Screws of cortical bone and method of manufacture thereof Number:7,063,702 from the United States Patent and Trademark Office (PTO) owispatent

Title: Screws of cortical bone and method of manufacture thereof

Abstract: A screw formed of cortical bone for use in the human body with an implant having a screw hole for receiving at least a portion of a screw therethrough, includes a shaft with a thread along at least a portion of its length. The thread has an outer diameter dimensioned to pass through the screw hole in the implant. The trailing end of the screw is configured to cooperatively engage at least a portion of the screw hole of the implant so as to prevent the screw from linear motion along the mid-longitudinal axis of the shaft in a direction opposite to the direction of insertion when the screw is threaded through the screw hole to attach the implant to a bone portion of the human body. The screw is formed substantially of cortical bone of a single cortical thickness.

Patent Number: 7,063,702 Issued on 06/20/2006 to Michelson

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Inventors:	Michelson; Gary K. (Venice, CA)
Assignee:	SDGI Holdings, Inc. (Wilmington, DE)
Appl. No.:	970294
Filed:	October 2, 2001

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Current U.S. Class:	606/73
Current International Class:	A61B 17/58 (20060101)
Field of Search:	606/69-73 623/16.11,17.11,23.51,23.58,23.61,23.63 411/411,417,423,416,308,904

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References Cited [Referenced By]

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U.S. Patent Documents

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Primary Examiner: Robert; Eduardo C.
Assistant Examiner: Araj; Michael J.
Attorney, Agent or Firm: Martin & Ferraro, LLP

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Parent Case Text

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RELATED APPLICATION

This is a divisional of application Ser. No. 09/566,055, filed May 5, 2000, which claims the benefit of U.S. provisional application No. 60/132,671, filed May 5, 1999; all of which are incorporated herein by reference.

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Claims

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What is claimed is:

1. A screw for use in the human body formed of cortical bone from a major long bone having a medullary canal, said screw comprising a leading end, a trailing end opposite said leading end, and a shaft therebetween, said shaft having a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said shaft having a cross section transverse to said mid-longitudinal axis through said thread having a concavedly arcuate portion and a convexedly arcuate portion opposite said concavedly arcuate portion, said concavedly arcuate portion being formed from at least a portion of the medullary canal and extending along a majority of the length of said screw, said cross section bisecting a rotation of said thread.

2. The screw of claim 1, wherein said cross section has opposite convex portions with approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section being through said concavedly arcuate portion of said thread.

3. The screw of claim 1, wherein said trailing end is configured to cooperatively engage at least a portion of the screw hole of an implant so as to prevent said screw from linear motion along the mid-longitudinal axis of said shaft in a direction opposite to the direction of insertion when said screw is threaded through a screw hole to attach the implant to a bone portion of the human body.

4. The screw of claim 1, wherein said screw is formed substantially of cortical bone of a single cortical thickness.

5. The screw of claim 4, wherein said cortical bone is obtained from a human.

6. The screw of claim 4, wherein said cortical bone is obtained from a generally intramembraneously formed cortical bone.

7. The screw of claim 4, wherein said cortical bone is obtained from a large tubular bone of a human.

8. The screw of claim 7, wherein said cortical bone is from the diaphyseal region of said large tubular bone.

9. The screw of claim 7, wherein the tubular bone is a femur.

10. The screw of claim 1, further comprising an enlarged portion proximate said trailing end with a dimension transverse to the mid-longitudinal axis of said shaft greater than said outer diameter of said thread, said enlarged portion configured to prevent said trailing end from passing through the screw hole in the implant.

11. The screw of claim 10, wherein said enlarged portion forms a head.

12. The screw of claim 10, wherein said enlarged portion forms a lip.

13. The screw of claim 1, wherein said trailing end includes a second thread having a different thread pitch than said thread along said shaft.

14. The screw of claim 13, wherein the thread pitch of said second thread is similar to a metal screw pitch.

15. The screw of claim 13, wherein the thread pitch of said thread along said shaft is similar to a wood screw pitch.

16. The screw of claim 1, wherein the thread pitch of said thread along said shaft is similar to a wood screw pitch.

17. The screw of claim 1, wherein at least a portion of said trailing end is expandable.

18. The screw of claim 17, wherein at least a portion of said trailing end is divided into at least two members with an opening therebetween.

19. The screw of claim 18, further comprising an insert configured to fit into said opening of said trailing end and to move said at least two members apart when inserted into said opening.

20. The screw of claim 19, wherein said insert is configured to be inserted by linear advancement into said opening.

21. The screw of claim 20, wherein said insert has a cruciate shape and said opening has a corresponding cruciate shape.

22. The screw of claim 19, wherein said insert is configured to be inserted by rotational movement into said opening.

23. The screw of claim 22, wherein said insert is threaded.

24. The screw of claim 1, wherein at least a portion of said trailing end is configured to cooperatively engage a driving instrument for insertion of said screw.

