AU630183B2

AU630183B2 - Anchoring element for supporting a joint mechanism of a finger or other reconstructed joint

Info

Publication number: AU630183B2
Application number: AU53297/90A
Authority: AU
Inventors: Per-Ingvar Branemark
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-04-25
Filing date: 1990-04-18
Publication date: 1992-10-22
Anticipated expiration: 2010-04-18
Also published as: FI103865B1; FI902050A0; CZ284504B6; CN1032189C; AU642353B2; ES2018769T3; DE59004539D1; NO176344C; JP2552752B2; BR9001906A; AU5329790A; HU902544D0; JPH031854A; DK0396519T3; DD301734A9; HU213427B; ES2018769A4; EP0396519B1; EP0396519A1; NO176344B

Description

S____0183 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 FORM Case 4563-AU Application Number: Class: Int. Class Lodged: Complete specification: Lodged: Accepted: Publishea: 0 Priority: 40 0 0 0 Related Art: 4 41 o f 4 0 8 Name of Applicant: PER-INGVAR BRANEMARK g444 Address of Applicant: Andergatan 3, S' S-431 69 Molndal, Sweden 944 Actual Inventor: PER-INGVAR BRANEMARK Address for Service:r iFpH F .ELLICTON C nsL457 St.. da Ro C EGk U Melbourne, 3004, VictoGria.

1,22.10 lie S, Complete Specification for the invention entitled: "ANCHORING ELEMENT FOR SUPPORTING A JOINT MECHANISM OF A FINGER OR OTHER RECONSTRUCTED JOINT" The following statement is a full description of this invention including the best method of performing it known to us, 1 IY I I -1A BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to an anchoring element for supportin9 a joint mechanism, a method of applying an anchoring element within a bone, and a reconstructed joint.

A preferred embodiment of the invention will be described in detail in the following with reference to the reconstruction of a finger joint. However, the invention is not limited thereto, The invention can be used for other similar joints, sMuch as toe joints, elbow joints, and so on.

The invention can alsc be used in reconstructions after amputation or other defects.

Description of the Related Art: Finger-joint reconstructions, entailing prostheses, are primarily carried out on MCP joints which have become rheumatically changed. Prostheses known for this purpose include Swanson Silastic finger joints. Such joints consist of a material similar to silicon, are elongate in shape, and have ends with substantially circular cross sections, The ends can be substantially circular cross sections. The ends can be fitted and anchored into the marrow cavity of each bone, The central portion of the prosthesis is elastically deformable and thus constitutes the actual joint mechanism.

The St. George prosthesis, a cemented prosthesis, is also known for finger-joint reconstructions.

A problem with these conventional prostheses is that the anchoring element supporting the actual prosthesis mechanism loosens and/or are damaging the surrounding tissue with Undesired displacement of the prosthesis in the direction of load. Attempts have therefore been made in LI- II L; =I- 2recent years to use titanium fixtures anchored in the marrow cavity of the bone with the object of becoming osseointegrated as described by Harert et al. "Metacarpophalangal Joint Replacement with Osseo-integrated Endoprostheses" in Scand. J. Plast. Reconstr. Surg. 20, pages 207-218, 1986. It is already known to permanently anchor oral and extraoral prostheses in bone tissue. This dental osseo-integration technicque has been developed over the last 25 years by Professor Branemark and his colleagues, with excellent results in applying fixtures in the jawbone to hold teeth or arch attachments. However, the experiments performed by Hagert to apply this technique to the reconstruction of finger joints has not fulfilled expectations. The o unacceptable results are evidently due to the entirely 15 different conditions encountered when using this "dental technique" in the prosthetic reconstruction of finger-joints.

For example, in the known techniques, the fixture is anchored at right angles to the longitudinal axis of the bone. In the finger joint, the fixture is placed along the axis of the bone. Of course, this creates totally different loads and stresses on the anchoring elements, Today, the main problem in orthopedic prosthesis surgery is still loosening of the bone anchoring unit.

However, with a success rate for dental implants of more than 90% over a 20 year period, a number of other problems arise which, so far, it has been unnecessary to take into account.

