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Updated: Jun 9 2021

Hip Resurfacing

Images
https://upload.orthobullets.com/topic/5032/images/xray.hip.ap.shows resurfacing.small.jpg
https://upload.orthobullets.com/topic/5032/images/femoral neck fx_moved.jpg
https://upload.orthobullets.com/topic/5032/images/xray.hip.ap.shows resurfacing.jpg
https://upload.orthobullets.com/topic/5032/images/bhr.jpg
  • Introduction
    • History
      • prior versions of resurfacing failed in the past due to
        • larger femoral head on polyethylene -> increased volumetric wear -> high osteolysis rate
      • modern resurfacing techniques (approved by FDA in 2006) have made the following changes
        • metal-on-metal components
        • larger femoral head
      • very popular 10 years ago particularly in younger patients due to less femoral bone resection
  • Indications
    • Indications (controversial)
      • patients with advanced arthritis and good proximal femoral bone stock
        • best outcomes in younger males with good bone stock
      • patients with proximal femoral deformity making total hip arthroplasty difficult
    • Contraindications
      • absolute
        • bone stock deficiency of the femoral head or neck
          • e.g., cystic degeneration of the femoral head
      • relative
        • coxa vara
          • increased risk for neck fractures
        • significant leg length discrepancies
          • resurfacing does not allow leg length corrections
        • female sex of child bearing age (controversial)
          • due to fact that metal ions can cross placenta
          • higher overall complication rate 
        • renal failure
          • functional kidneys required to excrete metal ions
  • Advantages & Disadvantages
    • Advantages
      • preservation of femoral bone stock
      • better stability compared to standard small head (22- to 32-mm) THA
      • improved restoration of hip biomechanics with lower risk of limb length discrepancy
      • revision may be easier than an intramedullary THA
    • Disadvantages
      • lack of modularity with inability to adjust length or correct offset
      • requires larger exposure than conventional THA
  • Outcomes
    • Variable outcome findings in the literature (79% to 98% success rate)
    • Better results found in patients young, larger males with excellent bone stock treated for osteoarthritis than for dysplasia or osteonecrosis
    • Some case series have shown survival comparable to conventional THA, while others have reported higher rates of early revision
      • some products have been removed from the market due to early failure
    • More recent prospective trials have shown few differences between resurfacing and THA
  • Complications
    • Periprosthetic femoral neck fracture
      • incidence of 0% to 4% (more common than in THA)
      • most common early complication (within first 3 years) and frequent cause for revision in acute post-operative period (<20 weeks)
      • mechanism thought to be related to osteonecrosis
      • fracture pattern
        • vertical fracture line from neck down to lesser trochanter
      • risk factors
        • femoral neck notching
          • prevent by placing implant in slight valgus (rather than slight varus)
        • osteoporotic bone
        • large areas of preexisting AVN
        • femoral neck impingement (from malaligned acetabular component)
        • female sex
        • varus positioning of femoral component
      • presents as groin pain
      • treatment
        • convert to a primary THA
        • place cerclage wire above lesser trochanter to prevent fracture propagation during stem insertion
    • Implant loosening (aseptic)
      • early loosening of the cemented femoral resurfacing component
    • Heterotopic ossification
      • higher incidence of heterotopic ossification compared to THA (from wider exposure)
    • Metallosis
      • may have elevated metal ion levels (cobalt, chromium, and cobalt-chromium ratio)
      • found in blood and urine from metal debris
      • presentation and laboratory values may mimic infection
        • may present with elevated synovial WBC due to metal debris and corrosion
      • most cases related to edge loading of the implant
    • Dislocation
      • risk is <1% (lower than conventional THA)
    • Pseudotumor
      • risk
        • metal-on-metal implants (like resurfacing)
        • young
        • female sex
      • may be asymptomatic
      • symptomatic patients require revision surgery
      • risk
        • metal-on-metal implants (like resurfacing)
        • young
        • female sex
      • may be asymptomatic
      • symptomatic patients require revision surgery
    • risk
      • metal-on-metal implants (like resurfacing)
      • young
      • female sex
    • may be asymptomatic
    • symptomatic patients require revision surgery
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