Rib cortical bone thickness variation in adults by age and sex

Abstract

Rib fractures are a common and serious outcome of blunt thoracic trauma and their likelihood is greater in older individuals. Osteoporotic bone loss is a well-documented aging phenomenon with sex-specific characteristics, but within rib bones, neither baseline maps of regional thickness nor the rates of bone thinning with age have been quantified across whole ribs. This study presents such data from 4014 ribs of 240 adult subjects aged 20-90. A validated cortical bone mapping technique was applied to clinical computed tomography scans to obtain local rib cortical bone thickness measurements over the surfaces of ribs 2 through 11. Regression models to age and sex gave rates of cortex thinning in local zones and aggregated across whole ribs. The statistical parametric mapping provided these relationships regionally as a function of rib surface location. All models showed significant reductions in bone thickness with age (p < 0.01). Average whole-rib thinning occurred at between 0.011 to 0.032 mm/ decade (males) and 0.035 to 0.043 mm/decade (females), with sex and age accounting for up to 37% of population variability (R 2 ). Rates of thinning differed regionally and by rib, with the highest bone loss of up to 0.074 mm/decade occurring in mid-rib cutaneous and superior regions of ribs 2-6. Rates were consistently higher in females than males (significantly so across whole ribs but not all local regions) and were more pronounced in cutaneous, superior, and inferior rib aspects (average 0.025 mm/decade difference in ribs 4-8) compared to pleural aspects which had the thickest cortices but saw only minor differences in thinning rates by sex (0.045 mm/decade for females and 0.040 mm/decade for males). Regional analysis showed male and female bone thickness differences that were not statistically significant at 20 years of age (p > 0.05 across practically all regions) but subsequent cortex thinning meant that substantial pleural and cutaneous regions were thinner (p < 0.05) in females than males by 55 years of age. The techniques and results from this study can be applied to assess rib bone content loss in clinical settings across wide populations. Additionally, average cortex thickness results can be mapped directly to finite element models of the thorax, and regression results are used to modify such models to represent the ribs of men and women across their full adult lifespan.

Cross-sectional properties of rib geometry from an adult population

“…Ribs from a total of 240 chest CT scans were used for this study under IRB HUM00041441 as described in detail previously in ( Holcombe and Derstine, 2022 ). The population consisted of approximately uniform counts (15 or greater) of males and females within each decade of age between 20 and 90 years, with demographic averages for height, weight, and BMI provided in Table 1 .…”

“…Since that time, we have improved upon CT image analysis techniques to report rib cortical bone thickness from a wider range of live subject CT scans, and from rib levels 2 through 11 ( Holcombe and Derstine, 2022 ). To date, however, the corresponding cross-sectional geometry properties of human ribs have not been expounded upon beyond just those data obtained from cadaveric sixth ribs.…”

Influences of human thorax variability on population rib fracture risk prediction using human body models

“…As shown in the figure, the used scaling range resulted in a range of SHBM sixth level rib bone thickness variability that was similar to the extent of variability in the sample. Holcombe and Derstine (2022) recently presented SDs of rib cortical bone thickness at different measurement sites in rib levels 2 to 11, obtained from a sample comprising 240 males and females aged 20–90 years. The Holcombe and Derstine (2022) SD of rib cortical bone thickness, averaged for each rib level, was 0.24 mm for sixth level ribs and was similar in other rib levels (0.21–0.24 mm), indicating that the influence of cortical bone thickness variability on NFR2+ is not inflated by applying too-large thickness variations in the SHBM ribs.…”

Molecular age estimation based on posttranslational protein modifications in bone: why the type of bone matters

“…The significantly wider scattering of data with increasing age in all bone types is typical for many biomarkers of ageing and due to an increasing destabilisation of the tissues and their functionality during ageing. Bone structure and metabolism are changing with increasing age; this process may result in loss of bone mass, decreasing thickness, and osteoporosis [ 31 – 33 , 38 , 39 ]. These structural and metabolic changes of bone with age may cause significant changes in the protein composition of bone samples, resulting in a significantly wider scattering of D-Asp and Pen concentrations with increasing age in mixed protein samples.…”