Fresh Core Mapping
Femoral Head
Attempt the first 4 cores at the North, East, West, and South (NEWS) positions of the femoral head.
North: Take the core from the top/superior aspect of the femoral head.
With the North core reamed, use a mallet to drive a small Lambotte osteotome into the lateral aspect of the femoral head (!). Aim for the spot in the femoral head so that the osteotome will intersect with the very bottom of the North core. If successful, you should see the North core "pop up", allowing for easy extraction. The vacant tunnel now present in the top of the femoral head will make extraction of additional cores easier.
East/West: Take a cores from the anterior and posterior sides of the femoral head. These harvest sites should be approximately opposite of each other on the graft. Always extract the core that was just reamed before proceeding to the next harvest site to avoid damaging that core.
South: Take a core from the underside/inferior aspect of the femoral head, just below the fovea capitis. Cores harvested from this location might have thinner or bruised cartilage. If that is the case, use this core as a destructive sample.
Use the Supplier App par levels to decide what size cores will be harvested.
If making both larger and smaller cores from this graft, use the larger size reamer (16mm) for the first 4 cores.
With the 4 NEWS cores extracted, you can now attempt to produce more cores from the cartilage left in-between the first 4 harvest sites.
Even when working with a large diameter femoral head, it is recommended to use a 10mm reamer for any additional cores after the first 4 are extracted.
For the remaining cores, plan your harvest sites carefully to avoid drilling into an existing tunnel.
Again, extract each core immediately after reaming and before attempting to take another core from a different site.
Distal Femur
Cores can be produced from the cartilage surface of the distal femur when:
The condyle(s) do not meet size requirements outlined in the decision matrix.
Defects would prevent the graft from meeting product specifications/grade levels.
Partial condyles will be left over from producing Trochlea or BiCompartment grafts.
Whatever the case, use the Supplier App par levels, condyle width, and graft topography to decide what size cores will be harvested.
*Unless working with a very large graft, it's unlikely a 16mm can be harvested from the trochlear region of the medial condyle.
*You may be able to extract 10mm cores from the spaces in-between 16mm harvest sites.
If making a Trochlea or BiCompartment graft, the partial condyle(s) can be cut away once the cores from these regions have been extracted.
If only taking cores from one condyle and outputting the other as a hemicondyle fresh graft, remove the hemicondyle from the distal femur as shown in Figure 5:
Use a band saw to cut through the trochlea 1. and make another perpendicular cut through the epicondyle 2.
Set the hemicondyle aside 3. and return the remaining condyle and femoral shaft to the vice to begin harvesting cores per figures 3 and 4.
As a general rule, if cores are to be taken from either hemicondyle's trochlear region, the condyles should be separated using a cut through the trochlea first.
This allows for the flush application of the cutting guide against the graft.
Updated on: 16/12/2022
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