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Patterns of strain in the macaque ulna during functional activity
B Demes1, J T Stern, M R Hausman
1Department of Anatomical Sciences, School of Medicine, State University of New York, Stony Brook 11794-8081, USA. bdemes@mail.som.sunysb.edu
American Journal of Physical Anthropology
|May 20, 1998
Summary
Experiments on rhesus macaque ulnae reveal mediolateral bending, not anteroposterior bending, as the primary loading during locomotion. Bone strain analysis challenges conventional interpretations of long bone geometry.
Area of Science:
- Biomechanics
- Primate Anatomy
- Skeletal Physiology
Background:
- Understanding bone deformation during locomotion is crucial for interpreting skeletal structure and function.
- Previous assumptions suggested anteroposterior bending in primate ulnae during locomotion.
Purpose of the Study:
- To investigate the in vivo bone strain and loading environment of the rhesus macaque ulna during locomotion.
- To test the hypothesis of anteroposterior bending in the ulna during limb movement.
Main Methods:
- In vivo bone strain measurements using rosette strain gauges on the ulnae of three female rhesus macaques.
- Recording strains during walking and galloping gaits.
- Calculation of principal strains and their directions relative to the bone's long axis.
Main Results:
- Mediolateral bending, not anteroposterior bending, was identified as the predominant loading regime in the macaque ulna.
- Tensile strains were observed on the lateral cortex, while compressive strains predominated on the medial cortex during walking stance phase.
- The neutral axis of bending ran from anterior-medial to posterior-lateral, with superimposed torsion.
- Strain magnitudes were at the lower end of those recorded for nonprimate mammals.
Conclusions:
- The rhesus macaque ulna primarily undergoes mediolateral bending during locomotion, contrary to the anteroposterior bending hypothesis.
- Ground reaction forces passing medial to the forearm likely cause this bending.
- The ulna's lack of reinforcement in the plane of bending and the counterintuitive bending direction necessitate caution in interpreting long bone cross-sectional geometry.