Clinical outcomes of cemented distal femur replacements with allpolyethylene tibial components for oncologic indications

BACKGROUND Endoprosthetic distal femoral replacement(DFR)is a well-established salvage procedure following resection of malignant tumors within the distal femur.Use of an all-polyethylene tibial(APT)component is cost-effective and avoids failure due to locking-mechanism issues and backside wear,but limits modularity and the option for late liner exchange.Due to a paucity of literature we sought to answer three questions:(1)What are the most common modes of implant failure for patients undergoing cemented DFR with APT for oncologic indications?(2)What is the survivorship,rate of all-cause reoperation,and rate of revision for aseptic loosening of these implants?And(3)Is there a difference in implant survivorship or patient demographics between cemented DFRs with APT performed as a primary reconstruction vs those performed as a revision procedure?AIM To assess outcomes of cemented DFRs with APT components used for oncologic indications.METHODS After Institutional Review Board approval,a retrospective review of consecutive patients who underwent DFR between December 2000 to September 2020 was performed using a single-institutional database.Inclusion criteria consisted of all patients who underwent DFR with a GMRS®(Global Modular Replacement System,Stryker,Kalamazoo,MI,United States)cemented distal femoral endoprosthesis and APT component for an oncologic indication.Patients undergoing DFR for non-oncologic indications and patients with metal-backed tibial components were excluded.Implant failure was recorded using Henderson's classification and survivorship was reported using a competing risks analysis.RESULTS 55 DFRs(55 patients)with an average age of 50.9±20.7 years and average body mass index of 29.7±8.3 kg/m2 were followed for 38.8±54.9 mo(range 0.2-208.4).Of these,60.0%were female and 52.7%were white.The majority of DFRs with APT in this cohort were indicated for oncologic diagnoses of osteogenic sarcoma(n=22,40.0%),giant cell tumor(n=9,16.4%),and metastatic carcinoma(n=8,14.6%).DFR with APT implantation was performed as a primary procedure in 29 patients(52.7%)and a revision procedure in 26 patients(47.3%).Overall,twenty patients(36.4%)experienced a postoperative complication requiring reoperation.The primary modes of implant failure included Henderson Type 1(soft tissue failure,n=6,10.9%),Type 2(aseptic loosening,n=5,9.1%),and Type 4(infection,n=6,10.9%).There were no significant differences in patient demographics or rates of postoperative complications between the primary procedure and revision procedure subgroups.In total,12 patients(21.8%)required a revision while 20 patients(36.4%)required a reoperation,resulting in three-year cumulative incidences of 24.0%(95%CI 9.9%-41.4%)and 47.2%(95%CI 27.5%-64.5%),respectively.CONCLUSION This study demonstrates modest short-term survivorship following cemented DFR with APT components for oncologic indications.Soft tissue failure and endoprosthetic infection were the most common postoperative complications in our cohort.