Application of the digital volume correlation technique for the measurement of displacement and strain fields in bone: A literature review

Digital volume correlation (DVC) provides experimental measurements of displacements and strains throughout the interior of porous materials such as trabecular bone. It can provide full-field continuum- and tissue-level measurements, desirable for validation of finite element models, by comparing image volumes from subsequent µCT scans of a sample in unloaded and loaded states.     

Comparison of patella bone strain between females with and without patellofemoral pain: A finite element analysis study

Elevated bone principal strain (an indicator of potential bone injury) resulting from reduced cartilage thickness has been suggested to contribute to patellofemoral symptoms. However, research linking patella bone strain, articular cartilage thickness, and patellofemoral pain (PFP) remains limited. The primary purpose was to determine whether females with PFP exhibit elevated patella bone strain when compared to pain-free controls. A secondary objective was to determine the influence of patella cartilage thickness on patella bone strain. Ten females with PFP and 10 gender, age, and activity-matched pain-free controls participated. Patella bone strain fields were quantified utilizing subject-specific finite element (FE) models of the patellofemoral joint (PFJ). Input parameters for the FE model included (1) PFJ geometry, (2) elastic moduli of the patella bone, (3) weight-bearing PFJ kinematics, and (4) quadriceps muscle forces. Using quasi-static simulations, peak and average minimum principal strains as well as peak and average maximum principal strains were quantified. Cartilage thickness was quantified by computing the perpendicular distance between opposing voxels defining the cartilage edges on axial plane magnetic resonance images. Compared to the pain-free controls, individuals with PFP exhibited increased peak and average minimum and maximum principal strain magnitudes in the patella. Additionally, patella cartilage thickness was negatively associated with peak minimum principal patella strain and peak maximum principal patella strain. The elevated bone strain magnitudes resulting from reduced cartilage thickness may contribute to patellofemoral symptoms and bone injury in persons with PFP.     

The static accuracy and calibration of inertial measurement units for 3D orientation

Inertial measurement units (IMUs) are integrated electronic devices that contain accelerometers, magnetometers and gyroscopes. Wearable motion capture systems based on IMUs have been advertised as alternatives to optical motion capture. In this paper, the accuracy of five different IMUs of the same type in measuring 3D orientation in static situations, as well as the calibration of the accelerometers and magnetometers within the IMUs, has been investigated. The maximum absolute static orientation error was 5.2°, higher than the 1° claimed by the vendor. If the IMUs are re-calibrated at the time of measurement with the re-calibration procedure described in this paper, it is possible to obtain an error of less than 1°, in agreement with the vendor's specifications (XSens Technologies B.V. 2005. Motion tracker technical documentation Mtx-B. Version 1.03. Available from: www.xsens.com).

The new calibration appears to be valid for at least 22 days providing the sensor is not exposed to high impacts. However, if several sensors are ‘daisy chained’ together changes to the magnetometer bias can cause heading errors of up to 15°. The results demonstrate the non-linear relationship between the vendor's orthogonality claim of < 0.1° and the accuracy of 3D orientation obtained from factory calibrated IMUs in static situations. The authors hypothesise that the high magnetic dip (64°) in our laboratory may have exacerbated the errors reported. For biomechanical research, small relative movements of a body segment from a calibrated position are likely to be more accurate than large scale global motion that may have an error of up to 9.8°.     

The static accuracy and calibration of inertial measurement units for 3D orientation

Inertial measurement units (IMUs) are integrated electronic devices that contain accelerometers, magnetometers and gyroscopes. Wearable motion capture systems based on IMUs have been advertised as alternatives to optical motion capture. In this paper, the accuracy of five different IMUs of the same type in measuring 3D orientation in static situations, as well as the calibration of the accelerometers and magnetometers within the IMUs, has been investigated. The maximum absolute static orientation error was 5.2 degrees , higher than the 1 degrees claimed by the vendor. If the IMUs are re-calibrated at the time of measurement with the re-calibration procedure described in this paper, it is possible to obtain an error of less than 1 degrees , in agreement with the vendor's specifications (XSens Technologies B.V. 2005. Motion tracker technical documentation Mtx-B. Version 1.03. Available from: www.xsens.com). The new calibration appears to be valid for at least 22 days providing the sensor is not exposed to high impacts. However, if several sensors are 'daisy chained' together changes to the magnetometer bias can cause heading errors of up to 15 degrees . The results demonstrate the non-linear relationship between the vendor's orthogonality claim of < 0.1 degrees and the accuracy of 3D orientation obtained from factory calibrated IMUs in static situations. The authors hypothesise that the high magnetic dip (64 degrees ) in our laboratory may have exacerbated the errors reported. For biomechanical research, small relative movements of a body segment from a calibrated position are likely to be more accurate than large scale global motion that may have an error of up to 9.8 degrees .     

