Total Hip Revision Arthroplasty Techniques - Femoral Revision
- 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.
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.
- 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.