Untitled record

ES 2 371 634 T3

DESCRIPTION

Unique Anterior Cervical Locking Plate System

1. Technical Field of the Invention

The invention relates to a plate system adapted for use in the human anterior cervical spine to contact the anterior pons of at least two cervical vertebral bodies. Therefore, the present invention relates generally to implants and instruments for the fusion of the cervical human spine from the anterior pons and, in particular, to plate systems for aligning and holding the cervical vertebrae adjacent in spatial relationship. selected during vertebral fusion of these vertebrae.

1. Description of related techniques

US-A-5 531 746 (the preamble of claim 1 is based on this document) discloses a posterior cervical implant assembly for holding adjacent vertebrae immobilized by fixation to posterior surfaces thereof, comprising an elongated plate, having at least two through holes arranged in spaced relationship with respect to each other along a longitudinal axis thereof; a series of coupling elements each of which has a hemispherical interior volume and each of said coupling elements being insertable in a corresponding through hole, as well as a series of bone holes, each of said bone screws having a hemispherical head part and a stem, said stem being insertable through the corresponding through hole into the orifice of the vertebra and said hemispherical head being mounted with free rotation capability within the hemispherical inner volume within the coupling element before insertion and in such a way that the screw stem bone screw and coupling element can be inserted into a corresponding through hole and said bone screw shaft can be inserted into the lateral mass at a selected angle within a predetermined range of angles, including non-perpendicular angles with respect to the plate and thereby locking said coupling element and said hemispherical head with said plate at said selected angle when said hemispherical head and said coupling element are forced to advance into said corresponding through hole.

It is common practice in this technique to use cervical plate placement systems for the indicated purpose. These systems are essentially made up of plates and screws to align and hold the vertebrae in a desired position relative to each other. The earliest of these devices consisted of stainless steel plates and screws and required the screws to pass completely through the vertebrae into the spinal canal in order to engage the strong bony tissues (posterior cortex) of the vertebral bodies. This required the ability to observe or visualize this area radiographically, which is not always possible, especially in the part of the lower cervical spine where the vertebrae may be radiographically hidden by the action of the shoulders.

In order to form holes in the vertebral bodies for the insertion of each of the screws, a drilling operation was carried out followed by a tapping operation. Each of these operations involved the passage of an instrument completely through the associated vertebral body, passing into the spine. Therefore, these instruments come in close proximity to the spinal cord and dural sac which are in close proximity to the posterior surfaces of the vertebral bodies. Any procedure that introduces an object into the spinal canal presents serious risks that are a concern to the surgeon.

The conventional technique of forming a bone screw receiving hole in vertebral bodies by drilling has a number of significant disadvantages. For example, drilling removes bone material, leaving a gap and resulting in loss of bone material. Drilling also causes microfractures of the bone at the interface between the drill and the bone, and the resulting fracture lines tend to propagate in directions perpendicular to the wall of the hole. More specifically, the bone material is essentially a type of ceramic that exhibits a brittle fracture pattern in its formation and propagation in response to drilling. In addition, drilling generates heat, which can result in thermal necrosis of the bone material, precisely at the interface between the bone and the screw that has been installed next, with the necrosis being very damaging. Any bone that experiences necrosis will subsequently be reabsorbed by the body as part of the bone repair process and this can lead to screw loosening.

Another problem with drilling is that the trajectory of the bit is difficult to control and since the bit works by rotation, it can project soft tissue around the associated plate. Furthermore, except with great care, the drill bit can be driven significantly beyond the posterior cortex, causing irreparable damage within the spinal canal. Finally, a drill bit can bend and break within the vertebral body and

ES 2 371 634 T3 can then cause serious damage, since the part of the drill that is still rotating enters the wound, while the part of the drill that has broken can protrude dangerously from the vertebral body or can break at the level of the upper surface of said body, so that it will be irretrievably inserted into it. In any case, the maneuvers that have to be performed to retrieve the broken part of the drill bit will inevitably prolong and complicate the surgical process.

In known plate placement systems, problems have arisen due to loosening and failure of the elements used, breakage of the screws and plates, and passage of the screws into the throat area of ​​the patient. These events generally require other surgical procedures to replace the broken parts of the plates and screws completely, and repair any damage that may have been caused.

Other problems that have arisen with known systems are the result of the failure of the screws to achieve sufficient insertion into the bone and the disappearance of the thread threading of the screw.

Also the use of known plating systems can result in a loss of lordosis, which is the normal curve in the cervical spine viewed laterally.

Known plating systems further experience problems in connection with procedures in which bone grafts are placed between vertebral bodies to achieve interbody fusion that is healed by a process called "creeping substitution". In this process, the bone at the interface between the graft and the vertebrae is eliminated by a biological process that involves the production of powerful acids and enzymes, as a prelude to the invasion of the interface by living tissue and the deposit or growth of new bone. While the plates allow for proper alignment of the vertebrae and their rigid fixation, they can therefore, at the same time and unfortunately, retain the separated vertebrae, while in the resorption phase of the slow replacement process a few interstices in the bone at the fusion site, with the result that the desired fusion does not take place. This failure is known as pseudoarthrosis. When this failure occurs, the used elements or hardware frequently break or become detached from the spine, thus requiring another surgical procedure to remove the components that have broken and an additional surgical procedure to retry the fusion.

In response to the problems that have been described, a second generation of plating systems have been developed and / or proposed. These include the system disclosed in US Patent Nos. 5,364,399 to Lowery and 5,423,826 to Morscher, as well as the SYNTHES Spine Cervical Spine Locking and Plating Systems, the DANEK ORION Plate. , the CODMAN SHURTLEFF plate and the SMITH NEPHEW RICHARDS plate, among others. The training elements of this second generation systems have a number of common characteristics. All of them are made of a titanium or pure titanium alloy instead of stainless steel, to minimize adverse reactions of the tissues and are also compatible with MRI, which is not the case with stainless steel. Screws and plates have been given extra thickness for added strength. The screws have larger diameters to improve their anchoring without requiring that they engage the posterior cortex of the vertebral bodies. Gentle longitudinal contouring of the plates is used to allow some lordosis, and / or limited transverse contouring to better follow the general curved shape of the front of the vertebral bodies. Mechanisms are used to secure the screws of the vertebral bones to their associated plates, in a way that prevents the screws from escaping. While this second generation of plate placement systems represents a significant improvement over previous systems, some problems still persist, while new ones have been created.

For example, since the screws no longer extend into the posterior cortex, it is common for the threads of the threaded screw holes to loosen and for the screws to fail to anchor properly. Furthermore, screw breakage continues to be experienced and takes place in a very common way at the attachment of the screw to the rear profile of the plate. The screws used in both the SYNTHES System and the SMITH NEPHEW RICHARDS System are especially vulnerable to this problem because these screws are hollow at the level where they engage the plate to allow internal reception of the locking screws.

In an attempt to prevent screw breakage at the screw-to-plate junction, newer screw designs have a larger bottom diameter from tip to head, resulting thus far in a smooth and blunt thread, almost unusable, close to the screw head with low holding power and little tactile feedback to the surgeon to signal the completion of the tightening before the screw shifts into the bone. Based on empirical studies to test these prior art screws, it has been found that the use of a pre-threaded hole was preferable to a self-tapping screw to improve pull-out strength, and therefore these screws have not been proven. been self-tapping type, so the screw holes must be pre-threaded. Since the cutting part of the thread of a tap is necessarily sharp and must rotate to do its job, there is a serious risk of damage to the surrounding soft tissue when it is used. This is combined with the fact that the plates used in these systems do not provide a long enough axis profile to fully allow lordosis and do not have a sufficient transverse contour to prevent the edge of the plate around its longitudinal axis, adapting to

ES 2 371 634 T3 anterior shape of the vertebral bodies, so that these plates do not prevent the soft tissues from penetrating from the sides and below the screw holes, thus exposing these tissues to damage due to the action of the drill and the tap. While it is possible, at the time of surgery, to make certain changes to the shape profile of these plates, this is generally limited to contouring the longitudinal axis and very frequently causes distortion of the bone screw holes in the plate. and the screw holes in the plate joints, such that it has an adverse effect on the screw and plate coupling. The lack of proper contouring prevents these plates from having an optimally low profile with respect to the spine.

In some second-generation cervical plate placement systems, cases of screw leakage continue to occur, because these plates could not be designed to allow all screws to be locked. Specifically, while the designers of these plates have recognized the importance of bone screw fixation to the plates, they have been unable to lock all the screws and have had to settle for leaving some of the screws unlocked.

In addition, some of these second-generation systems use small, delicate “watch” parts to achieve interconnection. These parts are characterized by the need to attach them with especially delicate small-tip screwdrivers. These interconnecting components are easily rendered ineffective by any effort to alter the contours of a plate during surgery.

Despite the improvement of these second generation plating systems over the first mentioned problems, the problems still persist, the most important of which is pseudarthrosis, and particularly diversion pseudoarthrosis ("distraction pseudoarthroses"). While these second generation plaques have clearly led to an increased rate of fusion, when fusion generation failure occurs, it is generally accompanied by resorption of bone along a line at the junction. from the graft to the vertebra, which can be seen on an x-ray.

In the case of first generation weak plates and screws, the plates can retain the vertebrae separated, preventing fusion, but only until the mechanical elements or hardware break, overcoming the deflection and then allowing fusion to take place. Second generation plating systems are too strong to allow this to occur, thus requiring other surgical procedures for correction of the nonunion.

Compression plates are well known and widely used in orthopedic surgery for the stabilization of tubular bones and in some cases also of flat bones. These plates can be based on certain means of external compression or they can be of the self-compression type, based on the ability of the screw head to slide within a slot with ramp, such that the tightening of the bone screws through the of the plate imparts a linear motion perpendicular to the bolt axes. US Patent No. 5,180,381 discloses an attempt to use this mechanism in connection with anterior spinal fixation.

However, it has been observed that all the self-compression-type plate systems that have been proposed have in common the need for a screw that is coupled to both the proximal and distal cortex, (bone envelope of a very dense bone material ), in order to anchor the screw tip in such a way as to allow the plate to move relative to the screw when tightening rather than allowing the plate to move the screw off-axis. However, as explained earlier in this description, when a screw has to be engaged in the posterior cortex of the vertebral body, it is necessary that the drill and the tap that forms the screw hole, as well as the tip of the screw itself. screw, enter the spinal canal, thereby exposing the spinal cord to damage.

