IL119942A

IL119942A - Modular implant for pelvis reconstruction

Info

Publication number: IL119942A
Application number: IL11994296A
Authority: IL
Inventors: Isaac Meller; Kalman Shvartsman; Lev Goldenberg
Original assignee: M P R S Ltd
Priority date: 1996-12-31
Filing date: 1996-12-31
Publication date: 2002-03-10
Also published as: IL119942A0; AU4218097A; WO1998029058A1

Abstract

An implant for replacement of a region of a pelvic bone by connecting a first portion and a second portion of the pelvic bone, comprising: (a) a main surface (1) including a stiffening rib (2) for connecting the first portion of the pelvic bone and the second portion of the pelvic bone; (b) at least one end surface (3,4) connected to said main surface; and (c) at least one primary bending zone (13, 18) located between said main surface and said at least one end surface for changing the orientation of said at least one end surface relative to said main surface. 380 כ" ו באדר התשס" ב - March 10, 2002

Description

A MODULAR IMPLANT FOR PELVIS RECONSTRUCTION FIELD AND BACKGROUND OF THE INVENTION The present invention relates to a modular implant for pelvis /'reconstruction and, more particularly, to a versatile implant which can be adapted to a specific patient during a real-time operation.

Specifically, the present invention may be used for the replacement of pelvic parts between the acetabulum and the sacrum of a treated patient.

Implants for pelvis reconstruction are widely used in orthopedic oncology. Such implants are often used in cases of bone and soft tissue sarcomas located in or around the pelvis, and in cases of metastatic bone disease (M.B.D.).

However, most of the implants currently used feature low bio- mechanical stability and integrity owing to their flat configuration.

Currently, such configuration is the most commonly used since it makes it possible to immediately transplant the implant without the need to specifically pre-design the implant to a specific patient.

U.S. Patent No. 5,326,367 (Robioneck) describes an implant that gives a solution to only one particular situation in the spectrum of pelvic resections for cancer, i.e. when the acetabulum is missing but the remaining parts of the sacrum SIJ, iliac bone, pubic and ischial bones are there. It is a solution for an extended THR revision. There is no characteristic of modularity as in the present invention.

Similarly, U.S. Patent No. 5,314,490 (Wagner et. al) is not related to replacement of bone defects in the pelvis after cancer resections. It is a solution for revision of the acetabulum, during THR revision, when the amount of subarticular cancellous bone of the acetabular roof is insufficient, i.e. loss of bone stock after revisions. It is obviously not a modular part as is the device described in the present invention. As with '367, this is a specific solution to one particular very small defect in the whole pelvis. It is not used after bone resection for cancer and is unsuitable after resection of the mid-portion of the hemipelvis.

The fiat configuration of the currently used implants is mechanically unfavorable since it fails to provide firm and stable long-term connection to the pelvis and sacrum of a patient, mainly because such portions of the patient's body feature a complex three dimensional configuration. The load on the screws connecting such implants to the bone surfaces of the pelvis and sacrum is not distributed in an optimized manner, exposing the screws to harsh transverse forces which decrease the long-term bio-mechanical stability, integrity and durability of the implant.

Various attempts have been made to design pelvic implants of a three dimensional configuration specifically adapted for a specific patient (customized implants) so as to provide better bio-mechanical stability and integrity to the complex bone-implant. Most of these implants are tailor-made by using methods of precision casting.

However, such implants can be made only after the precise boundaries of the malignant areas have been determined. The preparation of such implants usually takes between four to six weeks. Such a waiting period may be too long for a patient with a failing pelvis due to a metastatic bone disease. Moreover, since the dimensions and shape of such implants are not changeable, the implant may become unsuitable for implantation after that period of time owing to progress of the disease. Furthermore, the production method of precision casting is complex and expensive.

