Retrolisthesis and lumbar disc herniation: a preoperative assessment of patient function.

BACKGROUND CONTEXT: Retrolisthesis is relatively rare but when present has been associated with increased back pain and impaired back function. Neither the prevalence of this condition in individuals with lumbar disc herniations nor its possible relation to preoperative back pain and dysfunction has been well studied. PURPOSE: The purposes of this study were as follows: (1) to determine the prevalence of retrolisthesis (alone or in combination with other degenerative conditions) in individuals with confirmed L5-S1 disc herniation who later underwent lumbar discectomy; (2) to determine if there is any association between retrolisthesis and degenerative changes within the same vertebral motion segment; and (3) to determine the relation between retrolisthesis (alone or in combination with other degenerative conditions) and preoperative low back pain, physical function, and quality of life. STUDY DESIGN/SETTING: Cross-sectional study. PATIENT SAMPLE: A total of 125 individuals were identified for incorporation into this study. All patients had confirmed L5-S1 disc herniation on magnetic resonance imaging (MRI) and later underwent L5-S1 discectomy. All patients were enrolled in the Spine Patient Outcomes Research Trial (SPORT) study; data were obtained from the multi-institutional database comprised of SPORT patients from across the United States. OUTCOME MEASURES: Retrolisthesis, degenerative change on MRI, and Modic changes. METHODS: MRI scans of the lumbar spine were assessed at spinal level L5-S1 for all 125 patients. Retrolisthesis was defined as posterior subluxation of 8% or more. Disc degeneration was defined as any loss of disc signal on T2 imaging. Modic changes were graded 1 to 3 and collectively classified as vertebral endplate degenerative changes. The presence of facet arthropathy and ligamentum flavum hypertrophy was classified jointly as posterior degenerative changes. RESULTS: The overall incidence of retrolisthesis at L5-S1 in our study was 23.2%. Retrolisthesis combined with posterior degenerative changes, degenerative disc disease, or vertebral endplate changes had incidences of 4.8%, 16%, and 4.8% respectively. The prevalence of retrolisthesis did not vary by sex, age, race, smoking status, or education level when compared with individuals with normal sagittal alignment. However, individuals with retrolisthesis were more likely to be receiving workers' compensation than those without retrolisthesis. Increased age was found to be associated with individuals having vertebral endplate degenerative changes (both alone and in conjunction with retrolisthesis) and degenerative disc disease. Individuals who had retrolisthesis with concomitant vertebral endplate degenerative changes were more often smokers and had no insurance. The presence of retrolisthesis was not associated with an increased incidence of having degenerative disc disease, posterior degenerative changes, or vertebral endplate changes. No statistical significance was found between the presence of retrolisthesis on the degree of patient preoperative low back pain and physical function. Patients with degenerative disc disease were found to have increased leg pain compared with those patients without degenerative disc changes. CONCLUSIONS: We found no significant relationship between retrolisthesis in patients with L5-S1 disc herniation and worse baseline pain or function. It is possible that the contribution of pain or dysfunction related to retrolisthesis was far overshadowed by the presence of symptoms caused by the concomitant disc herniation. It remains to be seen whether retrolisthesis will affect outcome after discectomy in these patients.     

Comparison of Asymmetry in Cerebral Blood Flow Between Brain Hemispheres Using Digital Subtraction Angiography

BACKGROUND AND PURPOSE: Recently, endovascular techniques have gained significant therapeutic potential for both treatment and prevention of stroke. Cerebral angiography, which is an essential component of these procedures, has been used to provide morphological information regarding condition of blood vessels. In this study, we propose to determine the possibility of acquiring information regarding cerebral blood flow (CBF) in addition to morphologic information from data routinely available during angiography. METHODS: Digital subtraction angiography sequences were obtained for eight patients having occlusive disease in internal carotid artery (ICA) territories. Two regions-of-interest (ROIs) corresponding to the two brain hemispheres on AP view were delineated. For each image, the average pixel value within each ROI was calculated and used to generate time-density curves. Indices obtained from each curve were compared with each other and with the results obtained from the single photon emission computed tomography (SPECT) studies performed a pre- or postangiography procedure. RESULTS: Comparison between ICA stenosis and cerebral perfusion measurements revealed that cerebral perfusion deficit can be independent of arterial occlusive disease. The indices obtained from the time-density curves exhibit a correlating trend with the results from SPECT studies. However, lack of sufficient sample data prevented any meaningful statistical analysis to be conducted. CONCLUSIONS: We have developed a technique for utilizing the angiographic data for the important task of routinely and easily measuring CBF. Availability of CBF measurements during cerebral angiography may favorably impact upon the appropriate use of endovascular procedures and potentially contribute to the reduction of morbidity and mortality associated with stroke.     

An inventory-location optimization model for equitable influenza vaccine distribution in developing countries during the COVID-19 pandemic

The addition of other respiratory illnesses such as flu could cripple the healthcare system during the coronavirus disease 2019 (COVID-19) pandemic. An annual seasonal influenza vaccine is the best way to help protect against flu. Fears of coronavirus have intensified the shortage of influenza shots in developing countries that hope to vaccinate many populations to reduce stress on their health services. We present an inventory-location mixed-integer linear programming model for equitable influenza vaccine distribution in developing countries during the pandemic. The proposed model utilizes an equitable objective function to distribute vaccines to critical healthcare providers and first responders, elderly, pregnant women, and those with underlying health conditions. We present a case study in a developing country to exhibit efficacy and demonstrate the optimization model’s applicability.     

Involvement of xanthine oxidase in oxidative stress and iron release during hyperthermic rat liver perfusion.

The hepatotoxic effects of hyperthermia have been proposed to be related to lipid peroxidation as a consequence of oxidative stress. This can result from exposure of the cell to "radical oxygen" species such as the superoxide and hydrogen peroxide generated by the activity of the oxidase form (type O) of xanthine oxidase (XO), which is converted to that form by perfusion of the liver at hyperthermic temperatures. These radical species are not reactive enough in themselves to cause cell damage but require the presence of a catalyst such as low molecular weight chelated iron. In these studies, ferritin was shown to be a source of iron for the oxidative stress of hyperthermia. (a) Iron was released from ferritin in vitro by the activity of rat liver XO. The rate of iron release from ferritin in this incubation system was a function of the amount of type O XO present and the temperature. Inclusion of allopurinol or superoxide dismutase in the incubation resulted in significantly lower rates of iron release. (b) Livers from Sprague-Dawley rats were perfused at 42.5 degrees and 37 degrees C for 1 h. During the recirculating perfusion, loss of iron from the liver into the perfusate was significantly greater (P less than 0.05) at 42.5 degrees C than at 37 degrees C. Also, there was a pronounced increase in the lactate dehydrogenase and aspartate aminotransferase enzymes in the perfusate during perfusion at 42.5 degrees C. Furthermore, intrahepatic levels of low molecular weight chelated iron were significantly (P less than 0.05) increased following perfusion at 42.5 degrees C. All these responses were abrogated by the inclusion of allopurinol in the perfusate. (c) Oxidative stress, assessed by the efflux of glutathione and oxided glutathione from the liver at 42.5 degrees and 37 degrees C, was significantly (P less than 0.05) increased at the hyperthermic temperature. This oxidative stress was inhibited by iron chelation and allopurinol. These results demonstrate that there is a causal relationship between the generation of superoxide by type O XO produced by hyperthermic perfusion and mobilization of iron from ferritin to form a pool of low molecular weight chelated iron. This iron pool in combination with active oxygen species leads to oxidative stress and lipid peroxidation.