Biomechanical study of grasping among primates: evolutionary perspectives

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Journal o f Biomechanics 2006, Vol. 39 (Suppl 1)

References [1] Blickhan R. Biomechanik der axialen aquatischen und pedalen terrestrischen Lokomotion. Habilitationsschrift, Universit~t des Saarlandes 1992. 4086 Mo-Tu, no. 10 (P67) Biomechanical study o f grasping among Primates: evolutionary perspectives E. Pouydebat 1, P. Gorce 2, V. Bels 1. 1MNHN, USM 302, Paris, France, 2LESR

Universit# de Toulon et du Var, La Garde, France The relation between the evolution of Primates and the development of grasping behaviours allowing exploiting resources of their environment has been studied through a pluridisciplinary analysis on the basis of experimental studies. Our procedures of analyses consisted in comparative analysis of kinematics of limb and digit movements of one arboreal species of Platyrrhini, the capuchin, five species of Catarrhini and human during different tasks (grasping of food of different sizes and tool use). The questions were to know (i) if actual primates presented specific characteristics, structural, functional and behavioural linked to their modes of grasping, (ii) if it was possible to trace an evolution of these characteristics and to group species according to biomechanical characteristics and finally, (iii) if the grasping was a pertinent argument to define the human kind. We focussed on areas of contact between the grasping fingers to assess the relationship between grip types and food physical properties. Statistics were used to test the effects of the physical parameters of the food on (i) the digit areas used for grasping techniques, (ii) the kinematics properties of limb and digit movements during each of these techniques and (iii) the cognitive characteristics during complex grasping tasks. The results show that the object size and the task accomplished had an effect on the mode of grasping. More, the platyrrhinian and all catarrhinian primates were able to modulate their grasping techniques in strong relationship with food properties, independently of their phylogenetic relationship. For the first time, it has for example been demonstrated that all species studied are able to grasp small objects with precision (defined by Napier as the opposition of the distal phalanx of the index and the thumb). These data are used to discuss the simplest model of grasping evolutionary usually proposed in the literature to understand the evolution of the cognitive and functional grasping capacities of primates. 7407 Mo-Tu, no. 11 (P67) Validation o f a computer model of the equine frontlimb for simulating tendon strains in relation to bone and joint geometry R. Weller 1, G. Lichtwark 1, R. Payne 1, T. Pfau 1, A. Wilson 1,2. 1Structure

and Motion Lab, The Royal Veterinary College, University of London, UK, 2Structure and Motion Lab, University College London, The Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex, UK Introduction: Quantification of tendon strain and stress is essential in the investigation of the aetiopathogenesis oftendinopathies. Several computational models have been developed to determine the strain in horse tendons noninvasively, however none of these models allowed for the adjustment of leg geometry or muscle-tendon properties to match individual horses. Hypotheses: (1) stable computer models of can be created based on the data from individual horse legs (2) the tendon strain predicted by the computer model is closer to the experimentally measured tendon strain for the individual horse than to the average tendon strain of the sample population Materials and Methods: Leg geometry and muscle-tendon properties were determined for nine elbow-down equine frontlegs in a series of experiments [1]. Based on these data a computer model of each leg was built within the software package SIMM (MusculoGraphics Inc., USA). The models were validated by simulating axial compression of the leg to the maximum force measured in the experiments. The output was then compared to the experimental data. Results: Stable computer models were created for all legs. Tendons strains however were only successfully modelled for one type of tendon. For the majority of tendons the model underestimated tendon strain. Conclusion: Horse legs can reach a stable configuration in a variety of combinations of joint/segment geometry and muscle-tendon properties, which could be simulated in the computer model. It was not possible to predict the strain the tendons accurately and future work will concentrate on identifying how different sources of error influence these predictions. References [1] Weller R., Payne R.C. and Wilson A.M. Dissecting the pogostick: Are all horse legs equivalent? Comparative Biochemistry and Physiology Part A 2004; 137(96).

