Risk of endoprosthetic infection and impact of health-related quality of life in patients with osteosarcoma and giant cell tumor of bone; a retrospective case-control study

Background: Prosthetic joint infection (PJI) is a major cause of implant failure among patients who have undergone limb salvage surgery with metallic endoprosthesis for oncologic indications. There is no consensus on the best treatment approach for infection of well-fixed implants and the impact of infection on health-related quality of life (HRQoL) is not known in this patient population. Methods: We performed a retrospective case-control study to (I) review our overall infection rate and evaluate the limb salvage rates following treatment with an implant exchange, spindle retention and IV antibiotics, (II) determine if there were any predictors of infection and (III) determine HR-QoL outcomes in oncologic patients who developed PJI. Cases were identified as oncologic patients who had undergone reconstruction at the distal femur with a Compress (Zimmer-Biomet, Warsaw, IN) rotating hinged knee replacement that was complicated by a deep infection requiring a one or two-stage exchange and IV antibiotics who had minimum two-year follow-up data. Controls were matched for oncologic diagnosis, gender and age at initial surgery +/- 5 years. Demographics, infectious agent, treatment and treatment outcome were extracted from the electronic medical record. Patients completed the TESS and EQ-5D to evaluate HRQoL. Results: Over a 20-year period, PJI was diagnosed in 22 of 154 patients who underwent distal femur reconstruction with the compress endoprosthesis. Half of the infections occurred beyond 24 months. Eight different organisms were identified with staph species being the most common (61%). Twelve patients with available medical records and minimum two-year follow-up were identified as cases and matched with 24 controls. Seventy-five percent of cases and controls had a diagnosis of osteosarcoma and 25% had giant cell tumor of bone. No risk factors for infection were identified though a larger proportion of infected patients received an expandable implant (42% vs. 21%, OR 2.0; 95% CI, 0.4-11.1). Limb salvage was achieved in 67% of the infected cases treated with surgical debridement, one or two-stage exchange with Compress spindle retention and IV antibiotics. However, 45% required chronic suppressive oral antibiotics. Twelve patients completed the HR-QoL questionnaires and did not report lower HR-QoL compared to uninfected controls with an average EQ5D-VAS of 0.89 versus 0.82 (P=0.16) and TESS score of 76.6 versus 78.2 (P=0.85) respectively. Conclusions: Our results are promising, suggesting that spindle retention during two-stage exchange does not adversely affect limb salvage rates or HRQoL outcomes.