Sex differences in workload in medieval Poland: Patterns of asymmetry and biomechanical adaptation in the upper limb at Giecz.

OBJECTIVES: This study characterizes sexual dimorphism in skeletal markers of upper limb mechanical loading due to lateralization as evidence of division of labor in medieval Giecz, Poland. METHODS: Twenty-six dimensions for paired humeri, clavicles, and radii representing adult males (n = 89) and females (n = 53) were collected from a skeletal sample from the cemetery site Gz4. Percent directional asymmetry (DA) and absolute asymmetry (AA) for each dimension were compared among bones, osteometric subcategories, and sex. Additionally, side bias and sex differences were assessed in degenerative joint disease (DJD) and entheseal changes (ECs). RESULTS: Nearly all measurements revealed significant asymmetry favoring the right side. Asymmetry was most pronounced in midshaft dimensions with few sex differences. There were more correlations among dimensions within elements than between elements, mainly in the midshaft. No laterality in DJD frequencies was noted for either sex, but females demonstrated significantly lower odds of having DJD than males in most joints. Most ECs demonstrated a right-bias and association with DA with no sex-specific patterns except the biceps brachii insertion, where females were ~5 times more likely to be scored "right" than males. DISCUSSION: The general lack of sex differences in asymmetry and ECs suggests similarly demanding workloads for females and males, with the exception of sex-specific functional loading differences in the forearm. Further, DJD data suggest males engaged in more intensive activities involving the upper limb. These results enhance understanding of workload in this important historical period and provide a comparison for asymmetry in past populations.

Analysis of injury mechanism and thoracic response of elderly, small female PMHS in near-side impact scenarios.

OBJECTIVE: In 2020, 17% of all crash fatalities were individuals aged 65 years or older. Crash data also revealed that for older occupants, thoracic related injuries are among the leading causes of fatality. Historically, the majority of near-side impact postmortem human subjects (PMHS) studies used a generic load wall to capture external loads that were applied to PMHS. While these data were helpful in documenting biofidelity, they did not represent a realistic response an occupant would undergo in a near-side crash. The objective of this research was to test small, elderly female PMHS in a repeatable, realistic near-side impact crash scenario to investigate current injury criteria as they relate to this vulnerable population. METHOD: Ten small, elderly PMHS were subjected to a realistic near-side impact loading condition. The PMHS were targeted to be elderly females age 60+, approximately 5th percentile in height and weight, with osteopenic areal bone mineral density. Each subject was seated on a mass-production seat, equipped with a side airbag and standard three-point restraint with a pretensioner. Other boundary conditions included an intruding driver's side door. PMHS instrumentation included strain gages on ribs 3-10 bilaterally to identify fracture timing. Two chestbands were used to measure chest deflection, one at the level of the axilla and one at the level of the xiphoid process. RESULTS: Injuries observed included rib fractures, particularly on the struck side, and in multiple cases a flail chest was observed. Eight of ten subjects resulted in AIS3+ thoracic injuries, despite previously tested ATDs predicting less than a 10% chance of AIS3+ injury. Subjects crossed the threshold for AIS3 injury in the range of only 1% - 9% chest compression. Additionally, mechanisms of injury varied, as some injuries were incurred by door interactions while others came during airbag interactions. CONCLUSIONS: This research points to two areas of concern that likely require further analysis: (1) the appropriateness of potentially oversimplified PMHS testing to establish injury thresholds and define injury criteria for complicated crash scenarios; (2) the importance of identifying the precise timing of injuries to better understand the effect of current passive restraint systems.

Thoracic responses and injuries to male postmortem human subjects (PMHS) in rear-facing seat configurations in high-speed frontal impacts.

