Abstract:
A positioning device ( 1 ) for placing a prosthesis device ( 2 ) in a spinal column of a living mammal, including at least one holding device ( 6 ) for cooperation with the prosthesis device and for guiding thereof during positioning, wherein it includes fixing means ( 7 ) for fixation with respect to at least one vertebra ( 3,3 ′), and said fixing means includes locking means ( 9 ), which in a first, free state, allows adjustment movement of said holding means ( 6 ) and thereby of the prosthesis device ( 2 ), and in a second, locked state, fixes said holding device ( 6 ) and thereby the prosthesis device ( 2 ) in a selected position. The invention also concerns a system.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention concerns a positioning device according to the preamble of claim  1  and a system for engagement with vertebrae in a spinal column including such a positioning device. 
       BACKGROUND OF THE INVENTION 
       [0002]    For patients diagnosed disc degeneration, surgical operations are performed more and more often for released troubles. The most common operation for these patients today is still fusion, where an ossified connection of the vertebrae is obtained. Also metallic connection devices can be used. The movability then ceases between the vertebrae in question but the patient will become free from pain. As the patient becomes more active and movable, the segments above and below the fused region will, however, be subjected to greater strains. The risk of new symptoms from surrounding segments thereby increases. 
         [0003]    As an alternative to fusion, disc implants have been presented. A known disc prosthesis generally consists of two mutually articulated plates that are positioned between two vertebrae instead of the disc. The positioning of a disc implant results in eliminating the disc that causes pain, reinstating the distance between the vertebrae and reinstating movability between them. 
         [0004]    In order to obtain sufficient certainty against a disc implant over time moving in an undesired manner from the intended position between two vertebrae, the two mutually articulated plates of a previously known prosthesis are provided with different kinds of projecting engagement means such as fin-shaped elements, pointed elements, pins and like plural projections for the engagement with the meeting surfaces of the vertebrae. 
         [0005]    The operative method that is used for inserting a disc implant requires positioning of the prosthesis from the abdomen side in order to allow access to the vertebral column from the front. The disc to be replaced is cleared out, whereby the vertebrae are drawn apart with the aid of tension pliers. 
         [0006]    After using possible instruments shaping grooves in the surfaces of vertebrae for the cooperation with possible projecting protrusions for the purpose of achieving a correct position for the disc prosthesis, the latter is now to be positioned. 
         [0007]    According to today&#39;s methods, this is achieved by applying the prosthesis on a holder and hammering it in with great force between the vertebrae, guided by the prepared grooves. This step in the operation is very problematic, since the vertebrae tend to be drawn of fall against each other and then it will often be difficult to even bring in the prosthesis between the vertebrae. For this reason the hammering risks to be very violent. 
         [0008]    When the prosthesis is finally positioned, which is verified with X-ray radioscopy, said tension pliers are used in order to again span apart the vertebrae and thereby the disc plates of the prosthesis in order to be able to position a joint detail between these plates. Also this step is troublesome and sometimes laborious. 
         [0009]    When using prostheses that are completely assembled with the joint detail, this second step is not necessary. Such prostheses are, however, thicker and yet more troublesome to position between the vertebrae. Sometimes, unfortunately, damages to the vertebrae will occur during the positioning of the prosthesis. Such damages can be serious and have serious consequences. For that reason, the surgical operation puts great demands on the skill and experience of the surgeon. 
         [0010]    When, finally, everything is place, the operation is terminated and final X-ray is made. Not very seldom it can then be discovered that the disc prosthesis is not correctly positioned in such a way that it is not placed exactly on the middle line or in any other way is not in a proper position. The possibilities of adjusting the position are at this stage almost none. 
         [0011]    Since the disc prosthesis rests on the brittle covering plate of the vertebra, the prosthesis must have maximal size in order to support on a relatively strong peripheral rim of the vertebra. Exact positioning is therefore very essential. Patient having osteoporosis are therefore often disqualified for this type of surgical operation depending on lack of congruence between the parts of the disc prosthesis and the vertebra. 
         [0012]    Incorrect position results in risk of uncontrolled separation and repositioning of the vertebrae. 
       AIM AND MOST IMPORTANT FEATURES OF THE INVENTION 
       [0013]    It is an aim of the present invention to provide a positioning device of the kind mentioned initially and a system which makes it possible to eliminate or at least reduce the problems of the background art. 
         [0014]    These aims are achieved in a positioning device according to the above through the features of the characterizing portion of claim  1 . The corresponding advantages are obtained in a system device according to claim  18 . 
         [0015]    Hereby it is achieved that when spanning apart of the vertebrae in a spinal column, a prosthesis device, such as for example a disc prosthesis or a vertebral prosthesis, can be correctly positioned with respect to at least one vertebra when vertebrae are spanned apart, so that, when the separation is ended, the prosthesis is indeed in the right position. X-ray radioscopy can be used in connection with adjusting the holder means in order to assist the surgeon during the positioning. The invention is, however, not limited to this method but also other corresponding methods for this are possible to use, such as for example translucence with NMR-camera, magnet camera. Also other fluoroscopy and positioning indication methods can be used. 
