Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2000-01-14
2001-04-10
Yasko, John D. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
Reexamination Certificate
active
06213989
ABSTRACT:
BACKGROUND OF THE INVENTION
Hypodermic cannulas are manufactured by the millions for the many medical uses including blood and solution administration and collection, blood sample taking, and fistula needles for taking and returning blood for processing in a hemodialyzer or the like.
It is known that the best needles from the viewpoint of patient acceptance are the sharpest needles. However, the manufactureability of the needle is also an important factor since commercially successful needles will be manufactured by the millions. Also, such needles must be manufactured with great uniformity from unit to unit, and desirably are highly inexpensive in their manufacturing process.
The expired De Luca U.S. Pat. No. 3,308,822 shows a hypodermic needle having a sharp tip which is formed by five separate cuts of a shaping tool. Such a needle may exhibit certain desirable characteristics of sharpness, but the five separate cuts represent an undue level of complexity in the manufacturing process. Also, the cutting edge extending from the point extends to the outer wall of the cannula.
However, in needles providing vascular access, sharpness can be a problem. In this situation the point of the cannula must rest within the walls of a vessel, but the angle of the point is downward as the needle has been inserted through the skin at an angle. If the cannula is pushed downward, the sharpened point may touch the inside lumen of the vessel. If it pierces the lumen of the vessel a hematoma will result.
Tersteegen et al. U.S. Pat. No. 4,368,738 teaches a bent point cannula to try to avoid this problem. A well-known three bevel sharpened cannula is formed, and then the tip of the cannula is bent upwards much like a ski tip. If the cannula is pushed downward, it is likely that only the underside of the bent-portion will touch the lumen but not damage it.
There are many other problems with this approach. Not only is it very costly to bend a point, but the point can be easily damaged if this operation isn't performed precisely. Also, the bent point requires the cannula be inserted through the skin with the bevel in an abnormal “upside-down” position. Only after the point and bevel is completely within the vessel is the bevel turned “right-side up”. In clinical practice, this has shown to be more dangerous than the problem it sought to avoid.
Zimmermann U.S. Pat. No. 5,290,267 and Hickey U.S. Pat. No. 2,697,438 also show similar bent points.
By this invention, a cannula or needle is provided having a simplified manufacturing process, which exhibits extreme incision sharpness for maximized patient comfort, but also protection from hematomas, by means of the point and all forward cutting edges are spaced inwardly from the cannula outer wall.
DESCRIPTION OF THE INVENTION
By this invention, a tissue-penetrating cannula is provided which comprises a tube having a sharp end formed by a first cut surface defining an acute angle, typically about 10° to 30°, to the longitudinal axis of the tube. This first cut surface forms a generally oval tube edge which of course defines a similar acute angle to the longitudinal axis of the tube. The tube is typically made of stainless steel.
A second, cut surface is defined along a right-hand forward portion of the oval tube edge, along with a third, cut surface which is defined along a left-hand forward edge of the oval tube edge. The second and third cut surfaces define between them a forward cutting surface in the tube edge (where a curved surface would have been after the first, flat cut surface was formed, prior to forming the second and third surface).
A fourth, cut surface is provided at the above forwardmost point, the fourth, cut surface intersecting the second and third cut surfaces, causing the forward cutting surface to be radially spaced within the outer wall of said tube. Typically the forward cutting surface is thus formed as substantially a nonlinear point. Without the fourth cut, the forward cutting surface would define a line extending transversely between the inner and outer surfaces of the tube wall.
Preferably, the fourth cut surface is positioned on an outer surface of the tube, being substantially spaced by the wall of the tube from the first, second and third cut surfaces to comprise an outer, undercut bevel.
It is also preferred for the fourth cut surface to define an acute angle of opposite sense to the acute angle of the first cut surface. The planes of the acute angles defined by the first and fourth cut surfaces to the longitudinal axis of the tube are preferably substantially parallel. In other words, if the first and fourth cut surfaces were rotated in the direction of their angles, to become parallel to the longitudinal axis, they would be parallel to each other.
Preferably, the cannula of this invention may be manufactured by cutting a first flat surface at an acute angle to the longitudinal axis tube to form the generally oval tube edge described above. The second cut surface is then formed along the right-hand forward portion of the oval tube edge, while the third, cut surface is formed along the left-hand forward portion of the oval tube edge. This, in turn, forms between the second and third cut surfaces a forwardmost point defining an edge line through the thickness of the wall of the cannula. The second and third cut surfaces are typically in a position that is rotated respectively clockwise and counterclockwise relative to the tube axis by about 10 or 15 to 40 degrees.
Finally, the fourth flat, cut surface is formed at the point or front edge line, intersecting the second and third cut surfaces to reduce the edge line to a substantially non linear point.
Thus, by four machining cuts, a sharp needle point can be formed in accordance with this invention. With computer-directed machining, these cuts may be made in any order.
Alternatively, a six cut embodiment is also shown below.
REFERENCES:
patent: 2187259 (1940-01-01), Barnhart
patent: 2697438 (1954-12-01), Hickey
patent: 3289675 (1966-12-01), Dunmire et al.
patent: 3308822 (1967-03-01), De Luca
patent: 4368738 (1983-01-01), Tersteegan et al.
patent: 4490139 (1984-12-01), Huizenga et al.
patent: 4561445 (1985-12-01), Berke et al.
patent: 4586926 (1986-05-01), Osborne
patent: 4689040 (1987-08-01), Thompson
patent: 4826492 (1989-05-01), Magasi
patent: 5290267 (1994-03-01), Zimmermann
patent: 5405354 (1995-04-01), Sarrett
patent: 5484422 (1996-01-01), Sloane, Jr. et al.
patent: 5536259 (1996-07-01), Utterberg
patent: 5575780 (1996-11-01), Saito
patent: 0 739 639 A1 (1996-10-01), None
patent: 0 739 640 A1 (1996-10-01), None
patent: WO 92/04062 (1992-03-01), None
Communication from European Patent Office dated Nov. 5, 1997 including Abstract 96304586.9, European Search Report EP 96 30 4586 and Annex to the European Search Report—4 pages total.
DSU Medical Corporation
Ellis Garrettson
Shaw Seyfarth
Yasko John D.
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