Original articleCorrelation of bone mineral density with strength and microstructural parameters of cortical bone in vitro
Introduction
Cortical bone contributes significantly to the mechanical strength of bone.1, 5, 24 The assessment of cortical bone strength might therefore be considered to be relevant for the prediction of fracture risk or the choice of suitable therapy strategies in orthopedic surgery. Several approaches for the prediction of cortical bone strength have been described, most of them using cortical bone mineral density (BMD) or measures of cortical geometry.2, 16 However, low correlation coefficients have been reported often between cortical bone strength and BMD.23, 26
The relationship between intracortical porosity and cortical bone strength has been examined frequently. Strong correlations have been reported and power regression models have been established between these parameters.3, 8, 10, 17, 20, 31 Intracortical porosity has been determined by histomorphometric analysis, an established standard procedure for the analysis of microstructure of cortical bone.
In addition to porosity, other microstructural parameters are considered to be of importance for the mechanical strength of cortical bone. Typical changes in cortical bone associated with advancing age are a decrease in osteonal area, an increase in haversian canal area, and an increasing number of osteons per unit area.6, 9, 11, 13, 14, 18, 19
The aim of our study was to evaluate the predictive value of BMD measured by quantitative computed tomography (QCT) for the microstructure determined by histological sections as well as for the mechanical strength of cortical bone. Histomorphometric parameters used for the description of the osseous microstructure included porosity, dimensions of porous structures, and osteon dimensions.
Section snippets
Extraction of bone biopsies
Cortical bone biopsies from the lateral diaphysis of 23 patients (15 women and 9 men, aged 56–88 years; mean 69.1 years) undergoing surgery for total hip replacement were evaluated. The reason for surgery in all cases was moderate osteoarthritis of the hip joint with normal configuration of the femoral diaphysis in the X-ray. The bone status was screened by using the Singh index, a semiquantitative classification of osteoporosis due to the visible rarefication of trabecular structures into six
Results
The value ranges for yield stress and elastic modulus of the cortical bone specimens and their BMD are presented in Table 1. The results for the dimensions of porous structures of 23 specimens are shown in Table 2, and in Table 3 the dimensions of parameters related to osteon dimensions are presented.
Our results indicate significant positive correlations between BMD and both mechanical parameters (Figure 3 , Table 4). Significant correlations between most structural parameters, assessed by
Discussion
The relevance of BMD measured by quantitative computed tomography for the mechanical properties of cortical bone has been controversial, because low correlation coefficients have been reported between cortical bone strength and BMD.23, 26 However, the relevance of BMD at the tissue level for the prediction of mechanical parameters of bone has also been reported previously for cancellous bone.29 Our data reveal significant correlations between BMD and both mechanical parameters (Table 4). For
References (31)
- et al.
Assessment of bone mineral at appendicular sites in females with fractures of the proximal femur
Bone
(1998) - et al.
Regional differences in cortical porosity in the fractured femoral neck
Bone
(1999) - et al.
Age- and sex-related changes in iliac cortical bone mass and remodeling
Bone
(1993) The effect of porosity and mineral content on the Young’s modulus of elasticity of compact bone
J Biomech
(1988)- et al.
Cortical mineral content of the radius assessed by peripheral QCT predicts compressive strength on biomechanical testing
Bone
(1995) - et al.
The relative effects of collagen fiber orientation, porosity, density, and mineralization on bone strength
J Biomech
(1989) - et al.
Stiffness of compact boneEffects of porosity and density
J Biomech
(1988) - et al.
Holding power of the 4.5 mm AO/ASIF cortex screw in cortical bone in relation to bone mineral
Injury
(1993) - et al.
Basic biomechanical measurements of boneA tutorial
Bone
(1993) - et al.
Predictive value of bone mineral density and morphology determined by peripheral quantitative computed tomography for cancellous bone strength of the proximal femur
Bone
(2001)