WO2012062464A1

WO2012062464A1 - Spine fixation installation system

Info

Publication number: WO2012062464A1
Application number: PCT/EP2011/005631
Authority: WO
Inventors: Franz Copf
Original assignee: Spontech Spine Intelligence Group Ag
Priority date: 2010-11-10
Filing date: 2011-11-09
Publication date: 2012-05-18

Abstract

A spine fixation installation system comprises a spine fixation system (10) including a rod (12), a plurality of pedicle screws or other fasteners (14) and a plurality of connectors (18). The spine fixation installation system further comprises a rod bending device (40) for bending the rod (12). To this end the rod (12) is provided with a plurality of longitudinal marks (30). A computer (22) of the spine fixation installation system is programmed to compute a desired shape of the rod (12).

Description

SPINE FIXATION INSTALLATION SYSTEM

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to spine fixation systems that are used for the surgical treatment of spinal disorders which may require correction, stabilization, adjustment or fixation of the spinal column. More particu^¬ larly, the invention relates to a spine fixation installation system comprising a computer, a spine fixation system and a rod bending device.

2. Description of Related Art

Various types of spinal column disorders are known and include scoliosis (abnormal curvature or rotation of vertebrae relative to the plane of the spine) , kyphosis (abnormal backward curvature of the spine) and spondylolisthesis (forward displacement of a lumber vertebra) , all of which in^¬ volve a "misalignment" of the spinal column. Patients who suffer from such conditions usually experience extreme, de^¬ bilitating pain and physical deformity due to the condition. In severe cases treatments for these conditions have used a technique known as fusion with spinal fixation which results in the . mechanical immobilization of areas of the spine and the eventual fusion of the vertebrae in the regions treated. In less severe cases treatment comprises decompression of the affected nerves and fusion of the vertebrae involved.

Fusion, however, is not usually successful unless the vertebrae are also fixed for a time period by a mechanical device' installed internally during surgery. This allows the fused bone time to heal. Numerous mechanical systems have been proposed for this purpose. Screw and rod systems and screw and plate systems are commonly used to this purpose. The former system typically uses a rigid rod secured to the spine by screws inserted in the pedicles for holding the rod. The rod is usually bent to the desired configuration, and this both manipulates and holds the vertebrae in that same configuration until the fusion process can permanently accomplish the same thing. Since each patient has his or her own spinal characteristics or anatomy, including bone shape and bone density, the exact location of the pedicle screws and the other parts of the spine fixation system is determined while the patient is on the operating table. For that reason the rods have to be bent during the operation. However this process is very time consuming, because contouring the rod to correspond to the three-dimensional configuration of the spine can be ex^¬ tremely difficult and can lead to mistakes.

Various rod bending devices have been proposed that shall assist the surgeon to contpur the rods quickly and accu^¬ rately. Some of these devices have a very simple construction and basically provide additional leverage, only. See US 5,113,685, US 5,161,404, US 5,389,099 and US 2006/0264973 Al. More sophisticated devices such as those disclosed in US 5,490,409, US 5,548,985, US 6,644,087 Bl and US 2006/0150698 Al use rollers that engage the rod and assist in bending it with a desired curvature. Other types of bending devices such as known from US 6,006,581 are specifically designed to copy the shape of a given curved rod to another rod. US 6, 035, 691 discloses a rod bending device that comprises a plurality of rollers that are arranged next to each other on a lever. The positions of the rollers can be adjusted with the help of adjustment screws. If the lever with the rollers is pressed down, the contour defined by the positions of the rollers is transferred to a rod which is fixed in a holder to which the lever is articulated. Adjustable shafts sup^¬ porting the rollers are provided with a scale. For a desired curvature a computer indicates how the shafts have to be ad^¬ justed with the help of the scale. A drawback of this prior art bending device is that it is not possible to produce more complex contours, for example contours comprising undulations, or three dimensional contours. Apart from that it is very time consuming to adjust all the rollers individu^¬ ally to produce a single bend.

