Force and torque modelling of drilling simulation for orthopaedic surgery

The advent of haptic simulation systems for orthopaedic surgery procedures has provided surgeons with an excellent tool for training and preoperative planning purposes. This is especially true for procedures involving the drilling of bone, which require a great amount of adroitness and experience due to difficulties arising from vibration and drill bit breakage. One of the potential difficulties with the drilling of bone is the lack of consistent material evacuation from the drill's flutes as the material tends to clog. This clogging leads to significant increases in force and torque experienced by the surgeon. Clogging was observed for feed rates greater than 0.5 mm/s and spindle speeds less than 2500 rpm. The drilling simulation systems that have been created to date do not address the issue of drill flute clogging. This paper presents force and torque prediction models that account for this phenomenon. The two coefficients of friction required by these models were determined via a set of calibration experiments. The accuracy of both models was evaluated by an additional set of validation experiments resulting in average R² regression correlation values of 0.9546 and 0.9209 for the force and torque prediction models, respectively. The resulting models can be adopted by haptic simulation systems to provide a more realistic tactile output.     

A biomechanical approach to the analysis of methods and procedures of bariatric surgery

Bariatric surgery includes a variety of procedures that are performed on obese people and aim at decreasing the intake of food and calories. This goal is usually pursued by reducing stomach capacity and/or absorbing capability. Adjustable gastric banding is the most common and successful operation. In general, bariatric surgical procedures are effective, but are often associated with major complications.Surgical procedure and post-surgical conformation of the stomach are usually defined on clinical and surgical basis only. Instead, the optimal configuration should be identified by analyzing the mechanical functionality of the stomach and the surrounding structures, and the relationship between food intake, nutrient adsorption, mechanical stimulation of stomach wall and feeling of satiety.A novel approach to bariatric surgery is required, integrating competences in the areas of biomechanics, physiology and surgery, based on a strong interaction between engineers and clinicians. Preliminary results from coupled experimental and computational investigations are here reported. The analyses aim to develop computational tools for the investigation of stomach mechanical functionality in pre- and post-surgical conformations.     

Binge Eating and Eating‐Related Cognitions and Behavior in Ethnically Diverse Obese Women

Objective: To examine binge eating and eating‐related cognitions and behavior in a sample of ethnically diverse women who are severely obese and seeking bariatric surgery. Research Methods and Procedures: Female bariatric surgery candidates (62 African Americans, 18 Latinas, 130 whites) completed questionnaires on binge eating and eating‐related cognitions and behavior and completed a structured clinical interview to confirm binge‐eating disorder diagnosis. Results: Ethnic minorities and whites did not differ in rates of binge‐eating disorder (26.3%), binges per week (M = 0.95), or dietary restraint. Ethnic minorities reported less disinhibition, and there was a trend to report less hunger awareness than whites. After controlling for BMI and education, ethnicity accounted for significant variance in disinhibition (4%; p < 0.01). Ethnic minorities were younger, became overweight at a later age, and were overweight for fewer years than whites. Discussion: Results suggest that ethnicity exerts an important influence on disinhibition and that ethnic differences are not caused by BMI or education. Findings point to the need to continue to investigate the role of ethnicity, binge eating, and disinhibition in severely obese women, so that culturally appropriate services can be provided.     

Study on the enzymatic 5′-deiodination of 3′,5′-diiodothyronine using a radioimmunoassay for 3′-iodothyronine

A radioimmunoassay for 3′-iodothyronine has been developed. All iodothyronine analogues (except 3,3′-diiodothyronine) showed very little (0.02% at most) cross-reactivity, and the assay was sensitive to 1 pg 3′-iodothyronine/ tube. We have studied the 5′-deiodination of 3′,5′-diiodothyronine by rat liver microsomal fraction in the presence of dithiothreitol. Production of 3′-iodothyronine at 37°C was found to be linear with time of incubation up to 30 min and with concentration of microsomal protein up to 100 μg/ml. The reaction rate reached a limit on increasing 3′,5′-diiodothyronine concentration to 10 μM. The effect of pH on 3′-iodothyronine production was found to depend on 3′,5′-diiodothyronine concentration. Increasing 3′,5′-diiodothyronine concentration from 0.1 to 10 μM resulted in a shift of the pH optimum from 6–6.5 to 7.5. Similar effects on the 5′-deiodination of 3,3′,5′-triiodothyronine were observed, supporting the hypothesis that these reactions are catalysed by a single enzyme (iodothyronine 5′-deiodinase).     

Stimulation of glucose utilization and lactate production in cultured human fibroblasts by thyroid hormone

Human dermal fibroblasts were obtained by harvesting outgrowing cells from the dermal tissue explants and cultured in Dulbecco's modified Eagle medium containing 10% fetal calf serum. After the cells reached confluency, culture was continued in the medium containing calf serum which was deprived of thyroid hormone by the treatment with activated charcoal. These fibroblasts were responsive to exogeneously added thyroid hormone (triiodothyronine) at physiological concentrations, resulting in enhanced utilization of glucose and production of lactate. This stimulation by thyroid hormone was dependent upon the length of exposure to the hormone and its concentration.The hormone did not show any effects on cellular DNA and protein content. The experimental system described above seems to be easy to reconstitute and should be useful for the elucidation of the mechanism of thyroid hormone action.     

