Characterization of Lumbar Lordosis: Influence of Age, Sex, Vertebral Body Wedging, and L4-S1.

STUDY DESIGN: Retrospective radiographic review. OBJECTIVE: The objectives of the study were to determine the contributions to lumbar lordosis (LL) through both the vertebrae and the intervertebral disc (IVD), and to investigate the relationships between lumbar sagittal spine measurements and age and gender. SUMMARY OF BACKGROUND DATA: A small body of literature exists on the relative contributions of vertebral body and IVD morphology to LL, the effects of L4-S1 on overall LL, and the relationships/correlations between lumbar sagittal spine measurements. METHODS: Patients who met the inclusion criteria were retrospectively evaluated. Measurements included LL, pelvic incidence (PI), and % contributions of vertebral body wedging/IVD wedging/L4-S1 to LL. Patients were separated into groups by age and sex, demographic data were collected, and statistical analysis was completed. RESULTS: LL decreased with age, although PI remained similar. Females demonstrated increased LL and vertebral body wedging % than males. Males demonstrated increased L4-S1% than females. Despite a decrease in LL with age, patients maintained L4-S1% and IVD wedging %. There was a significant negative relationship between PI and IVD wedging, PI and L4-S1%, and LL and L4-S1%. CONCLUSIONS: During aging, the lumbar spine loses LL linearly. This occurs in the IVD and vertebral bodies. Females have increased LL compared with males, because of an increase in vertebral body wedging and IVD/vertebral wedging cranial to L4. In patients with high PI or LL, increased LL occurs from cranial to L4 and from vertebral body wedging.

Cutaneous drug eruptions including serum sickness-like reaction, symmetrical drug-related intertriginous and flexural exanthema, and drug-induced lupus.

Cutaneous manifestations of drug reactions are common yet vary widely in their appearance and degree of internal organ involvement. Serum sickness--like reactions, symmetrical drug-related intertriginous and flexural exanthem, granulomatous drug eruption, pseudolymphoma, and drug-induced lupus are medication-induced conditions with dermatologic presentations. Many of the conditions discussed are relatively rare but nonetheless demand our attention and understanding. Some of the conditions presented may be more likely encountered in the hospital setting, as is the case with serum sickness-like reactions and drug-induced lupus, whereas others may present to outpatient clinic for diagnosis. Given the similarities in clinical history of patients presenting with these conditions, an understanding of the clinical presentation, pathophysiology, culprit medications, histologic appearance, and serologic characteristics is warranted to correctly diagnose and manage these uncommon adverse reactions. We also discuss how to differentiate some of these conditions from more serious mimickers, as in the case of pseudolymphoma drug reaction mimicking a true lymphoma and drug-induced lupus mimicking acute systemic lupus erythematosus.

Efficacy of Applicator Devices for Self-Application of Topicals to the Back.

BACKGROUND: Self-application of topicals on the back can be challenging. OBJECTIVE: The aim was to assess topical back coverage using commercially available back applicators. MATERIALS AND METHODS: Ten subjects applied sunscreen to their back using their hands and then with 3 back applicators (large foam tip, small foam tip, roller tip). The amount of lotion used and the time it took to perform the application were recorded. The resulting distribution of sunscreen was assessed with a Wood's lamp; the area covered fluoresced less than the uncovered skin. Images were captured and then analyzed using an automated thresholding technique. RESULTS: Subjects applied more lotion when using the large foam tip (7.58 g, 95% CI 6.47-8.70 g; P < .004) and small foam tip (7.46 g, 95% CI 6.35-8.57 g; P < .006) applicators compared to hands alone (6.22 g, 95% CI 5.10-7.33 g). Application time was longer with the small foam tip applicator (113.4 s, 95% CI 96.7-130.1 s) relative to hand application (78.7 s, 95% CI 62-95.4 s) (P < .03). Coverage of the back was higher for the large foam tip (84.8%, 95% CI 78.4%-91.3%; P < .03), small foam tip (88.0%, 95% CI 81.6%-91.5%; P < .006), and roller tip (84.3%, 95% CI 77.9%-90.8%; P < .04) applicators compared to hand application (71.5%, 95% CI 65%-78%). The middle back tended to have less coverage when applying with the hands. CONCLUSIONS: Topical coverage of the back is improved with the use of applicator devices during self-application.

