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CORR Insights®: What Is the Risk of Repeat Revision When Patellofemoral Replacement Is Revised to TKA? An Analysis of 482 Cases From a Large National Arthroplasty Registry.

Partial joint arthroplasty, including patellofemoral replacement (PFR), is an attractive alternative to TKA in patients who have arthritis confined to the patellofemoral compartment. Clinically, partial joint arthroplasties have been associated with shorter hospital stays, faster recovery, better ROM, and a more “normal” feel of the knee [15]. Indeed, the move toward outpatient arthroplasty, the focus on bundled payments, and the expansion of value-based reimbursement all are driving providers to consider use of partial joint arthroplasties more often with more permissive indications. In the current study, Lewis and colleagues [10] studied the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) [2] and found that the most-common reason for revision of PFR to TKA was progression of arthritis to previously uninvolved compartments of the knee. They also found that PFRs revised to TKAs were more likely to undergo repeat revision than were TKAs that underwent revision to a second TKA. Additionally, those knees that had been revised to TKA from a PFR had a survivorship that more closely approached that of a revision TKA than a primary TKA. While the literature on PFRs is limited, there are other reports that also found lower survivorship of PFRs including a meta-analysis that found a more than three-fold annual increased risk of revision for PFR compared to primary TKAs [4]. While other studies have shown high early revision rates [1, 4, 5, 14], the current study represents the first report on the risk of repeat revision of PFRs revised to TKAs. As mentioned, the authors of the current study [10] found the mostcommon reason for a revised PFR was disease progression in the other compartments. Many surgeons argue, however, that these procedures merely delay the eventual TKA and that revisions of PFRs are equivalent to standard primary TKAs [13]; the current study [10] showed this not to be the case. One report on the mid-term survivorship of one PFR design went as far as to say that “conversion to TKR does not and should not be regarded as failure of the index operation” [13]. But to the patient, a return to the operating room is a major event resulting in pain, a second convalescence, and absence from work, likely leading to the view that the initial procedure failed or was a mistake. And, we now have learned that these revisions indeed are nothing like primary TKAs in terms of survivorship [10].