Background:No widely accepted view or criteria currently exist concerning whether or not patellar replacement (resurfacing) should accompany total knee arthroplasty for osteoarthritis of the knee.1)2)3)Objectives:We recently devised our own criteria for application of patellar replacement and performed selective patellar replacement in accordance with this set of criteria. The clinical outcome was analyzed.Methods:The study involved 1150 knees on which total knee arthroplasty was performed between 2005 and 2019 because of osteoarthritis of the knee. The mean age at operation was 73, and the mean postoperative follow-up period was 91 months. Our criteria for application of patellar replacement are given below. Criterion A pertains to evaluation of preoperative clinical symptoms related to the patellofemoral joint: (a) interview regarding presence/absence of pain around the patella, (b) cracking or pain heard or felt when standing up from a low chair, (c) pain when going upstairs/downstairs. Because it is difficult for individual patients to identify the origin of pain (patellofemoral joint or femorotibial joint), the examiner advised each patient about the location of the patellofemoral joint when checking for these symptoms. Criterion B pertains to intense narrowing or disappearance of the patellofemoral joint space on preoperative X-ray of the knee. Criterion C pertains to the intraoperatively assessed extent of patellar cartilage degeneration corresponding to class 4 of the Outerbridge classification. Patellar replacement was applied to cases satisfying at least one of these sets of criteria (A-a,-b,-c, B and C). Postoperatively, pain of the patellofemoral joint was evaluated again at the time of the last observation, using Criterion A-a,-b,-c.Results:Patellar replacement was applied to 110 knees in accordance with the criteria mentioned above. There were 82 knees satisfying at least one of the Criterion sets A-a,-b,-c, 39 knees satisfying Criterion B and 70 knees satisfying Criterion C. (Some knees satisfied 2 or 3 of Criteria A, B and C).When the pain originating from patellofemoral joint (Criterion A) was clinically assessed at the time of last observation, pain was not seen in any knee of the replacement group and the non-replacement group.Conclusion:Whether or not patellar replacement is needed should be determined on the basis of the symptoms or findings related to the patellofemoral joint, and we see no necessity of patellar replacement in cases free of such symptoms/findings. When surgery was performed in accordance with the criteria on patellar replacement as devised by us, the clinical outcome of the operated patellofemoral joint was favorable, although the follow-up period was not long. Although further follow-up is needed, the results obtained indicate that selective patellar replacement yields favorable outcome if applied to cases judged indicated with appropriate criteria.References:[1]The Effect of Surgeon Preference for Selective Patellar Resurfacing on Revision Risk in Total Knee Replacement: An Instrumental Variable Analysis of 136,116 Procedures from the Australian Orthopaedic Association National Joint Replacement Registry.Vertullo CJ, Graves SE, Cuthbert AR, Lewis PL J Bone Joint Surg Am. 2019 Jul 17;101(14):1261-1270[2]Resurfaced versus Non-Resurfaced Patella in Total Knee Arthroplasty.Allen W1, Eichinger J, Friedman R. Indian J Orthop. 2018 Jul-Aug;52(4):393-398.[3]Is Selectively Not Resurfacing the Patella an Acceptable Practice in Primary Total Knee Arthroplasty?Maradit-Kremers H, Haque OJ, Kremers WK, Berry DJ, Lewallen DG, Trousdale RT, Sierra RJ. J Arthroplasty. 2017 Apr;32(4):1143-1147.Disclosure of Interests:None declared
A Scale-Critical Trapped Surface Formation Criterion: A New Proof Via Signature for Decay Rates
