Identifying Risk Factors for Aseptic Loosening and Infection Following Distal Femoral Replacement for Periprosthetic...

Distal femoral replacement (DFR) is increasingly used for periprosthetic distal femoral fractures (PDFFs). Although infection and aseptic loosening are known complications, predictors, particularly of loosening, remain poorly defined in nononcologic populations. This study aimed to identify patient risk factors for aseptic loosening and infection following DFR for PDFF in a nononcologic cohort. Additionally, DFR utilization trends for PDFF were assessed over time.

A retrospective study was conducted using an insurance claims database (2015 to 2023). Aseptic loosening, periprosthetic joint infection (PJI), and DFR for PDFF were identified using side-specific diagnostic and procedural codes. Oncologic patients were excluded. Kaplan-Meier endpoints were diagnosis of aseptic loosening or PJI. Failure was considered a reoperation. Multivariable logistic regressions identified independent risk factors. A total of 1,002 DFRs were included; 85% of patients were women, and 82% were over 65 years of age.

After excluding cases with ipsilateral PJI, aseptic loosening occurred in 6.6% of patients (n = 57), of which 39 (4.6%) underwent reoperation. Men (odds ratio [OR] 4.11) and obesity (OR 2.67) were independently associated with increased odds of loosening. A PJI occurred in 159 patients (15.9%), of whom 103 (10.3%) underwent reoperation. Men (OR 3.50), obesity (OR 2.26), chronic kidney disease (OR 1.56), and anemia (OR 3.33) were independent risk factors for infection. Increasing age was mildly protective for both loosening (OR 0.97) and PJI (OR 0.97). The proportion of PDFFs treated with DFR rose from 0.6% in 2016 to a peak of 1.8% in 2021 before declining to 1.0% in 2023.

Men and obesity increased the odds of loosening, while men, obesity, chronic kidney disease, and anemia increased infection odds following DFR for PDFF. While comorbidities predicted PJI, unmeasured factors such as surgical technique, fixation strategy, and implant design likely contribute to loosening and warrant further investigation.