WO2021260063A1

WO2021260063A1 - Elongation device for small tubular bones

Info

Publication number: WO2021260063A1
Application number: PCT/EP2021/067243
Authority: WO
Inventors: Augustin Betz
Original assignee: Augustin Betz
Priority date: 2020-06-23
Filing date: 2021-06-23
Publication date: 2021-12-30
Also published as: DE102020116489A1; EP4164525A1

Abstract

The invention relates to an elongation device for a minimally invasive elongation of small tubular bones, said device being used to allow two bone parts secured to the device to be moved apart step by step by a specifiable distance by means of an axial manual actuation. The structure according to the invention provides a miniaturized highly integrated distraction device for minimally invasive interventions, said device allowing a high degree of daily comfort for the patient and continuous mobility. The device can be introduced into tubular bones axially through a joint surface for example by virtue of the miniaturized structure and can be removed again in order to achieve a maximum degree of minimal invasiveness and daily comfort for the patient.

Description

Extension device for small tubular bones

The invention relates to an extension device for minimally invasive Ver lengthen small tubular bones, in particular metatarsal, metacarpal, finger and / or toe bones.

Shortened small tubular bones on the metatarsus and metacarpal as well as on the toes and fingers - mostly congenital - lead to functional and aesthetic problems.

An operation can significantly improve function and cosmetic appearance. These shortened long bones can be lengthened in two ways, on the one hand by inserting foreign or own bones and on the other hand by so-called callus distraction.

The disadvantage of the method of inserting foreign or own bones is the acute strong increase in the soft tissue tension when the bone parts are pushed apart to insert the bone spacer. All neighboring structures such as muscles, tendons, vessels, nerves and the slack are affected by the high soft tissue tension. This can lead to tissue death due to partial or total reduced blood flow or serious deep infections due to a blood circulation stop, loss of correction due to a collapse of the implant, loss of function due to the necessary accompanying surgical tendon lengthening and poor healing of the inserted bone. No tubular bones are available for the use of the body's own bones, only cancellous bones. This predominantly cancellous bone has only a low level of strength, which often results in a collapse with a loss in length of the bone structure. This leads to an unsatisfactory surgical result and requires another surgical correction. This problematic disadvantage in the structural strength of the bone does not occur with a donor long bone, but immunological rejection reactions can occur, which can lead to problems with the healing of the bones and even infections that require bone removal, which at best sets the initial situation can be achieved again. In this procedure, the bone segment is fixed by means of a wire inserted centrally into the medullary cavity through the joint surface, which is removed again after healing.

In the procedure by means of callus distraction, which leads to a slow and therefore gentle lengthening of the soft tissue structures and the bone with a continuous formation of new bone substance, external fixation systems are used which, after the bone has been severed, serve to stabilize and continuously adjust the length. The outer holding systems have fixation elements that lead through the skin and soft tissues to the bone and fix the bone, but create a risk for germs to penetrate along the connecting elements to the bone due to an unavoidable bacterial load and, in the event of an infection, cause inflammation to loosen them the connecting elements in the bone can lead. This represents a frequent and serious complication with this method of treatment. The external fixation systems also have the disadvantage that it is not possible to wear shoes and a permanent dressing arrangement with daily wound care is required. This results in a severe reduction in suitability for everyday use and comfort.

The object of the present invention is therefore to realize a gentle, comfortable, low-pain, not susceptible to infection and less stressful possibility for lengthening small tubular bones in the form of a miniaturized, fully implantable extension device. This object is achieved by an extension device with the characteristics of claim 1 and in particular in that the extension device extends along a direction of extension and has a first fastening element for fastening to a first bone part and a second fastening element for fastening to a second bone part , in order to bridge a bone gap between the first bone part and the second bone part, wherein the second fastening element is connected to the first fastening element via an adjusting element and wherein a distance between the two fastening elements along the extension direction is gradually increased by, in particular manually, pulling on the first fastening element and / or the second fastening element can be enlarged. The setting element has a blocking section which is designed to block a relative movement of the first fastening element and the second fastening element directed towards one another and to enable the distance between the two fastening elements to be increased by pulling.

Since the extension device has a first fastening element and a second fastening element, the distance between which is gradually enlarged, the extension device can initially be fastened to the respective bone parts in the course of an operation with the two fastening elements, which then during the treatment by pulling on the first Fastening element and / or the second fastening element can be removed from each other. The pulling movement can be carried out by the patient himself, in particular by manually pulling on an extremity connected to the extension device, for example on a front phalanx of a finger to be extended, in order to successively increase the distance between the fastening elements and thereby increase the bone extend. The possibility of increasing the distance between the fastening elements by pulling and, in particular, manual pulling, enables the extension device to be operated easily and conveniently.

Furthermore, it enables the actuation of the extension device by pulling to use a mechanism that is easy to manufacture. It is sufficient here to design the setting element with the locking section in such a way that a translational extension movement is permitted in the extension direction and a movement in the opposite direction is blocked in order to reliably prevent an unintentional retraction of an extension that has already taken place. In addition, due to the simple mechanics, the extension device can be designed with a minimal number of components, in particular the two fastening elements and the adjustment element, which in particular can enable the extension device to be miniaturized for use even with small bones. It can be provided that only pulling movements or translational movements are required to actuate the extension device or to increase the distance between the fastening elements.

