A DEVICE FOR AND METHOD OF REPLACING OR REPAIRING A JOINT

Abstract: In an operation to repair a hip or other joint, a tunnel (T) is bored from behind the articular surface (S) through the neck (N) and head (H) of the femur so as to gain access to the articular space of the joint. A prosthesis may be inserted in the tunnel (T) so that a head portion (12) is located in the articular space. The head portion (12) may include a ceramic cap (14) for maintaining articular separation, a sac (16) for cushioning the articular surface (S) or a covering (18) for the articular surface (S). The prosthesis may be in the form of a sleeve member (2) screwed into the tunnel (T) and an inner member (8) screwed into the sleeve member (2) and carrying the head portion (12), the position of the inner member (8) being adjustable so as to locate the head portion (12) as desired in the articular space.

Description: A DEVICE FOR AND METHOD OF REPLACING OR REPAIRING A JOINT Field of The Invention The present invention relates to a device for replacing or repairing a joint. More particularly but not exclusively the present invention relates to a prosthesis for a joint, adapted for insertion from behind an articular surface of the joint through said surface, and adapted to abut the opposing articular surface. Background Standard joint replacement technology and methodology has remained substantially unchanged for 30 years or more. Hip replacement operations, for example, have involved the replacement of the head of the femur with alloy implants which allow ball and socket motion of the hip joint. The surgery involved is invasive, requires a great deal of physical work and thus requires a great deal of training which makes it a costly procedure to perform. Many joint implants currently available, such as hip joint implants, require the removal of a substantial amount of bone mass which is replaced by a rigid metallic implant. Implanting such devices produces complications which are well documented in medical literature. Furthermore, the removal of a substantial amount of bone mass to replace relatively minor articular damage is undesirable. Furthermore, current methods of repairing or replacing joints involve substantial damage to the sinovial membranes and other joint lubrication structures to gain access to the joint. International Patent Application Publication Number WO 98/34567 describes a hip prosthesis and a method for fitting such a prosthesis through a femoral bone extending from the outside of the femur to the femoral head, which is removed. The prosthesis and method for fitting are suitable for total hip replacement surgery where both the ball and socket of the joint are replaced. US Patent Number 4.714,478 describes an endoprosthesis comprising a flexible, collapsible, hollow device which can be filled after it is positioned within the bone structure. A method of installing such an endoprosthesis to replace the ball of the femur is also described in which a portal is drilled through the lateral cortex of the femur at a location opposite the ball, the ball of the femur is removed, and the endoprosthesis is inserted through the portal. Summary of the Invention According to a first aspect of the present invention there is provided a prosthesis for a joint, adapted for insertion from behind an articular surface of the joint through said surface, and adapted to abut the opposing articular surface, said prosthesis being substantially rigid and adjustable after insertion. Various further or alternate aspects of the present invention are set out in the accompanying claims. An advantage of a prosthesis adapted for insertion from behind an articular surface of a joint is that damage to the membranes surrounding the joint is avoided. An advantage of a prosthesis useable in a tunnel or passage bored or otherwise formed from behind the articular surface of a joint is that portions of the prosthesis for maintaining articular space, cushioning the joint and/or covering one or both of the articular surfaces can be easily and controllably inserted into the articular space. The prosthesis may be left in the bone behind the articular surface, so as to strengthen the joint. Alternatively, the prosthesis can be removed after surgery and the tunnel or passage filled with appropriate material. Preferably, the prosthesis comprises a hollow elongate member adapted to engage the surrounding bone in the tunnel and an inner member which can be engaged within the hollow elongate member such that its longitudinal position therein can be adjusted from the outer end of the tunnel. Preferably, the