Patent Description:
Spine surgeons can use many types of systems for spinal fixation. A known growth-guiding system for instance comprises a rod coupled to one end of the spine, a connector slidably coupled to said rod which connects to an anchoring device on the other end of the spine. The connector then allows relative movement of the rod and thus between the connection point at the lower end of the spine and the anchoring point. It is also known to use helical springs positioned around the rod to allows continuous distraction forces, which stimulates spinal growth.

A connector of the type claimed is known from the <CIT>, from which the preamble of claim <NUM> derives.

The object of the invention is to provide an improved connector for slidably connecting an anchoring device to a rod in a spinal correction system.

This object is met by a connector for slidably connecting an anchoring device to a rod in a spinal correction system, comprising a body, wherein the body has a first tubular opening, a coupling mechanism for coupling the body to the anchoring device, a guiding mechanism provided in said first tubular opening and arranged to guide the rod in a sliding movement along a longitudinal direction of the rod, wherein said guiding mechanism has at least two guiding portions provided at a mutual distance in said first tubular opening and is further arranged to prevent any movement, with respect to the rod, other than a translation along the longitudinal direction of the rod and a rotation around said longitudinal direction of the rod.

From the daily practice of orthopaedic surgeons came the observation that existing growing spine solutions suffer from the issue of proximal junctional kyphosis (PJK), where a moment in a sagittal plane is applied to the spinal correction system. By providing a connector for slidably coupling to a rod, while substantially preventing any relative rotation in the sagittal plane, the problem of kyphosis is believed to be significantly reduced.

Preferably, the guiding mechanism is arranged to prevent any movement with respect to the rod other than a movement with respect to said longitudinal direction of the rod and preferably axial rotation around said longitudinal direction. Generally, it is preferred if the guiding mechanism is arranged to prevent any rotation of the body with respect to the rod in any plane containing the longitudinal direction or axis of the rod. Rotation in for instance the sagittal plane and the coronal plane is thus prevented.

The coupling mechanism is arranged to couple to another orthopaedic device, for instance the anchoring device as mentioned. The coupling mechanism may also be formed integrally with another constructional element, such as an anchoring device. Rotation of such a device in the sagittal and coronal planes is then prevented. As the coupling mechanism, or another device as mentioned above, is preferably rigidly coupled to the body, also the relative movement of the coupling mechanism, and therewith any coupled other device, is fixed. Also such a device is thus not allowed to rotate in the sagittal or coronal plane, or any other plane containing the longitudinal direction or axis as mentioned above.

As mentioned, the guiding mechanism is arranged to prevent any movement, preferably with respect to the rod, other than a translation along or rotation around the longitudinal direction of the rod. In the alternative, only translation is allowed. The connector is then only allowed to translate longitudinally along the length of the rod. Any rotation of the body in other planes is then prevented with respect to the rod.

It is however preferred if guiding mechanism is further, or alternatively only, arranged to also allow a rotation around said longitudinal direction of the rod. In this way, rotational and axial mobility may be maintained while constraining any other movement, including a movement in a sagittal plane associated with kyphosis. As mentioned, rotation of the body with respect to the rod in other planes, such as the coronal and sagittal planes, is preferably also prevented.

It is remarked that when a curved rod is used, as will be explained in greater detail below, longitudinal direction of the rod may vary along the length, also within the connector. The guiding mechanism is then arranged to prevent any movement other than a movement with respect to an average longitudinal direction, as seen along the length, or to substantially prevent any movement as described. The guiding mechanism is arranged to allow relative movement with respect to the rod in only one degree of freedom, preferably sliding of the connector on the rod, i.e. in the longitudinal or axial direction. The guiding mechanism is further arranged to further allow movement in a second degree of freedom, i.e. rotation or roll around the rod. Thus, the guiding mechanism is arranged to only allow movement of the body of the connector, and therewith the coupling mechanism, in only two degrees of freedom, i.e. axial sliding along and rotation around the rod in the transverse plane.

According to a preferred embodiment, the body has a first tubular opening and the guiding mechanism is provided in the first tubular opening. The rod may thus be constrained by the geometric properties of the connector.

