Implant for transforaminal intracorporeal fusion

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DESCRIPTION

Implant for transforaminal interbody fusion.

The invention relates to an implant for transforaminal interbody fusion of lumbar spinal column segments, the surface areas that come into direct contact with the spine at least in sections having protection against dislocation, furthermore being provided within or on the implant a connection piece for a positioning instrument and holes or cavities for filling are arranged inside the implant, according to the generic concept of claim 1.

In interventions of the spine, we try to work in a minimally invasive way, developing in this sense some so-called PLIF surgical techniques (Posterior-Lateral-Interbody-Fusion = posterior-lateral interbody fusion). With this surgical technique, the intervertebral disc is excised through a posterior approach and the intervertebral space is filled with autologous bone. This technique dates back to Cloward who performed an operation of this type for the first time in 1943. Improvements in the PLIF technique led to the use of a transforaminal approach. In this technique, titanium baskets filled with spongiosa, the so-called cage, are inserted transforaminally from the dorsal side. Simultaneously, instrumentation and dorsal stabilization are used. The advantage of the briefly described method is that you do not have to use any additional transabdominal or retroperitoneal access.

In the "biotite basket" from Ulrich, this serves as an intervertebral disc prosthesis for the lumbar spine. The cage is used by means of a back access, being possible the application by pairs or individual. This known cage is essentially U-shaped and is protected against dislocation by a grooved structure. The implant material in the previously mentioned cage is titanium or a titanium alloy, so that relatively large radiological windows will be necessary to control the fusion.

Furthermore, a cage sold by the company Stryker Orthopedic, USA, is known in the form of a cubic implant, which can be implanted in pairs from both the anterior and posterior sides in the intermediate vertebral space.

With regard to the state of the art, patent DE 43 28 062 A1 should still be mentioned, which refers to an implant for the replacement of vertebral bodies and / or for the stabilization and fixation of the vertebral column. In this implant, an implant body is pushed transversely to the rod axis on a support rod. The implant body according to DE 43 28 062 A1 is provided with a surface structure on its adjacent vertebral bodies to support the implant, so that there is reciprocal fixation of the adjacent surfaces of the implant body on the one hand and of the bodies vertebral on the other hand.

The state of the art also includes height-adjustable vertebral body implants for the replacement of one or more vertebral bodies, for example according to DE 44 23 257 A1, DE 195 19 101 A1 or DE 195 09 317 A1. However, the manufacture of implants of this type variable in height is very expensive and complicated to handle.

A vertebral body substitute is disclosed in the German Industrial Utility Model DE 296 16 778 U1, which is incorporated e.g. ex. after vertebral body resection at the site of the missing vertebral body. Such substitutes must consist of a material tolerable for the body, the front ends forming an irregular edge and the wall of the substitute has holes, so that sufficient space has been created to receive the bone substance.

To incorporate the substitute according to DE 296 16 778 U1, a tool is used which has a relatively long shank, the shank comprising a threaded bolt at the free end. The threaded bolt may intervene with a threaded hole in the sheath-shaped body to insert the sheath at the preset position between two adjacent vertebrae in the resisted vertebral body space.

From patent US 2004/0153065 A1 an implant with a positioning device is known, which has a shape similar to a sickle and there is a connection at one end of the implant. The connection has through-holes which are in a position to receive a correspondingly formed end piece of the positioning instrument. For this reason, there is the possibility of making turning movements in the surgical use of the implant using the positioning instrument.

In the implant for interbody fusion of vertebral segments according to WO 02/17823 A1, the surface areas that come into contact with the vertebral column have dislocation protections in the form of teeth. One end of the implant has a front surface that is provided with an internal thread hole for receiving a threaded end corresponding to an angle of the respective positioning instrument.

The theory according to patent EP 1 290 985 A2 discloses a vertebral body implant, the arms of which can be opened by an intermediate piece kept movable and movable between the arms, for which a special positioning instrument is used.