         [0016]    When the vertebrae are released against the prosthesis device, through X-ray radioscopy or the like it can be verified that the final position of the prosthesis device also is the desired position. In the event this is not the case, there is a real possibility of repositioning the prosthesis device after a renewed spanning part of the vertebrae also if it is considered to be less likely that this would be necessary if the positioning is made accurately from the beginning. 
         [0017]    After a verified correct positioning, the holding device is released from the prosthesis device, whereafter the used spanning device can be removed permanently. Altogether, the positioning device according to the invention allows essentially more secure and further, more easily handled equipment, which also can be used in a patient-friendly manner with minimized risks of injuries to the patient when it is used. 
         [0018]    By providing two fixing elements outgoing from different engagement positions and which are mutually lockable, satisfactory stability is obtained and positioning security after possibility of adjustment. 
         [0019]    By providing a universal joint, which is lockable/releasable through said locking means, great positioning freedom is provided. 
         [0020]    In particular, it is preferred that the positioning device according to the invention includes distance means in order over connection portions to carry engagement means that are constructed for engagement with two vertebrae at a distance from each other. Hereby the prosthesis device is positioned with respect to these vertebrae, which are preferably located on either side of the operation point. 
         [0021]    In particular, it is preferred that said distance means are arranged such that they are capable of changing the degree of separation of said vertebrae when the engagement means are in engagement therewith. Hereby, in the positioning device, the means for spanning apart the vertebrae are integrated which is a considerable advantage, since the arrangement for spanning apart hereby can be constructed optimally for its use to function as a mechanism for spanning apart and further as the base for the fixing means. Greater freedom when removing the old, damaged disc is also achieved. With previously known technology, the tooling for holding apart the vertebrae comprises an obstacle making it difficult to evacuate the old, damaged disc. This process is time consuming and positioning of a disc implant is more difficult. The integrated aspect of this invention essentially simplifies clearing out of the damaged disc, whereby the entire operation is facilitated and speeded up, resulting in a safer operation. The possibility of spanning apart, which is provided according to this aspect of the invention, makes it possible to freely remove the old disc. 
         [0022]    The positioning of the holding means will thereby be very stable and no further engagement points, besides the ones belonging to the mechanism for spanning apart, that is the distance means, are necessary. The number of operation points in the patient in the form of holes for screws or the like can thereby be limited to a minimum. 
         [0023]    Said distance means preferably include two distance means arranged in parallel carrying the engagement means. The adjustment and handling of the holding means and the prosthesis carried thereon hereby takes place between these parallel arranged distance means. The fixing means are suitably comprised of elongate elements, that are arranged on the distance means and are fixable thereon, which in a common crossing point are lockable, which results in a very stable fixation. The crossing point between these elements is preferably also the starting point for a locking means, which in its locked position fixes the holding means. Preferably the locking means in said locked position also locks the fixing elements in said crossing point. 
         [0024]    By providing the fixing elements with each one slotted portion in their free regions, in the free state, sideways adjustment of the crossing point is allowed with respect to the operation point, which can be desirable for providing an accurate positioning of the prosthesis device in its rotational direction. 
         [0025]    It is previously known to use so called retractors in the kind of surgical operation of the present type in order to hold the soft parts in the abdomen from the operation point. A system according to the invention includes and preferably carries support devices for that purpose. By fastening them to the distance means, they contribute in an optimal manner to hold the abdomen wall pressed down and the operation field free. The clearing out of the old disc is also simplified with these means. 
         [0026]    Corresponding advantages are achieved in a system according to claim  18  and the dependant system claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0027]    The invention will now be described by way of embodiments and with reference to the annexed drawings, wherein: 
           [0028]      FIG. 1  shows a positioning device according to the invention during the process of introducing an implant in a spinal column, partly in section, 
           [0029]      FIG. 2  shows the positioning device in  FIG. 1  in a perspective view, 
           [0030]      FIG. 3  shows the positioning device in  FIGS. 1 and 2  in a separate perspective view, 
           [0031]      FIG. 4  shows the positioning device according to the invention with some details removed for the sake of clarity, and 
           [0032]      FIGS. 5   a  and  b  show in different views a holding device for the use with a device according to the invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0033]      FIG. 1  shows a positioning device  1  in the process of positioning a disc implant  2  between two vertebrae  3  and  3 ′ in a spinal column of a living human being. With  5  are indicated two healthy discs, whereas between the vertebrae  3  and  3 ′ is cleared out all material from a damaged disc to be replaced by said disc implant  2 . 
