Is double-strut fibula ankle arthrodesis a reliable reconstruction for bone defect after distal tibia tumor resection?-a finite element study based on promising clinical outcomes

Abstract

Background: There are different surgical methods for primary malignant tumor located at distal tibia. Previous studies have reported that double-strut fibula ankle arthrodesis is an alternative option. The purpose of this study was to investigate the biomechanical effect of double-strut fibula ankle arthrodesis by finite element analysis (FEA).

Methods: Computer-aided design software was used to establish three-dimension models. Three different models were constructed: normal tibia-fibula-talus complex (model A), double-strut fibula ankle arthrodesis (model B), and reconstruction by ipsilateral fibula (model C). We used FEA to evaluate and compare the biomechanical characteristics of these constructs. Simulated load of 600 N was applied to the tibial plateau to simulate balanced single-foot standing. Output results representing the model von Mises stress and displacement of the components were analyzed.

Results: Construct stiffness was increased when the internal plate fixation was used. For axial load, model B (1460.5 N/mm) was stiffer than the construct of model A (524.8 N/mm), and model C (636.6 N/mm), indicating model B was more stable. Maximum stress on the fibular graft occurred on the proximal end. The von Mises stress and stress distribution of fibular graft in model B (71.4 MPa) and model C (67.8 MPa) were similar. In model B, the ipsilateral fibula in model B has a higher value of stress (16.1 MPa) than that in model A (0.5 MPa), indicating the ipsilateral fibula shared load after fusion with talus.

Conclusions: Our computational findings suggest that double-strut fibula ankle arthrodesis is an acceptable construct for distal tibia defect and the ipsilateral fibula shares load after fusion with talus.

Keywords: Bone tumor; Distal tibia; Fibular graft; Finite element analysis.

Fig. 1

a Preoperative X-ray film shows osteosarcoma of distal tibia. b Intraoperative photo shows that a non-vascularized fibula transfer harvested from unaffected limb restore the tibial continuity, which parallels to the ipsilateral fibula. Fixation was carried out by plate and screws. The talus and ipsilateral fibula were fused. c Postoperative X-ray film

Fig. 2

3D models for simulation calculation. (a) Normal tibia-fibula-talus complex, (b) double-strut fibula ankle arthrodesis, and (c) reconstruction by ipsilateral fibula—centralization of the ipsilateral fibula

Fig. 3

Tetrahedron volume-mesh models

Fig. 4

The pictures indicate stress distribution in the three groups of models when a vertical compressive force of 600 N corresponding the body weight of a person weighing 60 kg was applied to the tibial plateau

Fig. 5

The pictures show the displacement distributions when a vertical compressive force of 600 N was applied to the tibial plateau

Fig. 6

The maximum VMS of implant in model B was 203.14 MPa and was decreased by 13.8% compared to that in model C (235.6 MPa) (group 1)

Fig. 7

There were no obvious differences in VMS and stress distribution of fibular graft in model B (22.73 MPa) and model C (23.69 MPa). The maximum displacement at the fibular graft in model B (0.37mm) was less than that in model C (0.82 mm) (group 1)

Fig. 8

The ipsilateral fibula in model B has a higher value of stress (12.07 MPa) than that in model A (0.67 MPa), indicating the ipsilateral fibula shared load after fusion with talus (group 1)