Lumbar Spine Response of Computational Finite Element Models in Multidirectional Spaceflight Landing Conditions.

The goals of this study are to compare the lumbar spine response variance between the hybrid III, test device for human occupant restraint (THOR), and global human body models consortium simplified 50th percentile (GHBMC M50-OS) finite element models and evaluate the sensitivity of lumbar spine injury metrics to multidirectional acceleration pulses for spaceflight landing conditions. The hybrid III, THOR, and GHBMC models were positioned in a baseline posture within a generic seat with side guards and a five-point restraint system. Thirteen boundary conditions, which were categorized as loading condition variables and environmental variables, were included in the parametric study using a Latin hypercube design of experiments. Each of the three models underwent 455 simulations for a total of 1365 simulations. The hybrid III and THOR models exhibited similar lumbar compression forces. The average lumbar compression force was 45% higher for hybrid III (2.2 ± 1.5 kN) and 51% higher for THOR (2.0 ± 1.6 kN) compared to GHBMC (1.3 ± 0.9 kN). Compared to hybrid III, THOR sustained an average 64% higher lumbar flexion moment and an average 436% higher lumbar extension moment. The GHBMC model sustained much lower bending moments compared to hybrid III and THOR. Regressions revealed that lumbar spine responses were more sensitive to loading condition variables than environmental variables across all models. This study quantified the intermodel lumbar spine response variations and sensitivity between hybrid III, THOR, and GHBMC. Results improve the understanding of lumbar spine response in spaceflight landings.

Neck Muscle Changes Following Long-Duration Spaceflight.

The effects of long-duration spaceflight on crewmember neck musculature have not been adequately studied. The purpose of this study was to evaluate the changes in the neck musculature on pre-flight and post-flight magnetic resonance imaging (MRI) examinations of six crewmembers on 4- to 6-month missions equipped with the advanced resistive exercise device (aRED). The MRI images were resliced to remove variations in spinal curvature, the cross-sectional area (CSA), and muscle fat infiltration (MFI) of neck musculature at the C1-C2, C4-C5, C7-T1, and T1-T2 intervertebral disc levels were measured bilaterally. Percent changes in the neck muscle CSA and fatty infiltration following spaceflight were calculated, and mixed models were used to assess significance of these changes. Crewmembers on missions equipped with the aRED experienced an average 25.1% increase in CSA for the trapezius muscle at C6-C7, an average 11.5% increase in CSA for the semispinalis capitis muscle at C4-C5, an average 9.0% increase in CSA for the sternocleidomastoid muscle at C4-C5, and an average 23.1% increase in CSA for the rhomboid minor at T1-T2. There were no significant changes in the CSA of the levator scapulae, splenius capitis, rectus capitis posterior major, scalenus anterior, scalenus posterior, scalenus medius, longissimus capitis, or obliquus capitis inferior muscles at the locations measured. None of the muscles analyzed experienced statistically significant changes in fatty infiltration with spaceflight. Our study indicates that long-duration spaceflight conditions are associated with preservation of CSA in most neck muscles and significant increases in the CSAs of the trapezius, semispinalis capitis, sternocleidomastoid, and rhomboid minor muscles. This may indicate that cervical muscles are not subjected to the same degradative effects microgravity imparts on the majority of muscles.

Lumbopelvic Muscle Changes Following Long-Duration Spaceflight.

