Hip joint forces in sheep

Testing orthopaedic implants at the proximal femur of sheep requires knowle dge of the contact forces acting on this joint. Telemeterized implants were used for long-term measurements of these forces in four sheep, mostly duri ng treadmill walking. Joint forces in the same sheep varied widely from day to day and interindividual differences were also pronounced. Forces during walking were mostly higher than in previous short-term measurements. At me dium walking speed, loads in the range of 65-140% of the body weight were t ypical. Fast walking increased the forces by only 20%, compared to slow spe ed. Stomping on the ground at the beginning of the stance phase and startin g to run freely led to very high forces. The highest values observed were n early four times the body weight. As in humans, the directions of high forc es varied only slightly in the frontal plane throughout the whole stance ph ase but much more in the transverse plane. With regard to the force magnitu des and their directions, sheep seem to be a good model for testing human i mplant at the proximal femur. (C)1999 Elsevier Science Ltd. All rights rese rved.