While the system disclosed in US Patent No. 5,180,381 avoids this danger by engaging the vertebral body end plate instead of the posterior vertebral body cortex, the screw path is necessarily very short, so that there is very little opportunity for the screw to be threaded for additional anchorage within a vertebral body. It seemed, therefore, that to the extent that the device disclosed in US Patent No. 5,180,380 is capable of achieving the stated objectives, it would pull the front of the spine to a greater extent than the posterior part and would not appear to compress the posterior part of the vertebral bodies at all, thus producing an undesirable iatrogenic loss of normal cervical lordosis. This situation alters the normal biomechanics of the cervical spine and is potentially very dangerous.

Creating compression between adjacent vertebrae would offer a number of advantages, including reduced deviation pseudoarthrosis, increased surface area of ​​contact between the graft and vertebrae as slightly non-corresponding surfaces are forced against each other, greater osteogenic stimulation, given that compression loads stimulate bone formation, and increased fusion graft, as well as greater stability of the spinal segment.

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Among the new problems created by these second generation systems is the tendency for the small “clockwork” pieces used to lock the bone screws to the plates to fall out of the screwdriver used for their fixation or to fall off the legs. associated and lost in the wound. Furthermore, these small pieces are very fragile and require additional specialized instruments for insertion and / or manipulation. In addition, improper placement of a bone screw relative to the axis of the plate hole can make the screw locking mechanism impractical or can lead to the formation of sharp titanium chips when a locking screw is inserted in contact with a screw. for bones that have been improperly attached. The means of establishing alignment of the bone screw with the hole in the plate and its preparation are unreliable. Furthermore, most of these second generation systems do not have efficient and reliable means for positioning and holding the plate during docking.

Specific characteristics of different prior art systems will be summarized below.

The system disclosed in US Patents No. 5,364,399 and No. 5,423,826, which have been cited earlier in this description, comprises a thin stainless steel plate that allows the placement of a side-offset bicortical screw. on the side, whose plate has a combination of screw holes and slots.

The “Acromed” system comprises a titanium plate and screws that require bicortical screw placement. This system does not comprise locking means for the bone screws.

The system disclosed in US Patent No. 5,180,381 comprises an "H" shaped plate having a combination of ramp slots and a hole that requires bicortical placement of a screw at a 45 ° angle with with respect to the plane of the plate. This patent discloses that this angular positioning is intended for the purpose of producing compression.

The SYNTHES Morscher plate system uses slotted, hollow screw heads. The screws are positioned unicortically so that the heads, when properly aligned, rest on top of the holes in the plate. The top of each screw is internally threaded to receive a small screw that is threaded into the bone screw head to increase interference fit between the bone screw head and the associated plate hole wall.

In the system disclosed in US Patent Nos. 5,364,399 and 5,423,826, pairs of unicortical bone screws are used that can be locked in place by both ends of the associated plate, by means of lag screws. lock that have a small diameter shank and a large head. At each end of a plate, two bone screws can be locked in place by a single locking screw that is located between the bone screws. In general, the plate is provided, between its two ends, with a diagonal groove or grooves to receive one or more additional screws, each of the additional screws being fixable in a bone graft or a corresponding vertebra, which is tensioned by the plate. There is no locking screw associated with these intermediate bone screws to lock the bone screws to the plate.

The Codman Shurtleff plate system uses the side of a pre-assembled rivet that has a rotating head to press against the side of the head of a bone screw to secure the screw to the plate. The plates of this system are also provided with holes to receive intermediate screws, but these screws are not associated with any locking means.

While the designers of the last mentioned systems have recognized the importance of locking the bone screws in place on the associated plates, they have not provided locking of the intermediate bone screws in their associated holes.

In an early version of the Codman Shurtleff system, the locking system was a lever pivoting around a stem that passes completely through the plate, and then flares to retain the stem within the plate. The lever was rotated after the bone screw had been inserted to engage the head of the bone screw and thereby fix the bone screw to the plate.

Based on a consideration of the characteristics of all known cervical plating systems, it appears that there is still a need for an improved system having the following combination of characteristics:

1) The plate must be strong enough to carry out the intended function without mechanical failure;

2) The plate must be preformed in three dimensions, in order to adapt anatomically both in the longitudinal plane and in the transverse plane to the anterior cervical spine;

3) The plate should be constructed so that all of the bone screws are generally perpendicular to the plate when viewed from the side, but the screw pairs are highly

ES 2 371 634 T3 converging corresponding to any vertebral level when viewed from the bottom or from the end;

4) Each pair of screws engages the corresponding vertebrae and the high convergence of screws in one pair allows the length of the screws that engage the bone to be longer, still remaining within the vertebra, and providing a more secure and secure engagement. tough with vertebrae;

5) The system must comprise bone screws capable of achieving greater anchorage within the bone of the vertebral body, and without the need to penetrate the posterior vertebral cortex and enter the vertebral canal;

6) A self-tapping screw should be used, thus eliminating the need for separate threading stages;

7) A reliable means must be provided for docking and maneuvering the plate during installation;

8) The plate must be matable with an instrument that can reliably produce bone screw holes that are coaxial with the plate screw holes;

9) It should be possible to prepare the vertebral bone to receive the bone screws, in order to produce a stronger connection and less risk of passing the thread by means of a pilot hole punch that creates a pilot hole for the screws for bones;

10) As an alternative to using a punch for a pilot hole, a relatively small diameter drill (compared to the overall bottom diameter of the screw) should be used in order to create the pilot hole;

11) Means must be provided for locking each and every bone screw in relative position with respect to the plate, and the locking means must be of sufficient size and strength to carry out the intended functions;

12) The bone screw locking means should preferably be capable of being retained by the plate prior to insertion of the bone screw or should be reliably engageable with a screwdriver to prevent small parts from loosening in the wound; Y

13) The system must be able to carry out compression of the vertebral segments to be fused, simultaneously maintaining and re-establishing lordosis.

OBJECTIVES OF THE INVENTION

It is an object of the present invention to provide an improved anterior cervical plate system that exhibits the characteristics described above and that avoids many of the drawbacks of previously known systems.

Another object of the invention is to provide an anterior cervical plate system that allows intersegmental compression of the vertebral segment (compression of the adjacent vertebrae and the fusion graft in the disc space between the adjacent vertebrae) in case of lordosis, and similarly, if desired, in multi-segment compression.

Another object of the invention is to provide a plate constructed to be reliably coupled to an instrument to form all bone screw holes coaxial with the holes formed in the plate, the instrument having integral depth limiting means that they completely limit the danger of perforation of the posterior vertebral wall or entry into the vertebral canal.

Another object of the invention is to provide a system in which the bone screws and locking mechanisms, once installed, have a low profile.

The stated objectives, as well as other objectives and characteristics of the invention will be more clearly understood from the following description of preferred embodiments of the invention, which is provided with reference to the attached drawings which show embodiments of the invention only by way of non-limiting example. .

CHARACTERISTICS OF THE INVENTION

The present invention provides a plate system having the features of claim 1. Other embodiments of the invention are described in the dependent claims.

The plate system of the invention comprises a plate that is of sufficient length to cover a disc space and to overlap, at least in part, at least, with two adjacent cervical vertebrae, with a substantial portion of the lower surface of the plate being preferably biconcave, that is, concavely curved along a substantial portion of the longitudinal axis of the plate and concavely curved along a substantial portion of the transverse axis of the plate. The lower surface of the plate may also be textured and / or treated to induce bone growth along the lower surface of the plate that makes contact with the cervical vertebrae. The plate is provided with a series of bone screw receiving holes that pass through the plate from the upper surface to the lower surface of the plate and at least one locking element is associated with the bone screw receiving hole. The board and its component parts may be

ES 2 371 634 T3 made of any implant quality material suitable for use in the human body, and the plate and associated components can be made of a bioabsorbable material.

The bone screws are each insertable in the respective bone screw receiving holes for the purpose of coupling the plate to a vertebra. A locking element can be coupled to a receiving recess in the locking element and has a shaped head for locking the bone screws in the plate.

In the present invention, a locking member engages within a corresponding bone screw receiving hole to lock a corresponding bone screw in place. In accordance with this second embodiment of the invention, each of the bone screws is locked in the plate by means of a single locking element that contacts at least a part of the bone screw. Since it is not necessary to form other holes in the plate to fix the locking elements on the plate, the plate is very strong.

The locking elements can take multiple forms to achieve the desired objective such as, without limitation, screws, threaded caps, rivets, set screws, projecting elements and the like.

Also, a new bone screw is disclosed to prevent the screw from exiting or removing during use. This is achieved by a design that includes a screw in which the external diameter or ridge diameter of the thread is kept substantially constant along the entire length of the bone screw axis, from under the head to the tip, in which threads with a smaller external diameter facilitate insertion. The screw tip has a slot at its distal end to make it self-tapping. The thread also has an extremely thin and sharp profile for cutting spinal bone material, preserving bone integrity.

The plating system does not require that the bone screw head be hollow, or that additional holes be placed through the plate in addition to those provided for the passage of the bone screws. It will be noted that the bone screws weaken when their heads are hollow and that the plates weaken when they are provided with additional holes.

Additionally, the plate of the above systems allows for proper alignment of the plate holes for the bone screws and for the plate to be easily applied to the vertebrae in a compression action. The plates comprise appropriate grooves and coupling means for the coupling of compression instruments, which are described in detail below, to apply a compressive force between adjacent vertebrae to which the plate is attached, easily and reliably.

An improved locking screw driver is disclosed. The driver provides a wedging interference with a recess in the head of the bone screws and the head of the locking elements. The same driver can be used for both bone screws and locking elements. The drive device ensures that the locking element cannot fall from the drive device, getting lost in the wound. The driver has a tapered end to facilitate insertion into the complementary recess in the screw head and is used to engage and collect the locking elements. Alternatively, the receiving housing can be conical for the same purpose.

Alternatively, a combination of the bone screw and locking screw driver is disclosed in which the bone screw driver passes through a longitudinal opening in the locking screw driver, so that the bone screw driver passes through a longitudinal opening in the locking screw driver. that the bone screw and the locking screw can be loaded prior to insertion of the bone screw and both can be tightened with an instrument without removing it from position.

Also, instruments are disclosed for forming pilot holes to aid in the ease and precision of bone screws and to create a compressive force between adjacent vertebrae during plate installation and to retain the plate during installation.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments according to Figures 1-46, 60-62, 70-79, 83-84E are not part of the invention.

Figure 1 is a perspective view, from the top, of a first embodiment of a multiple locking plate of the spine in the cervical part.

Figure 2 is a top plan view of the cervical spine multiple locking plate shown in Figure 1.

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Figure 3 is a side elevational view of the cervical spine multiple locking plate shown in Figure 1.

