Method and system for modeling bone structure

• US 7,353,153 B2
• Filed: 05/11/2004
• Issued: 04/01/2008
• Est. Priority Date: 10/17/2001
• Status: Expired due to Term

• 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.
• Primary Examiner(s): THANGAVELU, KANDASAMY
• Application Number:
  US10/844,051
• Publication Number:
  US 20050131662A1
• Time in Patent Office: 1,421 Days
• Field of Search: 703/2, 424/9.2, 424/49, 382/128, 600/586, 600/36, 600/449, 600/407, 514/12, 623/23.56, 623/23.61, 298/966, 700/98, 700/182
• US Class Current: 703/11
• CPC Class Codes: A61B 2034/105 Modelling of the patient, e.g. for ligaments or bones
• CPC Class Codes: B33Y 50/00 Data acquisition or data processing for additive manufacturing
• 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 method of predicting a mechanical response of a region of a subject bone to an applied force comprising the steps of:

(a) identifying a subject bone;

(b) selecting at least one database comprising empirical data representative of the subject bone, wherein the empirical data is based on recorded observations of at least one cadaveric bone corresponding to the subject bone, wherein recording the observations comprises;

(1) selecting a three-dimensional macrostructural sample from the cadaveric bone in which microstructural elements are present;

(2) identifying at least one individual microstructural element in the selected macrostructural sample; and

(3) generating viscoelastic data comprising at least one mechanical property of the identified microstructural element obtained by subjecting the identified microstructural element to at least one force;

(c) using the database with a computer program to generate a simulated region of the subject bone, the simulated region comprising at least one simulated microstructural element, wherein the computer program performs the steps of;

(1) defining a simulated three-dimensional region corresponding to the simulated microstructural element of the simulated region of the subject bone;

(2) creating a finite element mesh defining a finite number of three-dimensional elements filling the simulated three-dimensional region; and

(3) assigning at least one property to each of a plurality of the elements in the finite element mesh using viscoelastic data from the database;

(d) using a computer program to predict a mechanical response of the region of the subject bone to an applied force, wherein the computer program performs the steps of;

(1) generating a simulated force applied to the simulated three-dimensional region;

(2) calculating a response to the simulated force for each of a plurality of elements in the finite element mesh using the at least one assigned property for each element;

(3) computing a response of the simulated three-dimensional region to the simulated force using the calculated responses of the plurality of elements in the finite element mesh;

(4) computing the mechanical response of the simulated region of the subject bone from the computed response of the simulated three-dimensional region to the simulated force; and

(5) outputting the computed mechanical response of the region of the subject bone to the simulated force.

2. The method of claim 1, wherein

the database further comprises at least one of empirically collected dimensional data and distributional data from at least one ultrastructural component from the sample, and

elements in the finite element mesh are defined at least in part using the ultrastructural data.

3. The method of claim 2, wherein the ultrastructural component is at least one of a lacuna and a canalicula from the sample.

4. The method of claim 2, wherein elements in the finite element mesh are representative of an ultrastructural component.

5. The method of claim 4, wherein the ultrastructural component is at least one of a lacuna and a canalicula from the sample.

6. The method of claim 1, wherein the region of the subject bone corresponds to a lamella.

7. The method of claim 1, wherein the region of the subject bone corresponds to an osteon.

8. The method of claim 1, wherein the region of subject bone corresponds to a macrostructural region comprising a plurality of micro structural elements.

9. The method of claim 1, wherein at least one force is selected from tension, compression, shear, bending, and torsion.

10. The method of claim 1, wherein the microstructural elements identified from the sample are lamellae.

11. The method of claim 10, wherein the mechanical properties are selected from tension, compression, shear, bending, torsion, prestress, pinching, cement line slippage, stress distribution, and strain distribution.

12. The method of claim 10, wherein the lamellae are one or both of bright and dark lamellae.

13. The method of claim 1, wherein the microstructural elements identified from the sample are osteons.

14. The method of claim 13, wherein the osteons are one or both of longitudinal and alternate osteons.

15. The method of claim 13, wherein the osteon mechanical properties are selected from angle-of-twist as a function of torque per unit force, strain rate, and time.

16. The method of claim 1, wherein

the viscoelastic data further comprises empirically observed orientations of collagen bundles within micro structural elements, and

the orientation data is used in assigning properties to elements.

