Evaluation methodology for reoperation after intramedullary nailing for femoral shaft fracture: A quantitative computer tomography-based finite element analysis

Abstract

AIM: In a few cases of intramedullary nailing for femoral shaft fractures, nonunion due to insufficient fixation has been experienced. Although good results have been reported with the exchange nailing and the plate augmentation for reoperation, no method has been established to quantitatively evaluate postoperative instability, and it is not clear how the mechanical condition, including callus, is improved. In this study, Quantitative CT-based finite element analysis was used to quantify postoperative instability and to evaluate the mechanical effects of reoperation.

MATERIALS AND METHODS: A reoperation model (exchange nailing and plate augmentation) was created in addition to the actual surgery model using a CT of a patient who had an intramedullary nailing for a femoral shaft fracture. Finite element analysis was performed to evaluate the tensile failure risk of the callus at the fracture site, which is considered to contribute significantly to bone union.

RESULTS: In the actual surgery model with 11 mm diameter nails, 11.4% of callus showed tensile failure under axial loading of 3 times body weight, but this was reduced to 6.5% when the nail was changed to 13 mm diameter and 5.8% with the augmentation of a 5-hole plate.

CONCLUSION: The augmentation plate on the lateral side was mechanistically shown to promote union similar to exchange nailing.