A repeated sampling bone chamber methodology for the evaluation of tissue differentiation and bone adaptation around titanium implants under controlled mechanical conditions

A repeated sampling bone chamber methodology was developed for the study of the influence of the mechanical environment on skeletal tissue differentiation and bone adaptation around titanium implants. Via perforations, bone grows into the implanted outer bone chamber, containing an inner bone chamber with a central test implant. An actuator—easily mounted on the outer bone chamber—allows a controlled mechanical stimulation of the test implant. After each experiment, the inner bone chamber—with its content—can be harvested and analysed. A new inner bone chamber with a central implant can be inserted consecutively in the outer bone chamber and a new experiment can start. Pilot studies led to a reliable surgical protocol and showed the applicability of the methodology, offering the possibility to study skeletal tissue differentiation and adaptation around implants under well-controlled mechanical conditions, and this protected from external loading. Repeated sampling of the bone chamber allows conducting several experiments within the same animal at the same site, thereby excluding subject- and site-dependent variability and reducing the amount of experimental animals.     

Perinatal stem cells: A promising cell resource for tissue engineering of craniofacial bone

In facing the mounting clinical challenge and suboptimal techniques of craniofacial bone defects resulting from various conditions, such as congenital malformations, osteomyelitis, trauma and tumor resection, the ongoing research of regenerative medicine using stem cells and concurrent advancement in biotechnology have shifted the focus from surgical reconstruction to a novel stem cell-based tissue engineering strategy for customized and functional craniofacial bone regeneration. Given the unique ontogenetical and cell biological properties of perinatal stem cells, emerging evidence has suggested these extraembryonic tissue-derived stem cells to be a promising cell source for extensive use in regenerative medicine and tissue engineering. In this review, we summarize the current achievements and obstacles in stem cell-based craniofacial bone regeneration and subsequently we address the characteristics of various types of perinatal stem cells and their novel application in tissue engineering of craniofacial bone. We propose the promising feasibility and scope of perinatal stem cell-based craniofacial bone tissue engineering for future clinical application.     

A new method of fabricating robust freeform 3D ceramic scaffolds for bone tissue regeneration

Fabrication of three‐dimensional (3D) scaffolds with appropriate mechanical properties and desired architecture for promoting cell growth and new tissue formation is one of the most important efforts in tissue engineering field. Scaffolds fabricated from bioactive ceramic materials such as hydroxyapatite and tricalcium phosphate show promise because of their biological ability to support bone tissue regeneration. However, the use of ceramics as scaffold materials is limited because of their inherent brittleness and difficult processability. The aim of this study was to create robust ceramic scaffolds, which have a desired architecture. Such scaffolds were successfully fabricated by projection‐based microstereolithography, and dilatometric analysis was conducted to study the sintering behavior of the ceramic materials. The mechanical properties of the scaffolds were improved by infiltrating them with a polycaprolactone solution. The toughness and compressive strength of these ceramic/polymer scaffolds were about twice those of ceramic scaffolds. Furthermore, the osteogenic gene expression on ceramic/polymer scaffolds was better than that on ceramic scaffolds. Through this study, we overcame the limitations of previous research on fabricating ceramic scaffolds and these new robust ceramic scaffolds may provide a much improved 3D substrate for bone tissue regeneration. Biotechnol. Bioeng. 2013; 110: 1444–1455. © 2012 Wiley Periodicals, Inc.     

Review: Development of clinically relevant scaffolds for vascularised bone tissue engineering

Clinical translation of scaffold-based bone tissue engineering (BTE) therapy still faces many challenges despite intense investigations and advancement over the years. To address these clinical barriers, it is important to analyse the current technical challenges in constructing a clinically relevant scaffold and subsequent clinical issues relating to bone repair. This review highlights the key challenges hampering widespread clinical translation of scaffold-based vascularised BTE, with a focus on the repair of large non-union defects. The main limitations of current scaffolds include the lack of sufficient vascularisation, insufficient mechanical strength as well as issues relating to the osseointegration of the bioresorbable scaffold and bone infection management. Critical insights on the current trends of scaffold technologies and future directions for advancing next-generation BTE scaffolds into the clinical realm are discussed. Considerations concerning regulatory approval and the route towards commercialisation of the scaffolds for widespread clinical utility will also be introduced.     

