DE102019118748A1 - Endoprosthesis for a finger joint - Google Patents

Abstract

The invention relates to an endoprosthesis for a finger joint, in particular for a middle finger joint or a metacarpophalangeal joint, having a proximal component which can be connected to a first finger bone and which has a substantially hemispherical bearing with a cut surface and a bearing surface and a substantially perpendicular protruding from the cut surface and with This shaft which is connected in an angularly stable manner, and a distal component which can be connected to a second finger bone and which has a counter surface that interacts with the bearing surface of the proximal component, the shaft of the proximal component in the implanted state at an angle of at least 30 ° to the longitudinal axis of the first finger bone is inclined.

Description

The invention relates to an endoprosthesis for a finger joint according to the preamble of the first patent claim and is used in particular for the middle and metacarpal joints of the fingers.

In the case of joint damage to the finger joints, often caused by arthritis, osteoarthritis or injuries, finger joint endoprostheses are increasingly being used. These should primarily ensure mobility and stability and take over the functions of the natural joint. A wide variety of variants are conceivable, which usually essentially have anchors for the two adjacent bones, as well as a joint hinge.

As known finger joint endoprostheses, for example, silicone endoprostheses are used which consist of a rod-shaped body with a central, palmar transverse groove, and which are designed essentially in the manner of an elastic hinge. Both ends of the rod are anchored proximally and distally in the medullary canal of the base phalanx and the middle phalanx. However, silicone endoprostheses are often not resilient and usually after a short period of time (3 to 9 months) the prosthesis breaks and functional failure of varying degrees. During revision surgery, there is almost always inflammation of the surrounding tissue due to silicon abrasion. In addition, the bending of the bone elements relative to one another is only possible to a limited extent.

From the pamphlet EP 1 438 937 B1 is a finger prosthesis for adaptation to a tubular bone stump of a finger, having a stem-shaped implant that can be implanted in the tubular bone and fixed there, with which an extracorporeal replacement body can be coupled. The stem-shaped implant is hollow and a through-hole in the head, designed as a conical clamping sleeve in its approach, up to the hollow stem and a threaded hole in the lower end of the stem is provided. Furthermore, a threaded sleeve is provided, which has a thread at its foot end, which can be screwed to the threaded hole in the lower end of the stem, which length corresponds to at least the length of the surface area allowing the ingrowth of bone trabeculae, and an internally threaded hole in the head end and an adapter piece is provided which can be brought into the conical clamping connection with a head widening outside the stem-shaped implant, in which a threaded screw can be set through its interior, which can be screwed to the internally threaded bore in the head end of the threaded sleeve. This finger prosthesis has a complex and large structure.

A substantially hinge-like finger joint prosthesis is made DE 20 2014 010 623 known. This has at least one anchoring strip which is accommodated in the joint body in a longitudinally displaceable, self-adjustable manner or fixed in it in a longitudinally displaceable manner. The anchoring strip can thus move within the joint body to a certain extent to compensate for any stresses that may arise in the joint system, specifically over a range of 0 to 3 mm. This is intended to achieve an anatomically needs-based and self-adjusting length compensation on a finger joint prosthesis. This hinge-like finger joint prosthesis is also disadvantageously large in size and is not easy to implant. The finger joint prosthesis is not arranged axially in the intramedullary canal as usual, but attached to the side of the bone, with a bore from the radial side at the center of rotation of the proximal and distal phalanx, and two radial slots extending in the longitudinal center direction of the phalanges from the milled bore must be attached. This arrangement, as well as the fastening by a total of 4 screws, mean an disadvantageously high implantation effort.

Furthermore, finger joint endoprostheses made of ceramic or pyrocarbon are known which are not coupled with a proximal and a distal component.

With the pyrocarbon model, osteointegration is not achieved: the progressive osteolysis causes the prosthesis to sink in, which results in prosthesis failure and painful impairment of function.