It has been discovered that, from a medical point of view, it is sometimes unsatisfactory to bend the rods only with the view to simply connect all the pedicle screws. This is because the vertebrae are arranged during the surgery not necessarily in those positions that would be ideal for the fusing process. An experienced surgeon may be able to bend the rods in such manner that the spine fixation system fi^¬ nally manipulates the vertebrae such that the fusion takes place with the vertebrae being arranged in their optimum anatomical positions. But such an approach is prone to error and cannot predictably result in an optimum medical treatment .

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to im prove the spine fixation installation process such that the siirgeon is assisted in fixing the vertebrae in their timum anatomical configuration.

This object is solved by a spine fixation installation system comprising a spine fixation system. The spine fixation system comprises a rod, a plurality of fasteners each being configured to be secured to a vertebra to be treated, and a plurality of connectors. Each connector is attached to or is capable of being attached to one of the fasteners and comprises a seat member that is configured to be connected to the rod. The spine fixation installation system further comprises a rod bending device which is configured to bend the rod after it has been placed in or on the device at a desired longitudinal position. To this end the rod, which is configured such that it can be bent into a desired shape with the help of the bending device, is provided with a plu^¬ rality of longitudinal marks that indicate different longi^¬ tudinal positions along the rod. A computer of the spine fixation installation system is programmed to compute a de^¬ sired shape of the rod and to output a longitudinal symbol that unambiguously identifies one of the longitudinal marks provided on the rod.

With such a system it is possible to use a computer that assists the surgeon in determining an optimum contour of the rod. With the help of the longitudinal marks it is then easy for the surgeon to bend the rod with help of a relatively simple rod bending device, for example a device as it is known from US 2006/0150698 Al, such that it receives the contour that has been determined before by the computer.

The computer may compute a desired shape of the rod using 2D or 3D images of the vertebrae to be treated. The computer program may also access databases in which configurations of the vertebrae of healthy and/or affected spine segments from other patients are stored. It may also be necessary for the computer program to access images of the configuration of the pedicle screws that have been screwed into the vertebrae to be treated. The bending angle may be output by the computer on a display or a printout so that the user is able to bend the rod until the bending angle corresponds to what is shown on the dis^¬ play or the printout.

Usually, however, it will be more effective if the computer is programmed to output a bending symbol that identifies the bending angle by which the rod shall be bent with the help of the rod bending device. The rod bending device may then be capable to bend the rod by a bending angle that can be set by a user depending on the bending symbol that has been output by the computer. For example, the bending device may comprise a movable handle that has to be displaced to bend the rod. In the simplest case the rod bending device com^¬ prises some kind of scale so that the displacement of the handle can be visually checked. The bending symbol then sim^¬ ply identifies a position on the scale that is provided on the rod bending device. Then the surgeon may directly pro^¬ duce the desired bending angle, and consequently there is no need to check the bending angle on the basis of a computer display or a printout.

The marks that indicate different longitudinal positions along the rod may be engraved or printed on the surface of the rod so that they can be visually inspected. In principle, however, it is also possible to use non-visible marks that can be inspected only with the help of additional ma^¬ chinery. For example, the marks could be configured as electronic marks that are concealed under the surface of the rod and can be detected only with the help of electronic de^¬ vices. Marks that can be detected by optical or electronic devices may be useful if the rod bending device is a more complex machine, for example a machine that automatically reads the longitudinal marks and produces the desired bends. In some embodiments the longitudinal marks are equally spaced apart from each other, and in other embodiments at least some of the longitudinal marks are formed by or la^¬ beled with different symbols so that these marks can be unambiguously distinguished from each other. Then the longitudinal marks, together with the symbols, form in fact a scale of length on the rod that is used as a reference for determining the longitudinal position where the rod shall be bent .