Noninvasive measurement of aluminium in human bone: Preliminary human study and improved system performance

Aluminium has been measured in the hands of 18 referent subjects and six aluminium welders using the technique of in vivo neutron activation analysis. The minimal detection limit (MDL) in the human subjects was 28.0 μgAl/gCa, whereas it was 19.5 μgAl/gCa in calibration standards. On average the aluminium exposed subjects had higher levels of aluminium in their hands than did the referent subjects. However, this difference only just achieved significance at the 5% level and should be treated with caution, since the study had not been deliberately designed to assess this difference. Following the preliminary human study, improvements were made to the measurement system with respect to the gamma-ray detector array and to the timing sequence of irradiation-transfer-counting. These improvements were tested on the calibration standards, lowering the MDL from 19.5 μgAl/gCa to 8.32 μgAl/gCa. A similar improvement in human measurements would result in an in vivo MDL of 12.0 μgAl/gCa.     

A computational model for cell/ECM growth on 3D surfaces using the level set method: a bone tissue engineering case study

Three-dimensional open porous scaffolds are commonly used in tissue engineering (TE) applications to provide an initial template for cell attachment and subsequent cell growth and construct development. The macroscopic geometry of the scaffold is key in determining the kinetics of cell growth and thus in vitro ‘tissue’ formation. In this study, we developed a computational framework based on the level set methodology to predict curvature-dependent growth of the cell/extracellular matrix domain within TE constructs. Scaffolds with various geometries (hexagonal, square, triangular) and pore sizes (500 and 1,000  \(\upmu \) m) were produced in-house by additive manufacturing, seeded with human periosteum-derived cells and cultured under static conditions for 14 days. Using the projected tissue area as an output measure, the comparison between the experimental and the numerical results demonstrated a good qualitative and quantitative behavior of the framework. The model in its current form is able to provide important spatio-temporal information on final shape and speed of pore-filling of tissue-engineered constructs by cells and extracellular matrix during static culture.     

Investigating the spatial accuracy of CBCT-guided cranial radiosurgery: A phantom end-to-end test study

PurposeTo evaluate the spatial accuracy of a frameless cone-beam computed tomography (CBCT)-guided cranial radiosurgery (SRS) using an end-to-end (E2E) phantom test methodology.Methods and materialsFive clinical SRS plans were mapped to an acrylic phantom containing a radiochromic film. The resulting phantom-based plans (E2E plans) were delivered four times. The phantom was setup on the treatment table with intentional misalignments, and CBCT-imaging was used to align it prior to E2E plan delivery. Comparisons (global gamma analysis) of the planned and delivered dose to the film were performed using a commercial triple-channel film dosimetry software. The necessary distance-to-agreement to achieve a 95% (DTA95) gamma passing rate for a fixed 3% dose difference provided an estimate of the spatial accuracy of CBCT-guided SRS. Systematic (∑) and random (σ) error components, as well as 95% confidence levels were derived for the DTA95 metric.ResultsThe overall systematic spatial accuracy averaged over all tests was 1.4 mm (SD: 0.2 mm), with a corresponding 95% confidence level of 1.8 mm. The systematic (Σ) and random (σ) spatial components of the accuracy derived from the E2E tests were 0.2 mm and 0.8 mm, respectively.ConclusionsThe E2E methodology used in this study allowed an estimation of the spatial accuracy of our CBCT-guided SRS procedure. Subsequently, a PTV margin of 2.0 mm is currently used in our department.     