By means of such an extension device, a miniaturized, highly integrated distraction device for minimally invasive interventions can consequently be implemented, which allows the patient a high level of everyday comfort and can ensure continuous mobilization. In addition to the increased comfort, even when the extension device is operated to increase the distance between the fastening elements, the healing process can also be significantly accelerated. Miniaturization of the extension device can also make it possible to insert the extension device axially through an articular surface into small tubular bones and, after the desired elongation of the bone has been achieved, to remove it again through the articular surface. For the patient, an optimum of minimally invasive vity and everyday comfort can be achieved and the operation required to set the extension device can be carried out extremely quickly and without the need for any preparatory interventions or measures. Furthermore, the simple mechanical design makes it possible to use highly corrosion-resistant materials and to make the extension device permeable to body fluid, so that a gas-filled space within the extension device can be avoided. In particular, a change in air pressure prevents the escape of gases or possibly aged body fluids affected by corrosion, which can lead to extreme pain at greater geodetic heights, such as during a flight or when staying in the mountains. Furthermore, with a highly corrosion-resistant design, the extension device can also remain indefinitely in the extended bone if this is necessary in medically indicated cases, so that removal of the extension device after the end of the treatment is not absolutely necessary.

In the case of the gradual lengthening or enlargement of the distance between the fastening elements, provision can also be made for the distance to be increased by a predetermined travel distance with each pull. This can enable a simple agreement of the operation of the extension device or the treatment between a treating physician and a patient by, for example, the speed at which a bone is to be extended can be clearly coordinated and implemented in an uncomplicated manner. To do this, the patient only has to carry out an agreed number of actuations or pulling movements per unit of time and a current length of the lengthening device or the bone to be lengthened can be documented at any time by the number of actuations that have taken place. Here it can be provided, for example, that the travel is about 0.5 mm and total extensions of 1 cm to 3 cm can be achieved in order to be able to lengthen a small tubular bone.

While the lengthening device thus provides a convenient way of lengthening bones, the locking section of the adjusting element can ensure that there is no undesired reduction in the spacing between the fastening elements. Unwanted or incorrectly agreed or not deliberately executed extensions can be reliably prevented in that a permanent force is exerted on the fastening elements, which presses the fastening elements against one another. Since this force can be absorbed by the locking section, the fastening elements can be tightened to a certain extent at a set distance during mobilization, so that the distance to lengthen the bone can only be increased by conscious pulling. It was recognized that the necessary or sufficient force can already be exerted automatically by the tissue tension, so that in principle further components for fixing the extension device can be dispensed with when the fastening elements are at a desired distance from one another. However, it is possible to equip the extension device with a component for exerting a force on the fastening elements and to reinforce the force exerted by the tissue tension. For example, the distance can be increased against a bias voltage of a spring via which the two fastening elements are connected to each other.

It is to be expected that this extension device will enable a treatment method for the correction of shortened small tubular bones, such as metatarsal, metatarsal, finger and toe bones, which every other previous surgical treatment method due to the minimally invasive procedure, short recovery times, the complication-free Bone healing as well as the high functional onality during the treatment phase and in the long-term outcome of the treatment will be superior.

Further embodiments can be found in the dependent claims, the description and the figures.

In some embodiments, the first fastening element can have a plurality of locking recesses arranged one after the other in the direction of extent, wherein the locking section can engage in a respective locking recess. In particular, the one of the locking recesses, in which the locking section engages, depend on the distance between the two fastening elements and the locking section can by pulling on the first fastening element and / or the second fastening element along the extension direction from the respective locking recess in a subsequent locking be transferred. Correspondingly, the distance between the locking recesses can in particular predetermine an adjustment path by which the distance between the fastening elements increases each time the extension device is pulled or actuated. The locking section can be designed in such a way that the engagement in the respective locking recess blocks a relative movement of the fastening elements towards one another, but the locking section is brought out of engagement with the respective locking recess by pulling on the first fastening element and / or the second fastening element and into a subsequent locking recess can be transferred. For example, the distance between the locking recesses can be about 0.5 mm and the locking recesses can have an extension of about 0.5 mm in the extension direction of the extension device.

For example, the locking recesses can be designed as openings into which the locking portion engages transversely to the extension direction of the extension device. As an alternative to full openings, the locking devices Recesses can also be designed as depressions with a bottom or a maximum depth, which can be introduced, for example, on a wall of the first fastening element.

As an alternative to embodiments with locking recesses formed on the first fastening element, in other embodiments it can be provided that several locking lugs are arranged in the direction of extension on the first fastening element, wherein the locking section can have a blocking recess into which a respective one of the locking lugs engages . Here, too, a respective one of the locking lugs can engage in the blocking recess, in particular depending on the distance between the two fastening elements. The locking lugs and / or the blocking recess can be designed in such a way that the engagement of the respective locking lug in the blocking recess blocks movement of the two fastening elements towards one another, but allows the distance between the fastening elements to be increased by pulling. The blocking recess can be moved along the direction of extent by pulling in such a way that, as a result of the pulling, a subsequent locking lug engages the blocking recess in order to set the increased distance between the fasteners' rule.