For example in EP 0639360 A1 a finger joint prosthesis - in particular a metacarpophalangeal or a proximal interphalangeal prosthesis - comprising a two-part proximal implant that has a head element with a convex joint surface, and a distal also two-part element with a concave surface that slides in contact with the convex joint surface. The proximal element is anchored axially in a longitudinal bore in the medullary canal. Each implant comprises a shield, the shape and dimensions of which correspond at least substantially to those of the original cartilage. The prosthesis is made of metal, ceramic or plastic.

It is also common to use finger joint endoprostheses made of metal with a polyethylene pairing, which are manufactured in an uncoupled or coupled design.

The metal finger joint endoprostheses are oversized (in some variants to achieve a more stable anchoring of the prosthesis components) - this leads to trauma to the capsule-ligament apparatus with adhesions and a corresponding restriction in function.

A joint part prosthesis for a finger joint made of a high-strength metal is shown in EP 0 455 929 A1 described. In this case, the respective bearing body is designed as a thin-walled, but high-strength metallic shell element, with which essentially only the bearing surface needs to be replaced, for which the removal of the articular cartilage alone should generally be sufficient with the specified thickness of at most about 1 mm. At the same time, in this solution, the shaft attached to the back of this shell and anchored in the medullary canal of the bone, in conjunction with the roughness of the rear shell surface, should ensure a firm and permanent fit and secure adhesion of the prosthesis part to the anchored bone cement. The two bearing bodies have an essentially axial extent to one another.

The disadvantages of the conventional finger joint endoprostheses currently in use are that, for operational reasons, they usually have to be introduced from the dorsal side. The extensor aponeurosis is exposed and partially disinserted. This often leads to adhesions of these sliding layers and, as a result, to a restriction of mobility in the operated joint.

Due to the axial alignment of the prosthetic shafts of most of the aforementioned finger prostheses, the force vector in the functional position (flexion) in the middle or base joint is not taken into account. This promotes failure of the prosthesis with loosening, inflammation and scarring.

A finger prosthesis joint for implantation between two finger bone sections, which has a shaft for insertion into a passage formed in a first of the finger bone sections and a partial ball bearing provided at one end of the shaft to enable pivoting of a second finger bone, is from EP 0 338 715 A1 known. The bearing is arranged so that it is seated on an inclined end surface of the first finger portion so that it is not inclined perpendicular to the general axis of the passage. The partial ball bearing has a substantially flat seat surface that is engageable with the inclined end surface of the first finger portion and the shaft does not protrude perpendicularly from the flat seat surface to be received by the passage. In order to secure the prosthesis against twisting in the passage, the outer surface of the shaft is either provided with serrations or ribs, or the shaft has a square or a cross-section provided with flats. The disadvantage of this solution is the increased production cost of the prosthesis, since the shaft has to be angled on the one hand and be provided with a specially designed outer surface on the other. With this form of prosthesis, too, the shaft is aligned axially in the intramedullary canal. With this model, the expected disadvantages correspond to those of the usual metal implants.

The object of the invention is to develop an endoprosthesis for a finger joint which is small in size, does not restrict the mobility of the joint or restricts it only insignificantly, withstands higher loads and is easy to implant.

This object is achieved with the characterizing features of the first claim.

Advantageous configurations result from the subclaims.

According to the invention, an endoprosthesis for a finger joint, in particular for a middle finger joint or a metacarpophalangeal joint, has a proximal component which can be connected to a first finger bone and which has a substantially hemispherical bearing with a cut surface and a bearing surface and a substantially perpendicular protruding from and with the cut surface Has an angularly stable connected shaft, and a distal component connectable to a second finger bone, which has a counter surface cooperating with the bearing surface of the proximal component, wherein according to the invention the shaft of the proximal component in the implanted state is inclined at an angle of at least 30 ° to the longitudinal axis of the first finger bone is.