In other embodiments the rod is provided with a plurality of angular marks that indicate different angular positions along a circumference of the rod. This is particularly use^¬ ful if the rod has a circular or oval cross-section, because then it is difficult or even impossible to determine a certain angular position of the rod without any angular marks on it. Also the angular marks may be formed by or labeled with different symbols so that these angular marks can be unambiguously distinguished from each other.

But also if the cross-section of the rod is rectangular or square, angular mark symbols indicating the different orientations of the rod are useful to position the rod in the rod bending device in a certain angular position. Only with angular marks it is possible to reproducibly produce more complex three dimensional contours of a rod.

If the angular marks are provided at least at longitudinal positions of the rod where longitudinal marks are provided, it is possible to determine with two symbols each point where the longitudinal and the angular marks intersect. Then the longitudinal and the angular marks may form a grid extending over the circumferential surface of the rod, wherein at least some of the marks are labeled with symbols. The ability of a rod to be bent into a desired shape depends mainly on the material of the rod, but also on the diameter and the cross-sectional shape. These parameters have to be chosen such that the rod can be bent with a -rod bending device, but does not significantly bend after it has been installed into the patient's back.

Subject of the invention is also a method of bending a rod of a spine fixation system comprising the following steps: a) providing a rod as described above; b) using a computer that is programmed to compute a de^¬ sired shape of the rod and to output a longitudinal symbol that unambiguously identifies one of the longitudinal marks provided on the rod; c) placing the rod in or on a rod bending device at a lon^¬ gitudinal position such that the longitudinal mark identified by the symbol is located in a predetermined spatial relationship with respect to the rod bending device; d) bending the rod.

In step a) a rod provided with a plurality of angular marks that indicate different angular positions along a circumference may be provided. The computer used in step b) may then be programmed to output an angular symbol that unambiguously identifies one of the angular marks provided on the rod. In step c) the rod may be placed in or on the rod bending device such that the angular mark identified by the symbol is located in a predetermined spatial relationship with respect to the rod bending device. In some embodiments the computer used in step b) is pro^¬ grammed to output a bending symbol that identifies the bend^¬ ing angle by which the rod shall be bent with the help of the rod bending device. In step d) the rod is then bent using the rod bending device by the bending angle, thereby using a scale or a display of the rod bending device on which a quantity related the bending angle is indicated.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompa^¬ nying drawing in which:

FIG. 1 partial perspective view of a prior art spine fixation system;

FIG. 2 shows a computer that is used to compute a desired contour of the rods that are part of the spine fixation system shown in FIG. 1;

FIG. 3 is a top view of one of the rods according to a first embodiment;

FIG. 4 is a side view of a rod bending device which is used to bend the rod shown in FIG. 3 such that it receives the contour computer by the computer;

FIG. 5 is a side view of the rod bending device shown in

FIG. 4, together with a rod that has been bent by the device;

FIG. 6 is an enlarged representation of FIG. 5; FIG. 7 is a cross-sectional view of an upper portion of the rod bending device shown in FIGS. 4 to 6;

FIG. 8 is a top view of one of the rods according to a second embodiment in which the rod is additionally provided with angular marks;

FIG. 9 is an enlarged cutout from FIG. 8 ;

FIG. 10 is a front view of the rod shown in FIGS. 8 and 9 after it has been bent three-dimensionally .

DESCRIPTION OF PREFERRED EMBODIMENTS

1. Spine Fixation System

A portion of a prior art spine fixation system 10, as it is known from WO 2010/108665 A2 , is shown in the perspective view of FIG. 1 after having been installed in a segment of a human spine. This segment comprises three vertebrae VI, V2, V3 which are arranged one behind the other. For the sake of simplicity the vertebrae adjacent to this segment are not shown in .FIG . 1.

