阅读说明：本技术 具有3d打印组件的椎弓根螺钉组合件 (Pedicle screw assembly with 3D printing component ) 是由 W·A·雷扎切 J·M·梅 于 2019-10-21 设计创作，主要内容包括：提供了一种骨紧固件组合件,所述骨紧固件组合件包含骨螺钉、收纳器、冠部、第一保持环和第二保持环。所述冠部收纳在所述收纳器的内腔中,并且所述第一保持环被设置成将所述冠部保持在所述收纳器中。头部分的至少一部分收纳在所述收纳器的所述内腔中,并且所述第二保持环被设置成将所述头部分的至少一部分保持在所述收纳器中。所述冠部、所述第一保持环和/或所述第二保持环可以使用提供较高表面光洁度(Ra)的3D打印工艺来制造。(A bone fastener assembly is provided that includes a bone screw, a receiver, a crown, a first retaining ring, and a second retaining ring. The crown is received in the inner cavity of the receiver and the first retaining ring is configured to retain the crown in the receiver. At least a portion of the head portion is received in the inner cavity of the receiver, and the second retaining ring is configured to retain at least a portion of the head portion in the receiver. The crown, the first retaining ring, and/or the second retaining ring may be manufactured using a 3D printing process that provides a relatively high surface finish (Ra).)

1. A bone fastener assembly, comprising:

a bone screw comprising a head portion, a threaded shaft portion, and a central axis, the head portion comprising an outer surface;

a receiver including a body portion having a first end, an opposing second end, and an inner surface defining a first cavity extending between the first end and the second end, a first arm portion including a first inner arm surface and a second arm portion including a second inner arm surface, the first and second inner arm surfaces defining a second cavity therebetween, the first and second cavities communicating with one another;

a crown including a first end, an opposing second end, an outer surface, and an inner surface defining at least a first interior cavity portion extending from the first end of the crown to a location intermediate the first end and the second end of the crown; and

a retaining ring having an annular shape and comprising a generally cylindrical outer surface and an upwardly facing surface;

wherein, when the bone fastener assembly is assembled,

at least a portion of the crown is positioned within the first cavity of the receptacle at a location at and near the second end of the body portion,

the retaining ring is positioned within the first cavity of the receiver at a location between the crown and the first end of the body portion,

at least a portion of the head portion is receivable between the crown and the retaining ring, and

said outer surface said head portion being in contact with said upwardly facing surface of said retaining ring, and

wherein the retaining ring is manufactured using a 3D printing process that results in an Ra (surface finish) of at least the upward facing surface of the retaining ring in a range of about 0.8 μm (32 μ in) to about 3.2 μm (125 μ in).

2. The bone fastener assembly of claim 1, wherein the outer surface of the head portion is substantially spherical and the upwardly facing surface of the retaining ring is substantially frustoconical.

3. The bone fastener assembly of claim 1, wherein the outer surface of the head portion is in contact with the inner surface of the crown when the bone fastener assembly is assembled, and wherein the crown is manufactured using a 3D printing process that results in a Ra (surface finish) of at least the inner surface of the crown in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

4. The bone fastener assembly of claim 3, wherein the receptacle is manufactured using a 3D printing process that results in an Ra (surface finish) of at least the inner surface of the receptacle in a range of about 0.8 μm (32 μ in) to about 3.2 μm (125 μ in).

5. The bone fastener assembly of claim 1, wherein the inner surface of the receptacle includes a first recess for receiving the retaining ring therein, and the receptacle is manufactured using a 3D printing process that results in a Ra (surface finish) of at least the inner surface of the receptacle in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

6. The bone fastener assembly of claim 1, wherein the 3D printing process is a first 3D printing process, and the assembly further comprises an expansion ring having an annular shape and including a substantially cylindrical outer surface and a substantially cylindrical inner surface, and wherein the expansion ring is manufactured using a second 3D printing process having an Ra (surface finish) in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η), and the inner surface of the receptacle includes a second recess for receiving the expansion ring therein.

7. The bone fastener assembly of claim 6, wherein at least a portion of the crown is in contact with the expansion ring when the bone fastener assembly is assembled, and wherein the crown is manufactured using a third 3D printing process that results in a Ra (surface finish) in a range of about 0.8 μm (32 μ in) to about 3.2 μm (125 μ in).