The shaft is thereby advantageously aligned in the axis of the introduction of force in the middle functional position in the respective finger joint. The angle at which the shaft of the proximal component is inclined to the longitudinal axis of the first finger bone in the implanted state is particularly preferably 35 °. Due to the perpendicular alignment of the shaft to the cut surface of the proximal component, the cut surface of the proximal component is thus inclined at an angle of approximately 55 ° to the longitudinal axis of the first finger bone. Due to the more physiological alignment of the prosthesis axes in accordance with the force vectors, faster osteointegration can be expected, which leads to a faster achievement of full function and resilience of the finger joint to be replaced.

The substantially hemispherical bearing can also be a part-spherical bearing. The bearing of the proximal component is modeled on the anatomical head shape of the corresponding bone. It is also conceivable that the essentially hemispherical or part-spherical bearing has a sagittally oriented guide channel, the counterpart of which is designed accordingly in the distal component.

In a preferred embodiment, the shaft of the proximal component is designed as a pin.

In a further preferred embodiment, the shaft of the proximal component has a thread.

The proximal end of the shaft is preferably anchored transcortically in order to prevent the proximal component from tilting. In the context of the invention, transcortical is to be understood as “through the bone cortex” or “in the periosteum”.

The shaft is preferably coated with a biocompatible coating. This enables faster osteointegration to be guaranteed. Hydroxyapatite is particularly advantageous, but other biocompatible coatings known to the person skilled in the art can also be selected.

The cut surface of the proximal component advantageously has at least one first anchoring element for preventing the proximal component from rotating. The first anchoring element is preferably designed in the form of one or more spikes. The spikes interact with the bone material of the adjacent bone to the effect that the proximal component is secured against rotation. The first anchoring element can also have a biocompatible coating for better osteointegration.

The distal component preferably has a shaft for anchoring in the second finger bone. This shaft can also be designed as a pin or as a thread and have a biocompatible coating.

The distal component preferably has at least one second anchoring element on its surface facing the second finger bone to prevent the distal component from rotating. This is also preferably designed in the form of one or more spikes which interact with the bone material of the adjacent bone to the effect that the distal component is secured against rotation. The second anchoring element can also have a biocompatible coating for better osteointegration.

The first finger bone with which the proximal component is connected is preferably a phalanx or a metacarpal bone. Accordingly, the second finger bone to which the distal component is connected is preferably a middle phalanx or a phalanx.

When the endoprosthesis according to the invention is used, significantly fewer portions of the bone need to be resected proximally. As a result, the loss of tissue is lower than is the case with conventional finger joint endoprostheses.

Compared to conventional prostheses, the prosthesis head can be made smaller and is therefore less tissue-traumatic. This protects the capsule-ligament apparatus (especially the collateral ligaments) and the extensor aponeurosis.

The only palmar access protects the extensor aponeurosis and this results in fewer adhesions of the extensor aponeurosis, which leads to better mobility in the finger joint to be replaced. Advantageously, the prosthesis head is easier to implant (since there is only one resection level), which means that the surgical procedure has a lower risk of incorrect placement than with prostheses with multiple resection levels. Furthermore, the bone portions to be resected are much smaller (more economical) than is the case with conventional prostheses.

The faster osteointegration to be expected due to the more physiological alignment of the prosthesis axes in accordance with the force vectors advantageously leads to full function and resilience being achieved more quickly.

The invention is explained in more detail below with reference to exemplary embodiments and associated drawings, without being restricted to these.

• 1 Eine shematische Ansicht der Knochen eines Fingers in gestreckter Position mit implantierter erfindungsgemäßer Endoprothese zwischen Fingergrundglied und Fingermittelglied;
• 2 eine shematische Draufsicht auf die Knochenstruktur einer Hand mit mit implantierter erfindungsgemäßer Endoprothese zwischen Fingergrundglied und Fingermittelglied des Zeigefingers und eine vergrößerte Darstellung im Bereich der Endoprothese;
• 3 eine shematische Ansicht der Knochen eines Fingers mit implantierter erfindungsgemäßer Endoprothese zwischen Fingergrundglied und Fingermittelglied in Ruhestellung des Fingers;
• 4 eine shematische Ansicht der Knochen eines Fingers mit implantierter erfindungsgemäßer Endoprothese zwischen Fingergrundglied und Fingermittelglied bei gebeugter Stellung des Fingers;
• 5 eine erfindungsgemäße Endoprothese für die Implantation zwischen Mittelhandknochen und Grundglied eines Fingers;
• 6 eine erfindungsgemäße Endoprothese für die Implantation zwischen Grundglied und Mittelglied eines Fingers;

