- Email: [email protected]
Investigation of the hay-high jump technique by computer simulation
Abstracts of the Fourth Meeting of the European Society of Biomechanics
554
MECHANICAL LOAD ON THE ACHILLES TENDON DURING RAPID DYNAMIC SPORT MOVEMENTS
P. BR~~GGEMANN (Deutsche Sporthochschule
Koln, F.R.G.)
The purpose of this study was to estimate the magnitude of the force, which loads the achilles tendon during rapid dynamic movements. The chosen movement was the take-off of the backward somersault on floor because of the numerous accidents (ruptures) in this area. For calculating the load of the achilles tendon the spatial vector of the net muscle moment of the ankle joint, using the spatial coordinates of the joint center, the point of application of the force and the ground reaction forces, was calculated. Then the net muscle moment vector was divided into net muscle moments produced by the m. triceps surae, m. tibialis anterior, m. extensor and flexor hallucis longus and m. peroneus longus. Thus it was possible to estimate the net muscle forces, as well as the load of the tendons. INVESTIGATION
OF THE HAY-HIGH JUMP TECHNIQUE BY COMPUTER SIMULATION
R. PREI~ (Institut fur Sportwissenschaften,
6000 Frankfurt
90, F.R.G.)
The proposed high jump technique by J. Hay in 1973 was based on biomechanical considerations and promised an essential improvement in high jump results. Practical experiments of this technique have so far yielded no improvements. Therefore we decided to use a mathematical model in order to simulate the movement. A two-dimensional mathematical mode1 consisting of six rigid segments for airborne movements was constructed. The inertial parameters of the human body were calculated by a modified Hanavan-model. The computer simulation indicated that the predicted improvements in height could not be achieved. The main problem is to have only a small amount of rotation of the body during the ascending phase and a fast rotation during the clearance of the bar. S. GENERAL
FINITE ELEMENT MODELING
TOPICS
OF IMPLANTS IN BONE: INTERFACIAL ASSUMPTIONS
J. A. HIPP, J. B. BRUNSKI, M. S. SHEPHARDand G. V. B. COCHRAN(Rensselaer Polytechnic Institute,
Troy, NY 12181, U.S.A.) Finite element (FE) modeling can be an important tool in efforts to understand the loosening of orthopaedic and dental implants in bone. The fidelity with which an FE analysis represents reality depends on the assumptions used in the modeling. The special importance of the assumptions made regarding tissue-implant interfacial mechanics was examined by FE analysis of three problems using two limiting interface assumptions. FE models assuming perfect bonding between implant and bone produced significantly different results than FE models assuming frictionless boneimplant contact. Not only were the stresses quantitatively and qualitatively different, but the frictionless models predict relative displacements between implant and bone. This study makes the following point: if one wishes to use FE models to understand the loosening problem with orthopaedic and dental implants, then the mechanics of the implant-tissue interface must be accurately represented in the model. THE INFLUENCE OF FRICTION ON STABILITY OF THE INTERFACE IN HIP ENDOPROSTHESES
D. GEBAUER(Bergische Universitlt
GH Wuppertal, F.R.G.)
The friction torque in artificial joints is often accused of inducing loosening of cemented implants. To find out the influence of these torques during walking they were measured by a new self-constructed hip simulator. On the contrary to other simulators the physiological bending of the pelvis is imitated by implanting the cup in a bending frame. The transposition of the measured torques under dry friction to shear stresses in the interface showed that the stresses do not reach the level of critical values measured by Kiilbel. The comparison with experimental loosening torques of the cup investigated by Andersson and Jager also demonstrated that the friction alone cannot induce a loosening of the cup. LOADABILITY OF THE INTERFACE IN ARTIFICIAL JOINTS
D. GEBAUER*,H. HAGER~ and S. BRErERt (*Berg&he Universitlt Miinchen, F.R.G.)
Wuppertal, tTechnische Universitat
Standardized samples of cement-bone joints were loaded by static and dynamic shear- and pressure-forces, as they occur in hip endoprostheses, to find out the influence of biomechanical effects on aseptic loosening.
