Patent Application
20230103485
This application claims priority to German application No. 102021211157.2, filed on Oct. 4, 2021, the entire disclosure of which is incorporated herein by reference.
The present invention relates to an implant system for treating fractures of a curved bone structure, in particular broken ribs in the chest region. The invention further relates to a method for production of such an implant system.
US 2021/0298808 A1 discloses a sternum replacement plate having a central region and rod-like extensions. The extensions are thicker than the central region, such that the central region is bendable about a flexion axis.
US 2018/0360506 A1 discloses a bone fixation device having two rigid endpieces which are connected via an elastic connection region of wires.
A chest injury is understood as damage to the osseous thoracic cage and to all of the organs and organ systems contained in the latter. Chest injuries occur mainly in the context of violent impacts involving damage to multiple regions of the body. While isolated chest injuries are a rare occurrence, almost half of all patients suffering polytrauma present at the same time with a chest injury. Polytrauma is the term used when multiple regions of the body or multiple organ systems are affected, where one of the injuries on its own or the combination of the injuries is life-threatening. The chest is composed of the thoracic spine, the sternum, and twelve pairs of ribs. In the cranial direction, the chest is delimited by the superior aperture of the thoracic cavity, which is formed by the first thoracic vertebra, the two first ribs, and the upper part of the sternum. It constitutes the connection between the connective tissue spaces of the neck and of the thoracic cage. The caudal limit of the chest, the inferior aperture of the thoracic cavity, constitutes the boundary between the thoracic space and the abdominal space. It is formed by the 12th thoracic vertebra, the 11th and 12th ribs, the cartilage parts of the 7th to 10th ribs, and by the inferior margin of the sternum. The boundary structure between thoracic space and abdominal space is the diaphragm, which stretches between the aforementioned parts of the skeleton. The ribs are connected to the spinal column via the costovertebral joints and also to the breastbone via the sternocostal joints.
In interaction with the thoracic cage muscles, which lie between the ribs and fill the regions between the ribs, called the intercostal spaces, the joints play a central role in the mechanism of respiration. Since the thoracic cage also accommodates vital organs such as the heart and lungs and important pathways, it also serves as a protective framework.
During inhalation, expansion of the heads of the ribs in the costovertebral joints causes the ventral sternal ends of the ribs to lift. In parallel with this, the diaphragm lies deeper as a result of contraction. This results in an increased volume of the chest. During exhalation, the ventral sternal ends of the ribs fall again and the diaphragm muscles relax, such that the chest returns to its original volume. Of all the fractures in the chest region, rib fractures are the most common.
Fractures of this kind, such as those of the ribs, can be fitted for example with metal implants for treatment and bone reconstruction. Use is made, for example, of Kirschner wires which, in a procedure called K-wire osteosynthesis, are able to fix the fractures in question. However, after being introduced into the bone, these wires can sometimes migrate, particularly into bone cavities, and they are also not free from failure. Moreover, when using K-wires, immobilization often requires additional fixing by plaster cast, which makes the treatment of chest injuries more difficult.
Fractures can also be treated using metal splints, but these permit only insufficient suppression of pain. In the case of rib fractures, this suppression of pain cannot even be fully achieved by using rib clips, and these moreover do not provide for a controlled movement in the fracture gap. Overall, primary bone healing is at any rate also very difficult here.
A further possible way of fixing the aforementioned fractures is by plate osteosynthesis by means of plates or splints. In this context, DE 38 03 435 C1 discloses an implant splint with a side face that is adapted to the contour of a rib. A possible disadvantage of plate osteosynthesis is that the respiratory mechanism of the thorax may be impaired by the stiffness of the implant. Particularly in the case of bones with osteoporosis, loosening of screw-type fastenings may also occur at the transition to the non-rigid rib region.
The object of the present invention is therefore to make available an implant system which treats a fracture of a bone structure safely and in a manner free from failure and, while providing good bone healing and suppression of pain, at the same time permits a controlled movement in the fracture gap.
With the implant system according to the invention, an implant body can be arranged on the curved bone structure in a way which, for example by bending, imitates the curvature of the bone structure or at least partially encloses or surrounds the bone structure by twisting of the at least one middle piece, such that, on the one hand, the fragments of the bone structure are securely held and, on the other hand, a controlled movement of the bone structure as a whole is permitted without impeding the healing process, which is to say that the implant system permits a controlled elastic movement of the affected bone fragments of the bone structure. By virtue of the elastic configuration of the at least one middle piece, the holding pieces can be arranged in different positions relative to each other on the bone structure and optionally secured, whereas the middle piece or middle pieces is/are flexibly molded onto the bone structure. The implant system according to the invention is particularly suitable for treating damaged bone structures in the chest region, i.e. damaged rib bones, but is not limited thereto.
An embodiment with a middle piece and with two holding pieces located at the ends of the latter has already been described, but other configurations are also conceivable. Thus, the holding pieces can be adjoined by further elastic middle pieces, which in turn can be followed again by holding pieces. It is also conceivable for one or other piece to be omitted, such that a juxtaposition of middle pieces and holding pieces is conceivable which can engage once or even several times around a wide variety of bone structures of changing circumference and of great longitudinal extent.
In an advantageous development of the implant system according to the invention, which has a high degree of flexibility and permits good handling in terms of the arrangement of the implant body on the bone structure, the implant body, with its rod-like longitudinal extent, can have at least one region whose side edges have an undulating configuration, in particular a uniformly undulating configuration, on at least two mutually opposite sides. In this case, the at least one middle piece and also one or more holding pieces can be designed individually, but also jointly, with the aforementioned undulating shape.
