Analysis of 3D strain in the human medial meniscus.

This study presents a method to evaluate three-dimensional strain in meniscal tissue using medical imaging. Strain is calculated by tracking small teflon markers implanted within the meniscal tissue using computed tomography imaging. The results are presented for strains in the middle and posterior third of the medial menisci of 10 human cadaveric knees, under simulated physiologically relevant loading. In the middle position, an average compressive strain of 3.4% was found in the medial-lateral direction, and average tensile strains of 1.4% and 3.5% were found in the anterior-posterior and superior-inferior directions respectively at 5° of knee flexion with an applied load of 1× body weight. In the posterior position, under the same conditions, average compressive strains of 2.2% and 6.3% were found in the medial-lateral and superior-inferior directions respectively, and an average tensile strain of 3.8% was found in the anterior-posterior direction. No statistically significant difference between strain in the middle or posterior of the meniscus or between the global strains is uncovered.

Tensile mechanical properties of human forearm tendons.

Previous studies of the mechanical properties of tendons in the upper limb have used embalmed specimens or sub-optimal methods of measurement. The aim of this study was to determine the biomechanical properties of all tendons from five fresh frozen cadaveric forearms using updated methodology. The cross-sectional area of tendons was accurately measured using a laser reflectance system. Tensile testing was done in a precision servo-hydraulic device with cryo-clamp fixation. We determined that the cross-sectional area of some tendons is variable and directly influences the calculated material properties; visual estimation of this is unreliable. Data trends illustrate that digital extensor tendons possess the greatest tensile strength and a higher Young's modulus than other tendon types.

Regional and depth variability of porcine meniscal mechanical properties through biaxial testing.

The menisci in the knee joint undergo complex loading in-vivo resulting in a multidirectional stress distribution. Extensive mechanical testing has been conducted to investigate the tissue properties of the knee meniscus, but the testing conditions do not replicate this complex loading regime. Biaxial testing involves loading tissue along two different directions simultaneously, which more accurately simulates physiologic loading conditions. The purpose of this study was to report mechanical properties of meniscal tissue resulting from biaxial testing, while simultaneously investigating regional variations in properties. Ten left, fresh porcine joints were obtained, and the medial and lateral menisci were harvested from each joint (twenty menisci total). Each menisci was divided into an anterior, middle and posterior region; and three slices (femoral, deep and tibial layers) were obtained from each region. Biaxial and constrained uniaxial testing was performed on each specimen, and Young's moduli were calculated from the resulting stress strain curves. Results illustrated significant differences in regional mechanical properties, with the medial anterior (Young's modulus (E)=11.14 ± 1.10 MPa), lateral anterior (E=11.54 ± 1.10 MPa) and lateral posterior (E=9.0 ± 1.2 MPa) regions exhibiting the highest properties compared to the medial central (E=5.0 ± 1.22 MPa), medial posterior (E=4.16 ± 1.13 MPa) and lateral central (E=5.6 ± 1.20 MPa) regions. Differences with depth were also significant on the lateral meniscus, with the femoral (E=12.7 ± 1.22 MPa) and tibial (E=8.6 ± 1.22 MPa) layers exhibiting the highest Young's moduli. This data may form the basis for future modeling of meniscal tissue, or may aid in the design of synthetic replacement alternatives.

Rapid resolution of hidradenitis suppurativa after bariatric surgical intervention.

We report the case of a 52-year-old man who underwent rapid improvement of long-standing treatment-refractory hidradenitis suppurativa (HS) following bariatric surgical intervention and subsequent dramatic weight loss. This morbidly obese man had previously shown little response to multiple treatment avenues, including an extended course of antibiotic therapy and treatment with acitretin. He had developed marked genital lymphoedema consequential to HS, which had further complicated his HS treatment. However, his disease regressed significantly within weeks of undergoing laparoscopic gastric sleeve surgery, and the HS activity has remained quiescent for over 1 year since the bariatric intervention. This supports the role for obesity in the pathophysiology of HS, and highlights the importance of adequately addressing lifestyle factors in the treatment of HS.