One of the major problems is increased wear on the joint mechanism. A different type of prosthesis design from that used hitherto is required if the osseo-integration method is to be applied. To enable the joint mechanism to be replaced without disturbing the bone anchorage, the prosthesis system must be divided into components where the joint-mechanism element can be separated from the actual bone-anchoring element. Further, if the two-stage method is to be used, it -3must be possible to connect the joint mechanism in the second stage if the patient, or at least the patient's reconstructed joint, is not to be kept immobilized. Two factors must therefore be taken into account: First, the joint mechanism is subject to wear and therefore must be replaceable.

Second, to use the two-stage method, the joint mechanism must be replaceable.

SUMMARY OF THE INVENTION It has now surprisingly been found that the problems and drawbacks of the techniques described above can be eliminated by the present invention.

The invention is based on extensive experimental biological analysis of the structure and function of joints in the course of a disease or in defective state after wear a 15 or inflammatory decomposition of bone tissue and extensive :44studies of the vascular supply to the bone marrow. It has been established that, in the synthetic replacement of destroyed articular cartilage and ligament, bone and marrow tissue must be treated as a structural and functional unit.

It is absolutely npr,-ssary to account for the cooperation between the bone and marrow tissue, particularly over a long period of time, if the hard tissue is to function as a support element, The invention is thus based on the realization that, when anchoring a prosthetic replacement for a joint surface and ligament to parts of the skeleton close to a 0 4joint, the interaction between bone marrow and bone tissue must be respected. This means that an attachment element in the marrow cavity of a long bone must be anchored by mechanical elements which will permit communication between marrow and bone tissue along, as far as technically possible, the entire length of the anchoring element, paying particular attention to the boundary layer between marrow and compact bone in the wall of the marrow cavity.

I -I 1-- -4- Therefore, in one aspect of the present invention there is provided ar anchoring element for supporting a joint mechanism, :rein said anchoring element is substantially rotationally symmetrical, at least partially hollow, and includes a material which is compatible with the tissue of a bone, said anchoring element having a surface which can be at least partially osseointegrated with the tissue to achieve permanent endosteal anchorage in the longitudinal axis of the bone, said anchoring element further comprising a deformable, sleeve-like body having: a radially outer surface with external threads for screwing said anchoring element into the bone; a joint end located close to the joint mechanism and a guide sleeve, said joint end being positioned and secured in a lower end of said guide sleeve such that said guide sleeve surrounds said joint end.

In a second aspect of the present there is provided a joint reconstruction, comprising: a bone; a joint mechanism; and an anchoring element detachably receiving said joint mechanism, said anchoring element being substantially rotationally symmetrical, at least partially hollow, and includes a material which is compatible with the tissue of said bone, said anchoring element also having a surface which is at least partially osseo-integrated with the tissue thereby achieving permanent endosteal anchorage in the longitudinal axis of said bone, said anchoring element further comprising a deformable, sleeve-like body having: a radially outer surface with external threads for screwing said anchoring element into the bone; a joint end located close to the joint mechanism and a guide sleeve, said joint end being positioned and secured in a lower end of said guide sleeve such that said guide sleeve surrounds said joint end.

I

4a In a third aspect of the present there is provided a method of applying an anchoring element within a bone, comprising: cutting the bone close to its joint to expose the marrow cavity of the bone; forming a space in the marrow cavity close to the joint; applying a guide sleeve in the space; and screwing the anchoring element into the marrow cavity while using the guide sleeve to center the anchoring element.

Other features and advantages of the invention will become apparent from the following description of a preferred embodiment of the invention, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a partial cross-sectional view of a reconstructed finger joint with an anchoring element embodied by the present invention; Figure 2 shows the fully reconstructed finger joint of figure 1; Figure 3 illustrates how the anchoring element of figure 1 is located in the long bone; Figure 4 is a perspective view of the anchoring element of figure 1; Figure 5 is a cross-sectional view along the line of figure 4; Figure 6 is a partial cross-sectional view along the line 6-6 of figure 4, and illustrates a portion of the joint mechanism embodied by the present invention; and Figure 7 illustrates the assembly of the joint mechanism and anchoring elements embodied by the present invention.

Figures 8 to 10 illustrate some further embodiments of the present invention showing how the non rotatable wedge effect between the anchoring element and the guide sleeve can be achieved and/or improved.

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5 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In Fig. 1, the parts of a long bone on each side of a finger joint mechanism 1 are designated 2 and 3, respectively.

A rotationally symmetrical anchoring element 4 is formed of a hollow, substantially sleeve-like body 5 with external threading 6 and decreasing wall thickness. The open insertion end 7 of the body 5 tapers and is provided with slits 8 and 9 initiating from the open end 7.