According to a preferred embodiment, the guiding mechanism has at least two guiding portions provided at a mutual distance in said first tubular opening. The rod may be constrained by aligned guiding portions acting as a constraining conduit for the rod.

Preferably, the at least two guiding portions are provided at the end parts of the first tubular opening. This allows easy insertion of the guiding portions in the body and the physical size of the connector may be kept to a minimum. This further allows the receiving and guiding rods having more pronounced curvatures, as will be further explained below.

According to a preferred embodiment, the first tubular opening has a first internal diameter, the guiding portions have a second internal diameter, and the first internal diameter is larger than the second internal diameter. The first tubular opening may accommodate a rod with a curvature, in particular a rod contoured into the desired shape in both the coronal and sagittal plane.

According to a preferred embodiment, each guiding portion has a bearing or set of bearings and a bearing holder. The bearing portion is preferably a bearing mounted on the bearing holder and allowed to rotate with respect to said holder. Preferably, the bearing is rotatable around a plurality of axis with respect to said holder. Sliding of the rod is allowed at low friction while preventing metal debris and metallosis or metal poisoning, due to its specific lining. Curved rods are further efficiently received and guided.

According to a preferred embodiment, the guiding portions are spherical bearings. A rod with a curvature may then easily be accommodated through the ends of the tubular opening, since spherical bearings allow three rotations around roll, yaw and pitch axes.

For efficient fabrication, it is preferred if the guiding portions are slid inside the body through slot openings in the body.

According to a preferred embodiment, the guiding portions are slid inside the body via the ends of the first tubular opening. Bearing holders may thus be inserted in the body while the body may retain its integrity and while space for a locking mechanism in the middle part of the connector may be preserved.

According to a preferred embodiment, the guiding portions are fixed using one of a pin mechanism, a thread mechanism, a bayonet mechanism, a snap fit mechanism. More in particular, the bearing holders are fixed using one of a pin mechanism, a thread mechanism, a bayonet mechanism, a snap fit mechanism. In this way, bearings and their bearing holders may be inserted in the body in a tool less manner.

According to a preferred embodiment, a spring is preferably provided and preferably there is further a docking provided for said spring, wherein said spring is arranged for providing a distraction force along the longitudinal direction of the rod. In this way, distraction may be implemented in combination with sagittal control. A first end of the spring may abut the body of the connector, for instance at said docking, while a second end of the spring may abut a stop provided on the rod. Preferably, the spring is arranged around the rod.

According to a preferred embodiment, the body has a locking mechanism for locking the rod in a fixed position with respect to the body. In this way, a permanent fixation may be achieved, which is particularity useful when used in combination with a spring while implanting such a system.

According to a preferred embodiment, the coupling mechanism has a second tubular opening for receiving a stationary rod. Such a rod can be used for fixation to at least one, preferably a plurality of vertebrae, for instance using bone pins. Preferably, said second tubular opening has a direction substantially parallel to the direction of the first tubular opening. In this way, the transmission of a torque between the rods may be minimized.

According to a preferred embodiment, the coupling mechanism has a locking mechanism for locking the stationary rod with respect to the coupling mechanism. In this way, a kyphosis moment on the stationary rod may be transmitted to the connector.

The object of the invention is also met by a connector assembly for spinal correction comprising a connector as described above and an anchoring device for anchoring to the spine, said anchoring device being coupled to the connector via the coupling mechanism of the connector. In this way, kyphosis of a part of the spine may be controlled.

According to a preferred embodiment, the anchoring device has a stationary rod. In particular, the anchoring device has one or more anchoring elements for anchoring in one or more vertebrae. More in particular, the stationary rod is fixed by two anchoring elements in two neighbouring vertebrae. In this way, a kyphosis force on a part, mostly a superior part, of the spine may be controlled.

The object of the invention is also met by a spinal correction system comprising a rod for spinal correction and at least one connector according to any of the above preferred embodiments. In this way, a complete system for growth and/or distraction systems controlling kyphosis is provided.

According to a preferred embodiment, the system further comprises an anchoring device to form with the at least one connector a connector assembly according to any of the above embodiments. In particular, one or more anchors are further provided for anchoring the rod in the spine. In this way, kyphosis of a part, mostly a superior part, of the spine may be controlled.