8. A bone fastener assembly, comprising:

a bone screw comprising a head portion, a threaded shaft portion, and a central axis, the head portion comprising an outer surface;

a receiver including a body portion having a first end, an opposing second end, and an inner surface defining a first cavity extending between the first end and the second end, a first arm portion including a first inner arm surface and a second arm portion including a second inner arm surface, the first and second inner arm surfaces defining a second cavity therebetween, the first and second cavities communicating with one another;

a crown including a first end, an opposing second end, an outer surface, and an inner surface defining at least a first interior cavity portion extending from the first end of the crown to a location intermediate the first end and the second end of the crown;

a retaining ring having an annular shape and comprising a generally cylindrical outer surface and an upwardly facing surface; and

an expansion ring having an annular shape and comprising a generally cylindrical outer surface and a generally cylindrical inner surface;

wherein, when the bone fastener assembly is assembled,

the retaining ring is positioned within the first cavity of the receiver at a location between the crown and the first end of the body portion,

the expansion ring is positioned within the first cavity of the receiver at a location between the second end of the body portion and the retaining ring;

at least a portion of the crown is received within the expansion ring;

at least a portion of the head portion is receivable between the crown and the retaining ring, and

said outer surface said head portion being in contact with said upwardly facing surface of said retaining ring, and

wherein the retaining ring is manufactured using a 3D printing process that results in an Ra (surface finish) of at least the upward facing surface of the retaining ring in a range of about 0.8 μm (32 μ in) to about 3.2 μm (125 μ in).

9. The bone fastener assembly of claim 8, wherein the outer surface of the head portion is substantially spherical and the upwardly facing surface of the retaining ring is substantially frustoconical.

10. The bone fastener assembly of claim 8, wherein the outer surface of the head portion is in contact with the inner surface of the crown when the bone fastener assembly is assembled, and wherein the crown is manufactured using a 3D printing process that results in a Ra (surface finish) of at least the inner surface of the crown in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

11. The bone fastener assembly of claim 10, wherein the 3D printing process is a first 3D printing process and the receptacle is manufactured using a second 3D printing process that results in an Ra (surface finish) of at least the inner surface of the receptacle in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

12. The bone fastener assembly of claim 8, wherein the inner surface of the receiver includes a first recess for receiving the retaining ring therein, and the receiver is manufactured using a 3D printing process that results in an Ra (surface finish) at least in the range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

13. The bone fastener assembly of claim 12, wherein the 3D printing process is a first 3D printing process, the inner surface of the receptacle includes a second recess for receiving the expansion ring therein, and the expansion ring is manufactured using a second 3D printing process that has an Ra (surface finish) in a range of about 0.8 μ ι η (32 μ in) to about 3.2 μ ι η.

14. The bone fastener assembly of claim 13, wherein the 3D printing process is a first 3D printing process and the crown is manufactured using a 3D printing process that results in a Ra (surface finish) in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

15. A bone fastener assembly, comprising:

a bone screw comprising a head portion, a threaded shaft portion, and a central axis, the head portion comprising an outer surface;

a receiver including a body portion having a first end, an opposing second end, and an inner surface defining a first cavity extending between the first end and the second end, a first arm portion including a first inner arm surface and a second arm portion including a second inner arm surface, the first and second inner arm surfaces defining a second cavity therebetween, the first and second cavities communicating with one another; and

a retaining ring having an annular shape and comprising a generally cylindrical outer surface and an upwardly facing surface;

wherein, when the bone fastener assembly is assembled,

the retaining ring is positioned within the first cavity of the receiver at a location between the first end and the second end of the body portion,

at least a portion of the head portion is receivable between the retaining ring and the second end of the body portion, and

said outer surface said head portion being in contact with said upwardly facing surface of said retaining ring, and

wherein the retaining ring is manufactured using a 3D printing process that results in an Ra (surface finish) of at least the upward facing surface of the retaining ring in a range of about 0.8 μm (32 μ in) to about 3.2 μm (125 μ in).

16. The bone fastener assembly of claim 15, wherein the outer surface of the head portion is substantially spherical and the upwardly facing surface of the retaining ring is substantially frustoconical.

17. The bone fastener assembly of claim 16, further comprising a crown including a first end, an opposing second end, an outer surface, and an inner surface defining at least a first inner cavity portion extending from the first end of the crown to a location intermediate the first and second ends of the crown, wherein at least a portion of the crown is positioned within the first cavity of the receiver at a location at and near the second end of the body portion, and the at least a portion of the head portion is receivable between the crown and the retaining ring.