The spine fixation system 10 comprises two rods 12 which extend on either side of the spine segment along a longitudinal direction of the spine. The rods 12 are rigid and curved elements made of a suitable metal, for example titanium, and have a circular cross section. However, it is also known to use rods having other than circular cross-sections, for example an oval or polygonal cross-section. In the embodiment shown the rods 12 are only slightly curved so that the cur^¬ vature cannot be readily seen in the perspective view of FIG. 1. Depending on the position of the spine segment along the human spine the curvature may be much stronger. 631

The rods 12 are fastened to the vertebrae VI, V2, V3 with the help of pedicle screws 14, which are secured in the ped^¬ icles 16 of the vertebrae VI, V2 V3, and connectors 18 that connect the pedicle screws 14 to the rods 12. Each connector 18 has ^"a seat member formed by a tulip 20 that has various degrees of freedom so that it can be positioned in many dif^¬ ferent ways. This makes it possible to connect the curved rods 12 to the pedicle screws 14 also in those cases in which the curved rods 12 do not exactly extend along the curved line that is defined by the positions of the pedicle screws 14.

In FIG. 1 it is assumed that the pedicle screws 14 are screwed into the vertebrae VI, V2, V3 in such a manner that the tulips 20 on one side of the spine segment are all ar^¬ ranged in a single plane. Consequently, the rods 12 need to be curved in one plane, only.

2. Spine Fixation Installation System

The spine fixation system 10 shown in FIG. 1 is, apart from the inventive improvement of the rods 12, part of a spine fixation installation system in accordance with the present invention. FIGS. 2 to 4 show other components of the spine fixation installation system in accordance with the present invention .

Referring first to FIG. 2, the spine fixation installation system comprises a computer 22 which is programmed in such a manner that it computes a desired shape of the rods 12. To this end the computer 22 first determines a spatial configu^¬ ration of the vertebrae VI, V2 , V3 which comes as close as possible to the natural anatomic configuration for the patient to be treated. If the vertebrae were simply fixed by the spine fixation system in the spatial configuration in which they are found during the surgery, there would be an increased risk that the patient will again experience pain after some time. This is because only an anatomical correct spatial configuration of the vertebrae ensures that the vertebrae, the intervertebral disks and in particular the surrounding ligaments are not unduly stressed due to some kind of misplacement.

For determining the optimum spatial configuration of the vertebrae it is usually necessary to access 2D or 3D images of the vertebrae of the affected spine segment that have been taken in different positions (e.g. inclination, recli- nation, neutral) . Also statistical data that relate to the same spine segments and have been obtained for other comparable patients may be considered during such a determina^¬ tion. The computer program may then propose one or more possible configuration, and the surgeon finally decides which configuration shall be established.

More details with regard to the determination of an anatomical correct spine configuration are described in the provisional US patent application 61/387,469 filed February 26, 2010 whose full disclosure is incorporated herein by reference .

In a next step the computer 22 determines, on the basis of the optimum spine configuration and possibly of optical images from which the positions of the pedicle screws 14 can be determined, how the rods 12 should be curved such that the vertebrae are later moved to and fixed at their correct anatomical positions.

In a further step the rods are bent such that they receive the contour that has been determined by the computer 22. In accordance with the present invention special rods are used that cooperate with a rod bending device which is basically designed as it is known in the art as such and which is shown in the side view of FIG. 4.

Reference is first made to FIG. 3 which is a top view on one of the rods 12 in accordance with a first embodiment of the present invention. The rod 12 is, in its unbent original state, straight and has a circular cross section, as denoted at 26. On its circumferential surface 28 the rod 12 is pro^¬ vided with a plurality of longitudinal marks 30 that are equally spaced apart along the longitudinal direction of the rod 12. The longitudinal marks 30 (or strictly speaking every second mark 30) are labeled with different symbols 32 so that the marks 30 can be unambiguously distinguished from each other. In this embodiment Arabic numbers are used as symbols 32, but other symbols may be used instead. The marks 30, together with the symbols 32, form a scale 34 on the surface 28 of the rod 12.

A rod bending device 40, which is also a component of the spine fixation installation system of the present invention, is configured to bend the rod 12 after it has been placed in the device 40 at a desired longitudinal position, as it is illustrated in FIG. 5.