Figure 4 is an end view of the cervical spine multiple locking plate shown in Figure 1.

Figure 5 is a bottom plan view of the cervical spine multiple locking plate shown in Figure 1.

Figure 6 is a top plan view of the cervical spine multiple locking plate shown in Figures 1-5, with locking elements mounted in an open configuration.

Figure 7 is a top plan view of a modification of the plate of Figures 1-6 with a four bone screw locking element in place.

Figure 8 is a top plan view of another embodiment of a cervical locking plate, according to Figure 1, with an elongated central slot for greater compression capacity.

Figure 9 is a top plan view of a non-inventive locking element for use with the plates of Figures 1-6.

Figure 10 is a top plan view of a block element to be used with the central opening of the plate of Figures 7 and 22.

Figure 11 is a top plan view of a locking cap for use in the end openings shown in Figures 1, 6 and 7.

Figure 12 is a side elevation view of the locking element of Figure 16.

Figure 13 is a side elevation view of another embodiment of the locking element of Figure 16.

Figure 14 is a top perspective view of an alternative embodiment of a cervical spine multiple locking plate for use with locking rivets.

Figure 15 is a bottom plan view of the cervical spine multiple locking plate of Figure 14.

Figure 16 is a top plan view of a two bone screw locking element.

Figure 17 is a top plan view of an alterative embodiment of a four bone screw locking element having head slots to achieve greater flexibility of the locking tabs.

Figure 18 is a top plan view of a rivet-type locking element to be used with the central opening of the plate of Figure 14.

Figure 19 is a side elevational view of a rivet locking element that does not correspond to the present invention.

Figure 20 is a top perspective view of the bottom of the head of the rivet of Figure 19, viewed from lines 20-20.

Figure 21 is a top perspective view of the head portion of a three bone screw locking element.

Figure 22 is a top perspective view of a third embodiment of the cervical spine multiple locking plate utilizing threaded cap-shaped locking elements.

Figure 23 is a side elevation view of a locking element that does not correspond to the present invention, to be used with the plate of Figure 22.

Figure 24A is a side elevational view of a bone screw in accordance with the present invention.

Figure 24B is an enlarged side elevational view of a bone screw of Figure 24A.

Figure 25 is a side elevational view of an alternate embodiment of a bone screw in accordance with the present invention.

Figure 26 is a bottom end view of the bone screw shown in Figure 24A.

Figure 27 is an end top view of the bone screw shown in Figure 24A.

Figure 28 is a top perspective view of a fourth embodiment of a multiple block cervical spine plate.

Figure 29 is a top perspective view of a locking element to be used with the plate of Figure 28.

Figure 30 is a partial side sectional view of the plate of Figure 28, along lines 30-30, with a bone screw in place.

Figure 31 is a top perspective view of the plate of Figure 1, positioned against the anterior profile of three successive vertebral bodies in the cervical spine, a plate holder, and an instrument for forming bone screw receptor holes. in the vertebral bodies.

Figure 32 is a cross-sectional view of a portion of the bone-forming device, shown in Figure 31, taken along lines 32-32.

Figure 33 is a side elevational view, in partial cross section, showing a compression station tool and compression station coupled thereto for insertion into a vertebral body.

Figure 34 is a partial sectional side elevation view of the compression post tool engaged for dismounting of the compression post from the vertebral body.

Figure 35 is an end view of the bottom of the compression station tool of Figure 34. Figure 36 is a side elevation view of a plate engaging hook for use with the compression apparatus shown in Figure 38.

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Figure 37 is a sectional view of the plate of an alternative hole forming instrument in the form of a drill guide and drill bit for use during the plate installation process.

Figure 38 is a side elevational view showing intersegmental spine compression and a compression apparatus.

Figure 39 is a view similar to that of Figure 38 showing the compression apparatus in another stage of the plate installation process.

Figure 40 is a top perspective view showing locking of the plate bone screws.

Figure 41 is a partial side sectional view of a locking element attached to a positioning instrument.

Figure 42 is a partial sectional side view of another embodiment of the locking element attached to the delivery instrument.

Figure 43 is a partial sectional view showing a cervical plate, locking element, and bone screws taken along lines 43-43 of Figure 40.

Figure 44 is an enlarged portion of a detail along line 44 of Figure 43.

Figure 45 is a partial sectional side view of a plate holder attached to a plate.

Figure 46 is a partial cross-sectional side view of another plate holder attached to a plate.

Figure 47 is a top perspective view of a first embodiment of a single lock plate. Figure 48 is a top plan view of the plate shown in Figure 47.

Figure 49 is a side elevational view of the plate shown in Figure 47.

Figure 50 is an end view of the plate shown in Figure 47.

Figure 51 is a bottom view of the plate shown in Figure 47.

Figure 52 is a top plan view of the plate shown in Figure 47 with locking elements in place.

Figure 53 is a side elevational view of a bone screw used with the plate shown in Figure 47.

Figure 54 is a top plan view of the bone screw shown in Figure 53.

Figure 55 is a view of the lower end of the bone screw of Figure 53.

Figure 56 is a top plan view of a locking cap for use with a single locking plate according to Figure 47.

Figure 57 is a side elevational view of the locking cap shown in Figure 56.

Figure 58 is a bottom plan view of the locking cap shown in Figures 56 and 57.

Figure 59 is a bottom perspective view of the locking cap of Figures 56-58.

Figure 60 is a top perspective view of the individual locking plate of Figure 47 shown in its retention by the plate support against three vertebral bodies, with the hole forming instrument for punching a pilot hole in the bodies. vertebral bones to receive a bone screw.

Figure 61 is a partially cutaway side elevational view of the hole forming instrument threaded to a bone screw receiving hole.

Figure 62 is a perspective side sectional view of the drill bit and drill guide threadedly attached to the plate for drilling a hole in a bone screw insert.

Figure 63 is a top perspective view of a single locking plate installed along a segment of the spinal column with two locking caps installed in two bone screw receiving holes.

Figure 64 is a partially sectional side elevational view of a locking cap coupled to a driver to install the locking cap.

Figure 65 is a partial sectional view of the plate, bone screws, and locking caps, taken along line 65-65 of Figure 63.

Figure 66 is an enlarged partial view of area 66 of Figure 65.

Figure 67 is a perspective view of a cervical locking plate retained by an alternative plate support instrument.

Figure 68 is an end sectional view showing a plate holder of Figure 67 coupled to a plate.

Figure 69A is an end sectional view of an alternate embodiment of the plate holder.

Figure 69B is an end sectional view of another alternate embodiment of the plate holder.

Figure 70 is a plate support instrument with an offset and removable handle.

Figure 71 is a top perspective view of a second embodiment of a single cervical locking plate with individual locking elements for locking each of the bone screws.

Figure 72 is a top perspective view of a threaded locking element for use with the individual cervical locking plate of Figure 71.

Figure 73 is a partial side sectional view of the plate of Figure 71 viewed along lines 73-73 with the locking element of Figure 72 in place to retain a bone screw, but not fully tensioned .

Figure 74 is a top perspective view of an alternative locking element for use by a first modification of the individual cervical locking plate of Figure 71.

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Figure 75 is a side sectional view of the first modification of the plate of Figure 71 with the locking element of Figure 74.

Figure 76 is a perspective view of an alternative locking element for use with the first modification of the plate of Figure 71.

Figure 77 is a partial side sectional view of the first modification of the plate of Figure 71 with the locking element of Figure 76 in place.

Figure 78 is a top perspective view of another alternative locking element in the form of a rivet for use with a second modification of the locking plate of Figure 71.

Figure 79 is a detailed side partial sectional view of the plate of Figure 71 modified to use a locking element, according to Figure 78, shown in place.

Figure 80 is a partial sectional view of a bone screw and plate, showing the end of a tool for use in inserting the bone screws and locking caps.

Figure 81 is a side elevational view of another embodiment of the tool of Figure 80.

Figure 83 is a further embodiment of a Cervical Spine Multiple Locking Plate for use in stabilizing multiple spinal segments.

Figures 84A-84E are various embodiments of multiple cervical spine locking plates to be used in stabilizing a single segment of the spine.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention will first be described in association with a plate system, in which a series of bone screws are locked in place with a locking element. This is what is referred to as a multi-lock plate system. The multiple locking plates will be described, then the locking elements to lock the bone screws in the plate, then the bone screws associated with the multiple locking plates, and finally the instrumentation and method of mounting the plates. multiple lock. Thereafter, plate systems in which a single locking element locks a single bone screw will be described. This is what is referred to as a single plate locking system. The bone screw locking elements, instruments, and installation method associated with the individual locking plate will be explained below.

1. Multiple locking plate system (not part of the invention)

The preferred embodiment of the multiple locking anterior cervical locking plate 2 according to the present invention (shown by way of example for use at fusion level two (three adjacent vertebrae)) is shown in Figures 1-5. The plate 2 has a generally elongated shape, the outline of which deviates from the rectangular due to the presence of lobes or lateral projections 4 at the corners and in the center of the sides of the plate 2. Each lobe 4 has a rounded profile and contains a receiving hole 6 for the respective circular bone screw. Two additional receiving holes 8 of the intermediate circular bone screw are located on the inside of the sides of plate 2 and are centered on the longitudinal axis of plate 2. The lobes 4 provide plate 2 with additional strength in the area that surrounds each receiving hole 6 of the bone screw. It is recognized that other shapes may be used for plate 2.

Intermediate rigged bone screw receptor holes 8 are used for level two (three vertebra) fusion. The intermediate bone screw receiving holes 8 can be dispensed with in a single fusion level (two vertebrae), or said additional intermediate bone screw receiving holes 8 can be added if the additional levels are to be fused.

The plate 2 is further provided with three locking element holes 12, each of which is internally threaded 3 in the preferred embodiment and each of which is surrounded by a shallow recessed zone 14. As will be described in more detail below in the preferred embodiment, the bone screws are inserted into the bone screw receiving holes and a single pre-installed locking element associated with each of the holes 12 of the locking element. , locks a series of bone screws 30 at once in position in one go.

The number of paired bone screw holes generally corresponds to the number of vertebrae to be fused. A plate for one level of fusion could, however, have a single locking element hole 12, whereas plates for fusion of more than two levels (three vertebrae), could have additional intermediate locking element holes 12 corresponding to additional rigged bone screw holes. In the embodiment shown in Figures 1-6, each of the end locking elements 20 will lock the three bone screws 30 in the appropriate place, while the locking screw 21 of the central locking hole 12 locks the two screws to 30 bones in place. As shown in Figure 7, the central locking element 25 can also be configured so that four bone screws 30 are locked at one time.

