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Flashcards in TKR complications Deck (21):

What is the risk factors for TKR complications?

  • Obesity
  • prior surgery
  • diabetes
  • inflammatory arthritis


Describe the types of instability?

  • axial instability ( mediolateral)
  • Flexion instability (anterioposterior)


How do you treat axial instability?

  • If flexion and extension are the same
    • thicker tibial liner
  • If flexion and extension asymmetric
    • augmentation & component revision


How do you tx flexion instability?

  • Occurs when flexion gap > than extension gap
  • when femoral component is downsized or moved anterior
  • posterior dislocation is 0.15% of TKR with posterior stabilisation
  • PCL retaining should be revised to posterior- stabilised
  • post stabilised revised if recurrent dislocation


What is the risk of vascular injury?

  • Low incidence
  • stay medial with retractors
  • avoid sharp dissection in post compartment of knee
  • popliteal artery is 9mm posterior to posterior cortex when knee is flexed to 90o
  • if injury suspected consider dropping tourniquet after bone cuts


What is the incidence of nerve palsy?

  • 0.3%
  • increased risk with valgus and/or flexion deformity
  • incidence increases to 3-4% with valgus deformity
  • increase risk if tourniquet >120 mins, preop neuropathy, abberrent retractor placement
  • tx
    • release bandages
    • flex knee
    • AFO


What are the risk factors for post op stiffness?

  • Preop stiffness
    • most important factor ( ultimate motion is +/- 10o
  • large body habitus
  • female
  • extreme varus
  • young pts
  • limited intraop extension
  • poor pt compliance
  • low pain tolerance
  • technical factors
  • post op 
    • infection
    • delayed healing
    • periprosthetic fx
    • complex regional pain syndrome
    • HO


What is the tx for post op stiffness?

  • Manipulation under anaesthesia
    • flexion <90 degrees after first 6 weeks post op
      • risk fx/ extensor mechanism rupture
    • after 3 months post op manipulation assoc with greater risk and lower benefit
  • ​Scar excison, quadricepsplasty, possible revision of components
    • persistent late stiffness
  • CPm not been shown to improve longterm rom or clinical outcomes


What the incidence of extensor mechanism rupture?

  • Patellar tendon rupture is a rare and devastating complication after TKR
  • incidence 0.17-2.5%%
  • Quads tendon rupture is extremely rare 1%
  • tx by reconstruction with an achilles tendon/bone allograft


What is the risk factors for wound complications?

  • Systemic 
    • DM
    • vascular disease
    • RA
    • Certain medication
    • smoking
    • poor nutritional status
    • albumin <3.5g/L
    • Total lymphocyte count <1,500/uL
    • Perioperative anaemia
    • obesity
  • Local factors
    • prevision incision
      • skin bridge >5-6cm
      • avoid crossing previous skin incisions at angle <60 degrees
      • knee deformity
      • skin adhesions
      • poor local blood supply
  • NB nasal oxgyen should be given for first 1-2 days in all at risk pts
  • if drainage occurs longer than 4 days then aggressive surgical mx should be done


What is the risk of metal hypersensitivity?

  • rare
  • nickel found in colbalt- chromium alloy is most important offending agent


What are the risks for formation of Heterophic ossification?

  • Less frequent than after THR
  • Risk factors
    • periosteal stripping off ant femur
      • formation of HO proximal to anterior flange of femoral component
      • leads to tethering of extensor mechanism/quads
    • HO may -> indolent infection
    • following arthrofibrosis
    • male gender
    • Obesity
    • Post traumatic deformity


What is patellar clunk syndrome?

  • rare phenomenon only seen in posterior stabilised TKR 
  • caused by fibrous nodule that forms on posterior surface of quadriceps tendon above the superior pole of patella
  • Pt experience painful pop as knee is extended approx 40o flexion
  • tx by arthroscopic vs open resection of fibrous nodule


What are the risk factors for TKR periprosthetic fx?

  • Femoral notching
    • notching of anterior femur shown to weaken femur but has not been proven to equate with higher rates of supracondylar femur fx
  • RA
  • Steriod therapt tx
  • Osteopenia or osteoporosis
  • neurological disorders


What is the incidence of periprosthetic TKR fx?

  • 0.3-2.5%
  • incidence higher in revision TKR but not estimated stats reported


Name a classification system for periprosthetic TKR fx?

  • Su and Associates
  • type 1 - fx is proximal to femoral component
  • type 2- fx orginates at proximal aspect of the femoral component and extends proximally
  • type 3- any part of the fx line is distal to the upper edge of anterior flange of the femoral component

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What is the tx of type 1 Su peripros fx?

  • Antegrade IM nail
    • intact stable prosthesis with open box design to accomodate nail
  • Retrograde IM nail 
    • intact stable prosthesis with open box design to accomodate nail
  • OIRF with fixed angle device
    • intact stable prosthesis
    • condylar butress plate, locking supracondylar plate, blade plate, dynamic compression plate


what is the tx of type 2 su periprosthetic fx?

  • Retrograde IM nail 

    intact stable prosthesis with open box design to accomodate nail

  • Orif with fixed angle device


What is the tx of type 3 Su periprosthetic fx?

  1. ORIF with fixed angle device
  2. Revision to a long stem prosthesis
    • loose femoral component
    • type 3 with por bone stock


What is the classification for tibial periprosthetic fx?

  • Felix and associates
  • type 1 =fx to tibial plateau
  • type 2= fx adjacent to tibial stem
  • type 3= fx tibial shaft, distal to component
  • type 4= fx of tibial tubercle 

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What is the tx for tibial periprosthetic fx?

  • Non operative
    • casting or bracing
      • non displaced fx with stable prosthesis
  • Operative
    • Long stem revision prosthesis
    • for displaced fx
    • loose component