Long-duration spaceflight has been shown to negatively affect the lumbopelvic muscles of crewmembers. Through analysis of computed tomography scans of crewmembers on 4- to 6-month missions equipped with the interim resistive exercise device, the structural deterioration of the psoas, quadratus lumborum, and paraspinal muscles was assessed. Computed tomography scans of 16 crewmembers were collected before and after long-duration spaceflight. The volume and attenuation of lumbar musculature at the L2 vertebral level were measured. Percent changes in the lumbopelvic muscle volume and attenuation (indicative of myosteatosis, or intermuscular fat infiltration) following spaceflight were calculated. Due to historical studies demonstrating only decreases in the muscles assessed, a one-sample t test was performed to determine if these decreases persist in more recent flight conditions. Crewmembers on interim resistive exercise device-equipped missions experienced an average 9.5% (2.0% SE) decrease in volume and 6.0% (1.5% SE) decrease in attenuation in the quadratus lumborum muscles and an average 5.3% (1.0% SE) decrease in volume and 5.3% (1.6% SE) decrease in attenuation in the paraspinal muscles. Crewmembers experienced no significant changes in psoas muscle volume or attenuation. No significant changes in intermuscular adipose tissue volume or attenuation were found in any muscles. Long-duration spaceflight was associated with preservation of psoas muscle volume and attenuation and significant decreases in quadratus lumborum and paraspinal muscle volume and attenuation.

Modeling Human Volunteers in Multidirectional, Uni-axial Sled Tests Using a Finite Element Human Body Model.

A goal of the Human Research Program at National Aeronautics and Space Administration (NASA) is to analyze and mitigate the risk of occupant injury due to dynamic loads. Experimental tests of human subjects and biofidelic anthropomorphic test devices provide valuable kinematic and kinetic data related to injury risk exposure. However, these experiments are expensive and time consuming compared to computational simulations of similar impact events. This study aimed to simulate human volunteer biodynamic response to unidirectional accelerative loading. Data from seven experimental studies involving 212 volunteer tests performed at the Air Force Research Laboratory were used to reconstruct 13 unique loading conditions across four different loading directions using finite element human body model (HBM) simulations. Acceleration pulses and boundary conditions from the experimental tests were applied to the Global Human Body Models Consortium (GHBMC) simplified 50th percentile male occupant (M50-OS) using the LS-Dyna finite element solver. Head acceleration, chest acceleration, and seat belt force traces were compared between the experimental and matched simulation signals using correlation and analysis (CORA) software and averaged into a comprehensive response score ranging from 0 to 1 with 1 representing a perfect match. The mean comprehensive response scores were 0.689 ± 0.018 (mean ± 1 standard deviation) in two frontal simulations, 0.683 ± 0.060 in four rear simulations, 0.676 ± 0.043 in five lateral simulations, and 0.774 ± 0.013 in two vertical simulations. The CORA scores for head and chest accelerations in these simulations exceeded mean scores reported in the original development and validation of the GHBMC M50-OS model. Collectively, the CORA scores indicated that the HBM in these boundary conditions closely replicated the kinematics of the human volunteers across all loading directions.

Validation of a Finite Element 50th Percentile THOR Anthropomorphic Test Device in Multiple Sled Test Configurations.

Computational models of anthropomorphic test devices (ATDs) can be used in crash simulations to quantify the injury risks to occupants in both a cost-effective and time-sensitive manner. The purpose of this study was to validate the performance of a 50th percentile THOR finite element (FE) model against a physical THOR ATD in 11 unique loading scenarios. Physical tests used for validation were performed on a Horizontal Impact Accelerator (HIA) where the peak sled acceleration ranged from 8-20 G and the time to peak acceleration ranged from 40-110 ms. The directions of sled acceleration relative to the THOR model consisted of -GX (frontal impact), +GY (left-sided lateral impact), and +GZ (downward vertical impact) orientations. Simulation responses were compared to physical tests using the CORrelation and Analysis (CORA) method. Using a weighted method, the average response and standard error by direction was +GY (0.83±0.03), -GX (0.80±0.01), and +GZ (0.76±0.03). Qualitative and quantitative results demonstrated the FE model's kinetics and kinematics were sufficiently validated against its counterpart physical model in the tested loading directions.

