Fabric-elasticity relationships of tibial trabecular bone are similar in osteogenesis imperfecta and healthy individuals

A simple projection method to correlate the principal mechanical direction with the principal microstructural direction of human osteoporotic femoral heads

The mechanics of the trabecular bone is related to its structure; this work aimed to propose a simple projection method to clarify the correlation between the principal mechanical direction (PMD) and the principal microstructural direction (PMSD) of trabecular bones from osteoporotic femoral heads. A total of 529 trabecular cubes were cropped from five osteoporotic femoral heads. The micro computed tomography (μCT) sequential images of each cube were first projected onto the three Cartesian coordinate planes to have three overlapped images, and the trabecular orientation distribution in the three images was analyzed. The PMSD corresponding to the greatest distribution frequency of the trabecular orientation in the three images was defined. Then, the voxel finite element (FE) models of the cubes were reconstructed and simulated to obtain their compliance matrices, and the matrices were subjected to transversal rotation to find their maximum elastic constants. The PMD corresponding to the maximum elastic constant was defined. Subsequently, the correlation of the defined PMSD and PMD was analyzed. The results showed that PMSD and PMD of the trabecular cubes did not show a significant difference at the xy- and yz-planes except that at the zx-plane. Despite this, the mean PMSD-PMD deviations at the three coordinate planes were close to 0°, and the PMSD-PMD fitting to the line PMSD = PMD demonstrated their high correlation. This study might be helpful to identify the loading direction of anisotropic trabecular bones in experiments by examining the PMSD and also to guide bone scaffold design for bone tissue repair.

Surgical treatment of osteogenesis imperfecta: a summary of the incidence of femoral implant-related complications in children with Sillence type I, III and IV

PURPOSE

This study explored the incidence of IRCs used in the procedures of the femur in children with osteogenesis imperfecta (OI) and investigated the independent risk factors of IRCs.

METHODS

Three hundred eight-eight cases of surgical data about children with OI were included, who were treated with plate, elastic nail, Kirschner wire and telescopic rod. The choice of different procedures depended on the age of children, the status of femur and the availability of devices. Patient demographics and major IRCs were recorded to compare the outcomes of the four procedures. Then, Cox proportional hazard regression was used to analyse the independent risk factors of IRC, and subgroup analysis was applied to further verify the above results.

RESULTS

The total incidence of IRC in the four groups was 90.1% (191/212) for plate, 96.8% (30/31) for Kirschner wire, 87.7% (57/65) for elastic nail and 30.0% (24/80) for telescopic rod. The incidence of IRC in the telescopic rod was lower than that in plate, elastic nail and Kirschner wire (P < 0.001). Cox proportional hazard regression analysis confirmed that procedure was the independent risk factor of IRC (HR, 0.191; 95% CI, 0.126-0.288; P < 0.001), fracture (HR, 0.193; 95% CI, 0.109-0.344; P < 0.001) and deformity (HR, 0.086; 95% CI, 0.027-0.272; P < 0.001). In addition, age of surgery was the independent risk factor of fracture (HR, 0.916; 95% CI, 0.882-0.952; P < 0.001) and deformity (HR, 1.052; 95% CI, 1.008-1.098; P = 0.019). Subgroup analysis confirmed that age of surgery, gender, classification, preoperative state and angle did not affect the effect of telescopic rod on reducing the risk of IRCs.

CONCLUSIONS

In our cohort, lower incidence of IRCs was observed in telescopic rod group compared with plate, Kirschner wire and elastic nail. Procedure and age of surgery were independent risk factors of fracture. Likewise, procedure and age of surgery were independent risk factors of deformity, and procedure was independent risk factors of IRC.

Bone microarchitecture and strength assessment in adults with osteogenesis imperfecta using HR-pQCT: normative comparison and challenges

