Comparison of Stress Zones in Finite Element Models of Deformed Bovine Claw Capsules

A finite element model to simulate femoral fractures in calves: testing different polymers for intramedullary interlocking nails

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.