The locking lugs and the blocking recess can cooperate in a manner basically similar to that of the locking section and the locking recesses of the embodiments mentioned first. Developments described herein of embodiments with locking recesses on the first fastening element can therefore in principle also be implemented in a corresponding manner in embodiments with locking lugs on the first fastening element. It can be provided that the locking section can be transferred from the respective locking recess into a subsequent locking recess by pulling on the first fastening element and / or the second fastening element. As mentioned, the distance between the locking recesses can specify an adjustment path by which the distance between the fasteners increases with each step. As a result, in particular the speed of the bone lengthening can be given as a number of successive transfers of the locking section into subsequent locking recesses per unit of time, so that the treatment can be discussed in a simple and unambiguous manner between the attending physician and a patient and the patient can use the actuations Extending can do it yourself.

In order to be able to check and document the enlargement of the distance between the fastening elements by a respective step, the reaching of a subsequent locking recess or the engagement of the locking section in a subsequent locking recess can be perceptible, for example, haptically and / or acoustically. For example, it may be necessary to apply an increased force at the beginning of the transfer of the locking section from the respective locking recess into the subsequent locking recess in order to first disengage the locking section from the respective locking recess. This increased force can be noticeable, for example, when a subsequent locking recess is reached, so that an unintentional jump over a locking recess can be prevented. As an alternative or in addition, the locking section and / or the setting element can, for example, strike a boundary when reaching the subsequent locking recess, whereby an audible noise, for example a click, can be generated.

In some embodiments, the locking recesses may have a respective stop surface on which the engaging locking portion with a Blocking surface can rest, wherein the stop surfaces can be aligned substantially perpendicular to the direction of extension. In particular, the blocking surface can also be oriented essentially perpendicular to the direction of extension. The application of the blocking surface to a respective stop surface can prevent a directed relative movement of the fastening elements, whereby the perpendicular orientation to the He stretching direction in particular an unwanted pushing out of the Sperrab section from the respective locking recess can be prevented. In particular, the blocking surface can be provided at an end of the setting element opposite the second fastening element, so that the second fastening element can be supported on the first fastening element or in a respective blocking recess via the blocking surface formed at the end of the setting element To fix the distance between the fastening elements and thereby the length of the extension device.

In some embodiments, the locking recesses can be circumferentially closed and formed on a locking side of the first fastening element. In particular, the extent of the locking recesses in a circumferential direction of the extension device can be smaller than half of the circumference of the extension device. An extension of the locking recesses in the circumferential direction, which is smaller than a quarter of the circumference of the extension device, can be provided.

In particular, the locking recesses can thus only form minor recesses on the first fastening element, in which the second fastening element is supported via the locking section of the setting element that engages in the locking recesses. The locking recesses can thus be attached without inappropriately impairing the stability of the extension device or of the first fastening element. Furthermore, the locking section can be closed by the circumferentially closed design of the locking Also prevent relative movement of the fastening elements in the circumferential direction or relative rotational movements by the locking section engaging in a respective locking recess resting and / or abutting against the lateral boundaries of the locking recess. For example, the locking recesses can have an extension of about 1 mm in the circumferential direction with a diameter of the first fastening element of about 3 mm and an extension in the direction of extension of about 0.5 mm with an extension of the first fastening element of less than 40 mm, in particular of about 37 mm. 5 mm.

A small extension of the locking recesses in the circumferential direction can be seen in particular in the case of extension devices for extending relatively small tubular bones, for example finger and / or toe bones. Due to the relatively low loads that occur, for example in comparison to an extension device to extend a large leg bone, which has to carry the weight of the patient standing during a mobilization, a sufficient bloom can already be achieved by the juxtaposition of a small blocking surface on a stop surface Cracking effect for fixing the distance between the fastening elements can be achieved, so that the locking recesses can be made small and thus not impairing the stability of the first fastening element.

In some embodiments it can be provided that the locking recesses are arranged one after the other in a row along the direction of extent. In particular, just one row of locking recesses can be provided.

By pulling on the first fastening element and / or the second fastening element, the locking portion can be gradually brought into engagement with the locking recesses along the row by the distance between determine the fastening elements step by step. The locking section can thus - comparable to the principle of a stepladder - be guided along the row of locking recesses in order to support the second fastening element at a delimitation of the respective locking recess into which the locking section engages. The limitation of the locking recess can act in accordance with a rung of the stepladder on which a foot is supported.

In particular, the distance between the locking recesses can always be the same, so that the distance between the fastening elements can be adapted with each pulling by a predetermined and always the same adjustment path. As an alternative to this, it is also possible for the locking recesses to be arranged at a changing distance from one another in order, for example, to predetermine a certain course for an adjustment path by which the distance between the fastening elements increases as a result of the pulling.