According to the invention, is further provided a kit of parts comprising at least two of a connector, an anchoring device and a rod.

Also described herein, but not claimed, is a method for providing a spinal correction to a patient, comprising the steps of providing a rod for attachment to the spine of the patient, providing an anchoring device for attachment to the spine of the patient, providing a connector according to any of the above preferred embodiments for connection to the rod and the anchoring device, and coupling the connector to the rod. According to a preferred embodiment, the method further comprises coupling the connector to the anchoring device.

The method preferably comprises a step of attaching the rod to the spine, for instance using bone screws or bone pins. Providing the anchoring device may comprise attaching the anchoring device to the spine, in particular to at least one vertebra. The anchoring device may be unitary with the connector, in the alternative the connector can be coupled to the anchoring device.

The connector is preferably coupled to the rod by sliding the connector, preferably using the guiding mechanism as described above, over the rod. After connection to the anchoring device, the anchoring device can be attached to the spine. Or the connector can be attached to the anchoring device once the anchoring device is attached to the spine.

In particular the connector or system as described may be used for the following non exhaustive list of spinal applications:.

Thus, a method is provided according to any of the above applications, including the step of providing a connector or system as mentioned above.

Although arranged for spinal correction, the connector could be arranged for other orthopaedic applications related to bones or joints in general. For instance, the connector could be used for slidably connecting to rods in system connected to hands and feet. The principle of the connector described here is therefore not limited to spinal correction insofar as the concept of an orthopaedic connector constraining a moment in a given plane as disclosed here may also be declined accordingly for other types of orthopaedic applications.

It is noted that various known planes and directions will be referred to in the present application and are here explained for the ease of the reading. A sagittal plane refers to a plane defined by two axes, one drawn between a head (superior) and tail (inferior) of the body, and one drawn between a back (posterior) and front (anterior) of the body. A coronal plane refers to a plane defined by two axes, one drawn between a center (medial) to side (lateral) of the body, and one drawn between a head (superior) and tail (inferior) of the body. A transverse plane refers to a plane defined by two axes, one drawn between a back and a front of the body, and one drawn between a center and a side of the body.

The present invention will now be described in more detail, with reference to the appended drawings showing currently preferred embodiments of the invention, wherein:.

<FIG> shows a spinal correction system <NUM> comprising a connector <NUM>, an anchoring device <NUM>, a rod <NUM> and anchoring elements <NUM> and <NUM> for anchoring to the spine <NUM>. Each element of the system will now be described successively.

As shown in <FIG>, the rod <NUM> is an elongate member, having a cylindrical shape and being secured to the spinal column <NUM> via two anchoring elements <NUM>, <NUM>. The anchoring elements <NUM>, <NUM> are mounted, or fixed to two vertebrae <NUM>, <NUM> located at a first position along the spine <NUM>, in an inferior part of the spinal column <NUM>. Optionally the rod <NUM> may be anchored at additional anchoring points. The anchoring elements <NUM>, <NUM> are further adapted to receive and secure the rod <NUM>, such that the rod <NUM> is made solidary with the two vertebrae <NUM> and <NUM>.

The rod <NUM> in <FIG> is further illustrated as having a round cross section with a diameter D1. Yet other embodiments may be envisaged with a rod having a different contour and in particular with a rod having one or more flat portions. As illustrated in <FIG>, the rod <NUM> is a straight rod having an axis of symmetry. In such a case, a longitudinal direction A of the rod <NUM> coincides with the longitudinal axis of the rod <NUM>.

The anchoring device <NUM> comprises a stationary rod <NUM> extending along a longitudinal direction B and two anchoring elements <NUM> and <NUM>. The anchoring elements <NUM> and <NUM> may be similar to the anchoring elements <NUM> and <NUM> and may be mounted or fixed to two vertebrae 100n and <NUM>(n+<NUM>) located at a second position along the spine <NUM>, in a superior part of the spinal column <NUM>. The second position is in this example located above the first position along the spinal column <NUM>. Optionally the stationary rod <NUM> may be anchored at additional anchoring points.