18. The bone fastener assembly of claim 17, wherein the outer surface of the head portion is in contact with the inner surface of the crown portion when the bone fastener assembly is assembled, wherein the 3D printing process is a first 3D printing process, and wherein the crown portion is manufactured using a second 3D printing process that results in an Ra (surface finish) of at least the inner surface of the crown portion in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

19. The bone fastener assembly of claim 18, wherein the receptacle is manufactured using a 3D printing process that results in an Ra (surface finish) of at least the inner surface of the receptacle in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

20. The bone fastener assembly of claim 15, wherein the inner surface of the receptacle includes a first recess for receiving the retaining ring therein, and the receptacle is manufactured using a 3D printing process that results in a Ra (surface finish) of at least the inner surface of the receptacle in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

Technical Field

The present technology relates generally to pedicle screw assemblies having 3D printed components.

Background

Pedicle screw assemblies are used to facilitate placement and attachment of spinal rods with respect to the spine. Spinal rods may be used to correct spinal deformities. Typically, such pedicle screw assemblies include at least a bone screw portion and a receiver portion attached to each other. The bone screw portion is attached to a vertebra, and the receiver portion receives a portion of the spinal rod.

In addition, the receiver portion of a typical pedicle screw assembly is angled relative to the screw portion and may be fixedly positioned to provide attachment of the spinal rod between vertebrae. The configuration of pedicle screw assemblies often involves conflicting tradeoffs. For example, the strength of the receiver portion to the truncation of the bone screw portion and the maximum angle of the receiver portion to the bone screw portion are conflicting tradeoffs. Generally, as the maximum angle of the receiver portion relative to the bone screw portion increases, the truncation strength decreases. Accordingly, there is a need for a manufacturing technique that can alleviate this situation and increase other performance characteristics of pedicle screw assemblies.

Disclosure of Invention

The technology of the present disclosure generally relates to one or more 3D printed components that may be used in fastener assemblies including pedicle screw assemblies.

In one aspect, the present disclosure provides a bone fastener assembly including a bone screw including a head portion, a threaded shaft portion, and a central axis, the head portion including an outer surface; a receiver including a body portion having a first end, an opposing second end, and an inner surface defining a first cavity extending between the first end and the second end, a first arm portion including a first inner arm surface and a second arm portion including a second inner arm surface, the first and second inner arm surfaces defining a second cavity therebetween, the first and second cavities communicating with one another; a crown including a first end, an opposing second end, an outer surface, and an inner surface defining at least a first inner cavity portion extending from the first end of the crown to a location intermediate the first and second ends of the crown and a retaining ring having an annular shape and including a generally cylindrical outer surface and an upwardly facing surface; wherein when the bone fastener assembly is assembled, at least a portion of the crown is positioned within the first cavity of the receptacle at a location at and near the second end of the body portion, the retaining ring is positioned within the first cavity of the receptacle at a location between the crown and the first end of the body portion, at least a portion of the head portion is receivable between the crown and the retaining ring, and the outer surface the head portion is in contact with the upwardly facing surface of the retaining ring, and wherein the retaining ring is manufactured using a 3D printing process that results in an Ra (surface finish) of at least the upwardly facing surface of the retaining ring in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

In another aspect, the present disclosure provides a bone fastener assembly including a bone screw including a head portion, a threaded shaft portion, and a central axis, the head portion including an outer surface; a receiver including a body portion having a first end, an opposing second end, and an inner surface defining a first cavity extending between the first end and the second end, a first arm portion including a first inner arm surface and a second arm portion including a second inner arm surface, the first and second inner arm surfaces defining a second cavity therebetween, the first and second cavities communicating with one another; a crown including a first end, an opposing second end, an outer surface, and an inner surface defining at least a first inner cavity portion extending from the first end of the crown to a position retaining ring intermediate the first and second ends of the crown, the retaining ring having an annular shape and including a generally cylindrical outer surface and an upwardly facing surface; and an expansion ring having an annular shape and comprising a substantially cylindrical outer surface and a substantially cylindrical inner surface; wherein when the bone fastener assembly is assembled, the retaining ring is positioned within the first cavity of the receiver at a location between the crown and the first end of the body portion, the expansion ring is positioned within the first cavity of the receiver at a location between the second end of the body portion and the retaining ring; at least a portion of the crown is received within the expansion ring; at least a portion of the head portion is receivable between the crown and the retaining ring, and the outer surface the head portion is in contact with the upward facing surface of the retaining ring, and wherein the retaining ring is manufactured using a 3D printing process that results in an Ra (surface finish) of at least the upward facing surface of the retaining ring in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

