LONG-TERM OUTCOMES OF TOTAL KNEE ARTHROPLASTY WITH DISTAL FEMORAL REPLACEMENT FOR NON-ONCOLOGIC INDICATIONS

Distal femoral replacement (DFR) is a valuable salvage option to manage complex revision or primary total knee arthroplasty (TKA) in the setting of massive bone loss. Few studies report mid to long-term outcomes of DFR for non-oncologic indications. The purpose of this study was to report the implant survival of DFR in non-oncologic TKA for the entire cohort and by indication, as well as clinical outcomes. We retrospectively identified all DFR performed for non-oncologic indications from 2002 to 2021 at a single academic center. Three patients with less than two-year follow-up were excluded, none of which underwent a re-revision after the index DFR. Forty-five DFR (45 patients) were included with a mean follow-up from index DFR of 6.6 years (range two-17.2). At time of index DFR the mean age was 75.3 years (range 53.3-93.6), BMI was 29.2 (range 19.4-52.4), and 64.4% (29) were female. Patients had a mean of 2.3 (range one to six) knee surgeries prior to DFR. Indications for index DFR were mechanical failure of prior TKA (40.0%), periprosthetic fracture (33.3%) and periprosthetic joint infection (26.7%). All DFR were rotating hinge design, 43 (95.6%) were the same DFR system, and all had fully cemented stems. Kaplan-Meier analysis was used to determine all-cause implant survival for the entire cohort and by indication, with revision of any prosthesis component as the endpoint. Oxford Knee Scores (OKS) and patient reported satisfaction were collected at most recent follow-up. Fourteen (31.1%) patients underwent revision post index DFR at a mean time to first revision of 2.7 years (range 0.1-12.6). The most common reasons for first revision were infection (seven of 14, 50.0%), fracture (three of 14, 21.4%), and hinge dislocation (two of 14, 14.3%). The all-cause revision-free survival for the entire cohort was 74.6% (95% CI 67.9-81.3) at five-years and 60.2% (95% CI 49.4-70.8) at 10-years. By indication for index DFR, 50% (six of 12) of infection patients underwent a revision, 27.8% (five of 18) of mechanical failure underwent a revision, and 20% (three of 15) of fracture patients underwent revision. The differences in revision-free survival by indication were not statistically different in survival analysis (p=0.221). At final follow-up the mean OKS was 25 (range five to 44) and 68.8% of patients were satisfied with their outcome. Four patients have undergone multiple revisions post DFR and two have undergone an above knee amputation. DFR for non-oncological indications is associated with a high rate of revision, most due to early infection or fracture. The mid- and long-term revision-free survival is poor and patient satisfaction is modest. Differences in survival by indication for index DFR were not statistically significant. DFR remains a valuable salvage procedure, but patients need to be counselled on expected outcomes.