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Biomedical subjects

Heather McCann

Publications and source records attributed to Heather McCann.

6 recordsLinked to original sources
PubMed2006

Biomechanical comparison of augmentation techniques for insufficiency fractures.

STUDY DESIGN: Biomechanical laboratory research. OBJECTIVE: To compare 4 techniques for vertebral body insufficiency fracture repair by analyzing restoration of height, strength, and stiffness, and quantifying cement leakage. SUMMARY OF BACKGROUND DATA: Current techniques for insufficiency fracture repair, restore prefracture strength, and all potentially have the complication of cement extrusion. To our knowledge, there is no information directly comparing different augmentation techniques. METHODS: There were 4 osteoporotic/osteopenic fresh cadaveric spines' (T6-L5) vertebral bodies divided into the 4 groups and by levels (thoracic, thoracolumbar, lumbar). They were compressed to 25% of their initial height to simulate insufficiency fractures. Fixation techniques were vertebroplasty, osteoplasty (Interpore Cross Int., Irvine, CA), the Cavity Creation System (Synthes, Paoli, PA), and kyphoplasty (Kyphon, Sunnyvale, CA). Fractures were fixed using 3 cc of bone cement and recompressed. RESULTS: No significant difference was found in strength, height restoration, or stiffness among techniques (P < 0.05). Stiffness was significantly different in the lumbar levels between initial and post-fixation measurements (P < 0.05). Cement extrusion of 1 mL was seen in 1 vertebroplasty specimen. CONCLUSIONS: The 4 techniques equally restored strength and stiffness. No difference was seen in height restoration. Cement extrusion was significant in only 1 vertebral body, which may be attributable to the cement quantity.

Bone Cements↗
PubMed2003

Working memory and schizophrenia: evidence for slowed encoding.

Previous studies have found impairments in working memory in individuals with schizophrenia, but have not identified the underlying information processing deficit. Because schizophrenia is associated with slowed cognitive processing, deficits on working memory tests may be due to decreased speed of encoding rather than an inability to maintain information over time. This hypothesis was examined using a Delayed Match to Sample (DMTS) Test. Task difficulty under 0-delay conditions was equated by individually establishing the stimulus presentation time needed to reach approximately 80% accuracy. Schizophrenia participants required longer presentation durations, but there were no group differences under delay conditions when performance was equated in the 0-delay condition. These results suggest that poor working memory performance in schizophrenia results from slowed encoding processes.

Adolescent↗
PubMed2002

Intraneuronal advanced glycation endproducts in presenilin-1 Alzheimer's disease.

The most frequently mutated gene resulting in dominantly inherited Alzheimer's disease is presenilin-1. We have used antibodies against advanced glycation endproducts (AGE) in brain tissue sections of four patients with three different presenilin I mutations. Accumulation of intracellular AGE was observed in 75-95% of pyramidal neurons in patients with presenilin-1 mutations, far exceeding the percentage of presenilin-1-, tau- or ubiquitin-positive neurons. This high level of AGE-modified proteins in vulnerable neurons is most likely explained by higher levels of their precursors (reactive (di)carbonyl products) or a slower turnover of the participating proteins. These conditions of carbonyl stress may contribute to increased neuronal dysfunction and vulnerability leading to the early disease onset.

Adult↗
PubMed2002

Neurofilament-immunoreactive neurons in Alzheimer's disease and dementia with Lewy bodies.

The cortical neurons thought to be selectively affected in dementia with Lewy bodies (DLB) are those containing nonphosphorylated 200-kDa neurofilament (NF) protein. As these neurons are largely spared in Alzheimer's disease (AD), DLB and AD may impact on different cortical neuronal populations. The present study quantifies the NF-containing neurons in frontal and temporal cortex of 8 AD, 8 DLB, and 8 control cases. Formalin-fixed paraffin-embedded tissue was immunohistochemically stained with antibodies against nonphosphorylated and phosphorylated NF. Immunoreactive neurons were quantified by areal fraction analysis and corrected for cortical volume. As expected, nonphosphorylated and phosphorylated NF accumulated in the pathological hallmarks of AD and DLB. However, rather than a decrease in NF-containing neurons, a doubling of this population was observed in DLB, compared with AD and controls. This increased number of cortical NF-containing neurons reveal novel widespread cortical changes, beyond those explained by Lewy body formation, that are specific for DLB.

Aged↗
PubMedDate not supplied

The effect of tibial rotation on varus deformity measurement.

PURPOSE: Tibial osteotomy is used to treat a variety of orthopedic conditions, including reduction in pain and improvement of deformity and function. In templating for surgery, accurate radiographic measurement aids in planning for correction. The purpose of our study was to examine the effect of internal rotation and external rotation on measurement of tibial sawbone models with 5 closing wedge varus deformities at 10-degree increments between 10 and 50 degrees. One sawbone without deformity served as the control. STUDY DESIGN: A total of 66 radiographs were measured by 5 individuals. Measurement deviations from the control in each of the 10 positions of rotation were assessed. RESULTS: In the analysis of variance models, increased rotation and varus angulation were associated with increased deviation compared with the control. In external rotation for every 10 degrees of varus angulation, the degree deviation increased 0.69 degrees. In IR for every 10 degrees of angulation, the degree deviation increased by 0.84 degrees. Internal rotation had the greatest impact. Mean differences between different rater's measurements were small (1.1+/-1.2 degrees) and correlations suggested high interrater reliability. CONCLUSIONS: As the degree of rotation from neutral increased and varus angulation increased, deviation from neutral increased. CLINICAL RELEVANCE: Clinically, the results of this study support the importance of proper alignment of the tibia during radiography to more precisely template surgery.

Artifacts↗