Debate surrounds the optimum operative treatment of periprosthetic distal femoral fractures (PDFFs) at the level of well fixed femoral components; lateral locking plate fixation (LLP-ORIF) or distal femoral replacement (DFR). To determine which attributed the least peri-operative morbidity and mortality we performed a retrospective cohort study of 60 consecutive unilateral PDFFs of Su types II (40/60) and III (20/60) in patients ≥60 years; 33 underwent LLP-ORIF and 27 underwent DFR. The primary outcome measure was reoperation. Secondary outcomes included perioperative complications and functional mobility status. Kaplan Meier survival analysis was performed. Cox multivariable regression analysis identified risk factors for reoperation after LLP-ORIF.

Mean length of follow-up was 3.8 years (range 1.0–10.4). One-year mortality was 13% (8/60). Reoperation rate was significantly higher following LLP-ORIF: 7/33 vs 0/27, p=0.008. For the endpoint reoperation, five-year survival was better following DFR: 100% compared to 70.8% (51.8 to 89.8 95%CI) (p=0.006). For the endpoint mechanical failure (including radiographic loosening) there was no difference at 5 years: ORIF 74.5% (56.3 to 92.7); DFR 78.2% (52.3 to 100), p=0.182). Reoperation following LLP-ORIF was independently associated with medial comminution: HR 10.7 (1.45 to 79.5, p=0.020). Anatomic reduction was protective against reoperation: HR 0.11(0.013 to 0.96, p=0.046). When inadequately fixed fractures were excluded differences in survival were no longer significant: reoperation (p=0.156); mechanical failure (p=0.453).

Reoperation rates are higher following LLP-ORIF of low PDFFs compared to DFR. Where adequate reduction, proximal fixation and augmentation of medial comminution is used there is no difference in survival between LLP-ORIF and DFR.