Objective: One potential nonstandard seating configuration for vehicles with automated driving systems (ADS) is a reclined seat that is rear-facing when in a frontal collision. There are limited biomechanical response and injury data for this seating configuration during high-speed collisions. The main objective of this study was to investigate thoracic biomechanical responses and injuries to male postmortem human subjects (PMHS) in a rear-facing scenario with varying boundary conditions.Method: Fourteen rear-facing male PMHS tests (10 previously published and 4 newly tested) were conducted at two different recline angles (25-degree and 45-degree) in 56 km/h frontal impacts. PMHS were seated in two different seats; one used a Fixed D-Ring (FDR) seat belt assembly and one used an All Belts To Seat (ABTS) restraint. For thoracic instrumentation, strain gages were attached to ribs to quantify strain and fracture timing. A chestband was installed at the mid-sternum level to quantify anterior-posterior (AP) chest deflections. Data from the thorax instrumentation were analyzed to investigate injury mechanisms.Results: The PMHS sustained a greater number of rib fractures (NRF) in the 45-degree recline condition (12 ± 7 NRF for ABTS45 and 25 ± 18 NRF for FDR45) than the 25-degree condition (6 ± 4 NRF for ABTS25 and 12 ± 8 NRF for FDR25), despite AP chest compressions in the 45-degree condition (-23.7 ± 9.4 mm for ABTS45 and -39.6 ± 11.9 mm for FDR45) being smaller than the 25-degree condition (-38.9 ± 16.9 mm for ABTS25 and -55.0 ± 4.4 mm for FDR25). The rib fractures from the ABTS condition were not as symmetric as the FDR condition in the 25-degree recline angle due to a belt retractor structure located at one side of the seatback frame. Average peak AP chest compression occurred at 45.7 ± 3.4 ms for ABTS45, 45.6 ± 3.1 ms for FDR45, 46.7 ± 1.9 ms for ABTS25, and 46.9 ± 2.3 ms for FDR25. Average peak seatback resultant force occurred at 43.9 ± 0.9 ms for ABTS45, 44.6 ± 0.8 ms for FDR45, 42.5 ± 0.2 ms for ABTS25, and 41.5 ± 0.5 ms for FDR25. The majority of rib fractures occurred after peak AP chest compression and peak seatback resultant force likely due to the ramping motion of the PMHS, which might create a combined loading (e.g., AP deflection and upward deflection) to the thorax. Although NRF in the 45-degree reclined condition was greater than the 25-degree recline condition, similar magnitudes of rib strains were observed regardless of seat and restraint types, while strain modes varied.Conclusions: The majority of rib fractures occurred after peak AP chest compression and peak seatback force, especially in FDR25, ABTS45, and FDR45, while the PMHS ramped up along the seatback. AP chest compression, seatback load, and strain measured along the rib could not explain the greater NRF in the 45-degree recline conditions. A complex combination of AP chest deflection with upward deflection was discovered as a possible mechanism for rib fractures in PMHS subjected to rear-facing frontal impacts in this study.

Effects of loading rate, age, and morphology on the material properties of human rib trabecular bone.

The material and morphometric properties of trabecular bone have been studied extensively in bones bearing significant weight, such as the appendicular long bones and spine. Less attention has been devoted to the ribs, where quantification of material properties is vital to understanding thoracic injury. The objective of this study was to quantify the compressive material properties of human rib trabecular bone and assess the effects of loading rate, age, and morphology on the material properties. Material properties were quantified via uniaxial compression tests performed on trabecular bone samples at two loading rates: 0.005 s-1 and 0.5 s-1. Morphometric parameters of each sample were quantified before testing using micro-computed tomography. Rib trabecular bone material properties were lower on average compared to trabecular bone from other anatomical locations. Morphometric parameters indicated an anisotropic structure with low connectivity and a sparser density of trabeculae in the rib compared to other locations. No significant differences in material properties were observed between the tested loading rates. Material properties were only significantly correlated with age at the 0.005 s-1 loading rate, and no morphometric parameter was significantly correlated with age. Trabecular separation and thickness were most strongly correlated with the material properties, indicating the sparser trabecular matrix likely contributed to the lower material property values compared to other sites. The novel trabecular bone material properties reported in this study can be used to improve the thoracic response and injury prediction of computational models.

Differential Cortical Volumetric Bone Mineral Density within the Human Rib.

