AU2023314522A1 - Instrument set and tulip of the same - Google Patents

Abstract

The invention relates to an instrument set, having a tulip (10) extending along its longitudinal axis (X), a spinal implant having a pedicle screw and serving to couple a connecting rod along a transverse axis (Q) of the tulip, and a holding device (200) for temporarily holding the tulip in a holding state of the instrument set during an implant insertion procedure, wherein a transition from the holding state to a release state of the tulip and holding device, and vice versa, involves a rotational movement about an axis (A), wherein the axis (A) runs with a predominant directional component transverse to the longitudinal axis and parallel to the transverse axis of the tulip.

Description

LZ-141 WO 2024/022642 PCT/EP2023/063961

INSTRUMENT SET AND TULIP OF THE SAME

The present invention relates to the field of spinal implants, in particular such

implant systems that include pedicle screws, several of which are interconnected via a

connecting rod or a fixing rod to stabilize the spine. In particular, the invention relates

to an instrument set comprising a tulip that extends along its longitudinal axis, said tulip

forming part of a spinal implant that includes a pedicle screw and serves to connect a

connecting rod along a transverse axis of the tulip, and a holding device for temporarily

holding the tulip during an implantation process in a holding state of the instrument set,

wherein a transition from the holding state to a release state of the tulip and the holding

device, and vice versa, involves a rotational movement about an axis.

Implant systems of this kind are, of course, well known to a person skilled in the

art; for example, reference is made to US 2012/0041490 Al or EP 2 376 005 B1.

Holding systems of this kind in these and numerous other techniques which rely on

straight (purely tangential) grooves in the outer surfaces of the tulip walls, thereby

allowing a tangential sliding of a holding instrument but not a rotational screwing of a

holding instrument around the longitudinal axis of the tulip, have since been developed,

meaning that a holding state between a holding device and the tulip is achieved by

rotating the holding instrument about the longitudinal axis of the tulip. This is disclosed,

for example, in US 9,050,148 B2, which describes a groove that follows the cylindrical

outer side wall of the tulip circumferentially and is open to the side.

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The invention is based on the object of further improving an instrument set of

the kind referred to above, in particular against the background of combining ease of

operation with a reliable transition from release to the holding state.

This object is achieved by the invention through a development of the instrument

set of the kind referred to above, which is substantially characterized in that the axis

predominantly runs both transversely to the longitudinal axis and parallel to the

transverse axis of the tulip. In spherical coordinates, where the longitudinal axis of the

tulip is the z-axis and the transverse axis of the tulip is the x-axis, this therefore

corresponds to 4 > 450 and (p < 450. However, these angles are preferably closer to

900(0) and 00 ((p), preferably not deviating by more than 300 from these values, and

more preferably by no more than 200, in particular by no more than 100. In a preferred

embodiment, the axis of the rotational movement runs substantially parallel to the

transverse axis when the tulip and the holding instrument are in the holding state. The

axis of the rotational movement is a defined axis defined by the holding instrument and

fixed within the system of the holding instrument.

The solution according to the invention eliminates the need for the holding

instrument and tulip to be rotatable about the longitudinal axis of the tulip, ensuring a

reliable azimuthal alignment between the holding instrument and the tulip during the

transition.

Further advantageous embodiments are specified in the dependent claims.

LZ-141 WO 2024/022642 PCT/EP2023/063961

It is therefore preferably provided that during the transition of the instrument set,

a shift occurs between an anti-rotational lock that acts radially on the tulip with respect

to its longitudinal axis, preventing rotation of the holding device relative to the tulip

about its longitudinal axis, and a rotational lock that blocks the rotational movement

radially outwards with respect to the longitudinal axis of the tulip. The anti-rotational

lock against rotation about the longitudinal axis of the tulip is therefore not only

achieved in the final holding state but is already present in an intermediate holding

state during the transition from the release state to the holding state. Due to the

rotational movement, the forces acting on the tulip during the closing movement are

largely balanced in terms of their tangential components, so that effectively radially

inwardly directed forces are exerted.