In yet another aspect, the present disclosure provides a bone fastener assembly including a bone screw including a head portion, a threaded shaft portion, and a central axis, the head portion including an outer surface; a receiver including a body portion having a first end, an opposing second end, and an inner surface defining a first cavity extending between the first end and the second end, a first arm portion including a first inner arm surface and a second arm portion including a second inner arm surface, the first and second inner arm surfaces defining a second cavity therebetween, the first and second cavities communicating with one another; and a retaining ring having an annular shape and comprising a generally cylindrical outer surface and an upwardly facing surface; wherein when the bone fastener assembly is assembled, the retaining ring is positioned within the first cavity of the receiver at a location between the first end and the second end of the body portion, at least a portion of the head portion is receivable between the retaining ring and the second end of the body portion, and the outer surface the head portion is in contact with the upward facing surface of the retaining ring, and wherein the retaining ring is manufactured using a 30 print process that results in an Ra (surface finish) of at least the upward facing surface of the retaining ring in a range of about 0.8 μ ι η (32 μ ι η) to about 3.2 μ ι η (125 μ ι η).

The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.

Drawings

FIG. 1 is a top front perspective view showing an embodiment of a pedicle screw assembly;

FIG. 2 is a top front exploded perspective view showing the pedicle screw assembly of FIG. 1;

FIG. 3 is a first cross-sectional view showing an anterior elevation view of the pedicle screw assembly of FIG. 1; and is

Fig. 4 is an anterior elevation second cross-sectional view showing the pedicle screw assembly of fig. 1.

Detailed Description

A fastener assembly according to one embodiment of the present disclosure is generally indicated by numeral 10 in fig. 1-4. The fastener assembly 10 includes a screw 12, a receiver 14, a crown 16, a first expansion (or retaining) ring 18, and a second expansion (or retaining) ring 19. As discussed below, the fastener assembly 10 is used to facilitate attachment of spinal constructs, such as spinal rods S, to the spine. As discussed below, a portion of the spinal rod S is ultimately received within the receiver 14, and a threaded cap T engaging the receiver 14 is positioned over the portion of the spinal rod S to retain the portion of the spinal rod S within the receiver 14. The fastener assembly 10 is similar to the fastener assembly disclosed in U.S. patent No. 15/843,938, which is incorporated herein by reference in its entirety.

The screw 12 may be used to facilitate the secure attachment of the receiver 14 and crown 16 to tissue, such as bone. The screw 12 may be substantially identical to the screw disclosed in U.S. patent No. 15/843,938. The screws and screws 12 disclosed in us patent No. 15/843,938 may be pedicle screws.

Screw 12 includes head portion 20, neck portion 22, shaft portion 24 and central axis a 1. As depicted in fig. 1-3, head portion 20 is generally spherical, neck portion 22 engages shaft portion 24 to head portion 20, and shaft portion 24 is configured to penetrate tissue, e.g., bone. The shaft portion 24 may include one or more thread forms having continuous threads or discrete threads and/or different spacing to facilitate such bone penetration. As depicted in fig. 2 and 3, shaft portion 24 includes first thread form 30 and second thread form 32 having continuous threads and different pitches about shank 34. In addition to facilitating bone penetration, first and second thread forms 30, 32 also serve to secure screw 12, receiver 14, and crown 16 to bone. Further, the diameter of the shank 34 may be smaller or larger than the diameter of the neck portion 22, and may include portions having a tapered and/or cylindrical configuration.

Head portion 20 includes a tool engaging portion 36 configured to engage a surgical tool or instrument for rotating screw 12. The tool engaging portion 36 includes six (6) hornheads (lobes) arranged in a generally hexagonal cross-sectional configuration. In some embodiments, the tool engaging portion 36 may have, for example, alternative cross-sectional configurations, such as generally polygonal (including generally triangular, rectangular, hexagonal, etc. configurations), elliptical, or irregular.

Head portion 20 includes an outer surface 40, and as depicted in fig. 2 and 3, outer surface 40 is substantially spherical. The outer surface 40 includes a plurality of ridges 42 and a plurality of flats 44 disposed adjacent the tool engaging portion 36. Ridge 42 can be used to improve the grip of head section 20 with other surgical instruments. Further, in some embodiments, flattened portions 44 may be used to engage projections (not shown) in crown 16 to constrain movement of screw 12 relative to crown 16.

As depicted in fig. 1-3, the receiver 14 includes a body portion 50, a first arm 52 extending upwardly from the body portion 50, and a second arm 54 extending upwardly from the body portion 50. The receiver 14 includes a first cavity 56 and a second cavity 58. The first cavity 56 is located within the body portion 50 and extends between a first opening 60 and a second opening 62. A first opening 60 is provided at an end of the body portion 50 opposite the first and second arms 52, 54, and a second opening 62 is provided at a transition between the locations at which the first and second arms 52, 54 extend upwardly from the body portion 50. Further, a second cavity 58 is formed between the first arm 52 and the second arm 54.