INTRODUCTION: The human rib provides a vital role in the protection of thoracic contents. Rib fractures are linked to injuries and health complications that can be fatal. Current clinical methods to assess fracture risk and bone quality are insufficient to quantify intra-element differences in bone mineral density (BMD) or to identify at-risk populations. Utilizing quantitative computed tomography (QCT) provides accurate measures of volumetric BMD (vBMD) along the length of the rib which can help delineate factors influencing differential fracture risk. METHODOLOGY: One mid-level rib was obtained from 54 post-mortem human subjects (PMHS) and scanned using QCT. Volumes of interest (VOIs) were created for sites at 30%, 50%, and 75% of rib total curve length. Mean Hounsfield units (HU) from each VOI were converted to vBMD using a scan-specific cortical phantom calibration curve. Additionally, rib and lumbar areal BMD (aBMD) were obtained from a sub-sample of 33 PMHS. RESULTS: Significant differences in vBMD were found between all sites within the rib (p<0.01). When analyzed by sex, vBMD between the 30% and 50% site were no longer different in either males or females (p>0.05). Separating the sample into discrete age groups demonstrated the relative differences in vBMD between sites diminished with age. Further, age as a continuous variable significantly predicted rib vBMD at all sites (p<0.05), but with little practical or clinical utility (R2, 14.7- 22.8%). Similarly, only small amounts of variation in rib vBMD were explained from DXA lumbar and rib aBMD (R2 , 1.1-21.8%). CONCLUSIONS: vBMD significantly decreased from the posterior (30%) site to the anterior (75%) site within the rib which may represent adaptation to localized mechanical loading. These differences could result in differential fracture risk across the rib. As thoracic injury can be fatal, using comprehensive assessments of bone quality that accounts for variation within the rib may provide more accurate identification of at-risk populations.

Comparison of small female PMHS thoracic responses to scaled response corridors in a frontal hub impact.

OBJECTIVE: The purpose of this study was to generate biomechanical response corridors of the small female thorax during a frontal hub impact and evaluate scaled corridors that have been used to assess biofidelity of small female anthropomorphic test devices (ATDs) and human body models (HBMs). METHODS: Three small female postmortem human subjects (PMHS) were tested under identical conditions, in which the thorax was impacted using a 14.0 kg pneumatic impactor at an impact velocity of 4.3 m/s. Impact forces to PMHS thoraces were measured using a load cell installed behind a circular impactor face with a 15.2 cm diameter. Thoracic deflections were quantified using a chestband positioned at mid-sternum. Strain gages installed on the ribs and sternum identified fracture timing. Biomechanical response corridors (force-deflection) were generated and compared to scaled small female thoracic corridors using a traditional scaling method (TSM) and rib response-based scaling method (RRSM). A BioRank System Score (BRSS) was used to quantify differences between the small female PMHS data and both scaled corridors. RESULTS: Coefficients of variation from the three small female PMHS responses were less than 2% for peak force and 7% for peak deflection. Overall, the scaled corridor means determined from the TSM and RRSM were less than two standard deviations away from the mean small female PMHS corridors (BRSS < 2.0). The RRSM resulted in smaller deviation (BRSS = 1.1) from the PMHS corridors than the TSM (BRSS = 1.7), suggesting the RRSM is an appropriate scaling method. CONCLUSIONS: New small female PMHS force-deflection data are provided in this study. Scaled corridors from the TSM, which have been used to optimize current safety tools, were comparable to the small female PMHS corridors. The RRSM, which has the great benefit of using rib structural properties instead of requiring whole PMHS data, resulted in better agreement with the small female PMHS data than the TSM and deserves further investigation to identify scaling factors for other population demographics.

Factors affecting the numerical response and fracture location of the GHBMC M50 rib in dynamic anterior-posterior loading.

Rib fractures are common traumatic injuries, with links to increased morbidity and mortality. Finite element ribs from human body models have struggled to predict the force-displacement response, force and displacement at fracture, and the fracture location for isolated rib tests. In the current study, the sensitivity of a human body model rib with updated anisotropic and asymmetric material models to changes in boundary conditions, material properties, and geometry was investigated systematically to quantify contributions to response. The updated material models using uncalibrated average material properties from literature improved the force-displacement response of the model, whereas the cross-sectional geometry was the only parameter to effect fracture location. The resulting uncalibrated model with improved material models and cross-sectional geometry closely predicted experimental average force-displacement response and fracture location.

