Two-Stage Revision THA - Stage 1: Antibiotic Cement Spacer Insertion

Spacer Materials

• Antibiotic cement: Palacos preferred (better elution), 2-3 × 40g packs
• Vancomycin powder: 4-6g
• Tobramycin powder: 3.6g (or Gentamicin 2g)
• Articulating spacer mould: Modular head sizes (22mm, 28mm, 32mm available)
• Steinmann pins: For spacer reinforcement if making hand-moulded

Extraction Equipment

• Universal extraction set: Curved osteotomes, slap hammers
• High-speed burr: For cement removal
• Ultrasonic cement removal: If available (Midas Rex)
• Extended trochanteric osteotomy set: Oscillating saw, cables, plates
• Cerclage wire/cables: For prophylactic protection or fracture fixation

General Equipment

• Pulsatile lavage: 9L minimum (3-6L debridement, 3L final)
• Tissue sampling supplies: 5+ containers for separate tissue samples
• Drains: 2 deep drains minimum
• VAC dressing: If wound concern or repeat procedures planned

Step 1: Intraoperative Tissue Sampling (BEFORE Antibiotics)

CRITICAL: Obtain cultures BEFORE prophylactic antibiotics given. Hold antibiotics until 5+ tissue samples obtained.

Take minimum 5 separate tissue samples from:

1. Pseudocapsule (3 samples from different locations)
2. Interface membrane around acetabular component
3. Interface membrane around femoral component
4. Any obvious purulent collections
5. Synovial fluid aspiration

Each sample in separate sterile container. Send for aerobic, anaerobic, fungal, and AFB culture. Request prolonged culture (14 days for low-virulence organisms).

Step 2: Incision and Exposure

Use previous surgical approach - most commonly posterior (Southern or Moore).

Posterior Approach:

• Position: Lateral decubitus, hip flexed 30°
• Incision: Through previous scar, extending if needed
• Expect dense scarring - careful dissection in tissue planes
• Identify and protect sciatic nerve early
• Tag short external rotators with sutures for later repair (if salvageable)

Considerations:

• Extended incision often needed for visualization
• Anterior approach acceptable if previous approach
• Trochanteric osteotomy if severe scarring/heterotopic ossification

Step 3: Synovectomy and Debridement

Radical synovectomy - remove ALL infected/inflamed tissue:

• Complete excision of pseudocapsule
• Remove all granulation tissue
• Debride necrotic tissue to healthy bleeding margins
• Remove all foreign material (sutures, cement debris)
• Debride bone surfaces to healthy bleeding bone

Step 4: Acetabular Component Removal

Cemented cup removal:

• Identify cement-bone interface
• Use curved osteotomes to disrupt interface
• Lever cup out progressively (protect posterior wall)
• Remove ALL cement with curettes, osteotomes, high-speed burr

Uncemented cup removal:

• Curved osteotomes around rim to disrupt bone ingrowth
• Avoid aggressive levering (acetabular fracture risk)
• Specialized extraction devices for well-fixed components
• May need acetabular rim osteotomy for extraction

Step 5: Femoral Component Removal - Decision Point

Assessment: Is stem loose or well-fixed?

If LOOSE:

• Extract with slap hammer and trunnion extractors
• Remove all cement if cemented design
• Relatively straightforward

If WELL-FIXED (cementless):

• STOP - proceed to Extended Trochanteric Osteotomy (ETO)
• Do NOT attempt brute force extraction (fracture risk 30%+)

Step 6: Extended Trochanteric Osteotomy (ETO) - If Required

Indication: Well-fixed cementless stem, distally fixed stem, cement mantle requiring removal.

Technique:

1. Mark osteotomy length (usually 12-15cm, extending 2-3cm beyond stem tip)
2. Apply prophylactic cerclage at distal extent of planned osteotomy
3. Use oscillating saw for lateral and anterior cortical cuts
4. Create controlled crack with osteotomes (lateral to medial)
5. Open trochanteric fragment like a "book" - maintains muscle attachments
6. Now femoral component and cement are accessible
7. Remove component under direct vision

Step 7: Complete Cement Removal and Canal Preparation

Remove ALL cement - any retained cement harbors bacteria in crevices:

• High-speed burr for cement on cortical bone
• Long curettes for canal cement
• Ultrasonic tools if available
• Serial reaming to fresh bleeding bone
• Flexible reamers for curved canals

Debride medullary canal to healthy tissue:

• Sequential reaming until fresh bleeding bone
• Remove all interface membrane
• Brush canal walls

Step 8: Copious Pulsatile Lavage

Minimum 9 litres pulsatile lavage:

• 3-6L during debridement
• 3L final lavage before spacer insertion
• Use pulsatile lavage system (not bulb syringe)

Some surgeons use additive solutions (betadine, chlorhexidine, hydrogen peroxide) - evidence mixed, mainly saline.

