ZA200703387B

ZA200703387B - Spinal surgery

Info

Publication number: ZA200703387B
Application number: ZA200703387A
Authority: ZA
Inventors: Oelofse Lodewikus Andries
Original assignee: Oelofse Lodewikus Andries
Priority date: 2006-02-01
Filing date: 2007-04-25
Publication date: 2008-09-25

Description

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S111 2007/0538 7 - OE

THIS INVENTION relates, broadly, to spinal surgery. More ) particularly, the invention relates to a cross-linkage device for linking together . and stabilising a pair of rods employed during a spinal lumbar-fusion procedure, and to a method of stabilising such rods.

During certain spinal lumbar-fusion procedures a pair of rods, typically of titanium, is used to hold the part of the lumbar region of the spine whose vertebrae are to be fused together under compression. The rods are connected to vertebrae at opposite ends of the lumbar region of the spine to be fused, and the rods are placed under tension to compress said part. The rods are typically connected to the pedicles of the vertebrae in question, for example by screws, and extend alongside the part of the lumbar region to be fused, on the dorsal side of the spine and on opposite sides of its midline.

When required, the rods are stabilised and linked together by a cross-linkage device. Difficulties can arise if the rods are not parallel to each other, and there is a danger that the cross-linkage device employed can interfere undesirably with the spinal cord, as the device typically has a link which extends between adjacent vertebrae, from one rod to the other.

According to one aspect of the invention there is provided a cross-linkage device for linking together a pair of rods employed during the fusion of the lumbar region of the spine, the device comprising an elongated

. rigid link, and, at or adjacent opposite ends of the link, a pair of clamps respectively for clamping to the rods, each clamp being connected to the link and being clampable both to the link and to the associated rod, and each : clamp being adjustable relative to the link, at least to a limited degree, to alter its spacing from the other clamp and to alter its attitude or orientation relative - to the link, to cater for any misalignment between the rods whereby they depart from being parallel to each other.

The device may be of a surgically acceptable metal, typically titanium, and the link may be in the form of a flattened titanium bar having an opening at or adjacent each end thereof, each opening receiving a said clamp and holding it captive, thereby connecting the bar to the clamp. In turn, each clamp may have a seat portion providing a seat for engaging the associated rod and for holding it captive against the link by clamping it thereto, and a stem having a root via which it is fast with the seat portion, the stem being provided with threads engaging a nut, the stem passing through the associated opening in the bar with the seat portion, on the one hand, and the part of the stem having the threads engaging the nut, on the other hand, being located on opposite sides of the bar and being joined together by the root which 1s located in the opening and permits no more than limited pivoting or swivelling of the clamp about the axis of the stem, relative to the bar, engagement between the root and the periphery of the opening preventing rotation or excessive pivoting of the clamp about said axis relative to the bar, and the nut holding the clamp releasably in position with the root in the opening.

. More particularly, each opening in the bar may be in the form of an elongated parallel-sided closed-ended slot, along which the associated clamp is slidable, to a limited degree, to cater for different spacings between the rods to which the clamps are to be clamped, to provide the adjustable } spacing between the clamps, each root located in the associated slot having a - pair of parallel oppositely outwardly facing flat sides respectively opposed to opposite sides of the slot, for limiting the degree to which the root can pivot in the slot relative to the bar about the axis of the associated stem.

Each seat portion may be more or less hook-shaped, the interior of the hook defining a part-cylindrical seat for seating against the associated rod, which rod is typically cylindrical in shape, and the hook extending along a curve, which may be arcuate, from the root to a free end or tip of the hook remote from the root, in a direction parallel to the flat sides of the root, the seat being curved about an axis normal to said flat sides of the root.

The link may be provided with a curved central portion whereby, when the device is in place in use and the link extends transversely to the rods from on of the clamps clamped to its associated rod to the other clamp clamped to its associated rod, with the link extending past the dorsal side of the spinal cord at a position between two vertebra to be fused together, the curved central portion of the link remains sufficiently spaced from the spinal cord to reduce any risk of unwanted interference with the spinal cord by the link.

- ¥2007/p5355 ; . According to another aspect of the invention there is provided a cross-linkage device for linking together a pair or rods employed during the fusion of the lumbar region of the spine, the device comprising an elongated ngid ink and, at or adjacent opposite ends of the link, a pair of clamps ) respectively for clamping to the rods, each clamp being connected to the link - and clampable to the link and to the associated rod, the link being provided with a curved central portion whereby, when the device is in place in use and the link extends transversely to the rods from one of the clamps clamped to the associated rod to the other clamp clamped to the associated rod, with the link extending past the dorsal side of the spinal cord at a position between two vertebrae to be fused together, the curved central portion of the link remains sufficiently spaced from the spinal cord to avoid or at least reduce any risk of unwanted interference with the spinal cord by the link.