The end 13 (Fig. 6) of the anchoring element 4 closest to the joint mechanism 1 is located in a guide sleeve 11. The shown sleeve 11 is substntially cylindrical and is provided with longitudinal corrugations along its radially outer surface. These corrugations may suitably be identical to an axial section of tapped rotation-symmetrical fixtures used in dentistry. The guide sleeve 11 surrounds the joint end 13. The joint end 13 of the body 5 is thus locked by a wedge effect against the inner surface 14 of the guide sleeve 11 when the body 5 has been screwed sufficiently far into the bone tissue. The joint end 13 detachably receives connection parts 15 of the joint mechanism 1. The connection parts may be centered dowels (Fig. 7) protruding from the joint mechanism 1. Such dowels cooperate with corresponding recesses 16 in the anchoring element 4 or a connection piece (not illustrated) arranged suitably between the guide sleeve 11 and the joint mechanism 1.

-*y I I 19 6 One or more holes may be directly connected with the radially outer surface of the anchoring element 4, with the edges of the holes toward the surface forming cutting edges. Self-tapping is thus achieved when the body 5 is screwed into the bone 2. The removed bone tissue 17 is taken up inside th.e anchoring element 4 as illustrated in Fig. Since the thickness of the wall of the anchoring element 4 gradually decreases toward the insertion end 7 and/or since the element 4 has the longitudinal slits 8 and 9, the requirement for good deformation is fulfilled, thus greatly reducing the risk of concentrated stress which causes particular problems in prior art designs. The arrows B-B in oo Fig. 1 denote the flexibility of the open end 7, i.e. its S1 5 ability to adjust to the surrounding tissue, The same or 15 applies to the arrows A-A.

00 31 o °The slits 8 and 9 may suitably be provided with 0a cutting edges and, since the hollow cavity takes up the shavings 17, as illustrated in Fig. 5, the anchoring element 4 is, in itself, its own preparation tool, At the same time, optimum conditions for normal anatomical and physiological oo~o situations are ensured such that disturbance of the remaining b,-oqical tissue, i.e. marrow and bone tissue, is minimized.

Fig. 2 shows the joint reconstruction achieved with the anchoring element 4 in place.

Fig. 3 illustrates how the anchoring element 4 is positioned in the bone 2. When in use, the anchoring element 4 is positioned in the boundary zone between marrow and bone tissue, The wall thickness of the sleeve-like body decreases toward the slit insertion end 7, finishing in a cutting tapered edge 12. The edges of the longitudinal slits 8 may also be in th form of cutting edges. The shavings 17 produced when the anchoring element 4 is screwed into the marrow cavity are thus transferred to the hollow space inside the body 5 as illustrated in Fig. L _IC~L- Js I lL 7 In operation, the part of the long bone 2 close to the joint is cut, thus exposing the marrow cavity. A probe (not illustrated) is then inserted into the marrow cavity to localize a- suitable longitudinal axis for insertion of the anchoring element 4. The probe is used as a direction finder to center the anchoring element 4 as desired. A recess for the guide sleeve 11 is then carefully drilled in the exposed marrow cavity. After application of the guide sleeve 11, the sleeve-like body 5 is screwed down into the marrow cavity through the guide sleeve 11. The probe has of course been previously removed. The joint end 13 of the anchoring element 4 widens somewhat outwardly and upwardly as illustrated at 18 such that its diameter is slightly larger than the lower opening of the guide sleeve 11. Thus, a wedge effect will finally occur between the joint end 13 and the guide sleeve 11 (when the sleeve 11 is moved to the position illustrated in dotted line-s in Fig. so that both guide sleeve 11 and sleeve-like body 5 are positioned as desired.

The anchoring element 4 and the guide sleeve 11 consists of or are manufactured of titanium or are coated with titanium. The structure of the titanium surface is such that, at least over part of the relevant surface, integration is promoted. Advantageously, the surface may have irregularities consisting of micro-pitti.ng, as described in Swedish patent 7902035-0, with pitting diameters of between and 1000 nm, preferably 10-300 nm. Alternatively, the chemical composition of the titanium surface layer may be given certain positive tissue reactions, as described in Swedish patent 8505158-9, for instance.