Particularly preferably, in a development permitting simplified production, the at least one middle piece and the at least two holding pieces can have substantially the same outer contour, that is to say, for example, the identical uniform undulating shape at their side edges. However, in terms of their shape, the holding pieces can also differ from one another and also in each case from the at least one middle piece.
In one advantageous embodiment, a possibility of adapting the properties of the implant body of the implant system according to the invention to the conditions of the bone structure, and to the degree of damage of the latter, is one in which the thickness and/or length of the holding pieces and/or of the middle piece are different and/or variable. The variability of the holding pieces and middle piece means that the implant body in question is able to be individually adapted by measuring the respective situation. In simplified developments of implant bodies, the holding pieces for example can be designed identically in pairs.
In one development, in which on the one hand the middle piece affords a high degree of flexibility and, on the other hand, the holding pieces are very stable, the holding pieces can be designed with an increased thickness in relation to the at least one middle piece, such that they have a reduced pliability.
In order, on the one hand, to be able to connect the middle piece and the holding pieces of the implant body, particularly when the pieces have different thicknesses, in a way that does not require any unnecessary projections or steps, and, on the other hand, if necessary or desired, to provide the holding pieces with a preferred orientation by arranging them at an angle to the at least one middle piece, an advantageous development of the implant system according to the invention is one in which a transition region can be provided between at least one of the holding pieces and the at least one middle piece. For this purpose, the transition region can, for example, have at least one portion arranged at an angle to the longitudinal extent, although the transition region can also form a simple narrowing of the thickness of the cross section from the thickness of the at least one middle piece to the thickness of the respective holding piece. A transition region is likewise conceivable in which a flat face of the at least one middle piece and a flat face of the holding pieces, in particular the flat face for resting on the bone structure, lie in one plane.
As regards their dimensions, the middle piece and the holding pieces are intended to be subject to no limitations other than those of the environment in which they are used. However, with respect to individual directions of extent, certain dimensions are particularly preferred. Thus, the length of the implant body can preferably be between 1 mm and 300 mm, the length of the at least one middle piece can be between 1 mm and 50 mm, its thickness can be between 0.1 mm and 3.5 mm, while the thickness of the holding pieces can be 0.5 mm to 4.5 mm. The corners formed in the case of an undulating configuration of the side edges of the implant body can have rounded shapes in the region of between 0.01 and 4.5 mm. Moreover, it is conceivable that the stated dimensions can vary over their respective directions of extent.
In order to easily hold the implant body firmly in place in an expedient development of the implant system according to the invention, at least one fastening means can be arranged between the implant body and the bone structure.
The at least one fastening means is preferably formed with one or several spikes, points, hooks or similar projections which are configured to penetrate into the bone structure. Projections of this kind can be provided both on the at least one middle piece and on the two holding pieces, and both on the face directed toward the bone structure, where they penetrate into the bone structure, and on the face directed away from the bone structure, where they are able to fix the surrounding tissue. Another preferred development may be one in which screws engage, by way of receptacles provided for this purpose, on one or more of the holding pieces and thus fasten these to the bone structure. Receptacles for the passage of screws or of similar fastening means can also be provided on middle pieces.
In order for the particular and if appropriate individually manufactured implant body to be able to be suitably adapted to the particular situation, for example in terms of specifically chosen material properties such as fatigue resistance, flexibility, ideal elastic modulus or strength, another advantageous development of the implant system according to the invention is one in which the implant body can be made from at least one high-performance polymer or composites thereof. Particularly preferably, the at least one middle piece and the holding pieces can each be made from a thermoplastic such as a polyether ether ketone (PEEK) material, a polyether ketone ketone (PEKK) material, a polyphenyl sulfone (PPSU) material, a polyethylene (PE) material and compounds of the abovementioned materials with hydroxyapatite, tricalcium phosphate, strontium, magnesium and the like. However, further materials are also conceivable, and the above list is not exhaustive.
Particularly in the case of individual manufacture of the implant body, for example for treating complicated fractures or those with a poor healing prognosis, the at least one middle piece and the holding pieces can have, on their face in each case directed toward the bone structure, a surface that is adapted to the associated bone region and that permits still more exact adaptation.
Moreover, the object can also be achieved by a method for production of an implant system for treating fractures of a curved bone structure. It is likewise conceivable to produce the final shape of the implant body, and also the final shape of the at least one elastic middle piece, by reworking an implant body blank that has been obtained in a primary forming method. Such reworking can, for example, involve a cutting operation in which the blades of a tool are used to mechanically cut away material from the blank in order to change the workpiece shape and (or) workpiece surface. The material removal can take place for example as a milling procedure using geometrically defined blades; such a manufacturing method can permit a high degree of manufacturing precision.
In this way too, an implant system can be made available which treats a fracture of a bone structure safely and in a manner free from failure and, while providing good bone healing and suppression of pain, at the same time permits a controlled movement in the fracture gap.
The embodiments and developments above may be combined arbitrarily with one another insofar as is rational. Further possible embodiments, developments and implementations of the invention also encompass combinations, not explicitly stated, of features of the invention that are described above or below in relation to the working examples.
In all of the figures, identical or functionally identical elements and devices are provided with the same reference signs, unless indicated otherwise.
The implant system 100 according to the invention solves the problem mentioned at the outset through the combination of an innovative and flexible design and the specifically chosen material properties, such as fatigue resistance, flexibility, ideal elastic modulus, material strength. It is thus possible to ensure a controlled load distribution and also controlled movement of the dynamic chest cavity, which, in contrast to a stiffer metallic system, promotes bone healing.
Although the present invention has been described above on the basis of preferred exemplary embodiments, it is not limited thereto and instead can be modified in a variety of ways. In particular, the present invention can be changed or modified in a variety of ways without departing from the core of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021211157.2 | Oct 2021 | DE | national |
