Plane joint

Abstract: THIS STUDY APPLIES THE FINITE ELEMENT METHOD TO A THREE- DIMENSIONAL ANALYSIS OF DISPLACEMENTS AND STRESSES WITHIN ROCK SLOPES CONTAINING JOINTS OF ARBITRARY ORIENTATION AND EXTENT THE ROCK SLOPE IS IDEALIZED AS AN AGGREGATE OF TWO DISTINCT SETS OF PHYSICAL ELEMENTS: THE THREE-DIMENSIONAL ROCK BLOCKS AND THE TWO-DIMENSIONAL JOINT ELEMENTS PLANE JOINT ELEMENTS OF TRIANGULAR AND QUADRILATERAL SHAPE ARE DEVELOPED BY AN EXTENSION OF THE LINE JOINT ELEMENT CONCEPT THE SOLID ELEMENTS REPRESENTING ROCK BLOCKS ARE COMPOSED FROM TETRAHEDRA ON THE BASIS OF THE ANALYSIS, A COMPUTER PROGRAM IS DEVELOPED TO EXAMINE THE BEHAVIOR OF JOINTED ROCK SLOPES UNDER INITIAL, BODY, AND BOUNDARY LOADS /AUTHOR/

Abstract: An experimental study of the subtalar joint has been conducted with the aim of establishing its axis of movement as well as analysing the associated movement. For description of the axis, CT data for five positions of a single foot were reconstructed using a 3D programme, the 3D data was processed by Patran software. Measures of angular displacements were made from three amputated feet placed in a specially constructed foot frame. Four instantaneous axes of movement could be defined. Calculation of displacements showed an important rolling of the calcaneus (45r). Tacking was evident in inversion, with an opposite displacement between the front and rear part of the calcaneus, whereas during eversion tacking affected only the rear part of the bone these results were confirmed by 3D reconstructions. Henke’s axis was described as that for the talonavicular joint, but acceptable for the subtalar joint. Several authors investigating the coordinates of this axis have reported large differences and described screw-like movements, the latter being incompatible with a fixed axis instantaneous axes, however are compatible with a screw-like movement. The subtalar joint appears to work as a pivot joint during inversion and as a plane joint during eversion. Although Henke’s axis has pedagogical value the subtalar joint has a series of instantaneous axes.

Abstract: Compared with running straight, when human runners sprint along a curve, the ability of the inside leg to generate force is compromised. This decreased force generation has been suggested to limit the overall performance of the runner. One theory for this force loss is that the large non-sagittal plane joint moments of the inside leg reach their operating limits, thus prohibiting further generation of the performance-related sagittal plane joint moments. We investigated the inside leg force generation and the ankle and knee joint moments when 13 subjects sprinted with and without an additional mass of 12.4 kg along a curve of 2.5 m radius. The increase in the subjects' mass evoked a significant increase in the resultant ground reaction force. The peak non-sagittal plane moments increased significantly for both the ankle and knee joints. This observation suggests that when sprinting normally with maximum effort, the non-sagittal plane joint moments are not operating at their limits. The large increases in ground reaction force were associated with greater extension moments generated at the knee joint. In contrast, the peak ankle plantarflexion moment remained unchanged across conditions. It is possible that for the specific joint configuration experienced, the overall ability to generate plantarflexion moment reaches the limit. Future studies with interventions increasing the ability of the muscle-tendon units to generate plantarflexion moment may provide an experimental opportunity to further examine this speculation.