JP5276799B2 - Longitudinal material for use in spine or trauma surgery and stabilizing device comprising such a longitudinal material - Google Patents

Abstract

A stabilizing apparatus for a spinal or trauma surgery is provided to fix a fractured bone reliably by using a longitudinal member instead of a polymer rod. A stabilizing apparatus for a spinal or trauma surgery uses an extruded rod(1) for fixing a fractured bone. The stabilizing apparatus includes at least two multi-axis bone fixing members(14,14'). A shaft(15) having a screw line and a spherical head(16) are arranged on the respective bone fixing members. The spherical head is arranged at one end of the shaft. The head is pivotably arranged inside a container(17). The rod is contained in a recess inside the container. A pressure member applies a pressure on the head, so that the head is fixed at predetermined angle positions in the container. A locking member fixes the rod in the recess.

Description

  The present invention relates to a longitudinal member for use in spine or trauma surgery and a stabilizing device comprising such a longitudinal member.

A mechanical stabilization system for a vertebral column with a flexible rod made of an elastic material and a fixation device for fixing the rod to the spine is known in European Patent 1364622A2 and European Patent 1527742A1, respectively. The material of the rod is a polymer material that can be adapted to a living body without causing a rejection reaction, for example, a material mainly composed of polyurethane. The rod has a corrugated surface with corrugations extending in a direction transverse to the rod axis.
European Patent 1364622A2 European Patent 1527742A1

  Usually, the elastic member is manufactured by injection molding. Thereby, the molten plastic material is poured into a mold having a shape opposite to the desired shape at high pressure. As shown in FIG. 1, after injection molding, the polymer chains 100 of the material are intertwined and may include filler particles 101 and cross-linking groups 102 therein.

  The rod 103 made by injection molding is not homogeneous in the sense that it has defects in its macromolecular structure because it has an isotropic structure of polymer chains. Known elastomeric rods exhibit a local flow of material when pressure is applied on their surface in the process of securing the rod in the receiving portion of the bone anchoring element. This local flow of material can cause loosening of the fixation of the rod within the bone anchoring element.

  The object of the present invention is to provide a longitudinal member for use in spine or trauma surgery with improved mechanical properties and reduced manufacturing costs compared to known polymer rods and such a longitudinal member. It is to provide a stabilization device.

The foregoing objects are achieved by the according stabilizing apparatus vertically material and claim 6 according to claim 1. Further developments are achieved in the dependent claims.

  Longitudinal materials have the advantage that the tendency to flow when secured to a bone anchoring device is reduced compared to known injection molded elastomer rods. Also, the longitudinal material in the form of an extruded elastomer rod exhibits low permanent curability, which is characterized by the fact that deformation remains after the deformation stress is removed, and Rods of the same size exhibit a high rigidity characterized by an elastic modulus compared to injection molding. Therefore, under the same load conditions, a small size injection molded elastomer rod can be used. Also, the strength and wear resistance against mechanical tension and / or compression loads are improved. Manufacturing costs are reduced for the necessary tools and equipment, which is low in cost compared to the cost produced by injection molding.

The rod can be cut to a desired length before and during surgery.
Additional features and advantages of the present invention will be clearly understood by reference to the detailed description of embodiments taken in conjunction with the accompanying drawings.

  3 to 5 show an embodiment of the present invention used as the spine rod 1. The rod has a substantially circular cross section and a length suitable for being made over a distance between at least two vertebrae. The diameter of the rod can be selected to be compatible with the diameter of known metal spine rods. In this case, the rod 1 can be connected to a known bone screw. In the embodiment shown, the rod cross-section is constant over the entire length of the rod.

The rod is made of a biocompatible plastic material that can be shaped by extrusion. For example, the material may be, for example, a thermoplastic material such as polyallyl ether ketone (P EEK). The material is preferably flexible, such as an elastomer. Suitable elastomers include, for example, polymer materials based on polyurethane, polycarbonate urethane (PCU) or silicone (silicon resin). The rod exhibits three-dimensional elasticity in such a manner that a restoring force acts when the rod is placed under a load that restores the original shape of the rod.

  In particular, as can be seen from FIGS. 3 and 4, the macromolecular structure of the rod 1 is characterized by a polymer chain 2 of elastic material that is substantially aligned with the length of the rod 1. Therefore, the macromolecular structure of the rod is substantially uniform in the length direction. The polymer chain 2 constitutes a fibrous structure with the fibers oriented in the length direction and thus load oriented.

  The rod 1 is preferably manufactured by extrusion. In the known extrusion manufacturing process, a solid or flowable raw material is filled into an extruder and then extruded through an opening. Parameters such as temperature and pressure during the extrusion process depend on the materials that will be used and recognized by those skilled in the art.

