Previously, we showed that case-specific non-linear finite element (FE) models are better at predicting the load to failure of metastatic femora than experienced clinicians. In this study we improved our FE modelling and increased the number of femora and characteristics of the lesions. We retested the robustness of the FE predictions and assessed why clinicians have difficulty in estimating the load to failure of metastatic femora. A total of 20 femora with and without artificial metastases were mechanically loaded until failure. These experiments were simulated using case-specific FE models. Six clinicians ranked the femora on load to failure and reported their ranking strategies. The experimental load to failure for intact and metastatic femora was well predicted by the FE models (R2 = 0.90 and R2 = 0.93, respectively). Ranking metastatic femora on load to failure was well performed by the FE models (τ = 0.87), but not by the clinicians (0.11 < τ < 0.42). Both the FE models and the clinicians allowed for the characteristics of the lesions, but only the FE models incorporated the initial bone strength, which is essential for accurately predicting the risk of fracture. Accurate prediction of the risk of fracture should be made possible for clinicians by further developing FE models.
The authors would like to thank the clinical experts who were involved in the clinical assessment of the femora. Furthermore, we thank MSc students J. Kalisvaart and H. van den Boomen, technical staff of the Orthopaedic Research Laboratory and the Department of Anatomy for their assistance.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
Supplementary material. Figures showing the Kendall rank correlations between experimental and finite element (FE)-predicted rankings on load to failure for metastatic femora and for the total sets of metastatic and intact femora are available with the electronic version of this article on our website www.bjj.boneandjoint.org.uk
- Received October 12, 2011.
- Accepted April 26, 2012.
- ©2012 British Editorial Society of Bone and Joint Surgery