WO1992000702A1

WO1992000702A1 - Stereotaxis system for surgery of the rachis

Info

Publication number: WO1992000702A1
Application number: PCT/ES1991/000040
Authority: WO
Inventors: J. Ricardo Dejoz
Original assignee: Comercial Envisa, S.L.
Priority date: 1990-07-04
Filing date: 1991-07-04
Publication date: 1992-01-23
Also published as: ES2025894A6

Abstract

Stereotaxis system for surgery of the rachis which allows to localise and approach anatomical points and comprising a mechanical device having three and two degrees of freedom for displacement, in the first place, longitudinally, transversally and in elevation with respect to the operation table and, in the second place, a rotation with respect to the sagittal plane and a final introduction towards the target point which the surgeon wants to operate. To this effect, and in order to localise the point of intervention, the system uses sights adaptable to the X ray apparatus and which allow to determine with high precision the spatial coordinates of the target point which is desired to be operated.

Description

Stereotaxy system for spinal surgery. The object of the present invention is a system that helps the surgeon in percutaneous interventions. This system is called stereotaxic because it allows access with total precision to a surgical point located over an anatomical area by means of the three-dimensional reconstruction of the same and leads to the construction of an apparatus that will be handled by specialists in this type of surgery. . The stereotaxy system conceived will reduce the level of specialization required by surgeons who intervene herniated discs or other interventions suspected of being treated percutaneously, while minimizing radioscopic exposure times, both of the patient and the doctor, during these interventions .

The final design covers two basic objectives, on the one hand, its mechanical simplicity, associated with a functional dimensioning with strictly rational tolerances, will facilitate its machining and reduce manufacturing costs. Furthermore, operational simplicity alcan¬ Zada avoid typical resistance ^'to medical equipment utiliza¬ tion novel conception.

The spine is a structure that combines the stiffness necessary to support the standing body weight while protecting the delicate spinal cord and spinal nerves while possessing the flexibility demanded by the usual movements in humans (flexion , extension and torsion). It is formed by a series of vertebrae articulated with each other by intervertebral discs.

A spine is divided into four zones: cervical, thoracic, lumbar and sacral, consisting of 7, 12, 5 and 5 vertebrae, respectively. Each intervertebral disc is constituted by three parts, two cartilaginous end plates, upper and lower, an outer part of hard but flexible tissue, called a fibrous ring and a softer inner one called the nucleus pulposus. The cartilaginous plates have a millimeter of periphery, being somewhat thinner in their central part, they bind the bone to the fibrous ring through a dense matrix of collagen fibers.

The fibrous ring consists of concentric layers of collagen fibers. The fibers of each layer are parallel to each other and surround the axis of the spiral disk, forming angles of 45 ^s with it.

The fibers arranged in adjacent layers form right angles to each other. With this arrangement a great resistance is achieved in the union of the vertebral bodies allowing the interlocking of the fibers the flexion and torsion of the disc, ensuring the resistance to breakage of the fibrous ring. The adjacent layers are separated by a gel rich in proteoglycans that transmits and unifies the pressure generated in the nucleus pulposus.

The nucleus pulposus is constituted by a semi-gelatinous tissue that retains about 80% water. Essentially it is a very hydrated mucopolysaccharide gel, wrapped by randomly distributed collagen fibrils. Under normal conditions, the fibrous ring and cartilaginous end plates, supported by adjacent bones, are rigid enough to resist core displacements.

The spinal cord is held in its position supported by muscles and ligaments. From it the roots of the nerves are born, as channels of communication between the brain and the rest of the organism. The study of aging processes of the spine and intervertebral discs has given rise to the -degenerative theory, which assumes that all vertebral columns degenerate over time. From this point of view, any medical or surgical treatment involves temporary pain relief and not total restoration to normal spinal behavior.

The protrusion disc herniation is called without passing the medullary canal of the nucleus pulposus through the radial cracks that appear in the fibrous ring. There is a tendency to displacement of the nucleus due to the forces acting on it. Although the end plates and the ring are strong enough to prevent these displacements, a protrusion of the core through the most weakened parts of the disk finally appears on the disk. The protrusion usually appears on the back of the ring, which is not only the thinnest, but also the least firmly attached to the bone. In some cases, the protrusion is lateral or anterolateral and, only in a small percentage of occasions, is it anterior.