         [0034]    The disc implant  2  is held by a holding device  6  including a fork-shaped head  10 , which releasably grips around the disc implant  2  and a rod shaped manipulating element  11  which can be manipulated by hand by a surgeon. 
         [0000]    In the embodiment shown in  FIG. 1 , the manipulating element  11  is controlled by a fixing means  7 , which in turn is connected to the distance device  8  (only one shown on  FIG. 1 ), which in turn over engagement means in the form of screws, (indicated with dash dotted lines, and with numerals  4  and  4 ′), is in engagement with two vertebrae  3 ,  3 ′. 
         [0035]    The fixing means  7  includes fixing elements  12  (only one shown in  FIG. 1 ) together with a universal joint  9 ′ which is lockable by means of a locking means  9 , wherein the universal joint  9 ′ in a first, free state allows an adjustment movement including rotations and displacements of the holding means  6  and thereby for the disc implant  2 . In a second, locked position, the locking means  9  locks the universal joint  9 ′ and thereby the holding device  6  and thereby the disc implant  2  in a chosen position. 
         [0036]    As is indicated by arrows P 1 -P 6 , essentially total freedom of movement is achieved with the shown embodiment with three linear degrees of freedom P 1 -P 3  and three rotational degrees of freedom P 4 -P 6  for the holding device  6 . It should be noted that freedom of movement in the length direction of the distance device  8  is obtained by displacement of the fixing element  12  relative thereto. Locking of the locking means  9  can suitably be arranged by means of a smaller rotation of the fixing element  12  with respect of the distance device  8  and thereby friction locking of these elements with respect of each other. 
         [0037]    The function of the spanning device of the arrangement is such that the distance device  8  is extendable in the length direction by displacement in such a way that the engagement elements, which thus have been brought to engagement with two vertebrae, because of the extension will cause a change of the degree of separation between these vertebrae  3  and  3 ′ with respect to each other. 
         [0038]    This way the vertebrae can be separated and the space between them be cleared out so that the disc implant  2  without resistance can be inserted between the vertebrae  3  and  3 ′, accurately be positioned by the surgeon supported by simultaneous X-ray radioscopy until an optimal positioning of the disc implant  2  has been reached. Thereafter the holding device  6  is locked and thereby the prosthesis device in the chosen position with the aid of the fixing means  7 , whereafter the distance device  8  is manipulated in such a way that the distance between its outer ends reduces and thereby the vertebrae  3  and  3 ′ come closer to each other until they come into contact against the outer plates of the disc implant  2 . Thereafter a final control is made, by means of X-ray radioscopy or the like, that the disc implant  2  is indeed accurately positioned 
         [0039]    If that should not be the case, the degree of separation is again increased between the vertebrae  3  and  3 ′ and the disc implant  2  is repositioned. When accurate positioning has been reached, the holding device  6  is removed from the disc implant  2 , whereafter the distance device  8  and its engagement means  4  and  4 ′ can be removed from the engagement with the vertebrae. 
         [0040]    In  FIG. 2 , the positioning device  1  is represented in a perspective view in about the same position as is shown in  FIG. 1 . Hereby is shown that the spanning device belonging to the positioning device  1  includes two sideways separated distance means  8  and  8 ′, which are position such that it between them is a sufficiently great space for introducing a disc implant (not shown in  FIG. 2 ), which is carried by a fork head  10  of a holding device  6 . 
         [0041]    From each one of the distance means  8  and  8 ′, extents fixing elements  12  and  12 ′, which are longitudinally displaceable on the respectively means  8  and  8 ′ through sleeve portions  19 . The fixing elements  12  and  12 ′ are united in a crossing point, wherein a locking device  9  engages. The locking device  9  activates and deactivates also a universal joint  9 ′, which carries the manipulating element  11  of the holding device  6 . 
         [0042]    In the fixing means  12  and  12 ′ are arranged longitudinal, elongate through slots  20  and  20 ′, in which a bolt belonging to the locking means  9  can run. This way, in a free state of the locking means, it is possible to displace the locking device and the universal joint  9 ′ in height as well as sideways by side displacement of the locking device and the universal joint with respect to the operation point between the vertebrae  3  and  3 ′. 
         [0043]    Further, the distance devices  8  and  8 ′ are telescopic and thus axially displaceable in order to allow an increased separation of those vertebrae, with which they are in engagement. In the shown example, the distance means  8  and  8 ′ are not in engagement with two adjacent vertebrae, but with a first vertebra  3 ′ and a second vertebra  3 ″, whereas a third vertebra  3  is between these vertebrae. This arrangement allows better space at the place of operation. 
