Search

The Sangre de Cristo Mountains of southern Colorado and northern New Mexico, USA, contain an unusual combination of thick- and thin-skinned contractional structures involving both basement and cover rocks in the Laramide Rocky Mountain foreland. These structures are truncated by down-faulted extensional basins to the east and west. Together with synorogenic sediments, these structures preserve a record of the rise of the Ancestral Rocky Mountains, the Laramide orogeny, and Rio Grande rifting. Laramide structures within the mountains provide clues to processes that link the three events and to necessary conditions for thin-skinned and thick-skinned contractional structures to form together in continental interiors. To examine the full variety of structural styles, a portion of the northern Sangre de Cristo fold-and-thrust belt in Colorado was described and interpreted using geologic maps and structural cross-sections. Stratigraphic relations of the Ancestral Rocky Mountain highlands and basin fill were reconstructed from existing maps. These relations allow identification of faults inherited from the Ancestral Rocky Mountains, differentiation of thrust sheets, and in some cases, estimation of the magnitude of displacement. To examine relations between Laramide thrusts and Rio Grande rifting, kinematic data were collected from a thrust fault adjacent to rift faults. Three thrust fault styles were recognized: thin-skinned basement, thinskinned cover rocks, and thick-skinned basement. Thin-skinned thrusts arising from a hinterland beneath the present San Luis Valley carried sheets of Proterozoic basement rocks northeast over a Laramide foreland. These basement thrusts are interpreted to be faults of the Ancestral Rocky Mountains that reactivated during the Laramide orogeny. The Laramide foreland consists of thin-skinned thrusts and folds in sedimentary cover rocks as young as 49 Ma. Both thin-skinned thrusts in basement and cover rocks are bounded by thick-skinned basement thrusts that moved intermittently throughout the Laramide orogeny. We infer that thin-skinned thrusts form in continental interiors where deformation is focused in weak strata of thick basin fill and in fluid-reaction weakened preexisting faults in basement rocks. Both conditions are met in the Sangre de Cristo Mountains. Basement thrusts adjacent to the San Luis Valley contain evidence of plastic contractional microstructures overprinted by extensional microstructures that may record the transition from Laramide contraction to Rio Grande extension of the crust. [ABSTRACT FROM AUTHOR]

PurposeTo assess the influence of anatomic location on the relationship between computed tomography (CT) number and X-ray attenuation in limited and medium field-of-view (FOV) scans.Materials and methodsTubes containing solutions with different concentrations of K2HPO4 were placed in the tooth sockets of a human head phantom. Cone-beam computed tomography (CBCT) scans were acquired, and CT numbers of the K2HPO4 solutions were measured. The relationship between CT number and K2HPO4 concentration was examined by linear regression analyses. Then, the variation in CT number according to anatomic location was examined.ResultsThe relationship between K2HPO4 concentration and CT number was strongly linear. The slopes of the linear regressions for the limited FOVs were almost 2-fold lower than those for the medium FOVs. The absolute CT number differed between imaging protocols and anatomic locations.ConclusionThere is a strong linear relationship between X-ray attenuation and CT number. The specific imaging protocol and anatomic location of the object strongly influence this relationship.

Introduction : Despite increasing use of antiplatelet agents (APA), little is known regarding the effect of these agents on the orthopedic trauma patient. This study reviews clinical outcomes of patients with pelvic fractures (Pfx) who were using pre-injury APA. Specifically, we focused on the influence of APA on postinjury bleeding, transfusions, and outcomes after Pfx. Methods : Patients with Pfx admitted during a 37-month period beginning January 2006 were divided into APA and non-APA groups. Pelvic injuries were graded using pelvic fracture severity score (PFSS)-a combination of Young-Burgess (pelvic ring), Letournel-Judet (acetabular), and Denis (sacral fracture) classifications. Other clinical data included demographics, co-morbid conditions, medications, injury severity score (ISS), associated injuries, morbidity/mortality, hemoglobin trends, blood product use, imaging studies, procedures, and resource utilization. Multivariate analyses for predictors of early/late transfusions, pelvic surgery, and mortality were performed. Results : A total of 109 patients >45 years with Pfx were identified, with 37 using preinjury APA (29 on aspirin [ASA], 8 on clopidogrel, 5 on high-dose/scheduled non-steroidal anti-inflammatory agents [NSAID], and 8 using >1 APAs). Patients in the APA groups were older than patients in the non-APA group (70 vs. 63 years, P < 0.01). The two groups were similar in gender distribution, PFSS and ISS. Patients in the APA group had more comorbidities, lower hemoglobin levels at 24 h, and received more packed red blood cell (PRBC) transfusions during the first 24 h of hospitalization (all, P < 0.05). There were no differences in platelet or late (>24 h) PRBC transfusions, blood loss/transfusions during pelvic surgery, lengths of stay, post-ED/discharge disposition, or mortality. In multivariate analysis, predictors of early PRBC transfusion included higher ISS/PFSS, pre-injury ASA use, and lower admission hemoglobin (all, P < 0.03). Predictors of late PRBC transfusion included the number of complications, gender, PFSS, and any APA use (all, P < 0.05). Mortality was associated with pelvic hematoma/contrast extravasation on imaging, number of complications, and higher PFSS/ISS (all, P < 0.04). Conclusions : Results of this study support the contention that preinjury use of APA does not independently affect morbidity or mortality in trauma patients with Pfx. Despite no clinically significant difference in early postinjury blood loss, pre-injury use of APA was associated with increased likelihood of receiving PRBC transfusion within 24 h of admission. Furthermore, multivariate analyses demonstrated that among different APA, only preinjury ASA (vs. clopidogrel or NSAID) was associated with early PRBC transfusions. Late transfusion was associated with the use of any APA, complications, higher PFSS, and need for pelvic surgery.