Key Engineering Materials Vols. 326-328

Abstract: This paper reports the development and preliminary experiments of a robotic system designed to perform needle manipulation tasks in medical applications. A hybrid type manipulator is designed to enlarge the workspace without loss of position accuracy. In this paper, we initially analyze the workspace and step resolution of the robotic system in the operational space. Then, we perform trajectory tracking experiment to verify that the developed robotic system could be employed to attenuate an unpredictable tremor of human operators and enhance position accuracy in neurosurgery or ophthalmic surgery, etc. It is shown through experimentation that the robothuman cooperation mode is effective for micro-manipulation tasks.

Abstract: We design the biomechanical skin measurement system which is assembled with multi-components load cell and actuator. The multi-components load cell simultaneously measures the normal load (Fz), and moniter (Fx, Fy) with strain gages. Capacity and accuracy of load cell are less than 5 N and 0.1%. In this research, designed measurement system applies to determine in-vivo viscoelasticity of human skin.

Abstract: In this paper, we performed the dynamic measurement and modeling of soft tissue with removing samples from the main body to characterize the soft tissue properties for medical simulations. The measurement method made various patterns of normal surface indentations of a soft tissue. Next, the reaction forces through the indenter were measured using a force transducer. From the force-displacement profile, the nonlinear properties were observed in a relatively small deformation range and the frequency responses of the tissue were obtained using a series of sinusoidal indentations below 3 Hz. We developed a viscoelastic model of the tissues from the recorded force-displacement profiles, from which we can develop a model to predict the behavior of the tissues. The developed model, combined with the anatomical model, could provide a visible deformation and haptic feedback for virtual reality based medical simulations.

Abstract: The effect of carbonated apatite powder size on the carbonated apatite embedded on titanium alloy was studied. The process was conducted using superplastic deformation method at 750oC and initial pressure of 34MPa. In order to evaluate the characteristics of the resulting embedded layer, X-ray diffraction method was conducted followed with microstructure characterization. From X-ray diffraction characterization, it can be concluded that small stress layers of carbonated apatite were resulted for all samples with different initial powder size. In addition, initial powder size of carbonated apatite only significantly influences the intensity of diffraction peak for certain plane of crystal structure. From the experimental results, it can also be concluded that superplastic deformation can be used as an alternative method for the coating process of bio apatite material on titanium alloy substrate

Abstract: In recent years, embedded fibre-optic sensors as structural health monitoring devices have been widely used in both civil and aerospace engineering applications. Their small physical size and ability to immunize electromagnetic interference make them ideal sensing devices, which provide highly accurate and reliable strain and temperature measurements for structures. This paper presents a new designed temperature-compensated fibre-optic Bragg grating (TCS) strain sensor for imbedding into cement-based materials to measure their mechanical and thermal strains individually or simultaneously. However, the residual stress generated due to the constrained boundary of a steel tube that is used to protect the sensor, will influence the accuracy of measurement. Therefore, a theoretical model that is used to estimate this stress at different temperature conditions is discussed.

Abstract: The elastic modulus and the apparent density of the trabecular bone were evaluated from spherical indentation tests and Computed Tomography and their relationship was quantified. After the femurs were prepared and embedded with respect to their anatomical orientation, the transverse planes of the trabecular bone specimens were scanned at 1mm intervals using a CT scanner. The metaphyseal regions were sectioned with a diamond-blade saw, producing 8mm cubes. Using a custom-made spherical indentation tester, the cubes were mechanically tested in the anteriorposterior (AP), medial-lateral (ML), and inferior-superior (IS) directions. After determination of modulus from the mechanical testing, the apparent densities of the specimens were measured. The results showed that the IS modulus was significantly greater than both the AP and ML moduli with the AP modulus greater than the ML modulus. This demonstrated that orthogonality was a structural characteristic of the trabecular bone. The power relationship between the modulus and the apparent density was also found to be statistically significant.