Step 9: Antibiotic Cement Spacer Fabrication

Standard Formulation (EXAM ESSENTIAL):

• 2 × 40g cement (80g total) - Palacos has best elution characteristics
• Vancomycin 4-6g (Gram-positive, MRSA coverage)
• Tobramycin 3.6g OR Gentamicin 2g (Gram-negative, biofilm penetration)
• Maximum 10% antibiotic by weight to maintain mechanical properties

Mixing Technique:

1. Mix antibiotic powders with cement powder FIRST (before liquid)
2. Ensure homogeneous distribution
3. Add liquid monomer
4. Mix until doughy consistency
5. Mould into spacer components

Spacer Types:

• Articulating (preferred): Hand-moulded or modular systems (Prostalac, STAGE, Interspace)
• Static: Reserved for severe bone loss, instability, medically unfit for mobilization

Step 10: Femoral Spacer Component Insertion

Hand-moulded spacer:

• Form cement around Steinmann pin or K-wire for reinforcement
• Create stem shape that will fit canal
• Insert in doughy phase, seat firmly
• Maintain neutral alignment

Commercial spacer systems:

• Follow manufacturer technique
• Select appropriate size based on canal dimensions
• Ensure stable press-fit

Key points:

• Cement should interdigitate with cancellous bone for stability
• Maintain leg length (avoid excessive shortening)
• Slight anteversion (10-15°)

Step 11: Acetabular Spacer Insertion

Options:

1. Articulating spacer head: Cement hemispherical head placed on femoral component, articulates against native acetabulum (or augment cup)
2. Cement into acetabulum: Fill acetabular defect with antibiotic cement
3. Commercial systems: Pre-formed acetabular spacer components

Key considerations:

• Size head appropriately for stability (larger = more stable)
• Ensure coverage by acetabulum
• Accept some bone loss - reconstruction at stage 2

Step 12: Stability Assessment

Test stability in multiple positions:

• Hip flexion to 90° with internal rotation
• Extension with external rotation
• Assess for impingement, dislocation

If unstable:

• Larger head size
• Adjust offset if possible
• Consider constrained liner at stage 2
• Accept higher dislocation risk (10-20% inherent)
• May need abduction brace post-operatively

Step 13: Wound Closure

Layered closure:

• Deep drains (2 minimum) - to antibiotic-loaded cavity
• Capsule/short external rotator repair if possible
• Fascia lata - strong absorbable suture
• Subcutaneous - absorbable suture
• Skin - staples or absorbable subcuticular

Consider:

• VAC dressing if wound compromise or planned return to OR
• Tension-free closure essential (skin necrosis = exposed spacer = failure)

Step 14: Documentation and Specimen Handling

Document in operative note:

• All tissue samples taken (locations, culture requests)
• Components removed (manufacturer, size, condition)
• Intraoperative findings (purulence, membrane, bone loss)
• Spacer type and antibiotic content
• Stability assessment

Specimen handling:

• Each tissue sample in SEPARATE container
• Clearly labelled with site
• Request prolonged culture (14 days)
• Explanted components can be sent for sonication (biofilm disruption)

Immediate Post-operative

• Weight bearing: Toe-touch weight bearing with frame/crutches
• DVT prophylaxis: LMWH or aspirin per protocol
• Drains: Remove when <50mL/24hrs (usually day 2-3)
• IV antibiotics: Start post-operatively based on cultures (empiric initially)

Antibiotic Protocol

• Duration: Minimum 6 weeks IV antibiotics
• PICC line: Insert before discharge
• Outpatient parenteral antibiotic therapy (OPAT): Home or infusion centre
• Tailored regimen: Adjust based on culture sensitivities when available
• ID involvement: Essential for complex organisms, optimize regimen

Monitoring During Spacer Period

• Weekly bloods: CRP, ESR (expect initial rise then gradual normalization)
• Clinical assessment: Wound healing, pain, systemic symptoms
• Watch for: Spacer dislocation (sudden pain, shortening), fracture, persistent drainage

Criteria for Stage 2 (EXAM ESSENTIAL)

1. Minimum 6 weeks IV antibiotics completed
2. 2-6 week antibiotic holiday (to allow re-aspiration)
3. Normalized inflammatory markers: CRP <10, ESR <30 for 2+ consecutive weeks
4. Negative aspiration during antibiotic holiday
5. Healed wound with no drainage
6. No clinical signs of infection

References

1. Parvizi J, et al. New definition for periprosthetic joint infection: from the Workgroup of the Musculoskeletal Infection Society. Clin Orthop Relat Res. 2011;469(11):2992-2994.

2. Kurtz SM, et al. Economic burden of periprosthetic joint infection in the United States. J Arthroplasty. 2012;27(8 Suppl):61-65.

3. Hsieh PH, et al. Two-stage revision hip arthroplasty for infection: comparison between interim cement spacer and antibiotic-loaded cement prosthesis. J Bone Joint Surg Am. 2004;86(9):1989-1997.

4. Younger AS, et al. The outcome of two-stage arthroplasty using a custom-made interval spacer to treat infected hip arthroplasty. J Arthroplasty. 1997;12(6):615-623.

5. Masri BA, et al. Cementless two-stage exchange arthroplasty for infection after total hip arthroplasty. J Arthroplasty. 2007;22(1):72-78.

6. Fink B, et al. Two-stage cementless revision of infected hip endoprostheses. Clin Orthop Relat Res. 2009;467(7):1848-1858.

7. Penner MJ, et al. The extended trochanteric osteotomy in femoral component revision. Orthop Clin North Am. 1999;30(2):219-226.

8. Springer BD, et al. Systemic antibiotic regimens for periprosthetic joint infection in adults: a review. Curr Rev Musculoskelet Med. 2018;11(1):103-110.

9. Osmon DR, et al. Diagnosis and management of prosthetic joint infection: clinical practice guidelines by IDSA. Clin Infect Dis. 2013;56(1):e1-e25.

10. Tan TL, et al. Culture-negative periprosthetic joint infection: an update on what to expect. J Bone Joint Surg Am. 2018;100(12):1124-1133.