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Total Hip Revision Arthroplasty Techniques - Exposure
JAAOS Monograph series (Paprowsky).
Exposure
Trochanteric techniques:
1. Trochanteric slide
This is a modification of the direct lateral approach (Hardinge).
The anterior portion of the GT is osteotomised with the insertion of gluteus medius, and origin of vastus lateralis attached to it. This is then reflected anteriorly to expose the femoral metaphysis and acetabulum.
It is reattached by circlage wires passed around the LT.
The opposing forces of the gluteus medius (pulling it superior), and vastus lateralis (pulling it distal), results in inherent stability.
Problems:
- Re-attaching such a small flake of bone – non-union.
- Any limb lengthening may make re-attachment quite difficult.
2. Vastus slide
Essentially this is a subperiosteal peel of the origin of the vastus lateralis, and anterior insertion of gluteus medius.
The incision is in the shape of a question mark.
3. Extended proximal femoral osteotomy
An osteotomy of the anterolateral 1/3 of the proximal femur, including the entire GT.
The abductors and VL remain attached to fragment.
It is carried as distal as necessary to facilitate removal of the implant.
Pre-op templating will show how far this is – the revision stem must be longer than the end of the osteotomy site by at least 4cm or 2 cortical diameters.
Technical tips:
- Elevate the VL from the femur.
- Use a bur to make the distal, transverse limb – round the edges to minimise stress riser.
- Oscillating saw for the vertical limb.
- Re-attach prior to preparation of the revision stem.
- Prior to re-insertion of revision stem place a prophylactic circlage wire around the femur just distal to the distal extent of the osteotomy in order to prevent propagation.
Removal techniques
1. Poly exchange
Always be prepared with equipment for entire acetabular revision in-case the locking mechanism is damaged.
Techniques are;
Implant specific tools.
Drill into the polyethylene.
Split the polyethylene.
2. Cemented acetabular removal
In order to disrupt the bone-cement interface, you usually need to disrupt the implant-cement interface first.
Start superio-lateral edge of the cup.
Pass curved gouges and osteotomes to disrupt the implant-cement interface.
In removing cement be wary of possibility if intrapelvic content adhesion to cement fragments.
3. Cemented cup removal
The aim is to remove the cup with minimal bone loss.
Techniques are;
- Good circumferential exposure. This is essential.
- Passage of curved gouges and osteotomes.
- Be very careful of levering on the cup.
- Large lever arms can be generated. Cup removal with a large number of bone attached is dire. Titanium implants may be cut into quarters using midas-rex type device.
4. Cemented femoral stem removal
Obtain circumferential exposure of shoulder of prosthesis. This is crucial.
May require trimming of any over-hanging trochanter.
Disrupt the implant-cement interface first.
Attach an extraction device and extract the stem.
Piece-meal extraction of all cement.
Remove in a proximal to distal fashion.
Variety of tools:
- Currettes, flexible osteotomes, gouges.
- Use an osteotome to longitudinally split the proximal cement mantle.
- Used curved or flexible osteotomes and gouges to remove cement further down the shaft.
- Burs.
- Drill and screw in tap. Particularly useful in removing the distal cement plug.
- Sequential drilling and reverse hooks.
Supplementary techniques:
- Osseous windows – distal to cement plug.
5. Cementing back into a cement mantle
It is essential in this situation where the cement mantle is not compromised. (For example, Revision for limb length, acetabular revision.)
6. Cementless femoral stem removal
- Removal technique is dependent on the particular stem – need to know where the in growth surfaces are and disrupt these bone-prosthesis interfaces.
- Proximal porous coating - proximal disruption.
- Extensively porous coating - more extensive disruption (diaphyseal).
- Usual principles.
- Proximal exposure.
- Take care and be patient – preserve bone stock.
- Flexible osteotomes.
- “Episiotomy” – useful in proximal porous coated.
- Lift the VL anteriorly at its origin to expose the metaphyseal/diaphyseal junction.
- Use an oscillating saw to make a 10cm longitudinal osteotomy in this region of posterolateral proximal femur.
- Attach the extractor to the stem and make sequential impaction-extraction attempts.
- Extended proximal femoral osteotomy.
- Take down to just distal, to the distal extent of the porous coating.
- Pass a Gigli saw around the proximal stem to disrupt the bond at the calcar.
- Windows at sites of spot-welding.
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