Monday, December 24, 2012

Revision Total Hip Arthroplasty Quiz

:  (Resident of Harvard orthopedics program)


[ From connie :Nice summary of the indications and issues surrounding hip revisions.  I have read all of  my post op reports and have never seen a  bone loss classification scheme applied to my revision surgery.  I have to ask about this.  It would seem that if the surgeons used this scheme, it would provide some additional information on the actual bone loss that occurred to the different bones prior to revision?  I also notice that the ilium was not included.  In MoM revisions, you surely loose a good bit of bone in that region.  Not sure why it is not on this list?]

  • Indications
    • osteolysis
    • loosening
    • instability
    • infection
    • mal-alignment
    • polyethylene wear
  • Options include
    • acetabular component revision
    • femoral head and polyethylene exchange
    • femoral component revisions
    • conversion from a hip arthrodesis
  • Complications
    • significantly higher than primary hip reconstruction
    • include
      • dislocation (even is simple procedures)
      • infection
      • nerve palsy
      • cortical perforation
      • fractures
      • DVT
      • limb length inequalities
Classification of Bone Loss
  • Acetabulum
AAOS Classification of Acetabular Bone Loss
Type I (segmental) Loss of part of the acetabular rim or medial wall
Type II (cavitary) Volumetric loss in the bony substance of the acetabular cavity
Type III (combined deficiency)Combination of segmental bone loss and cavitary deficiency
Type IV (pelvic discontinuity) Complete separation between the superior and inferior acetabulum
Type V (arthodesis)Arthrodesis
Proposky Classification of Acetabular Bone Loss
Type IMinimal deformity, intact rim
Type IIASuperior bone lysis with intact superior rim
Type IIBAbsent superior rim, superolateral migration
Type IICLocalized destruction of medial wall
Type IIIABone loss from 10am-2pm around rim, superolateral cup migration
Type IIIBBone loss from 9am-5pm around rim, superomedial cup migration
  • Femur
AAOS Classification of Femoral Bone Loss
Type I (segmental)Loss of bone of the supporting shell of femur
Type II (cavitary)Loss of endosteal bone with intact cortical shell
Type III (combined)Combination of segmental bone loss and cavitary deficiency
Type IV (malalignment)Loss of normal femoral geometry due to prior surgery, trauma, or disease
Type V (stenosis)Obliteration of the canal due to trauma, fixation devices, or bony hypertrophy
Type VI (femoral discontinuity)Loss of femoral integrity from fracture or nonunion
Proposky Classification of Femoral Bone Loss
Type IMinimal metaphyseal bone loss
Type IIExtensive metaphyseal bone loss with intact diaphysis
Type IIIaExtensive metadiaphyseal bone loss, minimum of 4 cm of intact cortical bone in the diaphysis
Type IIIbExtensive metadiaphyseal bone loss, less than 4 cm of intact cortical bone in the diaphysis
Type IVExtensive metadiaphyseal bone loss and a nonsupportive diaphysis
  • Symptoms
    • groin pain --> acetabulum
    • thigh pain --> femoral stem
    • start-up pain --> component loosening
    • night pain --> infection
  • Radiographs
    • required views
      • AP pelvis
      • orthogonal views of involved hip
      • full-length femur radiographs
    • additional views
      • pre-operative radiographs
      • immediate post-operative radiographs
      • judet views
        • useful for assessment of columns
  • CT scan
    • useful for determining extent of osteolysis
      • radiographs frequently underestimate extent of osteolysis
    • assessment of component position
  • Laboratory analysis
    • infectious laboratories
      • ESR
      • CRP
      • CBC
  • Aspiration
    • recommended if infectious laboratories are suggestive of infection
  • Femoral revision
    • primary total hip arthroplasty components
      • indications
        • minimal methaphyseal bone loss
    • uncemented extensively porous-coated long stem prosthesis (or porous-coated/grit blasted combination)
      • indications
        • most Paprosky II and III defects
      • outcomes
        • 95% survival rate at 10-years
    • impaction bone grafting (Ling's technique)
      • indications
        • large ectactic canal and thin cortices
      • outcomes
        • most common complication is stem subsidence
    • modular oncology components
      • indications
        • massive bone loss with a non-supportive diaphysis
    • cemented stems
      • indications
        • irradiated bone
        • elderly
        • low-demand patients
      • outcomes
        • high failure rate
  • Acetabular revision
    • porous-coated hemisphere cup secured with screws
      • indications
        • rim is competent (> 2/3 of rim remaining)
    • reconstruction cage with structural bone allograft
      • indications
        • rim is incompetent (<2/3 of rim remaining)
      • outcomes
        • allograft failure is the most common complication
        • high failure rate (40-60%) without reconstruction cage due to component migration after graft resorption
  • Combined revision
    • femoral head and polyethylene exchange
      • indications
        • eccentric wear of the polyethylene with stable acetabular and femoral components
      • outcomes
        • hip instability is the most common complication of isolated liner exchange
    • conversion from a hip arthrodesis
      • indications
        • low back and knee pain as a result of arthrodesis
      • outcomes
        • implant survival greater than 95% at 10 years
        • competence of gluteal musculature is predictive of ambulatory success
Surgical Techniques
  • Femoreal revision with uncemented extensively porous-coated long stem prosthesis
    • technique
      • femoral stem must bypass most distal defect by 2 cortical diameters
        • prevents bending moment through cortical hole
      • cavitary lesions are grafted with particulate graft
      • allograft cortical struts may be used to reinforce cortical defects
  • Femoral impaction bone grafting
    • technique
      • morselized fresh frozen allograft packed into canal
      • smooth tapered stem cemented into allograft
  • Acetabular revision with porous-coated hemisphere cup with screws
    • technique
      • cavitary lesions are filled with particulate graft
      • cup placement should be inferior and medial
        • lowers joint reactive forces
      • metallic wedge augmentation may be used if cup in good position and rigid internal fixation is achieved
      • jumbo cups may be used when larger reamer is needed to make cortical contact
      • structural allografts may be used to provide stability while bone grows into cementless cup
  • Acetabular revision with reconstruction cage with structural bone allograft
    • technique
      • polyethylene cup is cemented into reconstruction cage
      • bone graft placed behind cage
  • Femoral head and polyethylene exchange
    • technique
      • exchange both head and liner
      • osteolytic defects may be bone grafted through screw holes to fill bony defects

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[Following is a quiz with 5 questions.  I thought it was useful to look at this because it gives you a sense for what the surgeon has to figure out when a patient walks in the door with symptoms.  The options are numerous but the right answers are few.  I can just imagine  how difficult it must be for a surgeon attempting to address a problem like MOM hip implants with no real clinical data to go on.  As my surgeon said several years ago:  "Its  all very  murky."  He just didn't know what to do which is why I sought out some consultants who were very familiar with the issues surrounding this problem...which several years ago were few and far between.

This quiz is not about MoM hips so skip this section if the thought process involved in getting to an answer is not of interest to you. The pictures accompanying the commentary are interesting too!




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