The protrusion of the nucleus through the ring is due to a combination of mechanical and biochemical phenomena of a degenerative nature, such as the progressive loss of water and proteoglycans from the nucleus. The fact that the herniated disc does not only have its origin in the mechanical overloads of the spine is confirmed by the fact that it has not been possible to reproduce, by compression of the cartilaginous plates ter. corpses, the type of herniated disc that - and observed in patients.

The intervention of a damaged intervertebral disc consists in the partial or total suppression of the nucleus pulposus of said disc, whose protrusion is causing compression of the nerve roots with - the consequent pain that results from it. There are several alternative techniques:

- Open surgery surgery with laminectomy or hemilaminectonia. Within this group we will include microsurgery.

- Percutaneous surgery:

- Percutaneous nucleotomy.

- Chemonucleosis The percentage of successes measured as pain relief is similar in all three methods. The last two techniques have the advantage, over open-pit surgery of methods that almost do not involve surgical risk. Both nucleotomy and chemo-nucleosis are being increasingly used in the face of open surgery since they are less aggressive, reduce the operating room time, reduce the period of hospitalization, reduce convalescence time and demand only local anesthesia. All intervention techniques are conditioned by the difficulty of reaching through the bone ends (apophysis ^" ) of the vertebrae to the nucleus that will be intervened, taking into account the delicate structures located in the vicinity.

Open surgery is performed when the purpose of the operation is to perform a wide exploration of the spinal canal at several intervertebral levels, or when the patient or the pathology is not adequate to perform a nucleotomy / chemo-nucleosis. The technique consists in resecting, totally or partially, the vertebral plate, until obtaining access to the part of the disc where the nucleus pulposus protrudes. Next, the disk fragments are carefully extracted. Having removed one bone portion, a second intervention may be necessary to stabilize the spine by spinal fusion (arthrodesis).

Percutaneous nucleotomy is based on the introduction through a small skin incision of a nucleotome 2 millimeters in diameter to reach the nucleus pulposus. Manual guidance in the introduction of the nucleotome, bypassing the bony processes, is performed by radioscopic control of the spine in two planes, vertical (anteroposterior) and horizontal (transverse or lateral), so that its observation allows the area to be reconstructed three-dimensionally. The introduction of the nucleotome requires its longi¬ tudinal axis angles form between 45 ^and 55 ^s with the sagittal plane so that in its advance not find the transverse apófi¬ sis.

Once the target point has been reached, the nucleotome performs its function consisting of cutting the nuclear material by guillotining between two concentric cylinders with advance and retraction of the interior and simultaneous aspiration of said material.

Chemucleucleosis consists ^" in the introduction of a needle into the nucleus pulposus, and once it has been reached, an enzyme chemopapain from papaya latex is injected, it is a proteolytic enzyme that catalyzes the hydrolysis of the nucleus matrix Octopus until dissolved.

Currently, chemo-nucleosis is considered as the least invasive lumbar disc herniation intervention technique with the least risk and cost.

A stereotaxy system is nothing more than a mechanical design that allows to determine the coordinates in space (x, y, z) of an anatomical point on which it is desired to act (surgery, stimulation, infiltration, etc.) taking this point as center of a casque- spherical te that is defined by the mechanical system itself.

Consequently, the use of a stereotaxy system is developed in two successive stages: -I ^a stage: Determination of the coordinates of the anatomical point on which it is desired to act.

2 - stage: Generation of a mechanism that describes the surface of a spherical cap whose center coincides with the previously located anatomical point. The systems of spatial location of a point start from the stereophotogrammetry technique developed by Hindmarsh (1973), its adaptation to the medical field for localization of internal anatomical points was developed by Bro n (1.973) giving rise to the biplanar radiography technique.