There is thus a widely recognized need for, and it would be highly advantageous to have, a modular versatile implant for pelvis reconstruction which can be adapted to any specific patient during a real-time operation. It would be further advantageous to have a versatile flat implant capable of adopting a three dimensional shape by changing the orientation of its surfaces. It would also be advantageous to have an implant whose shape can be determined and formed real-time in an operation so as to allow immediate transplantation. It would be further advantageous to have such an implant which has favorable mechanical features by having a stiffening rib having a convexo-concave surface shape, and by having optimized distribution of load on the screws such that they are not exposed to harsh transverse forces. It would be further advantageous to have an implant which allows a reliable, firm and stable long-term connection to the bone surfaces of a patient, and which is prepared by using simple and inexpensive production methods.

SUMMARY OF THE INVENTION According to the present invention there is provided an implant for replacement of a region of a pelvic bone, including: (a) a main surface for connecting a first portion of the pelvic area and a second portion of the pelvic area; (b) at least one end surface connected to the main surface; and (c) at least one bending zone for changing the orientation of the at least one end surface relative to the main surface.

According to further features in preferred embodiments of the invention described below, the implant may further include: (a) at least one cantilever element connected to the at least one end surface; and (b) at least one bending zone for changing the orientation of the at least one cantilever element relative to the at least one end surface.

Each of the cantilever elements may include at least one bending zone for changing the orientation of a portion of the cantilever element.

Specifically, the implant may include a first cantilever element connected to a first end surface and a second cantilever element connected to a second end surface, the first cantilever element for connection to an acetabulum of a patient and the second cantilever element for connection to a sacrum of a patient.

According to still further features in the described preferred embodiments, the end surface may be bent along any line within the limits of the bending zone so as to form an angle of between about 0 and about 30 degrees with the main surface.

The cantilever element may be bent along any line within the limits of the bending zone so as to form an angle of between about 0 and about 30 degrees with the end surface.

Further, a portion of the cantilever element may be bent along any line within the limits of the bending zone so as to form an angle of between about 0 and about 90 degrees, or alternatively, between about 0 and about 120 degrees with the rest of the cantilever element.

According to still further features in the described preferred embodiments, the implant includes a stiffening rib. The stiffening rib may feature a convexo-concave shape in cross section.

An implant according to the present invention further includes holes for connecting the implant to the bony surfaces of the pelvis of a patient, preferably by means of screws.

The present invention successfully addresses the shortcomings of the presently known configurations by providing a modular versatile flat implant for pelvis reconstruction capable of adopting a three dimensional shape by changing the orientation of its surfaces. Thus, the shape of such an implant can be determined and formed during a real-time operation, thereby allowing immediate transplantation. Such an implant has favorable bio-mechanical features since it provides an optimized distribution of load on the screws connecting the implant to the bony surfaces of the pelvis, thereby not exposing such screws to harsh transverse forces which decrease the long term stability and durability of the implant.

The present invention discloses a novel modular implant for pelvis reconstruction. While using an implant according to the present invention, the exact size and three-dimensional shape of the implant required for a specific patient is determined during surgery by means of a template which is easy to bend and is identical in shape and size to the required implant. The template is shaped by the surgeon so as to fit the exact dimensions of the pelvic area of a given patient after resection. The implant is then shaped according to the template by using a hand bending tool.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: FIG. 1 is a perspective view of an implant according to the present invention before adopting its three dimensional conformation; FIG. 2 is a partial cross sectional view across line A-A in FIG. 1 ; FIG. 3 is a perspective view of an implant according to the present invention while adopting its three dimensional conformation; FIG. 4 is a schematic view of an implant attached to a pelvic girdle of a patient; FIG. 5 is a cross sectional view across line B-B in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is of a modular implant for pelvis reconstruction which can be adapted to a specific patient during a real-time operation. Specifically, the present invention may be used for the replacement of pelvic parts between the acetabulum and the sacrum of a treated patient. A versatile implant according to the present invention is capable of adopting a three dimensional shape from a flat configuration by changing the orientation of its surfaces. The shape of such implant can be determined and formed during a real-time operation so as to allow an immediate transplantation.

The principles and operation of an implant according to the present invention may be better understood with reference to the drawings and the accompanying description.

