An experimental study of a novel external fixator based on universal joints for the rapid initial stabilization of mandibular comminuted fractures.

PURPOSE: Shaping and assembling contemporary external fixators rapidly for the severe mandibular fractures remains a challenge, especially in emergency circumstance. We designed a novel external fixator that incorporates universal joints to provide the stabilization for mandibular comminuted fractures. This study aims to confirm the efficacy of this novel external fixator through biomechanical tests in vitro and animal experiments. METHODS: In vitro biomechanical tests were conducted using 6 fresh canine with mandibular defect to simulate critical comminuted fractures. Three mandibles were stabilized by the novel external fixator and other mandibles were fixed by 2.5 mm reconstruction plates. All fixed mandibles were subjected to loads of 350 N on the anterior regions of teeth and 550 N on the first molar of the unaffected side. The stability was evaluated based on the maximum displacement and the slope of the load-displacement curve. In animal experiments, 9 beagles with comminuted mandibular fractures were divided into 3 groups, which were treated with the novel external fixation, reconstruction plate, and dental arch bar, respectively. The general observation, the changes in animals' weight, and the surgical duration were recorded and compared among 3 groups. The CT scans were performed at various intervals of 0 day (immediately after the surgery), 3 days, 7 days, 14 days, 21 days, and 28 days to analyze the displacement of feature points on the canine mandible and situation of fracture healing at 28 days. The statistical significance was assessed by the two-way analysis of variance test followed by the Bonferroni test, enabling multiple comparisons for all tests using GraphPad Prism10.1.0 (GraphPad Inc, USA). RESULTS: The outcomes of the biomechanical tests indicated that no statistically significant differences were found in terms of the maximum displacement (p = 0.496, 0.079) and the slope of load displacement curves (p = 0.374, 0.349) under 2 load modes between the external and internal fixation groups. The animal experiment data showed that there were minor displacements of feature points between the external and internal fixation groups without statistic difference, while the arch bar group demonstrated inferior stability. The CT analysis revealed that the best fracture healing happened in the internal fixation group, followed by the external fixation and arch baring at 28 days after fixation. The external fixation group had the shortest fixation duration (25.67 ± 3.79) min compared to internal fixation ((70.67 ± 4.51) min, p < 0.001) and arch baring ((42.00 ± 3.00) min, p = 0.046). CONCLUSION: The conclusion of this study highlighted the efficacy and reliability of this novel external fixator in managing mandibular fractures rapidly, offering a viable option for the initial stabilization of comminuted mandibular fractures in the setting of emergency rescue.

A retrospective study to compare the treatment outcomes with and without surgical navigation for fracture of the orbital wall.

PURPOSE: To evaluate the outcomes with and without aid of a computer-assisted surgical navigation system (CASNS) for treatment of unilateral orbital wall fracture (OWF). METHODS: Patients who came to our hospital for repairing unilateral traumatic OWF from 2014 to 2017 were included in this study. The patients were divided into the navigation group who accepted orbital wall reconstruction aided by CASNS and the conventional group. We evaluated the surgical precision in the navigation group by analyzing the difference between actual postoperative computed tomography data and preoperative virtual surgical plan through color order ratios. We also compared the duration of surgery, enophthalmos correction, restoration of orbital volumes, and improvement of clinical symptoms in both groups systemically. Quantitative data were presented as mean ± SD. Significance was determined by the two-sample t-test using SPSS Version 19.0 A p < 0.05 was considered statistically significant. RESULTS: Seventy patients with unilateral OWF were included in the study cohort. The mean difference between preoperative virtual planning and actual reconstruction outcome was (0.869 ± 0.472) mm, which means the reconstruction result could match the navigation planning accurately. The mean duration of surgery in the navigation group was shorter than it is in the control group, but not significantly. Discrepancies between the reconstructed and unaffected orbital-cavity volume and eyeball projection in the navigation group were significantly less than that in the conventional group. One patient had remnant diplopia and two patients had enophthalmos after surgery in the navigation group; two patients had postoperative diplopia and four patients had postoperative enophthalmos in the conventional group. CONCLUSION: Compare with the conventional treatment for OWF, the use of CASNS can provide a significantly better surgical precision, greater improvements in orbital-cavity volume and eyeball projection, and better clinical results, without increasing the duration of surgery.