Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
1999-11-09
2004-05-18
Snow, Bruce (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
C623S001150
Reexamination Certificate
active
06736844
ABSTRACT:
The invention essentially relates to a spiral stent forming device as well as to a method of making it.
It is known that devices forming endoprotheses, also known as “stents”, enable treating narrowing of various canals of the human anatomy, such as an artery, and to keep them open.
Several types of stents exist: tubular, network, filamentary, balloon-expandable or self-expandable stents.
For example, the document U.S. Pat. No. 5,578,149 as well as U.S. Pat. No. 5,591,230 describe a stent which is formed by a filamentary element coiled in a spiral and having bends which define a zigzag structure, enabling a significant radial expansion with a low shortening of the length of the stent.
The fault of these stents is that they have a weak shoring up strength at the ends and poor covering power at the ends.
Furthermore, it is also known from U.S. Pat. No. 4,553,545, of various embodiments of a stent which is formed by a filamentary element coiled in a spiral. With reference to
FIG. 10
of this patent, a risk is presented of shifting or of crushing or of unwinding of the stent during a radial expansion, and this is also explained in column
7
, lines
56
et seq. In order to remedy this, this patent proposes rigidifying the turns by a rigidifying element, see
FIGS. 11
to
16
. A stent of ladder construction is then proposed in
FIGS. 22 and 23
, and notably with reference to
FIG. 23
, a stent is formed by a double helix spiral which is joined by transversal elements
82
. It is indicated that this structure enables improving the stability during a radial expansion (column
12
, lines
45
to
66
).
The fault of these stents is that they have a weak shoring up strength at the ends and poor covering power at the ends.
Further, if an obstacle is encountered during the insertion of the stent forming device, due to the absence of hold of the spiral at the ends, a subsidence of the spiral can be produced in some cases.
It is further known from the document WO-A-96/03092, of a stent forming device which is constituted by a filamentary element coiled in a ring-like fashion, which is constituted of a certain number of rings joined together by bent binding elements
22
, the ring-like portions being also bent so as to form a zigzag structure. This device has a good shoring up strength during a radial expansion. This device has a certain flexibility by virtue of the presence of joints
22
comprising bends
20
, between the ring-like elements
11
, but this flexibility is essentially lost after expansion and gives rise to constraints on the canals, and in particular the arteries. It will be observed that the structure described in this document provides, after unfolding, a network or cellular system, as is clearly represented in
FIG. 4
, which favors the shoring up, but limits the flexibility and the shapability to the canal, and this constitutes a significant requirement.
The current limits of these known stent forming devices remain:
a) the rigidity of certain stents, which can compromise an access to certain lesions, the upstream of which is winding. This rigidity becomes a drawback insofar as stent forming devices of longer length are more and more sought after, at the same time as the stent forming devices being capable of making winding accesses and for which a greater flexibility is sought. The stent forming device described in the document WO-A-96/03092 has a flexibility which is improved with respect to the prior art devices, but which is still judged to be insufficient, notably in the case of long lengths, i.e. beyond 20 mm, which is the current tendency.
b) the constraints given rise to on the artery upstream and downstream from the stent resulting from a drawing out phenomenon by rigidification of the canal after unfolding of the stent. This can give rise to complications during the intervention of tissue reactions leading to a recurrent narrowing of the canal mentioned above. This leads to an insufficient shapability to the canal, and notably to the ends, giving rise to constraints which are not very satisfactory to said ends, and this in particular is the case in the document WO-A-96/03092.
c) the difficulty of getting over the stent when it is implanted straddling over a bifurcation and that the branch must be treated as well. In particular, it may be necessary to pass a balloon or a stent on balloon through the structure of the first stent. This also is in particular the case in the document WO-A-96/03092.
d) Certain stents lack radial strength, called shoring up strength, in particular at the ends, and this can be important for shoring up the origin (ostium) of a canal such as an artery, which is in general very elastic. This is in particular the case of stent forming devices described in the documents U.S. Pat. No. 5,578,149, U.S. Pat. No. 5,591,230, and U.S. Pat. No. 4,553,545. The shoring up strength of the whole of the stent is also very important when lesions exert a strong resistance to the dilatation, as is the case of calcified lesions or lesions having strong elastic recoil.
e) Certain filamentary type stents deform longitudinally during a blockage of the progression during the access to a lesion due to a lack of hold of the structure. This is in particular the case of the stent forming devices described in the documents U.S. Pat. No. 5,578,149, U.S. Pat. No. 5,591,230, and U.S. Pat. No. 4,553,545.
Thus, in the known prior art devices, these are of a design which is either entirely spiral, or entirely ring-like. Further, for certain ring-like type stents, these can be produced in a network, as in the case of the document WO 96/03092.
Thus, the main aim of the present invention is to solve the novel technical problem consisting of providing a solution, which consists of a novel stent forming device, which has simultaneously the following properties:
a) a very good flexibility,
b) a lateral crossing capacity from the inside of the stent by another stent or a balloon device,
c) a very good shapability in the longitudinal sense, so as not to modify the curvature of the canal in which the stent must be implanted, in the longitudinal sense,
d) a very good radial strength so as to completely fill its role of shoring up the canal in which the stent must be implanted,
e) a very good crossing capacity enabling a longitudinal passage by another device such as a balloon or another stent, optionally also on a balloon,
f) a very good capacity to keep in place in unfolded position,
g) a very good capacity of shoring up and of ring-like covering of the ends enabling a complete covering without overrunning, which is particularly important notably in the medical field at the level of ostia.
h) an expansion essentially without shortening of the length of the stent, and this even for stents of long lengths, namely greater than about 20 mm.
Thus, a further main aim of the invention is to provide a solution to the novel technical problem above, according to a particularly simple design which is relatively inexpensive and which can be used on an industrial and medical scale.
Thus, according to a first aspect, the present invention provides a stent forming device comprising a first filamentary element coiled spirally at least in its central portion, and a proximal end portion and a distal end portion, characterized in that it comprises a second filamentary element coiled spirally at least in its central portion, said first and second elements thus defining a double helix structure, and in that at least one, preferably both, end portion(s) is (are) produced with at least one said filamentary element coiled in substantially ring-like fashion. This device enables thus reinforcing notably the maintenance of the structure in place as well as ensuring a complete covering without running over, particularly at the level of the ostium.
According to an advantageous embodiment of the invention, the device comprises end portions defining respectively a proximal end edge and a distal end edge of the device, said end portions being produced with said first and second filamentary elements coiled in s
Ascher Gilles
Chevalier Bernard
Glatt Bernard
Guyon Philippe
LeCointe Bruno
Dennison Schultz Dougherty & MacDonald
Pellegrino Brian E.
Snow Bruce
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