Multidirectional morphology and mechanics of osteonic lamellae

• US 20030216899A1
• Filed: 02/03/2003
• Published: 11/20/2003
• Est. Priority Date: 10/17/2001
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Ascenzi, Maria-Grazia, Kabo, John M.
• Granted Patent: US 7,283,940 B2
• Time in Patent Office: Days
• US Class Current: 703/11
• CPC Class Codes: A61B 17/58 for osteosynthesis, e.g. bone plates, screws , setting implements or the like A61B17/14, A61B17/16 take precedence
• CPC Class Codes: A61B 2017/564 Methods for bone or joint treatment
• CPC Class Codes: A61B 34/10 Computer-aided planning, simulation or modelling of surgical operations
• CPC Class Codes: A61B 90/06 Measuring instruments not otherwise provided for
• CPC Class Codes: B33Y 80/00 Products made by additive manufacturing
• CPC Class Codes: G09B 23/30 Anatomical models G09B23/281 - G09B23/288 take precedence

Abstract

The present invention discloses a structural and mechanical model and modeling methods for human bone based on bone'"'"'s hierarchical structure and on its hierarchical mechanical behavior. The model allows for the assessment of bone deformations, computation of strains and stresses due to the specific forces acting on bone during function, and contemplates forces that do or do not cause viscous effects and forces that cause either elastic or plastic bone deformation.

Claims

1. A model of macrostructural properties of a bone, wherein said model comprises hierarchical structural and hierarchical mechanical properties of microstructure of said bone and interactions of said bone with external force.

2. A model as defined in claim 1, wherein said bone is compact bone or cancellous bone.

3. A model as defined in claim 1, wherein said mechanical properties are selected from the group consisting of tension, compression, shear, bending, torsion, prestress, pinching, and cement line slippage.

4. A method of predicting deformation and fractures of bone using the model as defined in claim 1.

5. A method of identifying the requirements of bone reconstruction and prosthesis using the model as defined in claim 1.

6. A model of compact adult bone, wherein said model comprises the viscoelastic properties of at least one type of a secondary osteon.

7. The model of claim 6, wherein said secondary osteon is a longitudinal osteon or an alternate osteon.

8. The model of claim 6, wherein the viscoelastic properties comprises at least one parameter selected from the group consisting of mechanical properties, collagen content, mucopolysaccharide content, hydroxyapatite content, collagen bundle orientation relative to osteon axis, osteocyte content, osteoblast content, and content of porosity fluids.

9. The model of claim 8, wherein the viscoelastic properties comprises mechanical properties, collagen content, mucopolysaccharide content, hydroxyapatite content, and collagen bundle orientation relative to osteon axis.

10. The model of claim 8, wherein osteon mechanical properties comprises an angle-of-twist as a function of torque, osteon hydroxyapatite content, strain rate, or time.

11. The model of claim 10, wherein the angle-of-twist as a function of torque is derived from tests conducted under monotonic or dynamic loading.

12. The model of claim 10, wherein angle-of-twist as a function of torque at an approximately constant strain rate and approximately constant hydroxyapatite content is represented by a Ramgood-Osgood equation.

13. The model of claim 12, wherein a higher hydroxyapatite content leads to a higher angle-of-twist as a function of torque.

14. The model of claim 12, wherein a higher strain rate leads to a higher angle-of-twist as a function of torque.

15. The model of claim 6, comprising the viscoelastic properties of longitudinal and secondary alternate osteons.

16. The model of claim 15, wherein the viscoelastic properties comprises mechanical properties, collagen content, mucopolysaccharide content, hydroxyapatite content, and collagen bundle orientation relative to osteon axis.

17. The model of claim 16, wherein the ratio of collagen and mucopolysaccharides in longitudinal osteons as compared to collagen and mucopolysaccharides in alternate osteons is less than 1 for longitudinal and alternate osteons with approximately equal hydroxyapatite contents.