  Therefore, the rod 1 can be distinguished from a conventional rod made of the same material but manufactured by injection molding, as shown in FIG. A rod formed by extrusion molding has improved mechanical strength as compared with a rod manufactured by injection molding using the same material. For example, the strength against mechanical tensile and / or compressive loads is increased. Also, wear resistance is increased. Therefore, the life of the rod graft is extended.

  The rod may have a shape other than the circular cross section. As can be seen in FIGS. 6a-g, for example, a circle (FIG. 6a), a square (FIG. 6b), a square with rounded corners (FIG. 6c), an ellipse (FIG. 6d), a rectangle (FIG. 6e), Different cross-sectional shapes are possible, such as a rectangle with rounded corners (FIG. 6f), a star (FIG. 6g), or a triangle. The cross section is preferably constant over the entire length of the rod. If the cross-section of the rod is not circular, rotation of the rod within the bone anchoring element to which the rod is connected can be prevented. Also, the cross-sectional shape can be used to achieve bending properties in bending / extending motion and lateral bending that can be different from each other.

The stabilization device using the rod according to the invention comprises at least two bone anchoring elements for the connection of the rod to the bone. As can be seen in FIGS. 7 and 8, according to the first example, the bone anchoring element is a single axis bone screw 10, 10 ', each of which is anchored to the spine. A threaded shaft 11 that can be provided and a receptacle 12 that is rigidly connected to the threaded shaft. The receiving part 12 has a substantially U-shaped recess for receiving the rod 1. A clamping element, for example an inner screw that is screwed into the recess, or an outer nut 13 as shown, is provided to fix the rod 1 in the recess. The anchoring element is made of a biocompatible hard material such as a biocompatible metal such as titanium or a metal alloy.

  In use, first the bone anchoring element 10, 10 'is screwed into the spine to be stabilized. The rod 1 is then inserted into the receiving part 12 and, after adjustment for its positioning, is fixed in the receiving part by means of a clamping element 13. Due to the non-uniformly aligned macromolecular structure of the rod, the tendency to flow under the pressure of the locking element is reduced. Therefore, the risk of loosening of the fixation between the rod and the bone anchoring element is reduced. The spine can be mechanically stabilized because the rod exhibits elasticity under flexion, extension and torsion of the spine. The elasticity that may be required for certain applications is obtained by selecting the material and / or size and / or cross-sectional shape of the rod made by extrusion.

  In the stabilization device of FIG. 7, the rod 1 is used in a straight state. The spine can perform limited motion in all planes controlled by the elasticity of the rod.

  FIG. 8 a shows a second example of a stabilization device using an extruded rod 1. The stabilization device has at least two polyaxial bone anchoring elements 14 and 14 ', one at each end with a threaded shaft 15 to be anchored in the bone. And a certain spherical head 16. The head 16 is rotatably held in a receiving portion that receives the rod in the recess. A pressure element (not shown) is provided, and it is preferred that pressure be applied to the head such that the pressure element is held in the receptacle at its angular position. A clamping element (not shown) is also provided to secure the rod in the recess.

  In use, as in the first example, the bone anchoring elements 14 and 14 'are screwed into the spine and then inserted into the rod. The head 16 is rotatably held in the receiving portion 17 and the position of the receiving portion can be adjusted relative to the head. After adjustment of the position of the receiving part relative to the head and the position of the rod relative to the receiving part, the connecting part is tightened by the tightening element.

  FIG. 8b generally shows the forces acting on the rod under axial load (A) and bending load (F) during the movement of the spine shown in FIG. 8a. As can be seen in the figure, the force component consisting of the axial load and the bending load is mainly directed in the direction of the alignment of the polymer chains 2. This constitutes an extruded rod that is particularly suitable for use in the mechanical stabilization of the spinal column. This also applies to the stabilization device shown in FIG. 7 using uniaxial screws.

  9 and 10 show an example of the medical use of the adjustment device. A correction device comprising two bone anchoring elements 10 and an extruded rod is applied to the spine where symptoms of scoliosis are observed. The elastic rod is bent from a neutral straight shape to fit the spinal deformity curve as shown in FIG. By reducing the distance between the screw heads of the correction device as indicated by the arrows in FIG. 9, a preload is generated in the rod to drive the deformed portion of the spine to a straight position as shown in FIG. The Uniaxial or polyaxial screws can be used for the bone anchoring element. Multiaxial screws have the advantage that the shaft and head can be aligned to receive the rod.

FIG. 11 shows a schematic view in the direction of the longitudinal axis of the spine of one bone anchoring element anchored in the spine. The extruded rod is clamped in the receiving part 12 by the fixing element 13. The polymer chains 2 are substantially aligned in the length direction of the rod. If required, additional fixation in the bone can be provided by the clamp 20.

  FIG. 12 shows a variant of the bone anchoring element with the rod inserted into the recess of the receiving part. The receiving part 18 includes a recess 19 having a cross section different from the cross section of the rod. In the example shown, the cross section of the recess is elliptical, while the cross section of the rod is circular with a diameter smaller than the diameter of the recess. Fixing can be achieved directly via a clamping element (not shown) or with a filling piece (not shown) between the clamping element and the rod.