Abstract: An understanding of the mechanical responses of the patellar tendon (PT) subunits should aid in determining which portion of the tissue might best be used as a cruciate ligament replacement. Human cadaveric knees were obtained from young donors. Fascicle groups with patellar and tibial bone blocks (subunits) were cut to provide six equally-spaced test specimens for each PT. After potting each bone end in PMMA, specimens were mounted in a saline-filled chamber, preloaded to 0.26 N and then subjected to 40 cycles of preconditioning to 2.5 % of the initial length at a strain rate of 1.25 %/sec, and then preloaded to 0.26 N again and failed at a strain rate of 100 %/sec using an Instron. The moduli and maximum stresses were generally greater in the lateral and mid subunits than in the medial subunits. The strains to maximum stress were similar between the lateral and medial subunits, but mid subunits had larger strains. Most strain values were distributed between 10 % to 20 %. Mechanical responses of human PT do vary from location to location. In general, the mid and lateral subunits were stiffer and carried greater stresses than the medial subunits. The results of this research should eventually be important, e.g. in selecting which portion of the PT would be the most suitable for cruciate ligament replacements to use as an autograft. On the basis of strength and stiffness, the more lateral portion of the PT would seem to be more advantageous.

Abstract: There are increasing incidence of Hangman fracture with the development of society and industrialization. The research on upper cervical spine concerning hangman fracture is able to be well carried on with The finite element method(FEM) developing. The research includes a biomechanical experiment of cadaver specimens and FEM analysis accordingly. The finite element models of geometrical complex structure from medical images are generated automatically, the research presents simulation of different surgical option of hangman fracture, testified the models by loads, calculated the stabilities and stress of models. The corresponding results were summarized with experiment of cadaver specimens. The research demonstrate that clinical therapeutics is an good option for Hangman fracture with C2-3 inter-vertebral disc injury.

Abstract: The optimal femoral cancellous bone angle is estimated in order to design the femoral IM (Intra-Medullary) nail for patients with more precise method based on CT image of the femur by converting the CT image files into the JPEG files and analyzing the mathematical models with MATLAB (Ver. 6.0). The results show that the measured average ℓ(femur length between Lesser trochanter and greater trochanter) of the right femoral cancellous bones out of 40 Korean males is 356.6 mm whereas the measured average ℓof the Caucasians is 430 mm and the estimated lateral bowing angle( of Korean males is 4.53°±0.93° whereas the estimated lateral bowing angle of the Caucasians is 4.2°±2.3°. Moreover, we have found that the longer femur is bended more than the shorter one and the distribution of the femoral bone length is not the Gaussian profile. This suggested method has a potential to estimate each patient’s femoral cancellous bowing angle more precisely. If the bowing angle of the lateral images of each patient can be estimated immediately through medical image data, it could be easier for surgeons to choose appropriate nails that are most suitable for each patient. More investigations can be achieved by collecting more data for patient’s femoral curvature.

Abstract: Objective. To determine whether the load-carrying capacity of human proximal femora with simulated lytic defects can be predicted using QCT-derived simplified beam theory. Design. The predicted fracture load of simulated defects were calculated using new technique of QCT combined with engineering beam analysis. Patients. Simulated lytic defects were created using a surgical drill in the intertrochanteric region of twenty human cadaveric femora. QCT scans were conducted before and after creating defects on either AM (Anterior-Medial) or PL (Posterior-Lateral) regions. Results. A linear relation could be used to predict failure load from the proposed engineering analysis based on QCT scan. The coefficient of determination analysis of QCT-derived predicted load vs. the measured failure load was R2=0.73 (p<0.0001). Conclusions. The data suggest that three quarters of human femoral failure can be predicted in vivo, i.e. using QCT scan. Combined with information on the loads associated with the activities of daily living, these data may be used to prevent pathologic fractures of patients who had prior surgery of removing tumors on proximal femurs.