25. The screw of claim 24, wherein said trailing end includes a recess to cooperatively engage a driving instrument.

26. The screw of claim 25, wherein said recess is one of cruciate-shape and hex-shaped.

27. The screw of claim 24, wherein said trailing end includes a protrusion to cooperatively engage a driving instrument.

28. The screw of claim 27, wherein said protrusion has a hex-shaped perimeter.

29. The screw of claim 1, wherein said thread is sharper proximate said leading end than proximate said trailing end.

30. The screw of claim 1, wherein said thread has a V-shaped cross section with an apex and a base adjacent to said shaft, said base being substantially wider than said apex.

31. The screw of claim 1, wherein said thread has a peak as measured from said shaft, the peak being greater proximate said leading end than said trailing end.

32. The screw of claim 1, wherein said shaft has a root diameter that increases in the direction from said leading end to said trailing end.

33. The screw of claim 1, wherein said leading end forms a tip and said tip is fluted.

34. The screw of claim 1, further comprising a bioresorbable material other than cortical bone.

35. The screw of claim 34, wherein said material includes bioresorbable plastics.

36. The screw of claim 34, wherein said material includes at least one of glycolide polymers, lactide, capralactone, trimethylene carbonate, and dioxanone.

37. The screw of claim 1, wherein said screw comprises bone growth promoting material.

38. The screw of claim 37, wherein said bone growth promoting material is selected from one of bone morphogenetic protein, hydroxyapatite, and genes coding for the production of bone.

39. The screw of claim 1, wherein said screw is treated with a bone growth promoting substance.

40. The screw of claim 1, in combination with a bone growth promoting material.

41. The screw of claim 40, wherein said bone growth promoting material includes at least one of bone morphogenetic protein, mineralizing proteins, hydroxyapatite, and genetic material coding for the production of bone.

42. The screw of claim 1, in combination with an instrument for inserting said screw.

43. The screw of claim 1, wherein said thread has a plurality of turns, a majority of said turns including said concavedly arcuate portion.

44. The screw of claim 43, wherein all of said turns include said concavedly arcuate portion.

45. The screw of claim 43, wherein the radii of at least two of said concavedly arcuate portions vary along the length of said shaft.

46. The screw of claim 1, wherein said thread has an outer diameter that is generally constant along the length of said shaft.

47. A screw formed from a major long bone having a medullary canal, said screw comprising a leading end, a trailing end opposite said leading end, and a shaft therebetween, said shaft having a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said shaft having a cross section transverse to said mid-longitudinal axis through said thread having a concavedly arcuate portion and a convexedly arcuate portion opposite said concavedly arcuate portion, said concavedly arcuate portion being formed from at least a portion of the medullary canal and extending along a majority of the length of said screw, said cross section bisecting a rotation of said thread, said screw being formed by the process of cutting a strip of cortical bone having a single cortical thickness from the long bone in the direction of the longitudinal axis of the long bone and machining said strip to form a thread.

48. The screw of claim 47, wherein said strip of cortical bone is cut with a trephine having a diameter greater than the cortical thickness of the long bone.

49. The screw of claim 48, wherein said cross section has opposite convex portions with approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section being through said concavedly arcuate portion of said thread.

50. The screw of claim 47, in combination with a bone growth promoting material.

51. The screw of claim 50, wherein said bone growth promoting material includes at least one of bone morphogenetic protein, mineralizing proteins, hydroxyapatite, and genetic material coding for the production of bone.

52. The screw of claim 47, in combination with an instrument for inserting said screw.

53. The screw of claim 47, wherein said thread has a plurality of turns, a majority of said turns including said concavedly arcuate portion.

54. The screw of claim 53, wherein all of said turns include said concavedly arcuate portion.

55. The screw of claim 53, wherein the radii of at least two of said concavedly arcuate portions vary along the length of said shaft.

56. The screw of claim 47, wherein said thread has an outer diameter that is generally constant along the length of said shaft.

57. A method for forming a screw made of cortical bone, comprising the steps of: cutting a strip of cortical bone having a single cortical thickness from a long bone in the direction of the longitudinal axis of the long bone; and machining said strip to form a screw having a shaft with a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said shaft having a cross section transverse to said mid-longitudinal axis through said thread having a concavedly arcuate portion and a covexedly arcuate portion opposite said concavedly arcuate portion, said cross section bisecting a rotation of said thread.

58. The method of claim 57, wherein the cutting step includes the sub-step of using a trephine having a diameter greater than the cortical thickness of the long bone.