inner member has a head which can be positioned within the articular space. The head may be permanently fixed to the end of the inner member, or may be detachable so as to remain in the articular space after the prosthesis is removed. The inner member may carry a conduit or mechanical connector allowing the head to be actuated form the outer end of the tunnel. Specific embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a sleeve member of a prosthesis in an embodiment of the present invention, with two alternative surfaces being shown in Figures la and lb; Figures 2a to 2c show alternative inner members for insertion into the sleeve member of Figure 1 ; Figures 3a to 3c show, from each end and from the side, the respective inner members of Figures 2a to 2c, when inserted in the sleeve member; Figures 4a to 4c show views of the prosthesis with the respective inner members of Figures 2a to 2c, in situ in a bore cut through the head and neck of the femur, which are shown cut away to reveal the prosthesis; and Figures 5a to 5c show corresponding views to Figures 4a to 4c, but with the sleeve member shown in cross-section to show the inner member within. A method and apparatus for inspecting, and repairing a hip joint according to embodiments of the invention will now be described. The method is preferably performed on a patient under local anaesthesia and sedation. First, the patient is placed on an orthopaedic theatre table in a supine position with a support under the hip so as to tilt laterally the thigh of the hip on which the operation is to be performed. An image intensifier fluoroscope or other radiological imaging device is set up so that the neck N of the femur and the hip joint can be visualised. After asepsia of the skin, the patient is draped, including double draping of the foot and knee of the operated leg, as the assistant may need to rotate the leg during arthroscopy. Next, a small incision of approximately 5 cm is made on the lateral aspect of the thigh at approximately 5 cm from the lower end of the greater trochanter and the bone is exposed. A guide wire is introduced into the neck N and head H of the femur, visualised by the image intensifier. Once the guide wire has been located correctly, a tunnel T, preferably of 18 to 20 mm diameter, is drilled through the neck N and head H of the femur, from the outer side of the femur into the articular space between the hip bone and the head H of the femur. Residual drilled bone is aspirated out through the tunnel T. Because the tunnel T is drilled into the articular space from behind the articular surface S of the femur, the sinovial membranes are not damaged. Next, an arthroscope is introduced through the tunnel T into the articular space of the hip joint, and the joint is inflated with fluid or gas, so that the surgeon can inspect the joint and decide what type of treatment and what type and size of prosthesis is required. The endoscope may be used to remove foreign bodies and reshape damaged articular surfaces, for example by removing osteophites with a rotor or an articulated rotating burr, and to implant cultivated cartilage or bone morphonic proteins (BMP), for example by means of reabsorbable staples. A screw microprosthesis, as described below, may be inserted into the tunnel T. The prosthesis comprises a sleeve member, and an inner member which is located within the sleeve member and which carries a head selected according to the function to be performed. The sleeve member 2, as shown in Figure 1 , has a diameter compatible with the diameter of the tunnel T, for example 18 to 20 mm, and a length equal to or less than that of the tunnel T. The sleeve member 2 is manufactured of titanium or any other biologically compatible metal, alloy or synthetic material of sufficient strength. The outer surface of the sleeve member 2 carries a screw thread 4, preferably a lag screw thread. The sleeve member 2 is a hollow cylinder and carries an inner screw thread on its inner wall. The proximal end of the sleeve member 2 carries a nut 6 which is rigidly fixed to or integrally formed with the sleeve, allowing the sleeve member 2 to be easily rotated. The sleeve member 2 is screwed into the tunnel T, with the outer screw thread engaging the bone in the tunnel wall, so that its distal end lies flush with or slightly behind the articular surface S of the femur and its proximal end lies within the tunnel T. Two alternative surface textures are provided on the outer surface of the sleeve member 2. If the sleeve member 2 is intended to be removed from the tunnel T after the hip operation, the surface of