         [0044]    Spanning apart the distance devices are made with a pliers device  18 , which forces apart two telescopic parts  15 ′ and  14 ′ belonging to the distance device  8 ′. For fixing of an obtained separation position, a locking ring  16 ′ is used, which locks against the smaller one of the telescopic parts  15 ′ by means of a locking screw  17 . In practice, the spanning apart of the vertebrae are made through step-wise manipulating of the pliers device  18  on first the one on the distance devices a smaller step, locking thereof, thereafter spanning apart of the second distance device a smaller distance, locking thereof etc. etc. 
         [0045]    In  FIG. 3 , the device of  FIG. 2  is shown in a different perspective and freed from a spinal column. The distance devices  8  and  8 ′ have at their ends per se known joint devices for cooperation with the engagement means  4 ,  4 ′, which are comprised of per se known skeleton screws. By the engagement means being articulately fastened to the distance devices, excess breaking forces onto the vertebra are avoided in connection with spanning-apart the spinal column. The positioning of the screws  4 ,  4 ′ are made in those parts of vertebrae that are least porous, and thereby best resist the forces for spanning apart. 
         [0046]    On  FIG. 3  are also shown two supporting elements  21  and  21 ′, preferably lockable and slightly curved, which are arranged for cooperation with (not shown) supporting plates for free holding the operation point from body organs in connection with the surgical operation. 
         [0047]    In  FIG. 4  are shown essential parts of the positioning according to the invention with some details removed. 
         [0048]    A holding device  6  is shown in  FIG. 5   a  and  b . The holding device  6  includes a fork-shaped head  10  with fork shanks  10 ′ and  10 ″, which from an engagement position, where they with the aid of the engagement means  24  engage with a disc implant, can be brought to a position where the disc implant is released. This is achieved by the normally curved element  23  between the fork shanks  24 , by means of an actuating means  22  in the form of an element inside the rod shape manoeuvring element  11 , is brought to a straightened state, where it presses apart the fork shanks  24 . See interrupted arrows in  FIG. 5   b . The actuating means  22  can be manipulated by hand by a surgeon through a press button outermost on the means  22 . The head  10  is preferably made of a plastic material in one piece in such a way that in an unloaded condition, it is in a position for engagement and with a bent element  23 . 
         [0049]    It should be noted that the invention can be modified within the scope of the claims. The shown embodiment with the positioning device thus directly cooperating with a spanning device in the form of distance means is preferred. However, it is not excluded that the positioning device is separate from the spanning device, and in that case it is arranged such that the fixing means are fastened otherwise to one or a plurality of vertebrae. This is, however, not desired, since it means that further operations with holes etc. in the spinal column have to be made. It, however, makes it possible to use another type of spanning device for separating the vertebrae than the one that is described and shown here. 
         [0050]    In order to arrange that a greater space is provided between two distance devices, the attachments of the engagement means can be positioned sideways outwardly, so that the distance devices can be positioned sideways with respect of the axes of the engagement means. 
         [0051]    A modification of the spanning device can have one single distance device, which provides spanning apart instead of two that are shown in the Figures. At the ends, this single distance device can have sideward angled portions for cooperation at different positions after their lengths with typically each two engagement means that are engaged with the vertebrae so that the spanning device will have a shallow U-shaped construction with the distance device as web and the sideward angled portions as the shanks of the U. In this case positioning, as an example, may need to be arranged on the one hand on the only distance device, on the other hand on a fixed point on a vertebra. 
         [0052]    The arrangement between the distance device (devices) and the engagements means can be different, for example, the arrangement with three independent joints for allowing movements: 1: in a plane parallel with the axis of the distance device, 2: in a plane at right angle to the axis of the distance device, 3: in a plane at right angle against the axis of the engagement means (screw). Independent locking of these joints results in possibility of changing the angles of the screws, also under load, which gives greater possibilities of influencing the positions and the parallelism of the vertebrae. 
         [0053]    The fixing means can in that and other cases be constructed otherwise, thus include portions for cooperation directly with a vertebra. Also other kinds of arrangements for locking the holding means can be envisaged, for example with a locking device arranged at the fastening point of the fixing means on the spanning device or on the vertebra itself. It is also possible to have other types of locking and a plurality of separate locks for movements in different directions instead of the integrated lock shown in the Figures. The distance devices can be manipulated otherwise, for example by screwing, with a notched rod with possibly spring loaded locking device, or with a leaver mechanism. 
         [0054]    In a simply handled modification, the distance device is manoeuvred with the aid of an adjustment cable, such as a “Bowden cable”, which can have its fastenings on engagement portions on mutually movable parts of a distance device in a manner which is per se obvious for the person skilled in the art. This way spanning apart of two vertebrae is initiated from a distance from the area of spanning apart, which is an advantages, since it enhances control and accessibility. Also other arrangements such as with pawl and rack and corresponding, actuating means with hydraulics or with pneumatics can be used for spanning apart. 
         [0055]    It shall be noted that it is not excluded that other prostheses are positioned with a device according to the invention, for example vertebra prostheses.