59. The method of claim 58, wherein the machining step includes the sub-steps of forming said cross section with opposite convex portions having approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section being through said concavedly arcuate portion of said thread.

60. The method of claim 57, further comprising the step of coating the screw with at least one of bone morphogenetic protein, mineralizing proteins, hydroxyapatite, and genetic material coding for the production of bone.

61. A screw for use in the human body formed of cortical bone from a major long bone having a medullary canal, said screw comprising: a leading end and a trailing end opposite said leading end; a shaft between said leading and trailing ends, said shaft having a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said thread having an outer diameter, said shaft having a cross section transverse to the mid-longitudinal axis through said thread having a concavedly arcuate portion and a convexedly arcuate portion opposite said concavedly arcuate portion, said concavedly arcuate portion being formed from at least a portion of the medullary canal and extending along a majority of the length of said screw, said cross section bisecting a rotation of said thread; and an enlarged portion proximate said trailing end with a dimension transverse to the mid-longitudinal axis of said shaft greater than the outer diameter of said thread, said enlarged portion configured to prevent said trailing end from passing through a screw hole in an implant, said enlarged portion including a concavedly arcuate portion formed from at least a portion of the medullary canal.

62. The screw of claim 61, wherein said cross section has opposite convex portions with approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section being through said concavedly arcuate portion of said thread.

63. The screw of claim 61, wherein said trailing end is configured to cooperatively engage at least a portion of the screw hole of the implant so as to prevent said screw from linear motion along the mid-longitudinal axis of said shaft in a direction opposite to the direction of insertion when said screw is threaded through the screw hole to attach the implant to a bone portion of the human body.

64. The screw of claim 61, wherein said screw is formed substantially of cortical bone of a single cortical thickness.

65. The screw of claim 64, wherein said cortical bone is obtained from a human.

66. The screw of claim 64, wherein said cortical bone is obtained from a generally intramembraneously formed cortical bone.

67. The screw of claim 64, wherein said cortical bone is obtained from a large tubular bone of a human.

68. The screw of claim 67, wherein said cortical bone is from the diaphyseal region of said large tubular bone.

69. The screw of claim 67, wherein the tubular bone is a femur.

70. The screw of claim 61, wherein said enlarged portion forms a head.

71. The screw of claim 61, wherein said enlarged portion forms a lip.

72. The screw of claim 61, wherein the thread pitch of said thread along said shaft is similar to a wood screw pitch.

73. The screw of claim 61, wherein at least a portion of said trailing end is configured to cooperatively engage a driving instrument for insertion of said screw.

74. The screw of claim 73, wherein said trailing end includes a recess to cooperatively engage a driving instrument.

75. The screw of claim 61, wherein said thread is sharper proximate said leading end than proximate said trailing end.

76. The screw of claim 61, wherein said thread has a V-shaped cross section with an apex and a base adjacent to said shaft, said base being substantially wider than said apex.

77. The screw of claim 61, wherein said thread has a peak as measured from said shaft, the peak being greater proximate said leading end than said trailing end.

78. The screw of claim 61, wherein said shaft has a root diameter that increases in the direction from said leading end to said trailing end.

79. The screw of claim 61, wherein said leading end forms a tip and said tip is fluted.

80. The screw of claim 61, further comprising a bioresorbable material other than cortical bone.

81. The screw of claim 80, wherein said material includes bioresorbable plastics.

82. The screw of claim 80, wherein said material includes at least one of glycolide polymers, lactide, capralactone, trimethylene carbonate, and dioxanone.

83. The screw of claim 61, wherein said screw is treated with a bone growth promoting substance.

84. The screw of claim 61, in combination with a bone growth promoting material.

85. The screw of claim 84, wherein said bone growth promoting material includes at least one of bone morphogenetic protein, mineralizing proteins, hydroxyapatite, and genetic material coding for the production of bone.

86. The screw of claim 61, in combination with an instrument for inserting said screw.

87. The screw of claim 61, wherein said thread has a plurality of turns, a majority of said turns including said concavedly arcuate portion.

88. The screw of claim 87, wherein all of said turns include said concavedly arcuate portion.

89. The screw of claim 87, wherein the radii of at least two of said concavedly arcuate portions vary along the length of said shaft.

90. The screw of claim 61, wherein said thread has an outer diameter that is generally constant along the length of said shaft.

91. A screw formed of cortical bone for use in the human body, said screw comprising a leading end, a trailing end opposite said leading end, and a shaft therebetween, said shaft having a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said shaft having a cross section transverse to said mid-longitudinal axis through said thread having a concavedly arcuate portion and a convexedly arcuate portion opposite said concavedly arcuate portion, said cross section having opposite convex portions with approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section bisecting a rotation of said thread and being through said concavedly arcuate portion of said thread.

