Reliability of Ultrasound-Guided One-Point Fixation for Zygomaticomaxillary Complex Fractures.

This study aimed to analyze the precision and postoperative stability of ultrasound guided 1-point fixation on the zygomaticomaxillary buttress for the treatment of zygomaticomaxillary complex (ZMC) fractures. The authors analyzed 24 consecutive patients who underwent ultrasound-guided 1-point fixation for ZMC fractures without separation of the fracture at the frontal process of the zygomatic bone. The authors used titanium plates in the first 6 cases, and biodegradable plates in the remaining 18 cases. The authors obtained computed tomography images preoperatively, and again the first day after surgery (T1) and 6 months after the surgery (T2). The authors calculated vertical change (VC) and horizontal change (HC) of the zygoma on computed tomography. Precision was evaluated with T1 images. Stability was evaluated from T1 to T2, and titanium and biodegradable plates were compared. From T1 images, the mean VC and HC was 0.22° (range, 1.60°-1.08°) and 0.33° (range, 1.86°-1.03°), respectively. From T1 to T2, the mean VC and HC was 0.08° and 0.28°, respectively. Comparing the types of plates, the mean HC in the biodegradable plate group was 0.39°, which was significantly greater than that in the titanium plate group (mean -0.10°). However, as the degree of change was relatively small, this did not pose any clinical problems. Our findings suggest that ultrasound-guided 1-point fixation on the zygomaticomaxillary buttress provides accurate reduction on ZMC fractures without the separation of the frontal process of the zygomatic bone fracture. Sufficient stability was obtained, even with the use of biodegradable plates.

Initial organ distribution and biological safety of Mg2+ released from a Mg alloy implant.

Magnesium (Mg) alloys are considered promising materials for biodegradable medical devices; however, the initial effects and distribution of released Mg2+ ions following implantation are unclear. This is addressed in the present study, using two types of Mg alloys implanted into rats. An in vitro immersion test was first carried out to quantify Mg2+ ions released from the alloys at early stages. Based on these data, we performed an in vivo experiment in which large amounts of alloys were subcutaneously implanted into the backs of rats for 1, 5, 10, and 25 h. Mg2+ accumulation in organs was measured by inductively coupled plasma mass spectrometry. In vivo, blood and urine Mg2+ concentrations were higher in rats receiving the implants than in controls after 1 h; however, the levels were within clinically accepted guidelines. The Mg2+ concentration in bone was significantly higher in the 25 h implanted group than in the other groups. Our results suggest that homeostasis is maintained by urinary excretion and bone accumulation of released Mg2+ ions in response to sudden changes in Mg2+ ion concentration in the body fluid in a large number of Mg alloy implants at the early stages.