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Revision TKR: Revision of Patellar Component:
one should consider not resurfacing the patella if less than 12mm of native bone remains (fx or early loosening may result);
obviously, if sepsis is present then patellar component removal is required;
if patellar component is to be retained, then it is necessary to surgically remove the peripatellar "meniscal" tissue that typically grows around patellar component;
subsequently ensure that there is no patellar loosening;
finally if the patellar component is to be retained, there should be good compatibility with the revision femoral component;
some suggest sewing a remnant of the patellar fat pad into the patella if it is not resurfaceable;
revision patellas are thicker to make up for lost bone and have shorter pegs;
if a primary patellar component is having its peg shortened for use in a revision situation, cut the peg with an oscillating saw away from the wound to prevent a shower of polyethylene particles;
following revision, the patellar height should be around 24-26 mm;
in the report by Hanssen AD, the author describes the surgical technique and early clinical results of an alternative to the conventional treatment options of either patellectomy or retention of the remaining patellar osseous shell;
goals of this procedure were to restore patellar bone stock and potentially to improve the functional outcome;
surgical procedure involves creating a tissue flap secured to patellar rim to contain cancellous bone graft inserted into patellar bone defect;
follow-up was at a mean of 36.7 months (24 to 55 months) after the patellar bone-grafting procedure;
mean preop Knee Society scores for function and pain were 39 points (range, 18 to 82 points) and 40 points (range, 20 to 80 points), respectively;
at the time of final follow-up, the Knee Society function and pain scores had improved significantly, to a mean function score of 91 points (range, 80 to 98 points) and a mean pain score of 84 points (range, 65 to 100 points) (p < 0.05).
point of greatest patellar thickness measured intraoperatively ranged from 7 to 9 mm.
patellar thickness on immediate postoperative Merchant radiographs averaged 22 mm (range, 20 to 25 mm) whereas, at the time of final follow-up, patellar thickness averaged 19.7 mm (range, 17 to 22.5 mm).