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Subsequently published WO 2005/041825 shows an implant for transforaminal interbody fusion of lumbar spinal segments, the implant having a sickle shape. In the local implant, both ends are provided with an oblong hole, to optionally house a shaft end of a positioning instrument. Due to the implementation of the implant provided on both sides for the admission of the positioning instrument, it is impossible to shape the insertion end of the implant in such a way as to allow insertion of the implant without opening the spinal column segments.

From the aforementioned, it is the task of the invention to indicate an improved implant for transforaminal interbody fusion of lumbar spine segments, the implant having to present a high primary stability and being possible a simple surgical procedure in the application.

The solution to the task of the invention is carried out with an implant according to the combination of characteristics according to claim 1, the sub-claims comprising appropriate configurations and refinements.

Starting from an implant that has protection against dislocation in the surface areas directly in contact with the spinal column at least in sections and that has a connecting piece for a positioning instrument, the body of the improved implant has a shape sickle, the arch of the sickle being oriented ventrally and the inner side of the sickle dorsally.

The special connection piece is located at one end of the sickle, acting as a trochoid joint, the opposite end of the sickle having a shape similar to a beak ending in a point that serves as an insertion resource. Between the sickle walls of the implant body there is present at least one filling opening to receive the large volume bone substance.

The connecting piece is made as a bolt, housed in a through hole, rotatable or tiltable, the bolt having an insertion opening which extends perpendicular to the longitudinal axis for an instrument.

Provided at the sickle end of the connecting piece is a recess for access to the bolt and an insertion opening there for the aforementioned positioning instrument.

The implant preferably consists of a bioelastic synthetic material, in particular polyether-etherketone (PEEK), however other materials suitable for implants are also conceivable.

Radiographic markers are embedded in the bioelastic synthetic material. These radiographic markers can be located medial ventral in vertical alignment and at the tip of the implant in horizontal sagittal alignment.

According to the invention, there is also the possibility of producing the bolt as a rotating part in a radiographically detectable material.

The structures for protection against dislocation are preferably made in the form of a truncated cone or pyramid or in the form of cut spherical bodies.

The bolt insertion opening has an internal thread.

The previously described positioning instrument for handling the implant consists of a stem and a capsule, the capsule housing a key with a threaded end and the threaded end is formed complementary to the internal thread of the insertion opening in the bolt.

Furthermore, with a rotary movement the key with the threaded end can be moved longitudinally displaceable towards the capsule. At the anterior end of the capsule a stop surface for the implant is arranged, so that the implant held on the key is fixable by tension in the respective angular position on the bolt and the stop surface.

It has surprisingly been shown that there are ideal requirements for durable fusion by using the bioelastic synthetic material PEEK. The elastic characteristics similar to bone counteract the sunken implant and favor the tendency to fusion. Simultaneously, the radiographic transparency ensures an optimal postoperative diagnosis, that is to say without having to exist larger radiological windows in the implant material referring to the state of the art.

Suitable radiographic markers, also relatively small and appropriately positioned, made for example from titanium or titanium alloy material, facilitate the location of the implant at any time.

Regarding the application and use of the implant, the following deductions are indicated.

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The intervertebral disc compartment is first emptied through a transforaminal approach. In this case, suitable forceps or molded curettes known per se are used.

Once the discectomy has been carried out, the intervertebral disc compartment is distracted by means of special distractors to the desired height. An appropriate distraction height has been reached, when the distractor is under tension and a stable sensation is given in this regard. After distraction, the required implant size, in particular the implant height, is verified with the help of special trial implants. To hold these trial implants, the positioning instrument according to the invention can already be used.

Before implantation of the size-determined implant, the intervertebral disc compartment is preferably filled ventrally and on the opposite lateral side of the implant with a suitable material, e.g. ex. the fluffy. The dorsal area of ​​the implant is also filled.