Since, in particular, only a single or precisely one row of locking recesses can be provided, the first fastening element can be designed asymmetrically in this regard and only have locking recesses on one locking side. The adjusting element can also be designed asymmetrically and only have a blocking section oriented in the direction of the blocking side on one side, which can point away from the adjusting element, for example, in this direction transversely to the direction of extension. In turn, any loss of stability of the first fastening element due to the locking recesses can thereby be minimized, with a stable blocking effect or stable fixing of the distance between the fastening elements being able to be ensured, particularly when lengthening small bones. As an alternative to this, several rows of locking recesses can also be provided, the adjusting element in particular having a corresponding number of locking sections which gradually engage in the locking recesses in a respective one of the rows of locking recesses. For example, the locking sections and the rows of locking recesses can be arranged along a circumferential direction of the extension device. In principle, it is also possible to provide several rows of locking recesses, but only one locking section which engages in only one of the rows.

In some embodiments, the locking recesses can be designed as window-like openings on the first fastening element. These fensterar term openings can be arranged one after the other along a row in the direction of extension, wherein the locking portion can be moved by pulling on the first fastening element and / or the second fastening element along such a row to increase the distance between the fastening elements. The second fastening element can be supported via the adjustment element and its locking section on the abutment surfaces already mentioned, which can thus act similarly to ladder rungs of a stepladder arranged along a row.

In some embodiments it can be provided that the locking section is prestressed in the direction of the locking recesses transversely to the direction of extension. In particular, the locking section and / or the setting element can be elastically deflected, the locking section protruding or engaging in a basic state in one of the locking recesses and being able to be pushed out of the respective locking recess by pulling on the first fastening element and / or the second fastening element. As a result of the pulling on the first and / or the second fastening element, the locking portion can be guided out of the locking recess transversely to the direction of extension and thus are elastically deflected from the basic state, so that the locking section can automatically engage against this deflection or bias in the subsequent locking recess when it reaches the subsequent locking recess in order to re-establish the distance between the fastening elements. In particular, the setting element can be designed as a spring and / or an elastically deflectable rod that is fixedly connected to the second fastening element at one end. For example, the locking section can protrude at an end of such a rod-like adjusting element opposite the second fastening element, transversely to the direction of extension of the extension device, in order to engage in a respective one of the locking devices. A rod-like setting element can be curved transversely to the direction of extension in the direction of the locking recess to generate a preload with one end at which the locking section is arranged, while a straight design along the direction of extension is also possible with the locking section protruding transversely to the direction of extension.

The locking section and / or the setting element can be designed to be elastically resilient. In particular, the setting element can be made from spring wire and / or from spring steel. In principle, such a spring wire can also be referred to as a spring steel wire. The manufacture of the setting element from such a material enables an elastic design with extremely cost-effective manufacture. Through an elastically resilient training it can be achieved that the locking section deflected during a transfer from a respective locking recess into a subsequent locking recess comes into engagement with the subsequent locking recess by itself when the subsequent locking recess is reached by the spring back to the stand of the two block elements to each other.

Furthermore, it can be provided that the locking section is elastically deformable. Such elastic deformability can also enable the To bring locking portion by pulling on the first fastener and / or the second fastener out of engagement with the respective locking recess, the locking portion when reaching the subsequent locking recess by returning to the original shape automatically in a handle can get to the locking recess.

In some embodiments, the locking section can have a sliding surface which is oriented at an incline to the direction of extension. In particular, the sliding surface can also be aligned inclined to the abovementioned stop surfaces of the locking recesses. The sliding surface can in particular be oriented in such a way that the extension of the locking section decreases transversely to the extension direction of the extension device in the direction of the second fastening element.

The sliding surface can be designed to slide off during a pulling on the first fastening element and / or the second fastening element on a delimitation of the respective locking recess oriented transversely to the direction of extension. The inclined sliding surface can allow a deflection of the pulling movement taking place along the extension direction in order to force the locking section out of the respective locking recess during the pulling and the resulting movement in the extension direction transversely to the extension direction. The locking section can thereby be guided beyond the limitation and slide along a separating section between the respective and a subsequent locking recess in order to engage with the same when the subsequent locking recess is reached. The sliding surface can thus act as a control surface in order to pull both a movement component running along the direction of extension to increase the distance between the fastening elements and a movement component running transversely to the direction of extension for pushing the locking section out of the respective locking section. mung to achieve. In particular, the sliding surface of the locking section can slide on an edge of the delimitation.

It can consequently be provided in some embodiments that the locking portion can be forced out of the locking recess by pulling on the first fastening portion and / or on the second fastening portion over the sliding surface, in particular against a preload directed in the direction of the locking recess. In particular, the sliding surface can for this purpose be oriented at an acute angle to the direction of extent, in particular in an angular range between 30 ° and 60 °, wherein the angle can be 45 °, for example.

As an alternative to a design of the locking section with an inclined sliding surface, it is also possible that the said delimitation of the locking recess, which in particular can be arranged opposite to the mentioned stop surface with respect to the direction of extension, is directed inclined to the direction of extension, so that a block-shaped locking section, for example, is directed through From slide at the boundary out of the locking recess can be pushed. Furthermore, it is possible for both the delimitation and the blocking section to have a respective inclined sliding surface, the sliding surfaces in particular being able to have a corresponding inclination.