Show:

• 1 A schematic view of the bones of a finger in an extended position with an implanted endoprosthesis according to the invention between the base phalanx and the middle phalanx;
• 2 a schematic top view of the bone structure of a hand with an implanted endoprosthesis according to the invention between the base phalanx and the middle phalanx of the index finger and an enlarged view in the area of the endoprosthesis;
• 3 a schematic view of the bones of a finger with an implanted endoprosthesis according to the invention between the base phalanx and the middle phalanx in the rest position of the finger;
• 4th a schematic view of the bones of a finger with an implanted endoprosthesis according to the invention between the base phalanx and the middle phalanx with the finger in a flexed position;
• 5 an endoprosthesis according to the invention for implantation between the metacarpal bone and the base of a finger;
• 6th an endoprosthesis according to the invention for implantation between the base member and middle member of a finger;

In 1 is a schematic view of the bones of a finger in the extended position with an implanted endoprosthesis according to the invention between the phalanx F1 and phalanx F2 shown. The endoprosthesis according to the invention has a proximal component 1 , which with the phalanx F1 connected, and a distal component 3 , which with the middle phalanx F2 connected to. The proximal component 1 has a substantially hemispherical bearing 1.1 with a cut surface 1.2 and a storage area 1.3 on. With the cut surface 1.2 is a shaft that protrudes substantially perpendicularly from it 2 connected at a stable angle. The proximal end of the shaft 2 is anchored transcortically to prevent tilting of the prosthetic head. A first anchoring element in the form of at least one spike 1.4 ensures that the proximal component is secured against twisting 1 .

The first anchoring element - here a first spike 1.4 - is essentially in the direction of the shaft 2 aligned and preferably designed in the form of a pointed cone.

In the storage area 1.3 there is a guide trough indicated by dashed lines 1.3 ' , which has an unspecified width and its course essentially the course of the bearing surface 1.3 is adapted. The guide trough 1.3 ' runs in the direction of curvature of the finger F2 .

The distal component 3 consists of a disc-shaped part, which is modeled on the anatomical shape of the base of the corresponding bone (middle pod or base pod). It is anchored in the bone axially via a short shaft 4th or spikes - these are also coated accordingly for better osteointegration. The distal component 3 has one with the storage area 1.3 the proximal component 1 interacting counter surface 3.1 on.

The opposite surface 3.1 points in the direction of the guide channel 1.3 ' a bulge that is convex in section 3.1 ' on. This engages in the guide channel after the prosthesis has been inserted 1.3 ' (see dashed arrows) and is guided in this. The width of the bulge, not shown 3.1 ' and their curved course is the width and the course of the guide channel 1.3 ' customized.

The distal component 3 is made by a short shaft 4th in the middle of the finger F2 anchored. Both the shaft 2 the proximal component 1 , as well as the shaft 4th the distal component 3 and the first anchoring element 1.4 the proximal component 1 are advantageously coated with a biocompatible coating. The proximal component 1 is like this in the phalanx F1 implanted that angle α between the longitudinal axis L. of the phalanx F1 and the longitudinal axis of the shaft 2 the proximal component is about 35 °. Because the shaft 2 substantially perpendicular to the cut surface 1.2 of the camp 1.1 the proximal component 1 protrudes from the angle β between the cut surface 1.2 of the camp 1.1 the proximal component 1 and the longitudinal axis L. of the phalanx F1 about 55 °.