It will be appreciated in this regard that the orientation of each clamp can be adjusted into two different attitudes relative to the bar, one in which the tip or free end of the hook is directed longitudinally outwardly, relative to the bar, and one in which the tip or free end is directed longitudinally inwardly, relative to the bar. To adjust between these attitudes, the nut is unscrewed from the stem, the stem and root are withdrawn from the associated opening, and the clamp is rotated by substantially 180° about the axis of the stem, before the clamp is re-inserted into the opening and re- connected in place there with the root in the opening, by means of the nut.

This feature enhances the adjustability of the spacing of the seats of the clamps lengthwise relative to the bar, although it will usually be preferred to

©522007/83387 . have the tips of both hooks directed longitudinally outwardly, relative to the bar, away from each other, the openings being provided close to the ends of the bar so that the hooks in use clamp the rods to the ends of the bar, with substantially no part of the device, other than the tips of the hooks, projecting ) past the rods in directions lateral relative to the rods and spine.

The invention extends to a method of stabilising a pair of rods employed during the fusion of the lumbar region of the spine, by linking them together, the method comprising linking the rods together by means of a cross-linkage device of the type defined and described above, by clamping the clamps respectively to the rods and to the link.

Thus, in use, the device is clamped in position to the rods which have already been connected to the spine of a patient, by clamping the respective clamps to the rods after adjusting the orientation of either or both of the clamps relative to the link, to cater for any misalignment of the rods whereby they depart from being parallel to each other, the link being located between adjacent vertebrae and the curve in the link partially encircling the spinal cord to keep the material of the link sufficiently spaced from the spinal cord to avoid or at least reduce any unwanted interference with the spinal cord by the link.

The invention will now be described, by way of non-limiting illustrative example, with reference to the accompanying diagrammatic drawings in which:

. Figure 1 shows a schematic partially-exploded three-dimensional view of a device in accordance with the invention;

Figure 2 shows a schematic plan view of the device of Figure 1 from above, In place linking and stabilising a pair of rods connected to the spine of ) a patient; and . Figure 3 shows a schematic rear elevation of the device of Figure 2, in place.

In the drawings, with particular reference to Figure 1, a cross- linkage device in accordance with the invention is generally designated by reference numeral 10. The device 10 comprises a link in the form of a flattened titanium bar 12, and a pair of clamps 14 connected to the bar 12, adjacent opposite ends of the bar 12.

The bar 12 has a more or less constant thickness and has a pair of end portions 16 separated by a central portion 18, the bar at its end portions 16 having a width which is somewhat greater than the width of the central portion 18. Each end portion 16 is provided with an elongated, parallel-sided closed-ended slot 20, the slots 20 extending lengthwise relative to the bar and the clamps 14, as described hereunder, passing respectively through the slots 20. The central portion 18 is curved to be located to one side of the end portions, which are more or less coplanar and aligned axially with each other, the curvature of the portion 18 being about an axis parallel to the major faces of the bar 12, and normal to the longitudinal direction of the bar 12.

Each clamp 14 is also of titanium and comprises a threaded stem 22 and a hook-shaped seat portion 24, the stem 22 being provided with a nut 26. The stem 22 and seat portion 24 are joined together by a root 28 which In use is located in one of the slots 20 of the bar 12. The stem 22 and . the seat portion 24 are thus located on opposite sides of the bar 12, the stem 22 being on the same side of the associated end portion 16 as the central portion 18. The root 28 has a pair of parallel oppositely outwardly facing flat sides 30 respectively opposed to the opposite parallel sides of the associated slot 20, the root 28 being slidable along the associated slot 20 with engagement between the sides 30 of the root 28 and the respective parallel sides of the slot 20 permitting no more than limited pivoting of the clamp 14, about the axis of the stem 22, relative to the bar 12, each root 28 being a rattling fit in its slot 20, the spacing between its sides 30 being less than the spacing between the parallel sides of the slot 20.

The interior of the hook of each seat portion 24 provides a part- cylindrical seat 32 for seating against the associated rod, the seat portion extending from the root 28 to a tip 34, circumferentially relative to the seat 32, which is curved about an axis normal to the flat sides 30 of the root 28. The hooks of the seat portions 24 are directed oppositely outwardly, longitudinally relative to the bar 12, away from each other so that the tips 34 are outermost, at or adjacent the longitudinal extremities of the ends of the bar 12. Each clip 14 can be detached from the bar 12 by unscrewing the nut 26 from its stem 22, withdrawing the root 28 and stem 22 from the associated slot 20, rotating

. the clamp by more or less 180° about the axis of the stem 22 relative to the bar 12, and re-inserting the stem 22 and root 28 into the slot 20, so that the root 28 is located in the slot 20, followed by re-connecting the nut 26 to the stem 22, to locate and hold the root 28 captive in the slot 20.