If we try to set a coordinate system with millimeter strips, radiograph the area in which the point to be located is located and measure the position of the point on the radiograph with the help of the strips that would appear on the radiograph we would make an error because strips and the point to be located are not in the same plane and, since the X-ray tube is a point source, the image would have suffered a conical distortion. Conventional stereotaxy equipment operating as described has two drawbacks:

- Part of the machining must be effected by EDM and subsequent filling of the holes of the millimeter by a radio-opaque material such as lead. In addition to the difficult machining, the thicknesses of lead must be very well adjusted in order to ensure the sharpness of the radiographic image. The complication of machining is such that the costs of manufacturing the strips involve approximate- mind 50% of the total manufacturing costs of the equipment.

If the stereotaxy system is used during a surgical intervention, the need to perform mathematical calculations in the middle of it, both due to time problems and the possibility of incurring measurement or calculation errors, significantly hinders it.

These limitations have led to the use of stereotaxy systems that have been limited mainly to brain surgery. A stereotaxy mechanical equipment for brain surgery has a very high cost.

The high final commercial cost of these equipment prevents the application of existing stereotaxy systems in the market to a field such as herniated disc interventions, because, badly there are 3 surgical techniques that solve this pathology. To alleviate all these problems, the stereotaxy system developed in this patent, allows access of an instrument with total precision and quickly, to the target point limiting the use of X-rays to the previous phase of spatial location of the target, reducing therefore the radiation exposure time in addition to the degree of specialization necessary.

As indicated in previous paragraphs, in addition to the use in the treatment of herniated discs, the system designed to optimize other surgical processes, one of them may be to obtain biopsy samples in vertebral bodies at the dorsal level. In this location the technique requires a high degree of accuracy since the access road is limited on one side by the spinal cord and in the other by the pleural leaf.

Other anatomical areas also require a high degree of accuracy in the approach. One of them is the neck of the femur, the access to which, for percutaneously obtaining biopsy pieces can be definitely facilitated with this system.

In short, the usefulness of this development is not limited to spinal surgery; its flexibility makes it a completely open system and can be used by other specialties such as general surgery, urology, gynecology, etc.

In order to more easily understand the design of the developed stereotaxy system, annexes to this report are attached showing:

Figures 1 and 2 show a scheme of the developed stereotaxy system.

Figures 3 and 4 respectively show a perspective view partially sectioned and with the fixing and sliding mechanism (22) perpendicular to its direction of action, for a better understanding of the total assembly; and a projection in profile.

The stereotaxy system proposed here is based on the fact that the location of a point in space requires, at a minimum, the taking of two images in two different planes (usually perpendicular) in which, in addition to the target point, a known reference system. Each of these images confirms that said point is in the line perpendicular to the image plane, which passes through the projection of the real point on this plane. The spatial inter¬ section of two of these lines at different normally perpendicular angles determines the X, Y, Z coordinates of the point in question to which it calls. oars target point of target.

Since the location of the objective point from two images requires the determination of only three degrees of freedom, the described process will generally associate a geometric error, since it over-determines the spatial situation of that point. The geometric error made depends on the radiographic equipment given the conicity with which the object under analysis is irradiated, the precision in the auxiliary reference system and the relative position of the two images. The geometric location error of the cut point of the two lines is smaller when the images are made in planes perpendicular to each other.

The operating rooms in which these interventions are performed have an image intensifying X-ray system. This equipment allows a continuous image of the desired area to be obtained on a monitor. The plane on which the image is obtained can be modified at will by simple movements of the intensifier. Thanks to this, its use in obtaining two images perpendicular to each other of the affected area is extremely simple.

The use of the image intensifier is the starting point for the correct placement of the stereotaxy equipment. With the individual in the prone or lateral recumbency position, these two planes must be, preferably the lateral and the anteropos¬ior.