92. The screw of claim 91, wherein said trailing end is configured to cooperatively engage at least a portion of a screw hole of an implant so as to prevent said screw from linear motion along the mid-longitudinal axis of said shaft in a direction opposite to the direction of insertion when said screw is threaded through a screw hole to attach the implant to a bone portion of the human body.

93. The screw of claim 91, wherein said screw is formed substantially of cortical bone of a single cortical thickness.

94. The screw of claim 91, wherein at least a portion of said trailing end is configured to cooperatively engage a driving instrument for insertion of said screw.

95. The screw of claim 91, further comprising a bioresorbable material other than cortical bone.

96. The screw of claim 95, wherein said material includes bioresorbable plastics.

97. The screw of claim 95, wherein said material includes at least one of glycolide polymers, lactide, capralactone, trimethylene carbonate, and dioxanone.

98. The screw of claim 91, wherein said screw comprises bone growth promoting material.

99. The screw of claim 98, wherein said bone growth promoting material is selected from one of bone morphogenetic protein, hydroxyapatite, and genes coding for the production of bone.

100. The screw of claim 91, wherein said screw is treated with a bone growth promoting substance.

101. A screw comprising a leading end, a trailing end opposite said leading end, and a shaft therebetween, said shaft having a mid-longitudinal axis, a length, and a thread extending from said shaft along at least a portion of its length, said shaft having a cross section transverse to said mid-longitudinal axis through said thread having a concavedly arcuate portion and a convexedly arcuate portion opposite said concavedly arcuate portion, said cross section having opposite convex portions with approximately the same radius, said concavedly arcuate portion and said convexedly arcuate portion being between said opposite convex portions, said convexedly arcuate portion having a radius greater than the radius of said opposite convex portions, said cross section bisecting a rotation of said thread and being through said concavedly arcuate portion of said thread, said screw being formed by the process of cutting a strip of cortical bone having a single cortical thickness from a long bone in the direction of the longitudinal axis of the long bone and machining said strip to form a thread.

102. The screw of claim 101, wherein said strip of cortical bone is cut with a trephine having a diameter greater than the cortical thickness of the long bone.

103. The screw of claim 101, in combination with a bone growth promoting material.

104. The screw of claim 103, wherein said bone growth promoting material includes at least one of bone morphogenetic protein, mineralizing proteins, hydroxyapatite, and genetic material coding for the production of bone.

105. The screw of claim 101, in combination with an instrument for inserting said screw.

106. The screw of claim 101, wherein said thread has a plurality of turns, a majority of said turns including said concavedly arcuate portion.

107. The screw of claim 106, wherein all of said turns include said concavedly arcuate portion.

108. The screw of claim 106, wherein the radii of at least two of said concavedly arcuate portions vary along the length of said shaft.

109. The screw of claim 101, wherein said thread has an outer diameter that is generally constant along the length of said shaft.

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Description

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is directed generally to screws for orthopedic use in humans, and specifically to screws made of cortical bone and method of manufacture thereof.

2. Description of the Related Art

The mammalian skeleton includes dense structural bone known as cortical bone. In humans, the femur, one of the larger long bones of the body, may have a cortical thickness as great as 6 8 mm. Larger mammals, which have been used to provide bone for surgical use in humans, have bones with cortical thicknesses substantially greater than those found in humans.

Screws for orthopedic use may be used for a multitude of purposes, including to join separated bone portions, and to attach various orthopedic implants, such as skeletal plates, to bones. Such screws have commonly been made of surgical quality metals (e.g. stainless steel, surgical grade titanium, and titanium alloys), ceramics and various plastics including some that are bioresorbable.

Metal screws typically remain in the body unless explanted by a later, separate operative procedure, and can inter alia potentially irritate tissue proximate the metal screws, shed ions harmful to the body, back-out or loosen causing injury within the body. Metal screws also can interfere with optimal visualization of the affected area by various diagnostic modalities such as x-rays, CAT scans or MRIs. On the other hand, resorbable screws made of bioresorbable plastic materials which can be absorbed by the body over time have had both limited applicability and success. Resorbable plastic screws have often been limited by insufficient strength, an inability to be formed into a sharp thread-form, an unpredictable absorption rate, an inability to maintain sufficient structural integrity for an adequate period of time, the elicitation of an undesirable inflammatory response, and the potentially toxic effects of the degradation products of the material released by the bioresorption process.

There is therefore a need for a bone screw that combines the advantages of being sufficiently strong so as to be useful for skeletal fixation and for the attachment of various implants to the human skeleton, that additionally is resorbable within the body, and which does not have all the undesirable qualities encountered with screws of the past.