Efficient use and recycling of the micronutrient iodide in mammals

Daily ingestion of iodide alone is not adequate to sustain production of the thyroid hormones, tri- and tetraiodothyronine. Proper maintenance of iodide in vivo also requires its active transport into the thyroid and its salvage from mono- and diiodotyrosine that are formed in excess during hormone biosynthesis. The enzyme iodotyrosine deiodinase responsible for this salvage is unusual in its ability to catalyze a reductive dehalogenation reaction dependent on a flavin cofactor, FMN. Initial characterization of this enzyme was limited by its membrane association, difficult purification and poor stability. The deiodinase became amenable to detailed analysis only after identification and heterologous expression of its gene. Site-directed mutagenesis recently demonstrated that cysteine residues are not necessary for enzymatic activity in contrast to precedence set by other reductive dehalogenases. Truncation of the N-terminal membrane anchor of the deiodinase has provided a soluble and stable source of enzyme sufficient for crystallographic studies. The structure of an enzyme·substrate co-crystal has become invaluable for understanding the origins of substrate selectivity and the mutations causing thyroid disease in humans.     

Scintigraphy has the potential to replace thyroid stimulating hormone and ultrasonography in hyperthyroidism diagnosis

The value of thyroid scintigraphy in hyperthyroidism diagnosis has long been the subject of debate. Unresolved issue is whether scintigraphy should be performed routinely, selectively, or for all hyperthyroidism patients. So, this study is concerned with the evaluation of thyroid scintigraphy for identifying hyperthyroidism in comparison with thyroid stimulating hormone (TSH) and ultrasound. This is cross sectional study including convenient patients sample (n = 50, 15 males and 35 females) aged (20–50 years) with primary hyperthyroidism and were attending endocrine clinics at King Faisal Specialist Hospital and Research Centre. All patients performed clinical investigations (TSH, ultrasound and thyroid scintigraphy). Among these patients, 96%, 48/50, had positive findings for hyperthyroidism with thyroid SC (95% CI; 96.0–99.5%); 84%, 42/50, had positive findings for hyperthyroidism by US (95% CI; 70.9–92.8%); and 56%, 28/50, had positive findings for hyperthyroidism by TSH measurement (95% CI; 41.3.0–70.0%). There was very good agreement between scintigraphy diagnosis and ultrasonography (kappa score = 0.812 (P < 0.0001), 95% CI (0.77–0.85). In many cases, scintigraphy provides considerably more functioning and anatomic details than ultrasound. In conclusion, these findings bring forth practical aspects of thyroid scintigraphy utilization for hyperthyroidism. By combining functional and anatomical information in one step, scintigraphy provides non-invasive, simple, fast and cost effective hyperthyroidism diagnostic method and has the potential to replace TSH and ultrasonography in hyperthyroidism investigation.     

Effect of gelatin on the cyclic AMP response of primocultured hog thyroid cells to acute thyrotropin stimulation

The cyclic AMP response of cultured hog thyroid cells to acute thyrotropin stimulation was shown to be under a dual regulatory control by thyrotropin: both positive and negative regulation have been described. When added to the culture medium, gelatin (0.25%) promoted the reorganization of the cells into follicle-like structures, as does thyrotropin. Unlike thyrotropin, gelatin did not induce an increase in intracellular cyclic AMP but enhanced the acute cyclic AMP response to thyrotropin in cells cultured in gelatin-containing medium. When both gelatin and thyrotropin were present, the positive effect of low concentrations of hormone (less than 50 μU/ml) was increased whereas the refractory process observed in the presence of higher concentrations of hormone (greater than 50 μU/ml) was unchanged. These effects of gelatin might be mediated by interaction of the denatured collagen molecules with external proteins of the plasma membrane of thyroid cells.     

Autofluorescence imaging for recurrence detection in skin cancer postoperative scars

This clinical study is a first attempt to use autofluorescence for recurrence diagnosis of skin cancer in postoperative scars. The proposed diagnostic parameter is based on a reduction in scar autofluorescence, evaluated in the green spectral channel. The validity of the method has been tested on 110 postoperative scars from 56 patients suspected of non‐melanoma skin cancer, with eight patients (13 scars) available for the repeated examination. The recurrence diagnosis within a scar has been made after two subsequent autofluorescence check‐ups, representing the temporal difference between the scar autofluorescence amplitudes as a vector. The recognition of recurrence has been discussed to represent the significant deviations from the value of vector angle θ. This new autofluorescence‐based method can be easily integrated into the postoperative monitoring of surgical scars and can help diagnose the recurrence of skin cancer from the early stage of scar development.     

The influence of limb alignment and transfemoral amputation technique on muscle capacity during gait

Many factors influence successful outcomes following transfemoral amputation. One factor is surgical technique. In this study, the influence of limb alignment and surgical technique on a muscle’s capacity to generate force was examined using musculoskeletal modeling. Non-amputee and transfemoral amputee models were analyzed while hip adduction, femur length, and reattached muscle wrap position, tension and stabilization technique were systematically varied. With muscle tension preserved, wrap position and femur length had little influence on muscle capacity. However, limb alignment, muscle tension and stabilization technique notably influenced muscle capacity. Overall, myodesis stabilization provided greater muscle balance and function than myoplasty stabilization.