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Conventional surgical navigation requires for surgeons to move their sight and conscious off the surgical field when checking surgical tool’s positions shown on the display panel. Since that takes high risks of surgical exposure possibilities to the patient’s body, we propose a novel method for guiding surgical tool position and orientation directly in the surgical field by a laser beam. In our navigation procedure, two cross-sectional planar laser beams are emitted from the two laser devices attached onto both sides of an optical localizer, and show surgical tool’s entry position on the patient’s body surface and its orientation on the side face of the surgical tool. In the experiments, our method gave the surgeons precise and accurate surgical tool adjusting and showed the feasibility to apply to both of open and percutaneous surgeries. [ABSTRACT FROM PUBLISHER]

Objectives: We investigated the effect of cartilage degeneration on ultrasound speed in human articular cartilage in vitro., Methods: Ultrasound speed was calculated by the time-of-flight method for 22 femoral condyle osteochondral blocks obtained from osteoarthritis patients. In parallel, histological evaluation of specimens was performed using the modified Mankin and OARSI scores., Results: The mean ultrasound speed was 1757 ± 109 m/s. Ultrasound speed showed significant negative correlation with OARSI score, and a decreasing tendency with high Mankin scores. Good correlation was found between the optically measured and the calculated cartilage thickness., Conclusion: Our results show that articular cartilage degeneration has relatively little influence on ultrasound speed. In addition, morphological evaluation of articular cartilage using a preset value of ultrasound speed seems to offer relatively accurate results.

Objective: The objective of this study was to investigate the factors that affect the predicted bone strength of proximal femur in Japanese population., Methods: Participants (552 men and 273 women) in a health checkup program with computed tomography (CT) at the University of Tokyo Hospital were enrolled in this study. Three-dimensional finite element models of the proximal femur were constructed from CT data of the participants with simultaneous scans of a calibration phantom containing hydroxyapatite rods. Multiple regression analysis was performed to analyze the relationship between the predicted bone strength and clinical factors., Results: Average predicted strength of proximal femur was lower in women than in men in all age ranges. Predicted bone strength in women under both stance and fall configurations significantly decreased with age, and that in men had the tendency to decrease with age. Body weight positively affected the predicted bone strength in both men and women., Conclusions: This is the first cross-sectional analysis of the predicted bone strength of the proximal femur in Japanese population of wide age range. Age and body weight critically affected bone strength of proximal femur determined by quantitative CT-based finite element method, in particular in women, under both stance and fall configurations.

Clinically available methods for estimating bone strength include bone densitometry techniques such as dual energy X-ray absorptiometry and quantitative computed tomography, and other diagnostic imaging procedures such as radiographic imaging. These techniques evaluate regional bone density and morphology, which are partly related to fracture risk, but are of limited value for quantifying structural strength. Therefore, it is necessary to develop a noninvasive method for accurate quantitative structural analysis that incorporates information on both morphology and bone density in a three-dimensional distribution. Computed tomography-based finite element method (CT/FEM), which incorporates information on both the three-dimensional architecture and bone density distribution, could possibly achieve precise assessment of the strength of the bone. We focused on a CT/FEM to quantify structural strength, developing a nonlinear CT/FEM to achieve accurate assessment of strength in the proximal femur and lumbar vertebrae. Here, we describe the CT/FEM.

Gelatin hydrogels cross-linked by y-ray irradiation using 60Co as gamma-ray source were prepared. As a model of controlled release of low-molecular-weight compounds, absorption and release of methylene blue, a water-soluble cationic dye, was investigated. Irradiated gelatin hydrogels did not redissolve at temperatures over 40 degrees C, while unirradiated gels were thermoplastic and reversibly changed the stage between gel and sol. Measurement of both the wet weight after swelling in distilled water and dry weight after freeze-drying showed that the higher-dose irradiation gave stiffer and more compact gels with the lower specific water content, irrespective of the absorbed dose rate. The time-course of absorption and release of methylene blue in aqueous solution was measured. Since absorption of dye into gelatin gels was much affected by liquid phase pH, amount of absorption was higher in pH above an IEP of gelatins. Moreover, the absorption and release of methylene blue with Type-B gelatin were higher than with Type-A gelatin, respectively. Therefore, absorption and release of the dye depend on the electrostatic interaction between the dye molecule and gelatin.