SUMMARY OF THE INVENTION

In accordance with the present invention, as embodied and broadly described herein, there are provided bone screws made of cortical bone for orthopedic use in humans. In a preferred embodiment, the bone screw of the present invention is made substantially of cortical bone and comprises at least a partially threaded shaft that is substantially solid, a leading end for introduction of the screw, and an opposite trailing end. The trailing end is adapted to cooperatively engage an instrument for turning the screw. The trailing end further comprises a head configured so as not to be able to pass through the same opening and passageway of an implant, for example, that the threaded shaft portion of the screw is capable of passing through for the purpose of preventing the continuing advancement of the screw. The screw head may take the form of an enlargement having either a greater diameter or a greater maximum dimension than that of the outer diameter of the threaded shaft portion of the screw. In the alternative, the proximal shaft portion at the trailing end of the screw may have a thread pitch in which the thread crests are closer together than the thread crests proximate the leading end. In a further refinement of this alternative, it is possible for the outside diameter of the thread to remain constant over the length of the screw shaft and for the thread profile to change from a cancellous thread-form for engaging cancellous bone to a machine thread-form at the trailing end to lock the screw at or within an orthopedic implant or at the cortex of a recipient bone itself.

The present invention is directed to an orthopedic bone screw made substantially of cortical bone, which is preferably but not necessarily of human origin. The screw of the present invention is substantially solid throughout its shaft portion and has a head portion at its trailing end configured to resist the further forward advancement of the screw when the screw is threaded through an appropriately sized opening, such as an opening in an orthopedic implant.

While the present invention is not so limited, the preferred bone is human obtained from the diaphyseal region of one of the large tubular bones of the skeleton, such as the femur or from a portion of a generally intramembraneously formed substantially cortical bone, such as may be found in the skull.

The present invention is further directed to locks for locking bone screws to an implant as an element separate from the screw or as part of the screw itself. The locks preferably also are made of cortical bone for locking the screws to an implant. The present invention also includes the combination of screws and locks with an orthopedic implant which also is preferably made of cortical bone.

The accompanying drawings, which are incorporated in and constitute a part of this specification, are by way of example only and not limitation, and illustrate several embodiments of the invention, which together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side elevation view of a first embodiment of a bone screw, a screw lock in cross section both made of cortical bone, a partial cross section of an orthopedic implant, and a tool in fragmentary view for installing the bone screw and screw lock.

FIG. 1B is a top perspective view of the lock of FIG. 1A.

FIG. 1C is a top plan view of the screw head of the bone screw of FIG. 1A.

FIG. 1D is a side elevation view of another embodiment of the bone screw in accordance with the present invention.

FIG. 2A is a side elevation view of a second embodiment of two bone screws and a screw lock made of cortical bone in accordance with the present invention, and a partial cross section of an orthopedic implant.

FIG. 2B is a top plan view of the head of a bone screw in FIG. 2A.

FIG. 3A is a side elevation view of a third embodiment of two bone screws and a screw lock made of cortical bone, and a partial cross section of an orthopedic implant.

FIG. 3B is a top plan view of the screw lock of FIG. 3A.

FIG. 4 is a side elevation view of a fourth embodiment of two bone screws and a screw lock made of cortical bone, and a partial cross section of an orthopedic implant.

FIG. 5 is a side elevation view of a fifth embodiment of two bone screws and screw lock made of cortical bone, and a partial cross section of an orthopedic implant.

FIG. 6 is a sixth embodiment of a bone screw and a partial cross section of an orthopedic implant each made of cortical bone.

FIG. 7A is a side elevation view of a seventh embodiment of a bone screw and a partial cross section of an orthopedic implant lock made of cortical bone.

FIG. 7B is a top plan view of the trailing end of the screw in FIG. 7A.

FIGS. 8 10 are side elevation views of an eighth embodiment of a bone screw, and a screw lock made of cortical bone, and a partial cross section of an orthopedic implant.

FIG. 11 is a side elevation view of a ninth embodiment of a screw made of cortical bone.

FIG. 12 is a top plan view of the trailing end of the bone screw made of cortical bone shown in FIG. 11 with a locking insert therein.

FIG. 13 is perspective view of a locking insert of cortical bone for use with the bone screw shown in FIGS. 11 and 12.

FIGS. 14 and 15 are a side elevation view and an end view, respectively, of an instrument for inserting the bone screw of FIGS. 11 and 12.

FIG. 16 is a side elevation view in partial cross section of a segment of the human spine with a spinal fusion implant made of in partial cross section bone inserted between two adjacent vertebrae, bone screws of FIG. 5, and a screw lock being installed.

FIG. 17 is a side elevation view in partial cross section of a segment of the human spine with an orthopedic plate in cross section made of bone placed across a spinal disc in contact with the adjacent vertebral bodies and screws installed through the orthopedic plate and into the adjacent vertebral bodies.

