Radiologic diagnosis of traumatic occipitovertebral dissociation: 1. Normal occipitovertebral relationships on lateral radiographs of supine subjects.

OBJECTIVE: The objective of this study was to establish a reliable method of determining the normal occipitovertebral relationship seen on lateral radiographs of the cervical spine in supine subjects in order to recognize alterations of normal that characterize occipitovertebral dissociation. MATERIALS AND METHODS: We define the rostral extension of the posterior cortex of the axis body as the posterior axial line, the distance between the basion (tip of the clivus) and the posterior axial line as the basion-axial interval, and the distance between the basion and the rostral tip of the dens as the basion-dental interval. The basion-axial interval was measured on horizontal-beam lateral radiographs of the cervical spine obtained at a 40-in. (1-m) target-film distance in 400 adults who had no occipitovertebral abnormalities. The basion-dental interval was measured in 374 (94%) of the same cohort of adults in whom the superior cortex of the dens could be identified. All radiographs were obtained with the subjects supine. The excursion of the basion referable to the posterior axial line was determined on lateral flexion and extension radiographs of 25 of the same cohort of adults. The basion-axial interval only was measured on radiographs of 50 children 2-13 years old who had no occipitovertebral abnormalities. RESULTS: In 392 (98%) of the 400 adults, the basion-axial interval did not exceed 12 mm. In eight adults (2%), the basion was situated 1-4 mm posterior to the posterior axial line. The excursion of the basion in flexion and extension ranged from 0 to 10 mm, but did not exceed the 12-mm limit of normal. The basion translated posterior to the posterior axial line in six (24%) of the 25 adults in whom excursion was measured. Of the 400 adults, the basion-dental interval ranged from 2 to 15 mm (mean, 7.5 +/- 4.3 mm [2 SD]); the 95% accuracy range was 11.8 mm. In all 50 children (100%), the basion was within the normal basion-axial interval of 12 mm, and in no instance was the basion posterior to the posterior axial line. CONCLUSION: In adults, the occipitovertebral junction can be considered normal when both the basion-axial interval and basion-dental interval are 12 mm or less. In children less than 13 years old, the basion-dental interval is not reliable because of the variable age at which complete ossification and fusion of the dens occur. The normal basion-axial interval in children did not exceed 12 mm. This simple, anatomically based method of recognizing normal occipitovertebral relationships facilitates identification of occipitovertebral dissociation.

Radiologic diagnosis of traumatic occipitovertebral dissociation: 2. Comparison of three methods of detecting occipitovertebral relationships on lateral radiographs of supine subjects.

OBJECTIVE: The purpose of this study was to describe a method for recognizing acute traumatic occipitoatlantal dissociation that uses the basion-axial interval and basion-dental interval and to compare the accuracy of this method with the accuracies of two other methods: the Powers ratio and the x-line method. MATERIALS AND METHODS: Lateral radiographs of the cervical spine of 37 patients in whom the diagnosis of occipitoatlantal dissociation had been made on the basis of the relationship of the basion to the tip of the dens, the Powers ratio, and/or the x-line method were reviewed. Retrospectively, the occipitoatlantal junction of each was reassessed by using the the Powers ratio, the x-line, and the basion-axial interval-basion-dental interval methods. Independently, the neurologic findings at admission and the final neurologic diagnosis at discharge were obtained from the hospital records and were compared with the radiologic findings to determine the degree of radiologic-clinical correlation. RESULTS: Three groups of patients were identified by analyzing the basion-axial and basion-dental intervals of the occipitovertebral junction and related clinical findings. Twenty-three patients (group 1) had frank occipitoatlantal dislocation. Eight patients (group 2) had incomplete occipitoatlantal dissociation, which was defined as occipitoatlantal subluxation. The remaining six patients (group 3) had normal radiologic and clinical findings. Four patterns of occipitovertebral dissociation were identified: purely anterior (4/31, 13%), purely distracted (6/31, 19%), concomitantly anterior and distracted (20/31, 65%), and purely posterior (1/31, 3%). Regardless of the magnitude or direction of occipitoatlantal dissociation, the basion-axial interval-basion-dental interval method correctly identified the abnormality and the type of each. Positive clinical correlation was found in 13 (57%) of the 23 patients in group 1 and in 100% of the eight and six patients in groups 2 and 3, respectively. Neither the Powers ratio nor the x-line method could be applied in 17 (46%) of 37 cases, either because the opisthion could not be detected on the radiographs or because fusion of the posterior arch of C1 had not occurred. In the remaining 20 patients in whom the Powers ratio and the x-line method were applicable, the type of occipitoatlantal dissociation was correctly identified by the Powers ratio in 12 (60%) and by the x-line method in four (20%). Neither the Powers ratio nor the x-line method was applicable in three (50%) of the six patients in whom analysis by the basion-axial interval-basion-dental interval method and clinical findings showed no occipitoatlantal abnormality. Normal occipitovertebral anatomy was correctly identified by the Powers ratio in the remaining three patients (50%) and by the x-line method in two (33%). CONCLUSION: Direct measurement of occipitovertebral skeletal relationships altered by occipitoatlantal dissociation using the basion-axial and basion-dental intervals provides the most accurate radiologic assessment of this injury.

Microcomputers and database software for monitoring quality assurance activities.

A description of how one community hospital implemented a successful quality assurance program in radiology with the use of a personal computer and relational database management software is presented. The system has been well received and is easy to use and maintain. There are aspects of quality assurance beyond the double-reading method that are not addressed by this system. However, as we learn more about different quality assurance programs, the system has the capacity to evolve. The advertising literature is flooded with information about software packages that claim to meet all Joint Commission quality assurance requirements. Therefore, it is prudent to avoid making hasty purchasing decisions to accomplish a quick-fix solution to managing quality assurance activities. The Joint Commission recommends a systematic approach to defining needs and evaluating vendor products or services.

The current status of faculty staffing and resident training in emergency radiology. Results of a survey.

The results of a survey of United States and Canadian radiology residency programs in hospitals maintaining major emergency departments indicate that (1) radiologic faculty assignment to emergency medicine may include "all faculty," "specific faculty," "specific and other faculty," "general," and "musculoskeletal" faculty; (2) a chief of emergency radiology section is designated in less than 35% of radiology departments providing emergency room services; (3) radiology resident rotation in emergency radiology occurs in less than 2/3 of the surveyed programs; and (4) radiology resident experience in emergency radiology ranges from two to 16 weeks in 40% of these programs, the remainder being "unspecified." The effect of this circumstance upon the emergency department patient care and resident teaching in emergency radiology is discussed and remedial suggestions presented.

Circumflex retroesophageal right aortic arch simulating mediastinal tumor or dissecting aneurysm.

The authors present three cases of circumflex right aortic arch, a retroesophageal arch in which the aorta crosses from right to left behind the esophagus to descend on the left side. The findings on the frontal chest films resembled those of a left arch with mediastinal widening, simulating a mass. Aortography revealed four-vessel branching of the arch vessels, typical of right aortic arch with aberrant left subclavian artery. Computed tomography and barium studies of the esophagus demonstrated the retroesophageal course of the aorta. In two patients, obstruction of the thoracic portion of the left subclavian artery resulted in differences in blood pressure and pulse between the arms, supporting the clinical impression of dissecting aortic aneurysm.