Development of a Strain-Based Model to Predict Eviscerated Thoracic Response From Dynamic Individual Rib Tests.

The objective of this study was to develop an analytical model using strain-force relationships from individual rib and eviscerated thorax impacts to predict bony thoracic response. Experimental eviscerated thorax forces were assumed to have two distinct responses: an initial inertial response and subsequently, the main response. A second-order mass-spring-damper model was used to characterize the initial inertial response of eviscerated thorax force using impactor kinematics. For the main response, equivalent strains in rib levels 4-7 were mapped at each time point and a strain-based summed force model was constructed using individual rib tests and the same ribs in the eviscerated thorax test. A piecewise approach was developed to join the two components of the curve and solve for mass, damping, stiffness parameters in the initial response, transition point, and scale factor of the strain-based summed force model. The final piecewise model was compared to the overall experimental eviscerated thorax forces for each postmortem human subjects (PMHS) (n = 5) and resulted in R2 values of 0.87-0.96. A bootstrapping approach was utilized to validate the model. Final model predictions for the validation subjects were compared with the corridors constructed for the eviscerated thorax tests. Biofidelity ranking system score (BRSS) values were approximately 0.71 indicating that this approach can predict eviscerated responses within one standard deviation from the mean response. This model can be expanded to other tissue states by quantifying soft tissue and visceral contributions, therefore successfully establishing a link between individual rib tests and whole thoracic response.

A comparison of rib cortical bone compressive and tensile material properties: Trends with age, sex, and loading rate.

The objectives of this study were to develop novel methods for quantifying human rib cortical bone material properties in compression and to compare the compressive material property data to existing tensile data for matched subjects. Cylindrical coupons were obtained from the rib cortical bone of 30 subjects (M = 19, F = 11) ranging from 18 to 95 years of age (Avg. = 48.5 ± 24.3). Two coupons were obtained from each subject. One coupon was tested in compression at 0.005 strain/s, while the other coupon was tested in compression at 0.5 strain/s. Load and displacement data were recorded so that the elastic modulus, yield stress, yield strain, ultimate stress, ultimate strain, elastic strain energy density (SED), plastic SED, and total SED could be calculated. All compressive material properties were significantly different between the two loading rates. An ANOVA revealed that sex alone had no significant effect on the compressive material properties. The interaction between sex and age was significant for some material properties, but this may have been a consequence of the lack of older females in the subject pool. None of the compressive material properties were significantly correlated with age, but were more correlated with sample density. This finding differed for the tensile material properties, which showed stronger correlations with age. When comparing between tension and compression, significant differences were observed for all material properties except for the total SED, once the effects of loading rate and age had been accounted for. This was the first study to quantify the material properties of human rib cortical bone in compression. The results of this study demonstrated that rib and thorax finite element models should consider the effects of loading rate, loading mode, and age when incorporating material properties published in the literature.

Subject-specific rib finite element models with material data derived from coupon tests under bending loading.

Rib fractures are common thoracic injuries in motor vehicle crashes. Several human finite element (FE) human models have been created to numerically assess thoracic injury risks. However, the accurate prediction of rib biomechanical response has shown to be challenging due to human variation and modeling approaches. The main objective of this study was to better understand the role of modeling approaches on the biomechanical response of human ribs in anterior-posterior bending. Since the development of subject specific rib models is a time-consuming process, the second objective of this study was to develop an accurate morphing approach to quickly generate high quality subject specific rib meshes. The exterior geometries and cortical-trabecular boundaries of five human 6th-level ribs were extracted from CT-images. One rib mesh was developed in a parametric fashion and the other four ribs were developed with an in-house morphing algorithm. The morphing algorithm automatically defined landmarks on both the periosteal and endosteal boundaries of the cortical layer, which were used to morph the template nodes to target geometries. Three different cortical bone material models were defined based on the stress-strain data obtained from subject-specific tensile coupon tests for each rib. Full rib anterior-posterior bending tests were simulated based on data recorded in testing. The results showed similar trends to test data with some sensitivity relative to the material modeling approach. Additionally, the FE models were substantially more resistant to failure, highlighting the need for better techniques to model rib fracture. Overall, the results of this work can be used to improve the biofidelity of human rib finite element models.