Poster Presentations 7122 Mo-Tu, no. 12 (P67) Compliance in the hindlegs and individual joints o f goats during extreme vertical jumping D.V. Lee, E. Yoo, A.A. Biewener. Concord Field Station, Harvard University,

Cambridge, MA, USA There is no question that animal's legs are spring-like during running but does the inverse relationship between leg length and leg force represent true compliance from physical springs? To address this question, we considered three jumping behaviors in goats: 1) a climbing jump up onto a 64 degree wall (C J1), a climbing jump from a 64 degree wall up onto a horizontal platform (C J2), and 2) a running jump up onto a box (BXJ). We predicted that physical springs, where present, would constrain joint mechanics and tested this by modeling the compliance of individual hindlimb joints and the whole hindleg during the stance phase of jumping. Across the three jumps, actuation ratio (i.e., 1 = pure actuation, 0 = pure compliance) of the whole leg closely mirrored that of the ankle joint, with lowest ratios in BXJ (0.51±0.015), intermediate in C J1 (0.65±0.018), and greatest in C J2 (0.97±0.015). So elasticity is exploited most in the running approach jump (BXJ) and least in the steep climbing jump (C J2). The ankle emerged as the principal joint spring in C J1 and BXJ but none of the joints show much potential for storage and return of elastic strain energy in C J2. Despite different jumping strategies and variable work requirements, the Achilles tendon spring is evidenced by the consistent spring constant of the ankle across the three jumps tested. The linear leg spring, however, differs significantly, having similar spring constants in C J1 and BXJ (4.2±0.58 and 4.0±0.50kN/m) but a much greater spring constant in C J2 (6.8±0.49 kN/m). This modulation of spring constant demonstrates that the leg as whole is not constrained absolutely by a physical spring. True compliance at the ankle paired with modified limb posture and joint actuation yields an effectively stiffer leg in steep climbing jumps. 6684 Mo-Tu, no. 13 (P67) Statistical shape modelling of long bones for biomechanical analyses '~H.M. Yang 1,2, A.M. Hill 1, A.M.J. Bull 1, D. Rueckert 2. 1Departments of

Bioengineering and 2 Computing, Imperial College London, UK Subject-specific preclinical surgical planning, intraoperative navigation, and musculoskeletal modelling require accurate definition of the shapes of bones. The most appropriate methods available require large imaging datasets and manual or semi-manual segmentation; these methods are not widely applicable. The aims of this work were to devise robust methods for the definition of the shapes of long bones using statistical shape modelling (SSM), and to test these on a dataset of humeri that demonstrate significant variability in shape. A set of 31 primate humeri were CT scanned and manually segmented. These primates encompassed all terrestial locomotor types. Point correspondences among members of this training set were established using a method that is built on the work of Frangi et al. [1]. The alignment of samples into the common coordinate system was obtained by scaling them into the same size followed by rigid registrations. Affine registration was found to produce significant errors; therefore, a bounding box scaling was applied to reduce complexity. The scaling factors were defined as the difference of the longest axis. Corresponding point sets were based on Multiresolution B-Splines free form deformation. The SSM was constructed using Principle Component Analysis. The free form deformation resulted in no discernible differences between bone shapes, demonstrating a high accuracy of the method. The first mode of variation accounted for 42% of the variation in bone shape. This single component discriminated directly between great apes (including humans) and monkeys. A locomotor similarity matrix was constructed that incorporated time spent in five modes of locomotion. Manters test was used to relate the locomotor similarity matrix to the principal components of variation of shape; this showed that principal components 2, 3, and 4 may be significantly related to locomotor type. This study demonstrates that SSM of bones can discriminate between bones that have different environmental influences that includes loading based on locomotor type. References [1] Frangi et al. IEEE Trans. Med. Imag. 2002; 21. 6618 Mo-Tu, no. 14 (P67) Prediction of ground reaction forces during quadrupedal animal locomotion using accelerometers and gyroscopes L. Ren, T. Pfau, K. Parsons, A. Wilson, J.R. Hutchinson. The Royal Veterinary

College, University of London, London, UK We developed a novel method to calculate the total three-dimensional ground reaction force (GRF) acting on animals during locomotion, based on 3D accelerometer and gyroscopic data. The method uses linear acceleration and rate of gyration data from multiple sensors to derive the total GRF, without