented all-polyethylene cups with minimum 8-year follow-up. Steady-state femoral head penetration was effectively zero (approximately -0.0002 mm/year) in the highly cross-linked remelted group versus 0.138 mm/year in the moderately cross-linked annealed group (p less than 0.001), a more than tenfold reduction in measurable wear.
- Tribological testing of porous coatings against human cadaveric bone showed that rougher porous coatings generated higher friction (coefficient of friction up to ~0.9 versus 0.45 for a polished surface) and greater mechanical interlock, improving primary stability. Relative displacements up to ~35 microns occurred without true sliding at the interface, refining the classic micromotion thresholds assumed for osseointegration.
- RCT of 400 patients (mean age 85) with displaced intracapsular hip fracture, randomised to cemented polished tapered or uncemented hydroxyapatite-coated hemiarthroplasty, with 3-year follow-up. Early recovery of mobility was better with cemented fixation, and 3-year mortality was significantly lower in the cemented group (p = 0.029), with no increase in implant-related complications or revision.
- The major national joint registries (Australian AOANJRR, the National Joint Registry for England and Wales, and the American AJRR) collectively report on millions of primary THAs. Across these registries, cemented, cementless and hybrid constructs all achieve high 10- to 15-year survivorship (broadly in the mid-90% range) when matched to the appropriate patient, with cumulative revision risk consistently higher in younger patients. Exact percentages and rankings differ year to year and between registries, so cite the current annual report rather than a fixed figure.
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“An 82-year-old woman with severe osteoarthritis of the right hip requires total hip arthroplasty. She has osteoporosis with T-score of -2.8. She is independently mobile with a stick. What fixation method would you use and why?”
“A 45-year-old man who is a recreational runner requires total hip arthroplasty for post-traumatic arthritis following acetabular fracture 10 years ago. He has good bone stock. What fixation would you recommend and why?”
“A 68-year-old woman requires total hip arthroplasty. She has moderate activity level. Intraoperatively, you find the acetabulum has good bone stock, but the femur is Dorr Type C (wide canal, thin cortices, osteoporotic). What fixation would you use and why?”
MCQ Practice Points
Q: What is the most appropriate fixation method for an 82-year-old woman with osteoporosis (T-score -2.8)? A: Cemented both components. Poor bone quality cannot achieve press-fit. Registries show high survivorship (mid-90% range) and lower revision risk than uncemented over age 75.
Q: What is the most critical factor for cementless fixation success? A: Initial press-fit stability (micromotion less than 150 microns). Without it, fibrous interface forms instead of osseointegration.
Q: Which fixation method has the highest 15-year survival per AOANJRR? A: Hybrid constructs are typically among the best performers, with cementless and cemented also achieving high survivorship (all broadly mid-90% range at 15 years). All are excellent when appropriately selected; quote the current annual report for exact figures.
Q: What is the ideal cement mantle thickness for femoral stem fixation? A: 2-3mm uniform mantle. Less than 2mm risks cement fracture and early loosening. Direct bone-implant contact without cement creates stress concentration.
Q: What is the optimal pore size for bone ingrowth in cementless components? A: 50-150 microns for traditional porous coating. Smaller pores allow only fibrous tissue. Trabecular metal (400-600 microns) allows deeper ingrowth.
Q: Why is hybrid THA (cementless cup, cemented stem) common in Australian practice? A: Combines excellent cementless acetabular fixation with reliable cemented femoral fixation in older patients with poor bone quality. AOANJRR shows excellent outcomes.
Guidelines, Registries & Global Practice
Global epidemiology. Total hip arthroplasty is one of the most effective and most frequently performed elective operations worldwide, with primary osteoarthritis the leading indication across all high-income registries. Lifetime revision risk is strongly age-dependent: in a competing-risk analysis of 214,638 primary THAs from the Dutch Arthroplasty Register, the 10-year cumulative revision risk ranged from roughly 1.6% to 13%, with the highest risk in the youngest patients regardless of fixation type (according to PubMed, Gademan et al., Acta Orthop 2021, DOI).
Registry evidence on fixation. The major national joint registries are the strongest real-world evidence base for implant survival:
| Registry | Region | What it shows on fixation |
|---|---|---|
| AOANJRR | Australia / NZ | All fixation types achieve high 10-15 year survivorship; cumulative revision risk higher in younger patients |
| NJR | England, Wales, NI | Cemented and hybrid constructs have low revision rates in older patients; very large dataset on stem and bearing comparisons |
| AJRR | USA | Cementless fixation predominates in US practice; tracks bearing surface and head-size trends |
| SHAR (Swedish) | Sweden | Historic stronghold of cemented fixation with excellent long-term survivorship data |
| Multi-registry synthesis | Global | Cemented fixation carries lower all-cause revision risk than uncemented in patients over 75 across almost all registers (the 'uncemented paradox') |
The multi-registry synthesis by Bunyoz et al. found that, across Australia, Denmark, England-Wales, Finland, the Netherlands, New Zealand, Norway, Sweden and Switzerland, cemented fixation was associated with a lower all-cause revision risk than uncemented fixation in patients older than 75 years, despite continued high uncemented use in many countries (according to PubMed, Clin Orthop Relat Res 2020, DOI).