Biomechanical Response Targets of Adult Human Ribs in Frontal Impacts.

Thorax injuries mainly due to rib fractures have been associated with high rates of morbidity and mortality in motor vehicle crashes. Thoracic biomechanics has been studied extensively, but there are no robust biomechanical response targets for ribs that consider age, sex, body size, and vulnerability factors. The objective of this study was to generate biomechanical targets for human rib response with respect to age, sex, and body size. Two-hundred sixty-one ribs from 171 individuals were dynamically loaded to failure in anterior-posterior bending. Force and displacement at the time of fracture in young adults were greater than in older adults (p < 0.0001). Sex differences were found in those over 40 years old (p < 0.0001). Fracture force from 5th percentile female ribs was lower than 50th and 95th male (p < 0.005). Vulnerable ribs were successfully identified by examining the percentile of both force and displacement at the time of fracture in the proposed samples. The biomechanical targets generated in this study will have useful applications to computational thorax and rib models to aid in injury prevention measures.

Rib Variation at Multiple Locations and Implications for Histological Age Estimation.

Existing histological age estimation methods using the rib were developed mainly from the midshaft; however, in forensic practice, uncertainty of sampling location often arises due to fragmented or previously sampled ribs. The potential for error increases when sampling location is uncertain and utilizing a section beyond the midshaft (either anterior or posterior) may result in erroneous age estimates. Additionally, there is debate within the field regarding the minimum number of sections needed for accurate age estimation. The aim of this research is to determine the importance of the midshaft distinction for age-at-death assessment and the necessity of analyzing serial sections by evaluating histological variables at sampling locations along the length of the rib. Three seriated histological sections at three sampling locations (anterior, midshaft, and posterior) were obtained from sixth ribs of ten postmortem human subjects. Cortical area (Ct.Ar) and osteon population density (OPD) were collected from each section (n = 90). Significant differences were determined in Ct.Ar between sampling locations, demonstrating the variation present along the length of the rib. A comparison of OPD at sampling locations revealed significant differences, suggesting that sampling site is critical to accurate age estimates. When sampling location is uncertain, a more anterior section should be taken. Analysis of serial sections within locations revealed no significant differences in OPD or Ct.Ar, supporting the practice of collecting data from one section for age estimation. While an age estimate can be achieved through the analysis of one section, best practice suggests reading two sections to capture intraindividual variation.

Comparing FE human body model rib geometry to population data.

Finite element human body models (HBMs) are used to assess injury risk in a variety of impact scenarios. The ribs are a key structural component within the chest, so their accuracy within HBMs is vitally important for modeling human biomechanics. We assessed the geometric correspondence between the ribs defined within five widely used HBMs and measures drawn from population-wide studies of rib geometry, focusing on (1) rib global shape, (2) rib cross-sectional size and shape, and (3) rib cortical bone thickness. A parametric global shape model fitted to all HBM ribs was compared to expected rib parameters calculated for each HBM's subject demographic using population reference data. The GHBMC M50 and THUMS M50 male HBMs showed 24% and 50% of their fitted rib shape parameters (6 parameters per each 12 ribs) falling outside 1SD from population expected values, respectively. For female models the GHBMC F05, THUMS F05, and VIVA F50 models had 21%, 26%, and 19% of their rib shape parameters falling outside 1SD, respectively. Cross-sectional areas and inertial moments obtained along the HBM ribs were compared to average ± 1SD corridors for male and female ribs drawn from reference population data. The GHBMC M50, THUMS M50, and VIVA F50 model ribs were all larger in overall cross-sectional area than their targeted average population values by 0.9SDs (average across the rib's full length), 1.7SDs, and 1.3SDs, respectfully. When considering cortical bone cross-sectional area, the THUMS and VIVA models-which each define a constant bone thickness value across the entire rib-overestimated bone content on average by 1.1SDs and 1.2SDs, respectively. HBMs have traditionally performed poorly when predicting rib fracture onset or fracture site, and in all HBMs in this study the rib regions with the most extreme cortical bone thickness and cross-sectional area discrepancies (compared to average reference data) corresponded to regions toward the sternal end of the ribs where rib fractures most frequently occur. Results from this study highlight geometrical components of current HBM ribs that differ from the rib geometry that would be expected from within those models' target demographics, and help researchers prioritize improvements to their biofidelity.