the outer screw thread is smooth, as shown in the inset Figure la. Alternatively, if the sleeve member 2 is intended to be permanently fixed in the tunnel T. the surface of the outer screw thread is pitted, as shown in the inset Figure lb. The pits allow bone growth into the ridges of the outer screw thread, which permanently fixes the sleeve member 2 within the tunnel T. Once the sleeve member 2 is positioned in the tunnel T. a generally cylindrical inner member 8 is inserted into the sleeve member 2. The inner member 8 is shorter than the sleeve member, for example by 10 mm. The distal section of the inner member 8 carries an outer screw thread 9 which conforms with the inner screw thread of the sleeve member, so that the longitudinal position of the inner member 8 within the sleeve member 2 can be adjusted by rotating the inner member 8. A slot 10 is provided in the proximal end of the inner member 8 to allow adjustment of the inner member 8 within the sleeve member 2, by means of a screwdriver. The inner member 8 carries a head 12 is located within the articular space. In a first embodiment shown in Figures 2a, 3a, 4a and 5a, the head 12 comprises a metal sphere 13 covered by a ceramic cup 14 of the same diameter as the tunnel T. The inner member 8 is screwed into the sleeve member 2 so that the ceramic cup 14 abuts the hip socket surface and maintains an adjustable separation between the articular surfaces of the femur and the socket, while allowing rotation of the femur. In a second embodiment shown in Figures 3b, 4b and 5b, the head 12 comprises an inflatable sac 16 connected to a fluid conduit 17 extending through the inner member 8. The sac 16 is deflated during insertion of the inner member 8, until the head 12 is located within the articular space. Fluid or semisolid is then introduced through the conduit 17 into the sac 16, which inflates in the articular space and provides a cushion between the articular surfaces. The conduit is then sealed, for example at the proximal end of the inner member 8, to maintain the desired degree of inflation. In a third embodiment, the head 12 comprises a unfurlable covering 18 which is furled as the inner member 8 is screwed into the sleeve member 2. The covering 18 is unfurled within the articular space so that it covers at least part of the articular surface S of the femur, so as to protect the surface from wear. A mechanical connector 20, for furling and unfurling the covering, passes through a passage in the inner member 8 and is operable from the proximal end. The covering 18 may have a support which is substantially rigid when unfurled. The prosthesis may be completely removed following the operation, in which case the tunnel T is filled with a threaded dowel of Surgibone, the tip of which is covered with cultivated cartilage. Alternatively, the prosthesis may be left in place; the prosthesis strengthens the neck N and head H of the femur and the head 12 remains in the articular space. The proximal end of the prosthesis is buried under the cortical bone of the femur. If it is subsequently necessary to adjust the position of the inner member 8, for example to adjust the articular separation using the prosthesis of the first embodiment, the cortical bone is removed and the inner member 8 screwed in or out as required. In a further alternative in the second and third embodiments, the head 12 is detached from the inner member 8 in its inflated or unfurled state in the articular space. The fluid conduit in the second embodiment may be sealed close to the sac 16, while the mechanical connector 20 in the third embodiment may have a point of weakness close to the covering 18 so that it can be detached. The inner member 8 and the sleeve member 2 are removed and replaced with the threaded dowel. To complete the operation, the tissue layers are closed and dressings applied. If the prosthesis is not used following arthroscopy, the tunnel T is filled with the threaded dowel in the same way as if the prosthesis had been removed. The position of the tunnel T provides an advantageous means of access to the articular space for arthroscopy, independently of whether a prosthesis is subsequently inserted. The sleeve member 2 could be inserted into the tunnel T to provide a passage for an endoscope, without the inner member 8 being inserted. In that case, the sleeve member 2 need not have an internal screw thread, but instead may have a smooth inner surface to allow the endoscope to be slid in and out easily; preferably the outer surface of the sleeve member 2 is smooth as shown in Figure la, to allow subsequent removal.