ES 2 371 634 T3

As specifically shown in Figures 3, 4 and 5, plate 2 is shaped so that its bottom surface 27 (surface that will be in contact with the vertebral bodies) has biconcave curvature, being concave both in the longitudinal plane (corresponding to its length) and in the plane transverse to it, corresponding to its width. The concave curvature in the longitudinal plane conforms to the appropriate shape of the anterior profile of the spine with the vertebra aligned in the appropriate lordosis. The longitudinal curve is an arc along the circumference of a circle (referred to in this description as "radius of curvature") of 15.0 cm to 30.0 cm radius and more preferably 20.0-25. , 0 cm radius. According to an end view in Figure 4, the plate 2 has a radius of curvature of a circle of radius 15-25 mm, preferably radius 19-21 mm. While the plate 2 may have a thickness between 2 and 3 mm, a thickness between 2.25 mm and 2.5 mm is preferred.

The lower surface 27 of plate 2 being contoured so as to be able to remain flush against the associated vertebral bodies is in contrast to conventional plates which have larger radii of curvature that contact the vertebral bodies only along the length. of the longitudinal axis of the plate, thus allowing side-to-side oscillation of the plate with respect to the vertebral bodies. The contour of the plate of the present invention provides effective resistance to the oscillation of the plate 2, with respect to the vertebral bodies about the longitudinal axis of the plate, thereby reducing the stress on the plate 2 and the screws. of bone 30, preventing soft tissue reattachment below the plate.

Other advantages brought about by the aforementioned curvature are that plate 2 will more closely conform to the opposite bone surface; plate 2 will extend from the spine for a short distance; soft tissues will be prevented from slipping under the edges of plate 2, where damage could occur; and the angle of the bone screws 30, perpendicular to the plate when viewed from the side, when installed, will be a substantially convergent angle, clamping the vertebral bone between the bone screws 30, and thereby more firmly anchoring the plate to the spine.

As seen in Figure 5, the lower surface 27 of plate 2 preferably has a porous, rough and / or textured surface layer and can be coated with, impregnated with or comprise fusion promoting substances (such as morphogenetic proteins for bones) in order to increase bone growth along the underside of plate 2, between vertebrae and vertebrae. The textured bottom surface 27 further provides a means for retaining fusion promoting substances with which the bottom surface layer 27 can be impregnated prior to installation. The lower surface 27 of the plate 2 can be provided with the desired porous textured shape by coarse blasting or other conventional technology, such as, for example, etching, plasma spraying, sintering and casting. If porous, the bottom surface 27 is formed such that it has a porosity or pore dimensions on the order of 50-500 microns, and preferably 100-300 microns. Fusion promoting substances with which the porous textured undersurface 27 is impregnated include, without limitation, bone morphogenetic proteins, hydroxyapatite, or hydroxyapatite tricalcium phosphate. The plate 2 may comprise, at least in part, a resorbable material that can be further impregnated with the bone growth material so that the plate 2 is resorbed by the patient's body, the bone growth material is released, thereby acting as well as a timing release mechanism. By forming plate 2 from a material that is resorbable and has a material that promotes bone growth present, the vertebrae are allowed to fuse in a more natural way since the plate becomes progressively less load bearing, preventing this mode a posterior protection by effort of the spine.

As further shown in Figures 4 and 5, at least one end of plate 2 has a recess 18 that can cooperate with the compression apparatus, described in detail below with reference to Figures 36 and 38.

Figure 6 is a top plan view of the plate 2 of Figure 1, with the locking elements 20, 21 inserted in the receiving holes of the locking element. In a preferred embodiment, the locking elements 20, 21 are in the form of screws that cooperate with the threaded interior 3 of the locking holes 12. Each of these locking elements 20, 21 is shown in its initial open orientation, in which the orientation of the cuts 22 in the head 23 of each locking element 20, 21 is directed so as to allow the insertion of the screws. for bones 30 into the receiving holes 6, 8 of the adjacent bone screw, without interference by the head 23 of the locking elements 20, 21. It will be appreciated that other configurations of the head 23 are possible in order to allow the insertion of bone screws into the adjacent bone screw receiving holes without interference by the head 23.

Figure 8 is a plan view of another embodiment of plate 2 of Figures 1-5, and is generally referred to as plate 120. Plate 120 is provided with an elongated slot 122 that extends longitudinally along its axis. longitudinal overlap over the intermediate locking hole 12. Elongated slot 122 allows for additional relative movement between plate 120 and a compression station 54 associated with a compression tool during the compression procedure, as described above.

ES 2 371 634 T3

Referring to Figures 14 and 15, an alternative embodiment of a multiple locking plate is shown referred to at 70. Plate 70 is provided, instead of threaded locking hole 12, with a central aperture 200 to receive a removable rivet 202, of the type shown in Figures 17-20. Figure 15 is a bottom plan view of plate 70 shown in Figure 14. The outline of plate 70 is the same as that of plate 2 shown in Figures 1-5. Rivet 202 is removable and fits within unthreaded opening 200, comparable to lock hole 12 and slot 122 described above. Other embodiments may use a rivet that is not removable, but is manufactured as part of the plate 70, as would be used in the end locking holes 19 of Figures 14 and 15.

Referring to Figure 22, another alternative embodiment of a multi-lock plate is shown, referred to at 230. Plate 230 uses threaded caps, such as the cap 300 shown in Figures 9 and 23, for a locking element, or preferably one having cuts such as described with the appearance in a top view similar to the locking element of Figures 10-11, for example. The central locking hole 602 has an elongated slot 234 to provide greater compressibility, as will be further described below.

Referring to Figures 10-13, there is shown a first embodiment of a locking element 20, 21, 25 in the form of locking screws, in accordance with the present invention, for use with plate 2. Figure 10 is a Top plan view showing the head 23 of the central locking element 25, shown in Figure 7. The stem 46 of the locking element 25 is threaded 47 to coincide with the threading 3 within the associated locking hole 12 of the plate 2 . As seen in FIG. 21, each segment 49 on each side of the cuts 22 of the locking element 21 has a support surface 48 formed on the bottom surface of the head 23 of the locking element. As shown in Figure 16, the head 23 of the locking element may be provided with two slots 42 to give flexibility to the head 23 of the locking element, to assist the locking element in its ability to move over the top. of the bone screw head 32 during the supporting action when the locking element is rotated. Alternatively, it is noted that the support surface can be sloped, wedge or cam shaped. The camber, wedge or camber features can also be used with other locking elements described in this document.

Referring to Figures 6 and 10-13, it will be noted that when the locking elements 20, 21 are rotated clockwise with respect to Figure 6, a respective support surface 48 will be directed toward the surface. curved top 39 of the respective bone screw head 32, in order to effectively lock the associated bone screws 30 and locking elements 20, 21 in place.

Alternatively, as shown in Figure 21, in place of a support surface 44, a wedge or ramp-shaped surface 44 may be used to increase the force applied to the head 32 of the bone screw. When in the locked position, the forward end of the inclined portion of the locking member should be lower than the projection of the bone screw head 32, so that more force is required to lift the locking member and loosen it than just enough for the locking element to remain firm and locked. However, the heads 23 of the locking member are not required to be slotted, cam-shaped, or have a sloped surface to lock the bone screw 30 in place. Elements of pressure, friction, interference or other coupling means capable of preventing the locking element from being displaced from its locking position can be used.

Rivet 202, shown in Figures 17-20, is intended for use in association with plate 70 shown in Figures 14-15, being shown in detail in section, in Figures 19 and 20. Rivet 202 has a head 204, a stem 206 and an elongated lower segment 208 for engagement within the corresponding opening 200 of plate 70. The lower surface 210 of the head 204 of the rivet 202 has an irregular surface that may have a cam structure, such as in the lower part of the locking element 20, 21, for engagement with the upper surface 39 of the head 32 of the screw to bones. For use in the end locking holes 19, the upper surface of the elongated lower segment 208 may have an irregular surface to cooperate with the irregular surface of the lower portion of the plate 70, to retain the rivet 202 in a locked position against the head 32 of the bone screw, as shown in FIG. 15. Although the rivet of Figure 18 is a separate and removable component with respect to the plate, the rivets, and particularly those intended for use with the end locking holes, can be formed as part of the plate during the manufacturing process. plate, and the rivet may be non-removable.

Each of the aforementioned embodiments provides a firm engagement of the locking element with respect to the bone screw 30 and the corresponding plate.

In the alternative embodiment of the multiple locking plate 23, shown in FIG. 22, the locking member may take the form of a threaded locking cap 300, which is shown in FIG. 23. The threaded locking cap 300 has a thread. 302 in its external circumference, corresponding to the thread 303 of the internal circumference of the recesses 304 of the locking element in the upper part of the plate 230, shown in Figure 22. The locking cap 300 is relatively thin, especially compared to its width.

ES 2 371 634 T3

The upper part 305 of the locking cap 300 is provided with a non-circular through hole 306 to receive a driving tool having the same configuration.

Referring to Figures 28, 29 and 30, another embodiment of the multiple locking plate is shown, indicated generally at 400, and a locking element in the form of a thin locking element 412. Plate 400 has an opening in its upper surface for insertion of the reduced thickness locking element 412, a recess 402 associated with each of the bone screw receiving holes 408 and a slot 410 in the side wall of the holes. 408 bone screw receivers to allow thinner locking element 412, which has a series of slender projections or blades 414, thinner than slot 410, which provide this locking element 412 with a helix-like appearance. The reduced thickness locking element 412 is capable of being rotated inside the plate, in order not to cover the bone screw holes, thus allowing said thin thickness locking element 412 to be pre-installed, prior to assembly. of the screws, by the surgeon. The limited rotation of the thin locking element 412 allows the blades 414 to protrude through the slot 410 and cover a portion of the upper area of ​​the associated bone screws 30. The blades 414 of said thin locking element 412 are flexible and, when rotated, slide over the upper surface 39 of the head of the bone screw 32 to lock the screw 30 in place. As with the other embodiments that have been discussed, each of the embodiments of the locking element is capable of locking more than one bone screw 30. It will be appreciated that different multiple locking plates and combinations of locking elements are capable of lock up to four bone screws simultaneously, but they are equally effective at locking fewer or no number, ie producing their own fixation to the plate

It will be observed that a characteristic of each of the embodiments of locking elements described above consists in having a coupling means for their actuation or drive, in these cases, for example, a recess 24 as large as the recess 34 of the bone screws 30, so that the same tool can be used for turning the screws 30 and the locking elements. Also, the locking elements are strong enough and have sufficient mass to support their locking without breakage.

