Total Hip Revision Arthroplasty Techniques - Techniques To Restore Bone Stock
This is used in order to create a femoral bone bed which will support a cemented long stem.
- Fully expose the femur.
- Any segmental defects must be converted to contained defects – mesh or strut grafts with circlage fixation.
- Prophylactically circlage wire the femur. It must be able to withstand the significant hoop stresses which need to be generated for this technique to work successfully.
- Insert a thick intramedullary plug at least 2m pass the most distal lytic defect – hold it there by interference fit, and by passing a K-wire transversely beneath it.
- Pass an IM guide-wire down and into the centre of the plug – confirm its central location.
- Use a cannulated system to systematically impact morsellised bone graft chips into the femur, creating a solid endosteal canal.
- Chips should be 3-5mm in size – too small will allow poor fixation.
- Pack the bone in a distal to proximal fashion.
- Final tamp will be 1-2 sizes larger than the stem to be used.
- Remove the IM guide wire.
- Broach in normal fashion.
- Cement the stem in routine fashion – insert cement slightly more liquid than normal.
- Insert a highly polished, collarless, double-tapered stem (Exeter).
- Protected weight bear for 3 months and results are encouraging.
- Main problem is with excessive subsidence.
APC (allograft prosthesis composites) and strut grafts
- Calcar defect > 5cm – if it is < 5cm use a calcar replacing prosthesis.
- Large intra-medullary defect with a thin cortical shell.
- This generally involves applying strut grafts using circlage wires.
- How much load these grafts can then support is controversial; some advocate loading them to encourage their incorporation. Others bypass them (distally fit stems) suggesting that you can’t expect them be true structural supports – most apply this approach.
- Create a step cut at site of junction with the native diaphysis.