The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Complications in Cross-Species Comparisons of Joint Kinematics: An Example from the Primate Foot

THOMAS M. GREINER.

Department of Health Professions, University of Wisconsin-La Crosse

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Kinematic analyses are often complicated by the casual creation of the reference planes used to describe the orientation of joint rotational axes. The human “anatomical position” is most often chosen as the standard referent. However, the identification of the anatomical position becomes complicated when it is based upon skeletal landmarks. Skeletal landmarks are subject to individual variation and the basis of their variation rarely coincides with the biology of joint mechanics. Therefore, comparisons of joint kinematics are confounded by variations in the reference frame. Complications are magnified when the comparisons are made between species, each of which may have different skeletal growth trajectories and natural postures that diverge from the human based standard. This presentation will illustrate this problem by comparing the orientations of rotational axes for intrinsic foot joints of three different primates.

Data are derived from a kinematic investigation of cadaveric feet in six humans, five chimpanzees and six baboons. The orientations of the rotational axes for selected joints are then described using different reference frame constructions. Comparisons show that there is higher variation, both within and between species, when reference frames are constructed from skeletal landmarks. Undue emphasis on skeletal landmarks may therefore complicate posited interpretations of cross species biomechanical functions. These results suggest that some interpretations of the evolution of biomechanical functions may be similarly misguided.

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