Hip Resurfacing Arthroplasty

Major hip resurfacing systems:

Birmingham Hip Resurfacing (BHR):

• Introduced 1997 by Derek McMinn
• Cast high-carbon cobalt-chromium alloy
• Cemented femoral component
• Uncemented acetabular component
• Best registry data of all resurfacing systems
• Even BHR showed higher revision rate than conventional THA

ASR - the failure:

• Introduced 2003 as easier alternative to BHR
• Shallow acetabular component (high edge-loading)
• Poor femoral component design
• Exceptionally high failure rates led to recall
• Became the poster child for MoM failure

Understanding these implant differences helps explain why some patients did better than others with resurfacing.

Femoral component fixation:

Cemented (most common):

• Cement fills space between bone and metal
• Cement exotherm may damage blood supply
• Allows immediate weight bearing
• Used in BHR and ASR

Cementless (less common):

• Hydroxyapatite coating for bone ingrowth
• Avoids cement exotherm
• May reduce AVN risk (theoretical)
• Requires good bone quality

Acetabular component fixation:

Cementless (standard):

• Press-fit with porous coating
• Screw augmentation available
• Standard approach for most systems

Hybrid approach:

• Cemented femoral, cementless acetabular
• Most commonly used combination
• BHR standard technique

The choice between cemented and cementless femoral fixation remains debated, with no clear winner.

Critical positioning parameters:

Femoral component:

• Valgus preferred (reduces neck stress)
• Avoid varus (increases fracture risk)
• Neutral version (10-15 degrees anteversion)
• Avoid notching anterior femoral neck

Acetabular component:

• Inclination: 40-45 degrees (same as THA)
• Anteversion: 15-20 degrees
• Avoid edge-loading (high inclination or retroversion)

Combined version:

• Must avoid impingement
• Avoid combined retroversion (instability)

Original indications (2000-2010):

Hip resurfacing was marketed for young active patients as a bone-preserving alternative. The ideal candidate profile was:

Patient factors:

• Age under 65 years (typically under 55)
• Male gender (females 2-3x higher failure rate)
• Active lifestyle with desire to return to high-demand activities
• Good bone quality (no osteoporosis)

Anatomic factors:

• Large femoral head (over 50mm diameter ideal)
• Normal hip anatomy (no dysplasia)
• Good femoral neck geometry
• No femoral head cysts

Pathology factors:

• Primary osteoarthritis preferred
• Post-traumatic arthritis acceptable
• Inflammatory arthritis (relative contraindication)

Extremely limited current indications:

Most surgeons have completely abandoned hip resurfacing. A tiny minority might consider it in:

Very narrow patient profile:

• Young male (under 55 years)
• Large femoral head (over 55mm)
• Excellent bone quality
• Normal hip anatomy
• Primary osteoarthritis
• Willing to accept higher complication rate
• Committed to lifelong metal ion monitoring

Realistic counseling required:

• Higher revision rate than conventional THA
• Risk of ALVAL requiring revision
• Femoral neck fracture risk
• Need for blood metal ion monitoring
• Uncertain long-term outcomes

Absolute contraindications:

Relative contraindications:

• Age over 65 years (THA preferred)
• Inflammatory arthritis (poor bone quality)
• Obesity (higher failure rate)
• Hip dysplasia (abnormal anatomy)
• Previous hip surgery (scarring and anatomy distortion)
• Femoral neck width under 35mm (fracture risk)

These contraindications help explain why the suitable patient population was always very small.

For young active patient with hip arthritis:

Modern standard approach (2024):

1. Conservative management first

   • Activity modification
   • Physiotherapy and core strengthening
   • NSAIDs and analgesia
   • Weight loss if applicable
   • Intra-articular steroid injection

2. Surgical options when conservative fails:

Primary choice - Conventional THA:

• Ceramic-on-polyethylene bearing (most common)
• Ceramic-on-ceramic bearing (ultra-low wear)
• Excellent long-term outcomes (over 95% survival at 15 years)
• Established monitoring protocols
• Well-understood complication profile

Second choice - Preservation procedures (if very early disease):

• Hip arthroscopy for FAI (if primarily labral/cartilage pathology)
• Periacetabular osteotomy for dysplasia
• Femoral osteotomy for deformity

Rarely considered - Hip resurfacing:

• Only in exceptional circumstances
• Young male with very large femoral head
• Patient insists after full counseling
• Surgeon experienced with technique

The vast majority of young patients are better served with conventional THA using modern bearing surfaces.