It is further preferred that the transition of the instrument set includes, at least

near the holding state, a translational axial movement between the tulip and the holding

device along the longitudinal axis of the tulip. This increases the axial depth of the

rotational lock.

It is also preferably provided that, in the instrument set, the rotational movement

and the axial movement overlap at least temporarily during the transition. To this end,

a guide may be provided which is preferably achieved through complementary shapes,

such as suitable slopes or curves in the respective coupling areas, for example, on the

underside of a radial projection of the instrument and a radially inwardly upwards-facing

surface of the tulip.

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A tulip for an instrument set according to one of the aforementioned aspects is

also provided.

The tulip preferably has at least four coupling areas spaced azimuthally apart

from one another on the tulip side for coupling the holding device in the holding state.

These are preferably designed to be mutually axis-symmetrical with respect to the

transverse axis and, as a preferred variant, achieve the aforementioned force

distribution and compensation.

More preferably, a coupling area of the tulip has a notch with a particularly

concave base for forming the anti-rotational lock to prevent rotation of the instrument

about the longitudinal axis. "Concave" or "concave base shape" in this context does

not imply a perfectly mathematical concavity but rather distinguishes it from purely

straight (tangential) contours and oppositely curved convex base shapes. For example,

if a circle defines a curvature sign around a chord, concavity here means an averaged

opposite curvature over the course of the notch base.

The coupling area of the tulip preferably also includes a lower (proximal) axial

channel section adjoining the azimuthal notch, which forms the rotational lock region

of the rotational lock on the tulip side.

The tulip preferably has multiple upper axial channel sections opening into the

upper axial side of the tulip walls, which particularly communicate with the lower

channel sections and align with them. While the upper axial channel sections represent

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an inherently undesirable material weakening of the tulip walls, they are nevertheless

preferred for manufacturing reasons.

In one embodiment, the axial channel sections run linearly in cross section when

viewed orthogonally to the longitudinal axis and are preferably tangential to the

longitudinal axis. However, in another embodiment, these sections could also run

polygonally in this cross section. A variant is also preferred in which this a curved

trajectory, preferably with the center of the curvature located substantially in the center

of the tulip (i.e. at the point where the longitudinal axis intersects the cross-sectional

plane). This applies to both the lower and/or upper axial channel sections.

Furthermore, the tulip preferably has side walls of the azimuthal notches

pointing towards the distal axial end of the tulip, which include a planar surface section

lying in a radial plane or entirely located within a radial plane, in particular at the same

axial height. Preferably, one side wall of the tulip has at least two azimuthal notches of

this kind.

Even more preferably, the tulip has a side wall of the azimuthal notch pointing

towards the proximal axial end of the tulip that is formed as a ramp. The ramped design

facilitates the transition between rotational and translational movement and provides

the necessary clearance for introducing the component of the rotational lock on the

holding instrument side. In one embodiment, mutually facing planar surface sections

in the respective base of two azimuthal notches arranged in the same side wall are at

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an angle to one another that is different from zero, preferably an angle of at least 20

degrees.

In a further preferred embodiment, the tulip has a web area formed azimuthally

between two azimuthal notches located on one side wall of the tulip, in particular with

an azimuthal dimension decreasing radially outwards. The proportion of the axial

channel sections, as viewed in the circumferential direction, is preferably no more than

70% of the azimuthal area of the side wall, preferably no more than 65%, and in

particular no more than 60%. The azimuthal dimension of the web area at the web

base, i.e. at the radial height of the notch bases and the axial height of the proximal

notch side surface, is preferably at least 120, more preferably at least 180, and in

particular at least 240.

Two azimuthal notches arranged on different side walls can each have a planar

surface section running parallel to one another. Preferably, an azimuthal notch on one

side wall is arranged diametrically opposite an azimuthal notch on another side wall.