Referring now to the drawings, FIGs. 1-5 illustrate an implant according to the present invention. As shown in FIG. 1 , an implant according to the present invention preferably includes: a main surface 1 having a stiffening rib 2 disposed along the longitudinal axis of surface 1; two end surfaces 3 and 4 located at each end of surface 1; and two cantilevers 10 and 11 connected to end surfaces 3 and 4, respectively. Stiffening rib 2 is preferably of a convexo-concave shape in cross section, as shown in FIG. 2. Preferably, the longitudinal side 19 and the transverse sides 20 and 26 of main surface 1 feature a rounded shape so as to minimize damage to soft tissues. As shown in FIG. 1 , cantilevers 10 and 11 are connected to end surfaces 3 and 4. A slot 5 defines the dimensions and shapes of cantilevers 10 and 11. Preferably, slot 5 includes a longitudinal portion 6 and a cutout portion 7, such that the edges 8 and 9 of cantilevers 10 and 11, respectively, form an angle of between about 60 degrees and about 90 degrees with the edge of longitudinal portion 6.

As shown in FIG. 3, an implant according to the present invention further includes bending zones, preferably zones 13, 14, 15, 16, 17 and 18. Preferably, each of end surfaces 3 and 4 and each of cantilevers 10 and 11 include a group of holes 12 for screws, such that bending zones 13, 14, 15, 16, 17 and 18 are formed between the groups of holes 12.

When using an implant according to the present invention, end surfaces 3 and 4 may be bent along any line within the limits of bending zones 13 and 18, respectively, so as to form an angle of preferably 5 between about 0 and about 30 degrees with main surface 1.

Cantilever 10, preferably for attachment to the acetabulum of a patient, may be bent along any line within the limits of each of bending zones 14 and 15. Preferably, cantilever 10 is bent along a line within the limits of bending zone 14 to form an angle of between about 0 and about 10 30 degrees with end surface 3, and along a line within the limits of bending zone 15 to form an angle of between about 0 and about 120 degrees between the two parts of cantilever 10 spaced by bending zone 15.

Cantilever 11, preferably for attachment to the sacrum of a patient, may be bent along any line within the limits of bending zones 16 and 17. 15 Preferably, cantilever 11 is bent along a line within the limits of bending zone 17 to form an angle of between about 0 and about 30 degrees with end surface 4, and along a line within the limits of bending zone 16 to form an angle of between about 0 and about 90 degrees between the two parts of cantilever 11 spaced by bending zone 16. 20 When bending the implant of the present invention into a three- dimensional shape as described above and attaching the implant to a patient's pelvic area, the load is distributed among screws 25 (FIG. 5) in an optimized manner, so that screws 25 are not susceptible to harsh transverse forces. Thus, the long-term bio-mechanical stability of the implant is improved.

The edge 21 of cantilever 10 preferably features a rounded shape so as to facilitate the attachment of end surface 3 and cantilever 10 to the acetabulum. The edges 8 and 9 of cantilevers 10 and 11, respectively, feature a rounded shape so as to minimize damage to soft tissues.

While using an implant according to the present invention, the exact size and three-dimensional shape of the implant required for a specific patient is determined during surgery by using a thin metal template which is easy to bend and is identical in shape and size to the required implant. The template is shaped by the surgeon so as to fit the exact dimensions of the pelvis and sacrum of a given patient after resection. The implant is then shaped according to the template by using a hand bending tool. When fitting the implant to a pelvic area (FIG. 4), cantilever 10 is preferably supported by, and attached to, bony surface 24 formed by the resection of the pelvis, while end surface 3 is supported by, and attached to, bony surface 22 in the immediate proximity of the acetabulum. Cantilever 11 and end surface 4 are preferably supported by, and attached to, bony surface 23 of the sacrum.

The present invention is preferably provided as a set of modular units of templates and pertinent implants of different size, and a hand bending tool for bending the implants. For example, a set of modular units may include templates and pertinent implants having lengths of between about 80 mm and about 140 mm, and graded with differences of about 5-10 mm. The templates and implants are preferably made of stainless steel commonly used for endoprostheses. The method of production used for preparing the implants preferably includes cold stamping and electro-polishing of the implant surface.