FIG. 18 is a side elevation view of a fractured long bone with lag screws made of bone in accordance with the present invention installed along the fracture to rejoin the long bone.

FIG. 19 is a side elevation view of a long bone with segments illustrated in hidden line of cortical bone being removed from the diaphysis by making a longitudinal cut, the segments being used to form bone screws made of cortical bone in accordance with the present invention.

FIG. 20 is an enlarged fragmentary end view of FIG. 19.

FIG. 21 is a side elevation view of a tenth embodiment of a bone screw made of cortical bone removed from the diaphysis of a long bone in accordance with the present invention.

FIG. 22 is an end view of a segment of cortical bone removed from the diaphysis of a long bone by making a longitudinal cut as illustrated in FIG. 20.

FIG. 23 is a block diagram of the steps of manufacturing and packaging the bone screws of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The following description is intended to be representative only and not limiting and many variations can be anticipated according to these teachings, which are included within the scope of the present invention. Reference will now be made in detail to the preferred embodiments of this invention, examples of which are illustrated in the accompanying drawings.

FIGS. 1A 12, 18, 21, and 22 show various embodiments of screws made of cortical bone in accordance with the present invention generally referred to by the reference numerals 100 to 1100, respectively. Similar reference numbers will be used throughout the drawings to refer to similar portions of similar parts.

Screws 100 1100 are shown in use with partial segments of orthopedic implants generally referred to by the reference numerals 150 850. As used in this application, orthopedic implants 150 850 can include various types of orthopedic implants such as, but not limited to, skeletal plates and interbody spinal fusion implants. Orthopedic implants 150 850 are preferably made of resorbable (bioresorbable) materials such as, but not limited to, cortical bone, plastics, and composite plastics. Suitable plastics may include those comprising lactides, galactides, glycolide, capronlactone, trimethylene carbonate, dioxanone in various polymers and/or combinations. Implants 150 850 may also comprise any other material suitable for surgical implantation into the human body including various metals, ceramics, and non-resorbable plastics and composites.

Screws 100 1100 each have a shaft that is threaded at least in part preferably having a tip at its leading end and may have a screw head at its trailing end. The screw head may or may not be protuberant, but is adapted to prevent the forward movement of the screw once the head is fully engaged to the orthopedic implants 150 850 or an appropriate opening in a bone.

Screws 100 1100 may be further secured to the orthopedic implants 150 850 by locks that are preferably made of cortical bone and may also be made of resorbable materials.

FIGS. 1A 1C show a screw 100 with a shaft 102 having a leading end 104, a tip 106, and a trailing end 108 opposite leading end 104. Shaft 102 is configured to pass through an opening 140 in an implant 150 adapted to receive a bone screw. Shaft 102 has a thread 110 adapted to engage bone. Shaft 102 has a minor diameter and an outer diameter as measured from the peaks of threads 110 to the minor diameter. The turns of thread 110 are spaced apart by valleys preferably having rounded bottoms. As a result, thread 110 has a wide base. The preferred embodiments of the present invention have generally enlarged root diameters to increase their strength overall and to withstand the torques generated on insertion which may be further mitigated by the prior use of a tap. Further stress risers are avoided by avoiding sharp corners and unradiused edges. Further, it may be desirable to have the root diameter be generally increased nearer to the head end of the screws. Thread 110 preferably has a self-tapping first turn near tip 106.

As shown in FIG. 1D, in another embodiment screw 100' has a thread near tip 106' in the same configuration of thread 110 and has a thread portion 114 with a wider base such that the valleys between thread 114 are more rounded than the valleys between the portion of thread 110'. This results in a screw having a shaft 102' with wider root diameter proximate trailing end 108' for increased strength of screw 100'. Trailing end 108 preferably has a screw head 120 with an enlarged portion having a diameter greater than the outer diameter of the threaded portion of shaft 102 and greater than opening 140 in implant 150 so as to prevent passage therethrough.

As shown in FIGS. 1A and C, screw head 120 preferably has a cruciate recess 122 for receiving distal end 152 of screw driver 156. Bone screw 100 is prevented from backing out by screw lock 130 that threads into threaded portion 118 of opening 140 in implant 150. Screw lock 130 has a tool receiving recess 132 and opening 134 for engaging lock engagement end 154 of screw driver 156 for installing screw lock 130. Distal end 152 of screw driver 156 is preferably configured to pass through opening 134 when engagement end 154 cooperatively engages recess 132.

