← Part 3 · Persona resurfacingPART 4 / RESECTION ACCOUNTING

Measure cartilage. Set the cut.

The original articular surface defines the target.

Native knee · extension

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Cut plane & mm ticks Original cartilage envelope

CAD-aligned plane guides; green shows the modeled pre-wear envelope.

Inspect a femoral surface

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Surface close-ups are illustrative; cartilage depth is not measured from this model.

9 MM TOTAL · EACH SURFACE

Measure the unworn side.

Use that thickness to reconstruct the worn side.

Distal femur

Unworn cartilage thickness

Target bone resection— mm

9 mm − cartilage thickness

Posterior femur

Unworn cartilage thickness

Target bone resection— mm

9 mm − cartilage thickness

Assumes matching native cartilage thickness on the worn and unworn sides. Depth is measured beneath exposed bone, with no bone erosion.

Measurement details

Distal and posterior values are independent. These entries calculate bone depth; they do not measure cartilage from the model or change its illustrative green envelope.

If cartilage remains, add its thickness when measuring from the current articular surface. Bone erosion requires a separate correction.

The removed specimen is thinner than the planned cut depth by the saw kerf. For example, 2 mm native cartilage gives a 7 mm bone cut; a 1 mm kerf leaves a 6 mm bone specimen.

Persona technique · resection and saw-kerf accounting. Matching cartilage thickness is the assumption used here.

Continue to Part 5 · Tibial reconstruction →