Preferably, the axial length of an axial end section of the tulip arranged distally

to the azimuthal notches and/or that of the axial channels does not exceed 1.6 times

the axial dimension of the notch base at its radially innermost point, more preferably

not 1.3 times that dimension, and in particular not 1.1 times that dimension. This

creates an axially compact design of the tulip. In relation to the latter two values, this

ratio preferably also applies to the axial dimension of the notch at its radially outermost

point.

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A method for manufacturing a tulip is also provided, in which the lower axial

channel section is formed after the upper channel section, and the lower channel

section is formed in particular before the azimuthal notch. This sequence reduces the

risk of damage to the often delicate side walls of the tulip. The holding instrument

preferably has two legs that can pivot by rotation about the axis of the rotational

movement, with coupling areas of the holding instrument formed on the radial inner

side of each leg, matching the number of coupling areas on the tulip. These coupling

areas are preferably formed by a radial projection, onto which an axial projection is

flanged. The radial projection engages with the azimuthal notch of the tulip, while the

axial projection engages with the lower axial channel.

The legs of the holding instrument are preferably biased to achieve a release

position, for example by an elastic device. Furthermore, the holding instrument

preferably has a locking mechanism that allows it to be locked, against the bias, into a

closed state corresponding to the holding state of the instrument. It is evident that this

locking mechanism also forms a (primary) rotational lock to prevent a relative pivoting

of the legs away from one another. However, based on the findings of the present

invention, this rotational lock alone may not always be sufficient in certain cases,

meaning that the additional rotational lock provided by the coupling areas of the holding

instrument and the tulip offers extra security against an opening relative movement of

the legs of this kind.

Further details, features, and advantages of the invention will be apparent from

the following description with reference to the accompanying figures, in which:

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Fig. 1 shows an instrument set with a tulip of a spinal implant and a lower part

of a holding instrument,

Fig. 2 shows the instrument set from Fig. 1 on the left in an intermediate position

to reach the holding state, along with a detailed view, and on the right in the holding

state,

Fig. 3 shows the spinal implant from Fig. 1 along with an enlarged partial view

of the upper section with the tulip,

Fig. 4 shows a side view of the spinal implant along with two radial cross

sectional views at different axial heights,

Fig. 5 shows a similar view to Fig. 4 of another embodiment,

Fig. 6 shows a similar view to Fig. 4 of yet another embodiment,

Fig. 7 shows the entire holding instrument from Fig. 1 in a perspective view, in

an open state, and

Fig. 8 shows this holding instrument in a closed state corresponding to the

holding state depicted on the right in Fig. 2.

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The basic functionality of the spinal implant 100 shown in Fig. 1 will be well

known to a person skilled in the art. It comprises a bone anchor in the form of a pedicle

screw 30 which is mounted in the head of the implant 100, commonly referred to as

the tulip 10, in a pivoting manner, particularly in a polyaxially pivoting manner, relative

to the longitudinal axis X of the tulip 10. The fundamental structure of the tulip 10 is

also typical and well understood by a person skilled in the art. In addition to a receiving

area in the lower section for accommodating the (concealed) head of the pedicle screw

30, the tulip has an upper, cylindrical peripheral area from the basic outer shape to

form a receiving groove running in the transverse direction Q for accommodating a

connecting rod (not shown) that can be used to couple one pedicle screw to another.

In the upper section, two side walls 11a, 11b of the tulip 10 therefore remain,

with threads on their inner sides for receiving a set screw (also not shown), such as a

grub screw, with which the connecting rod can be fixed relative to the tulip 10.

Tightening the set screw also fixes the position of the pedicle screw 30 relative to the

tulip 10, not by direct force transmission from the connecting rod onto the screw head,

but rather through indirect force transmission by means of an intermediate component

commonly referred to as a saddle 20. The saddle 20 at least partially accommodates

the screw head in its lower section and is shaped on its upper side to fit the connecting

rod running along the transverse direction Q.

It is understood that the invention is not limited in terms of the numerous design

possibilities of the basic functionality described thus far, such as the specific designs

of the saddle 20, the internal structure of the tulip 10, monoaxiality or polyaxiality,

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symmetry or asymmetry of the angular ranges available for pivoting relative to the

longitudinal axis (axial axis) X, the material selection for the implant, the thread design

of the pedicle screw 30, and/or any additional functionalities.