Matrix/mineral ratio and domain size variation with bone tissue age: A photothermal infrared study

Atomic force microscopy-infrared spectroscopy (AFM-IR) and optical photothermal infrared spectroscopy (O-PTIR), which feature spectroscopic imaging spatial resolution down to ～ 50 nm and ～ 500 nm, respectively, were employed to characterize the nano- to microscale chemical compositional changes in bone. Since these changes are known to be age dependent, fluorescently labelled bone samples were employed. The average matrix/mineral ratio values decrease as the bone tissue matures as measured by both AFM-IR and O-PTIR, which agrees with previously published FTIR and Raman spectroscopy results. IR ratio maps obtained by AFM-IR reveal variation in matrix/mineral ratio-generating micron-scale bands running parallel to the bone surface as well as smaller domains within these bands ranging from ～ 50 to 700 nm in size, which is consistent with the previously published length scale of nanomechanical heterogeneity. The matrix/mineral changes do not exhibit a smooth gradient with tissue age. Rather, the matrix/mineral transition occurs sharply within the length scale of 100–200 nm. O-PTIR also reveals matrix/mineral band domains running parallel to the bone surface, resulting in waves of matrix/mineral ratios progressing from the youngest to most mature tissue. Both AFM-IR and O-PTIR show a greater variation in matrix/mineral ratio value for younger tissue as compared to older tissue. Together, this data confirms O-PTIR and AFM-IR as techniques that visualize bulk spectroscopic data consistent with higher-order imaging techniques such as Raman and FTIR, while revealing novel insight into how mineralization patterns vary as bone tissue ages.     

Preparation and characterization of cockle shell aragonite nanocomposite porous 3D scaffolds for bone repair

The demands for applicable tissue-engineered scaffolds that can be used to repair load-bearing segmental bone defects (SBDs) is vital and in increasing demand. In this study, seven different combinations of 3 dimensional (3D) novel nanocomposite porous structured scaffolds were fabricated to rebuild SBDs using an extraordinary blend of cockle shells (CaCo₃) nanoparticles (CCN), gelatin, dextran and dextrin to structure an ideal bone scaffold with adequate degradation rate using the Freeze Drying Method (FDM) and labeled as 5211, 5400, 6211, 6300, 7101, 7200 and 8100. The micron sized cockle shells powder obtained (75 µm) was made into nanoparticles using mechano-chemical, top-down method of nanoparticles synthesis with the presence of the surfactant BS-12 (dodecyl dimethyl bataine). The phase purity and crystallographic structures, the chemical functionality and the thermal characterization of the scaffolds’ powder were recognized using X-Ray Diffractometer (XRD), Fourier transform infrared (FTIR) spectrophotometer and Differential Scanning Calorimetry (DSC) respectively. Characterizations of the scaffolds were assessed by Scanning Electron Microscopy (SEM), Degradation Manner, Water Absorption Test, Swelling Test, Mechanical Test and Porosity Test. Top-down method produced cockle shell nanoparticles having averagely range 37.8±3–55.2±9 nm in size, which were determined using Transmission Electron Microscope (TEM). A mainly aragonite form of calcium carbonate was identified in both XRD and FTIR for all scaffolds, while the melting (Tm) and transition (Tg) temperatures were identified using DSC with the range of Tm 62.4–75.5 °C and of Tg 230.6–232.5 °C. The newly prepared scaffolds were with the following characteristics: (i) good biocompatibility and biodegradability, (ii) appropriate surface chemistry and (iii) highly porous, with interconnected pore network. Engineering analyses showed that scaffold 5211 possessed 3D interconnected homogenous porous structure with a porosity of about 49%, pore sizes ranging from 8.97 to 337 µm, mechanical strength 20.3 MPa, Young's Modulus 271±63 MPa and enzymatic degradation rate 22.7 within 14 days.     

The effect of strain rate on the failure stress and toughness of bone of different mineral densities

The risk of low energy fracture of the bone increases with age and osteoporosis. This paper investigates the effect of strain rate and mineral level on the peak stress and toughness of whole ovine bones.     

Maxillary expansion treatment using bone anchors: development and validation of a 3D finite element model

Objective: Develop a finite element (FE) model of a skull to perform biomechanical studies of maxillary expansion using bone anchors (BA).

Materials and methods: A skull model was developed and assigned material properties based on Hounsfield unit (HU) values of cone-beam computerized tomography (CBCT) images. A 3 mm diameter cylindrical BA was modelled and inserted in the palatal bone. A 4 mm transverse displacement was applied on the anchor. An evaluation on the effect on local stresses of BA implantation inclination angle was performed.

Results: Proper displacement results and strain–stress trends for the expansion process were present. Stress distribution patterns were similar as reported in the literature. No significant difference between BA inclination angles was found.

Conclusion: This work leads to a better understanding and prediction of craniofacial and maxillary bone remodelling during ME with BA treatments and is a first step towards the development of patient specific treatments.     