In some embodiments, the adjustment element can be arranged at least partially within the first fastening element. The first fastening element can have a bore and in this respect form a channel running along the direction of extent which can be closed on one side or open on both sides. The adjustment element can be designed as a rod extending from the second fastening element along the direction of extent, which protrudes into the channel formed by the first fastening element and from which the locking section protrudes, to engage in locking recesses formed on the side of a duct wall. The setting element can be moved together with the second fastening element when pulling relative to the first fastening element, so that the setting element can be gradually pulled out of the first fastening element when the distance between the fastening elements increases. Furthermore, the setting element can be designed in one piece with the second fastening element or can be connected to the second fastening element as a component manufactured separately from the second fastening element.

As an alternative to an arrangement of the setting element within the first fastening element, it is also possible for the setting element to encompass the first fastening element, for example, like a sleeve and the first fastening element to be partially arranged within the setting element, with an inwardly projecting transverse to the direction of extension of the setting element Barring section can engage in locking recesses formed on an outer wall of the first fastening element. Again, the locking section and / or the setting element can be elastically deformable and / or deflectable, for example, in order to enable the locking section to be transferred from a locking recess into a subsequent locking recess. The locking recesses can be designed, for example, like a window or a groove on the outside of the first fastening element.

In some embodiments, the setting element can be connected to the second fastening element in a form-fitting and / or force-fitting manner. In particular, the setting element and the second fastening element can be caulked and / or pressed together. The second fastening element and the adjusting element can thus be manufactured in a simple manner as separate components and then fixed to one another without the need for any further connecting elements. The first fastening element and / or the second fastening element can be screwed into the respective bone parts in some embodiments. In particular, the first fastening element and the second fastening element can have respective external threads for screwing into the bone parts. The extension device can thereby be introduced directly into the respective bone parts without the fastening elements having to be fastened by screws guided obliquely through the bone. In particular, this can facilitate the onset of the extension device, especially with relatively small bones, and accelerate it. Furthermore, by screwing in the fastening elements directly and dispensing with separate screws, an intervention that is as minimally invasive as possible can be achieved. For example, an external thread of the first fastening element can have a diameter of approximately 3.5 mm and an external thread of the second fastening element has a diameter of approximately 4.5 mm. The diameter of the fastening elements, apart from the external threads, can be about 3 mm.

In some embodiments, the first fastening element and the second fastening element can be coupled to one another in a rotationally fixed manner with respect to rotations about the direction of extension. In particular, the first fastening element and the second fastening element can be coupled to one another in a rotationally fixed manner at a minimal distance from one another. For example, when the extension device is being inserted into a bone in the course of an operation, the fastening elements can lie against one another and be coupled to one another in a rotationally fixed manner in order to be able to be screwed into the bone together and at the same time. The extension device can in particular be screwed through a joint surface of a bone, so that the extension device, for example with the first fastening element, through the second bone part as far into the first bone part can be screwed in that the second fastening element is also connected to the second bone part and the gap between the two bone parts is bridged by the extension device. Starting from this sem minimum distance at which there is a rotationally fixed coupling of the fastening elements and the extension device can be inserted into the bone during the operation, the distance between the fastening elements can then be increased, with a first increase after the screw and possibly already can be done during the operation. With a minimal distance between the fastening elements, the extension device can in particular have an extent in the direction of extent of at most 50 mm, in particular an extent of approximately - within the framework of manufacturing tolerances - 50 mm. The first fastening element can, for example, have an extension of less than 40 mm, in particular approximately 37.5 mm, and the second fastening element an extension of less than 15 mm, in particular approximately 12.5 mm.

It can be provided that the first fastening element and the second fastening element interlock in a form-fitting manner at the respective coupling end faces at a minimal distance from the rotationally fixed coupling. For example, a coupling recess extending transversely to the extension direction of the extension device can be formed on one coupling face, in which a coupling elevation formed on the other coupling face engages. Through such a form-fitting engagement, the two fastening elements can be screwed together into the bone to be lengthened. The coupling end faces can in particular be formed by respective facing end faces of the fastening elements.

In some embodiments, on an end face of the extension device, in particular an end face of the first fastening element and / or the second fastening element, a tool engagement section for a work be formed by means of which the extension device can be connected to the first bone part and the second bone part. In particular, the end face in question can be opposed to one of the coupling end faces already mentioned. Such a tool attack can make it possible to screw the extension device as a whole with a rotationally fixed coupling of the two fasteners into the bone by means of a tool in order to connect the fasteners to the respective bone parts. This can be done in a single process or work step, so that the attachment of the extension device can be carried out extremely quickly and easily.

The tool engagement section can be designed as a screw head with a screw head drive, wherein the extension device can be screwed into the first bone part and the second bone part by means of a screwdriver engaging the screw head drive. In particular, a cross-shaped and / or slot-shaped depression can be formed on the end face of the extension device, into which a corresponding screwdriver can engage. The depression can, for example, have an extension in the extension direction of approximately 1 mm and a width transverse to the extension direction of approximately 0.85 mm.