The connector <NUM> comprises a body <NUM>, a coupling mechanism <NUM> for coupling the body <NUM> to the anchoring device <NUM>, and a guiding mechanism <NUM>. The guiding mechanism <NUM> (see also figures 2a and 2b) is configured to guide the rod <NUM> in a sliding movement along the longitudinal direction A of the rod <NUM>, and is further arranged to prevent any movement with respect to the rod other than a movement with respect to said longitudinal direction A of the rod <NUM>.

The body <NUM> illustrated in <FIG> has an elongated tubular shape with a longitudinal direction (see arrow C in <FIG>) matching the longitudinal direction A of the axis of the rod <NUM>, such that the rod <NUM> may cross right through the body <NUM> along the longitudinal direction A. Although represented as rather a tubular shaped element, other shapes of a body may be envisaged for receiving the rod <NUM> in the body <NUM>.

The connector <NUM> is such that when assembled in the system of <FIG> any movement in a sagittal plane (see arrow S in <FIG> illustrating this movement) may be constrained. When the rod <NUM> is mounted in the connector <NUM>, or in other words, when the connector <NUM> is coupled to the rod <NUM>, the connector <NUM> may slide freely along the longitudinal direction A of the rod <NUM> while any other movement is prevented. In particular any movement in a sagittal plane is prevented. Only a translation along the direction A and a roll rotation movement around the axis of the rod are allowed by the guiding mechanism <NUM> of the connector <NUM>. In this way, rotational and axial mobility for growth or distraction is maintained while preventing the issue of kyphosis, particularly present in cases of growing or distraction systems.

For the option where some distraction between the lower vertebrae <NUM>, <NUM> and the upper vertebrae 100n, <NUM>(n+<NUM>) is desired, a spring mechanism <NUM> may be provided around the rod <NUM> for constraining the translation movement of the connector <NUM> along the rod <NUM> by exerting a compression effort between a stopper element <NUM> and the body <NUM> of the connector <NUM>. The stopper element can be used proximal and distal depending on the desired function.

In the embodiment of <FIG>, the coupling mechanism <NUM> is integrally attached to the body <NUM> to form an L-shaped connector <NUM>. The long side of the L-shape corresponds substantially to the body <NUM> of the connector <NUM> and extends in the longitudinal direction A of the rod <NUM>. The short side of the L-shaped connector <NUM> corresponds substantially to the coupling mechanism <NUM>. Alternatively the coupling mechanism <NUM> may provide coupling to an additional element (not represented in any of the figures) configured solely for anchoring and/or to receive and secure the stationary rod <NUM> or any other orthopaedic device.

The coupling mechanism <NUM> is configured to receive and secure the stationary rod <NUM>, such that the stationary rod <NUM> is made solidary with the coupling mechanism <NUM> and thus with the connector <NUM>. The coupling mechanism <NUM> is configured to secure the stationary rod <NUM> in a direction B. The direction B may be substantially parallel to the direction A such that the rod <NUM> and the rod <NUM> are substantially parallel to each other and at a mutual lateral distance L1 chosen to minimize the transmission of a torque between the rods <NUM> and <NUM>. The rod <NUM> is further positioned next to the anchoring device <NUM> to preserve mobile segments of the spine as much as possible.

The coupling mechanism <NUM> may comprise a locking mechanism <NUM> for locking the stationary rod <NUM> with respect to the coupling mechanism <NUM>. A screw may for instance be provided in an opening in the coupling mechanism <NUM> for securing the stationary rod <NUM> to the coupling mechanism <NUM>.

Similarly the body <NUM> may comprise a locking mechanism <NUM> for locking the rod <NUM> with respect to the body <NUM>. A screw may for instance be provided in an opening in the body <NUM> for securing the rod <NUM> to the body <NUM>.

Figure 2a illustrates a cross-section of the connector <NUM> connected to a straight rod <NUM>. In particular Figure 2a shows how the body <NUM> has a first tubular opening <NUM> extending through the body <NUM> in a longitudinal direction of the body <NUM> (coinciding with direction A in figure 2a), creating a receptacle for the rod <NUM>. The guiding mechanism <NUM> is then provided in the first tubular opening <NUM> for guiding the rod <NUM> in a sliding movement along the longitudinal direction A of the rod <NUM>.