554
MECHANICAL LOAD ON THE ACHILLES TENDON DURING RAPID DYNAMIC SPORT MOVEMENTS
P. BR~~GGEMANN (Deutsche Sporthochschule
Koln, F.R.G.)
The purpose of this study was to estimate the magnitude of the force, which loads the achilles tendon during rapid dynamic movements. The chosen movement was the take-off of the backward somersault on floor because of the numerous accidents (ruptures) in this area. For calculating the load of the achilles tendon the spatial vector of the net muscle moment of the ankle joint, using the spatial coordinates of the joint center, the point of application of the force and the ground reaction forces, was calculated. Then the net muscle moment vector was divided into net muscle moments produced by the m. triceps surae, m. tibialis anterior, m. extensor and flexor hallucis longus and m. peroneus longus. Thus it was possible to estimate the net muscle forces, as well as the load of the tendons. INVESTIGATION
OF THE HAY-HIGH JUMP TECHNIQUE BY COMPUTER SIMULATION
R. PREI~ (Institut fur Sportwissenschaften,
6000 Frankfurt
90, F.R.G.)
The proposed high jump technique by J. Hay in 1973 was based on biomechanical considerations and promised an essential improvement in high jump results. Practical experiments of this technique have so far yielded no improvements. Therefore we decided to use a mathematical model in order to simulate the movement. A two-dimensional mathematical mode1 consisting of six rigid segments for airborne movements was constructed. The inertial parameters of the human body were calculated by a modified Hanavan-model. The computer simulation indicated that the predicted improvements in height could not be achieved. The main problem is to have only a small amount of rotation of the body during the ascending phase and a fast rotation during the clearance of the bar. S. GENERAL
FINITE ELEMENT MODELING
TOPICS
OF IMPLANTS IN BONE: INTERFACIAL ASSUMPTIONS
J. A. HIPP, J. B. BRUNSKI, M. S. SHEPHARDand G. V. B. COCHRAN(Rensselaer Polytechnic Institute,
Troy, NY 12181, U.S.A.) Finite element (FE) modeling can be an important tool in efforts to understand the loosening of orthopaedic and dental implants in bone. The fidelity with which an FE analysis represents reality depends on the assumptions used in the modeling. The special importance of the assumptions made regarding tissue-implant interfacial mechanics was examined by FE analysis of three problems using two limiting interface assumptions. FE models assuming perfect bonding between implant and bone produced significantly different results than FE models assuming frictionless boneimplant contact. Not only were the stresses quantitatively and qualitatively different, but the frictionless models predict relative displacements between implant and bone. This study makes the following point: if one wishes to use FE models to understand the loosening problem with orthopaedic and dental implants, then the mechanics of the implant-tissue interface must be accurately represented in the model. THE INFLUENCE OF FRICTION ON STABILITY OF THE INTERFACE IN HIP ENDOPROSTHESES
D. GEBAUER(Bergische Universitlt
GH Wuppertal, F.R.G.)
The friction torque in artificial joints is often accused of inducing loosening of cemented implants. To find out the influence of these torques during walking they were measured by a new self-constructed hip simulator. On the contrary to other simulators the physiological bending of the pelvis is imitated by implanting the cup in a bending frame. The transposition of the measured torques under dry friction to shear stresses in the interface showed that the stresses do not reach the level of critical values measured by Kiilbel. The comparison with experimental loosening torques of the cup investigated by Andersson and Jager also demonstrated that the friction alone cannot induce a loosening of the cup. LOADABILITY OF THE INTERFACE IN ARTIFICIAL JOINTS
D. GEBAUER*,H. HAGER~ and S. BRErERt (*Berg&he Universitlt Miinchen, F.R.G.)
Wuppertal, tTechnische Universitat
Standardized samples of cement-bone joints were loaded by static and dynamic shear- and pressure-forces, as they occur in hip endoprostheses, to find out the influence of biomechanical effects on aseptic loosening.