Genital lymphoedema due to ano-genital granulomatosis.

A 21-year-old man presented to genitourinary (GU) medicine physicians with (initially) painful penile and scrotal swelling. A diagnosis of ano-genital granulomatosis was confirmed on histological analysis of penile skin. Enquiring about systemic symptoms resulted in the additional diagnosis of gastrointestinal Crohn's disease. The patient is now receiving immunosuppressive therapy to treat both conditions.

Progressive lymphangiomatosis and Gorham's disease: case report and clinical implications.

Lymphangiomatosis is a rare proliferative disorder of the lymphatic system. The etiology is unknown, rendering it difficult to manage. This case report of lymphangiomatosis with features of Gorham's disease reveals the progressive and unexpected nature of the condition. It highlights the need for further research into the pathophysiology and management of lymphangiomatosis as current treatment options are limited.

Herschel detects a massive dust reservoir in supernova 1987A.

We report far-infrared and submillimeter observations of supernova 1987A, the star whose explosion was observed on 23 February 1987 in the Large Magellanic Cloud, a galaxy located 160,000 light years away. The observations reveal the presence of a population of cold dust grains radiating with a temperature of about 17 to 23 kelvin at a rate of about 220 times the luminosity of the Sun. The intensity and spectral energy distribution of the emission suggest a dust mass of about 0.4 to 0.7 times the mass of the Sun. The radiation must originate from the supernova ejecta and requires the efficient precipitation of all refractory material into dust. Our observations imply that supernovae can produce the large dust masses detected in young galaxies at very high redshifts.

Kinematics of ulnar head arthroplasty.

This in vitro study evaluated the performance of an ulnar head replacement. A joint simulator was employed that produced active forearm rotation in cadaveric specimens, with motion measured using an electromagnetic tracking system. The kinematics of the intact forearm were compared with a partial ulnar head replacement and a full replacement (with and without soft-tissue reconstruction) and a full excision of the ulnar head. There were no differences between intact kinematics and those following prosthetic reconstruction. However, ulnar head excision produced distal radioulnar joint instability in the form of radioulnar convergence and increased anteroposterior translations.

A review of methodology and quantification in dental microwear analysis.

Dental microwear analysis is a method of inferring oral events (primarily food processing and aspects of masticatory biomechanics) from microscopic abrasion patterns retained on the enamel surfaces of teeth. Although some qualitative pattern differences may be easily distinguishable, most of the significant results produced thus far have derived from quantified studies of SEM images of occlusal enamel. It often goes unnoticed by readers of microwear reports who are not themselves specialists that microwear analysis is essentially a statistical method, not a visual one. In this review of current techniques and methods, several problems in current approaches are detailed. It is noted that feature definition can have significant effects on ultimate pattern differentiation. Sampling bias is also a major concern, as most microwear studies are carried out on samples which are very small. Compounding this are the effects of magnification level choices, and the effects of SEM instrumentation on feature visibility. Finally, the interpretation of pattern differences requires careful attention to comparisons of within-group and between-group variability.

Taste responses to amino acids in the southern leopard frog, Rana sphenocephala.

Integrated taste recordings of the glossopharyngeal (IX) nerve innervating the tongue of the southern leopard frog were studied in response to various amino acids and quinine hydrochloride. Amino acids and quinine hydrochloride elicited primarily phasic taste responses. Acidic (L-aspartic and L-glutamic) and basic (L-lysine and L-arginine) amino acids, adjusted to pH8, were effective taste stimuli. All glossopharyngeal nerve twigs that responded to amino acid stimuli also responded to quinine; however, not all quinine-sensitive IX nerve bundles were responsive to amino acids. Electrophysiological thresholds for amino acids were estimated to be 2.5-10 mM, whereas threshold for quinine hydrochloride averaged approximately 10 microM.

Hominoid dental microwear: complications in the use of microwear analysis to detect diet.