In some embodiments, the extension device can be designed to be connected to the first bone part and the second bone part through an articular surface of a finger and / or toe bone. In particular, the extension device can be designed to be screwed through an articular surface of a finger and / or toe bone in order to connect to the first bone part and the second bone part. The extremely simple design of the extension device to be actuated by pulling enables miniaturization in order to enable such minimally invasive use even with small finger and / or toe bones. Correspondingly, by screwing in the extension Device through the articular surface, even when treating such small bones, a quick and easy insertion of the extension device he will be enough. It can also be provided that the extension device is designed to be removed again in the same way after the treatment through the joint surface.

The invention is explained in the following purely by way of example using a game Ausführungsbei with reference to the drawings. Show it:

Fig. 1 is a schematic longitudinal view of a renkbochen inserted into a small Röh lengthening device for lengthening the bone and

2A to 2C show a schematic longitudinal view of the extension device, a schematic longitudinal sectional view of the extension device and a detailed view of a portion of the extension device in longitudinal section to illustrate the fixing of the extension device at a set length.

The extension device 1 shown in Fig. 1 extends along a He stretching direction E and has a first fastening element 4 with a first external thread 3 which is screwed into a first piece of bone 2 of a small tubular bone 24, for example a finger or toe bone. A second fastening element 7, which has a second external thread 8 and is screwed into a second bone part 9, is connected to the first fastening element 4 via an adjusting element 12 (cf. FIGS. 2B and 2C) that the extension device 1 bridges a gap between the bone parts 2 and 9 and aligns them with one another.

Fig. 1 shows the extension device 1 in an operating position in which the first fastening element 4 and the second fastening element 7 with respective coupling end faces 20 and 21 interlock positively in order to achieve a rotationally fixed coupling of the two fastening elements 4 and 7. For this purpose, a coupling recess 18 is formed on the coupling face 20 of the first fastening element 4, which extends in the form of a slot transversely to the direction of extent E of the extension device 1 and in which a coupling bump 19 formed on the coupling face 21 of the second fastening element 7 engages in a form-fitting manner. The coupling recess 18 and the coupling elevation 19 form a coupling 6, so that the first fastening element 4 and the second fastening element 7 in this operational position are connected to one another in a rotationally fixed manner with regard to rotations about the extension direction E.

The second fastening element 7 has on one end face 22 opposite the coupling end face 21 with respect to the direction of extent E, a work engaging section 10 which is designed as a screw head and has a screw head drive 16. This screw head drive 16 can be ausgebil det for example as a slot or cross-shaped recess in the end face 22 to screw the extension device 1 or the two fasteners te 4 and 7 into the bone 24 by means of a screwdriver. The rotationally fixed coupling of the two fastening elements 4 and 7 enables both fastening elements 4 and 7 to be screwed into the bone 24 together in a single work step. In particular, the extension device 1 can be screwed into the bone 24 through an articulation surface 29 of the second bone part 9 in order to traverse the second bone part 9 and fasten it with the first fastening element 4 in the first bone part 2 will. The second fastening element 7 is screwed into the second bone part 9 at the same time, so that finally the gap between the bone parts 2 and 9 is bridged by the extension device 1.

While the first fastening element 4 and the second fastening element 7 in the operating position of the extension device 1 shown in Fig. 1 lie with their coupling end faces 20 and 21 against each other and thus have a minima len distance from each other in order to achieve a rotationally fixed coupling and the extension device 1 in a single To be able to screw into the bone 24 working step, the extension device 1 is designed such that the distance between the two fastening elements 4 and 7 can be gradually increased by pulling on the first fastening element 4 and / or the second fastening element 7. As a result, an extension of the bone 24 can be achieved in that the two bone parts 2 and 9 are gradually removed from each other by increasing the distance between the fastening elements 4 and 7 and increasingly bone substance is formed between the bone parts 2 and 9, so that the bone 24 to the At the end of the healing process, it can ultimately grow together at a desired length. The pulling movement can be transmitted to the fastening elements 4 and 7 by pulling on the respective limbs or extremities connected to the bone parts 2 and 9.

In order to enable a gradual increase in the distance between the fasteners 4 and 7, but to prevent an unintentional reduction in this distance, the second fastening element 7 is connected to the first fastening element 4 via the adjustment element 12 already mentioned (see, in particular, FIG. 2B ). The setting element 12 is fixed in the second fastening element 7, for example by a compression 13, and extends like a rod along the direction of extent E into an axial bore 11 formed on the first fastening element 4. The bore 11 thus forms as it were a channel for the adjusting element 12, which is open in the direction of the second fastening element 7 and is closed or open on the opposite side by a tip 26 of the first fastening element 4.

On a blocking side 23 of the first fastening element 4, a plurality of blocking recesses 5 arranged one after the other along the direction of extent E are formed, with a blocking section 25 arranged on an end 27 of the setting element 12 opposite the second fastening element 7, depending on the distance between the two fastening elements 4 and 7 engages in a respective one of the locking recesses 5 (see. Fig. 2C). By engaging in the locking recess 5, the locking section 25 blocks a relative movement of the two fastening elements 4 and 7 towards one another, but enables the distance between the two fastening elements 4 and 7 to be increased by, in particular, manual pulling.