As illustrated the guiding mechanism <NUM> provided inside the tubular opening <NUM> has at least two guiding portions <NUM>, <NUM> provided at a mutual distance D in said first tubular opening <NUM>. In particular the two guiding portions <NUM>, <NUM> are provided at or near the end parts of the first tubular opening <NUM>. Each guiding portion <NUM>, <NUM> comprises an annular bearing <NUM> housed in a bearing holder <NUM>. Each annular bearing <NUM> can rotate in its bearing holder such that the rod <NUM> may slide and roll with respect to the direction A. The bearings <NUM> may be spherical bearings.

The cross section of the coupling mechanism <NUM> shows further a second tubular opening <NUM> in the coupling mechanism <NUM> for receiving the stationary rod <NUM>. The second tubular opening <NUM> has a longitudinal direction B substantially parallel to the longitudinal direction of the first tubular opening <NUM>.

Figure 2b illustrates a cross-section of the connector when connected to a rod <NUM> having a curvature. Of significance is that the bearings <NUM> are spherical bearings allowing a rotation according to a roll, pitch and yaw rotation axis, see arrows R1 and R2 in figure 2b, allowing the bearings to adjust to the surface of the curved rod <NUM>. The first internal diameter D1 of the tubular opening <NUM> is larger than the second internal diameter D2 of the bearings <NUM> to allow the movement of the rod having a curvature in the region there between. The second internal diameter D2 is dimensioned relative to the diameter of the rod <NUM> to allow a translation with a predetermined friction. In this case the sliding movement of the rod is guided locally at each guiding portion <NUM>, respectively <NUM> in a longitudinal direction A1, respectively A2. It is noted that the longitudinal directions A1 and A2 of the sliding movement of the rod at the guiding portions <NUM> and <NUM> are substantially the same as the longitudinal direction C of the first tubular opening <NUM>.

<FIG> illustrates a perspective view and three cross-sections of a connector <NUM> with a connector body <NUM> comprising two bearing holders <NUM> formed as spherical cavities inside the tubular opening <NUM> in the body <NUM>. At the extremities 10a and 10b of body <NUM> along the longitudinal direction A, the tubular opening <NUM> mouths into an oval shape having a long axis dimension D3 greater than a short side dimension D4, wherein D3 and D4 are chosen relative to the external diameter of the bearings <NUM>, such that D4 is greater than the external diameter of the bearings <NUM> and D4 is smaller than the external diameter of the bearings <NUM>. The oval shaped holes at the ends 10a and 10b of the body allow the insertion and the shape locking of annular bearings <NUM> in the spherical bearing holder cavities <NUM>.

<FIG> illustrate alternative embodiments where the bearing holders <NUM> are separate elements form the body <NUM>. In particular the embodiments of <FIG> show alternatives where the bearings <NUM> and their bearings holders <NUM> are slid inside the body <NUM> via the ends of the first tubular opening <NUM>.

<FIG> illustrates a cross-section of the connector according to an alternative embodiment of the invention with a connector body configured having a pin mechanism <NUM> for locking bearing holders <NUM>. First the bearing holders <NUM> housing the bearings <NUM> are slid from each end of the body <NUM> inside the tubular opening <NUM>, then pins <NUM> are engaged from the outside of the housing into holes provided in the body <NUM> and the bearing holders <NUM> to lock the bearing holders <NUM> inside the body <NUM>.

<FIG> illustrates a cross-section of a connector with a connector body <NUM> configured having a thread mechanism <NUM> for locking bearing holders <NUM>. Each bearing holder <NUM> is provided with a thread <NUM> mating a thread provided on the inner side of the body <NUM> such that the bearing holders <NUM> and the bearings <NUM> may be presented via the ends and fixed by rotation inside the body <NUM>.

<FIG> illustrates a cross-section of the connector with a connector body <NUM> configured having a bayonet mechanism <NUM> for locking bearing holders <NUM>. Each bearing holder <NUM> is provided with a bayonet <NUM> mating a bayonet thread provided on the inner side of the body <NUM> such that the bearing holders <NUM> and the bearings <NUM> may be presented via the ends and fixed by rotation inside the body <NUM>.