In the following the design of the rod bending device 40 will be explained in more detail with reference to. FIG. 6 which shows the rod bending device 40 in the operating state as in FIG. 5, but at a larger scale.

The rod bending device 40 includes a handle portion 42 con^¬ figured to fit in the palm of a user and a leaver portion 44 which is pivotally coupled to the handle portion 42. At the upper end of the handle portion 42 a rod seat 46 is formed between two side walls 48a, 48b of the handle portion 42 from which only one side wall 48a facing the viewer can be seen in FIG. 6. The two opposite side walls 48a, 48b define a channel which is configured to receive and hold the rod 12 to be bent .

The rod bending device 40 further includes a movable linkage system 50 for rotatably coupling the leaver portion 44 to the handle portion 42 and for supplying a force to bend the rod 12 when the leaver portion 44 pivots towards the handle portion 42. A user actuates the device 40, so as to provide controlled bending of the rod 12 inserted into the rod seat 46, by pivoting the lower end of the leaver portion 44 to^¬ wards the handle portion 42, for example by squeezing the leaver 44 while holding the handle portion 42 fixed. As the leaver portion 44 pivots towards the handle portion 42, the movable linkage system 50 applies a force to a selected por^¬ tion of the rod 12 to bend the rod in the vicinity of the selected portion by a predetermined amount.

A biasing mechanism such as a spring may be provided between the handle portion 42 and the leaver portion 44 for biasing the leaver portion 42 towards a selected position (not shown) .

The movable linkage system 50 of the embodiment shown in^¬ cludes a plurality of pivotally connected links that translate movements of the leaver portion 44 towards the handle portion 42 into an upward and forward force applied to the rod 12. The kinematics of the linkage system 40 give a me^¬ chanical advantage to the user, allowing for the movement of the leaver portion 44 to produce a force sufficient to bend the rod 12.

The components of the movable linkage system 50 include a first pivot 52a, a second pivot 52b, a third pivot 52c, a fourth pivot 52d, a fifth pivot 52e and a sixth pivot 52f . As it is shown in the cross section of FIG. 7, the rod 12 is guided between the fourth and fifth pivots 52d, 52e that can be commonly articulated, and a roller 54 that is supported by the sixth pivot 52f and closes the rod seat 46 from above .

Actuation of the leaver portion 44 results in an upward movement of the fourth and fifth pivots 52d, 52e. The bending angle is thus determined by the rotational angle by which the leaver portion 44 is pivoted around the first pivot 52a. This rotational angle can be measured with the help of a leaver scale 56 which is provided on an extension 58 connected to the handle portion 42. An angle pointer 60 is attached to the leaver portion 44 such that it points on the scale 58, and a quantity representing the bending angle is visualized by the angle pointer 60 when pointing on a specific mark of the leaver scale 56.

At the upper part of the handle portion 42, and in the vicinity of the rod seat 46, a seat pointer 62 is arranged.

For more details with regard to the rod bending device 40, reference is made to US 2006/0150698 Al whose full disclosure is incorporated herein by reference.

Referring back to FIGS. 2 to , it will now be explained how the rod 12 will be bent such that it receives the contour that has been determined beforehand by the computer 22:

Based on the computed contour of the rod 12, the computer 22 determines one or more longitudinal symbols that each unambiguously identifies one of the longitudinal marks 30 provided on the rod 12. In FIG. 2 the longitudinal symbols 24 are shown on the left hand side of a display screen 23 of the computer 22. The symbol "L" denotes that the following number represents a longitudinal symbol. Thus the symbol "L = 5" instructs a user, after he has inserted the rod 12 into the rod seat 46 of the rod bending device 40, to ad^¬ vance the rod 12 until the longitudinal mark 30 indicated with the symbol "5" reaches the seat pointer 62 in the vi^¬ cinity of the rod seat 46.

