[home] [Personal Program] [Help]

---

Session: Poster session I
Session starts: Thursday 24 January, 15:00

---

Florieke Eggermont (Orthopaedic Research Laboratory, Radboud Institute for Health Sciences, Radboud university medical center, Nijmegen, The Netherlands)
Yvette van der Linden (Department of Radiotherapy, Leiden University Medical Center, Leiden, The Netherlands)
Loes Derikx (Orthopaedic Research Laboratory, Radboud Institute for Health Sciences, Radboud university medical center, Nijmegen, The Netherlands )
Marianne de Jong (Radiotherapeutic Institute Friesland, Leeuwarden, The Netherlands)
An Snyers (Department of Radiation Oncology, Radboud Institute for Health Sciences, Radboud university medical center, Nijmegen, The Netherlands )
Tom Rozema (Department of Radiotherapy, Institute Verbeeten, Tilburg, The Netherlands)
Nico Verdonschot (Orthopaedic Research Laboratory, Radboud Institute for Health Sciences, Radboud university medical center, Nijmegen, The Netherlands; Laboratory of Biomechanical Engineering, University of Twente, Enschede, The Netherlands)
Esther Tanck (Orthopaedic Research Laboratory, Radboud Institute for Health Sciences, Radboud university medical center, Nijmegen, The Netherlands)

Abstract:
Cancer patients with bone metastases have an increased risk of fracturing their femur. Treatment is based on the impending fracture risk: patients with a high fracture risk are considered for prophylactic surgery, whereas low fracture risk patients are treated conservatively with radiotherapy to decrease pain. Current clinical guidelines suggest to determine fracture risk with x-rays, but that appears to be non specific (sensitivity=86%, specificity=58%, PPV=23%, NPV=97%).[1] Therefore, we developed a patient-specific finite element (FE) model that has shown to be able to predict fracture risk in an experimental setting.[2] The aim of this study was to determine if these finite element models improve current fracture risk prediction in patients with bone metastases. 66 patients (76 femurs treated with radiotherapy) affected with predominantly lytic bone metastases were included from four radiotherapy institutes in the Netherlands. Most patients were low risk and received 8 Gy. Some intermediate risk patients were too fragile to undergo prophylactic surgery and received 20 Gy in 5 fractions. CT scans were made and patients were followed for six months to determine whether or not they fractured their femur. Non-linear isotropic FE models were created with the patient-specific geometry and bone density obtained from the CT scans, and in the FE simulation, an axial load was applied to the models simulating stance. Failure loads normalized for bodyweight (BW) were calculated for each femur and were compared between the fracture and non-fracture groups. Subsequently, a threshold defining high and low fracture risk was determined and diagnostic accuracy values were calculated. Femurs of ten patients fractured during follow-up. Median failure loads significantly differed between the fracture and non-fracture groups (5.2xBW and 8.4xBW, respectively, p<0.001). The threshold resulting in the highest sensitivity and specificity was 7.5xBW. Sensitivity was 100%, specificity was 70%, and positive (PPV) and negative predictive values (NPV) were 33% and 100%, respectively. This study showed that patient-specific FE models can aid in predicting fracture risk in patients with lytic femoral bone metastases, showing higher sensitivity and specificity compared to current clinical guidelines. We are initiating a pilot for clinical implementation of the FE model. References [1] Van der Linden et al, J Bone Joint Surg Br 86:566-573, 2004. [2] Derikx et al, J Bone Joint Surg Br 94:1135-1142, 2012.