17. The method of claim 16, wherein the orientation data corresponds to lamellae organized within an osteon having an osteon axis, and wherein at least one dark lamella within the osteon is oriented at an angle ranging from 0 degrees to substantially less than ±

45 degrees with respect to the osteon axis.

18. The method of claim 16, wherein the orientation data corresponds to lamellae organized within an osteon having an osteon axis, and wherein at least one bright lamella within the osteon is oriented at an angle ranging from a midpoint orientation with respect to the osteon axis to an angle of about ±

45 degrees with respect to the midpoint orientation.

19. The method of claim 16, wherein the orientation data corresponds to lamellae organized within an osteon having an osteon axis, and wherein at least one dark lamella within the osteon is oriented at an angle of up to ±

23 degrees with respect to the osteon axis.

20. The method of claim 16, wherein the orientation data corresponds to lamellae organized within an osteon having an osteon axis, and wherein at least one bright lamella within the osteon is oriented at an angle ranging from a midpoint orientation with respect to the osteon axis to an angle of about ±

23 degrees with respect to the midpoint orientation.

21. The method of claim 1, wherein the simulated three-dimensional region corresponding to a selected region of the subject bone is determined from an in vivo scan of the subject bone.

22. The method of claim 8, wherein

the database further comprises empirical data recording the spatial distribution of microstructural elements within a cadaveric sample, and

the step of generating a simulated region of the subject bone further comprises defining a spatial configuration of simulated microstructural elements in the simulated region using data from the database.

23. The method of claim 8, wherein

the database further comprises empirical data recording the spatial distribution of microstructural elements within the subject bone, and

the step of generating a simulated region of the subject bone further comprises defining a spatial configuration of simulated microstructural elements in the simulated region using data from the database.

24. The method of claim 23, wherein the spatial configuration of simulated microstructural elements is observed using an in vivo scan of the subject bone to obtain microstructure distribution in the subject bone.

25. The method of claim 1, wherein at least steps (d)(2) and d(3) are repeated for each of a plurality of simulated forces.

26. The method of claim 25, wherein the simulated force is applied incrementally.

27. The method of claim 1, wherein the mechanical response comprises fracture initiation, wherein fracture initiation comprises microcracking, debonding, breakage, void growth, or combinations thereof.

28. The method of claim 1, wherein the mechanical response comprises fracture propagation.

29. The method of claim 1, wherein the step of calculating a response to the simulated force accounts for a prestress distribution in the simulated region of the subject bone.

30. The method of claim 1, wherein the cadaveric bone is compact bone.

31. The method of claim 1, wherein the cadaveric bone is obtained from a human.

32. The method of claim 1, further comprising the steps of:

generating at least one distribution function corresponding to the distribution of empirically observed values for a measurement recorded in the database;

using the distribution function to assign values for at least one property of the elements in the finite element mesh.

33. The method of claim 1, wherein

the subject bone corresponds to a bone attached to a prosthesis, and

the applied force corresponds to forces acting on the bone as a consequence of the attached prosthesis.

34. A computerized bone model stored on one or more computer readable media for predicting a mechanical response of a region of a subject bone to an applied force, comprising:

(a) a database comprising empirical data representative of a subject bone, wherein the empirical data comprises recorded observations of at least one microstructural element from a cadaveric bone corresponding to the subject bone; and

(b) a set of computer readable instructions for use with the database comprising;

(1) instructions for generating a simulated region of the subject bone wherein the simulated region comprises at least one simulated microstructural element;

(2) instructions for defining a simulated three-dimensional region corresponding to the simulated microstructural element of the simulated region of the subject bone;

(3) instructions for creating a finite element mesh defining a finite number of three-dimensional elements filling the simulated three-dimensional region;

(4) instructions for assigning at least one material property to each of a plurality of the elements in the finite element mesh using data from the database;

(5) instructions for applying a simulated force to the simulated three-dimensional region;

(6) instructions for calculating a response to the simulated force for each of the plurality of elements in the finite element mesh using the assigned at least one property for each element;

(7) instructions for computing a response of the simulated three-dimensional region to the simulated force using the calculated responses of the plurality of elements in the finite element mesh;

(8) instructions for computing the mechanical response of the simulated region of the subject bone from the computed response of the simulated three-dimensional region to the simulated force; and

(9) instructions for outputting the computed mechanical response of the region of the subject bone to the simulated force.

