Do stress distributions explain patterns of growth in sea urchins?: A finite element analysis

ABSTRACTS OF THE ELEVENTH ANNUAL MEETING OF THE AMERICAN SOCIETY OF BIOMECHANICS Held in Davis, California,

16-18 September,

Edited by Thomas

1987

D. Brown

At the Eleventh Annual Meeting of the American Society of Biomechanics, 66 oral and 33 poster presentations were delivered. There were fourteen slide sessions, three keynote lectures. the Fourth Annual Borelli Award presentation, and two poster sessions. The podium session topics were: (1) Skeletal Development and Functional Adaptation; (2) Kinematic/Kinetic Analysis of the Extremities; (3) Cardiovascular Biomechanics; (4) OrthoticsiProsthetics/ Equipment; (5) hluscle-Endurance, Force Distribution and Modeling Requirements; (6) Locomotion; (7) Mechanical/Morphological Correlations of Bone Properties; (5) Exercise and Sports Science; (9) Load Transmission Through Natural and Reconstructed Articular Joints; (10) Mechanical Processes in Cells and Small Organisms: ( I I) Mechanical Properties and Stress Analyses of Bone; (13) Getting Along in the Water; (13) Orthopacdic Problems of the Spine; and (14) Mcasuremcnt Instrumentation.

SESSION 1. SKELETAL

I_!~rr:srd Per

.J.

tiaran.

Lteoartment

DEVELOPMENT ADAPTATION

Lonlogy,

at

Unl

AND FUNCTIONAL

ver-51

ty

of

Cal

itornia.

Le 1ev . CA 94YYt.! Cea urc:~lns ~Echlnodermata.

Ech~noidea) are marine creatures ha.:lnq an internal CaZO2 skeleton with the general appearance of a orolate soherold. lhe lsossible relationshlp between the distribution nf stresses and the pattern af growth over the skeletons of sea ttrch~nr- has been an ob lect of aoeculation for at least X) years. Here the results c*f a cornouter generated finite element analssls of the sea urcn~n slcleton al-e used to analyze the effects of shape and material cgf stresses cfver the skeleton. oi-~pe~-tv differences an ';he
1butlon

of

I he resrtl ts t !attened wd’,e

forces

to

s,tres:_ges

fur ther

ever

suqoest

grounded- forms 81-e

f iattei

.tha:~

skeleton

the

whv. with

for

1)~ general. arorrth.

those

and

1r-1 protected

a sea

why

given

loadinq

regime.

urchins change from sea urchins exposed to areas.

THE ROLE OF MECHANICAL STRESS AND GEOMETRY IN THE PATTERN OF OSSIFICATION OF THE STERNUM Marcy \Vong and Dennis R. Carter Design Division, Department of .\lechanical Engineering Stanford University, StanIord, California, 91305. L’SA The role of mechanical loading and geometry in the endochondral ossification of the human sternum is explored using 2-D, plane stress finite element models. The loading history on the sternum by the rib bones is characterized by an assumed pressure distribution along the fourteen facets of costal cartilage. Based on the theory that cyclic octahedral shear stresses promote rndochondral ossification and cyclic dilatational stresses inhibit ossification, an osteogenic index is calculated which identifies areas of accelerated ossification within the sternum. These areas of increased osteogenic stimulus in the sternum model correctly predict the patterns of ossification By varying the geometry of the model, we were able to centers in developing human sterna. duplicate the three standard ossification patterns identified by Ashley (1956). The results of this study support the contention that mechanical loading histories play a fundamental role in skeletal morphogenesis and more generally in chondro-osseous biology. 887