As discussed below, in various embodiments, during an initial stage of assembly of the fastener assembly 10, the crown 16 is received in portions of the first and second cavities 56, 58, and then the crown is ultimately received in the first cavity 56 due to the use of the threaded cap T to retain the portion of the spinal rod S within the receiver 14 and the corresponding interaction of the portion of the spinal rod S with the crown 16. Moreover, in various embodiments, at least a portion of the head portion 20 and neck portion 22 are ultimately received in the first cavity 56, and the spinal rod S is ultimately received in the second cavity 58.

As depicted in fig. 2 and 3, the crown 16 includes a wall portion 70 having a first end 72 and a second end 74, a flange portion 76 extending outwardly from the second end 74 of the wall portion 70, and an internal cavity 78 extending through the wall portion 70 and the flange portion 76 between a first opening 80 formed at the first end 72 of the wall portion 70 and a second opening 82 formed through the flange portion 76. The wall portion 70 may be substantially cylindrical and include a first mating portion 84 and a second mating portion 86.

The flange portion 76 may be "saddle" shaped and may include a first end 90 having a first lip portion 92, a second end 94 having a second lip portion 96, and a recess 98 formed between the first and second ends 90, 94 and defined by first and second side surfaces 100, 102. The first side surface 100 and the second side surface 102 may each be generally U-shaped to provide the flange portion 76 with its "saddle" shape. Like second cavity 58, recess 98 is configured to receive the portion of spinal rod S therein. As discussed below, the first and second mating portions 84, 86 and the first and second lip portions 92, 94 may be configured to engage portions of the wall portion 70 in the internal cavity 78 to facilitate attachment of the crown 16 to the receiver 14 during an initial stage of assembly of the fastener assembly 10.

As depicted in fig. 3, the first cavity 56 formed in the body portion 50 is defined by an inner surface 104. The inner surface 104 may be generally cylindrical and sized to receive at least a portion of the crown 16 therein. The inner surface 104 includes a third mating portion 106 and a fourth mating portion 108 for engaging the first mating portion 84 and the second mating portion 86, respectively. One of the first and third mating portions 84, 106 may be a recess and the other of the first and third mating portions 84, 106 may be a projection; and one of the second mating segment 86 and the fourth mating segment 108 may be a recess and the other of the second mating segment 86 and the fourth mating segment 108 may be a projection. As depicted in fig. 3, the first and second mating portions 84, 86 are recesses, and the third and fourth mating portions 106, 108 are projections. The engagement of the first mating portion 84 with the third mating portion 106 and the engagement of the second mating portion 86 with the fourth mating portion 108 serve to attach the crown 16 to the receiver 14 in the initial position, as depicted in fig. 1 and 3.

As depicted in fig. 3, the second cavity 58 of the receptacle 14 is formed between the first arm 52 and the second arm 54 by a first inner surface 110 formed on the first arm 52 and a second inner surface 112 formed on the second arm 54. The first inner surface 110 includes a first recess 114 for receiving the first lip portion 92 of the first end 90 of the flange portion 76, and the second inner surface 112 includes a second recess 116 for receiving the second lip portion 96 of the second end 94 of the flange portion 76. The engagement of the first lip portion 92 with the first recess 114 and the second lip portion 96 with the second recess 116 in the second cavity 58 further serves to attach the crown 16 to the receiver 14 in the initial position, as depicted in fig. 1 and 3. Further, the second cavity 58 includes first and second threads 118A, 118B formed on the first and second inner surfaces 110, 112 of the first and second arms 52, 54, respectively, for engaging a threaded cap T for securing the portion of the spinal rod S received in the second cavity 58 relative to the fastener assembly 10.

With continued reference to fig. 3, the interior cavity 78 of the crown 16 includes a first portion 120 and a second portion 122. The first portion 120 extends from the first opening 80 to a location intermediate the first and second openings 80, 82, and the second portion 122 extends from the location intermediate the first and second openings 80, 82 to the second opening 82. The first portion 120 is sized to receive a portion of the head portion 20 of the screw 12 therein, and the second portion 122 is sized to receive a surgical tool or instrument (not shown) for engaging the tool engaging portion 36 when the screw 12 is received in the first portion 120. The first portion 120 is formed by an inner surface 124. As depicted in FIG. 3, inner surface 124 can be spherical or substantially spherical to facilitate engagement with the substantially spherical shape of outer surface 40 of head portion 20. As discussed below, the friction caused by the engagement of outer surface 40 (including ridges 42) with inner surface 124 serves to maintain the position of head section 20 relative to crown 16.

