Fig 1.
Virtual reconstruction planning with a custom-made, newly developed software tool.
Patient specific 3D models of mandibula and fibula are used. (a) Resection planes are adjusted freely for the mandible by the surgeon. (c) Fibula segments are automatically projected into (b) the defect and can be adjusted for optimal harvesting site.
Fig 2.
Patient specific, topology optimized osteosynthesis plates (TOPOS-implants).
(Top) Virtual planning and fitting of the osteosynthesis plates for the fixation of the fibular segments. (Bottom) Application of the implants to the specimen produced with electron beam melting.
Fig 3.
Process from bone to reconstruction.
Stepwise process of creating the reconstruction specimen with topology optimized patient specific implants from the intact bone to the reconstructed mandible for testing. An experienced surgeon performed virtual planning and reconstruction. For reconstruction with miniplates the steps are similar but without the implant fitting.
Fig 4.
Biomechanical test setup for dynamic and static testing.
(a) test setup for dynamic testing of the constructed specimen, force is applied through the cables fixed to the ramen mandibulae (b) front view of the dynamic test setup with an exemplary reconstruction using miniplates (c and d) static testing of the reconstruction in the same test rig as for dynamic testing with additional displacement sensors measuring (c) the vertical displacement on the mandible (red circle) at the contact plane of the fibula segments and (d) the lateral displacement at the ramen mandibulae.
Fig 5.
Measurement of the cortical thickness of the mandible at the resection plane of the right mandibular angle.
Measurement of the cortical thickness of the mandible according to Heibel et al. [34].
Fig 6.
Graphical visualization of the biomechanical comparison of miniplates with patient specific, topology optimized (TOPOS-)implants. The bars show the average of the passed cycles per group with 500 000 cycles at maximum. For comparing of fatigue properties of the implant types only test runs without bone fracture are used (statistics: significant (*) p<0.05, highly significant (**) p<0.01).
Fig 7.
Failure cases of the biomechanical testing.
Bone fracture occurred at the right mandibular angle with the fracture line running across the upper fixation screws for (a) miniplates (two views) and (b) TOPOS-implants (two views); (c)Failure of the implant only occurred for reconstructions with miniplates at both fixation sites of the mandibular segment to the fibular segment(left: left mandibular segment to central fibular segment; right: right mandibular segment to right fibular segment).
Table 1.
Measurement results of the cortical thickness of the mandible for all specimen (mean ± standard deviation).