Comparisons in finite element analysis of minimally invasive, locking, and non-locking plates systems used in treating calcaneal fractures of Sanders type II and type III.

BACKGROUND

Calcaneal fractures are relatively common but complex, while the treatment of these fractures is still controversial. The objective of this study was to compare the biomechanical stability of minimally invasive, locking, and non-locking plating systems used for fixing Sanders type II and type III calcaneal fractures. Finite element analysis was used for comparing the three types of plating systems. This study helped in guiding the clinical management of calcaneal fractures.

METHODS

The CT data acquired from a volunteer was used to construct a finite element model of calcaneus. The fracture lines were made according to Sanders type II (A, B, C) and type III (AB, AC, BC) and six calcaneal fractures models were constructed accordingly. Three fixation methods used in clinical treatment were simulated by design tools (minimally invasive plating with percutaneous screws, Y-size non-locking plating, and locking plating) and then fixed to these fracture models with the help of clinical principles. The single minimally invasive plating fixation was also tested to compare the function of percutaneous screws. Then, the neutral force was applied on established methods. The displacement and presses distribution condition in various plating models were analyzed and compared.

RESULTS

The levels of displacement and compressive press on the bone around fixation or strains on plating were within the physiological limit, indicating that the three methods were suitable for application. Compared with the locked and unlocked plates, the minimally invasive plating caused a relatively lower displacement without the high stress in bone or fixation. The minimum stress in fixation was observed in locking plate as the distribution of stress was concentrated in the anterior part of locking plate.

CONCLUSIONS

The minimally invasive plating method could be a better alternative method in treating Sanders type II and type III calcaneal fractures. The observed stiffness of locking plate was not obviously stronger than unlocked plate.