Restore both surfaces.
What did we remove? What did we put back?
What these measurements mean
Femoral reference thickness is sampled from the supplied size 11 Right Persona CAD at six locations relative to fitted dominant internal CAD planes. These reference planes are not yet confirmed manufacturer cutting planes. Internal lands and recesses vary, so surface-to-plane depth is not uniform metal thickness. The separate local metal thickness measures between the first outer and inner CAD intersections along the same ray. The manufacturer technique does not establish these six sample depths as surgical targets. The saved, unmodified illustrative femur supplies the comparison surface; the approved display femur retains its Persona-shaped trochlea. These are model-space comparisons, not patient measurements or evidence of surgical accuracy.
The surface-to-cut depth includes the reconstructed original surface. For surgical specimen measurements, account for cartilage loss and saw kerf before comparison. Added seating thickness is a teaching input, not a cement recommendation. Changing depth translates the rigid femoral component along the selected plane normal; it does not change implant size or validate all five resections. Equal thickness restores the selected local offset, not the entire trochlear shape.
The patella is 19.5 mm thick at its illustrated center. The button is an illustrative dome, not manufacturer CAD. Residual bone and thickness settings are geometry examples, not safe surgical limits. The original outline moves with the patella. Fixed tendon length and sampled contact are retained; motion is not a force solution.
Evidence: under- or overstuffed?
Zimmer Biomet · Persona KA surgical technique: the 9 mm posterior thickness reference must not be transferred to the anterior flange. Confirm anterior resection with the appropriate guide; our fitted reference planes are not manufacturer-verified cutting planes.
Rivière, Howell et al. · Persona trochlear restoration: proximal understuffing with conventional KA; upsizing can introduce overstuffing and overhang elsewhere.
Ito et al. · 94 knees: mean understuffing of 3.1 mm at the flange and 3.9 mm at the chamfer using an anterior-flush technique. Clinical significance remained uncertain.
Shatrov et al. · 122 knees: restoring extension geometry did not ensure restoration in mid or deep flexion.
Howell et al. · KA-optimized design: trochlear peak understuffing was associated with equivalent or better outcomes in this cohort. A geometric mismatch is not automatically a clinical failure.