As depicted in fig. 2, the fastener assembly 10 is assembled in the following manner: the crown 16 is first inserted through the first opening 60 and into the first cavity 56, then the first expansion ring 18 is inserted through the first opening 60 and into the first cavity 56, and then the second expansion ring 19 is inserted through the first opening 60 and into the first cavity 56. As discussed below, the crown 16 and the first expansion ring 18 are first positioned in the receiver 14 in an initial position as depicted in fig. 3, and then, after a portion of the head portion 20 of the screw 12 is inserted into the receiver 14, when the threaded cap T pushes the portion of the surgical rod S against the crown 16 and correspondingly pushes the crown 16 against the head portion 20, and secondly, the crown 16 and the first expansion ring 18 are positioned in the receiver 14 in a final position as depicted in fig. 4.

The second expansion ring 19, in conjunction with the crown 16, serves to ultimately maintain the position of at least a portion of the head portion 20 in the first cavity 56. As discussed below, the first and second expansion rings 18, 19 are each formed in various embodiments as incomplete, generally annular structures that provide for expansion and contraction. Further, as depicted in fig. 4, the first expansion ring 18 is configured to ultimately assist in holding the crown 16 in place relative to the receiver 14 when the resulting assembly 10 is used, and in fig. 4, the second expansion ring 19 is configured to ultimately assist in holding the screw 12 in place relative to the crown 16 when the resulting assembly 10 is used.

As depicted in fig. 2, the first expansile loop 18 includes a first end 130, an opposing second end 132 and a bore 134 extending between the first end 130 and the second end 132. Further, the first expansion ring 18 is incomplete in various embodiments and includes a first circumferential end 140, a second circumferential end 142, and a gap 144 between the first and second circumferential ends 140, 142. As discussed above, the first expansion ring 18 defines the aperture 134 therethrough, and the first expansion ring 18 is received in the first recess 146 formed in the inner surface 104.

The first expansion ring 18 is compressible to reduce the size of the gap 144 and thus fits through the first cavity 56 and into the first recess 146. As depicted in fig. 2, first expansion ring 18 includes a substantially annular lower surface 150 at first end 130, a substantially annular upper surface 152 at second end 132, a substantially cylindrical outer surface 154, and a substantially cylindrical inner surface 156. As depicted in fig. 3, when the first expansion ring 18 is in the initial position, portions of the upper surface 152 and the outer surface 154 contact portions of the first recess 146, and portions of the inner surface 156 contact the wall portion 70 of the crown 16. Further, in its initial position, the first expanse 18 is in contact with the crown 16 and is used to maintain engagement of the first mating portion 84 with the third mating portion 106, engagement of the second mating portion 86 with the fourth mating portion 108, engagement of the first lip portion 92 with the first recess 114, and engagement of the second lip portion 96 with the second recess 116.

As depicted in fig. 2, the second expansile loop 19 includes a first end 170, an opposing second end 172 and a bore 174 extending between the first end 170 and the second end 172. In addition, the second expansion ring 19 is incomplete and includes a first circumferential end 180, a second circumferential end 182, and a gap 184 between the first and second circumferential ends 180, 182. As discussed above, the second expansion ring 19 defines the aperture 174 therethrough, and the second expansion ring 19 is received in the second recess 186 formed in the inner surface 104.

Second expansion ring 19 is expandable to increase the size of gap 184 and, thus, the size of aperture 174 to allow at least a portion of head section 20 to pass therethrough. After the crown 16 and the first expansion ring 18 are positioned within the receiver 14 in their initial positions and the second expansion ring 19 is positioned in the second recess 186, at least a portion of the screw head portion 20 may be inserted through the first opening 60, into the first cavity 56, and through the hole 174. Second expansion ring 19 expands to facilitate passage of at least a portion of head section 20 through aperture 174. If desired, second expansion ring 19 may be moved by head portion 20 from second recess 186 into third recess 210 formed between first recess 146 and second recess 186. The positioning of second expansion ring 19 in third recess 210 further increases the size of aperture 174 to pass at least a portion of head portion 20 therethrough. Second expansion loop 19 eventually contracts after at least a portion of head section 20 passes through the second expansion loop to facilitate capturing at least a portion of head section 20 between crown 16 and second expansion loop 19. As discussed below, the friction caused by the final engagement of head portion 20 with crown 16 and second expansion ring 19 serves to maintain the position of head portion 20 relative to crown 16.