As can be seen in particular from the detailed view of FIG. 2C, the locking section 25 stands at the end 27 of the rod-like adjusting element 12 laterally or transversely to the direction of extension E and protrudes into one of the locking devices 5. In this case, the blocking section 25 has a blocking surface 15 which is oriented essentially perpendicularly to the direction of extension E and which rests against a stop surface 17 of the blocking recess 5. As a result of this contact of the blocking surface 15 on the stop surface 17, a relative movement of the fastening elements 4 and 7 directed towards one another is blocked in order to prevent an undesired reduction in the distance between the fastening elements 4 and 7 or a shortening of the extension device 1. The second fastening element 7 is thus supported to a certain extent on the first fastening element 4 via the locking section 25 of the setting element 12. However, in order to enable an increase in the distance between the fastening elements 4 and 7, the locking section 25 has a sliding surface 14 inclined at an angle α to the direction of extension E. The setting element 12 is elastic, in particular resilient, or deflectable, so that the sliding surface 14, by pulling on the first fastening element 4 or the second fastening element 7, slide against a boundary 28 of the locking recess 5 and the locking section 25 is forced out of the locking recess 5 can be. The sliding surface 14 thus acts as a control surface in order to derive a movement component directed transversely to the direction of extension E from a pulling movement directed along the direction of extension E and thereby to be able to force the locking section 25 out of the locking recess 5. For example, the setting element 12 can be made from spring wire for this purpose.

By sliding the sliding surface 14, the locking section 25 can be transferred out of the locking recess 5 along a separating section 30 formed by the first fastening element 4 into a subsequent locking recess 5a (see in particular Fig. 2C) in order to reduce the distance between the fastening elements 4 and 7 to enlarge. Due to the deflectability of the setting element 12 or a resulting bias of the locking section 25 in the direction of the locking recesses 5, the locking section 25 can automatically engage in this when reaching the subsequent locking recess 5a to the extension device 1 at this distance between the two fastening elements 4 and 7 to be fixed to each other. The tissue tension of the limb causes permanent pressure on the setting element 12, so that the locking surface 15 is always pressed against the stop surface 17 of the respective locking recess 5 in order to prevent unwanted or unconscious lengthening of the extension device 1. The locking section 25 can thus be transferred in a controlled and reliable manner by pulling a respective locking recess 5 into the subsequent locking recess 5a, so that the distance between the fastening elements 4 and 7 can be increased step by step by a respective adjustment path S, which is derived from the distance of the Locking recesses 5 results in relation to one another. In particular, the treatment of a patient or the speed of the bone lengthening can be precisely coordinated and checked by instructing a patient to perform a certain number of steps per unit of time. The simple actuation by manual pulling enables comfortable handling and the unrestricted mobilization leads to a quick healing process.

As in particular Fig. 2B shows, the locking recesses 25 are formed successively along a row in the direction of extent E on the locking side 23 and form an asymmetry of the first fastening element 4, which does not have a corresponding row of locking recesses 5 on a side opposite the locking side 23 . The locking recesses 25 represent window-like openings in the locking side 23 and form only slight recesses, so that the stability of the first fastening element 4 is not impaired by the locking recesses 5. The extremely simple mechanism for lengthening the extension device 1, in particular with only three components, enables, in addition to cost-effective production, in particular a miniaturization of the extension device 1, so that the extension device 1 can be used to extend small bones 24, for example finger and / or toe bones, suitable is.

The exemplary embodiment of the lengthening device 1 shown in the figures thus enables a reliable, step-by-step lengthening of a bone 24 with the aid of an extremely simple mechanism and the smallest possible number of components. This makes the extension device 1 particularly suitable for miniaturized training to enable minimally invasive use to lengthen small long bones and hereby replace external fixation devices that severely limit the patient's ability to move in everyday life and represent a significant risk of infection due to the possible entry of pathogens through the mechanically broken skin . In addition, due to the simple mechanics, highly corrosion-resistant materials can be used to manufacture the fastening elements 4 and 7 and the setting element 12, which can be made from spring wire, for example, so that the extension device 1 can in principle remain in the bone 24 even after the treatment . The non-rotatable coupling of the fastening elements 4 and 7 also enables extremely quick insertion of the extension device 1 into the bone 24 by simultaneously screwing in the fastening elements 4 and 7 by means of a tool that engages the tool, for example a screwdriver.

D 0 CD _C 0

List of reference symbols

1 extension device

2 first bone part

3 first external thread

4 first fastening element

5 locking recess

5a subsequent locking recess coupling second fastening element second external thread second bone part

10 tool attack section

11 axial bore

12 adjustment element

13 grouting

14 sliding surface

15 restricted area

16 screw head drive

17 stop surface

18 Coupling recess

19 Linkage survey

20 coupling face

21 Coupling face

22 front side

23 Blocking Page

24 bones

25 locking section

26 tip

27 End of adjustment element

28 limitation

29 articular surface

30 separation section

E direction of extent

S travel a angle of the sliding surface to the direction of extent

Claims

Expectations

1. Extension device (1) for minimally invasive lengthening of small tubular bones (24), in particular metatarsal, metacarpal, finger and / or toe bones, which extends along an extension direction (E) and which has a first fastening element (4) for fastening a first bone part (2) and a second fastening element (7) for fastening to a second bone part (9) in order to bridge a bone gap between the first bone part (2) and the second bone part (9), the second fastening element ( 7) is connected to the first fastening element (4) via an adjusting element (12) and a distance between the two fastening elements (4, 7) along the extension direction (E) is gradually increased by, in particular manually, pulling on the first fastening element (4 ) and / or the second fastening element (7) can be enlarged, the adjusting element (12) having a Sperrab section (25) which is designed to i st to block a relative movement of the first fastening element (4) and the second fastening element (7) directed towards one another and to enable an increase in the distance between the two fastening elements (4, 7) by pulling.