The computer 22 also determines one or more bending symbols that each unambiguously identifies one of the marks or sym^¬ bols on the leaver scale 56. In FIG. 2 the bending symbols 27 are shown on the right hand side of a display screen 23 of the computer 22. The symbol "R" denotes that the following number relates to a bending symbol. Thus the symbol "R=8" instructs a user, after he has advanced the rod 12 to the determined longitudinal position, to squeeze the leaver portion 44 and the handle portion 42 until the angle pointer 60 attached to the leaver portion 42 points to the bending symbol displayed on the display screen 23. After this step the rod 12 is exactly bent by the bending angle and at the longitudinal position that have been determined by the computer 22.

Often it will be necessary to bend the rod 12 not only once but a couple of times at different positions and bending an gles. In this case the user releases the leaver portion 44 so that the (now curved) rod 12 can be further advanced in the rod seat 46 until the next longitudinal position indicated on the display screen 23 is reached (here the second longitudinal position is indicated by the longitudinal sym^¬ bol "7.5"). Then the user squeezes again the leaver portion 54 until the angle pointer 60 points on the corresponding mark on the leaver scale 56 (here bending symbol "4") . These steps are repeated until the rod 12 has the contour that has been determined before by the computer 22.

As a matter of course, it is also possible to produce an un^¬ dulated contour in which concave and convex curvatures al^¬ ternate. Then the rod 12 is simply rotated around its longitudinal axis by 180° in the rod seat 46 before the leaver portion 44 is squeezed. On the display 23 such a negative curvature may be indicated by a minus sign in front of the bending symbol.

3. Alternative embodiment

FIG. 8 is a top view of a rod 12 according to a second em^¬ bodiment in which the surface 28 of the rod 12 is provided not only with longitudinal marks 30, but also with angular marks 70. The angular marks 70 are in this embodiment formed by lines that extend along the longitudinal direction of the rod 12 and are equally spaced apart along its circumference.

As can be seen from the enlarged cut-out of FIG. 9, the an^¬ gular marks 70 are labeled with angular symbols 72. In this particular embodiment small letters are used as angular symbols 72, but as a matter of course other symbols which make it possible to distinguish the angular marks 70 from one other may be envisaged as well.

The longitudinal marks 30 and the angular marks 70 form a regular grid 74 on the surface 28 of the rod 12, as can be seen from FIG. 8. By indicating a longitudinal symbol and an angular symbol it is possible to unambiguously identify any of the points of intersection of the grid 74.

When advancing the rod 12 in the rod seat 46 of the rod bending device 40, it is not only possible to arrange the rod 12 within the rod seat 46 at a desired longitudinal position, but also at a desired angular position. If the com^¬ puter 22 outputs also angular symbols indicating the angular position of the rod 12 before the bending takes place, the rod 12 may be rotated within the rod seat 46 until the point of intersection determined by the longitudinal symbol 32 and the angular symbol 72 is placed directly in front of the seat pointer 62 of the rod bending device 40.

The additional angular 70 make it possible to give the rod 12 not only a two dimensional, but a three dimensional con^¬ tour as desired. FIG. 10 is a front view of a rod 12 that has been bent three-dimensionally . In this illustration one of the lateral faces 76 is arranged in the plane of the sheet, and it can be seen that the rod 12 curves not only in one plane, but in two orthogonal planes.

Such a three dimensionally curved rod 12 is useful particularly in those cases in which it is not easily possible to adjust the pedicle screws 14 such that the connectors 18 are all arranged in a single plane.

In short, the position of longitudinal marks 30 and angular marks 70 makes it possible to uniquely and completely define the spatial position of the rod in the rod bending device 40 before it is bent. By additionally providing information with regard to the bending angle, it is possible to transfer almost any arbitrary contour to the rod with the help of a simple rod bending device 40.

