RESUMEN
PURPOSE: The occiput-axis crossing translaminar screw (C2LAM) fixation technique can help avoid vertebral injury, while the inclusion of offset connectors can facilitate implantation. This three-dimensional finite element (FE) study compared the stability of C2LAM using offset connectors (C2LAM + OF) with other methods. MATERIALS AND METHODS: Occipital and cervical spine computed tomography images of a healthy 30-year-old man were selected to build the FE model. Four internal fixation instruments including occiput plate-C2 pedicle (C2P) and pars (C2Pars) screws, as well as C2LAM and C2LAM + OF were applied consecutively to the model respectively to establish four new models, which were subjected to all states of motion and physiological loads to simulate normal movement, including the four kinds of basic activities of human such as flexion, extension, lateral bending, and axial rotation. Physiological measures and comparison included the range of motion (ROM) and stress distribution in the model. RESULTS: ROM between the fixation techniques was comparable, and the stability of the C2LAM + OF fixation technique was similar to that of C2P. Screw entry points, offset connectors and rods were the main stress distribution regions in the C2LAM + OF system. The mean von Mises stress of the inner wall was significantly smaller than that of the outer wall in flexion, extension, and rotation (p < 0.05); however, lateral bending was comparable, indicating a relatively small risk of damage to the inner wall. CONCLUSIONS: The results of this study indicate that the C2LAM + OF fusion technique can provide sufficient stability and can be used as an alternative to C2P under special circumstances.
RESUMEN
BACKGROUND: The success or failure of donation after circulatory death depends largely on the functional warm ischemia time, which is closely related to the duration between withdrawal of life-sustaining treatment and circulatory arrest. However, a reliable predictive model for the duration is absent. We aimed to compare the performance of the Chinese Donation after Circulatory Death Nomogram (C-DCD-Nomogram) and 3 other tools in a cohort of potential donors. METHODS: In this prospective, multicenter, observational study, data were obtained from 219 consecutive neurocritical patients in China. The patients were followed until circulatory death after withdrawal of life-sustaining treatment. RESULTS: The C-DCD-Nomogram performed well in predicting patient death within 30, 60, 120 and 240 minutes after withdrawal of life-sustaining treatment with c-statistics of 0.87, 0.88, 0.86 and 0.95, respectively. The DCD-N score was a poor predictor of death within 30, 60 and 240 minutes, with c-statistics of 0.63, 0.69 and 0.59, respectively, although it was able to predict patient death within 120 minutes, with a c-statistic of 0.73. Neither the University of Wisconsin DCD evaluation tool (UWDCD) nor the United Network for Organ Sharing (UNOS) criteria was able to predict patient death within 30, 60, 120 and 240 minutes after withdrawal of life-sustaining treatment (UWDCD tool: 0.48, 0.45, 0.49 and 0.57; UNOS criteria: 0.50, 0.53, 0.51 and 0.63). CONCLUSION: The C-DCD-Nomogram is superior to the other 3 tools for predicting death within a limited duration after withdrawal of life-sustaining treatment in Chinese neurocritical patients. Thus, it appears to be a reliable tool identifying potential donors after circulatory death.
