Osteon pullout in the equine third metacarpal bone: effects of ex vivo fatigue.
Abstract: An important concept in bone mechanics is that osteons influence mechanical properties in several ways, including contributing to toughness and fatigue strength by debonding from the interstitial matrix so as to "bridge" developing cracks. Observations of "pulled out" osteons on fracture surfaces are thought to be indicative of such behavior. We tested the hypothesis that osteon pullout varies with mode of loading (fatigue vs. monotonic), cortical region, elastic modulus, and fatigue life. Mid-diaphseal beams from the dorsal, medial, and lateral regions of the equine third metacarpal bone were fractured in four point bending by monotonic loading to failure under deflection control, with or without 10(5) cycles of previous fatigue loading producing 5000 microstrain (15-20% of the expected failure strain) on the first cycle; or sinusoidal fatigue loading to failure, under load or deflection control, with the initial cycle producing 10,000 microstrain (30-40% of the expected failure strain). Using scanning electron microscopy, percent fracture surface area exhibiting osteon pullout (%OP.Ar) was measured. Monotonically loaded specimens and the compression side of fatigue fracture surfaces exhibited no osteon pullout. In load-controlled fatigue, pullout was present on the tension side of fracture surfaces, was regionally dependent (occurring to a greater amount dorsally), and was correlated negatively with elastic modulus and positively with fatigue life. Regional variation in %OP.Ar was also significant for the pooled (load and deflection controlled) fatigue specimens. %OP.Ar was nearly significantly greater in deflection controlled fatigue specimens than in load-controlled specimens (p=0.059). The data suggest that tensile fatigue loading of cortical bone eventually introduces damage that results in osteonal debonding and pullout, which is also associated with increased fatigue life via mechanisms that are not yet clear.
Publication Date: 2003-04-23 PubMed ID: 12706021DOI: 10.1016/S0736-0266(02)00232-2Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The researchers investigated how the pulling out of microscopic structural units in bone, called osteons, as a bone is stressed or “fatigued,” affects the strength and durability of horse metacarpal bones (bones in the horse’s lower leg). The study concludes that such pullout is correlated with factors such as how the bone is loaded, its stiffness, and how long it can endure stress.
Objective and Hypothesis
- The aim of this study was to understand whether the process known as ‘osteon pullout’ varies with factors such as type and area of loading, stiffness (measured as ‘elastic modulus’), and the length of time the bone can withstand stress or ‘fatigue life’.
- The team hypothesized that osteon pullout influenced the mechanical properties of bones, adding to their fatigue strength and toughness by separating from the surrounding matrix to bridge developing cracks.
Methodology
- Bones from various areas of the equine (horse) lower leg (third metacarpal bone) were tested under a number of different conditions.
- These conditions included continuous direct loading to the point of failure, both with and without several rounds of fatigue loading beforehand; and also variable fatigue loading to the point of failure. In each case, the initial level of stress applied to the bones was a significant percentage of the expected failure strain.
- The ‘pullout’ of osteons was examined using scanning electron microscopy, and the percentage of the fracture surface exhibiting this phenomenon was quantified.
Findings
- The research revealed zero osteon pullout in bones loaded monotonically (i.e., without any previous fatigue loading), as well as in bones on the compression side of the fracture when fatigue loading was applied.
- On the tension side of fractures produced by load-controlled fatigue, osteon pullout was observed.
- Osteon pullout appeared to be region-specific, and was found to be greater on the dorsal (back) side. It was also inversely correlated with elastic modulus (i.e., the stiffer the bone, the less pullout) and directly correlated with fatigue life (the longer a bone was able to withstand stress, the more pullout).
- A nearly significant increase in osteon pullout was found with deflection-controlled fatigue loading compared to load-controlled loading.
Conclusion
- The results suggest that tensile fatigue loading of bones eventually causes damage that results in osteonal debonding and pullout.
- This phenomenon is also associated with longer fatigue life of the bone. However, the mechanisms behind this are yet to be fully understood and needs further investigation.