18. The model of claim 6, wherein the internal diameter of a reference osteon is about 40 μ

m, the external diameter of the reference osteon is about 210 μ

m, and the height of the reference osteon is about 500 μ

m.

19. The model of claim 18, wherein a longitudinal reference osteon comprises about 12 laminae.

20. The model of claim 18, wherein an alternate reference osteon comprises about 36 laminae.

21. The model of claim 6, comprising a Finite Element Model (FEM).

24. A method of identifying the requirements of bone reconstruction and prosthesis using the model of claim 6.

30. The method of claim 24, wherein the ratio of collagen and mucopolysaccharides in a longitudinal osteon as compared to an alternate osteon is less than 1, for a longitudinal and alternate osteon with approximately equal hydroxyapatite contents.

31. The method of claim 21, wherein the collagen-bundle direction related to osteon axis is determined by circularly polarizing light microscopy, confocal microscopy or X-ray diffraction.

22. A method of predicting deformation and fractures of compact adult bone comprising using a model of compact adult bone, wherein said model comprises the viscoelastic properties of secondary longitudinal and alternate osteons.

23. The method of claim 22, wherein the model simulates fracture propagation by calculating stress distribution as a function of a torque applied to the bone.

25. A method of preparing a model of the viscoelastic properties of bone, wherein said method comprises determining viscoelastic properties of alternate and longitudinal osteons.

26. The method of claim 25, wherein viscoelastic properties comprises mechanical properties, collagen content, mucopolysaccharide content, hydroxyapatite content, and collagen bundle orientation relative to osteon axis.

27. The method of claim 26, wherein the mechanical properties are determined by evaluating angle-of-twist as a function of torque, osteon hydroxyapatite content, strain rate, or time.

28. The method of claim 27, wherein angle-of-twist as a function of torque is determined by quasi-static torsional loading to rupture.

29. The method of claim 26, comprising determining the ratio of collagen and mucopolysaccharides in a longitudinal osteon as compared to those of an alternate osteon by the following method:

(i) drying the longitudinal and alternate osteons to constant weight;

(ii) separately contacting the longitudinal and alternate osteons with acid to promote the hydrolysis of collagen to hydroxyproline and mucopolysaccharides to hexosamine; and

(iii) separating hydroxyproline from hexosamine; and

(iv) determining the ratio of hydroxyproline and hexosamine in the longitudinal osteon as compared to the alternate osteon;

wherein the ratio of hydroxyproline and hexosamine in the longitudinal osteon as compared to the alternate osteon corresponds to the ratio of collagen and mucopolysaccharides in the longitudinal osteon as compared to the alternate osteon.

32. A method of identifying lamellar mechanical behavior wherein said method comprises

a.) isolating lamellae, and

b.) identifying lamellar mechanical behavior of the isolated lamellae by confocal microscopy, polarized light microscopy, and x-ray diffraction.

34. A method of determining the role of lamellar ultrastructure in the mechanical behavior of a single lamella comprising using the method of claim 32 to identify lamellar mechanical behavior.

36. A method of identifying the requirements of bone reconstruciton and prosthesis wherein said method comprises

a.) determining the role of lamellar ultrastructure using the method of claim 34,

b.) comparing the role of lamellar ultrastructure to bone used for reconstruction or prosthesis.

33. A method of identifying lamellar mechanical behavior wherein said method comprises

a) isolating lamellae,

b) identifying regions of unidirectional collagen bundles by confocal microscopy,

d.) measuring the regions of unidirectional collagen bundles, and

e.) determining differences in structural response of the isolated lamellae in orthagonal directions by quasi-static tensional testing,

wherein the measurements of the regions of unidirectional collagen bundles and the differences in structural response increase understanding of the make-up of bone at the single lamella level.

35. A method of determining the quasi-static tensional behavior of osteonic lamella wherein said method comprises using a numerical model of fully calcified osteonic lamella wherein the numeric model reflects the geometry and distribution and orientation of lamella components.