With the help of the technique described above, the surgeon manages to locate a specific point of the stereotaxy system (an x-ray image will appear on the x-ray image, which will be the result of the superposition of at least two consecutive points or a linear piece projected longitudinally) in a relative position relative to the target point (default by design). This is simple to achieve since the equipment is equipped with three degrees of freedom (following the coordinates X, Y, Z), as shown in Figure 1. The stereotaxy system is equipped with a pointing mechanism to base of view to achieve its alignment with the objective point (thus specifying its coordinates X, Y, Z). The mechanical system can move continuously and observe these movements with the image intensifier, observing on the screen the displacement of the horizontal references of the equipment established to specify the X, Y coordinates under horizontal (lateral) radiological projection. until the coincidence of those with the target point; in a second moment, and under vertical radiological projection (or perpendicular to the previous one), the vertical references of the system will be matched with the target point, thus specifying the Z coordinate. The equipment will be correctly positioned when the aiming points appear the superimposed objective point, both in the horizontal and vertical projection. In this way we have managed to match the center 0 "(zero) of the spherical cap shown in Figure 2, with the target point. Once the design position has been achieved With respect to 0, the surgeon can anchor the three kinematic pairs B, C and D of Figure 1. From here, exposure to radiation X is no longer necessary since the relative position A-0 is fixed and does not depend on the anthropometric characteristics of the subject being intervened.

Suppose now that in A a system has been arranged that allows moving the point "a" of the mobile segment ab over a spherical surface, centered at point 0 and radius the distance 0A, and that It is designed in such a way that segment ab always points towards point 0. To allow this type of movement it is necessary to place a type II kinematic pair (2 degrees of freedom) from point A, as outlined in the figure 2.

In order to approach a surgical intervention with the stereotaxy system of this patent, we would proceed, under horizontal radiolδgical projection (lateral or transverse), to the sliding of the bar (1), along the guide (2) belonging to the lateral of the table of interventions, and the ascent or descent of the bar (4) (and therefore of the sights 8 and 8 '), until the superposition or alignment of the target point to intervene, on the sights 8 and 8' (thus we managed to match the X and Y coordinates of the line that joins 8 and 8'which, by design, are the same as those of the center 0 (zero) of the spherical cap (figure 2), with the X and Y coordinates of the target point ; the ascent or descent of 8 and 8 'is in solidarity with the same movement of the bar (4), for being connected to (10) and (4).

This location of the point to intervene is achieved by sliding on the side (X coordinate) of the bar (1), and the height displacement (Y coordinate) of the bar (4) with the help of a radioscopic control which will determine in the previous screen lateral (horizontal) irradiation, the point that we intend to locate and on which it is desired to intervene, superimposing on it the sights 8 and 8 ^' (Figure 3 and 4), first with a displacement lateral (X), and then with a displacement in height (Y), and all this under radioscopic control. In this way and once the objective is located in a plane, the locks are fixed in the form of levers or screws (5) and (6) that will prevent lateral movement (axis X), and the lock (11) that ^' will prevent movement in height (Y axis). Since it is a question of determining a point in space, we need a third coordinate of the Z, so we will proceed to observe with the image intensifier the point to intervene through a view (3 and 3 ^' ), which they move horizontally in depth (Z coordinate) by means of a guide (Gn) that circulates through the dovetail (9), located in the bar (4). Therefore, the bar (4) will slide horizontally in depth (Z axis) along the part (10), until the point to intervene is shown on the screen of the image intensifier super¬ placed with the references vertical (3 and 3 ^' ) that have moved until they coincide in the image with the target point; with this we have managed to match the coordinate Z of the line that joins 3 and 3 ^' , and which in turn coincides with that of point 0 (zero) of the spherical cap of the figure (2), with the coordinate Z of the target point. At that time, the safety lock (7) that prevents the displacement of the bar (4) will be fixed, with the Z coordinate being set. The X, Y, Z coordinates of the target point will be obtained.

For a perfect location of the point to intervene, the movements have been made using the adjusters (12, 13, 14) that act along the length, width and height of the operating table, initially manually, although they will be susceptible to Be motorized. Once the target point has been perfectly determined and these three degrees of freedom have been fixed, the use of the X-ray system becomes unnecessary, thus avoiding the dangerous exposure of the patient and the surgeon since the surgical instrument to be introduced through of the guide at all times will remain in the direction of the target point, regardless of the mobilization of the introduction guide (segment ab of figures 1 and 2) at any of the constituent points of a spherical cap (figure 2), taking into account the type II kinematic torque model, represented in figure 2.