<FIG> illustrates a cross-section of the connector with a connector body <NUM> provided with a locking ring mechanism 39a for locking bearing holders <NUM>. Each bearing holder <NUM> is provided with a locking ring 39a meant to lock into a recess provided on the inner side of the body <NUM> such that the bearing holders <NUM> and the bearings <NUM> may be presented via the ends and snap-fitted when the locking ring 38a falls into the recess inside the body <NUM>.

<FIG> illustrates a cross-section of the connector with a connector body <NUM> having a snap fit mechanism for locking bearing holders <NUM>. Each bearing holder <NUM> is provided with a locking profile 39b for a snap fit with a complementary locking profile provided on the inner side of the body <NUM> such that the bearing holders <NUM> and the bearings <NUM> may be presented via the ends and snap fitted inside the body <NUM> when the locking profiles 39b on the bearing holder <NUM> and the body <NUM> interlock.

<FIG> illustrates a cross-section of the connector with a connector body <NUM> configured for interlocking bearing holders <NUM>. Bearing holders <NUM> on opposite ends of the body are configured to interlock inside the body via interlocking profiles 39c1, 39c2 such that the bearing holders <NUM> and the bearings <NUM> may be presented via the ends and snap fitted together inside the body <NUM> when the locking profiles39c of the bearing holders <NUM> interlock.

It is further noted that the above list of ways of mounting the bearings <NUM> inside the connector <NUM> is not exhaustive. Other alternatives may be envisaged by a skilled person depending on the circumstances and materials used. One can imagine for instance alternatives where the bearings would not be inserted by the ends of the tubular opening <NUM> but for instance via lateral openings and slots in the body <NUM>.

As far as materials are concerned, the connector is preferably made of titanium and the rod of cobal-chromium (CoCr) to prevent titanium-on titanium friction and metal debris. Other materials suitable, such as for instance poly ethylene, for the above described movements may however be envisaged as well.

According to an example, a method for spinal correction is provided, comprising the steps of:.

A further step comprises coupling the connector (<NUM>) to the anchoring device (<NUM>).

The method preferably comprises a step of attaching the rod <NUM> to the spine <NUM>, for instance using anchoring elements <NUM> and <NUM>, being bone screws or bone pins. Providing the anchoring device <NUM> may comprise attaching the anchoring device <NUM> to the spine <NUM>, in particular to at least one vertebra 100n and optionally to another vertebrae <NUM>(n+<NUM>). The anchoring device <NUM> may be unitary with the connector <NUM>, in the alternative the connector <NUM> can be coupled to the anchoring device <NUM>.

The connector <NUM> is preferably coupled to the rod <NUM> by sliding the connector100, preferably using the guiding mechanism <NUM> as described above, over the rod <NUM>. After connection to the anchoring device <NUM>, the anchoring device <NUM> can be attached to the spine.

Alternatively the connector <NUM> can be attached to the anchoring device <NUM> once the anchoring device <NUM> is attached to the spine.

Surgery can be performed in particular through a posterior midline skin incision. The anchoring elements <NUM>, <NUM>, <NUM>, <NUM> can be placed with the freehand technique. The rods <NUM> and <NUM> can be passed sub-fascially and contoured into the desired shape in both the coronal and sagittal plane.

It is noted that a surgeon may decide depending on circumstances to alter the sequence of the steps, and start with any one of the anchoring device, the rod and or the connector.

Claim 1:
Connector (<NUM>) for slidably connecting an anchoring device (<NUM>) to a rod (<NUM>) in a spinal correction system, comprising
- a body (<NUM>), wherein the body (<NUM>) has a first tubular opening (<NUM>),
- a coupling mechanism (<NUM>) for coupling the body (<NUM>) to the anchoring device (<NUM>),
- a guiding mechanism (<NUM>) provided in said first tubular opening (<NUM>) and arranged to guide the rod (<NUM>) in a sliding movement along a longitudinal direction (A) of the rod (<NUM>), characterized in that said guiding mechanism has at least two guiding portions (<NUM>, <NUM>) provided at a mutual distance (d) in said first tubular opening (<NUM>) and is further arranged to prevent any movement, with respect to the rod (<NUM>), other than a translation along the longitudinal direction (A) of the rod (<NUM>) and a rotation around said longitudinal direction (A) of the rod (<NUM>).