As depicted in fig. 2, the second expansion ring 19 includes a substantially annular lower surface 190 at the first end 170, a substantially annular upper surface 192 at the second end 172, a substantially cylindrical outer surface 194, and a substantially cylindrical inner surface 196. Portions of the lower surface 190 and the outer surface 194 contact portions of the second recess 186, and portions of the inner surface 196 contact portions of the head portion 20.

To facilitate passage of at least a portion of head portion 20 through aperture 174, inner surface 196 of second expansion ring 19 may include a lower angled first surface 200 adjacent first end 170. As depicted in fig. 2, the lower angled first surface 200 may be a partial frustoconical shape. The configuration of the lower angled first surface 200 serves to assist in the expansion of the second expansile loop 19 as at least a portion of the head 20 passes thereby.

Further, to facilitate maintaining at least a portion of the head portion in position between crown 16 and second expansion ring 19, inner surface 196 of second expansion ring 19 may include an upper angled second surface 202 adjacent second end 172. As depicted in fig. 2, the upper angled second surface 202 may be a partial frustoconical shape.

The configuration of the inner surface 124 and the upper angled second surface 202 serves to maintain the screw 12 in a selected angular position relative to the receiver 14 and the crown 16 when the crown 16 and the first expansion ring 18 are positioned in the receiver 14 in the final position depicted in fig. 4. In other words, the friction caused by the interface formed by outer surface 40 (including ridges 42) on inner surface 124 and the friction caused by outer surface 40 on upper angled second surface 202 act to resist movement of head portion 20 (and the remainder of screw 12) relative to receiver 14 and crown 16. As such, this friction serves to maintain the selected position of the screw 12 relative to the receiver 14 and crown 16.

During use of the fastener assembly 10, the screw 12 may be attached to the bone before the receiver 14 and crown 16 are attached thereto, the receiver 14 and crown 16 may be attached to the screw before the screw 12 is attached to the bone, or the screw 12 may be initially attached to the bone, the receiver 14 and crown 16 may then be attached to the screw 12, and the screw 12 (to which the receiver 14 and crown 16 are attached) may be further attached to the bone.

To facilitate positioning the crown 16 in its initial position (fig. 3) relative to the receiver 14, the crown 16 is inserted through the first opening 60 into the first cavity 56 such that the first mating portion 84 engages the third mating portion 106, the second mating portion 86 engages the fourth mating portion 108, the first lip portion 92 engages the first recess 114, and the second lip portion 96 engages the second recess 116. To facilitate positioning of the first expansion ring 18 in its initial position relative to the receiver 14 (fig. 3), the first expansion ring 18 is thereafter inserted through the first opening 60 and into the first cavity 56 and positioned in the first recess 146 formed in the inner surface 104. After the crown 16 and the first expansion ring 18 are positioned in the initial position as depicted in fig. 3, the second expansion ring is inserted through the first opening 60 into the first cavity 56 and positioned in the second recess 186 formed in the inner surface 104.

To facilitate attachment of screw 12 to receiver 14 and crown 16, at least a portion of head portion 20 is inserted through first opening 60, into first cavity 56, and through hole 134 (with second expansion ring 19 expanded as needed to provide insertion therethrough). If desired, second expansion ring 19 is moved by head portion 20 from second recess 186 into third recess 210 to further increase the size of aperture 174.

After at least a portion of head portion 20 is received in first cavity 56 and the portion of surgical shaft S is positioned in second cavity 58 and in contact with crown 16 at first and second side surfaces 100 and 102 thereof, threads 208 of the threaded cap are threadedly engaged with first and second threads 118A and 118B. As depicted in fig. 4, when the threaded cap pushes the portion of the surgical rod S against the crown 16, the first mating portion 84, the second mating portion 86, the first lip portion 92, and the second lip portion 96 are released from their above-discussed engagement with the receiver 14, and the crown 16 moves downward within the receiver 14. This movement of crown 16 forces first expansion ring 18 from first recess 146 into third recess 210 and pushes inner surface 124 against outer surface 40 (containing ridges 42) and outer surface 40 against upper angled surface 202 to capture at least a portion of head portion 20 between crown 16 and second expansion ring 19. This movement forcing the outer surface 40 against the upper angled surface 202 pushes the second expansion ring 19 from the third recess 210 into the second recess 186 to collapse the second expansion ring 19 if the expansion ring 19 is positioned in the third recess 210. The first expansion ring 18 is configured to ultimately assist in holding the crown 16 in place relative to the receiver 14 by friction. In addition, friction between the screw 12 and the second expansion ring 19, as well as friction between the screw 12 and the crown 16, may be used to maintain the screw 14 in position relative to the rest of the fastener assembly 10.

