Total Hip Revision Arthroplasty Techniques - Femoral Revision

Goals:

  • To extract prosthesis with minimal damage
  • To implant a new stem which will be STABLE
  • To manage and augment bone loss

Classification of femoral bone loss:

  • AAOS classification.
  • Type I – Segmental loss.
  • Any loss of cortical shell.
  • Type II – Cavitary loss (cancellous or endosteal cortical loss without violation of the outer shell).
  • IIA – Cavitary loss.
  • IIB – Ectasia (femoral expansion with cortical thinning and complete loss of cancellous stock).
  • Type III – Combined.
  • Type IV – Malalignment.
  • Type V – Stenosis.
  • Type VI – Femoral discontinuity.

Paprosky classification:

This is useful in decision making where an uncemented revision stem is to be used.

  • Type I - Minimal defects with intact metaphysis and diaphysis, and partial loss of calcar or AP bone stock.
  • Type II - Metaphyseal defect with normal diaphsyis, calcar completely absent and major AP bone loss.
  • Type III - Defects of metaphysis and diaphyseal junction.
  • Type III A - Fixation with a fully coated porous stem will be proximal to, or at, the isthmus.
  • Type III B - More distal defect, but fixation will still be achieved (just distal to the isthmus) – need minimum 6cm bone contact (assess stability intra-op).
  • Type IV - Extensive metaphyseal and diaphyseal bone loss and a canal which will not support even a long stem.

Treatment

Paprosky protocol:

  • Type I – As for primary.
  • Type II - IIIB – Fully coated stem with variable degrees of calcar replacement.
  • Type IV – Impaction grafting or allograft-prosthetic composite.

Points to consider:

  • Primary aim is a stable prosthesis.
  • Uncemented stems have better results than cemented stems in the literature.
  • Must obtain axial and rotational stability – micormotion of > 40um will result in fibrous ingrowth.
  • Meticulous femoral bone preparation is crucial - the cancellous bed will be poor (studies show fixation strengths of 70% less than in the primary setting).
  • Meticulous removal of all previous cement or pseudomembrane.
  • All sclerotic areas need to be burred down to “fresh” bleeding or cancellous bone – take care not to perforate though.
  • Rigorous cementing technique if you are going to cement – need good pressurisation
  • A stem longer than 7 inches requires an anterior bow.
  • The apex of the anatomical femoral bow is 7 inches below the LT.

Osseointegration Group of AustraliaNorwest Advanced OrthopaedicsDrummoyne Advanced Specialty ServicesThe Sports & Arthritis Clinic NorwestNorwest Advanced Specialty Services