Guidance side by side. Major bodies broadly agree that fixation should be matched to age and bone quality rather than chosen dogmatically:
| Body | Position | Practical implication |
|---|---|---|
| NICE (UK) | Use implants with an Orthopaedic Data Evaluation Panel (ODEP) survivorship benchmark; cement strongly favoured for fragility hip-fracture arthroplasty | Evidence-driven implant selection; cement for elderly fracture patients |
| AAOS (US) | Supports both cemented and cementless fixation; cementless predominates in US practice, with patient-specific selection | Either method acceptable with appropriate patient selection |
| AO Foundation / fracture guidance | Cemented fixation preferred for arthroplasty after displaced intracapsular fracture in the elderly | Cement in fragility-fracture arthroplasty |
| Registry-informed consensus | Cemented or hybrid femoral fixation in patients over 75; cementless reasonable in younger patients with good bone | Age- and bone-quality-stratified choice |
The recommendation to cement in elderly fracture patients is supported by Level I evidence: an RCT of 400 patients (mean age 85) found lower 3-year mortality and better early mobility with cemented hemiarthroplasty and no increase in complications (according to PubMed, Parker et al., Bone Joint J 2023, DOI).
Global practice variation. Fixation choice varies markedly by region rather than by evidence alone. Cementless fixation predominates in the USA and in several Scandinavian countries (e.g. Denmark, Norway), whereas the UK and Sweden retain higher cemented use; hybrid constructs are common in the UK and Australia for intermediate-age patients. In limited-resource settings, cost and cement availability also influence the choice. The persistence of high cementless use in older patients despite registry data favouring cement is the most clinically important practice-evidence gap in this topic.
Whatever board you sit, defend fixation choice with registry evidence and the age/bone-quality principle, not country-specific habit. Key points: lifetime revision risk is highest in the young (favouring revisable cementless constructs); cemented or hybrid femoral fixation lowers revision and mortality risk in the elderly; and modern highly cross-linked polyethylene reduces the wear-driven osteolysis that limits all fixation types.
CEMENTED FIXATION
- PMMA bone cement - immediate mechanical stability
- Indications: Age over 75, osteoporosis, rheumatoid, poor bone quality
- Third-generation technique: lavage, restrictor, vacuum mix, gun, pressurize
- Goal: 2-3mm uniform cement mantle in all Gruen zones
- Advantages: immediate stability, proven track record, works in poor bone
- Disadvantages: cement removal difficult in revision, embolism risk
- Registries: high survivorship (mid-90% range); lower revision than uncemented over 75
CEMENTLESS FIXATION
- Biological ingrowth - press-fit initial stability, osseointegration 6-12 weeks
- Indications: Age under 65, good bone quality, active patients
- Porous coating: 50-150 micron optimal for ingrowth
- Technique: underream 1-2mm acetabulum, line-to-line femur fit
- Advantages: easier revision, no cement debris, biological fixation
- Disadvantages: requires good bone, 6-12 weeks for fixation, thigh pain
- Registries: high survivorship (mid-90% range); lifetime revision risk highest in young
HYBRID FIXATION
- Cementless cup + cemented stem (most common)
- Indications: Age 65-75, mixed bone quality, Dorr Type C femur
- Combines advantages: biological cup + immediate stem stability
- Very common in Australian practice
- Registries: among the best-performing constructs at 15 years
- Not a compromise - deliberate strategy for specific scenarios
PATIENT SELECTION
- Under 50: cementless both components
- 50-65: cementless or hybrid
- 65-75: hybrid common in Australia
- Over 75: cemented both components
- Dorr Type A (thick cortices): cementless ideal
- Dorr Type C (thin cortices): cemented preferred
- Bone quality trumps age in decision-making
AOANJRR KEY DATA
- All methods achieve 94-96% survival at 15 years
- Hybrid fixation: among the best-performing constructs
- Age-specific outcomes support stratified selection
- Registry shows hybrid very common in Australian practice
- Know annual report key findings for exam
EXAM TRAPS
- Don't choose cementless in osteoporotic bone
- Don't choose cemented in young active patients
- Hybrid is not a compromise - it's often optimal
- Know Dorr classification and implications
- Quote AOANJRR data to support decisions
- Explain specific technique for chosen fixation