To hold the tulip 10 during the implantation of the spinal implant 100, in particular

in minimally invasive procedures, a holding instrument 200 is provided. As is more

clearly visible in the holding state shown on the right in Fig. 2 between the instrument

200 and the tulip 10, the holding instrument 200 has two legs, 211a and 211b, which

are each coupled to one of the side walls, 11a and 11b, respectively. Although the

transition from a release state to this holding state involves a rotational movement

about an axis, this axis does not correspond to the traditional rotational axis, which in

the prior art is aligned with the longitudinal axis X of the tulip. Instead, the axis A of the

rotational movement runs in the transverse direction Q. The instrument is therefore not

rotated about the axial axis X relative to the tulip; instead, the coupling movement

involves a pivoting motion of the legs 211a and 211b towards each other, induced by

the rotational movement, with a corresponding approach to the tulip 10 in a

predominantly radial direction relative to the axial axis X and orthogonal to the axis A

of the rotational movement which is fixed in the coordinate system of the instrument.

The tulip-side coupling regions 12a and 12b on the side walls 11a and 11b are

designed identically on both sides in this exemplary embodiment, meaning that the

following description focuses on one side only. As can be seen most clearly in Fig. 3,

near its upper axial end, the tulip 10 has concavely shaped cuts 12a that serve as

coupling regions. These cuts do not follow the circumferential direction of the convex,

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substantially cylindrical side wall 11a, but instead act as a rotational lock for the

instrument-side counter-coupling parts, preventing the instrument 200 from rotating

relative to the tulip 10 about its longitudinal axis X. The counterparts on the instrument

are thereby prevented, even in an intermediate holding state before reaching the final

holding state, from entering or leaving the concave, notch-like coupling regions 12a

due to rotational force. This is best seen in the radial cross-sectional view A-A in Fig.

4.

The concave, notch-like coupling region 12a, hereinafter referred to simply as

the notch 12a, comprises, in terminology relating to the radial direction of the axial axis

X, a base surface 120, a first side surface 121, and a second side surface 122. The

first side surface 121 follows the course of the base surface 120 on its adjoining side

and transitions to the convex side wall 11a at its opposite edge. However, it does not

lie in the radial plane, but its normal vector, which does not necessarily remain constant

along the course of the first side surface 121, exhibits a directional component pointing

radially outwards, especially near the base surface 120.

In contrast, the second side surface 122 in this exemplary embodiment is formed

in a substantially planar manner and therefore extends in a radial plane with respect to

the axial axis X. The axial distance between the second side surface 122 and the first

side surface 121 is therefore in any event greater at the azimuthal midpoint transition

to the convex outer surface of the side wall 11a than on the base side. In the

embodiment shown in Figures 1 to 4, it is especially provided that this axial distance

increases from radially inwards to radially outwards and also azimuthally from the outer

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edges towards the azimuthal midpoint of the notch 12a. The notches 12a are spaced

apart azimuthally with their azimuthal midpoints separated by approximately 600 in this

exemplary embodiment.

The two notches 12a in this exemplary embodiment are separated by a ridge

14a. Due to the concave shape of the base surface 120 of the notches 12a, the ridge

14a has a substantially trapezoidal, almost triangular shape in the radial cross section,

so with a significantly larger azimuthal dimension radially inwards compared with

radially outward which is 300 in this exemplary embodiment. This shape is specifically

intended to provide greater material stiffness to compensate for material weakening in

the tulip wall 11a within the region in the axial direction X between the notches 12a and

the upper axial end of the tulip 10, as can be seen most clearly in Figures 3 and, in

particular, in the radial cross section B-B in Fig. 4.