All of the examples shown of the multiple locking elements, having a series of recessed areas or cuts, have an arc with a radius greater than that of the bone screw head. Furthermore, the head 23 of each of the locking elements 20, 21 is provided in its central part with a non-circular recess 24, such as the one shown in figure 9, which can be engaged by a manipulation tool appropriate, such as that shown in Figures 40-42. In the embodiment of the head 23 shown in Figure 9, the associated tool would have a hexagonal head, but other forms of recesses of the head 23 can be used. The threads of each locking hole 12 and each locking element 20, 21 have a close tolerance, so that it will reliably retain their orientations, allowing the insertion of bone screws 30 into the receiving holes 6, 8 of the bone screws, without interference.

It will be appreciated that while various forms of locking elements have been disclosed, with the description in mind, other equivalent elements may be used with the aim of locking the bone screws 30 in place. In Fig. 83, an alternative multi-type locking plate 990 is shown having additional bone screw receiving intermediate holes 980 and associated locking elements 960 for locking the bone locking screws 30 in place. Plate 990 allows for closer spacing and more bone screw holes than the number of vertebrae to be engaged.

Several plates 700a-g used for single-level fusion are shown in Figures 84A-84E. Each of these plates 700a-g is designed to extend to a segment of the spine, consisting of a disc space and two adjacent vertebrae (containing the bone graft), and have bone screws inserted into the end of the vertebrae through the screw receiving holes 6 associated with the two adjacent vertebrae and then locked in place. As shown in Figures 84A-84E, one locking element 710 or two locking elements can be used to lock four bone screws in place. In Figures 84A-84E, each of the plates 700a-e is shown with the locking elements in their open orientation, prior to their rotation to lock the bone screws.

Each of the previously described plates can have the same contour, generally biconcave, that has already been described to adapt to the anterior aspect of the spine.

Figures 24A and 24B provide a side view of one embodiment of bone screw 30. Figure 27 is a top view of bone screw 30. In the center of bone screw head 32 is a profiled recess 34 which it can have the same shape as the recess 24 of each of the locking elements 20, 21, in which case it can be rotated with the same tool used for the rotation of said locking elements 20, 21. It will be appreciated that the engaging portion of the bone screw driver 30 could have a slot, and could be male or female in structure (as shown).

ES 2 371 634 T3

In the embodiment of the bone screw 30 shown in Figures 24A and 24B, the screw head 32 is stepped, with the first lower head portion 35 contiguous with the screw shank 33, having a larger diameter. smaller than the top of the bone screw head 32. When this embodiment of the bone screw 30 is used, each of the screw receiving holes 6, 8 of the plate 2 has a recessed area 14 that conforms to the diameter of the top of the head 32 of the bone screw and that it is sized for interference coupling. The lower portion 35 of the bone screw head 32 is dimensioned to achieve interference engagement with its associated portion of the screw receiving holes 6, 8. The larger diameter upper portion of the bone screw head 32 ensures that the bone screw 30 cannot be fully displaced through the bone screw receiving holes 6, 8 of the plate 2. The bone screw 30 passes completely through the upper surface of plate 2, without engaging the upper surface in any way.

As shown in Figure 44, the head 32 of the screw 30 passes unobstructed through the upper surface of the plate, until the lower surface of the enlarged screw head 32 engages the upper face of the part. narrower bone screw receptor in the middle or below the middle of the plate. This arrangement is considered optimal to allow the greatest stability of the screw with respect to the plate, even in the absence of locking, against all forces except those inverse to the insertion path, while providing the greatest resistance of the plate below the head 23 of the bone screw. That is, since the plate is generally only 2-3 mm thick, a purely circumferential and vertical wall is the one that has the greatest capacity to restrict the movement of a screw, if the head is similarly configured and there is a low tolerance between the two elements. Placing the head support near the middle thickness of the plate is preferred as this allows the head to be large to receive the recess for the screwdriver or tool without undergoing weakening, simultaneously positioning the head support away from the surface. top of the plate to allow the screw head to be positioned deep within the plate. Placing the head support approximately halfway through the plate thickness ensures a significant amount of the plate material below the head for support purposes, while simultaneously providing adequate head length above and below the point of contact to prevent the contact point from acting as a fulcrum by providing adequate lever arms to prevent unwanted movement.

In the alternative embodiment of the bone screw 30 ', shown in FIG. 25, the head 32' of the bone screw is inclined in the direction from the top of the head 32 'of the bone screw towards the tip of the screw 36'. . Also in this case, the bone screw head 32 'is dimensioned to achieve interference engagement in the associated bone screw receiving hole 6, 8 when the bone screw 30' has been fully assembled. When using this embodiment of the bone screw 30 ', it is not necessary for the bone screw receiving holes 6, 8 to be provided with the recessed area 4.

In each of the above bone screw embodiments, the bone screws 30 and 30 'feature a unique combination of a conical screw shaft 33 and helical thread 31. The diameter of the screw shaft 33 generally increases from a distal portion of the stem near the tip 36 of the screw toward the proximal portion of the stem, near the head 32 of the screw. In the preferred embodiment, the rate of diameter increase is also greatest near the head 32 of the bone screw. This conformation avoids areas of increased stress and provides greater strength in the screw-plate joint, where it is required to a greater extent. The taper of the screw shank 33 may be concave in shape, as shown in FIG. 24A, or it may be linear. The distal portion of the screw shaft 33 can adopt a constant diameter.

Referring again to Figures 24A and 24B, the thread 31 of the bone screw 30 has a substantially constant outer diameter "d" or crest, from the proximal part of the shaft below the head 32 of the bone screw to the distal part. of the stem near the tip 36 of the bone screw. At the screw tip 36, the crest diameter of the thread 31 may preferably be reduced by one or two turns to facilitate insertion and penetration of the bone screw 30 into the bone.

In the preferred embodiment, the thread 31 of each bone screw 30 has an external diameter slightly less than the diameter of the lowermost portion 35 of the head 32 of the bone screw that is adjacent to the posterior or upper end of the associated thread 31. Furthermore, the thread 31 is relatively thin, in the direction of the longitudinal axis of the screw, and tapers outwardly and has a triangular cross section.

An example of the dimensions of a bone screw to be used in surgery of the human anterior cervical spine for insertion into the vertebrae is as follows: the threaded part of the screw has a length between approximately 10 mm and 22 mm (preferably 12 mm). -18mm) and a head length of about 1mm to 3mm (preferably 2-2.5mm). The threaded part must have a maximum outside diameter between approximately 3.6 and 5.2 mm (preferably 3.8-4.5 mm) and the head has a diameter between approximately 3.8 mm and 6 mm (preferably 4 -5.5 mm). The thread pitch is between approximately 1.25 mm and 2.5 mm (preferably 1.5-2.0 mm) and has a profile of

ES 2 371 634 T3 thin and sharp thread. The apex of the two faces of the thread is at an angle of less than about 21 degrees (preferably 15 degrees) and the base of the thread is less than about 0.60 mm thick (preferably 0.25 mm-0.35 mm). The screw has a diameter at the base that increases approximately above the tip of the shank, along the longitudinal axis to approximately below the head portion of the screw. Preferably, the tip of the screw is slotted through at least one recessed area in order to make the screw self-tapping.

Although the thread 31 of the bone screw 30 has a thin profile, the thread will nevertheless be stronger than the bone into which it is inserted, so that the thread will effectively cut a thin helical groove in bone tissue. The volume of bone that will be displaced by the thickness of the thread is minimized by the thin shape of the thread, however, the substantial diameter of the crest of the screw thread maximizes the surface area of ​​the threads in contact with bone. While enlarging the diameter of the screw shaft 33 near the bone screw head 32 increases its strength, if necessary by reducing the diameter of the screw shaft 33 from the screw head 32 where such resistance is not required, it allows achieving the maximum engagement area for the thread 31 with respect to the bone.

In the preferred embodiment, as shown in Figures 24A and 26, the bone screw tip 36 is provided with cutting slots 38, to make the bone screw 30 self-tapping. Unlike previously known bone screws used for anterior cervical spine surgery, which are not self-tapping, the screw shape of the present invention is more similar to that of a tap. than a conventional screw due to the fact that the threads are sharp and grooved. Additional embodiments of bone screws 30 are shown in Figures 53-55.

By way of example, plates for the fusion of three adjacent vertebrae (two gaps or two dorsal segments) are shown. Each set of bone screw receiving holes associated with a vertebra is considered to be a segment of the plate so that, for example, three segments are shown in Figure 1: an upper segment, a central segment and a lower segment. While the present disclosure relates to plates to be used in the fusion of three vertebrae with two gaps, it should be understood that longer and shorter plates are envisioned having the appropriate number and proper placement of bone screw receiving holes. corresponding to the number of vertebrae to be fused, and would adopt the shape of the plates shown with a greater or lesser number of intermediate segments, such as the segment along line 9 of Figure 1, or the intermediate segments of the plates shown in Figures 82-84F.

Referring to Figures 31-42, an explanation of the steps of the method for installing the plates is shown below. This explanation is followed by a detailed description of the instrumentation and method for installing the multi-lock plate.

Stage 1

After the interbody fusions are complete, the surgeon removes any protruding points or irregularities located along the front of the spine from the area to be fused.

Stage 2

The correct length plate is selected by the surgeon, measuring the distance over the thoracic spine using a gauge, ruler, template, or the like. The plate shall be of sufficient length to cover the distance from the spine to be fused and partially overlap a part of each of the end vertebrae to be fused.

Stage 3

Using a plate holder, the plate is placed within the wound and positioned to confirm the positioning, length, and alignment of screw holes with respect to the spinal cord segments to be fused.

Stage 4

As shown in Figure 31, with the plate thus positioned and firmly retained, the plate can be attached to any of the vertebrae to be fused (by way of example only, upper vertebrae shown).

Sub-stage 4A

The pilot punch 60 (guide) of the hole is attached to the plate 2, as shown in Figure 32, or alternatively, although not preferably, the drill guide can be used as indicated in Figure 37. In In either case, the pilot hole forming means is rigidly aligned with the bone screw receiving hole wall of the plate, being captured by it.

ES 2 371 634 T3

Sub-stage 4B

The pilot hole is then formed by impact of the pilot hole punch of FIG. 32 or by drilling with the drill bit of FIG. 37. In an alternative embodiment, which is not preferred, the formation of the pilot hole can be dispensed with and You can directly insert the correct screw selected so that it has a length less than the distance along its path to the posterior vertebral cortex.