While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made.

Claims

WHAT IS CLAIMED IS:

1. An implant for replacement of a region of a pelvic bone by connecting a first portion and a second portion of the pelvic bone, comprising: (a) a main surface including a stiffening rib for connecting the first portion of the pelvic bone and the second portion of the pelvic bone; (b) at least one end surface connected to said main surface; and (c) at least one primary bending zone located between said main surface and said at least one end surface for changing the orientation of said at least one end surface relative to said main surface.

2. The implant of claim 1 , wherein the implant includes a first end surface and a second end surface, said first end surface.:for--connection to the first portion of the pelvic bone and said second end surface for connection to the second portion of the pelvic bone.

3. An implant for replacement of a region of a pelvic bone by connecting an acetabulum and a sacrum of a patient, comprising: 119942/2 12 (a) a main surface including a stiffening rib for connecting the ; acetabulum and the sacrum; (b) a first end surface and a second end surface connected to said main surface; and (c) primary bending zones located between said main surface and each of said end surfaces.

4. The implant of claim 1 , further comprising: (a) at least one cantilever element connected to said at least one end surface; and (b) at least one secondary bending zone located between said at least one end surface and said at least one cantilever element for changing the orientation of said at least one cantilever element relative to said at least one end surface.

5. The implant of claim 4, wherein said at least one cantilever element includes at least one tertiary bending zone for changing the orientation of a portion of said cantilever element.

6. The implant of claim 5, wherein said implant includes a first cantilever element connected to a first end surface and a second cantilever element connected to a second end surface, said first cantilever element for connection to the first portion of the pelvic bone and said second cantilever element for connection to the second portion of the pelvic bone.

7. The implant of claim 3, further comprising: (a) a first cantilever element connected to said first end ~" " surface and a second cantilever element connected to said second end surface, said first cantilever element for connection to the acetabulum and said second cantilever element for connection to the sacrum; and (b) two secondary bending zones, each of which being located between a cantilever element and a respective end surface.

8. The implant of claim 7, wherein each of said cantilever elements includes a tertiary bending zone.

9. An implant for replacement of a region of a pelvic bone by connecting a first portion and a second portion of the pelvic bone, comprising: (a) a main surface including a stiffening rib for connecting the first portion of the pelvic bone and the second portion of the pelvic bone; (b) at least one cantilever element connected to said main surface; and (c) at least one primary bending zone located between said main surface and said at least one cantilever element for changing the orientation of said at least one cantilever element relative to said main surface.

10. The implant of claim 9, wherein said at least one cantilever element includes at least one secondary bending zone for changing the orientation of a portion of said cantilever element.

11. The implant of claim 1 , wherein said at least one end surface is bent along a line within the limits of said at least one primary bending zone so as to form an angle of between about 0 and about 30 degrees with said main surface.

12. The implant of claim 4, wherein said at least one cantilever element is bent along a line within the limits of said at least one secondary bending zone so as to form an angle of between about 0 and about 30 degrees with said at least one end surface. 119942/2 15

13. The implant of claim 5, wherein said portion of said at least one cantilever element is bent along a line within the limits of said at least one tertiary bending zone so as to form an angle of between about 0 and about 90 degrees with the rest of said cantilever element.

14. The implant of claim 5, wherein said portion of said at least one cantilever element is bent along a line within the limits of said at least one tertiary bending zone so as to form an angle of between about 0 and about 120 degrees with the rest of said cantilever element. 15· The implant of claim 1 v , wherein said stiffening rib has a convexo-concave shape in cross section. 1* . The implant of claim 1 , wherein said implant includes holes for screws. \H. The implant of claim 6, wherein the dimensions and shapes of said cantilever elements are defined by a slot having a longitudinal portion and a cut-out portion. Mark M. Friedman Advocate, Patent Attorney Beit Samueloff 7 Haomanim 67897 Tel Aviv