As shown in FIG. 1A, in use distal end 152 is moved into opening 140 and screw driver 156 is utilized to insert bone screw 100 by cooperatively engaging a cruciate recess 122 in bone screw head 120. Once screw 100 is inserted into opening 140, the enlarged portion of the head 120 is at least partially blocked from passing through implant 150 by a retaining flange 116. In a preferred embodiment, lock 130 is machined out of cortical bone and may best be harvested from portions of the calvarium as it is less curved than a long bone. Alternatively, lock 130 could also be machined out of a long bone. As with other screw locks shown herein, by way of example only and not limitation, the locks can alternatively be formed of a bioresorbable plastic. Screw lock 130 is preferably made of one cortical thickness, e.g., longitudinally along a long bone, rather than by cutting transversely across the bone.

Lock 130 is preferably circumferentially threaded with threads 136 as shown in FIG. 1B. When screw driver 156 is advanced to insert lock 130 into implant 150, threads 136 of lock 130 can be threaded into receiving threads 118 of implant 150. In this example, it can be appreciated that opening 140 need not be threaded along its entire depth. Lock 130 can be rigidly tightened against the unthreaded portion of opening 140, which acts as a stop, preventing any further movement of lock 130 into opening 140. By binding lock 130 to trailing wall 112 of implant 150, and making the lower surface of lock 130 concave, allowance is made for motion of screws 100 relative to implant 150. This allows the surgeon some freedom of choice in positioning screws 100 and in selecting the direction of the force vector to be generated relative to implant 150.

Alternatively, by any number of structural configurations, such as for example an interference fit between screw head 120 and implant opening 140, or by way of more deeply threading opening 140, or by flattening the top of the screws and making the circumferential perimeter flush to lock 130, or by allowing lock 130 to contact screw head 120, later motion of screw 100 can be prevented. Stated differently, while the present example shows how to allow for variability in the screw's placement and provides for later movement of the screw as might occur with settling, in the alternative, the path of screw 100 through implant 150 can be rather narrowly defined, and any angular motion of screw 100 relative to implant 150 can be prevented.

As shown in FIGS. 2A and 2B, bone screw 200 has a threaded shaft 202, a leading end 204, a tip 206, and an opposite trailing end 208. Shaft 202 has a thread 210 adapted to engage bone. Trailing end 208 has a screw head 220 having a slightly enlarged head portion. Head portion 220 has a dimension greater than the outer diameter of the thread portion 210 of shaft 202 and greater than opening 240 in the implant 250 so as to prevent passage therethrough. Screw head 220 has a hex-shaped perimeter 222 adapted to complimentary engage a hex socket driver for installing the screw. A screw lock 230 having a threaded shaft 236 and an enlarged head 238 is used to lock screws 200 to implant 250 and to prevent them from backing out. Screws 200 are preferably non-parallel to the longitudinal axis of implant 250, more preferably at an angle of between 25.degree. and 75.degree. relative to the implant longitudinal axis. Lock 230 includes a hexagonal tool receiving area 232 for rotatably inserting lock 230 in implant 250. Screws 200 are adapted to angle toward each other in the direction of the arrows in FIG. 2A.

As shown in FIGS. 3A and 3B, each one of bone screws 300 has a threaded shaft 302 having a leading end 304, a tip 306, and an opposite trailing end 308. Shaft 302 has a thread 310 for engaging bone. Trailing end 308 has a screw head 320 having an enlarged portion with a diameter greater than the outer diameter of the threaded portion of shaft 302 and greater than opening 340 in implant 350 so as to prevent passage therethrough. Screw head 320 has a cross slotted cruciate recess 322 similar to that shown in FIG. 1C for receiving end 152 of screw driver 156. Bone screw 300 is prevented from backing out by screw lock 330 that threads into threaded opening 318 of implant 350. The bone screw lock 330 has a tool receiving recess 332 for engaging end 352 of a screw driver for installing the screw lock 330. Screw lock 330 may also have cutaway portions 360 and 362 to permit the insertion of bone screws 300 into openings 340 while screw lock 330 is attached to implant 350 in an unlocked position. Screw lock 330 can be rotated to a locked position to cover at least a portion of screw heads 320 and lock bone screws 300 to implant 350.

FIG. 3A shows lock 330 in use, where it can be appreciated that head portion 320 of screw 300 is prevented from passing through implant 350 by a retaining flange 316 at the base of opening 340. It can also be appreciated that when lock 330 is fully tightened, a lower portion of the screw head can be tightened against implant 350 itself so as to, as previously described, allow for some convergent motion of the bone screws. FIG. 3B shows lock 330 having a hex well 332 therein, and opposed concave portions 360 and 362. It should be understood that various driver engaging structures are useful for the intended purpose are contemplated and within the scope of the present invention.

