A Finite Element Model to Simulate Femoral Fractures in Calves: Testing Different Polymers for Intramedullary Interlocking Nails

• Published in: Veterinary surgery 2012-10, Vol.41 (7), p.838-844
• Main Authors: Rodrigues, Luciano B., Las Casas, Estevam B., Lopes, Daniel S., Folgado, João, Fernandes, Paulo R., Pires, Eduardo A. C. B., Alves, Geraldo Eleno S., Faleiros, Rafael R.
• Format: Article
• Language: English
• Subjects: Animals; Biocompatible Materials; Biomechanical Phenomena; Bone Nails - veterinary; Cattle; Cattle - injuries; Femoral Fractures - pathology; Femoral Fractures - veterinary; Finite Element Analysis; Fracture Fixation, Intramedullary - methods; Fracture Fixation, Intramedullary - veterinary; Fractures; Legs; Materials Testing; Models, Biological; Orthopedics; Polymers; Veterinary medicine
• ISSN: 0161-3499; 1532-950X
• DOI: 10.1111/j.1532-950X.2012.01032.x

Objective To verify if the finite element method can correctly estimate the performance of polyacetal and polyamide 6 intramedullary nails in stabilizing a femoral fracture in calves and to estimate the performance of a polypropylene nail in same conditions. Study Design Computational and experimental study. Sample Population Finite element models (FEMs). Methods Based on a 3‐dimensional finite element method (FEM) of the femoral diaphysis, 3 models were constructed to simulate an oblique simple fracture stabilized by an intramedullary nail composed of 1 of 3 distinct polymers. Models were tested under 6 loading conditions that simulated a static calf or a calf in different walking phases. Maximum bone and implant stresses were compared to yield and rupture stresses of specific materials. Results Under static conditions, all polymers were resistant to critical deformation and rupture because maximum von Mises stresses were lower than the respective yield and rupture stresses. However, during walking, maximum stresses exceeded the yield and rupture limits of the polymers, in agreement with a previous in vivo study, which used polyacetal and polyamide nails. Conclusions FEM correctly estimated that polyacetal and polyamide 6 nails would fail to immobilize an oblique femoral diaphyseal fracture in calves that were allowed to walk freely during the early postoperative period. FEM can be useful in the development of new bovine orthopedic devices.