For the implant that must also be filled, a filling resource is used, in which the implant is inserted. The filling resource here collects the outer contour of the implant and forms a holding frame.

After an appropriate angle between the instrument and the implant has been found with the aid of the positioning instrument and the locking possibility and the latter is subjected to a corresponding fixation, the implant is incorporated into the compartment of the intervertebral disc. Due to the implantation curve, it is advisable to adapt the angle during the implantation itself by a brief loosening taking advantage of the advantageous effects of the positioning instrument.

Definitive positioning can then take place with the aid of suitable straight or curved pushers. For correct implantation, the curved side of the implant points towards the ventral area and the two ends of the implant towards the dorsal area. In order to achieve all the desired advantageous effects, the implant should be positioned towards the ventral area if possible. After implantation, the remaining compartment of the intervertebral disc is filled to ensure safe fusion.

The principle of the implant according to the invention is based on the tension of the annulus and of the longitudinal bands if there is sufficient bone quality. In certain cases, additional stabilization with a dorsal fixator should take place.

As already mentioned, the implant can be made of a synthetic material, particularly PEEK. This material is radiographically transparent and its mechanical characteristics are very similar to those of the body. To facilitate postoperative diagnosis, radiographic markers can be inserted into the implant. One marker is for example on the medial ventral part of the implant in vertical alignment and another marker on the tip of the implant in horizontal sagittal alignment. Additionally, the swivel can function as a radiographic marker for housing instruments.

The invention is to be described in detail below by means of an embodiment example and with the aid of the figures.

Here they show:

Fig. 1 different representations of the implant according to the invention in the shape of a sickle and

Fig. 2 side view and perspective representation of the implant positioning instrument.

In the implant for transforaminal interbody fusion of lumbar vertebral column segments according to the exemplary embodiment, the surface areas directly in contact with the vertebral column have special structures 1 for protection against dislocation. These structures 1 can for example be formed as pyramidal stumps, truncated cones or cut spherical bodies.

The body of the implant itself has a sickle shape, the sickle arch 2 being oriented ventrally and the inner side of the sickle 3 dorsally in the case of application.

At one end of the sickle there is a connecting piece 4, the other end of the sickle opposite this connecting piece having a beak shape 5 ending in a point.

At least one filling opening 6 is provided between the walls of the sickle.

The connecting piece 4 is designed as a tilting or rotating bolt which is located in a corresponding notch 7 in the implant.

Extending essentially perpendicular to the longitudinal axis of the bolt, it has an insertion opening 8 with an internal thread (not shown).

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The insertion opening 8 serves to receive a corresponding end 9 of the positioning instrument 10 (Fig. 2).

Different radiographic markers not shown in the figures can be inserted into the body of the implant preferably made of a synthetic material, so that a postoperative localization of the implant can take place at any time.

The positioning instrument 10 according to FIG. 2 consists of a grip 11 with a capsule 12.

A key with a threaded end (part 9) is guided in the capsule 12, the threaded end being formed with respect to the internal thread of the insertion opening 8 complementary in the bolt.

By a rotary movement in the cap 14, the key 9 with the threaded end can be moved.

At the anterior end of the capsule 12, a stop surface 13 for the implant is arranged, so that the implant held on the key 9 can be fixed in the respective angular position on the bolt and the stop surface 13.

Documents cited in description

This list of documents related by the applicant has been compiled exclusively for the information of the reader and is not part of the European patent document. It has been made with the greatest diligence; However, the EPO does not assume any responsibility for eventual errors or omissions.

Patent documents related in the description • DE 4328062 A1 [0005] [0005] • US 20040153065 A1 [0009] • DE 4423257 A1 [0006] • WO 0217823 A1 [0010] • DE 19519101 A1 [0006] • EP 1290985 A2 [ 0011] • DE 19509317 A1 [0006] • WO 2005041825 A [0012] • DE 29616778 U1 [0007] [0008].