Clinical decision pathway:

Step 1: Is patient suitable for any hip surgery?

• Medical optimization
• Realistic expectations
• Willing to commit to rehabilitation

Step 2: Can symptoms be managed non-operatively?

• Trial conservative management first
• At least 3-6 months unless severe

Step 3: What is the primary pathology?

• Advanced arthritis → THA or resurfacing
• Early arthritis with mechanical symptoms → Preservation
• Dysplasia → PAO versus THA

Step 4: For advanced arthritis - THA vs resurfacing?

Choose conventional THA if:

• Female gender (absolute)
• Small femoral head under 50mm (absolute)
• Any AVN, cysts, or poor bone quality (absolute)
• Age over 55 years (relative)
• Patient prefers established technique (most patients)

Consider resurfacing only if:

• Male gender
• Large femoral head over 55mm
• Excellent bone quality
• Primary OA
• Patient understands and accepts risks
• Surgeon experienced and still performing procedure

Step 5: Execute chosen procedure with excellence

• Proper technique
• Appropriate component positioning
• Post-operative monitoring protocol

In practice, Step 4 almost always leads to conventional THA in 2024.

Essential patient counseling topics:

Benefits of resurfacing (theoretical):

• Bone stock preservation
• Large femoral head (stability, lower dislocation risk)
• Easier revision to THA if needed (debatable)
• Potential for higher activity (unproven)

Risks of resurfacing (proven):

• Higher revision rate (15-20% at 10 years vs 5-10% for THA)
• Femoral neck fracture (1-2% per year in first 5 years)
• ALVAL and pseudotumor (10-15%)
• Metal ion elevation requiring monitoring
• Potential systemic metal toxicity
• Uncertain very long-term outcomes

Alternative - conventional THA:

• Excellent outcomes (over 95% survival at 15 years)
• Multiple bearing surface options
• Well-established monitoring
• Lower complication rate
• No metal ion concerns with modern bearings

Monitoring requirements if resurfacing chosen:

• Annual clinical review
• Blood cobalt and chromium levels annually
• Plain radiographs annually
• MRI if symptomatic or elevated ions
• Lifelong commitment to follow-up

Patients must understand that resurfacing is a historical technique with proven problems, not a superior modern alternative.

Surgical approaches for hip resurfacing:

Posterior approach (most common):

• Patient lateral decubitus
• Standard posterior incision
• Detach external rotators and capsule
• Posterior dislocation of hip
• Excellent femoral head exposure

Advantages:

• Familiar to most surgeons
• Good visualization of femoral head
• Easier to achieve valgus positioning

Disadvantages:

• Disrupts posterior capsule and blood supply
• Higher dislocation risk (mitigated by large head)
• External rotator repair required

Anterolateral (modified Watson-Jones):

• Patient supine
• Interval between TFL and gluteus medius
• Anterior hip capsulotomy
• Anterior dislocation

Advantages:

• Preserves posterior structures
• Lower dislocation risk
• May preserve some blood supply

Disadvantages:

• More difficult femoral exposure
• Risk of abductor damage
• Challenging to achieve valgus position

The posterior approach remains most popular for surgeons still performing resurfacing.