Radiographic timelines for pediatric healing fractures: a systematic review.

Skeletal fractures, a common injury in physically abused children, often go undetected and untreated for significant lengths of time and are sometimes incidentally discovered radiographically. Our objective was to review current literature for scientific studies of pediatric fracture healing with associated timelines. We conducted a search of Embase, EBSCOhost, MEDLINE (PubMed), and Web of Science for literature published from the earliest available up to August 2018. We evaluated the included articles for quality, with consideration for use in clinical and forensic settings. Of a total of 313 full-text articles evaluated, 10 met study inclusion criteria. The patient age range among studies was 0-17 years, with children younger than 1 year included in the majority of studies. The fracture locations included in studies were primarily fractures of the upper limb and pectoral girdle, followed by fractures of the lower limb. The radiographic features of healing varied greatly among the studies. Timelines of common fracture healing variables differed significantly among studies. Scientific, radiographic studies of pediatric fracture healing are limited. Gaps in knowledge regarding fracture healing highlight the need for future research and validation studies. Fracture healing timelines derived from existing timelines should be used with caution.

Biomechanical Responses and Injury Assessment of Post Mortem Human Subjects in Various Rear-facing Seating Configurations.

The objective of this study was to generate biomechanical corridors from post-mortem human subjects (PMHS) in two different seatback recline angles in 56 km/h sled tests simulating a rear-facing occupant during a frontal vehicle impact. PMHS were placed in a production seat which included an integrated seat belt. To achieve a repeatable configuration, the seat was rigidized in the rearward direction using a reinforcing frame that allowed for adjustability in both seatback recline angle and head restraint position. The frame contained instrumentation to measure occupant loads applied to the head restraint and seatback. To measure PMHS kinematics, the head, spine, pelvis, and lower extremities were instrumented with accelerometers and angular rate sensors. Strain gages were attached to anterior and posterior aspects of the ribs, as well as the mid-shaft of the femora and tibiae, to determine fracture timing. A chestband was installed at the mid sternum to quantify chest deformation. Biomechanical corridors for each body and seat location were generated for each recline angle to provide data for quantitatively evaluating the biofidelity of ATDs and HBMs. Injuries included upper extremity injuries, rib fractures, pelvis fractures, and lower extremity injuries. More injuries were documented in the 45-degree recline case than in the 25-degree recline case. These injuries are likely due to the excessive ramping up and corresponding kinematics of the PMHS. Biomechanical corridors and injury information presented in this study could guide the design of HBMs and ATDs in rigid, reclined, rear-facing seating configurations during a high-speed frontal impact.

Effects of sex, age, and two loading rates on the tensile material properties of human rib cortical bone.

The objective of this study was to evaluate the effects of sex, loading rate, and age on the tensile material properties of human rib cortical bone over a wide range of subject demographics. Sixty-one (n = 61) subjects (M = 32, F = 29) ranging in age from 17 to 99 years of age (Avg. = 56.4 ±â€¯26.2 yrs) were used in this study. Two rectangular coupons of cutaneous rib cortical bone were obtained from each subject and milled into dog-bone coupons for testing. For each subject, one coupon was tested to failure in tension on a material testing system at a targeted strain rate of 0.005 strain/s, while the other coupon was tested at 0.5 strain/s. A reaction load cell was used to measure axial load, and an extensometer was used to measure displacement within the gage length of the coupon. Data were obtained from fifty-eight (n = 58) subjects at 0.005 strain/s and fifty-eight (n = 58) subjects at 0.5 strain/s, with fifty-five (n = 55) matched pairs. The elastic modulus, yield stress, yield strain, failure stress, failure strain, ultimate stress, elastic strain energy density (SED), plastic SED, and total SED were then calculated for each test. There were no significant differences in material properties between sexes and no significant interactions between age and sex. In regard to the differences in material properties with respect to loading rate, yield stress, yield strain, failure stress, ultimate stress, elastic SED, plastic SED, and total SED were significantly lower at 0.005 strain/s compared to 0.5 strain/s. Spearman correlation analyses showed that all material properties had significant negative correlations with age at 0.005 strain/s except modulus. At 0.5 strain/s, all material properties except yield strain had significant negative correlations with age. Although the results revealed that the material properties of human rib cortical bone varied significantly with respect to chronological age, the R2 values only ranged from 0.15 to 0.62, indicating that there may be other underlying variables that better account for the variance within a given population. This is the first study to analyze the effects of sex, loading rate, and age on tensile material properties of human rib cortical bone using a reasonably large sample size. Overall, the results of this study provide data that will allow FEMs to better model and assess differences in the material response of the rib cage for nearly all vehicle occupants of driving age.