Long-term study of bone remodelling after femoral stem: a comparison between dexa and finite element simulation

A hip replacement with a cemented or cementless femoral stem produces an effect on the bone called adaptive remodelling, attributable to mechanical and biological factors. The objective of all of cementless prostheses designs has been to achieve a perfect transfer of loads in order to avoid stress-shielding, which produces an osteopenia. In order to quantify this, the long term and mass-produced study with dual energy X-ray absorptiometry (DEXA) is necessary. Finite element (FE) simulation makes possible the explanation of the biomechanical changes which are produced in the femur after stem implantation. The good correlation obtained between the results of the FE simulation and the densitometric study allow, on one hand, to explain from the point of view of biomechanical performance the changes observed in bone density in the long-term, where it is clear that these are due to a different transfer of load in the implanted model compared to the healthy femur; on the other hand, it validates the simulation model, in a way that it can be used in different conditions and at different time periods, to carry out a sufficiently precise prediction of the evolution of the bone density from the biomechanical behaviour in the interaction between the prosthesis and femur.     

Advances in 3D printing of composite scaffolds for the repairment of bone tissue associated defects

The conventional methods of using autografts and allografts for repairing defects in bone, the osteochondral bone, and the cartilage tissue have many disadvantages, like donor site morbidity and shortage of donors. Moreover, only 30% of the implanted grafts are shown to be successful in treating the defects. Hence, exploring alternative techniques such as tissue engineering to treat bone tissue associated defects is promising as it eliminates the above-mentioned limitations. To enhance the mechanical and biological properties of the tissue engineered product, it is essential to fabricate the scaffold used in tissue engineering by the combination of various biomaterials. Three-dimensional (3D) printing, with its ability to print composite materials and with complex geometry seems to have a huge potential in scaffold fabrication technique for engineering bone associated tissues. This review summarizes the recent applications and future perspectives of 3D printing technologies in the fabrication of composite scaffolds used in bone, osteochondral, and cartilage tissue engineering. Key developments in the field of 3D printing technologies involves the incorporation of various biomaterials and cells in printing composite scaffolds mimicking physiologically relevant complex geometry and gradient porosity. Much recently, the emerging trend of printing smart scaffolds which can respond to external stimulus such as temperature, pH and magnetic field, known as 4D printing is gaining immense popularity and can be considered as the future of 3D printing applications in the field of tissue engineering.     

Validation of a dual energy X-ray absorptiometer: measurement of bone mass and soft tissue composition

We investigated the reproducibility of total and regional body composition measurements performed on a dual energy X-ray absorptiometer (DXA). A group of 38 women aged 21–81 (mean 52. 4) years was scanned twice with repositioning to determine intra-observer reproducibility of measurements of bone mineral density (BMD, g · cm⁻²), bone mineral content (BMC, g), lean mass (LM, kg) and fat mass (FM, kg) of the total body and of the major subregions of the body. In addition, the ability of the DXA machine to detect changes in LM and FM (simulated by placing 11.1 and 22.3 kg porcine lard on the body of 11 subjects) was examined. Coefficients of variations calculated from the root mean square averages of individual standard deviations were as follows (BMD, BMC, FM, LM): 1.4%, 1.1%, 1.4%, 1.7% (total body), 2.2%, 2.1%,-,- (head), 2.8%, 2.8%, 2.0%, 2.2% (trunk), 3.6%, 3.9%, 4.0%, 4.9% (arms), 2.7%, 1.3%, 2.6%, 2.8% (legs). Percentage fat (%fat) of exogenous lard was 81.3 (SD 3.5)% as assessed by the absorptiometer which corresponded well with the result of chemical analysis (82.8%). Estimated %fat of exogenous lard was not influenced by initial body mass or percentage body fat. Percentages of expected mean values with 11.1 kg lard placed on the body were 99.9 (SD 0.3) for body mass, 100.5 (SD 2.1) for LM, and 99.5 (SD 3.5) for FM. BMD was overestimated by 3.2% (P < 0.005) with 11.1 kg lard on the body. BMD as well as BMC increased significantly with 22.3␣kg lard on the body (P < 0.005). The results showed that BMD, BMC, LM, and FM of the total body were precisely estimated by the DXA machine used. Regional measurements were less precise. Changes in total body soft tissue composition were precisely and accurately estimated. The lard placed on the body falsely affected BMD and BMC measurements. Changes in body mass could have a similar effect. Accepted: 6 January 1997