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Journal Club

January 2011

Knee Summary - Australian Joint Registry 2010

• September 1999 - December 2009.
  
• 289,274 Knee replacements up to 31 Dec 2009.
  
• Up 40,675 from last year

• Partial 11.7%
  
• Primary total 80%
  
• Revisions 8.4%
  

• 2/3 in Private sector.
  
  • (68.8% in 2009)
    

Primary partial knee replacements

• Types of partial knee replacements
• Unicompartment knee 94.6%
• Patellotrochlear 4.5%
  
• Partial resurfacing 134,
  • 74% < 55 yo.
  • One cap implants (revision 17.9% at 3 years)
    
• Reasons for revision
  1. Progression of disease
  2. loosening
  3. pain
     
• Cumulative Percentage revision
  • Unicompartment KR
    • 2.2% at 1 year
    • 13.4% at 9 years.
      
  • Unispacers. n=40.
    • All revised after 1 year
  • Bicompartmental. n=126.
    • 6.4% revised 1 year due to patellofemoral pain.
      
  • Patella/trochlear. n=1,519.
    • 75.4% females.
    • 1 year revision 22.4%.
    • Causes
      • Progression of disease,
      • loosening.
    • Young males had high rates of revision.
      

Unicompartmental. n=31,884

• up 3,062 from last year however declining in proportion to TKR.
  
• Equal gender distribution.
• Age 55-74.
  
• Components
  1. Oxford3,
  2. ZUK,
  3. Unix.
     
• Cumulative revision at 9 years 13.3%
  
  • Loosening/lysis 49.9%,
  • disease progression 19.6%,
  • pain 12.0%.
    
• Increased risk in young, females
  
  

Primary TKR

• Femorotibial articulation +/- patellar replacement.
• 231,409, up 34,108 from last report.
  
• 83.9% of all knee replacement procedures.
  
• OA 97.1%
  
• Females 57.3%
  
• Age 55-64. 27.3%
  • Increasing use in younger patients.
    
• Majority of replacements are undertaken without resurfacing the patellar
  
  
• Most popular prosthesis
  • based on femoral component.
    
    • Triathalon 13.8%,
    • PFC Sigma 11.4%,
    • LCS 11.0%.
      
  • Combined
    • Nexgen 19.7% (LPS, LPS Flex, LCCK)
      
• 9 year revision rate 5.1%
  
  • Loosening/ lysis 31.3%,
  • infection 22.2%,
  • Patellofemoral pain 14.3%,
  • pain 9.1%,
  • instability 5.5%.
    
    
• Infection dominates revision within first year. (1.3% at 9 years.)
  
• Components revised
  • Tibial and femoral revision 23.3%,
  • patella only replacement 22.0%,
  • insert only exchange 20.5%
    
• Dx.
  
  1. OA,
  2. RA
  • RA has the lowest rate of revision.
  3. other inflammatory arthritis,
  4. AVN.
     
• Age.
  • Younger the higher the revision rate.
  • <55yo four times the rate than a 75yo at 3 years.
    
• Gender
  • Males higher risk of revision.
    
• Outcome by prosthesis characteristics
  
  • Fixed and mobile bearing.
    
    • Fixed bearing have  a lower rate of revision compared to mobile bearing.
      
  • All-polyethylene tibial prostheses
    • higher risk of revision to moulded non modular and fixed modular tibial prosthesis
• Stability
  
  • Posterior stabilised significantly higher risk of revision compared to minimally stabilised.
    
• Patellar resurfacing
  
  • Resurfacing patella is associated with lower risk of revision in first nine years.
    
  • Risk of revision varies between minimally and posterior stabilised prosthesis.
    
  • Posterior stabilised without patella resurfacing has highest risk of revision (829 revised out of 22,463).
    
• Fixation
  
  • There is no difference between cemented and hybrid fixation.
    
  • Risk of revision in first year is less in cemented and hybrid than cementless.
    
  •  After that year the risk is less for uncemented. (After bony ingrowth.)
    
• Prosthesis types.
  
  • 320 femoral and tibial prosthesis combinations in the registry.
    
  • Cemented.
    • Nexgen CR/Nexgen has the lowest cumulative percentage revision at 9 years of 2.9%.
      
  • Uncemented.
    • Advantim/Advantim has lowest at 1.5%
      
  • Hybrid.
    • AGC/AGC 2.7%
      
  • LCS Duofix femoral prosthesis recalled in 2009 had highest revision rate.
    
    
• Demographic
  
  • 24,162 revisions  registered. Up 3,200.
    
  • Type.
    
    • Major 67.4%
      
      • Most common major was tibial/ femoral (48.3%) tibia only (8.2%).
        
    • Minor 32.6%
      
      • Insert only 13.4%,
      • patellar only 10.3%
      • insert and patella 7.3%
        
    • No change in proportion of major, minor, partial since 2003.
      
      
• Age.
  
  • Most revisions in 65-74 yo.
    
  • More common in females.
    
• Aetiology
  
  • Loosening/lysis most common 42.2%
    
    
• Outcomes of first revision in primary unicompartmental knee replacement.
  
  • 2,291. (Infections excluded)
    
  • Lowest risk of re-revision for a revised unicompartmental knee is when it is revised to TKR. (9.8%.)
    
  • Revision to another unicomp fails in 30% at 3 years.
    
  • Uni to uni was most common for insert exchange or major partial revisions of femoral or tibial components.
    
  • Revision rate for uni to total is equivalent to total to total.
    
    
• Outcome of first revision of primary total knee replacement.
  
  • 4,946 (Infections excluded)
    
  • Minor revisions have a similar risk to major partial or major total revisions.
    
  • Femoral only revision has a higher risk of re-revision than tibial/ femoral revision.
    
  • Revising the patella has same risk of re-revision as a major revision.

Prothesis highlighted in Registry with poor results

• Newly identified
  • Genesis II/ Genesis II CR Cementless
    
    • Revision rates 11.0% at 3 years.
    • Two and a half times revision rate compared to all others. (loosening and lysis)
      
  • Opetrak CR
    • 8.1% revision rate. (Patellofemoral pain, Loosening/lysis)