Microdamage as a Bone Quality Component: Practical Guidelines for the Two-Dimensional Analysis of Linear Microcracks in Human Cortical Bone.

Microdamage is a component of bone quality believed to play an integral role in bone health. However, comparability between existing studies is fraught with issues due to highly variable methods of sample preparation and poorly defined quantification criteria. To address these issues, this article has two aims. First, detailed methods for preparation and analysis of linear microcracks in human ribs, specifically addressing troubleshooting issues cited in previous studies, are laid out. Second, new, partially validated criteria are proposed in an effort to reduce subjective differences in microcrack counts and measures, ensuring more comparable results between studies. Revised definitions based on current literature in conjunction with a digital atlas to reduce observer inaccuracy and bias are presented. The goal is to provide a practical methodology for bone biologists and biomechanists to collect and analyze linear microcracks for basic science research. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Regional maps of rib cortical bone thickness and cross-sectional geometry.

Here we present detailed regional bone thickness and cross-sectional measurements from full adult ribs using high resolution CT scans processed with a cortical bone mapping technique. Sixth ribs from 33 subjects ranging from 24 to 99 years of age were used to produce average cortical bone thickness maps and to provide average ± 1SD corridors for expected cross-section properties (cross-sectional areas and inertial moments) as a function of rib length. Results obtained from CT data were validated at specific rib locations using direct measurements from cut sections. Individual thickness measurements from CT had an accuracy (mean error) and precision (SD error) of -0.013 ± 0.167 mm (R2 coefficient of determination of 0.84). CT-based measurement errors for rib cross-sectional geometry were -0.1 ± 13.1% (cortical bone cross-sectional area) and 4.7 ± 1.8% (total cross-sectional area). Rib cortical bone thickness maps show the expected regional variation across a typical rib's surface. The local mid-rib maxima in cortical thickness along the pleural rib aspect ranged from range 0.9 to 2.6 mm across the study population with an average map maximum of 1.4 mm. Along the cutaneous aspect, rib cortical bone thickness ranged from 0.7 to 1.9 mm with an average map thickness of 0.9 mm. Average cross-sectional properties show a steady reduction in total cortical bone area from 10% along the rib's length through to the sternal end, whereas overall cross-sectional area remains relatively constant along the majority of the rib's length before rising steeply towards the sternal end. On average, male ribs contained more cortical bone within a given cross-section than was seen for female ribs. Importantly, however, this difference was driven by male ribs having larger overall cross-sectional areas, rather than by sex differences in the bone thickness observed at specific local cortex sites. The cortical bone thickness results here can be used directly to improve the accuracy of current human body and rib models. Furthermore, the measurement corridors obtained from adult subjects across a wide age range can be used to validate future measurements from more widely available image sources such as clinical CT where gold standard reference measures (e.g. such as direct measurements obtained from cut sections) are otherwise unobtainable.

The use of ROI overlays and a semi-automated method for measuring cortical area in ImageJ for histological analysis.

A major part of histologic studies is the use of high resolution imaging for data collection and analysis. ImageJ, a freely available software from the NIH designed for image analysis, has many features that are not well-known among bone histologists and can be incredibly beneficial in terms of stream-lining data collection and maximizing limited resources. The aims of this technical note are twofold: (a) to describe methods for image annotation and measurement using region of interest overlays in ImageJ, and (b) to present a new code for a semi-automated method of measuring cortical bone areas from high resolution cross-sectional images also using ImageJ.