Narrow Results

The purpose of this paper was to investigate the anatomical location of the main axes of rotation of the knee, that is the axes of flexion-extension and longitudinal rotation. We compared 4 hypotheses on the correlation between the axis of flexion-extension and the femoral anatomy and 4 hypotheses on the correlation between the axis of longitudinal rotation and the tibial anatomy in 6 normal human knees. The methods used for the study were:. digitization by an electrogoniometer; computer reconstruction of motion and bone geometry, and an original geometrical interpolation to identify axes location. Our results suggest that: (a) the axis of flexion-extension lies in a cone spanned by the transepicondylar line and the so called FFc line;¹⁹ (b) the axis of longitudinal rotation can be represented by a line parallel to the tibial anatomical axis intersecting the flexion axis in a fixed point of the medial compartment.

A mathematical study is conducted of the oscillatory hydromagnetic flow of a viscous, incompressible, electrically conducting, non-Newtonian bio-fluid in an inclined, rotating channel with nonconducting walls, incorporating couple stress effects. The constitutive equations for a couple-stress fluid and the Maxwell electromagnetic field equations are presented and then reduced to a set of coupled partial differential equations for the primary and secondary flow. The model is then nondimensionalized with appropriate variables and shown to be controlled by the inverse Ekman number (K² = 1/Ek), the hydromagnetic body force parameter (M), channel inclination (α), Grashof number (Gr), Prandtl number (Pr), oscillation frequency (ω), and time variable (ωT). Analytical solutions are derived using complex variables. The influence of the governing parameters on the primary velocity (u), secondary velocity (w), temperature (θ), primary and secondary flow discharges per unit depth in the channel (Q_x, Q_z), and frictional shear stresses due to primary and secondary flow (τ_x, τ_z), are studied graphically and using tables. Applications of the study arise in the simulation of the manufacture of electrically conducting bio-polymeric liquids and magneto-physiological flow devices.

This paper discusses several new mechanisms that may be used in prostate cancer seed implant robotics. Aiming at the limitation of human body structure space, and in order to improve robotic kinematic dexterity and execution efficiency. We have developed an articulated seed implantation robot with three-dimensional transrectal ultrasound navigation. It is noteworthy that the organization will produce displacement, deformation and needle tip deflection and other issues while needle inserting prostate. In order to improve positioning accuracy of robot to control the puncture needle, a piezoelectric vibration and rotation needle insertion device is designed and developed. Based on the evaluation experiment of vibration and rotation needle insertion, a high accuracy mixed needle insertion strategy is proposed and the corresponding control software is designed. Finally, the insertion force evaluation experiment is completed by mixed needle insertion strategy, and the experimental results validate the effectiveness of this method.

Compared with fixed-bearing (FB) total knee arthroplasty (TKA), mobile-bearing (MB) TKA may promote knee rotation and reduce rotational load at bone–implant interface. Unfortunately, this hypothesis has not been examined with neither knee rotation during stance of pivoting nor knee rotational moment during activities other than level walking. This study used 3D motion analysis to obtain the rotation of tibia relative to the femur and knee rotation moment during stance phase of level walking, stair ascent/descent, step and spin turn for 17 FB, 20MB and 28 healthy knees. Statistical comparisons revealed that transverse plane biomechanics was similar between MB and FB knees. Compared with healthy knees ($7.8^{\circ }$), both FB ($3.8^{\circ }$) and MB knees ($4.1^{\circ }$) reduced internal rotation during step turn at early stance. During spin turn, FB knees ($10.5^{\circ }$ vs. $15.6^{\circ }$) reduced internal rotation at late stance, whereas MB knees ($-10.8^{\circ }$ versus $-15.4^{\circ }$) reduced external rotation at early stance. MB knees (0.064% and 0.126% body weight $\times$ height) had lower peak external rotation moments during early stance phase of both level walking and spin turn than healthy knees (0.108% and 0.238% body weight $\times$ height). Using FB for TKA surgery without bias and step-turn strategy for pivoting were recommended.

In this paper, we present and discuss a model of bone remodeling set up in the framework of the theory of generalized continuum mechanics which was first introduced by DiCarlo et al. [Sur le remodelage des tissus osseux anisotropes, Comptes Rendus Mécanique334(11):651–661, 2006]. Bone is described as an orthotropic body experiencing remodeling as a rotation of its microstructure. Thus, the complete kinematic description of a material point is provided by its position in space and a rotation tensor describing the orientation of its microstructure. Material motion is driven by energetic considerations, namely by the application of the Clausius–Duhem inequality to the microstructured material. Within this framework of orthotropic remodeling, some key features of the remodeling equilibrium configurations are deduced in the case of homogeneous strain or stress loading conditions. First, it is shown that remodeling equilibrium configurations correspond to energy extrema. Second, stability of the remodeling equilibrium configurations is assessed in terms of the local convexity of the strain and complementary energy functionals hence recovering some classical energy theorems. Eventually, it is shown that the remodeling equilibrium configurations are not only highly dependent on the loading conditions, but also on the material properties.