Screw angulation affects bone-screw stresses and bone graft load sharing in anterior cervical corpectomy fusion with a rigid screw-plate construct: a finite element model study

Background contextAnterior corpectomy and reconstruction with bone graft and a rigid screw-plate construct is an established procedure for treatment of cervical neural compression. Despite its reliability in relieving symptoms, there is a high rate of construct failure, especially in multilevel cases.PurposeThere has been no study evaluating the biomechanical effects of screw angulation on construct stability; this study investigates the C4–C7 construct stability and load-sharing properties among varying screw angulations in a rigid plate-screw construct.Study designA finite element model of a two-level cervical corpectomy with static anterior cervical plate.MethodsA three-dimensional finite element (FE) model of an intact C3–T1 segment was developed and validated. From this intact model, a fusion model (two-level [C5, C6] anterior corpectomy) was developed and validated. After corpectomy, allograft interbody fusion with a rigid anterior screw-plate construct was created from C4 to C7. Five additional FE models were developed from the fusion model corresponding to five different combinations of screw angulations within the vertebral bodies (C4, C7): (0°, 0°), (5°, 5°), (10°, 10°), (15°, 15°), and (15°, 0°). The fifth fusion model was termed as a hybrid fusion model.ResultsThe stability of a two-level corpectomy reconstruction is not dependent on the position of the screws. Despite the locked screw-plate interface, some degree of load sharing is transmitted to the graft. The load seen by the graft and the shear stress at the bone-screw junction is dependent on the angle of the screws with respect to the end plate. Higher stresses are seen at more divergent angles, particularly at the lower level of the construct.ConclusionThis study suggests that screw divergence from the end plates not only increases load transmission to the graft but also predisposes the screws to higher shear forces after corpectomy reconstruction. In particular, the inferior screw demonstrated larger stress than the upper-level screws. In the proposed hybrid fusion model, lower stresses on the bone graft, end plates, and bone-screw interface were recorded, inferring lower construct failure (end-plate fractures and screw pullout) potential at the inferior construct end.     

Metabolism of antidepressants: urinary metabolites of trimipramine in the rat

1. Studies on the metabolism of the tricyclic antidepressant trimipramine (TMP) in the rat are described. 2. Twenty metabolites of TMP were isolated from rat urine after enzymatic hydrolysis and their structures were determined by a gas chromatographic-mass spectrometric (GC-MS) method. 3. Twelve TMP metabolites were the result of alicyclic (C10 or C11) oxidation in addition to the other metabolic pathways.     

Actin-free Gc globulin: a rapidly assessed biomarker of organ dysfunction in acute liver failure and cirrhosis.

Reductions in serum levels of Gc globulin, a hepatically synthesized component of the extracellular actin scavenger system responsible for complexing circulating actin and attenuating intravascular microthrombus formation, are associated with poor outcome in acute liver failure. Clinically applicable assays of the important actin-free fraction (Af-Gc) have not been available until now. We measured actin-free Gc globulin levels with a novel, rapid assay in 61 cases of acute liver failure (ALF) and in 91 patients with cirrhosis (40 of whom were clinically unstable with extrahepatic organ dysfunction), and studied associations with liver dysfunction, extrahepatic organ dysfunction, indices of disseminated coagulation, and outcome. Reductions in Af-Gc levels mirrored hepatic dysfunction and organ dysfunction in both groups, and discriminated patients with poor prognosis from those with good prognosis in the ALF cohort. Levels were lowest in patients with ALF (10% of control values), but levels were also markedly reduced in both unstable (28%) and stable (44%) patients with cirrhosis. Associations with markers of disseminated intravascular coagulation were seen in both groups, most notably in the cirrhosis cohort, supporting a pathophysiological role for reduced Af-Gc in the evolution of organ dysfunction. In acetaminophen-induced ALF, Af-Gc identified patients with poor prognosis as well as did the Acute Physiology and Chronic Health Evaluation (APACHE II) score (area under the receiver operating characteristic curve, 0.7), and in cirrhosis, Af-Gc was an independent predictor of mortality by multifactorial analysis. In conclusion, the importance of Af-Gc reductions in the development of multiple organ dysfunction in ALF and cirrhosis is highlighted, probably resulting from reduced hepatic production and peripheral exhaustion of this arm of the extracellular actin scavenger system.     

1,450 nm Long-Pulsed Diode Laser for Nonablative Skin Rejuvenation

Background:. There has been growing patient demand for laser technology to treat rhytids and to refine skin texture without the associated lifestyle hindrance common to ablative cutaneous procedures. Nonablative laser systems have been developed to meet this need and, in many instances, have replaced ablative lasers as the preferred treatment modality.
Objective:. To review long-pulsed diode laser technology in the treatment of a variety of cutaneous disorders.
Materials and Methods. All publications involving 1,450 nm long-pulsed diode laser technology were reviewed and discussed.
Results. The latest generation of nonablative lasers, in the midinfrared electromagnetic spectrum, selectively targets and heats dermal tissue to stimulate collagen remodeling while sparing the epidermis.
Conclusions. Demonstrating efficacy in the treatment of a wide range of cutaneous disorders, including facial rhytids, acne vulgaris, and atrophic scars, the 1,450 nm diode laser is a useful addition to the nonablative laser armamentarium.     

Protective Effects of Antioxidants Against Uraemia-Induced Lipid Peroxidation and Glutathione Depletion in Humans

Abstract: The effects of uraemias and antioxidant therapy for 40 days with vitamin A, vitamin C and vitamin E on blood and erythrocyte sulfhydryl (glutathione, GSH) content and on erythrocyte glutathione-S transferase (GST), glutathione reductase (GSR) and glutathione peroxidase activities were studied in six uraemic patients maintained on haemodialysis. In addition, the effect of antioxidant therapy on erythrocyte lipid peroxidation was determined, and erythrocyte haemoglobin content was measured. Uraemic patients in dialysis exhibited significant decreases in blood and erythrocyte GSH content as well as significant decreases in the activities of GST, GSR and GSH-peroxidase relative to control subjects. Furthermore, the uraemic patients had elevated erythrocyte malondialdehyde levels. Blood and erythrocyte GSH content from uraemic patients was significantly elevated after 20 days of antioxidant treatment and remained elevated thereafter throughout the remaining 20 days of the study (130% and 173%, respectively). Antioxidant therapy also produced significant increases in GSR and GSH-peroxidase activities after 20 days of treatment which remained relatively constant thereafter. No significant change in GST activity was observed. Erythrocyte malondialdehyde levels, as an index of oxidative tissue damage, exhibited a significant decrease (70%) in the patients after 40 days of antioxidant therapy. A gradual increase in erythrocyte haemoglobin content was observed following treatment of the uraemic subjects (45% at day 40). The results suggest that antioxidant therapy may protect against oxidative stress associated with uraemia.     

The profile and incidence of cancer in Down syndrome

Background Down syndrome is one of the commonest causes of intellectual disability. As life expectancy improves with early and more intensive surgical and medical treatments, people with the disorder are more likely to exhibit classic morbidity and mortality patterns and be diagnosed with diseases such as cancer. Methods A profile of cancer cases among people with Down syndrome has been compiled, based on the analysis of a linked data set that included information from the Disability Services Commission of Western Australian and the State Cancer Registry. Results and conclusions Although the total age‐ and sex‐standardized incidence ratios (SIRs) for people with Down syndrome were similar to that for the general population, SIRs for leukaemia were significantly higher while the incidence of certain other types of cancers was reduced. Overall, there was a lower incidence of solid tumours in Down syndrome, possibly reflecting the age profile of the study cohort.