. In use, and with particular reference to Figures 2 and 3, after a pair of rods 36 have been connected to the lumbar region of a patient's spine (one of whose vertebrae is shown schematically at 38 in Figure 2 and two of which are shown in Figure 3) to extend under tension alongside each other and alongside the spinal column to hold said lumbar region to be fused under compression, the device 10 1s clamped in place by clamping the rods 36 respectively to the ends of the bar 12 by means of the clamps 14. Each rod 36 is seated against the seat 32 of the associated clamp 14 and is clamped thereby to the adjacent end of the bar 12 by tightening the associated nut 26 on the associated stem 22. Any out-of-parallel misalignment of the rods 36 is catered for by pivoting or swivelling of either or both of the clamps 14 about the axes of their stems 22, and the bar 12 extends from one rod 36 to the other at a position between adjacent vertebrae 38, dorsally of the spinal cord 48, the curve of the central portion 18 keeping the material of the bar 12 safely remote from the spinal cord 40 (see particularly Figure 2).

1. A cross-linkage device for linking together a pair of rods employed during the fusion of the lumbar region of the spine, the device comprising an elongated rigid link, and, at or adjacent opposite ends of the link, a pair of : clamps respectively for clamping to the rods, each clamp being connected to the link and being clampable both to the link and to the associated rod, and each clamp being adjustable relative to the link, at least to a limited degree, to alter its spacing from the other clamp and to alter its attitude or orientation relative to the link, to cater for any misalignment between the rods whereby they depart from being parallel to each other. 2. A device as claimed in Claim 1, in which the link is in the form of a flattened titanium bar having an opening at or adjacent each end thereof, each opening receiving a said clamp and holding it captive, thereby connecting the bar to the clamp.

3. A device as claimed in Claim 2, in which each clamp has a seat portion providing a seat for engaging the associated rod and for holding it captive against the link by clamping it thereto, and a stem having a root via which it is fast with the seat portion, the stem being provided with threads engaging a nut, the stem passing through the associated opening in the bar with the seat portion, on the one hand, and the part of the stem having the threads engaging the nut, on the other hand, being located on opposite sides of the bar and being joined together by the root which is located in the opening and

} permits no more than limited pivoting or swivelling of the clamp about the axis of the stem, relative to the bar, engagement between the root and the periphery of the opening preventing rotation or excessive pivoting of the clamp about said axis relative to the bar, and the nut holding the clamp ) releasably in position with the root in the opening. 4. A device as claimed in Claim 2 or Claim 3, in which each opening in the bar is in the form of an elongated parallel-sided closed-ended slot, along which the associated clamp is slidable, to a limited degree, to cater for different spacings between the rods to which the clamps are to be clamped, to provide the adjustable spacing between the clamps, each root located in the associated slot having a pair of parallel oppositely outwardly facing flat sides respectively opposed to opposite sides of the slot, for limiting the degree to which the root can pivot in the slot relative to the bar about the axis of the associated stem. 5. A device as claimed in Claim 4, in which each seat portion is more or less hook-shaped, the interior of the hook defining a part-cylindrical seat for seating against the associated rod, and the hook extending along a curve from the root to a free end or tip of the hook remote from the root, in a direction parallel to the flat sides of the root, the seat being curved about an axis normal to said flat sides of the root. 6. A device as claimed in any one of Claims 1-5 inclusive, in which the link is provided with a curved central portion whereby, when the device is in

. place in use and the link extends transversely to the rods from on of the clamps clamped to its associated rod to the other clamp clamped to its associated rod, with the link extending past the dorsal side of the spinal cord at a position between two vertebrae to be fused together, the curved central portion of the link remains sufficiently spaced from the spinal cord to reduce ; any risk of unwanted interference with the spinal cord by the link. 7. A cross-linkage device for linking together a pair or rods employed during the fusion of the lumbar region of the spine, the device comprising an elongated rigid link and, at or adjacent opposite ends of the link, a pair of clamps respectively for clamping to the rods, each clamp being connected to the link and clampable to the link and to the associated rod, the link being provided with a curved central portion whereby, when the device is in place in use and the link extends transversely to the rods from one of the clamps clamped to its associated rod to the other clamp clamped to its associated rod, with the link extending past the dorsal side of the spinal cord at a position between two vertebrae to be fused together, the curved central portion of the link remains sufficiently spaced from the spinal cord to reduce any risk of unwanted interference with the spinal cord by the link. 8. A device as claimed in Claim 1 or Claim 7, substantially as dgscribed and as illustrated herein by the drawings.

DATED THIS 25™ day of APRIL 2007

ALAN LEWIS

ADAMS & ADAMS

APPLICANT'S PATENT ATTORNEYS