Comparison of the Biomechanical Stiffness of Titanium and Sonic Weld RX Osteofixation Systems for Monoblock Zygomaticomaxillary Complex Fractures.

Resorbable osteosynthesis systems are widely used for the fixation of zygomaticomaxillary complex (ZMC) fractures instead of titanium systems, because they do not have postoperative hardware-related complications. However, the strength of conventional resorbable systems is inferior to that of titanium systems. Recently, ultrasound-aided resorbable osteosynthesis systems, which have higher fixation than conventional resorbable osteosynthesis systems, have become available.The purpose of this study was to compare the mechanical stiffness of the ultrasound-aided resorbable and titanium osteosynthesis systems in a cadaveric monoblock ZMC fracture model. Three human cadaveric monoblock ZMC fracture models (6 zygomas) were created. The fixation materials included the titanium (Level One Fixation; KLS Martin, Germany) and ultrasound-aided resorbable osteofixation systems (SonicWeld RX; KLS Martin). The fixation methods included the 3-point (zygomaticofrontal [ZF], zygomaticomaxillary buttress, and inferior orbital rim [Group I]) and the 2-point (ZF + inferior orbital rim [Group IIa] and ZF + zygomaticomaxillary buttress [Group IIb]) fixations. Each fixation model was mechanically tested with a load of up to 100 N, based on the previously reported postoperative masseter muscle strength, and the stiffness was calculated. Titanium was found to be stiffer than SonicWeld RX, though not significantly different. The fixation points in decreasing order of stiffness were Group I, Group IIa, and Group IIb, though the differences were not significant. In conclusion, the 2-point fixation, including the ZF fixation with SonicWeld RX, can be used as an alternative to the 3-point titanium fixation, which is considered to be stronger and stiffer.