Biomechanical comparison of anterior Caspar plate and three-level posterior fixation techniques in a human cadaveric model.

Traumatic cervical spine injuries have been successfully stabilized with plates applied to the anterior vertebral bodies. Previous biomechanical studies suggest, however, that these devices may not provide adequate stability if the posterior ligaments are disrupted. To study this problem, the authors simulated a C-5 teardrop fracture with posterior ligamentous instability in human cadaveric spines. This model was used to compare the immediate biomechanical stability of anterior cervical plating, from C-4 to C-6, to that provided by a posterior wiring construct over the same levels. Stability was tested in six modes of motion: flexion, extension, right and left lateral bending, and right and left axial rotation. The injured/plate-stabilized spines were more stable than the intact specimens in all modes of testing. The injured/posterior-wired specimens were more stable than the intact spines in axial rotation and flexion. They were not as stable as the intact specimens in the lateral bending or extension testing modes. The data were normalized with respect to the motion of the uninjured spine and compared using repeated measures of analysis of variance, the results of which indicate that anterior plating provides significantly more stability in extension and lateral bending than does posterior wiring. The plate was more stable than the posterior construct in flexion loading; however, the difference was not statistically significant. The two constructs provide similar stability in axial rotation. This study provides biomechanical support for the continued use of bicortical anterior plate fixation in the setting of traumatic cervical spine instability.

Cerebral blood flow in a rat glioma model during halothane anesthesia.

Little is known about the influence of infiltrating gliomas on the responsivity of the cerebral circulation to anesthetic agents. Therefore we designed a study to address this issue. Male Fischer 344 rats were assigned to two tumor groups and one sham group. In the two tumor groups, glioma cells were stereotactically injected into the right striatum; animals in the sham group were injected with sterile culture medium only. Either 12 or 16 days after injection, the rats were anesthetized with 1 MAC halothane in 40% O2/balance N2. Local and remote regional cerebral blood flow was then determined using 14C-iodoantipyrine autoradiography. Physiologic values (PaCO2, PaO2, pHa, mean arterial pressure, and rectal temperature) were similar for both tumor and sham groups. Tumor volume was relatively small (cross-sectional diameter = 2-3 mm), and there was no evidence of midline shift in coronal tissue sections. Blood flow within the tumor was substantially reduced relative to adjacent structures (e.g., tumor = 88 +/- 10 ml/100 g/min; adjacent caudate = 161 +/- 23 ml/100 g/min). There were no significant differences between the tumor and sham groups for regional blood flow values in histologically normal tissue in either the injected or contralateral hemispheres. We conclude that this model of brain neoplasia shows no evidence of either local or remote changes in the cerebrovascular responsibility of normal tissue to volatile anesthesia.

Types of aortic stenosis in surgically removed valves.

In 109 specimens of aortic valves removed surgically from adults for isolated or dominant aortic stenosis, five types of valve were encountered. In order of decreasing frequency the types were as follows: calcification of congenitally bicuspid aortic valves (48.6%); calcification of a normally tricuspid aortic valve without commissural fusion, the so-called senile type of aortic stenosis (27.6%); calcification of an acquired bicuspid valve (12.8%); the fibrous (rheumatic)-type valve (10.1%); and calcification of congenitally unicuspid valves (0.9%). In the overall study men were more commonly represented than women by a ratio of 3:2. In only the senile type were women more commonly represented than men.

Infratentorial stereotactic biopsy. A review of 11 cases.

A review of the stereotactic cases performed at the University of Iowa between February, 1985, and December, 1990, yielded 12 infratentorial stereotactic biopsies in 11 patients. A definitive diagnosis was obtained in 9 of 11 patients. One patient required a second biopsy to obtain a diagnosis and 1 yielded cystic fluid only. The pathological diagnosis obtained included 4 high-grade gliomas, 2 undifferentiated adenocarcinomas, 2 low-grade astrocytomas, 1 malignant ependymoma, 1 pontine hematoma and 1 cyst. None of the patients experienced increased neurological deficit following biopsy and there was no mortality. One patient developed postoperative meningitis. We conclude that stereotactic biopsy of infratentorial lesions can be performed safely with a high probability of obtaining a diagnosis. Adequate tissue diagnosis is necessary to direct further therapy.

Intracavernous self-injection with phentolamine and papaverine for the treatment of impotence.

To evaluate the efficacy and safety of intracavernous self-injection of phentolamine and papaverine for the treatment of impotence, 30 patients were enrolled in a prospective, randomized, double-blind, placebo-controlled cross-over study of papaverine and phentolamine versus normal saline. A total of 29 patients completed the study. The phentolamine plus papaverine combination resulted in erection in 24 patients (82.8 per cent) and no erection occurred after injection of saline. Of the patients 12 (41.4 per cent) experienced technical difficulties with the injection. Ecchymosis of the penis at the site of injection was common and 1 patient experienced priapism that resolved spontaneously. No other side effects occurred. Intracavernous self-injection with phentolamine and papaverine appears to be a safe and effective treatment of impotence but long-term effects must be determined.