Medical scalpel

Details Medical scalpel Medical scalpel

2001-02-28

2003-04-29

Hale, Gloria M. (Department: 3765)

Surgery

Instruments

Means for removing, inserting or aiding in the removal or...

C606S167000, C606S166000

Reexamination Certificate

active

06554840

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a medical scalpel for incising spherical biological tissues, and in particular to a medical scalpel capable of producing a highly auto-closable incisional vulnus in eyeball incision.
BACKGROUND ART
In the conventional ophthalmic surgery, incision of cornea or interstice of cornea and sclera inevitably requires successive suture or ligation of incised cornea or sclera. A suture may, however, pressurize the cornea or sclera, which tends to retard recovery of eyesight or to produce postoperative astigmatism. So that recent trends in the surgery relate to production of auto-closable incisional vulnus which automatically closes without needing suture.
A preferable and highly auto-closable incisional vulnus will be explained referring to
FIGS. 5A and 5B
, and
FIGS. 6A
to
6
C. As shown in
FIG. 5A
, when a cornea
52
is incised with a scalpel
51
in a direction oblique to the thickness thereof to produce an incisional vulnus
53
(this is generally done, in a front view of an eyeball, by piercing the scalpel
51
in a direction from lower to obliquely upper), intraocular pressure will be exerted to pressure-open the cornea
52
(in a direction energizing the cornea
52
along an arrow “a”), to thereby close the incisional vulnus
53
by pressure contact.
While a morphology of such preferable, highly auto-closable incisional vulnus will differ whether it is viewed from a direction of the scalpel insertion or front of the eyeball since the eyeball has a spherical surface, a front view of the eyeball shows an external incisional line
53
a
formed on the external of the cornea
52
, which is given as a straight line as shown in
FIG. 6A
, or as curved lines bulging toward an internal incisional line
53
b
as shown in
FIGS. 6B and 6C
.
The scalpel
51
used for incising the eyeball will now be described referring to the drawings. The scalpel
51
shown in
FIG. 7A
has a sharp pointed end
51
a
and peripheral cutting edges
51
b,
and that shown in
FIG. 7B
has a cutting edge
51
b
rounded along the entire periphery rather than having a pointed end. Sectional forms of such scalpel
51
being generally employed include a trapezoid having a virtual line connecting the cutting edge
51
b
as a base as shown in
FIG. 7C
(bevel-up type), and flattened hexagon having a line connecting the cutting edge
51
b
approximately at the center of the total thickness of the blade portion as shown in
FIG. 7D
(bi-bevel type).
In eyeball incision, the scalpel
51
is opposed to the cornea
52
so as to allow formation of the auto-closable incisional vulnus
53
, and is forwarded straight along a direction indicated by arrow “b” in FIG.
5
A. The scalpel
51
is then moved rightward or leftward according to a purpose of the surgery, to widen the incisional vulnus
53
.
It is known that such preferable, highly auto-closable incisional vulnus has the external incisional line which gently curves as bulging toward the center of the eyeball or runs straight when viewed from the front of the eyeball. On the contrary, a less auto-closable incisional vulnus is known to have the external incisional line which gently curves as bulging away from the center of the eyeball when viewed from the front of the eyeball, and is likely to turn over when pressure is exerted on the cornea to thereby undesirably incorporate foreign matters or bacteria contained in lacrimal fluid into the eye, so that such vulnus needs suture to enhance auto-closable property. It has, however, been difficult to produce a preferable, highly auto-closable incision vulnus using a generally known scalpel.
More specifically, a bevel-up scalpel
51
shown in
FIG. 8
causes on both planes of the blade portion thereof different amounts of force due to pressure p ascribable to the ocular tension and incision resistance when pierced into the cornea
52
(that is, downward force F
d
exerted on the upper plane comprising an upper plane and a slant plane is larger than upward force F
u
exerted on the base plane), so that the entire portion of the scalpel
51
will shift toward the base plane as it advances deeper into the eye. So that an incisional vulnus thus produced will have a reversed V-form when viewed from the direction of the scalpel insertion, which comprises a tip portion corresponding to the pointed end
51
a
and straight portions extending from such tip portion toward the ends. Such incisional vulnus will, however, have the tip portion and curves extending from the such tip portion when viewed from the front of the eyeball. Such tip portion is likely to dislocate and may cause astigmatism after the auto-closure.
The bi-bevel scalpel causes on both sides of the blade portion thereof balanced forces ascribable to the ocular tension and incision resistance, so that no vertical force enough for dislocating the scalpel will be generated The incisional vulnus thus produced will have a straight profile as viewed from the direction of the scalpel insertion, but will have an external incisional line bulging away from the center of the eyeball, which makes the incisional vulnus less auto-closable.
It is therefore an object of the present invention to provide a medical scalpel capable of producing a preferable, auto-closable incisional vulnus.
SUMMARY OF THE INVENTION
A medical scalpel of the present invention is such that for incising a spherical biological tissue which comprises a shank, and a planar blade portion being associated to said shank and having a first face and a second face one of which is formed flat at least wherein said blade portion having an edge in parallel as a whole with said flat first face or said second face, and being formed so as to have a ratio of the partial thickness thereof on one side of a virtual flat plane surrounded by said edge to the total thickness thereof which resides within a range from 75 to 93%.
Such medical scalpel (simply referred to as scalpel, hereinafter) has along the outer periphery of the blade portion at least two slopes composing both sides thereof, and the partial thickness of such blade portion on one side (the upper side, for example) of a virtual flat plane surrounded by such edge accounts for 75 to 93% of the total thickness of the blade portion. Such setting allows the force exerted on the upper side of the edge, that is the force pushing the scalpel downward, to become larger than the upward force exerted on the lower side.
Difference between the downward force and upward force is, however, smaller than that in the conventional bevel-up scalpel by virtue of cancellation therebetween, so that a slight downward dislocation of the scalpel will occur when the scalpel is pierced into the eyeball, to thereby produce the external incisional line gently bulging toward the center of the eyeball or extending straightly when viewed from the front of the eyeball. Hence, the external incisional line can have a profile equivalent to that illustrated in
FIG. 6C
, to thereby produce a preferable, highly auto-closable incisional vulnus.
The force exerted on the blade portion along the direction from the upper face side to the lower face side when the edge is pierced into the eyeball can properly be adjusted by selecting the upper partial thickness within a range from 75 to 93% of the total thickness, which defines the travel distance of such blade portion from the upper face side to the lower face side. Thus the shape of the incisional vulnus can readily be selected depending on such travel distance, to thereby form a desired incisional vulnus with an excellent auto-closable property.


REFERENCES:
patent: 5201747 (1993-04-01), Mastel
patent: 5217476 (1993-06-01), Wishinsky
patent: 5222967 (1993-06-01), Casebeer et al.
patent: 5405355 (1995-04-01), Peyman et al.
patent: 5713915 (1998-02-01), Van Heugten et al.
patent: D405178 (1999-02-01), Dykes
patent: 6056764 (2000-05-01), Smith
patent: 6099543 (2000-08-01), Smith
patent: 6139559 (2000-10-01), Nordan et al.
patent: RE37304 (2001-07-01), Van Heugten et al.
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