The proximal component 1 consists of a headboard 1.1 with only a short shaft 2 , this shaft 2 is not placed axially aligned in the intramedullary canal, as is usual, but in the axis of force introduction in the middle functional position in the middle or metacarpal joint (approx. 55 ° in each case) to the longitudinal axis L. runs dorsally. The shaft is advantageously 2 thus in the axis of the introduction of force in the middle functional position in the phalanx F1 (in the embodiment shown here) aligned, whereby faster osteointegration can be expected.

The prosthesis is implanted exclusively from the palmar using a standardized surgical approach. When resecting the head (for the proximal prosthesis component), a little more material has to be resected in order to create sufficient space for the distal component, which is nevertheless very narrow

2 shows a schematic plan view of the bone structure of a hand with an inventive endoprosthesis implanted between the phalanx F1 and phalanx F2 of the index finger and an enlarged view in the area of the endoprosthesis. The proximal component 1 the endoprosthesis is with the phalanx F1 and the distal component 3 with the middle phalanx F2 connected. The proximal component 1 is the anatomical head shape of the phalanx F1 and the distal component 3 the anatomical shape of the base of the Middle phalanx F2 modeled on. In this illustration, in particular from the enlarged view in the area of the endoprosthesis, it can be seen that the bulge 3.1 ' in the guide channel 1.3 ' intervenes and both are matched to one another in their unspecified width.

In 3 is a schematic view of the bones of a finger with an implanted endoprosthesis according to the invention between the phalanx F1 and phalanx F2 shown with the finger at rest. The proximal component 1 the endoprosthesis is by means of a shaft 2 and spikes 1.4 on the phalanx F1 anchored. The distal component 3 is by means of a shaft 4th on the middle of the finger F2 anchored. The shaft 2 the proximal component 1 and the shaft 4th the distal component 3 lie on one and the same axis when the finder is in the rest position A. . 4th shows a schematic view of the bones of a finger with an implanted endoprosthesis according to the invention between the phalanx F1 and phalanx F2 with the finger bent.

In 5 shows an endoprosthesis according to the invention for implantation between the metacarpal bone and the base of a finger, as shown in FIG 1 is used .. The proximal component 1 has a substantially hemispherical bearing 1.1 with a cut surface 1.2 and a storage area 1.3 on. With the cut surface 1.2 is a shaft that protrudes substantially perpendicularly from it 2 connected at a stable angle. A first anchoring element in the form of a spike 1.4 ensures that the proximal component is secured against twisting 1 . The distal component 3 consists of a disc-shaped part that is modeled on the anatomical shape of the base of the corresponding bone. The distal component 3 has one with the storage area 1.3 the proximal component 1 interacting counter surface 3.1 on.

In the in 5 The embodiment shown is the storage area 1.3 the proximal component 1 convex and the counter surface 3.1 the distal component 3 concave. The distal component 3 has one with the storage area 1.3 the proximal component 1 interacting counter surface 3.1 on which a convex bulge 3.1 ' in the form of an equivalent / matching counterpart to the sagittal guide trough 1.3 ' having. The endoprosthesis designed in this way is intended as a replacement for the metacarpal joint between the metacarpal bone and the phalanx. Anchoring the distal component 3 in the bone takes place axially via a short shaft 4th . Both the shaft 2 the proximal component 1 , as well as the shaft 4th the distal component 3 and the first anchoring element 1.4 the proximal component 1 are advantageously coated with a biocompatible coating.

6th shows an endoprosthesis according to the invention according to 5 , but in a 90 ° around the longitudinal axis A. rotated position, for the implantation between the base and middle phalanx of a finger. The proximal component 1 has a substantially hemispherical bearing 1.1 with a cut surface 1.2 and a storage area 1.3 on. The storage area 1.3 has a guide channel running in the sagittal plane on its surface 1.3 ' on. With the cut surface 1.2 is a shaft that protrudes substantially perpendicularly from it 2 connected at a stable angle. The distal component 3 consists of a disc-shaped part that is modeled on the anatomical shape of the base of the corresponding bone. It can also be seen here that the distal component 3 which has a convex bulge 3.1 ' in the form of an equivalent / matching counterpart to the sagittal guide trough 1.3 ' having. When the endoprosthesis is inserted, the bulge engages 3.1 ' in the guide channel 1.3 ' a.