Claims: CLAIMS 1. A prosthesis for a joint, adapted for insertion from behind an articular surface of the joint through said surface, and adapted to abut the opposing articular surface, said prosthesis being of high strength and adjustable after insertion. 2. A prosthesis according to claim 1, securable to the bone or other material behind said articular surface. 3. A prosthesis according to claim 2, securable such that the position of said prosthesis within said bone or other material can be adjusted. 4. A prosthesis according to claim 1, comprising a sleeve member securable to the bone or other material behind said articular surface. 5. A prosthesis according to claim 4, wherein said sleeve member is securable such that the position of the sleeve member within said bone or other material can be adjusted. 6. A prosthesis according to claim 4 or claim 5, wherein at least part of the outer surface of said sleeve member is textured so as to promote attachment thereto of said bone or other material. 7. A prosthesis as claimed in claim 6, wherein the textured part of the outer surface comprises a plurality of pits. 8. A prosthesis according to any one of claims 4 to 7, wherein the outer surface of said sleeve member carries a screw thread for engaging said bone or other material. 9. A prosthesis according to claim 8, wherein said screw thread is a lag screw thread. 10. A prosthesis according to any one of claims 4 to 9, further comprising an inner member insertable in said sleeve member. 11. A prosthesis according to claim 10, wherein the inner member is securable within the sleeve member such that the position of the inner member within the sleeve member can be adjusted. 12. A prosthesis according to claim 1 1, wherein the inner member has a threaded engagement within the sleeve member. 13. A prosthesis according to any one of claims 10 to 12, wherein the inner member has a head portion adapted for location in, or adjacent to, the articular space of the joint. 14. A prosthesis according to claim 13, wherein said head portion is adapted to support said articular surface or said bone or other material. 15. A prosthesis according to claim 13 or claim 14, wherein said head portion is adapted to at least partially replace or cover said articular surface while allowing articular movement. 16. A prosthesis according to any one of claims 13 to 15, wherein said head portion is adapted to create or maintain articular space in the joint. 17. A prosthesis according to claim 15 or claim 16, wherein said head portion comprises a rigid curved portion for at least partially replacing or covering said articular surface. 18. A prosthesis according to claim 15 or claim 16, wherein said head portion comprises a deformable portion for at least partially replacing or covering said articular surface. 19. A prosthesis according to claim 18, wherein said deformable portion is a sac. 20. A prosthesis according to claim 19, wherein the inner member includes means for introducing a fluid or semi-solid into said sac. 21. A prosthesis according any one of claims 15 to 20, wherein said head portion is adapted to expand so as to at least partially replace or cover said articular surface. 22. A prosthesis according any one of claims 1 to 21, wherein said joint is a hip joint. 23. A method of examining or repairing a joint or at least partially replacing an articular surface of a joint, including the steps of: a) creating a passage substantially up to or through an articular surface of a joint through the bone or other material from behind said articular surface; b) inserting a prosthesis as claimed in any one of claims 1 to 22 in said passage substantially up to or through said articular surface. 24. A method according to claim 23 including the step of: i) removing foreign bodies or osteophites within the articular space of the joint accessible through said passage. 25. A method according to claim 23 or claim 24, including the step of: ii) repairing or reshaping at least part of said articular surface accessible through said passage. 26. A method according to any one of claims 23 to 25 including the step of: iii) implanting cultivated cartilage, osteomorphogenic proteins or other bio-materials into said joint through said passage. 27. A method according to any one of claims 24 to 26 wherein one or more of steps i), ii), and iii), when performed, are performed prior to performing step b). 28. A method according to any one of claims 24 to 26 wherein one or more of steps i), ii), and iii), when performed, are performed using said prosthesis after performing step b). 29. A method according to claim 25 or 26 wherein when two or more of steps i), ii), and iii) are performed, at least one of steps i), ii), and iii) is performed prior to performing step b) and at least one other of steps i), ii), and iii) is performed using said prosthesis after performing step b). 30. A method according to any one of claims 23 to 29 wherein said prosthesis is adjustable after said repairing or replacing such that the articular space of said joint is enlarged or reduced. 31. A method of adjusting the articular space in a joint in which is implanted a prosthesis by the method of claim 23 when dependent on claim 16, including adjusting the position of the prosthesis in the joint. 32. A prosthesis substantially as herein described with reference to Figure 1 of the drawings. 33. A prosthesis as claimed in claim 32, further substantially as herein described with reference to Figure la of the accompanying drawings. 34. A prosthesis as claimed in claim 32, further substantially as herein described with reference to Figure lb of the accompanying drawings. 35. A prosthesis as claimed in any one of claims 32 to 34, further substantially as herein described with reference to Figures 2a, 3a. 4a and 5a of the accompanying drawings. 36. A prosthesis as claimed in any one of claims 32 to 34, further substantially as herein described with reference to Figures 2b, 3 b, 4b and 5b of the accompanying drawings. 37. A prosthesis as claimed in any one of claims 32 to 34, further substantially as herein described with reference to Figures 2c, 3c, 4c and 5c of the accompanying drawings.

Inventors: CABRERA CONTRERAS JAVIER MIGUE, CABRERA CONTRERAS, JAVIER, MIGUEL
Applicants: CABRERA CONTRERAS JAVIER MIGUE, CABRERA CONTRERAS, JAVIER, MIGUEL
Application year: 2000
Main classification: A61F2
IPC codes: A61B17, A61F2