Non-invasive (pQCT) biomechanical analysis of the whole human tibia in normal men and women.

SARA FELDMAN; RICARDO FRANCISCO CAPOZZA; PABLO ANDRÉS MORTARINO; IVAN YELIN; PAOLA REINA; HANS SCHIESSL; JOERN RITTWEGER; JOSÉ LUIS FERRETTI; GUSTAVO ROBERTO COINTRY

Denver (CO)

Congreso; XXXI ANNUAL MEETING, American Society for Bone & Mineral Research (ASBMR); 2009

Non-Invasive (pQCT) Biomechanical Analysis of the Whole Human Tibia In Normal Men and Women Authors: S. Feldman, R. Capozza, P. Mortarino, I. Yelin, P. Reina, H. Schiessl, J. Rittweger, J. Ferretti,G. CointryS. Feldman, R. Capozza, P. Mortarino, I. Yelin, P. Reina, H. Schiessl, J. Rittweger, J. Ferretti,G. Cointry Calf muscles induce a changing stress pattern along the tibia (uniaxial compression close to the heel, combined compression/torsion/bending toward the knee). This study analyzes pQCT scans taken at 5% intervals of the bone length (S5-S95 sites from heel to knee) in normal men and women (10/10) aged 20-40yr. Indicators of bone mass (cortical area, CtA; cortical & total BMC, ToC, CtC), diaphyseal design (peri/endosteal perimeters, PeriC, EndoC; cortical thickness, CtTh; circularity; bending & torsion moments of inertia, MI), and material quality (cortical vBMD, vCtD) were determined. Longitudinal patterns of variation of indicators were similar between genders, but male values were higher excepting vCtD. Expression of data as percentages of the minimal values for each indicator eliminated those differences. CtA and CtC increased from S5 to S45; were stable until S75, and fell more proximally. CtTh varied directly with CtA and CtC in S5-S45, then it decayed until S95. PeriC decreased from the heel to a minimum at S25-S55 and increased to a maximum toward the knee. MIs were minimal at S5-S25 and increased toward the knee. Up to S45, MIs grew directly with CtC, CtA or CtTh. From S50 to S80 they grew inversely to these indicators and directly with PeriC. CtC contributed to MIs only at S25-S45. From S55 to S70 MIs increased while ToC stabilized, and in S75-S90 they increased while CtC decreased. MIs(y) were related positively with CtC (distribution/mass curves) and negatively with vCtD (distribution/quality curves), with higher intercepts for men than women. ToC decayed 33% from S5 to S15 (where minimal ToC values and variance and maximal circularity were observed) and increased until S45, reaching the original S5 value at S40. It remained stable in S50-S80 and increased more proximally. The gender-related differences reflect allometric relationships. However, both distribution/mass and distribution/quality curves show that men distribute more efficiently their available cortical mass than women, in inverse association with tissue stiffness (vCtD). Minimal amount/variance of mass and MIs and largest circularity at S15 suggest a compression pattern at that level. Increasing MIs and decreasing circularity toward the knee indicate the progressive addition of bending and torsion stresses derived from calf muscle forces. Structural adaptations include increases in CtTh up to midshaft and in PeriC upwards. Results are in general agreement with the mechanostat Theory.