Hence, the tulip 10 in this region 16a has two bores 18a running in the axial

direction X, which are configured as slots in the azimuthal direction. Their azimuthal

extent covers only a portion, in this embodiment approximately half the azimuthal

extent of the notches 12a. The inner wall of the slot in the radial direction aligns axially,

substantially with the base surface 120 of the notch 12a. In the slot 18a, an axial

projection 218a is accommodated in the holding state, which is not visible in Fig. 1 or

Fig. 2 due to being obscured by the instrument leg 211a. However, the axial projection

218b mounted on the radial projection 212b, as seen in Fig. 1, is visible in Fig. 7 and

is designed to fit into the slot 18b in the opposite side wall 11b. The radially outer

boundary of the slot 18a (18b) therefore forms a rotational lock in the holding state,

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preventing the leg 211a from pivoting about the axis A of the rotational movement of

the instrument 200.

The slots 18a, 18b are closed on both azimuthal sides. In this embodiment, the

ratio of the material area of the tulip that is not occupied by the slots 18a, 18b and

therefore remains part of the tulip, to the total azimuthal extent of the side wall 11a of

the tulip in the radial region of the slots 18a, 18b is approximately 50%.

In the embodiment shown in Fig. 5, the slots 18a, 18b are not concentric as in

the embodiment in Fig. 4 but are instead tangential, meaning that the slots are straight

in design. In the embodiment depicted in Fig. 6, three slots per side wall 11a, 1lb are

provided, in this case with a concentric arrangement similar to the embodiment in Fig.

4. However, these slots can also be designed straight (tangential), as in the

embodiment in Fig. 5, in another embodiment that is not depicted.

As illustrated in Fig. 2, the holding state shown on the right side in Fig. 2 is

achieved in that the legs 211a, 211b, by executing the pivoting motion about the axis

A, bring the radial projections 212a and 212b, protruding radially inwards from the inner

sides of the legs 211a and 211b, predominantly radially into the notches 12a and 12b

facing them. The final holding state is achieved by an axial translational movement

between instrument 200 and tulip 10, during which the rotational movement about the

axis A and this translational movement can already overlap. In the exemplary

embodiments shown in the figures, the first side surface 121 and the lower surface of

the radial projection 212a, b facing this side surface 121 form a guide that supports

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and, in particular, can also generate where required a translational axial movement of

this kind out of the rotational movement. Correspondingly, when releasing instrument

200 and tulip 10, a translational axial movement along the longitudinal axis X of the

tulip can be initiated, and the rotational movement can be guided or initiated by this

guide.

In Figures 7 and 8, the holding instrument 200 is shown again in its entirety. In

the open state depicted in Fig. 7, the legs 211a and 211b are pivoted relative to each

other out of their parallel base configuration (Fig. 8) in the holding state. A sliding switch

230, positioned on an extension of leg 211b beyond axis A, can maintain the holding

state (Fig. 8) against the restoring force of a spring mechanism 240. However, in the

holding state of the tulip, the locking mechanism of the switch 230 is no longer stressed

by forces acting on the free ends of the legs 211a and 211b, particularly those directed

radially outwards, as these forces are absorbed by the rotational lock formed by the

coupling areas of the tulip 10.

The inner channel 250 formed between the legs 211a and 211b extends to the

distal end, allowing an internally guided stamp (not shown) to be guided within the

instrument to press the connecting rod (also called a fixation rod) explained above into

the tulip. The free space in the transverse direction between the legs 211a and 211b

of instrument 200 is also of sufficient dimensions for this purpose. This internally guided

stamp can also be made hollow inside to permit the axial introduction of an additional

instrument part therein, in which case a set screw (not depicted) can be screwed into

the thread on the inner side of the tulip walls 11a and 11b. Likewise, a screwing

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instrument 200 (not depicted) could be guided within the instrument 200 to insert the

pedicle screw 30 into a vertebra while the tulip 10 is held by the instrument. In the case

of configurations with a saddle 20, said saddle includes an access opening that

provides access to the screw head of the pedicle screw 30 for this purpose.

