A new dynamic pressure transducer

175

Abstracts

THE ORTHOGONAL MATERIAL PROPERTIES OF TRABECULAR BONE: CORRELATION WITH COMPUTED TOlMOGRAPHY DENSiTY MEASURE.MENTS

M. CIARELLI,J. PETERSON, B. MACINTOSH, J. L. Ku, L. S. MA-~-~HEWS and S. A. GOLDSTEIN (The Biomechanics, Trauma and Sports Medicine Laboratory, Section of Orthopaedic Surgery and the Bioengineering Program, The University of Michigan, Ann Arbor, MI 48109, U.S.A.) The distribution of the mechanical properties of trabecular bone from the proximal and distal femur. proximal humerus, distal radius, vertebral bodies and iliac crest was investigated. Computed tomographic density, orthogonal material properties, apparent density and ash weight were analyzed as a function of metaphyseal and anatomic locations. The relationship between orthogonal material properties and density was found to be statistically significant as noted by previous investigators. The study also indicates that quantitative CT scanning can be utilized to establish the mechanical properties of trabecular bone.

E. MEASUREMENT

A PORTABLE

IN-SHOE

PRESSURE

MONITOR

M. R. LEVIN, K. M. REINECK,J. HESSELINKand C. L. VAUGHAN(Departments of Electrical and Biomedical Engineering, University of Cape Town, South Africa) The assessment of lower extremity function can be greatly enhanced by the measurement of the mechanical environment at the foot/shoe interface. This was recognized a century ago by Marey, and more recently has been the focus of various groups in the U.S.A. and elsewhere. The purpose of our study was to develop an in-shoe pressure monitor to overcome some of the problems associated with previous systems. Our monitor has the following components: a thin insole (3 mm, 170g) with eight pressure transducers; a patient backpack consisting of a memory, sensor circuitry, video generator and RF transmitter; a microcomputer, a video mixer, TV monitor and video cassette recorder. We believe that our in-shoe pressure monitor has a number of features-low cost, instant data display, portability, simple operation, RF transmission range of 1 km, thin insole-that enhance its potential as a clinical assessment tool. At present it is being used to study normal subjects and patients with running injuries.

A NEW DYNAMIC

PRESSURE

TRANSDUCER

J. HAUGHTON,K. DRAKE, D. BYLSKI,L. S. MAI-~HEWSand S. A. GOLDSTEIN (The Biomechanics, Trauma and Sports Medicine Laboratory, Section of Orthopaedic Surgery and the Bioengineering Program, The University of Michigan, Ann Arbor, MI 48109, U.S.A.) A new thin film piezoelectric transducer material has been evaluated for use as a dynamic pressure sensor. The polyvinylidene fluoride polymer is manufactured in thicknesses of 9-100 jr and its surfaces can be metalized to produce any array of sensors using printed circuit techniques. Experimentally the transducers were found to be linear, reproducible, rate insensitive and easily insulated from moisture. They are particularly useful for measuring the pressure distribution between conforming surfaces such as in joint articulations.

A METHOD

FOR MEASURING

SURFACE

STRAINS FRO,M INDIVIDUAL

TRABECULAE

J. L. Ku, S. A. GOLDSTEIN, D. AXELRODand L. S. MATTHEWS(The Biomechanics, Trauma and Sports Medicine Laboratory, Section of Orthopedic Surgery and the Bioengineering Program, The University of Michigan, Ann Arbor, MI 48109, U.S.A.) The purpose of this work was to devise a method by which to investigate optimization schemes and test hypotheses of trabecular bone remodeling. Surface trabeculae from extracted bone cubes which have remodeled to controlled load histories, are marked with a grid of parallelograms by laser bleached fluorescence. The cube is