The primary stability of different implants for intra-articular calcaneal fractures: an in vitro study

Abstract

BackgroundCalcaneal fractures account for around 2% of all fractures and most of them are intra-articular fractures. Many implants have been used in the fixation of calcaneal fractures, but their biomechanical stability has not yet been well investigated. The aim of this study was to compare the primary stability of four fixations of calcaneal fracture.MethodsEight cadaveric calcaneus samples were used to simulate the Sanders’ types III fracture pattern and fixed through four different implants, namely, K-wires, cannulated screws (CS), absorbable screws (AS), and plate-screw system (PSS). Each specimen was then placed into a custom-made jig and was loaded through a material testing machine to simulate the physiological condition. The primary stability was measured in the vertical direction as the stiffness and anterior–posterior direction as the calcaneocuboid force. One-way analysis of variance was used for data analysis.ResultsThe results showed the highest stiffness of 634 (383–891; SD 226) N/mm in the intact model. It was significantly higher than the models fixed with K-wires, CS or PSS. There was no significant difference in vertical stiffness between fractures fixed with AS and the intact model or other fixed models. The intact model showed the lowest calcaneocuboid force of 153 (120–218; SD 39) N, while the fractures fixed with AS showed the greatest force of 242 (146–398; SD 84) N. The significance was only detected between these two models.ConclusionsThe global stiffness was similar when the calcaneal fractures were fixed by K-wires, CS and PSS. The stability of the AS fixation differed along both the vertical and anterior–posterior directions, and was greatly influenced by the bone quality. AS for fracture fixation should be designed with greater strength and pull-out resistance.

Computational Biomechanical Analysis of Postoperative Calcaneal Fractures with Different Placement of the Sustentaculum Screw

“…The finite element model of the calcaneus simulating the one‐leg standing phase was validated as follows. The finite element model predicted the highest vertical construct stiffness of the intact calcaneus (618 N/mm under 650 N vertical loads) was nearly coincident with the construct stiffness of the cadaveric experiment (634 N/mm under 700 N vertical loads) from the published study. The FEA showed the locking plate fixation for the fracture model provided the highest construct stiffness value of 473 N/mm, which was also similar with the stiffness value of 440 N/mm from the cadaveric experiment.…”

“…The construct stiffness of the intact calcaneus model and the fracture model fixed by locking plate fixation was predicted to validate the finite element model. The construct stiffness was compared with the cadaveric calcaneus experiment under the similar experimental conditions of 700 N vertical loads reported by Ni et al .…”

Cannulated screw fixation for dislocated fractures of the calcaneus

“…(17), it was emphasized that percutaneous screw fixation of calcaneus fractures may provide a strength similar to that of plate fixation. Different implants can be used for fracture synthesis and the goal is to achieve enough stability to promote early active range of motion, without weight bearing and redisplacement of the fragments (18,19).…”