Fig. 8 shows how the upper end 19 of the sleeve 11 facing the flange 20 of the element 4 is provided with a protruding edge 21 arranged to cooperate with threads 22 on said flange 20. The element 4 and sleeve 11 are thus nonerotatably locked when the body 5 has been screwed sufficiently far into the bone tissue.

8~ a~-y- 8 An alternative locking effect between the sleeve 11 and element 4 is achieved by the arrangement shown in Fig.

9, wherein axially arranged corrugations are arranged to cooperate with the inner surface of the sleeve 11.

A further locking effect may be achieved by the arrangement shown in Fig. 10 by a special thread 24 of the upper rim of the element 4, which is screwed into the tissue.

Although the invention has been described in relation to a preferred embodiment thereof, many other variations ind modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the invention be limited not by the specific disclosura herein, but only by the appended claims, The matter contained in each of the following claims is to be read as part of the general description of the present invention.

Claims

1. An anchoring element for supporting a joint mechanism, wherein said anchoring element is substantially rotationally symmetrical, at least partially hollow, and includes a material which is compatible with the tissue of a bone, said anchoring element having a surface vhich can be at least partially osseointegrated with the tissue to achieve permanent endosteal anchorage in the longitudinal axis of the bone, said anchoring element further comprising a deformable, sleeve-like body having: a radially outer surface with external threads for screwing said anchoring element into the bone; a joint end located close to the joint mechanism and a guide sleeve, said joint end being positioned and secured in a lower end of said guide sleeve such that said guide sleeve surrounds said joint end.

2. An anchoring element according to claim 1, wherein said joint end has a flange and said guide sleeve has a protruding edge which is directed toward the joint mechanism, said flange including teeth which cooperate with said protruding edge to lock said sleeve-like body to said guide sleeve when said anchoring element is screwed into the bone.

3, An anchoring element according to claim 1, wherein said joint end has axially arranged corrugations which cooperate with an inner surface of said guide sleeve to lock said sleeve-like body to said guide sleeve when said anchoring element is screwed into the bone.

4. The anchoring element of claims to 3, wherein said material of said anchoring element is titanium.

11771-A/30.07,92 10 The anchoring element of claims 1-3, wherein said surface of said anchoring element is coated with titanium. 6. The anchoring element of claims 1 to 3, wherein the joint mechanism is an element of a reconstructed finger joint. 7. The anchoring element of claims 1 to 3, wherein said surface of said anchoring element is a radially outer surface which is at least partially micro-pitted with pitting diameters of between 10-300 nm. 8. The anchoring element of claims 1 to 3, further comprising holes directly connected to said radially outer surface, said holes having cutting edges at said radially outer surface. 9. The anchoring element of claims 1 to 3, wherein said sleeve-like body has a wall and an open insertion end, the thickness of said wall gradually decreasing toward said insertion end, The anchoring element of claim 9, further comprising longitudinal slits through said wall, said slits extending from said insertion end toward the joint mechanism. 11. The anchoring element of claim 10, wherein said slits having cutting edges. 12. The anchoring element of claim 11, wherein said joint end expands in the direction of the joint mechanism. 13. The anchoring element of claims 1 to 3, wherein said joint end defines an open end facinc the joint mechanism 217if-A/,0.07.92 I i iYULII~IIII^I-.I-I _ill~ili~ii liil.~-ii_(i-il 11 for detachably receiving the joint mechanism. 14. A joint reconstruction, comprising: a bone; a joint mechanism; and an anchoring element detachably receiving said joint mechanism, said anchoring element being substantially rotationally symmetrical, at least partially hollow, and includes a material which is compatible with the tissue of said bone, said anchoring element also having a surface which is at least partially osseo-integrated with the tissue thereby achieving permanent endosteal anchorage in the longitudinal axis of said bone, said anchoring element further comprising a deformable, sleeve-like body having: a radially outer surface with external threads for screwing said anchoring element into the bone; a joint end located close to the joint mechanism and a guide sleeve, said joint end being positioned and secured in a lower end of said guide sleeve such that said guide sleeve surrounds said joint end. An anchoring element for supporting a joint mechanism substantially as hereinbefore described with reference to any one of the embodiments illustrated in Figures 1 to 10 of the accompanying drawings. 16. A joint reconstruction sub.-.sntially as hereinbefore described with reference to any one of the embodiments illustrated in Figures 1 to 10 of the accompanying drawings. DATED this 31st day of July 1992 PER-INGVAR BRANEMARK By his Patent Attorneys GRIFFITH HACK CO