Femoral head preparation technique:

Key steps:

1. Guidewire placement

   • Central in femoral head on AP and lateral
   • Aim for slight valgus (5-10 degrees from anatomic axis)
   • Avoid varus positioning

2. Reaming

   • Spherical reamers to shape femoral head
   • Remove minimal bone
   • Achieve smooth spherical surface
   • Avoid notching anterior femoral neck (critical)

3. Chamfer cutting

   • Chamfer tool to create seating surface
   • Removes peripheral osteophytes
   • Creates landing zone for implant

4. Sizing

   • Trial components to determine size
   • Largest component that fits without overhang
   • Typically 40-60mm diameter

5. Final preparation

   • Drill cement holes if using cemented component
   • Pulse lavage to remove debris
   • Dry bone surface

Femoral component implantation:

Cemented technique (most common):

• Apply cement to bone surface
• Fill chamfer area thoroughly
• Impact femoral component onto prepared head
• Maintain pressure until cement sets
• Remove excess cement
• Avoid cement intrusion into vascular channels

Cementless technique:

• Ensure bone surface prepared to exact size
• Impact component firmly onto bone
• Verify seating on all sides
• Component must be stable

Acetabular component implantation:

Standard cementless technique:

• Ream acetabulum to bleeding bone
• Underream by 1-2mm for press-fit
• Impact acetabular component
• Verify seating and stability
• Add screws if needed for fixation

Critical positioning:

• Inclination 40-45 degrees
• Anteversion 15-20 degrees
• Avoid excessive inclination (edge loading)

Final steps:

• Reduce hip
• Check stability through full range of motion
• Verify no impingement
• Close in layers with capsule repair

Achieving correct component positioning is critical to minimize edge loading and wear.

Common technical errors and how to avoid them:

Detailed complication discussion:

1. Femoral neck fracture (major early complication):

Presentation:

• Sudden onset hip pain
• Unable to weight bear
• Usually within first 2 years (but can occur later)

Risk factors:

• Female gender
• Small femoral head (under 50mm)
• Varus component positioning
• Anterior neck notching
• Pre-existing cysts or AVN
• Osteoporosis

Management:

• Urgent revision to conventional THA
• Remove femoral resurfacing component
• Prepare femoral canal for stem
• Usually requires cemented stem due to bone loss
• Good outcomes if treated promptly

2. ALVAL - Aseptic Lymphocytic Vasculitis-Associated Lesion:

Pathophysiology:

• Type IV delayed hypersensitivity reaction to metal debris
• Lymphocytic and plasma cell infiltration
• Perivascular inflammation and necrosis
• Leads to soft tissue destruction

Presentation:

• Pain (commonest symptom)
• Soft tissue mass (pseudotumor)
• May be asymptomatic with only elevated metal ions
• Can cause nerve compression or muscle necrosis

Diagnosis:

• Elevated blood metal ions (cobalt and chromium over 7 micrograms per L)
• MRI shows soft tissue masses and fluid collections
• Metal artifact reduction sequence (MARS) MRI protocol
• Ultrasound can also show pseudotumors

Management:

• Revision surgery required
• Remove both components (even if acetabulum looks good)
• Thorough debridement of necrotic tissue
• Revise to conventional THA (ceramic or polyethylene bearing)
• Warn patient that soft tissue damage may be permanent

3. Pseudotumor formation:

Characteristics:

• Soft tissue mass from organized inflammatory response
• Can be cystic or solid
• May cause pain, swelling, nerve compression
• Associated with high metal ions

Types:

• Type 1: Fluid-filled cysts
• Type 2: Solid masses
• Type 3: Mixed solid and cystic

Imaging:

• MRI best for detection
• May be large (up to 10cm or more)
• Often posterior to hip

Treatment:

• Revision surgery with pseudotumor excision
• May require extensive soft tissue debridement
• Outcomes variable depending on tissue damage

4. Metal ion elevation:

Monitoring protocol:

• Baseline pre-operative cobalt and chromium
• Check at 6 months post-op
• Then annually lifelong
• More frequent if symptomatic or concerning trend

Interpretation:

• Normal: under 2 micrograms per L
• Moderate elevation: 2-7 micrograms per L (monitor closely)
• High: over 7 micrograms per L (consider revision)

Factors causing elevation:

• Component malposition (edge loading)
• Large component size (more surface area)
• Poor component seating
• ALVAL or pseudotumor