In this term, we will proceed to act on the two degrees of freedom that we had not yet considered, with which a turn will be made in a more or less wide range of degrees, depending on the specific use, in reference to the Sagittal plane of the arc (15) that describes a rotation around the axis A _j (figure 3) and is fixed with the lock (16). The piece 15 (and, therefore, the 17 guide 28 fixed thereto), it is possible to rotate it around the axis A2 » ^with 1 ° which is configured the second degree of freedom of the kinematic pair of type II represented in figure 2, and commented above. From this moment the bar (17) can rise or fall following the direction of the radius of the arc (15), and be fixed to it by the safety (23). After that, the instrument is introduced (needle, clamp, nucleotome, cannula, trocar, etc.) (18), necessary for the intervention.

The locks (19 and 20) respectively fix the rotation on the A axis of the arc (15), and the instrument holder (28) or guide for the penetration of the instrument to be introduced, (which is interchangeable depending on the type of intervention To make).

The fixing and sliding mechanisms act directly on the sprockets (14, 13 and 12), or with eccentrics, sliding by means of sprockets that act on a rack system (25), as well as on the dovetails of the bars (1 and 4) respectively, on which two zippers have been installed. The Zippers will be capable of being replaced by another system, such as endless screws.

If in the introduction of the surgical instrument (18) that is to reach the target point, it makes contact with an obstacle, for example with a bone process, a slight variation of the last two degrees of freedom (both simultaneously) or only one of them), first removing the instrument (18) and subsequently varying the angulation slightly on the A axis, and / or A „again by introducing the surgical instrument through a different point on the skin penetrating later, and unfailingly, towards the target point.

The equipment is essentially formed by a series of basic parts, defined above, designed to allow easy disassembly. The zipper sliding system allows fine adjustments of great precision while the fixing means are constituted by parts without edges and clean and ergonomic design.

Finally, mention that the sliding and fixing devices of the three and two degrees of freedom can be carried out manually as in the description previously made or by incorporating electric motors to the movement mechanisms provided with the corresponding remote control, whereby the The surgeon will avoid even short exposure to scattered or reflected X radiation that occurs at the time of system adjustment.

Obviously, these and other improvements may be included in the object here recommended, which has been represented exclusively on a representative and non-limiting basis. Describe sufficiently the nature of the pre I set up an invention, as well as a way of putting it into practice, we only have to add that as a whole and its component parts it is possible to introduce changes in shape, materials, layout, as long as these alterations do not substantially vary the characteristics of the invention that are claimed.

Finally, to say that in the process of specifying the coordinates of the target point the order of the projections can be altered, initially carrying out a vertical radiological projection, in which the X, Z coordinates of the target point will be specified by proceeding to the superimposition in the radiological image of the target point on sights 3 and 3 'through the movement along the table of interventions -guide 2- (coordinate X), and horizontally in depth of bar 4 (coordinate Z ). Subsequently, the Y coordinate will be concretized, under lateral radiological projection (horizontal), locating in the image the Puntodiana that you want to access surgically, on which the sights 8 and 8 'must be superimposed, which will be done by shifting in height (ascent - descent) bar 4 until the three points (8, 8 'and target point) coincide.

During the process of concreting the coordinates, even if the movements are not motorized, the upper members of the surgeon are not directly exposed to the X irradiation, since the displacement wheels on which the hands of the operator will act are found far from the flow of X-rays.

Claims

1.- Stereotaxy system for spinal surgery, which allows the location and approach of anatomical point and which is materialized in a mechanical device that behaves three and two degrees of freedom with which it moves, first, to the length, width and height of the operating table, and secondly, a rotation around the horizontal axis (movement in the vertical plane) and around the vertical axis (movement in the horizontal plane), and a final introduction towards the target point on which you want to act; It is also characterized in that, for the location of the point to intervene, it uses perpendicularly arranged sights, adaptable to the X-ray apparatus, image intensifier, which allow to accurately determine the spatial coordinates of the target point "U" on which it is desired to intervene.

2.- Stereotaxy system for spinal surgery,