Data on bone microarchitecture in osteogenesis imperfecta (OI) are scarce. The aim of this cross-sectional study was to assess bone microarchitecture and strength in a large cohort of adults with OI using high-resolution peripheral quantitative computed tomography (HR-pQCT) and to evaluate challenges of using HR-pQCT in this cohort. Second-generation HR-pQCT scans were obtained at the distal radius and tibia in 118 men and women with Sillence OI type I, III, or IV using an extremity-length-dependent scan protocol. In total, 102 radius and 105 tibia scans of sufficient quality could be obtained, of which 11 radius scans (11%) and 14 tibia scans (13%) had a deviated axial scan angle as compared with axial angle data of 13 young women. In the scans without a deviated axial angle and compared with normative HR-pQCT data, Z-scores at the radius for trabecular bone mineral density (BMD), number, and separation were -1.6 ± 1.3, -2.5 ± 1.4, and -2.7 (IQR: 2.7), respectively. They were -1.4 ± 1.5 and -1.1 ± 1.2 for stiffness and failure load and between ±1 for trabecular thickness and cortical bone parameters. Z-scores were significantly lower for total and trabecular BMD, stiffness, failure load, and cortical area and thickness at the tibia. Additionally, local microarchitectural inhomogeneities were observed, most pronounced being trabecular void volumes. In the scans with a deviated axial angle, the proportion of Z-scores <-4 or >4 was significantly higher for trabecular BMD and separation (radius) or most total and trabecular bone parameters (tibia). To conclude, especially trabecular bone microarchitecture and bone strength were impaired in adults with OI. HR-pQCT may be used without challenges in most adults with OI, but approximately 12% of the scans may have a deviated axial angle in OI due to bone deformities or scan positioning limitations. Furthermore, standard HR-pQCT parameters may not always be reliable due to microarchitectural inhomogeneities nor fully reflect all inhomogeneities.

Tensile Mechanical Properties of Dry Cortical Bone Extracellular Matrix: A Comparison Among Two Osteogenesis Imperfecta and One Healthy Control Iliac Crest Biopsies

Osteogenesis imperfecta (OI) is a genetic, collagen-related bone disease that increases the incidence of bone fractures. Still, the origin of this brittle mechanical behavior remains unclear. The extracellular matrix (ECM) of OI bone exhibits a higher degree of bone mineralization (DBM), whereas compressive mechanical properties at the ECM level do not appear to be inferior to healthy bone. However, it is unknown if collagen defects alter ECM tensile properties. This study aims to quantify the tensile properties of healthy and OI bone ECM. In three transiliac biopsies (healthy n = 1, OI type I n = 1, OI type III n = 1), 23 microtensile specimens (gauge dimensions 10 × 5 × 2 μm3) were manufactured and loaded quasi-statically under tension in vacuum condition. The resulting loading modulus and ultimate strength were extracted. Interestingly, tensile properties in OI bone ECM were not inferior compared to controls. All specimens revealed a brittle failure behavior. Fracture surfaces were graded according to their mineralized collagen fibers (MCF) orientation into axial, mixed, and transversal fracture surface types (FST). Furthermore, tissue mineral density (TMD) of the biopsy cortices was extracted from micro-computed tomogra[hy (μCT) images. Both FST and TMD are significant factors to predict loading modulus and ultimate strength with an adjusted R 2 of 0.556 (p = 2.65e-05) and 0.46 (p = 2.2e-04), respectively. The influence of MCF orientation and DBM on the mechanical properties of the neighboring ECM was further verified with quantitative polarized Raman spectroscopy (qPRS) and site-matched nanoindentation. MCF orientation and DBM were extracted from the qPRS spectrum, and a second mechanical model was developed to predict the indentation modulus with MCF orientation and DBM (R 2 = 67.4%, p = 7.73e-07). The tensile mechanical properties of the cortical bone ECM of two OI iliac crest biopsies are not lower than the one from a healthy and are primarily dependent on MCF orientation and DBM. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Recommendations for High-resolution Peripheral Quantitative Computed Tomography Assessment of Bone Density, Microarchitecture, and Strength in Pediatric Populations

PURPOSE OF REVIEW

The purpose of this review is to summarize current approaches and provide recommendations for imaging bone in pediatric populations using high-resolution peripheral quantitative computed tomography (HR-pQCT).

RECENT FINDINGS

Imaging the growing skeleton is challenging and HR-pQCT protocols are not standardized across centers. Adopting a single-imaging protocol for all studies is unrealistic; thus, we present three established protocols for HR-pQCT imaging in children and adolescents and share advantages and disadvantages of each. Limiting protocol variation will enhance the uniformity of results and increase our ability to compare study results between different research groups. We outline special cases along with tips and tricks for acquiring and processing scans to minimize motion artifacts and account for growing bone. The recommendations in this review are intended to help researchers perform HR-pQCT imaging in pediatric populations and extend our collective knowledge of bone structure, architecture, and strength during the growing years.