The endoprosthesis designed in this way is intended to replace the proximal inerphalic joint between the base phalanx and the middle phalanx. Anchoring the distal component 3 in the bone takes place axially via a short shaft 4th . A second anchoring element in the form of two spikes 3.2 ensures that the distal component is secured against twisting 3 . Both the shaft 2 the proximal component 1 , as well as the shaft 4th the distal component 3 and the second anchoring element 3.2 the distal component 3 are advantageously coated with a biocompatible coating.

Furthermore, an embodiment is also conceivable which has both first anchoring elements in the form of one or more first spikes 1.4 on the proximal as well as second anchoring elements in the form of second spikes 3.2 on the distal component.

List of reference symbols

1

proximal component

1.1

warehouse

1.2

Cut surface

1.3

storage area

1.3 '

Guide trough

1.4

first anchoring element

2

Shaft of the proximal component

3

distal component

3.1

Counter surface

3.1 '

convex bulge

3.2

second anchoring element

4th

Shaft of the distal component

F1

first finger bone

F2

second finger bone

A.

axis

L.

Longitudinal axis

α

Angle between shaft and longitudinal axis

β

Angle between the cutting surface and the longitudinal axis

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 1438937 B1 [0004]
• DE 202014010623 [0005]
• EP 0639360 A1 [0008]
• EP 0455929 A1 [0011]
• EP 0338715 A1 [0014]

Claims (13)

Endoprosthesis for a finger joint, in particular for a middle finger joint or a metacarpal joint, having a proximal component (1) which can be connected to a first finger bone (F1) and which has a substantially hemispherical bearing (1.1) with a cut surface (1.2) and a bearing surface (1.3) and a shaft (2) protruding substantially perpendicularly from the cut surface (1.2) and connected to it in an angularly stable manner, and a distal component (3) which can be connected to a second finger bone (F2) and which is connected to the bearing surface (1.3) of the proximal component (1) having interacting counter surface (3.1), characterized in that the shaft (2) of the proximal component (1) in the implanted state is inclined at an angle (α) of at least 30 ° to the longitudinal axis (L) of the first finger bone (F1) is. Endoprosthesis Claim 1 , characterized in that the shaft (2) of the proximal component (1) is designed as a pin. Endoprosthesis Claim 1 , characterized in that the shaft (2) of the proximal component (1) has a thread. Endoprosthesis according to one of the Claims 1 to 3 , characterized in that the shaft (2) of the proximal component (1) is coated with a biocompatible coating. Endoprosthesis according to one of the Claims 1 to 4th , characterized in that the cut surface (1.2) of the proximal component (1) has at least one first anchoring element (1.4) to prevent the proximal component (1) from rotating. Endoprosthesis Claim 5 , characterized in that the first anchoring element (1.4) is designed in the form of one or more first spikes. Endoprosthesis Claim 5 or 6th , characterized in that the first anchoring element (1.4) is coated with a biocompatible coating. Endoprosthesis according to one of the Claims 1 to 7th , characterized in that the distal component (3) has a shaft (4) for anchoring in the second finger bone (F2). Endoprosthesis according to one of the Claims 1 to 8th , characterized in that the distal component (3) has at least one second anchoring element (3.2) on its surface facing the second finger bone (F2) to prevent the distal component (3) from rotating. Endoprosthesis Claim 9 , characterized in that the second anchoring element (3.2) is designed in the form of one or more second spikes. Endoprosthesis Claim 9 or 10 , characterized in that the second anchoring element (3.2) is coated with a biocompatible coating. Endoprosthesis according to one of the Claims 1 to 11 , characterized in that the first finger bone (F1) is a phalanx or a metacarpal bone. Endoprosthesis according to one of the Claims 1 to 12 , characterized in that the second finger bone (F2) is a middle phalanx or a phalanx.

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