Three-dimensional morphometric properties of rod- and plate-like trabeculae in adolescent cancellous bone

Abstract

Background/objective: Despite many researches have been carried out on the three-dimensional microarchitecture of cancellous bone, the morphometric properties of rod and plate trabeculae in adolescent cancellous bone have not yet been investigated. This study aimed to investigate three-dimensional morphometric properties of rod- and plate-like trabeculae in normal adolescent cancellous bone, and to compare them with adult cancellous bones to reveal morphometric changes from adolescence to adult life to obtain more insight into the subchondral bone adaptations during development and growth.

Methods: This study included 23 normal human proximal tibiae. These tibiae were divided into three groups: adolescents (9-17 years, n = 6), young adults (18-24 years, n = 9), and adults (25-30 years, n = 8). From each tibia, six cubic cancellous bone samples (dimensions 8 × 8 × 8 mm³) were sawed from each medial and lateral condyle, yielding a total of 276 samples. These samples were scanned using micro computed tomography leading to three-dimensional cubic voxel sizes of 10.5 × 10.5 × 10.5 μm³. The morphometric parameters of individual rod- and plate-like trabeculae were calculated and compared among three age groups.

Results: Significant differences in some morphometric parameters were revealed. The mean longitudinal length of rods was significantly greater in the adolescents than in the young adults. Plate volume density showed an increasing trend with age, although not significant. Trabeculae were more plate-like in adolescents in the medial condyle of adolescents than in the lateral condyle, and changed towards more plate-like trabeculae in the adults. The single best predictor for the mechanical properties was apparent density. Apparent density alone explained 59% variations in Young's modulus, 77% in ultimate stress and 34% in failure energy, respectively (all p < 0.01). Morphometric parameters might improve this prediction.

Conclusion: In conclusion, this study has reported for the first time the morphometric parameters of rod- and plate-like trabeculae in adolescent proximal tibial cancellous bone, which will improve our understanding of morphometric changes in individual trabeculae during development and growth. Furthermore, separate analysis of individual rods and plates may also help reveal disease-related morphometric changes beyond bone mineral density.

The translational potential of this article: A thorough quantification of individual trabeculae during development and growth may help understand disease-related 3-D morphometric changes beyond bone mineral density.

Keywords: Adolescence; Microarchitectural properties; Trabecular plate; Trabecular rod; Volumetric spatial decomposition.

Figure 1

Study design. Cancellous bone samples were obtained beneath the thin layer of the subchondral plate and above the growth plate by using plastic template, which was available in different scales . Four cubic specimens with dimensions of 8 × 8 × 8 mm³ were sawed out, two from each medial and lateral condyles of each 23 human normal proximal tibia. Three-dimensional reconstruction of cancellous bone is displayed at the right side of lower corner, and volumetric spatial decomposition of trabeculae is illustrated at the middle and left sides of lower panel. Orientations of the sample are indicated. To investigate possible differences, the samples were divided into three groups: adolescents (9–17 years), young adults (18–24 years) and adults (25–30 years). These samples were scanned using micro-CT, and volumetric spatial decomposition was performed to quantify rod- and plate-like trabeculae and related properties. Stepwise multiple linear regressions were performed to determine the best predictor for mechanical properties as dependent variables, and all measured global microarchitectural properties, local morphometric properties and physical and compositional properties as independent (explanatory) variables. Regression analyses were further performed to determine the best predictor for mechanical properties independent of bone mineral density. AP = anterior–posterior; CC = cephalocaudal; CT = computed tomography; ML = medial–lateral.

Figure 2

Three-dimensional reconstructions of micro-CT images for selected samples with different ages. Differences in the microarchitecture are illustrated in the panel (A), volumetric spatial decomposition of trabeculae is shown in the panel (B), with further focus on the three-dimensional reconstruction of 10 slices in the panel (C). Orientations of the sample are indicated. AP = anterior–posterior; CC = cephalocaudal; CT = computed tomography; ML = medial–lateral.