Determination of the appropriate screw length is done by measuring or applying a template from X-rays, MRI, or CT scans, or is determined directly by measuring the depth of the disc space.

Stage 5

The correct screw is then attached to the screwdriver which, regardless of the specific shape of the screwdriver engagement means, is designed to have an interference mount in order to remain firmly attached to the screwdriver during transport to the site. insertion. Figures 41, 42, 63, 64, 80 and 81 show various ways of achieving such a coupling between the screwdriver and the screw. In addition to wedging the screw and screwdriver interface, clips and springs as well as other means for temporary and reversible fixation of the screw to the screwdriver are well known, as shown in Figure 80, in which a slotted bushing with features The inward spring retains a peripherally threaded cap until, as it is threaded onto the plate, it is automatically pushed back, releasing the threaded cap.

Once a first bone screw has been fully inserted into one vertebra through the plate, it is preferred to insert the other of the transverse pair in the manner already described with respect to Figure 33.

Similarly, it is possible to insert the remaining bone screws, according to the surgeon's preference, in each of the vertebrae to be included in the fusion, exactly the end vertebrae of the fusion assembly or construct, or to additionally place screws in the bone grafts. fusion.

However, as shown in Figures 33, 34, 38 and 39, it is possible with the present invention, at the option of the surgeon, to place any part or all of the fusion construct under compression and thus proceed in a manner intersegmental or along the entire length of the fusion construct, even when it has a multi-segment structure.

It will be appreciated that the same procedure could generally be used for any of the plate systems of the present invention.

As shown in Figure 31, the vertebrae 50a-c are separated from each other by blocks of fusion grafts 51 that have been mounted anteriorly in the disc space of the spine between adjacent vertebrae 50, forming a graft construct of bone for fusion. The plate 2 is shown in figure 31 with the locking elements 20, 21 removed, in order to simplify the illustration. It will be understood, however, that in the preferred embodiment the locking elements 20, 21 can be and preferably are, pre-installed in the positions shown in figure 6, prior to positioning the plate 2 on the vertebral bodies of the vertebrae 50, thus saving time and trouble for the surgeon.

Plate 2 may be retained in position in any plate support means, but preferably by the retention tools shown in Figures 45, 46, or 47 via slots 142 in the sides of compression arms 104, 130 of a vertebral compression tool 100, as shown in FIG. 39, or as a further alternative, by the unitary plate holder, similar to the design of FIG. 70.

As shown in FIG. 45, the plate holder 870 has a hollow tubular housing 872, with a central rod 874 with a thread 878 at one end for engagement of one of the screw lock holes 12 in plate 2. The bottom end of housing 872 has projections 880, 882 which extend outward and then downward to engage bone screw receiving holes 8 in plate 2, preventing housing 872 from rotating. Center rod 874 is located in housing 872 so that it can be caused to rotate by causing rotation of a handle (not shown) which is attached to center rod 874 at its upper end.

An alternate embodiment of the plate holder 890 is shown in FIG. 46. A single solid member 890 has a threaded boss 894 at its lower end for engagement with the central threaded locking hole 12 in the plate. The lower surface of the bracket 890 of this embodiment is shaped to conform to the contour of the upper surface of the plate adjacent to the locking hole 12, shown in the form of a recess or depression 14.

ES 2 371 634 T3

Referring to Figures 67-68, one embodiment of a plate holder for retaining any of the plates disposed on vertebrae is generally shown and referenced at 800. The plate holder 800 has a hollow tubular housing 802 with a center rod 804 having a handle 806 at one end and a thread 808 at the other end for engagement with one of the threaded lock holes 12 in plate 600. The lower end of the housing 802 has protrusions 810, 812 that extend outward and then downward 814, 816, engaging along the lateral edge of the plate 2 between the end and intermediate lobes 4, preventing the housing 802 can rotate. The central rod 804 is located in the housing 802 so that it can be rotated by rotation of the handle 806, which is attached to the central rod 804 at its upper end. This center rod 804 may also be attached to the body 802, so that it can be moved up and down to some extent in a number of conventional ways, for example, by causing the center rod 804 to have an annular recess about a length of 3-5mm, and an adjusting screw that protrudes inward from the housing to engage the center rod 804. Once plate 600 is in the proper place and the plate is attached to one of the vertebrae by bone screws 30, center rod 804 is disconnected from the opening in plate 600 and bracket 800 is removed.

Figure 69A is an alternative embodiment of the plate holder 850. A single solid element 852 has a threaded boss 854 at its lower end for attachment to the central threaded locking hole 12 of the plate. Solid member 852 could also be threaded into a bone screw receiving hole 6. The bottom surface of the bracket 850 of this embodiment is shaped to match the contours of the top surface of the plate adjacent to the locking hole 12, shown as recess 14.

Fig. 69B is another embodiment of the plate holder 850 '. A housing 851 'having an end 853' configured to engage a receiving hole 6 of a bone screw, contains a rod 855 'that has an irregular diameter and is provided with a threaded area 857'. As rod 855 'is rotated through a handle similar to handle 806 shown in FIG. 68, rod 855' is threaded into housing 851 'at mating threads 858'. As the end of the rod 855 'is inserted, the rod extends portions 859a' and 859b '(859c' and 859d 'not shown) wedging the plate holder 850' into a hole in the receiving plate of a bone screw. Plate Holder 850 'is best used with non-threaded bone screw receiving holes, but works for all types of bone screw receiving holes.

Referring to Figure 70, an alternative embodiment of the plate holder referred to at 800 'is shown, wherein there is a removable handle 860' which is used to first fix the holder 800 'from the plate to the plate itself, by turning the stem 804 and then holding the plate support 800' to the side by the extension 864, during the fixing process, reducing the interface of the plate holder 800 with the surgical process.

Referring to Figure 38, a compression tool 100 is shown with a toothed bar 102 having a first compression arm 104 attached to its free end. Compression arm 104 has, at its distal end, a hole 106 for removably retaining a plate engagement member 108, shown in FIG. 36, having a hook 110 at one end for engagement of a plate. recess or depression or slot 18 at the end of plate 2, or to removably retain a compression element 54 shown in Figures 33-34. As shown in figure 36, the plate coupling element 108 comprises the stem 112 that will be inserted into the corresponding hole 106 of the compression arm 104, and a flange 115 to rest against the bottom or bottom face of the hole 106 to precisely limit the depth of insertion of plate engaging element 108 into hole 106. An annular spring 128, preferably metallic, is located in an annular recess of the shaft 112, to retain the plate coupling element 108 in the hole 106.

Referring to Figures 38-39, compression tool 100 comprises a second movable compression arm 130 movable along toothed bar 102 parallel to first compression arm 104. The distal or remote end of second compression arm 130 it also has a hole 132, like hole 106, which can receive a removable stem 134. The holes 106 and 132 are the same, so that either of the compression arms 104, 130 can be used to retain the removable stem 134, allowing the compression tool 100 to be used in any orientation. By allowing plate engaging member 108 and compression stem 54 to both rotate and slide into holes 106, 132 of the two compression arms 104, 130, with plate engaging hook 110 able to function even By forming an angle with respect to the plate, it is possible for the apparatus to be easily attachable to the spine via the compression stem 54 and the plate.

Compression arm 130 has a drive assembly consisting of a sprocket (not visible) that is engaged with sprocket 138 of sprocket bar 102 and is connected to compression arm 130 such that compression arm 130 it is movable along the length of the toothed bar 102 by means of the rotation of the handle 140, which is connected to the toothed wheel. When handle 140 is rotated in the direction of the arrow shown in FIG. 38, compression arm 130 is moved toward compression arm 104. The drive assembly has a self-locking release mechanism so that the

ES 2 371 634 T3 movement of the two compression arms 104, 130, moving away from each other, is prevented, without activation of the disassembly or release. At the inner distal end of each of the compression arms, on opposite sides to each other, there is a slot 142 or recess to retain the plate 2 along its sides between the central lobes 4 and the end lobes 4, such as shown in figure 37.

While toothed bar 102 and compression arms 104, 130 have been described as straight, it is possible that toothed bar 102 and compression arms 104, 130 are arcuate or other shaped, for induction purposes. Lordosis in the vertebrae, if desired.

As shown in Figure 31, in the case where the compression tool 100 is used to retain the plate 2, the ends 144 of the compression arms 104, 130 will be located in line with the element or construct of fusion graft 51, which has been placed in the disc space when plate 2 is properly positioned. A gap will be produced between the plate 2 and each of said fusion graft elements 51, providing a space to receive the free ends of the arms 104, 130, should they extend beyond the bottom surface of the plate 2. As will be described later, the same compression tool 100 has also been used for the compression of a series of vertebral bodies of the cervical part with interposed bone grafts during the coupling of plate 2 to vertebrae 50.

Referring to Figure 31, plate 2 is retained by a suitable support, in the case shown in the form of compression arms 104, 130. Once the plate 2 of the appropriate length has been positioned, so that the receiving holes 6 of the bone screws are aligned with each of the corresponding vertebrae 50a-ca to fuse, the next stage consists in the formation of the holes 6 bone screw receptors prior to mounting the bone screws 30 themselves in the vertebrae 50a. Although the procedure has been described with the fixation, first, of plate 2 to the upper vertebrae 50a, the plate 2 can be fixed to any of the vertebrae in any order. Plates of different dimensions are used so that, as indicated above, the physician will select the plate of the appropriate dimension in which the bone screw receiving holes 6, 8 are aligned with the three adjacent vertebrae 50a, 50b and 50c. Pilot holes are formed by an apparatus 60 for forming them, as shown in Figures 31 and 32. Unlike prior art and screw coating systems, bone screws 30 can be inserted without prior formation of an opening in the vertebrae, since bone screws 30 are preferably made with a sharp point, and with self-tapping characteristics, and have a decreasing head diameter at the tip to aid screw entry and penetration into the bone. However, while a hole may be formed in the bone of the vertebrae prior to screw insertion, it is preferred that the hole has a diameter smaller than the diameter of the screw base and for a different purpose than in the art. previous. In the prior art, the drilled hole had to have a diameter equal to but preferably greater than the diameter of the base (minor) of the screw, since the screws are not self-tapping. It is desirable to create pilot holes to ensure that a proper trajectory is maintained for the bone screws 30, and also to prevent damage to the bones of the vertebrae during the insertion of said bone screws 30. In addition, the hole-forming apparatus 60 The pilot creates a more compact vertebral bone mass to receive the self-tapping bone screw 30 used in this insertion.