  The present invention is not limited to the embodiment and application examples described above. The features of the examples described above may be combined with each other. Although the rod is shown connected to two bone anchoring elements, it may have a sufficient length to connect to two or more bone anchoring elements. Since the rod is made of an elastomer, its length can be adapted before or at the time of surgery by cutting the rod.

  The rod may be made entirely or partially of a polymeric material. For some applications, it is fully contemplated that a portion of the entire rod is made of an extruded polymeric material. The length of the cross section depends on the specific application and the required flexibility. For example, an anisotropic cross section such as a rectangle can be used to provide a rod with elastic properties that vary depending on direction.

  The rod may be hollow and may include a core inside the hollow to obtain additional properties.

  According to the manufacturing method of extrusion molding, it is possible to produce rods having different cross-sectional shapes and diameters at low cost. This is because there is no need to use complicated molds and expensive equipment as in injection molding.

  All known types of rods can be used for the bone anchoring element. Typically, the one having a known metal rod is used.

  Also, the present invention is not limited to applications for the spine. The rods can also be used to stabilize fractured bones instead of metal rods, for example in fixture externe or intern.

  The term polymer material as described above means a mixture of polymer materials comprising a single polymer material or copolymer and so-called block copolymers having hard and soft parts. The polymeric material may also contain additives such as filler particles or carbon fibers or other reinforcing fibers. Reinforcing fibers can be used to enhance their synthesis if required.

It is a general-view figure which shows arrangement | positioning of the polymer chain of the polymer plastic material after injection molding. 1 is a schematic cross-sectional view of a spinal rod made of a polymer plastic material produced by injection molding. 1 is a perspective view of a rod according to the present invention. FIG. FIG. 4 is a schematic cross-sectional view of the rod according to FIG. 3 when viewed in a plane including the longitudinal axis of the rod. FIG. 4 is a schematic cross-sectional view when viewing the rod according to FIG. 3 in a plane perpendicular to the longitudinal axis. (A)-(g) has shown the example of the cross section of a rod. FIG. 3 shows a stabilization device for a spinal column including a rod and two uniaxial bone screws according to the present invention. FIG. 3 shows a stabilization device for a spinal column including a rod and two polyaxial bone screws according to the present invention. It is a figure which shows roughly the force currently acting on the rod under an axial load and a bending load. FIG. 3 shows that the rod according to the invention is in a first prestressed state when the stabilization device according to the invention is applied to the vertebral column for the purpose of correcting spondylolisthesis. FIG. 10 shows the stabilization device of FIG. 9 in a second state. FIG. 3 is a schematic view showing a bone screw and clamp fastened in a spine and fixing a rod. It is a figure which shows the modification of the bone anchoring element which has received the rod.

Explanation of symbols

  1 vertical member, 2 polymer chain, 12, 17, 18 receiving part, 19 concave part.

Claims (8)

A longitudinal member (1) for use in spine or trauma surgery sized over a distance between at least two vertebrae or two bones,
The longitudinal member consists of an extruded polymer material over its entire length ,
The longitudinal member exhibits bending elasticity and axial elasticity,
The polymer chains (2) of the material are substantially aligned in the longitudinal direction of the longitudinal member (1), the longitudinal member having a uniform cross section in the longitudinal direction;
A vertical material in which the polymer material is a polymer mainly composed of polyurethane, polycarbonate urethane (PCU), or silicone (silicon resin), and the vertical material (1) is made of only an elastomer over the entire length.   The longitudinal member according to claim 1, characterized in that the longitudinal member (1) is obtained by extrusion. Wherein a longitudinal member (1) is a rod, stringer according to claim 1 or 2. The cross-section of the longitudinal member is substantially circular, longitudinal material according to any one of claims 1-3. A stabilization device for stabilizing vertebrae or bones,
Comprising at least two bone stabilizing element having a receiving portion for connecting to the shaft and the longitudinal member for fixing in the bone, the longitudinal member is the bone fixing element according to any of claims 1-4 A stabilization device provided to connect each other. The receiving portion (12, 17, 18) includes a recess (19) for receiving the longitudinal member, and a partial cross section of the recess (19) for receiving the longitudinal member is different from a section of the longitudinal member. The stabilization device according to claim 5 . A method for producing the longitudinal member according to any one of claims 1 to 4 ,
Providing a polymeric material comprising a biocompatible elastomer;
Wherein the shape of the longitudinal member has a front Kipo Rimmer material characterized by the steps of extrusion molding method for manufacturing a longitudinal member. The method for producing a vertical member according to claim 7 , wherein an elastomer material such as a polymer mainly composed of polyurethane, polycarbonate urethane (PCU) or silicone (silicon resin) is used.

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