Patient specific glass fiber reinforced composite versus titanium plate: A comparative biomechanical analysis under cyclic dynamic loading

OBJECTIVES: Free flap fixation with patient specific titanium (TI) plates is commonly performed after oncologic mandible resection, but plate exposure, osseous nonunion and imaging artefacts are associated complications. The aim of this study was to analyze interfragmentary movements and fatigue behaviour of patient specific titanium plates in comparison to a novel glass fiber reinforced composite (GFRC) plate in vitro.

METHODS: Two polyurethane fibula segments were fixed to a corresponding mandible (Synbone AG, Malans, CH) with a patient specific 2.0 mm titanium plate (DePuy Synthes, Umkirch, Germany and Materialise, Leuven, Belgium) or one of two patient specific GFRC plates with different glass fiber orientation. Plate fixation to the fibula segments was performed with monocortical non-locking screws in all groups. Plate fixation to the mandible was performed with bicortical locking screws in the titanium group and with bicortical non-locking screws in the GFRC groups. Mastication was simulated via cyclic dynamic loading on the left side at a rate of 1 Hz with increasing peak loading (+0.15 N/cycle, Bionix, MTS, Eden Prairie, USA). A three-dimensional optical measuring system (PONTOS 5 M, GOM, Braunschweig, Germany) was used to determine interfragmentary movements between mandible and fibula segments.

RESULTS: Mean plate stiffness of GFRC plates was 431 ± 64 N/mm and 453 ± 70 N/mm versus 560 ± 112 N/mm in the titanium group. No significant differences were found for the number of loading cycles until a vertical displacement of 1.0 mm (p = 0.637) and for vertical displacement over time (p = 0.490). Interosteotomy gap movement differed significantly between titanium and GFRC plates in the right distal (p = 0.001), intermediate (p = 0.006) and left distal gap (p = 0.025).

CONCLUSIONS: CAD/CAM titanium plates with locking screws provide increased stiffness and reduced interosteotomy movements in comparison to CAD/CAM glass fiber reinforced composite plates with non-locking titanium screws. Future studies should evaluate the influence of mechanobiologically optimized fixation systems on bone healing in free flap surgery.