As shown in Figures 31 and 32, the apparatus 60 for forming the pilot holes comprises a hollow cylindrical housing 62 having its bottom provided with a through hole 63. The housing 62 comprises a central shaft 64 which is It extends through the through hole 63 in the bottom of the housing 62. The forward end 66 of the shaft 64 tapers gradually to a sharp point 65. The shaft 64 is provided with an annular element 73 having a diameter that closely corresponds to the internal diameter of the casing 62 to guide the displacement of the axle 64 within the casing or housing 62. A compression spring 67 is interposed between the annular element. 73 and the bottom of the housing 62. The compression spring 67 provides a counter force that normally forces the sharp point 65 to a retracted position within the housing 62. The upper end of the stem 64 has a larger head 68 that extends out of the casing 62, which is intended to be pressed manually or struck by a percussion instrument, in order to drive the sharp point 65 out of the socket. shell 62, passing into vertebral body 50a. The shaft 64 has a length, taking into account the length that the spring 67 will have once fully compressed, to determine the maximum depth of the pilot hole formed in the vertebral body. The depth is selected to ensure that the pilot hole does not reach the posterior cortex of the vertebral body, which borders the spinal canal.

Certain structural features of the hole forming apparatus 60 are shown in more detail in Figure 32. In particular, it can be appreciated that the lower end of the housing 62 has a projecting portion 69 dimensioned to precisely engage the Bone screw receiving hole 6 or 8 of plate 2. The bottom 71 of the protrusion 69 is flat in a plane perpendicular to the axis of the housing 62. When the protruding part 69 of the housing 62 is inserted intimately into a hole 6, 8 receiving a bone screw and the flat bottom 71 is placed flush against the upper surface of the plate 2, it is ensured that the front end 66 of the shaft 64 will form a pilot hole in the vertebral bone having its axis perpendicular to the plane of the associated portion of plate 2, thereby ensuring that bone screw 30

ES 2 371 634 T3 will be installed next so that its axis is also perpendicular to the plane that is parallel to the upper and lower surfaces of the associated part of the plate 2.

When a plate having a threaded hole is used to receive a screw, the lower end of the pilot hole forming apparatus 60 is threaded to engage the thread of the bone screw receiving hole 6, 8, securing accordingly. this way the plate and the pilot hole forming apparatus with each other, ensuring a stable coupling between the pilot hole forming apparatus and the plate 2. It should be noted that the diameter of the leading end 66 of the stem 64 is small since it has to fit within the reduced space that remains between the inner walls of the pilot hole forming apparatus. Since only a pilot hole is formed for a self-tapping bone screw 30, the reduced diameter is satisfactory.

Referring to Figure 37, if for any reason it is desired to form the pilot hole in the vertebral body 50 by drilling, instead of using the pilot hole forming apparatus 60, a drill guide 80 may be used, which has a lower end as shown in Figure 37. The drill guide 80 consists of a tubular member 82 and a small diameter lower end 84 that is dimensioned to achieve a precise interference fit in the associated bone screw receptor hole 6, 8 of plate 2. Along the small diameter lower end 84, the drill guide 80 has an axial end surface in a plane perpendicular to the longitudinal axis of the drill guide 80, such that when the reduced diameter portion 84 is engaged inside the bone hole receiving hole 6 and the surface surrounding said small diameter portion 84 is flush with the upper surface of plate 2, the axis of the drill guide hole 86 in the drill guide 80 will be precisely perpendicular to the upper and lower surfaces of the associated portion of plate 2. As in the case described above, the lower end of drill guide 80 may be threaded to engage the threaded opening in plate 2.

After the holes 6, 8 have been formed for bone screw receptors in the vertebral body 50a through the two upper holes 6 for fixation of bone screws of the plate 2 by means of said hole forming apparatus 60 or guide 80 for the drill bit, bone screws 30 are threaded into vertebrae 50 while simultaneously holding plate 2 firmly against vertebrae 50 with compression tool 100 or plate holder 800. This locks the plate to the 50th vertebrae.

It is then possible, if desired, to compress the fusion graft in the next adjacent vertebrae 50b, prior to coupling the bone screws 30 to the adjacent vertebrae 50b through the central bone screw receiving holes of the Plate 2. Once the initial bone screws are in place at vertebrae 50a, plate holder 100 or 800 can be removed from plate 2. Compression of the fusion element or construct between the two adjacent vertebrae 50a and 50b is achieved as follows:

The compression stem 54 is driven through the central locking hole 12 of the plate 2 by means of the insertion tool 90, shown in Figures 33, 34 and 35, passing into the vertebral bone of the vertebra. 50b, where it will be used in a next step to apply a compression force between vertebrae 50a and 50b. The compression stem 54 consists of a shaft 56 that has a sharp point 57 at its lower end, a larger central collar 58 that serves as a depth stop, and a circumferential groove 59 near its upper end, defining a enlarged head 55.

The compression stem insertion tool 90 comprises a shaft 92 having a closed hollow portion 94 at its lower end 96 to receive the compression stem 54 and an enlarged hammer cap 98 at the other end. The compression stem insertion tool 90 also comprises, at its lower end 96, a second opening 95 having a recess 99 in its inner wall to allow engagement of the enlarged head 55 on the compression stem 54 within the depression o recess 97. Second opening 95 is in communication with hollow portion 94 of insertion tool 90, as shown in FIG. 35.

Referring to Figure 38, the hole 132 of the second compression arm 130 of the compression tool 100 is applied over the compression stem 54 at the vertebrae 50b, and the plate engaging element 108 is inserted into the hole 106 of the first compression arm 104 of the compression tool 100. Hook 110 of plate engaging element 108, shown in FIG. 36, is mounted within slot 18 at the end of plate 2 which is secured by bone screws 30 in vertebra 50a, such as shown in figure 38. However, as indicated above, the compression tool 100 can be forced to rotate so that the first compression arm 104 is, in this case, at the bottom and is capable of engaging on the compression stem 54 in vertebra 50c.

Since the plate is attached to the vertebrae 50a by means of the bone screws 30 and the compression stem 64 is fixed to the adjacent vertebrae 50b, the movement of the first and second compression arms 104 and 130 in the direction of the vertebrae 50a, by rotation of the handle 140, results in the

ES 2 371 634 T3 compression of bone graft element or construct 51 between adjacent vertebrae 50a and 50b. The distance of several millimeters is sufficient for compression of the bone graft element or construct 51. Once the desired compression has been obtained, the pilot holes for bone screws can be formed in the vertebral body 50b by means of the pilot hole forming apparatus 60, as described above, for the insertion of the bone screws. 30 into bone screw receiving holes 8 of bone plate 2, securing plate 2 to adjacent vertebrae 50b. The compression tool 100 can then be removed by activating the release element.

Figure 39 shows the use of the compression tool 100 to induce compression between the two lower vertebral bodies 50b and 50c after the bone screws 30 have been installed in the middle vertebral body 50b, as just described. As shown in FIG. 39, compression stem 54 remains in place in mid vertebral body 50b, and a further compression stem 54 is driven into lower vertebral body 50c by tool 60. formation of the pilot hole, distal to the plate itself, in the recess located in the end projections 4 to allow the lower compression stem 64 to be displaced towards the vertebrae 50b in an upward direction, as shown. The original compression rod 64 is inserted into the hole 106 of the first compression arm 104 and the additional compression rod 54 is inserted into the hole 132 of the second compression arm 130 of the compression tool 100. Again, as explained above, rotation of handle 140 results in the two compression arms 104, 130 moving toward each other, with the result that compression stem 54 in vertebra 50c moves toward the upper compression stem 54 of the vertebra 50b, again compressing the fusion graft element or construct 51 between the vertebrae 50b and 50c. The upper compression stem 54 of the vertebra 50b cannot be displaced since the vertebra 50b has been fixed to the plate by the insertion of the bone screws 30 in the holes 8 of the plate 2, receptors of the bone screws. Therefore, only the lower compression stem 54 and vertebra 50c can be displaced. As before, pilot holes associated with vertebra 50c are formed and bone screws 30 are inserted through bone screw receiving holes 6. Then, the compression tool 100 is disassembled. The compression stem 54 is then removed from the vertebra by inserting it into the second opening 95 of the compression stem insertion / removal tool 90 so that it engages the enlarged head 55 at the end of the compression stem 54 at the depression 57, as shown in figure 34.

It will be appreciated that other variants can be used for compression purposes. For example, during compression of the fusion element or construct 51 between vertebrae 50b and 50c, the hook 110 of the compression tool 100 may make contact with the slot 18 at the end of the plate 2, and the other compression arm of compression tool 100 can engage compression stem 54 at adjacent third vertebra 50c. It should also be noted that the plate 2 has a cutout portion in the form of an extreme recess, between the lobes, at the end of the plate for insertion of the compression stem 54 into the vertebra. Otherwise, there may be no space below the end of plate 2 for insertion of compression stem 54.

It will be appreciated that the above-described process has been carried out with bone screws 30 fully inserted into vertebral bodies 50a, 50b, and 50c, and lordosis is maintained during compression of the bone graft construct or element 51.

As noted above, the process for attaching plate 2 to vertebrae 50a, 50b, and 50c has been shown without locking screws 20, 21, in place, on plate 2. Figure 40 is a perspective view showing plate 2 of Figures 1-5, at one stage of a surgical procedure, when bone screws 30 have been fully installed in three adjacent vertebrae 50a, 50b, and 50c and the locking screws 20, 21 have been rotated through an angle of about 90 ° to lock three bone screws 30 in place; so that the left locking screw 20, as shown, has been rotated through an angle of about 60 ° to lock three bone screws 30 in place, and the central locking screw 21 has been forced to rotate through an angle of about 90 ° to lock two other bone screws 30 in place. At this time, one of the cam surfaces 44 of each of the locking screws 20, 21 rests on top of the screw head 32 of the corresponding bone screw 30.

The mounting of the locking cap 300 can also be carried out with a tool 220, as shown in Figures 41 and 42, with an appropriately shaped tip 222 with a length depending on the depth of the hole 306 in a locking cap 300. End 222 of tool 220 is flared in the vicinity of the most distal end, creating a press fit with screw cap 300 for ease of manipulation, and prevents screw cap 300 from dislodging from tool 200. .

Figure 43 is a sectional view, along the plane of the axis, of the two holes 6 for end locking screws of plate 2, with two bone screws 30 in their mounting positions and the locking element 21 in its position of blocking. Figure 44 is an enlarged view of one of the bone screws 30 in plate 2 of Figure 43. In a preferred embodiment, the axis of each screw 30 is generally perpendicular to tangents to

ES 2 371 634 T3 the upper and lower surfaces of plate 2, at points that are intersected by the longitudinal axis of the associated bone screw 30. Therefore, because of the curvature of plate 2 in the plane of the figure 18, the bone screws 30 can be directed to converge toward each other at the desired angle. The axis of the two bone screws 30 shown in FIG. 18 can form an angle of about 45 °. Alternatively, the curvature of the plate from side to side may be such that it conforms to the anterior profile surface of the adult human cervical spine, and the axis of the paired screw holes may deviate from the perpendicular to the plate, when viewed from the end, achieving optimal convergence.