It is understood that the holding instrument can also perform additional functions

familiar to a person skilled in the art in connection with the insertion of pedicle screws

and holding of the tulips in spinal implants of this kind. To this extent, details of the

exemplary embodiments explained above are not to be considered limiting for the

invention. Instead, the features of the above description and also the following claims

may be essential, individually or in combination, for realizing the invention in its various

embodiments.

Claims (13)

LZ-141 WO 2024/022642 PCT/EP2023/063961 Claims

1. An instrument set (10, 200) comprising a tulip (10) that extends along its

longitudinal axis (X), said tulip forming part of a spinal implant (100) that includes a

pedicle screw (30) and serves to connect a connecting rod along a transverse axis (Q)

of the tulip (10), and a holding device (200) for temporarily holding the tulip (10) during

the implantation process in a holding state of the instrument set, wherein a transition

from the holding state to a release state of the tulip (10) and the holding device (200),

and vice versa, involves a rotational movement about an axis (A),

characterized in that the axis (A) predominantly runs transversely to the

longitudinal axis (X) and parallel to the transverse axis (Q) of the tulip.

2. The instrument set as claimed in claim 1, wherein during the transition, a

shift occurs between an anti-rotational lock (12, 212) that acts radially on the tulip with

respect to its longitudinal axis (X), preventing rotation of the holding device (200)

relative to the tulip (10) about the longitudinal axis (X), and a rotational lock (18, 218)

that blocks the rotational movement radially outwards with respect to the longitudinal

axis of the tulip.

3. The instrument set as claimed in claim 1 or 2, wherein the transition, at

least near the holding state, includes a translational axial movement between the tulip

and the holding device along the longitudinal axis of the tulip.

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4. The instrument set as claimed in claim 3, wherein the rotational

movement and axial movement overlap at least temporarily during the transition.

5. A tulip for an instrument set as claimed in any one of the preceding

claims.

6. The tulip as claimed in claim 5, comprising at least four coupling areas

(12, 18) spaced azimuthally apart from one another on the tulip side for coupling the

holding device in the holding state.

7. The tulip as claimed in claim 6, wherein a coupling area has a notch with

a particularly concave base (120) for forming the anti-rotational lock to prevent rotation

of the instrument about the longitudinal axis.

8. The tulip as claimed in claim 6 or 7, wherein the coupling area includes a

lower axial channel section (18) adjoining the azimuthal notch, which forms the

rotational lock region of the rotational lock on the tulip side.

9. The tulip as claimed in any one of claims 5 to 8, having multiple upper

axial channel sections (18) opening into the upper distal axial side of the side walls of

the tulip, which preferably communicate with the lower channel sections and, in

particular, align with them.

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10. The tulip as claimed in any one of claims 7 to 9, wherein the side walls

(122) of the azimuthal notches pointing towards the distal axial end of the tulip lie

substantially within a radial plane, in particular at the same axial height.

11. The tulip as claimed in any one of claims 7 to 10, wherein a side wall

(121) of the azimuthal notch pointing towards the proximal axial end of the tulip is

formed as a ramp.

12. The tulip as claimed in any one of claims 6 to 11, comprising a ridge area

formed azimuthally between two azimuthal notches formed on one side wall of the tulip,

in particular with an azimuthal dimension decreasing radially outwards.

13. A manufacturing method of a tulip formed as claimed in any one of claims

5 to 12, wherein the lower axial channel section is formed after the upper channel

section is formed, and wherein the lower channel section is preferably formed

particularly before the azimuthal notch is formed and, in particular, before the side walls

of the tulip are formed by removing the material area located between the side walls.

218b

100

10 20 Ma 30

Fig. 1

A 2116

24a Detail

11b Detail

Ma 10 212b

Fig. 2

18a 18a 186 122 Detail Aba

12a 7 10 12b 14a 12a 121

120 Detail

Fig. 3

16a 18a B A A B A +

Ma B-B

14a 10 12a +

A-A 12b

Fig. 4

B BA A +

B-B

+

A-A

Fig. 5

T B BA A +

B-B

+

A-A

Fig. 6

218b

Fig. 7

Fig. 8