Cite This Article
APA
Hiller LP, Stover SM, Gibson VA, Gibeling JC, Prater CS, Hazelwood SJ, Yeh OC, Martin RB.
(2003).
Osteon pullout in the equine third metacarpal bone: effects of ex vivo fatigue.
J Orthop Res, 21(3), 481-488.
https://doi.org/10.1016/S0736-0266(02)00232-2 Publication
Researcher Affiliations
- Orthopaedic Research Laboratories, School of Medicine, University of California at Davis, 95616, USA.
MeSH Terms
- Animals
- Bone Remodeling / physiology
- Fractures, Stress / physiopathology
- Haversian System / injuries
- Haversian System / physiopathology
- Haversian System / ultrastructure
- Horse Diseases / physiopathology
- Horses
- Metacarpus / injuries
- Metacarpus / physiopathology
- Microscopy, Electron, Scanning
- Weight-Bearing / physiology
Grant Funding
- AR41644 / NIAMS NIH HHS
Citations
This article has been cited 15 times.- Doube M. Closing cones create conical lamellae in secondary osteonal bone. R Soc Open Sci 2022 Aug;9(8):220712.
- Nguyen JT, Barak MM. Secondary osteon structural heterogeneity between the cranial and caudal cortices of the proximal humerus in white-tailed deer. J Exp Biol 2020 Jun 11;223(Pt 11).
- Shah FA, Ruscsák K, Palmquist A. 50 years of scanning electron microscopy of bone-a comprehensive overview of the important discoveries made and insights gained into bone material properties in health, disease, and taphonomy. Bone Res 2019;7:15.
- Rajão MD, Leite CS, Nogueira K, Godoy RF, Lima EMM. The bone response in endurance long distance horse. Open Vet J 2019 Apr;9(1):58-64.
- Campbell AM, Cler ML, Skurla CP, Kuehl JJ. Damage accumulation of bovine bone under variable amplitude loads. Bone Rep 2016 Dec;5:320-332.
- Poundarik AA, Vashishth D. Multiscale imaging of bone microdamage. Connect Tissue Res 2015 Apr;56(2):87-98.
- Skedros JG, Sybrowsky CL, Anderson WE, Chow F. Relationships between in vivo microdamage and the remarkable regional material and strain heterogeneity of cortical bone of adult deer, elk, sheep and horse calcanei. J Anat 2011 Dec;219(6):722-33.
- Skedros JG, Kiser CJ, Keenan KE, Thomas SC. Analysis of osteon morphotype scoring schemes for interpreting load history: evaluation in the chimpanzee femur. J Anat 2011 May;218(5):480-99.
- Chung DH, Dechow PC. Elastic anisotropy and off-axis ultrasonic velocity distribution in human cortical bone. J Anat 2011 Jan;218(1):26-39.
- Skedros JG. A 50-year perspective on the use and potential of artiodactyl calcanei in bone adaptation studies. Biol Rev Camb Philos Soc 2026 Feb;101(1):437-485.
- Cao X, Xiao S, Shen C, Fan Y. Microdamage in biological hard tissues and its repair mechanisms. Biomed Eng Online 2025 Aug 25;24(1):102.
- Skedros JG, Dayton MR, Cronin JT, Mears CS, Bloebaum RD, Wang X, Bachus KN. Roles of collagen cross-links and osteon collagen/lamellar morphotypes in equine third metacarpals in tension and compression tests. J Exp Biol 2024 Jul 15;227(14).
- Skedros JG, Dayton MR, Bloebaum RD, Bachus KN, Cronin JT. Strain-mode-specific mechanical testing and the interpretation of bone adaptation in the deer calcaneus. J Anat 2024 Mar;244(3):411-423.
- Marty AG, Barbone PE, Morgan EF. Multiscale theoretical model shows that aging-related mechanical degradation of cortical bone is driven by microstructural changes in addition to porosity. J Mech Behav Biomed Mater 2023 Sep;145:106029.
- Ko YG. Formation of oriented fishbone-like pores in biodegradable polymer scaffolds using directional phase-separation processing. Sci Rep 2020 Sep 2;10(1):14472.
Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists
