THA FIXATION OPTIONS - CEMENTED VS CEMENTLESS
Patient Selection | Bone Quality | Age | Activity Level | AOANJRR Outcomes
FIXATION METHODS
Critical Must-Knows
- 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
Examiner's Pearls
- "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 Gallery
Critical THA Fixation Exam Points
Patient Selection Critical
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.
Know AOANJRR Data
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.
Cement Technique Matters
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.
Cementless Requires Stability
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.
Fixation Selection Algorithm
| 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) |
CEMENT - Indications for Cemented Fixation
Memory Hook:CEMENT helps remember when to use cemented fixation - elderly patients with poor bone quality
PRESS-FIT - Cementless Fixation Requirements
Memory Hook:PRESS-FIT describes the technique and requirements for successful cementless fixation
HYBRID - Mixed Fixation Strategy
Memory Hook:HYBRID is the middle ground - combining advantages of both fixation methods
Overview and Epidemiology
Cemented Fixation
PMMA Bone Cement (Polymethylmethacrylate)
- Provides immediate mechanical interlock
- Gold standard since Charnley (1960s)
- Ideal for elderly, osteoporotic bone
- Requires proper third-generation technique
Cementless Fixation
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 Clarification
"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
THA Fixation Types
| 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.
Pre-operative assessment:
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
Radiographic assessment:
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
Cement Mantle Requirements
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 (15-year data):
- Cemented both components: 94.5% survival
- Cementless both components: 95.8% survival
- Hybrid (cementless cup + cemented stem): 96.2% survival
- Reverse hybrid: 93.1% survival (less common, selected cases)
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
AOANJRR Exam Relevance
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
Fixation-Specific Complications
| 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
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
- Over 20-year follow-up of cemented Charnley hips showed 90% survivorship. Established cemented fixation as gold standard with excellent long-term results. Failures primarily due to polyethylene wear and osteolysis, not cement failure.
- Analysis of over 200,000 THAs showed cemented stems superior in patients over 75 years. Cementless stems showed better results in younger patients (under 55). Age-based fixation selection supported by large registry data.
- 15-year survival: Hybrid (96.2%), Cementless (95.8%), Cemented (94.5%), all excellent results. Hybrid THA most common fixation in Australia. Age-specific recommendations align with international data.
- Highly crosslinked polyethylene reduced wear rates by over 90% compared to conventional polyethylene. Dramatic reduction in osteolysis and aseptic loosening with modern bearing surfaces. Addresses primary failure mode of both cemented and cementless THA.
- Histological studies show bone ingrowth into porous coating begins at 6 weeks and matures by 12 weeks. Initial press-fit stability is critical - micromotion greater than 150 microns prevents osseointegration. Press-fit achievable with good bone quality and proper technique.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Fixation Choice in Elderly Patient
"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?"
Scenario 2: Fixation Choice in Young Active Patient
"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?"
Scenario 3: Hybrid Fixation Decision-Making
"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
Fixation Selection
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. AOANJRR: 94.5% survival at 15 years.
Cementless Success Factor
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.
AOANJRR Outcomes
Q: Which fixation method has the highest 15-year survival per AOANJRR? A: Hybrid fixation (96.2%), followed by cementless (95.8%) and cemented (94.5%). All excellent when appropriately selected.
Cement Mantle
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.
Pore Size for Ingrowth
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.
Hybrid THA Rationale
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.
Australian Context
AOANJRR Registry: World's largest national joint registry (established 1999). Mandatory reporting of all Australian joint replacements. Essential reading for exam - know the survival data.
Australian Practice Patterns:
- Hybrid THA very common (especially ages 65-75)
- Young patients: cementless both components
- Elderly patients: cemented both components
- Practice heavily influenced by AOANJRR data
Key Registry Data:
- Hybrid: 96.2% survival at 15 years (highest)
- Cementless: 95.8% survival at 15 years
- Cemented: 94.5% survival at 15 years
- All methods excellent when appropriately selected
Epidemiology: Over 50,000 THAs performed annually in Australia. Primary OA is leading indication. Revision rate under 5% at 10 years reflects excellent modern outcomes.
Exam Preparation
For the exam, know AOANJRR survival rates and understand why hybrid is so common in Australian practice. Quote registry data to support fixation decisions.
THA FIXATION OPTIONS
High-Yield Exam Summary
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
- •AOANJRR: 94.5% survival at 15 years
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
- •AOANJRR: 95.8% survival at 15 years
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
- •AOANJRR: 96.2% survival at 15 years (highest)
- •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: 96.2% (highest survival)
- •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