Patellar Reconstruction With a Trabecular Metal-Backed Component and Screw Fixation: A Preliminary Case Series

Limited patellar bone stock in revision total knee arthroplasty (TKA) may compromise fixation. Trabecular metal (TM)-backed components have been proposed to obtain long-term fixation. However, current fixation techniques (i.e., sutures) have limitations. Thus, we sought to evaluate survivorship of porous TM-backed patellar components affixed with a novel method of mini fragment screw fixation in the setting of limited patellar bone stock.

We conducted a retrospective chart review of all TM-backed patellae affixed with mini fragment screws during revision TKA by the senior authors from March 25, 2020, to May 20, 2022 (22 patellae, 21 patients). Demographics, TM-backed patellae survivorship, radiological status (loosening) of surviving patellae, and TKA reoperations were evaluated. The average follow-up was 3 years (range, one to four).

At the latest follow-up, and despite a high prevalence (82%) of a history of periprosthetic joint infection (PJI), previous revisions (mean, 3.2), and limited preoperative patellar thickness (mean, 7.6 mm), only one TM-backed patella was removed due to infection. All surviving patellae were radiologically stable. There were nine TKAs reoperated: one for supracondylar fracture and PJI; another for patellar subluxation/PJI/ruptured tendon; four for PJI; one for femoral component loosening; another for femoral component loosening and PJI; and one for a defect in the medial parapatellar arthrotomy. Nevertheless, intraoperatively, TM-backed patellar components were deemed well-fixed and were retained.

The TM-backed patellar components affixed with mini fragment screws have excellent short-term survivorship in the setting of limited bone stock. Further investigations with longer follow-ups and better levels of evidence are needed to ascertain the mid- and long-term outcomes of this particular construct.