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ACKNOWLEDGEMENTS
The authors would like to thank the donors for their generous gifts. Thank you to the Forensic Anthropology Center at Texas State University – San Marcos for the use of some their samples.
Lastly, thank you to all the members of the Skeletal Biology Laboratory and the Injury Biomechanics Research Center at OSU, especially Randee Hunter and Michelle Murach.
REFERENCES CITED
CONCLUSIONS
INTRODUCTION
• As the elderly population continues to increase, understanding the etiology of
age-related bone loss becomes of increasing importance. Both trabecular and
cortical bone diminish with age. However, in the elderly, trabecular bone within
the rib is almost non-existent, while cortical bone loss is characterized by large
pores on the endosteal envelope, resulting in trabecularization of the cortex
(Zebaze et al., 2009).
• Evidence suggests that bone loss occurs at a differential rate between the
pleural and cutaneous regions of the rib, though what drives this remains unclear.
• This study examines the prevalence and location of cortical resorption via
porosity in the ribs of elderly individuals. Patterns of bone loss are explored by
sex, as well as by intra-individual comparison of the pleural and cutaneous
cortices of the rib.
Agnew, A.M., Moorhouse, K., Kang, Y.-S., Donnelly, B.R., Pfefferle, K., Manning, A.X., Litsky, A.S, Herriott, R., Abdel-Rasoul, M.,
Bolte, J.H. IV, 2013. The Response of Pediatric Ribs to Quasi-static Loading: Mechanical Properties and Microstructure. Ann.
Biomed. Eng. 41 (12), 2501–2514.
Rasband, W.S., ImageJ, U. S. National Institutes of Health, Bethesda, Maryland, USA, http://imagej.nih.gov/ij/, 1997-2014.
IBM Corp. Released 2013. IBM SPSS Statistics for Macintosh, Version 22.0. Armonk, NY: IBM Corp.
Zebaze, R., Ghasem-Zadeh, A., Bohte, A., Iuliano-Burns, S., Mackie, E., Seeman, E., 2009. Age-related bone loss: The effect of
neglecting intracortical porosity. Bone 44, S117–S118.
Mean%
SD%
Cutaneous)Cortex)
1.6957)
0.95887)
Pleural)Cortex)
0.8378)
1.36962)
• Our results show that in elderly individuals, the cutaneous cortex undergoes higher rates of bone loss than the
pleural cortex of the rib. When coupled with previous work that found the same pattern in the ribs of juveniles
undergoing modeling drift (Agnew et al., 2013), this suggests a preferential preservation of the pleural cortex over
that of the cutaneous cortex throughout life. Future work should examine both juvenile and adult samples to
determine if this pattern holds through all decades of life and why.
MATERIALS AND METHODS
• The sample is composed of 34 elderly individuals, 18 male and 15 female,
between 63–94 years of age (mean = 79.06, SD = 8.36 years). Complete cross-
sections were taken at the left, midshaft of the 6
th rib and slides prepared
following standard histological protocols. All slides were photographed at 40X
magnification and all data were collected using ImageJ.
• Ribs were photographed and then digitally bisected into pleural and cutaneous
regions for data collection (defined by Imin). Variables collected are listed in
Table 1. All areas were manually traced and only those pores with an area ≥0.02
mm2 were included in the analyses (Fig. 1).
• Normality tests indicated that %Porosity values were not normally distributed, so
log transformation was applied to normalize the data. Independent sample t-tests
were run to compare %Porosity values between the sexes. Then, paired sample
t-tests were used to compare %CuPorosity and %PlPorosity.
Variab le
Definition
Ct.Ar
Total area between periosteal and endosteal borders
Po.Ar
Total area of pores within cortex
%Porosity
(Po.Ar/Ct.Ar)*100
RESULTS AND DISCUSSION
• Independent sample t-tests indicated no significant differences between males and females in the tested porosity
indices (Table 2). Samples were pooled for further analyses.
• Paired sample t-tests indicated that the cutaneous cortex of the rib has a significantly higher %Porosity than the
pleural cortex (p = 0.001, Table 3)
• Delimitating between cortex and trabeculae was a problem in this study (Fig. 2). Though we used traditional Ct.Ar
measurements, it must be noted that these measurements exclude trabecularized cortex, thus underestimating both
cortex size and the associated increase in porosity (Zebaze et al., 2009). This may account for seemingly higher
%PlPorosity values in some of the study samples. While the trend in increased %CuPorosity is strong enough to
remain evident despite this quantification issue, researchers should keep in mind that traditional cortical
measurements may be underestimating rates of cortical bone loss.
t"
df"
p"
Total)Cortex)
1.574)
31)
0.126)
Cutaneous)Cortex)
1.109)
31)
0.276)
Pleural)Cortex)
0.738)
28)
0.467)
Ta bl e 2 . I n de p en d en t t-test Between Males and Females
Table 1. Collected Variablesa
Fig. 1. Rib stained in basic fuchsin, illustrating data collection protocol. Red line
indicates delineation between pleural and cutaneous regions. Inset represents
two measured pores included in the analyses.
aEach variable was also collected and analyzed for the cutaneous and pleural halves of
the rib specifically.
Table 3. Paired Sample t-testa Means
at(29) = 3.524, p = 0.001*
Fig. 2. A. Discernable endosteal border for porous cortex. Rib stained in basic fuchsin.
B. Endosteal border degraded by cortical trabecularization.
A) B)
Cutaneous
Pleural
