(P 100) THE ROLE OF CANCER TYPE IN THE DEVELOPMENT OF PERIPROSTHETIC JOINT INFECTION IN DISTAL FEMORAL REPLACEMENT

Author(s)

Othneil N. Sparks, BS (he/him/his)

Medical Student
UCLA DGSOM
Los Angeles, California, United States

Co-Author(s)

Christopher D. Hamad, MD (he/him/his)

Resident Physician
Department of Orthopaedic Surgery, University of California Los Angeles
Los Angeles, California, United States
Kole Joachim, BA

Medical Student
David Geffen School of Medicine at University of California Los Angeles
Atwater, California, United States
AL

Adrian Lin, BS

David Geffen School of Medicine at University of California Los Angeles
Los Angeles, California, United States
SJ

Sumin Jeong, BSN

David Geffen School of Medicine at University of California Los Angeles
Los Angeles, California, United States
AP

Amanda Perrotta, BS MS

David Geffen School of Medicine at University of California Los Angeles
Los Angeles, California, United States
Michael Fice, MD

Department of Orthopaedic Surgery, University of California Los Angeles
Los Angeles, California, United States
Lauren Wessel, MD

Assistant Professor
Department of Orthopaedic Surgery, University of California Los Angeles
Los Angeles, California, United States
Nicholas M. Bernthal, MD (he/him/his)

Associate Professor
University of California Los Angeles
Los Angeles, California, United States
AC

Alexander Christ, MD

Department of Orthopaedic Surgery, University of California Los Angeles
Los Angeles, California, United States

Objective: Periprosthetic joint infection (PJI) is the second most common and devastating complication following endoprosthetic reconstruction, often necessitating hardware explantation, cement mantle removal, prolonged antibiotics, and potential amputation. Oncologic patients are often presumed to be at elevated risk due to chemotherapy-induced immunosuppression and tumor-driven immune modulation. We hypothesized that primary oncologic diagnosis may influence PJI risk following distal femoral replacement (DFR).

Methods: We retrospectively reviewed 175 patients who underwent DFR at a single center between 1990 and 2022. PJI was defined according to Henderson failure mode of classification (Type IV). Demographic, oncologic, and surgical variables were extracted, including age, sex, primary oncologic diagnosis, chemotherapy exposure, radiation therapy, and prior revision surgery. Univariate analyses were performed using Fisher's exact tests for categorical variables and t-tests for continuous variables. Cox proportional hazards regression was used to model time to PJI, with follow-up time defined as time from surgery to PJI occurrence (for events) or last clinical follow-up (for censored observations). Variables with complete separation (zero events in certain categories) were noted in the analysis. The final multivariable Cox model included age, sex, cancer type, prior revision surgery, chemotherapy, and radiation therapy.

Results: Among 161 oncologic patients (mean age 30.6 years) who underwent distal femoral replacement (DFR), 8.7% developed periprosthetic joint infection (PJI) over a mean follow-up of 42.6 months. Over half (54.7%) received chemotherapy, and 11.3% had radiation therapy. PJI rates varied by tumor type, with the highest rates in Ewing sarcoma (40%) and chondrosarcoma (25%), followed by soft tissue sarcomas (16.7%) (p=0.047). Significant risk factors for PJI included older age, osteosarcoma, Ewing sarcoma, soft tissue sarcomas, and prior revision surgery (all with p< 0.05). Sex, chemotherapy, and radiation therapy were not significantly associated with PJI risk in the time-to-event analysis.

Conclusion: Prior revision surgery, age, osteosarcoma, Ewing sarcoma, and soft-tissue sarcomas were identified as factors associated with increased risk of PJI following DFR in time-to-event analysis. These findings suggest potential biological or malignant tumor characteristics that increase PJI susceptibility and underscore the need for future risk stratification in oncologic arthroplasty.