Increasing the surface roughness of the components of the fastener assembly 10 may increase their performance characteristics, and for illustration, the following component interfaces of the fastener assembly 10 may benefit from such increased surface roughness. For example, increasing friction between the second expansion ring 19 and the screw 12 at the interface formed by the outer surface 40 of the head portion 20 on the upper angled second surface 202, increasing friction between the screw 12 and the crown 16 at the interface formed by the outer surface 40 (including the ridges 42) on the inner surface 124, increasing friction between the first expansion ring 18 and the receiver 14 at the interface of the first expansion ring 18 and the first recess 146, increasing friction between the second expansion ring 19 and the receiver 14 at the interface of the second expansion ring 19 and the second recess 186, and increasing friction between the crown 16 and the spinal rod S at the interface of the spinal rod S and the first and second side surfaces 100 and 102 may be beneficial to the fastener assembly 10. To this end, the crown 16, the first expansion ring 18 and/or the second expansion ring 19 may be manufactured by a 3D printing or additive manufacturing process. Printing the respective components may be referred to as separate processes-e.g., in the claims hereof-whether printing the shared steps or functions, and performed at the same or a close time and place.

To illustrate, the 3D printing process may create a rough surface during formation of the receiver 14, crown 16, first expansion ring 18, and/or second expansion ring 19, over that which could be created by other manufacturing processes, such as a media blasting process or a machining process. 3D printing can be used to optimize the surface characteristics of the components of the fastener assembly 10 by increasing Ra, which is the arithmetic mean of the roughness curves, to a range between about 0.8 μm (32 μ in) to about 3.2 μm (125 μ in). By providing the Ra range discussed above through 3D printing, the coefficient of friction between the components of the fastener assembly 10 can be correspondingly increased.

When interfacing with other similarly formed rough surfaces, rough surfaces produced by other manufacturing processes, and smooth surfaces, these rough surfaces manufactured using 3D printing provide a favorable Ra and increase in coefficient of friction, which provides a mechanical advantage that mitigates tradeoffs in the configuration of fastener assembly 10.

For purposes of illustration, the strength of the truncation of the receiver 14 relative to the screw 12 and the maximum angle of the receiver 14 relative to the screw 12 are conflicting tradeoffs. The strength of the truncated cone is obtained by pulling the receiver 14 out of the screw 12The required force and the maximum angle of the receiver 14 relative to the screw 12 is the axis A of the receiver 14₂Relative to the axis A of the screw 12₁The maximum angle of (c). Generally, as the maximum angle of the receiver 14 relative to the screw 12 increases, the truncated strength of the receiver 14 relative to the screw 12 decreases. Manufacturing, for example, second expansion ring 19 using 3D printing to create a roughened surface thereon may increase the coefficient of friction between upper angled surface 202 and head portion 20, and such friction may provide better mechanical properties to mitigate this tradeoff and increase both the truncated strength and the maximum angle. For example, the Ra of upper angled surface 202 may be in a range between about 0.8 μm (32 μ in) to about 3.2 μm (125 μ in), and such range may increase the Inner Diameter (ID) of second expanse 19 to increase such that axis A of receptacle 14 is increased₂Relative to the axis A of the screw 12₁May increase from about 25 to about 35.

Manufacturing using 3D printing may also increase other performance characteristics of the pedicle screw assembly. To illustrate, manufacturing the receiver 14, crown 16, first expansion ring 18, and/or second expansion ring 19 to have an Ra within the ranges discussed above using 3D printing may increase the coefficient of friction at the interface formed between the receiver 14 and crown 16, the coefficient of friction between the screw 12 and the crown 16 is increased at the interface formed by the outer surface 40 (including the ridges 42) on the inner surface 124, increasing the coefficient of friction between the first expansion ring 18 and the receiver 14 at the interface of the first expansion ring 18 and the first recess 146, increasing the coefficient of friction between the second expansion ring 19 and the receiver 14 at the interface of the second expansion ring 19 and the second recess 186 (to increase ball slip strength), and increasing the coefficient of friction between the crown 16 and the spinal rod S received in the recess 98 at the first and second side surfaces 100, 102 (to increase axial grip and torsional strength).

It should be understood that the various aspects disclosed herein may be combined in different combinations than those specifically presented in the description and drawings. It will also be understood that, depending on the example, certain acts or events of any process or method described herein can be performed in a different order, may be added, merged, or omitted altogether (e.g., all described acts or events may not be necessary for performing the techniques). Additionally, although certain aspects of the disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of the disclosure may be performed by a combination of units or modules associated with, for example, a medical device.