Biomechanical analysis of an interference screw and a novel twist lock screw design for bone graft fixation.

BACKGROUND: Malpositioning of an anterior cruciate ligament graft during reconstruction can occur during screw fixation. The purpose of this study is to compare the fixation biomechanics of a conventional interference screw with a novel Twist Lock Screw, a rectangular shaped locking screw that is designed to address limitations of graft positioning and tensioning. METHODS: Synthetic bone (10, 15, 20lb per cubic foot) were used simulating soft, moderate, and dense cancellous bone. Screw push-out and graft push-out tests were performed using conventional and twist lock screws. Maximum load and torque of insertion were measured. FINDINGS: Max load measured in screw push out with twist lock screw was 64%, 60%, 57% of that measured with conventional screw in soft, moderate and dense material, respectively. Twist lock max load was 78% and 82% of that with conventional screw in soft and moderate densities. In the highest bone density, max loads were comparable in the two systems. Torque of insertion with twist lock was significantly lower than with conventional interference screw. INTERPRETATION: Based on geometric consideration, the twist lock screw is expected to have 35% the holding power of a cylindrical screw. Yet, results indicate that holding power was greater than theoretical consideration, possibly due to lower friction and lower preloaded force. During graft push out in the densest material, comparable max loads were achieved with both systems, suggesting that fixation of higher density bone, which is observed in young athletes that require reconstruction, can be achieved with the twist lock screw.

Body and risk: cultural ambivalence towards radioactivity through the history of two protagonists.

Two women with profoundly different backgrounds were brought together in a destiny that saw their paths cross and join in the discovery of radioactivity: Marie Curie and Blanche Wittman. The former was one of the greatest women scientists of all time, the only woman to have won the Nobel Prize for science. Noted for her extraordinary humanitarian spirit, and despite scandal over an affair that saw her hounded by journalists, she dedicated most of her life to scientific research. The latter passed into history as the "Queen of Hysterics" during her hospitalisation in the famous Parisian asylum Pitié Salpêtrière. After her recovery, she became a close assistant of Marie Curie in the extraction of radium from pitchblende, until her death sixteen years of toil later. The discovery of radioactivity was the common denominator underlying the vicissitudes of their lives, the same radioactivity that was so acclaimed and of such incredible diagnostic and therapeutic potential while at the same time so underrated in the everyday life of the time that disregarded, almost disparagingly, the deleterious biologic effects it was capable of provoking. At the beginning of the twentieth century, those effects were in fact often underestimated or scarcely considered, and it was only after World War II that there came an awareness of the ambiguous properties of ionising radiation. After numerous studies on radiation exposure, much of the current debate concerns the possible effects of exposure to small doses, such as those delivered in most radiological examinations. The theories proposed include the unorthodox theory of hormesis, which requires careful reevaluation. Much light has been shed on radiology since the time of Blanche and Marie, but there still remain many shadows to dispel, and this can only be done by serious and constant scientific commitment.

Detection of incidental vertebral fractures on routine lateral chest radiographs.

PURPOSE: This study sought to assess the usefulness of routine lateral chest radiographs for detecting unrecognised vertebral compression fractures. MATERIALS AND METHODS: We prospectively selected outpatients without symptoms or risk factors for osteoporosis who underwent chest radiography for different clinical indications. Two independent reviewers with different levels of experience assessed the radiographs for vertebral deformities and graded them as mild, moderate and severe according to the semiquantitative Genant Index. The kappa statistic was used to evaluate interobserver agreement and verify the reproducibility of this method. The prevalence of vertebral fractures observed was compared with that recorded in the official radiology reports. RESULTS: Our study involved 145 patients (73 men, 72 women; age range 50-86 years, mean age 67.5). Clinically relevant vertebral fractures were seen in 18/145 patients (12.4%). These were moderate in 13 patients and severe in five, and single in 12 patients and multiple in six. Interobserver agreement was very high (kappa=0.9). Only 11% of these fractures were recorded in the official reports. CONCLUSIONS: Lateral chest radiographs could be effective for assessing previously unknown vertebral compression fractures in individuals without clinical evidence or risk factors for osteoporosis.

Imaging of the patient with chronic bronchitis: an overview of old and new signs.

Up to now, neither chest radiograph nor high-resolution computed tomography (HRCT) has much to offer to the diagnosis of patients with chronic bronchitis (CB). A lot of HRCT findings can be observed, but they cannot be regarded as specific for pure CB. Their evaluation is often subjective, and measurements are poorly reproducible. In order to better characterise the HRCT features of CB, further efforts are warranted. The finding of bronchial wall thickening may even be considered nonsensitive as well as nonspecific. CB should not only be equated with narrowing of the airway since thickness of the bronchial wall may vary among different stages of development. Small pits can often be detected along the inner surfaces of the large bronchi in patients with CB using volumetric thin-section CT. Sometimes, multiple pits give rise to the accordion-like appearance that was described using bronchography. In our experience, they often occur in patients with long-lasting CB. A better comprehension of the large airways abnormalities is important because it is likely that the same pathophysiologic process that causes small-airway obstruction also takes place in larger airways, where it has less functional effect.

Nimesulide-induced acute hepatitis: evidence from six cases.

BACKGROUND/AIMS: A number of nonsteroidal anti-inflammatory drugs have been reported to provoke hepatic injury. Nimesulide is a new agent of the sulfonanilide class, and is a more selective inhibitor of cyclooxygenase type 2 than of type 1. Well-documented cases of acute hepatitis have not yet been reported with this drug. We report on six patients who developed acute liver damage after initiation of nimesulide. METHODS: Between April 1996 and January 1997, six patients with apparent nimesulide-induced liver injury were admitted. Clinical, laboratory, serologic, radiological, and histologic data of all six cases were extensively analyzed. The causal relationship between nimesulide and liver injury was assessed, using a scoring system elaborated by the French and International consensus meeting group. RESULTS: Four women developed a centrilobular (three) or panlobular (one) bridging necrosis, whereas two men showed a bland intrahepatic cholestasis. Jaundice was the presenting symptom in five of the six cases. One patient with hepatocellular necrosis and one with cholestasis had hallmarks of hypersensitivity with an increased blood and tissue eosinophilia. The causal relationship could be designated as "highly probable" in one, "probable" in four, and "possible" in one patient. One patient died from a pancreatic tumor 5 months after the diagnosis of toxic liver injury. In all other patients, liver tests returned to completely normal values within a late follow-up period of 6 to 17 months. CONCLUSIONS: Nimesulide-induced liver injury can present with hepatocellular necrosis or with pure cholestasis. From clinical and histologic data, it appears that both immunologic and metabolic idiosyncratic reactions can be invoked as the pathogenic mechanisms of nimesulide-induced liver disease.

Assessment of the severity of pulmonary emphysema by computed tomography.

Pulmonary emphysema is defined as an abnormal enlargement of alveolar spaces distal to the terminal bronchioles, with alveolar wall disruption and without obvious fibrosis. Clinico-functional evaluation and chest radiographic diagnosis are not highly accurate in detecting emphysema and in establishing the extent of the process of alveolar destruction. Several computed tomography (CT) techniques are now available for detection and quantitative assessment of emphysema. The results appear to correlate significantly better than chest radiography with functional impairment and pathological score. Many options have been proposed by different authors regarding CT technique. The choice, however, is essentially between inspiratory high resolution CT (HRCT) with a visual scoring system, and automated quantitative evaluation by means of a "density mask" (DM) program. This paper presents the state of the art on CT quantification of pulmonary emphysema and briefly discusses the technical options and parameters to be used, together with the problems to be solved.