The above description of the preferred embodiments has been given by way of example. From the disclosure given, those skilled in the art will not only understand the present invention and its attendant advantages, but will also find ap- parent various changes and modifications to the structures and methods disclosed. The applicant seeks, therefore, to cover all such changes and modifications as fall within the spirit and scope of the invention, as defined by the ap- pended claims, and equivalents thereof.

Claims

A rod of a spine fixation system, wherein the rod (12) is configured such that it can be bend into a desired shape with the help of a bending device, wherein the rod (12) is provided with a plurality of longitudinal marks (30) that indicate different longitu^¬ dinal positions along the rod (12).

The rod of claim 1 or 2, wherein at least some of the longitudinal marks (30) are formed by or la^¬ beled with different symbols (32) so that that these longitudinal marks (30) can be unambiguously distinguished from each other.

The rod of any of the preceding claims, wherein the rod (12) is provided with a plurality of angular marks (70) that indicate different angular positions along a circumference of the rod (12).

The rod of claim 3, wherein at least some of the angular marks (70) are formed by or labeled with different symbols (72) so that that these angular marks (70) can be unambiguously distinguished from each other.

A spine fixation system, comprising a) a rod (12) of any of the preceding claims, b) a plurality of fasteners (14), wherein each fastener (14) is configured to be secured to a vertebra (VI, V2, V3) to be treated, and c) a plurality of connectors (18), wherein each connector 818) is attached to, or is capable of being attached to, one of the fasteners (14) and comprises a seat member (20) that is con^¬ figured to be connected to the rod (12) .

A spine fixation installation system, comprising: a) the spine fixation system of claim 5, b) a rod bending device (40) , which is configured to bend the rod (12) after it has been placed in or on the device at a desired longitudinal position, c) a computer (22) which is programmed to compute a desired shape of the rod (12) and to output a longitudinal symbol (24) that unambiguously identifies one of the longitudinal marks (30) provided on the rod.

The spine fixation installation system of claim 6, wherein the computer (22) is programmed to output a bending symbol (27) that identifies the bending angle by which the rod (12) shall be bent with the help of the rod bending device (40), and wherein the rod bending device (40) is capable to bend the rod by a bending angle that can be set by a user depending on the bending symbol (27) that has been output by the computer (22) .

The spine fixation installation system of claim 7, wherein the rod bending device (40) comprises a scale (56) or a display on which a quantity relat^¬ ing to the bending angle is indicated.

The spine fixation installation system of any of claims 6 to 8, wherein the computer (22) is programmed to output an angular symbol that identifies a desired angular position of the rod (12) that it shall have when it is placed in or on the rod bend^¬ ing device (40) before it is bent.

A method of bending a rod of a spine fixation sys^¬ tem, comprising the following steps: a) providing a rod (12) of any of claims 1 to 4 ; b) using a computer (22) that is programmed to compute a desired shape of the rod (12) and to output a longitudinal symbol (24) that unambiguously identifies one of the longitudinal marks (30) provided on the rod (12) ; c) placing the rod (12) in or on a rod bending device (40) at a longitudinal position such that the longitudinal mark (30) identified by the symbol (24) is located in a predetermined spatial relationship with respect to the rod bending device (40) ; d) bending the rod (12) .

The method of claim 10, wherein in step a) a rod of any of claims 3 or 4 is provided, the computer used in step b) is programmed to output an angular symbol that unambiguously identifies one of the angular marks (70) pro^¬ vided on the rod (12), and wherein in step c) the rod is placed in or on the rod bending device (40) such that the angular mark (70) identified by the symbol is located in a predetermined spatial relationship with respect to the rod bending device (40). e method of claim 10 or 11, wherein the computer used in step b) is programmed to output a bending symbol (27) that identifies the bending angle by which the rod (12) shall be bent with the help of the rod bending de^¬ vice (40), and wherein step d) the rod (12) is bent using the rod bending device (40) by the bending angle, thereby using a scale (56) or a display of the rod bending device (40) on which a quan^¬ tity related the bending angle is indicated.