Since the bone screws 30, once inserted, are locked to the plate, a “claw” with a rigid triangular structure is obtained on each pair of bone screws 30, such that the coupling of the plate 2 to the vertebral bodies 50a, 50b, and 50c would be very safe due to the retention of a wedged mass of bone material between the triangle formed by the bone screws, even if some thread slippage occurred. The "claw" can be further formed by three angled bone screws, in a tripod configuration, or by four bone screws in a four-sided claw configuration.

A coating system can be assembled, according to any of the previous embodiments, in the same manner as described, and using the same instruments and tools, as shown and described above with respect to the first embodiment. In the case of the embodiment shown in Figure 22, compression operations would be carried out via slot 604, rather than intermediate hole 12 for a locking screw.

b.) Single Locking Plate Systems

The single lock plate system will be described below. Figures 47-52 are views of a first embodiment of a single plate locking system. The outline of plate 600 is the same as that of plate 2 shown in Figures 1-5. Plate 600 contains bone screw receiving holes 602 that are internally threaded 603 to receive corresponding locking elements in the form of a locking cap 610 shown in Figures 56-59. For example, in plate 600, bone screw hole 602 has an external diameter of approximately 5 mm with a preferred range of 4-6 mm and a threaded internal diameter of approximately 4.8 mm with a range of 3. 5-5.8 mm for this use. Fastening means other than threads such as bayonet-type fasteners can be used.

The bottom of each bone screw receiving hole 602 has an inwardly stepped portion of appropriately selected dimensions to retain an associated bone screw 170, as shown in Figures 53-55. As described in detail below in this embodiment, a single locking cap-shaped locking element 610 with thread threads 608 shown in Figures 56-59 is associated with each of the screw receiving holes 602 for bones.

The difference between the bone screw 170 used in the single locking plate embodiment versus the bone screw used in association with the multiple locking plate is essentially due to the fact that while in the locking plate embodiment multiple locking, the locking elements slide over a portion of the top 39 of the screw head 32, in the single locking plate embodiment, the locking cap 610 engages over the head 172 of the bone screw 170. Therefore, the head 172 of the bone screw 170 of the present embodiment need not be smooth. This allows the head 172 of this embodiment of bone screw 170 to be thicker and stronger.

Figure 63 shows two bone screws 170 and associated threaded locking caps 610 in their fully installed positions. In these positions, the head portions 174 and 176 of each of the bone screws 170 form an interference fit with corresponding portions of a bone screw receiving hole 602. The flange 612 of each threaded locking cap 610 forms an interference fit with the top 178 of the head of its associated bone screw 170. Since the thread 608 of each locking cap 610 precisely mates with the internal thread of a bone screw receiving hole 602, each threaded locking cap 610 is additionally subjected to a clamping force between the portion 178 of the associated head and internal thread threads 603 of the associated bone screw receiving hole 602. The rounded head 614 of each threaded locking cap 610 ensures that the top surface of a mounted plate system will be free of sharp edges or protrusions.

Referring to Figures 80 and 81, tools are shown for use in inserting the bone screws and locking cap into a single-type locking plate 600. In the first embodiment of the drive tool 1000 shown in FIG. Figure 80, said tool 1000 has an enveloping tubular body 1002. Within the housing 1002 is a hexagonal or "torks" drive element 1004 having a projecting end 1006 that corresponds to the recess 306 in the cap 610 for engagement with said cap 610. As noted above, the device Actuator 1004 is configured to provide a firm fixation for locking cap 610 to retain locking cap 610 firmly relative to the driver. Hex Drive 1004 is hollow to hold

ES 2 371 634 T3 ability for the shaft 1010 of a Phillips or “torks” screwdriver to be engaged by the hollow part 1012 for engagement by the tip 1012 with the corresponding recess 1080 of the bone screw 170 for engagement by the end 1006 of the device drive 1004. Stem 1010 and actuator 1000 are longer than tubular body and actuator 1004 has an upper end (not shown) that extends from the upper end of tubular body 1002 so that it can be rotated. using the handle.

The housing 1002 has a diameter that allows the locking cap 610 to be retained within the inner end of said tubular body 1002 by frictional engagement or by the actuator 1004. It will be appreciated that other methods can be used for the retention of the locking cap 610 within the end of the tubular housing 1000.

As shown in FIG. 80, the operation of the bone screw and locking element actuator 1000 is as follows: The cap 610 is inserted over the end of the cap driver 1004 and then said cap driver 1004 with the shaft 1010 of the bone screw driver passing through the central longitudinal opening of the bone screw driver. cap actuation. As shown, the shaft 1010 of the bone screw driver passes through the recess 306 in the cap 610 and engages the recess 180 in the head of the bone screw 170. The bone screw 170 has been shown mounted in a bone screw receiving hole in plate 600. The handle (not shown) of the bone screw driver is rotated, thereby screwing the bone screw 170 in place. Since the diameter of the bone screw driver is less than the width of the recess 306 in the cap 610, the bone screw driver 1010 can rotate without rotation of the cap 610.

The hollow tubular housing 1002 rests on the upper surface of the plate 600 and aids in the alignment of the stem 1010 relative to the plate. Once the bone screw 170 has been inserted, the cap driver 1004 is driven until the threads 608 on the outside of the cap 610 engage the threads 603 in the bone screw receiving hole. . Then, the cap actuator 1004 is rotated until the cap 610 is securely in place.

In Figure 81, an alternative embodiment of the combination of the bone screw and locking cap driver is shown. In this embodiment, no housing is used. Instead, the cap driver 1010 retains the cap 610 by friction and the handle 620 for the bone screw driver 1010 is rotated. A spring and ball assembly 622 holds the cap driver 1002 at the top until the bone screw has been screwed into the receiving hole thereof. The actuator 1010 has an elongated portion that, once the bone screw has been assembled, the spring and ball assembly 622 is depressed, and the handle 624 associated with the cap actuator can be lowered for rotation. cap 610. A tubular housing can be used to aid in the alignment of cap 610 in the bone screw receiving hole, as noted above.

The actuation elements, shown in Figures 80 and 81, simplify the procedure and reduce the number of instruments that need to be used during the assembly process. The process is fast and reliable, giving the clinician greater assurance that small parts will not be lost or difficult to handle.

Figure 52 is a top plan view of plate 600, partially assembled, with threaded locking caps 600 mounted in bone screw receiving holes 602.

Figures 54-56 show a bone screw 170 for use with the single locking plate system in accordance with the invention. The bone screw 170 differs from the bone screw 30 previously described in detail only with respect to the stepped configuration of the head 172. Preferably, bone screw 170 includes a lower portion 174 that is continuous with the screw shaft, and has a reduced diameter equal to the maximum diameter of shaft 176. Head portion 178 of head 172 also has a smaller diameter than that of the shaft. bottom 174. Thread 182 has the same configuration as bone screw 30 discussed above. However, any embodiment of bone screws can be used with either plate.

As in the case of a multiple plate locking system described above, bone screws 170 for use in a single locking plate system are preferably solid so that the screws reach the surface. of the bottom plate, in which situation, the screws used with plates of the prior art have the greatest tendency to break, the only recess in the heads being for engagement of the tip 222 of the driving tool 220 and the recess being above the critical area. Therefore, these bone screws 170 continue to be robust. The screw heads are not

ES 2 371 634 T3 are deeply slotted dividing them into parts, and the locking caps do not exert a radial external force on the associated bone screw heads, so that the screw heads do not open by deforming and weakening.

Referring to Figures 71, 73 and 75, another alternative embodiment of the single locking plate system of the present invention is shown, referenced to 500. Plate 500 has the same contour as plate 2 of Figures 1 to 5, but associated with each of the bone screw openings 502 are threaded openings 524 offset from bone screw openings 502 to receive the locking element 506-508 shown in Figures 72 and 74 as a set of threaded locking screws or cap 506 or screw 508.

It will be appreciated that other unique locking plate configurations can be used. Referring to Figure 82, a single locking plate 900 is shown showing a pair of bone screw receiving holes 910 at its ends 930 and a series of bone screw receiving holes 950 along the length of the plate. longitudinal axis of plate 900. Additional bone screw receiving holes 950 allow a single plate to be able to align with a series of disc spaces of different sized vertebrae and bone fusion grafts. As noted above, the plate of the present invention shown in Figures 1-5 requires selection of an appropriately sized plate by the surgeon such that each pair of bone screw receiving holes 6-8 are aligned. with the appropriate vertebrae. This requires having a series of plates of different dimensions for optimal coupling of the bone screw receiving holes to each of the vertebrae. With plate 900 of FIG. 82, the reduced spacing and increased number of central openings allow the surgeon to position at least one appropriate opening in alignment with each of the intermediate vertebrae and / or bone grafts.

The procedure for mounting single-type locking plates is substantially the same as that described in detail for multiple-type locking plates. The central longitudinal groove 670 of the single-type locking plates is used for the compression process. The same instrumentation is used to create the hole in the plate by means of a punch or drill. Figures 60-69 show the different stages in the assembly procedure of the single-type locking plates, comparable with the steps used in the assembly of the multiple-type locking plates.

Referring to Figures 76-79, the heads 507 and 526 of the locking elements 508 and 522 have a recess 510 and 524 corresponding to the radius of the bone screw openings 502 and 528, so that the locking element 508 and 522 can be mounted in place prior to insertion of bone screw 170 into hole 502 and 528 for receiving bone screws. When locking elements 508 and 522 are forced to rotate, a portion of their head extends over the top of the head of bone screw 170 locking in place. As in previous embodiments, the lower surface of the locking screws 508 and 522 may have an eccentric and another configuration, for engagement with the upper surface 39 of the associated bone screw 170.

Although the instrumentation of the plates and their procedure have been described, in relation to the fixation of a plate to the vertebrae of the spinal column, it should be noted that the plates can be adopted for application to other parts of the body. However, the dimensions of the plate, the specific contour of the plate, and the placement of the receiving holes for the bone screws would have to be modified.

Similarly, the bone screws described in this application can be used in other parts of the body, which would also have to be modified to serve the intended purpose, depending on the dimensions of the part of the body in which they have to be mounted. .