2. Extension device (1) according to claim 1, wherein the first fastening element (4) has a plurality of locking recesses (5) arranged one after the other in the direction of extension (E), where the locking section (25) engages in a respective one of the locking recesses (5).

3. Extension device (1) according to claim 2, wherein the locking portion (25) by pulling on the first fastening element (4) and / or the second fastening element (7) from the respective locking recess (5) can be transferred into a subsequent locking recess (5a).

4. Extension device (1) according to claim 2 or 3, wherein the locking recesses (5) have a respective stop surface (17) on which the engaging locking portion (25) rests with a Sperrflä surface (15), the stop surfaces (17) are oriented essentially perpendicular to the direction of extension (E), in particular where the blocking surface (15) is oriented essentially perpendicular to the direction of extension (E).

5. Extension device (1) according to one of claims 2 to 4, wherein the locking recesses (5) are circumferentially closed and formed on a locking side (23) of the first fastening element (4), in particular wherein the extension of the locking recesses (5) in a To the circumferential direction of the first fastening element (4) is less than half the circumference of the first fastening element (4) or less than a quarter of the circumference of the first fastening element (4).

6. Extension device (1) according to one of claims 2 to 5, wherein the locking recesses (5) in a row along the extension direction (E) are arranged one after the other, in particular wherein only one row of locking recesses (5) is provided.

7. Extension device (1) according to one of claims 2 to 6, wherein the locking recesses (5) are designed as window-like openings on the first fastening element (4).

8. Extension device (1) according to one of claims 2 to 7, wherein the locking portion (25) is biased in the direction of the locking recesses (5) transversely to the direction of extension (E).

9. Extension device (1) according to one of claims 2 to 8, wherein the locking portion (25) and / or the adjusting element (12) is designed to be elastically resilient, in particular wherein the adjusting element (12) is made of spring wire and / or spring steel.

10. Extension device (1) according to one of claims 2 to 9, wherein the locking portion (25) has a sliding surface (14) which is oriented inclined to the direction of extension (E).

11th Extension device (1) according to claim 10, wherein the sliding surface (14) is designed to, while pulling on the first fastening element (4) and / or the second fastening element (7) on a boundary ( 28) slide off the respective locking recess (5).

12. Extension device (1) according to claim 10 or 11, wherein the locking portion (25) by pulling on the first fastening element (4) and / or on the second fastening element (7) over the sliding surface (14) from the locking recess (5) can be pushed, in particular against a bias voltage directed in the direction of the locking recess (5).

13. Extension device (1) according to one of the preceding claims, wherein the adjusting element (12) is arranged at least partially within the first fastening element (4).

14. Extension device (1) according to one of the preceding claims, wherein the adjusting element (12) with the second fastening element (7) is positively and / or non-positively connected, in particular wherein the one adjusting element (12) and the second fastening element (7) with each other are caulked and / or pressed.

15. Extension device (1) according to one of the preceding claims, wherein the first fastening element (4) and / or the second fastening element (7) can be screwed into the respective bone parts (2, 9), in particular wherein the first fastening element (4) and the second loading fastening element (7) have respective external threads (3, 8) for screwing into the bone parts (2,9).

16. Extension device (1) according to one of the preceding claims, wherein the first fastening element (4) and the second fastening element (7) can be coupled to one another in a rotationally fixed manner with respect to rotations about the direction of extension (E), in particular with a minimal distance between the first fastening element ( 4) and the second fastening element (7).

17. Extension device (1) according to one of the preceding claims, wherein the first fastening element (4) and the second fastening element (7) interlock positively at a minimal distance from the rotationally fixed coupling at respective coupling end faces (20, 21).

18. Extension device (1) according to one of the preceding claims, wherein on one end face (22) of the extension device (1), in particular one end face (22) of the first fastening element (4) and / or the second fastening element (7), a tool engagement section (10) is designed for a tool by means of which the extension device device (1) can be connected to the first bone part (2) and the second bone part (9).

19. Extension device (1) according to claim 18, wherein the tool engagement portion (10) as a screw head with a

Screw head drive (16) is formed, wherein the extension device (1) can be screwed into the first bone part (2) and the second bone part (9) by means of a screwdriver engaging in the screw head drive (16).

20. Extension device (1) according to one of the preceding claims, wherein the extension device (1) is designed to pass through a joint surface (29) of a finger and / or toe bone (24) with the first bone part (2) and the second bone part (9) to be connected, in particular to be screwed through an articular surface (29) of a finger and / or toe bone (24) to connect to the first bone part (2) and the second bone part (9).