What Factors Necessitate Removal of Retained Ballistic Fragments in the Head and Neck?

PURPOSE: The purpose of this study was to estimate the frequency of retained ballistic fragment (RBF) removal and to identify factors associated with an increased risk for RBF removal. To date, there are no studies focused on identifying factors associated with removal of RBFs localized to the maxillofacial region. MATERIALS AND METHODS: Using a retrospective cohort study design, the authors enrolled a sample composed of patients with RBFs localized to the maxillofacial region. The predictor variables included bullet size, location, involvement of bone, involvement of sinus, antibiotics, multiple antibiotics, and multiple locations. The primary outcome variable was RBF retrieval. The secondary outcome variables were timing of operative retrieval, fragment site infection, and migration of RBF. Appropriate uni- and bivariate statistics were computed and logistic regression modeling was used. RESULTS: The sample was composed of 20 patients (mean age, 30 yr; 80% male) and 55% (11 patients) required or desired object removal overall. The number of projectiles ranged from 1 to 19 (total, 48) in the 20 patients. The logistic model identified larger size, final location of bone, final location of soft tissue, and final location of sinus as having a higher probability of removal that was statistically significant (P < .05); however, size was the only variable with a substantial odds ratio (OR; 1.96; P < .05). There was no evidence of migration and a low rate (2.3%) of infection was noted at subsequent follow-up radiography and clinical examination. CONCLUSION: Size was the only statistically significant predictor variable with a substantial OR (1.96; 95% confidence interval, 1.31-3.40; P < .05). There was a low risk of infection even when considering oral pharyngeal contamination and low risk of migration. Further studies could focus on prudent antibiotic use and larger patient populations.

Ion chemistry of 1H-1,2,3-triazole.

A combination of experimental methods, photoelectron-imaging spectroscopy, flowing afterglow-photoelectron spectroscopy and the flowing afterglow-selected ion flow tube technique, and electronic structure calculations at the B3LYP/6-311++G(d,p) level of density functional theory (DFT) have been employed to study the mechanism of the reaction of the hydroxide ion (HO-) with 1H-1,2,3-triazole. Four different product ion species have been identified experimentally, and the DFT calculations suggest that deprotonation by HO- at all sites of the triazole takes place to yield these products. Deprotonation of 1H-1,2,3-triazole at the N1-H site gives the major product ion, the 1,2,3-triazolide ion. The 335 nm photoelectron-imaging spectrum of the ion has been measured. The electron affinity (EA) of the 1,2,3-triazolyl radical has been determined to be 3.447 +/- 0.004 eV. This EA and the gas-phase acidity of 2H-1,2,3-triazole are combined in a negative ion thermochemical cycle to determine the N-H bond dissociation energy of 2H-1,2,3-triazole to be 112.2 +/- 0.6 kcal mol-1. The 363.8 nm photoelectron spectroscopic measurements have identified the other three product ions. Deprotonation of 1H-1,2,3-triazole at the C5 position initiates fragmentation of the ring structure to yield a minor product, the ketenimine anion. Another minor product, the iminodiazomethyl anion, is generated by deprotonation of 1H-1,2,3-triazole at the C4 position, followed by N1-N2 bond fission. Formation of the other minor product, the 2H-1,2,3-triazol-4-ide ion, can be rationalized by initial deprotonation of 1H-1,2,3-triazole at the N1-H site and subsequent proton exchanges within the ion-molecule complex. The EA of the 2H-1,2,3-triazol-4-yl radical is 1.865 +/- 0.004 eV.