Structural analysis of the human tibia by tomographic (pQCT) serial scans

Abstract

This study analyses the evaluation of tomographic indicators of tibia structure, assuming that the usual loading pattern shifts from uniaxial compression close to the heel to a combined compression, torsion and bending scheme towards the knee. To this end, pQCT scans were obtained at 5% intervals of the tibia length (S5-S95 sites from heel to knee) in healthy men and women (10 ⁄ 10) aged 20-40 years. Indicators of bone mass [cortical area, cortical ⁄ total bone mineral content (BMC)], diaphyseal design (peri ⁄ endosteal perimeters, cortical thickness, circularity, bending ⁄ torsion moments of inertia -CSMIs), and material quality [(cortical vBMD (bone mineral density)] were determined. The longitudinal patterns of variation of these measures were similar between genders, but male values were always higher except for cortical vBMD. Expression of BMC data as percentages of the minimal values obtained along the bone eliminated those differences. The correlative variations in cortical area, BMC and thickness, periosteal perimeter and CSMIs along the bone showed that cortical bone mass was predominantly associated with cortical thickness toward the mid-diaphysis, and with bone diameter and CSMIs moving more proximally. Positive relationships between CSMIs (y) and total BMC (x) showed men's values shifting to the upper-right region of the graph and women's values shifting to the lower-left region. Total BMC decayed about 33% from S5 to S15 (where minimum total BMC and CSMI values and variances and maximum circularity were observed) and increased until S45, reaching the original S5 value at S40. The observed gender-related differences reflected the natural allometric relationships. However, the data also suggested that men distribute their available cortical mass more efficiently than women. The minimum amount and variance of mass indicators and CSMIs, and the largest circularity observed at S15 reflected the assumed adaptation to compression pattern at that level. The increase in CSMIs (successively for torsion, A-P bending, and lateral bending), the decrease in circularity values and the changes in cortical thickness and periosteal perimeter toward the knee described the progressive adaptation to increasing torsion and bending stresses. In agreement with the biomechanical background, the described relationships: (i) identify the sites at which some changes in tibial stresses and diaphyseal structure take place, possibly associated with fracture incidence; (ii) allow prediction of mass indicators at any site from single determinations; (iii) establish the proportionality between the total bone mass at regions with highly predominant trabecular and cortical bone of the same individual, suitable for a specific evaluation of changes in trabecular mass; and (iv) evaluate the ability of bone tissue to self-distribute the available cortical bone according to specific stress patterns, avoiding many anthropometric and gender-derived influences.

Increased density and periosteal expansion of the tibia in young adult men following short-term arduous training

“…This site is subject to predominantly compressive forces as indicated by its maximum circularity and lowest cortical thicknesses along the tibial diaphysis [30]. The difference in trabecular number and thickness of the ultra distal tibia between athletes of different sports [42] also suggests a possible contribution of trabecular microarchitecture to compressive bone strength with mechanical loading, which we could not directly assess using pQCT (due to its in-planar resolution of 0.4 mm).…”

“…The high trabecular content and larger cross sectional area at the distal site (4% of endplate) [30] is designed to resist high axial compressive forces resulting from impact, internal muscle forces, and to some extent posterior shear force generated throughout most of stance [31]. The primary forces experienced along the diaphysis result from the bending and torsional loads of eccentric muscle action and impact with the ground, resisted by its tubular structure and thicker outer cortical shell [30].…”

The Use of Allograft Bone Morphogenetic Protein in Foot and Ankle Arthrodesis

“…During the 2000s, the improved power and definition of scanners led to the multiplication of studies on this subject [1,[6][7][8][9][10][11][12].…”

“…The tibia consists of several parts (epiphyses-metaphyses-diaphysis) and each must bear a series of forces. It is commonly accepted that each part of the tibia cannot resist all forces, and so resistance is distributed differently in each part [1]. The epiphyseal and metaphyseal part (corresponding to S5-S15 and S80-S95) is subjected to compression forces.…”

“…The ratios between the mass and the resistance of each bone differ. They depend on the site and on the forces exerted [1]. In order to resist compression forces, highly mineralized bone (pre-eminently cancellous) is developed at the expense of cortical bone.…”