Meeting Abstract

112.5  Saturday, Jan. 7  In vivo locomotor mechanics of the tarsometatarsus bone in juvenile emus LAMAS, L.P.*; MAIN, R.P.; SHEFELBINE, S.; HUTCHINSON, J.R.; The Royal Veterinary College, UK; Purdue University, Indiana, USA; Imperial College London, London, UK; The Royal Veterinary College, London, UK llamas@rvc.ac.uk

Emus(Dromaius novaehollandiae) have become increasingly popular models for pelvic limb (PL) mechanics. Strain gauge (SG) measurements of the loading patterns from PL bones offer are essential to test the accuracy of computer modelling approaches such as finite element analysis (FEA). If localized SG results match FEA estimates then this would build confidence in FEA, which can estimate strains throughout an entire bone including regions such as muscle attachment sites and joint surfaces for which strains are extremely difficult to determine experimentally. Previous mechanical studies of emu PL bone strains have demonstrated that both the femur and tibiotarsus (TBT) are predominantly loaded under shear strains induced by torsional loads. Although these loading patterns are maintained during ontogeny, the femora and TBT of emu scale with mixed allometry during growth. Unlike the femur and the TBT, no information is yet available on the loading patterns of the more distal tarsometatarsus (TMT) bone. Is the TMT similarly loaded in torsion like the more proximal femur and TBT? To answer this question, in vivo bone strains from the TMT were measured in juvenile (one 6week old and three 30 week old) emus. Simultaneous 3D kinematics of the limb and ground reaction forces were also obtained from these animals. Our results suggest that the TMT does not follow the loading pattern of the more proximal bones, being loaded predominantly in bending, not torsion. This suggests that the torsional strains measured for the proximal bones originate from either hip joint contact forces or, more likely, from internal muscle and other soft tissue forces, which are dissipated before reaching the TMT.