35. The computerized bone model of claim 34 wherein

the database further comprises at least one of empirically collected dimensional data and distributional data from at least one ultrastructural component, and

elements in the finite element mesh are defined at least in part using the ultrastructural data.

36. The computerized bone model of claim 35, wherein the ultrastructural component is at least one of a lacuna and a canalicula.

37. The computerized bone model of claim 35, wherein elements in the finite element mesh are representative of an ultrastructural component.

38. The computerized bone model of claim 37, wherein the ultrastructural component is at least one of a lacuna and a canalicula.

39. The computerized bone model of claim 34, wherein the region of the subject bone corresponds to a lamella.

40. The computerized bone model of claim 34, wherein the region of the subject bone corresponds to an osteon.

41. The computerized bone model of claim 34, wherein the region of subject bone corresponds to a macrostructural region comprising a plurality of microstructural elements.

42. The computerized bone model of claim 34, wherein the microstructural elements identified from the sample are lamellae.

43. The computerized bone model of claim 42, wherein the mechanical properties are selected from tension, compression, shear, bending, torsion, prestress, pinching, cement line slippage, stress distribution, and strain distribution.

44. The computerized bone model of claim 42, wherein the lamellae are one or both of bright and dark lamellae.

45. The computerized bone model of claim 34, wherein the microstructural elements identified from the sample are osteons.

46. The computerized bone model of claim 45, wherein the osteons are one or both of longitudinal and alternate osteons.

47. The computerized bone model of claim 45, wherein the osteon mechanical properties are selected from angle-of-twist as a function of torque per unit force, strain rate, and time.

48. The computerized bone model of claim 34, wherein

the viscoelastic data further comprises empirically observed orientations of collagen bundles within microstructural elements, and

the orientation data is used in assigning properties to elements.

49. The computerized bone model of claim 48, wherein the orientation data corresponds to lamellae organized within an osteon having an osteon axis, and wherein at least one dark lamella within the osteon is oriented at an angle ranging from 0 degrees to substantially less than ±

45 degrees with respect to the osteon axis.

50. The computerized bone model of claim 48, wherein the orientation data corresponds to lamellae organized within an osteon having an osteon axis, and wherein at least one bright lamella within the osteon is oriented at an angle ranging from a midpoint orientation with respect to the osteon axis to an angle of about ±

45 degrees with respect to the midpoint orientation.

51. The computerized bone model of claim 48, wherein the orientation data corresponds to lamellae organized within an osteon having an osteon axis, and wherein at least one dark lamella within the osteon is oriented at an angle of up to ±

23 degrees with respect to the osteon axis.

52. The computerized bone model of claim 48, wherein the orientation data corresponds to lamellae organized within an osteon having an osteon axis, and wherein at least one bright lamella within the osteon is oriented at an angle ranging from a midpoint orientation with respect to the osteon axis to an angle of about ±

23 degrees with respect to the midpoint orientation.

53. The computerized bone model of claim 34, wherein the simulated three-dimensional region corresponding to a selected region of the subject bone is determined from an in vivo scan of the subject bone.

54. The computerized bone model of claim 41, wherein

the database further comprises empirical data recording the spatial distribution of microstructural elements within a cadaveric sample, and

the set of computer readable instructions further comprises instructions for defining a spatial configuration of simulated microstructural elements in the simulated region using data from the database.

55. The computerized bone model of claim 41, wherein

the database further comprises empirical data recording the spatial distribution of microstructural elements within the subject bone, and

the set of computer readable instructions further comprises instructions for defining a spatial configuration of simulated microstructural elements in the simulated region using data from the database.

56. The computerized bone model of claim 55, wherein the spatial configuration of simulated microstructural elements is observed using an in vivo scan of the subject bone to obtain microstructure distribution in the subject bone.

57. The computerized bone model of claim 34, wherein the cadaveric bone is compact bone.

58. The computerized bone model of claim 34, wherein the cadaveric bone is obtained from a human.

59. The computerized bone model of claim 34, wherein the set of computer readable instructions further comprises:

instructions for generating at least one distribution function corresponding to the distribution of empirically observed values for a measurement recorded in the database;

instructions for using the distribution function to assign values for at least one property of elements in the computerized model.