Analysis of dental microwear on chimpanzee molars reveals much variation that reflects jaw mechanics and occlusal function rather than diet. Observed microwear pattern differences relate to variations in molar position, facet type, and overall age of the tooth. Gradients in the amounts of shear and compression generated at different points in the molar series relative to the condyle probably account for pattern variations associated with molar position, while differences in facet inclination may affect the vectors of compression and shear, resulting in facet differences. Age-related pattern differences may be a result of surface and subsurface variations in enamel hardness. These results demonstrate that intraspecific and intra-individual differences in microwear may be extreme, and care must be taken to distinguish normal variation due to occlusal mechanics from variations due to dietary difference. The finding that microwear variations are reflective of subtle changes in occlusal forces and vectors along the tooth row might in itself be a clinically useful phenomenon.

Pitting and bubbling artefacts in surface replicas made with silicone elastomers.

Pitting or bubbling on the surface of epoxy resin replicas is a frequently encountered artefact associated with the use of silicone rubber impression materials. Several variants of this type of artefact are illustrated. It is suggested that bubbles or pits form at the mould:epoxy interface during curing of the epoxy, and that they are caused by gas escaping from the mould material itself. Duration of silicone rubber polymerization, base-catalyst ratios, and surface porosity of the object may all influence the occurrence of mould degassing.

The assessment of jaw movement direction from dental microwear.

In order to resolve several controversies about unusual jaw movements such as thegosis and orthal retraction, information about direction of jaw movement is essential. Ryan (1979a,b) proposed that asymmetry of microwear striations might provide such data. In vivo occurrences of asymmetric striations on chimpanzee molars are presented and analyzed. Results suggest that either thegosis contacts commonly occur on chimpanzee molars or that Ryan's model, as developed in vitro, does not accurately apply to naturally occurring molar microwear.

Orientation of occlusal contacts in the chimpanzee, Pan troglodytes verus, deduced from scanning electron microscopic analysis of dental microwear patterns.

Analysis of dental microwear may be used to detect species differences in diet and to secure information about occlusal relationships and biomechanics of the jaw. Microscratch-orientation data evaluated with reference to several hypotheses about functional, wear-related, sex and age influences on occlusal contacts indicated significant effects of facet type on scratch orientation, with less marked and sometimes paradoxical effects of molar wear and sex. Age per se seemed not to be related to scratch-orientation patterns. Orientations showed a considerable breadth of occlusal contact pathways, possibly indicating that in the chimpanzee, as in modern man, occlusal guidance is not precise.

Playing 'possum: a microwear experiment.

A recent experiment to evaluate the reliability of dental microwear as an indicator of diet seems to show that differences in diets fed to laboratory animals are not reflected by their tooth wear. We feel that these results are misleading, and reflect not so much the limits of microwear analysis per se, but rather result from the problems of design and execution inherent in any experimental simulation of natural feeding behavior. The experiment in question was flawed in several respects, and we think that changes in the methods and assumptions of the study are necessary before the experimental approach can yield meaningful results with which to test hypotheses about microwear analyses.

A study of microwear on chimpanzee molars: implications for dental microwear analysis.

Recent investigations of dental microwear have shown that such analyses may ultimately provide valuable information about the diets of fossil species. However, no background information about intraspecific variability of microwear patterns has been available until now. This study presents the results of an SEM survey of microwear patterns found on occlusal enamel of chimpanzee molars. Methods of pattern analysis are described. Selected sites on the occlusal surface included shearing, grinding, and puncture-crushing surfaces formed by both phases of the power stroke of mastication. The microwear patterns found in this sample of chimpanzees showed a high degree of regularity. However, certain parameters such as relative pit-to-striation frequencies, feature density, striation length, and pit diameter were significantly affected by facet type and molar position. Sex and age of individuals also influenced some microwear parameters, but due to the small sample size these findings are considered to be preliminary. These results show that microwear within a single species may vary because of factors that are due more to biomechanics than to diet. The study also supplies some metrical estimates of "normal" pattern variability due to functional and morphological influences. These estimates should provide a useful baseline for assessing the significance of microwear pattern differences that may be found between species of differing diets.