In a preferred embodiment, when lock 330 is one-quarter turn short of being fully tightened, openings 340 are open and unobstructed at lock 330 to permit bone screws 300 to be inserted therein. After screws 300 have been installed, lock 330 can be further tightened by turning it 90 degrees until the shaft of the lock 330 reaches the lower most internal threads 318, thereby allowing the locking screw to be solidly tightened to implant 350.

While screws 300 have freedom to move closer together, screws 300 cannot back out of implant 350 with lock 330 in place. As previously discussed, while this is considered preferable, implant 350 can be so constructed to prevent any angular freedom of screw 300 relative to implant 350. Further, implant 350 and lock 330 can be configured to cooperate to prevent any backward motion of screw head 320.

As shown in FIG. 4, screw 400 has a threaded shaft 402 having a leading end 404, a tip 406, and an opposite trailing end 408. As with all of the embodiments described herein, tip 406 may have various configurations and may or may not have cutting flutes. Such flutes may be useful when such screws are for insertion into cancellous bone. However, when the bone is dense, the use of a thread forming tap as could be made of an instrument quality metal would be preferable. The tap would cut the path for the screw to follow rather than have the screw be subjected to the forces that would be required to form thereafter.

Shaft 402 has a thread 410 for engaging bone. Trailing end 408 has a screw head 420 having an enlarged portion having a diameter greater than the outer diameter of the threaded portion of shaft 402 and greater than opening 440 in implant 450 so as to prevent passage therethrough. Bone screw 400 is prevented from backing out by screw lock 430. Lock 430 is in the form of a disc with a threaded side wall 462 capable of threadably engaging threads 464 within common opening 460. When screws 400 are locked to implant 450, screws 400 can be allowed some angular motion relative to implant 450. The screw lock 430 has a tool receiving recess for engaging the end of a screw driver for installing the screw lock 430. Screw lock 430 and implant 450 are preferably made of cortical bone.

Distal to heads 420 of screws 400 is a smooth shaft portion 458 of a lesser cross sectional dimension than opening 440 which, in combination with the available space within common opening 460 between screw head 420 and lock 430, allows for bone screw 400 to operate as a lag screw, but, nevertheless, be capable of some variability in its positioning and to still further be capable of some ability to move closer to implant 450.

FIG. 5 shows an alternative implant screw and lock arrangement for use with implant 550, or as with the lock and screw configuration of FIG. 4 with any of the other embodiments of the present invention as may be appropriate. To that end, it should be appreciated that the implants shown herein are by way of example only and without limitation to the various combinations and permutations of the various screw, lock, and implant configurations shown, as well as the substantial equivalent thereof which are within the scope of the present invention.

As shown in FIG. 5, screw 500 has a threaded shaft 502 having a leading end 504, a tip 506, and an opposite trailing end 508. Shaft 502 has a thread 510 for engaging bone. Trailing end 508 has a screw head 520 having an enlarged portion having a diameter greater than the outer diameter of the threaded portion of shaft 502 and greater than opening 540 in implant 550 so as to prevent passage therethrough. Screw head 520 is preferably adapted to cooperatively engage the end of screw driver. Bone screw 500 is prevented from backing out by screw lock 530 that has a shaft 536 that threads into internal threads 518 implant 550. As with other embodiments herein described, the screw lock 530 may have a tool receiving recess for engaging an end of a screw driver for installing screw lock 530. Screw 500 and lock 530 are preferably made of cortical bone as preferably is implant 500. The combination results in screw 500 having a precise and defined orientation that is further secured by lock 530 so that no angular deviation of the screw in the construct is allowed.

Lock 530 differs from lock 430 in that extending from head portion 520 is a threaded shaft 536 for threading into internal threads 518 between opposed openings 540 within common opening 560 of implant 550. Unlike the mechanism illustrated in FIG. 4 where cap 430 tightens against the internal implant wall rather than only pressing against the screw heads themselves, thereby permitting some motion, head 538 of lock 530 tightens against heads 520 of screws 500 which also differ from screws 400 in that the smooth proximal shaft portions 558 are adapted to form an interference fit with the passageway through implant 550 and to thereby in combination allow for the screws to have a precise trajectory and to further be rigidly locked to the implant. It should be appreciated then that FIGS. 4 and 5 each teach a structure by which an implant of the present invention can be constructed so as to either cause the screws passing therethrough to have a fixed trajectory or in the alternative, be capable of variable angle placement. Further taught is structure for permitting the present invention implants to either allow for, or to prevent post-deployment angular motion of the bone screws relative to the implant after the screws have been locked within the implant; or still further to allow for but one degree of freedom of the locked screws and that being only to allow for the settling, or the coming closer together of the adjacent vertebrae. Various ways for achieving each of these are shown herein and may be combined in various ways with various embodiments of the implants shown or their substa