Biomechanical Comparison of Intrapelvic and Extrapelvic Fixation for Acetabular Fractures Involving the Quadrilateral Plate.

OBJECTIVES: Elderly patients represent the fastest growing and most difficult to treat population sustaining acetabular fractures. When treated surgically, isolated extrapelvic or combined intrapelvic-extrapelvic constructs may be used. No biomechanical or clinical study has compared the merits of these 2 techniques in cadaveric models. This research aims to biomechanically quantify the additional benefit of intrapelvic fixation to a standard extrapelvic fixation construct. METHODS: Ten cadaveric pelves underwent standardized anterior column and quadrilateral plate fracture creation. One hemipelvis from each subject received isolated extrapelvic fixation, whereas the other received adjunctive intrapelvic fixation. Specimens were then subjected to a 50% of body weight (BW) nondestructive stiffness test followed by loading to failure. For the 50% BW test, displacement at 50% BW and stiffness were calculated. For the load to failure test, stiffness, elastic energy, and plastic energy were calculated. Yield point, force at clinical failure (defined at 2 mm of displacement), and maximum force were also identified. A Wilcoxon matched-pairs t test was used to compare fixation groups. RESULTS: The addition of an intrapelvic plate improved construct performance for all test parameters. A statistically significant difference (P < 0.05) was reached for yield force, maximum force, and plastic energy. CONCLUSIONS: These findings demonstrate that the addition of intrapelvic plating may offer distinct advantages in prevention of catastrophic construct failure in situations in which significant lateral to medial force is applied to the greater trochanter such as patient falling.

Heterogeneity of Scaffold Biomaterials in Tissue Engineering.

Tissue engineering (TE) offers a potential solution for the shortage of transplantable organs and the need for novel methods of tissue repair. Methods of TE have advanced significantly in recent years, but there are challenges to using engineered tissues and organs including but not limited to: biocompatibility, immunogenicity, biodegradation, and toxicity. Analysis of biomaterials used as scaffolds may, however, elucidate how TE can be enhanced. Ideally, biomaterials should closely mimic the characteristics of desired organ, their function and their in vivo environments. A review of biomaterials used in TE highlighted natural polymers, synthetic polymers, and decellularized organs as sources of scaffolding. Studies of discarded organs supported that decellularization offers a remedy to reducing waste of donor organs, but does not yet provide an effective solution to organ demand because it has shown varied success in vivo depending on organ complexity and physiological requirements. Review of polymer-based scaffolds revealed that a composite scaffold formed by copolymerization is more effective than single polymer scaffolds because it allows copolymers to offset disadvantages a single polymer may possess. Selection of biomaterials for use in TE is essential for transplant success. There is not, however, a singular biomaterial that is universally optimal.

Correlating structure and function during the evolution of fibrinogen-related domains.

Fibrinogen-related domains (FReDs) are found in a variety of animal proteins with widely different functions, ranging from non-self recognition to clot formation. All appear to have a common surface where binding of one sort or other occurs. An examination of 19 completed animal genomes--including a sponge and sea anemone, six protostomes, and 11 deuterostomes--has allowed phylogenies to be constructed that show where various types of FReP (proteins containing FReDs) first made their appearance. Comparisons of sequences and structures also reveal particular features that correlate with function, including the influence of neighbor-domains. A particular set of insertions in the carboxyl-terminal subdomain was involved in the transition from structures known to bind sugars to those known to bind amino-terminal peptides. Perhaps not unexpectedly, FReDs with different functions have changed at different rates, with ficolins by far the fastest changing group. Significantly, the greatest amount of change in ficolin FReDs occurs in the third subdomain ("P domain"), the very opposite of the situation in most other vertebrate FReDs. The unbalanced style of change was also observed in FReDs from non-chordates, many of which have been implicated in innate immunity.